processdesign - User contributions [en]

Mixer and Splitter

2015-03-06T05:15:58Z

Jian:

Author: Nicklaus Dotzenrod [2015] 

Stewards: Jian Gong and Fengqi You
 

== Introduction ==
The production of products from chemical processing plants usually involve a variety of mechanical equipment. Distillation columns, reactors, heaters and condensers are some of the most prominent pieces of equipment utilized at production facilities. Mixers and splitters, however, are equally important and play crucial roles in many different types of processes.
== Mixers ==
Mixers play an important role in many different production processes, at the beginning or at the end. Some processes require several feed streams to be properly mixed before a reaction is commenced in a reactor. Other processes require that final products are blended together. Mixers serve to achieve both of these roles. Materials in all physical states are capable of being mixed together, whether it is gas mixing, liquid mixing, gas-liquid mixing or solid-liquid mixing.
=== Gas Mixing ===
In certain processes, gas to gas mixing is necessary to produce a desire product. This type of mixing is rare, however, as gases have low viscosity making them easy to mix on there own, without the assistance of a mechanical mixer. An example of gas mixing would be the mixing of oxygen, along with other gases to dilute the oxygen to desired compositions. Usually, a long pipe that contains turbulent airflow is sufficient enough to mix gases (Towler and Sinnot, 2012).[[File:gasmixer.jpg|thumb|center|'''Figure 1''' Standard 2-Gas Mixer|150x150px]]

=== Liquid Mixing ===
Processes that require the mixing of two liquids are very common in many industries. Several factors should be considered when determining the type of mixer needed including the degree of mixing required, if the process is a batch or continuous operation and the properties of the liquids being mixed. There are several methods by which liquid to liquid mixing can be achieved (Towler and Sinnot, 2012).
1.'''Inline Mixing''' Inline mixers are static devices that provide a turbulent [[File:108.jpg|thumb|right|none|'''Figure 2''' Inline Mixing Diagram|150x150px]] environment that promote the mixing of liquids. They are generally inexpensive and can be used to mix both laminar and turbulent flows. There are several types of inline mixers.

::*'''Tee Mixer''' Allows for two lower viscosity fluids to meet at an intersection where they are able to meet and exit the "tee" together.
::*'''Injection Mixer''' Fluid is introduced into a stream of another fluid with a concentric pipe injector, allowing for mixing to occur via turbulent diffusion.
::*'''Annual Injection Mixer''' Very similar to the injection mixer except fluid is introduced into another stream of fluid with an annular array of jets instead of a single concentric pipe.

2.'''Stirred Tanks''' Stirred tanks are mixing vessels equipped with an agitation device to promote the mixing of liquids. These mixers are quite often used for mixing viscous liquids. There are several types of agitators sued for stirred tanks including turbine impellers, pitched bladed turbine, paddle, anchor and helical ribbon. [[File:stirredtank.png|thumb|right|baseline|'''Figure 3''' Stirred Tank Diagram|150x150px]]

3.'''Side-entering Agitators''' Side-entering agitators are useful for mixing lower viscosity fluids in larger tanks as these sort of tanks are not very compatible for top supported agitators. [[File:side.jpg|thumb|center|none|right|'''Figure 4''' Side-Entering Agitator Diagram|150x150px]]

=== Gas-Liquid Mixing ===
There are several different types of mechanical mixers used to achieve a homogeneous gas-liquid mixture. Some include inline mixers, stirred vessels and other static mixers. A special device called a ''sparger'' can be used for this type of mixing as well. A sparger is essentially an injection tube with multiple holes in it to disperse gas within a tube filled with a liquid (Towler and Sinnot, 2012). [[File:sparger.jpg|thumb|center|'''Figure 5''' Diagram of a Sparger|250x250px]]

=== Solid-Liquid Mixing ===
There are times when a process requires a solid to mixed with a liquid. Generally, this is due to the fact the solids are insoluble and need to be transported as a slurry. Often times, stirred tanks are used to mix these physical states. Additionally, a screw conveyor can be used. Typically, this sort of combination is mixed at atmospheric pressure with the completed mixture later being pumped at the process pressure (Towler and Sinnot, 2012).[[File:screw.gif|thumb|center|'''Figure 6''' Screw Conveyor Animation|250x250px]]

== Aspen HYSYS Version 8.0 Simulation for Mixers==
Aspen HYSYS software is an easy to use process modeling software that allows users to design efficient systems for industrial applications. HYSYS is capable of simulating many types of equipment that most industrial processes would require, including mixers. Unfortunately, HYSYS is only able to model a generic mixer, and is not able to model a specific model. The mixer used in HSYSY simulates and ideal mixing environment (Aspen HYSYS, 2014).
===Preparing Simulation Environment===
Before a mixer can be simulated, the HYSYS simulation environment must be prepared. The first step is to pick a ''fluid package''. The package chosen is based on the materials being used and the overall process being simulated. The next step is to choose components. These also, depend on what type of process is being modeled.
===Creating Input Streams===
After a fluid package and components have been chosen, steams can be entered into the simulation environment. For the example shown in Figure 7., only two input steams are used.
[[File:material.jpg|thumb|none|'''Figure 7''' Creating Input Streams|800x800px]]

===Specify Input Streams===
After creating the input steams, they must be specified.
#Click the '''Home''' tab at the top of the screen.
#Click the '''Workbook''' tab at the top of the screen.
#Specify all known conditions of the input streams.
[[File:material2.jpg|thumb|none|'''Figure 8''' Specify Input Streams|800x800px]]

===Set Compositions of Streams===
Set the compositions of the input streams by clicking on the '''Compositions''' tab located at the bottom of the '''Workbook'''. In the example shown in Figure 9, one stream is pure ethanol and one is pure water.
[[File:material3.jpg|thumb|none|'''Figure 9''' Set Compositions of Streams|800x800px]]

===Insert Mixer===
To add a mixer to the simulation environment, look at the '''Palette''' tool box and find the '''Mixer''' component icon (illustrated in Figure 10). Now, the mixer can be placed onto the simulation environment, ideally near the two input streams already placed.
[[File:material4.jpg|thumb|none|'''Figure 10''' Insert Mixer|800x800px]]

===Connecting Mixer===
Now that the mixer is placed into the simulation environment, it must be connect to input and output streams in order to function. Figure 11 illustrates the necessary steps.
#Click the '''Flowsheet/Modify''' tab at the top of the screen.
#Choose the '''Attach''' (paper clip) icon
#Click and drag the two input streams and connect them to the mixer
#Click the output side of the mixer and drag out an output stream
[[File:material5.jpg|thumb|none|'''Figure 11''' Connecting Mixer|800x800px]]

===Finalize Output Stream===
Once all the input and output streams have been connected to the mixer, go back to the '''Home''' tab and click the '''workbook''' icon as illustrated in Figure 12. The output stream should be specified and should be well mixed representation of streams 1 and stream 2.
[[File:material6.jpg|thumb|none|'''Figure 12''' Finalize Output Stream|800x800px]]

== Conclusion ==
HYSYS does not offer a very comprehensive means of simulating a mixing process, however, it is able to estimate the result of multiple material streams being mixed. The results of a mixing simulation in HYSYS should not be the sole simulation used when designing a process that includes mixing, but it will assist in determining general process dynamics.
==References==
1. G.P. Towler, R. Sinnott, Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design, Elsevier, 2012.

2. Aspen HYSYS. Vers. 8. Bedford: AspenTech, 2014. Computer software.

Preliminary market analysis and plant capacity

2015-03-02T04:23:48Z

Jian: /* References */

Authors: Sean Cabaniss, David Park, Maxim Slivinsky and Julianne Wagoner (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Feb. 2, 2014

 

==Introduction==

In forming the design basis it is necessary to determine the opportunity to satisfy a societal need, and assess this based on market analysis which includes current production, projected market demand, and current and projected selling prices (Seider et al., 2004). The market analysis provides economic data which will determine which process alternatives to choose from as well as equipment capacities. This process will help narrow the scope of a project, and establish guidelines for sizing design elements across the project. The market analysis and subsequent plant sizing estimations are the natural first steps in process design, and are incredibly important factors in shaping the future work of process designers down the line. No design project should proceed to the final stages before the overall economic feasibility is considered. A preliminary market analysis is the first step in determining whether a plant will be profitable (Peters and Timmerhaus, 2003).

[[File:Design_basis_plant_size.PNG]]

Figure 1. Early market analysis, shown here by the yellow boxes, will affect many elements of later design work, so it is important to produce a detailed report before taking further design steps (Towler and Sinnott, 2013).

==Market Analysis==

The first step when considering the development of a new product or process is to examine the existing market scenario. It is important to take a survey of current market situations in order to understand whether or not your product or process will be an economically successful venture.

Economic data are difficult to estimate due to inherent volatility in the marketplace (Seider et al., 2004); most companies use market studies to project future market size and prices. A risk analysis is performed using a range of chemical prices to determine the sensitivity of the project economics to specific prices. A commonly used source of national economic price data is the Chemical Marketing Reporter, which is updated biweekly (Seider et al., 2004). For more detailed estimates, e.g. for a specific region, the chemical manufacturer should be contacted. The supply and demand for feeds and products must be considered. This will, clearly, impact the price of these items. Consider the forecast for the supply and demand for these streams as well. Are there any niche markets that are underserved? Is there any technology on the horizon that could impact supply/demand levels? Additionally, are there any competitors running the same process? This could impact the company’s profitability, as your process must be unique enough to justify competition with existing organizations.

The scope of a project can also be limited by budget. Engineers must consider the budget they have to work with and various strategies for financing, including issuing more stock, selling bonds, and/or simply borrowing the funds (Biegler et al., 1997).

==Plant Sizing and Decision Making==

The scale (e.g. flow rates, equipment capacities) of the process is determined based on projected demand for the product (Seider et al., 2004), which was determined in earlier market analyses. From this basic starting point, it becomes necessary to consider a variety of plant alternatives; it is sometimes advantageous to design beyond the requirement, as the market for chemical products will likely fluctuate over the lifetime of the plant, with both positive and negative swings for the company. These early decisions will dramatically affect the operation of the process for years to come. When considering the various attributes of a process, the overall company goals should be the guiding factor for design teams.
===Sizing===

After considering the results of the market analysis, it should be known how much of your desired feeds and inputs are readily available in the region your plant is being built. This amount, which we will define as "F", can be either a flow rate or a definite amount, depending on whether your operation is a continuous or batch operation. Depending on the process chosen, there will be calculated overall conversion of the incoming materials, which we will define as "x". From a simple calculation:

<math>x*F = Y</math>

Where Y will be an initial estimate for the size of your plant. Depending on the confidence in the calculated yield rate, it may be necessary to slightly tweak Y. If there is low confidence in the value of "x", Y should be decreased to match, while if there is high confidence in the value of "x", no changes to Y will be necessary (Seider et al., 2004).

"F" is a variable largely dependent on your market analysis. The depth and scope of your market analysis will allow for a much more precise estimate for "F", which will allow for much more confident decision making when determining the size of your plant.

Market analysis can also work in the reverse order by responding to a known demand and converting it to an hourly production rate as shown below:

<math>MD = HP * 24hr/day * OD</math>

<math>OD = OF * 365 days/yr</math>

Where MD is market demand, HP is hourly production, OD is the number of days/year plant is in actively producing material, and Operating Factor (OF) is the capacity the plant will run at (usually between .8 and .9). Both calculations are viable ways to estimate plant capacity, and the choice of calculation is dependent on how market analysis research was conducted (Seider et al., 2004).

The final sizing concern comes from considering the usage of process byproducts. In the following sections, details concerning side products will be discussed in more detail, but it is always necessary to know what will happen with any byproducts produced by your process, whether they are hazardous or beneficial. Hazardous materials may required additional processing, and those byproducts which may be used for other processes in the company may be shipped to other plants, or could be processed on site if the size is available and additional investment may be beneficial.

[[File:Byproduct analysis.PNG]]

Figure 2. A simple flowsheet which describes the decision making process when determining potential uses of process byproducts. These byproducts may result in an expansion of the plant size, since additional processing may be economically beneficial for the company (Peters and Timmerhaus, 2003).

===Technology Alternatives===

Consider whether adding on to an existing plant, building at a new location, or tearing down an old plant and starting fresh will be the best move for the company. Could the new process piggy-back off technology the company is already running? The team must decide whether to use in-house chemistry; a common, well proven process; or a new, unconventional solution (Biegler et al., 1997). Consulting any in-house experts should be the first step for a design team. Engineers, operators, and/or researchers with hands-on knowledge of the process can help to create an understanding of the problem and propose alternatives for improving the process (Biegler et al., 1997). Sources of information on processes less familiar to the company include: patent literature, journal articles, encyclopedias of technology, handbooks, textbooks, external corporate files, and consultants. Businesses can also join organizations that carry out studies of their member companies (Biegler et al., 1997). The company will need to pay royalties for the use of any patented chemistry that was not developed in-house. They must also consider environmental concerns and ensure that each process alternative satisfies the large number of environmental regulations.

===Safety Considerations===

Each process alternative should be considered from a safety standpoint. The team should attempt to determine whether any reasonable combination of events could lead to an unsafe situation: fire, explosion, or release of toxic chemicals. If any process is particularly hazardous to operate (for example, it requires the use of a noxious gas), this aspect should be heavily weighted in the decision-making process. This can often lead to situations where additional processing of hazardous materials must be required before removal from the plant site, which can dramatically increase costs. Processing hazardous side products will increase feed material requirements, plant space requirements, and utility costs, leading to higher capital investment for the additional equipment and higher operating costs than may have been initially estimated.

Fine-tuned electronic control of potentially dangerous processes will often be required to ensure operator safety and prevent explosions or leaks. The level of detail required in electronic control will also lead to rapidly rising costs, as more controllers required more servers, electrical wiring, and climate-controlled buildings in order for complex systems to operate. As seen in the "Incident at Morales" film, cutting costs at the control level can have fatal results, so designers must be careful to ensure that every dangerous outcome is properly controlled, no matter the costs associated with such an expansion.

===Utility Concerns===

Rising utility costs will have an enormous impact on the financial viability of a process design. The cost of powering a larger plant can rise exponentially as the size of the plant increases, sometimes without a significant rise in revenues. Optimizing this balance is important when considering the sizing of an operation. Estimates of utility prices, such as electricity, cooling water, and steam, can be found tabulated in reference texts (Seider et al., 2004). For more accurate estimates local utility companies should be contacted.

===Next Steps===

Once a process has been chosen, the design team generates and evaluates a conceptual flowsheet. The team considers various alternative designs and strategies to come up with the more detailed process flow diagram. The plant can then be modeled using simulation software. With each new level of detail considered, the team should be mindful of the needed investment and the expected return (Biegler et al., 1997).

==Examples==

Example 1:

Primitive Design Problem:
"An opportunity has arisen to satisfy a new demand for vinyl chloride monomer, on the order of 800 million pounds per year, in a petrochemical complex on the Gulf Coast, given that an existing plant owned by the company produces 1 billion pounds per year of this commodity chemical. Because vinyl chloride monomer is an extremely toxic substance, it is recommended that all new facilities be designed carefully to satisfy governmental health and safety regulations."

The scale of this process is determined by the primitive design problem to be 100,000 lb/hr, which is approximately 800 million pounds per year assuming 330 operating days per year, giving an operating factor of 0.904 (Seider et al., 2004).

Example 2:

Fictional Design Project:
ChemEng, a small chemical firm, is interested in investing in technology to convert glycerol to propylene glycol. The company has tasked a design team with conducting a preliminary market analysis and suggesting a capacity for the proposed plant.

The following facts are important aspects of a basic market analysis. They should be researched by the design team and reported to the managers of ChemEng.
* The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $500/ton.
* The supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum.
* The production grades of glycerol are crude (40-88% purity), technical grade (98% purity), and USP (United States Pharmaceutical) grade.
* Propylene glycol is relatively expensive at around $1500/ton.
* Supply of propylene glycol struggles to keep up with an increasing global demand currently at 1.8m tons.
* The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity)
* There are two plants running similar technology with a capacity of 100,000-tons currently in operation by Archer Daniels Midland and Oleon. There is also a 200,000-ton Global Bio-chemical Technology Group facility.

Based on the market analysis, a plant capacity of 180,000 tons would be reasonable. This would be 10% of the global propylene glycol market and is in line with similar plants in operation.

==Conclusion==

Market analysis provides an important stepping-off point when beginning the design of a chemical process. Preliminary economic estimates will influence decisions concerning the sizing of your operation, which will have long-term effects on the profitability and viability of a chemical product, so it is important to pay close attention to the results of these early analyses.

==References==

Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Site condition and design

2015-03-02T04:23:30Z

Jian: /* References */

Authors: Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: 1/17/2014

 

== Introduction ==
One of the first and most important decisions when designing a chemical plant is plant location. If a new plant is being built, a suitable site must be found and a plant layout considered. However, if the chemical plant is being built on the site of an old plant (possible upgrade or expansion) the existing site’s infrastructure must be considered. Of incredible importance are local laws and ordinances concerning chemical disposal, safety of the local population, and considerations for the employed operators.

Suitable locations for chemical plants often have several plants in close proximity. The existence of these locations is often beneficial as there are often living infrastructure nearby to support the labor. Figure 1 shows the distribution of labor across the US and implicitly the common locations of many chemical plants.

[[File:Map of ChE.png]]

Above is shown the occupational employment density of chemical engineers separated county. It is noticeable that the coastal areas of the United States are most attractive for chemical process industries due, no doubt, to the easy access to water transportation routes, which are cheaper and faster than land transportation. Building a process plant in any of the “240-3,740” density shaded regions would capture the additional benefit of having the process plant built in an area where supporting industries already thrive, therefore making repairs and operational costs as a whole as low as possible as determined by location. The states of greatest chemical process plant density are California, Arizona, Texas, Louisiana, Mississippi, Illinois, Michigan, Indiana, Ohio, and the majority of the east coast states. The local corporate tax rates of these locations are highly dependent on income bracket as per the information found at http://www.taxadmin.org/fta/rate/corp_inc.pdf

== Geographical selection ==
The location surrounding a chemical plant can substantially influence its construction costs and operating costs, and may affect long-term profitability. Thus it is important to choose an appropriate location for every facility.

=== Factors considered ===
==== Natural resources ====
Transporting materials to and from the plant is a huge operational cost that is heavily factored into when selecting a plant location. Therefore, choosing to build a plant near natural resources reduce the operational cost of the plant tremendously. Natural resources such as river, lake, sea, and oil well near operating plants can be a huge bonanza for them.

Major chemical plants processes need cooling system, which require immense amount of water. If river, lake, or sea is in close proximity, plants can utilize the water readily and relatively cheap. Plant needing of a great energy may build a dam on a river to resolve power issue. Upstream oil sectors look for oil wells to operate and drill out the oil and gas. Companies find themselves saving or making money when they build a plant near natural resources which they can take advantage.

==== Weather ====
Climate condition is an important factor when considering a plant to be built. Adverse weather conditions affect the longevity of the equipment directly. Often times, special adjustments have to be made to the plant equipment to negate the harmful climatic effect, which then increase the capital and operating cost of the plant.

Sufficiently high temperature or humidity variation may necessitate cooling or heating systems to control the ambient temperature of the plant processes. Pipes used in severely low temperature require special insulation or heating to prevent them from freezing. In a site where flooding is possible, plant should be designed in a way to minimize or prevent from flood damage. Also, plant structures have to be built stronger to withstand more force in the site where high winds and earthquakes frequently occur. Utility cost will also vary depending on the ambient temperature and humidity.

==== Proximity to related chemical operations ====
The availability and price of raw materials for feed streams often play a large part in determining the plant location. For example, many ethylene plants are built in the Middle East near supplies of natural gas.

If building a plant near raw materials is not possible, often the next determining factor is ease of transportation. For most chemicals, proximity to major road, rail, waterway, or ports are desired. For high-value products such as pharmaceuticals, proximity to air ports can be used to prevent degradation of product during transport. Ease of transportation results in cheaper logistics cost for transport between both suppliers and buyers.

Proximity to utilities are important in chemical process. Water is ubiquitous in chemical plants and are often require in substantial amounts. Construction of plants near rivers and lakes are often desired to reduce the cost of process water. If drawing from local water is not possible, cooling towers will need to be used. Electrical power is required in all plants, often requiring plants to be built on available power grids.

==== Laws and regulations ====
Federal laws will be listed as it serves as a baseline for the entire country. State and local laws sometimes are stricter than the established federal laws resulting. Property costs, property taxes, corporate income taxes, and fines also vary between states. Therefore, further consultation of the state and local laws must also be done beyond the laws listed in this text to ensure adherence to all laws required for the location of the plant. Below are several hallmark federal laws which proper treatment and disposal of waste in the air, ground, and water (Towler and Sinnott, 2013).

===== The Clean Air Act =====

The Clean Air Act (CAA) was first passed in 1970 and was amended in 1990. The CAA empowers the EPA to set National Ambient Air Quality Standards (NAAQS)for the following seven contaminants:

::*Ozone
::*Carbon Monozide
::*Lead
::*Nitrogen Dioxide
::*Sulfur Dioxide
::*PM10: Partulate matter with mean diameter less than 10 μm.
::*PM2.5: Partulate matter with mean diameter less than 2.5 μm.

In addition to these seven contaminatns, the CAA also empowered EPA to regulate an additional 189 hazardous air pollutants listed in the National Emission Standards for Hazardous Air Pollutants. Failure to meet NAAQS levels will result in the requirement of remediation steps to be taken to lower emissions before the plant is allowed to be operational.

===== The Clean Water Act =====

The Clean Water Act was first passed in 1972 and was amended in 1977 and 1987. It seeks to achieve clean water for swimming, boating, and protecting fish and water life. This act mandates that a permit from the EPA must be issued for discharge of pollutants into navigable waters.

===== The Safe Drinking Water Act =====

The Safe Drinking Water Act was passed in 1974. It empowers the EPA to set standards on the required purity of any water which could be used for drinking.

===== The Resource Conservation and Recovery Act =====

The Resource Conservation and Recovery Act was passed in 1976 to protect groundwater from contamination. This Act states that all waste producers are legally liable at any time from waste production to final disposal. Hazardous waste must be clearly labeled and tracked in transport and treated to levels specified by the EPA.

==== Waste Minimization and Management ====
===== Waste Minimization =====
Production of waste is arises naturally in any plant and require a noticeable amount of resources to take care of. Before even considering methods of managing ways, cost can significantly be reduced by efficient management by source reduction. Below is a five-step review often conducted to minimize waste production (Towler and Sinnott, 2013):

::1. Identify waste: Identify what waste products are produced.

::2. Economical Impact: Determine the size of the waste stream and the cost of treatment

::3. Root causes: Determine the root cause of the waste streams.

::4. Modifications: Analyze the effectiveness and cost of potential solutions.

::5. Implement: Implement and optimize solutions of waste management.

Below are some source reduction strategies which can be employed (Towler and Sinnott, 2013):

::* Purification of feeds: Impurities in feed streams can lead to side reactions and formation of waste. Either purchase of purer feeds or employment of purification techniques which do not generate more waste can be used. Purification of feeds will also lead to the reduction of purge and vent streams.

::* Protect catalysis and adsorbents: Catalysts are sensitive to containment in the feed and be deactivated. One method of protecting the catalyst or adsorbent is by employing a guard bed of material to absorb or filter out contaminants.

::* Eliminate use of extraneous materials: Limiting the diversity of solvents is beneficial. The mixing of different solvents can result in waste formation when solvents are degraded.

::* Increase recovery from separations: Higher product recovery results in lower concentrations of products in the the waste streams and less waste formation.

::* Improve fuel quality: Cleaner-burning fuel can have less harmful emissions.

::* Recycle or sell side-products: Rather than processing side-products, attempt to identify companies which might use the waste as raw material for another process.

Keep in mind for all the strategies which can be employed to minimize waste production and therefore waste treatment, the overall cost must be considered. The savings from minimizing waste must be more than the additional cost implementing minimization.

===== Waste Management =====
There are many methods of waste treatment and safe disposal. The availability and efficiency of these methods depend heavily on location. Adherence to federal, state, and local laws may further restrict the availability, of some of these techniques. Common techniques include:

::* Dilution and dispersion.
::* Discharge into municipal sewer.
::* Physical treatments: absorption, adsorption.
::* Chemical treatment: precipitation, neutralization.
::* Biological treatment: composting, anaerobic digestion.
::* Incineration.
::* Landfill at controlled sites.
::* Sea dumping.

== Economical definition of cost ==

=== Cost ===
All of the above criteria ultimately influence the capital and operating costs of a plant, and its expected lifespan.

<math>TC = r K + w L</math>

Local wages, prices of chemical feedstock, shipping costs, and utilities all contribute to total operating costs.

Property prices, rental fees, taxes, and existing company property in the area contribute to recurring investment costs.

== Site Layout: Design and Construction ==

=== Site Layout ===

The needs of a site for a chemical process vary considerably from process to process. In general, however, all chemical plants require the following (Towler and Sinnott, 2013):

::*Shipping and receiving of products and raw materials
::*Storage
::*Utilities
::*Offices and laboratories for management and quality control personnel
::*Medical and fire services for emergency management
::*Cafeterias, parking lots, and other amenities for employees.

These auxiliary buildings are often referred to as ancillary structures and they are placed within a chemical process to minimize transportation of goods and personnel, and to maximize safety. The following procedure is followed when determining the site layout of a chemical process (Mecklenburgh, 1985):

::1. Major process equipment is placed in a logical order to minimize transportation of process streams. Extra emphasis is placed on the separation and treatment of hazardous materials as quickly as possible.

::2. Utilities such as boilers and power plants are placed to minimize transportation of utility to its use within the process. Utilities are usually consolidated into one section of the chemical plant because they are usually generated together. For example, a boiler produces high pressure steam; half the steam is sent through a turbine to generate electricity and to expand the steam into low pressure steam.

::3. Shipping and receiving are placed wherever there is a need to conform to preexisting infrastructure. For example, if the plant is located on a harbor, shipping and receiving for all barge shipments are located by the water. If the plant is built next to a railway, shipping by rail is located next to the tracks.

::4. Storage tanks and warehouses are consolidated as much as possible. Storage of raw materials and products are stored between where they enter or exit the process and where they are shipped or received.

::5. Ancillary buildings are placed to minimize time personnel spend traveling around the site.

::6. Offices and labs are located as far away from hazardous processes as possible.

::7. Walkways and roadways are added as needed to assist with construction and transportation during plant operation.

=== Site Construction ===
Site construction, along with process design, is an iterative process that follows a multi-step procedure (Mecklenburgh, 1985).

==== Stage One Layout ====

The "Proposal" or Stage One layout is the first step towards designing a site layout. The purpose of the Stage One layout is to assess the feasibility of the process according to the cost, hazard, risk, and environmental standards set by the interested parties.

The information included in a Stage One layout is the relative position of buildings and process equipment, and any other data that may come from a preliminary case study of a particular process. Additionally, preliminary estimates by manufacturers and contractors for process equipment and ancillary structures, as well as local building codes and regulations are used in generating the Stage One Layout.

Usually, different layouts for the same process may produce different costs. At this stage in development, many different layouts should be generated and the different layouts should be compared in a systematic way. It is usually very difficult to tell which layout is superior based purely on inspection. Once a Stage One design is finalized, the layout can move on to the next stage.

==== Stage Two Layout ====

Stage Two Layouts are generated based on the finalized Stage One design. Changes to the Stage One design are minimized. The purpose of the Stage Two Layout is to determine an accurate detailed cost of the entire process. Additionally, detailed hazard and environmental information is determined and submitted to all involved regulatory parties at this stage.

==== Final Stage Layout ====

After the detailed cost information, hazard, and environmental information are approved, the Final Design layout commences. At this stage, detailed drawings of all equipment, piping, and layouts are finalized. At the conclusion of the Final Stage layout, orders with contractors are placed and fabrication of process equipment begins, and the site land is purchased. Essentially, this is the "point of no return."

==== Construction ====

The first step in constructing the plant is remediation and preparation of the land for construction of a chemical plant. This can include clearing the land of trees and vegetation, removing other natural obstacles such as boulders and ditches, implementing a drainage system, landscaping, grading to remove difficult topography, and anything else that is necessary. Site selection attempts to minimize costs associated with this step, but there is invariably some form of preparation required for every site.

The second step is to construct all roadways, sidewalks, and fences required for both plant operation and plant construction. Costs associated with this step can range from 2 to 10 percent of the total capital investment for a chemical plant (Peters et al., 2002).

Process equipment and buildings are then constructed as soon as they are available. While construction schedules vary considerably from process to process, in some cases it is possible to perform the final construction steps once the process has already begun to operate, and the construction schedule is designed with this in mind (Mecklenburgh, 1985).

A new aspect of construction of process equipment is a modular approach, where process equipment is assembled as completely as possible by the manufacturer and shipped while assembled. The advantage to this approach is a more comprehensive testing of the equipment by the manufacturer and less installation time once the equipment has arrived on site (Towler and Sinnott, 2013).

== References ==

Mecklenburgh JC. Process plant layout. New York: Halsted Press; 1985.

Peters MS, Timmerhaus KD, West RE. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw-Hill; 2002.

Towler G, Sinnott R. General Site Considerations. In: Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013. p. 505-524.

== External links==
* [https://en.wikipedia.org/wiki/Chemical_plant_cost_indexes Wikipedia - Chemical plant cost indexes]
* [https://en.wikipedia.org/wiki/Chemical_plant#Clustering_of_Commodity_Chemical_Plants Wikipedia - Clustering of Commodity Chemical Plants]

Block Flow Diagram

2015-03-02T04:23:11Z

Jian: /* References */

Author: Nick Pinkerton, Karen Schmidt, and James Xamplas (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: February 2, 2014

 


__TOC__

==Introduction==
A block flow diagram (BFD) is a drawing of a chemical processes used to simplify and understand the basic structure of a system. A BFD is the simplest form of the flow diagrams used in industry. Blocks in a BFD can represent anything from a single piece of equipment to an entire plant. For a complex process, block flow diagrams can be used to break up a complicated system into more reasonable principle stages/sectors.

==Overview==
===Uses===
Creating a BFD is often one of the first steps in developing a chemical process. Different alternatives can be easily and inexpensively compared at an early stage using simple BFDs. Once alternatives have been chosen, the BFD serves as a starting point for a complete process flow diagram (PFD).

A BFD is a useful tool for reports, textbooks and presentations when a detailed process flow diagram is too cumbersome. These models allow for the reader to get an overall picture of what the plant does and how all the processes interact. These can be understood by people with little experience with reading or creating flow diagrams (Towler and Sinnott, 2013).

===Models===
BFDs come in many forms and styles. They can be extremely simple or very detailed in their explanation of a process.
====I/O Diagrams====
The simplest form of BFD, the I/O (input/output) diagram (Biegler et al., 1997), provides the material streams entering and exiting the process. The diagram is modeled below using arrows entering and exiting a process box to represent the inputs and outputs, respectively.

[[File:Io_example.JPG|center|frame|Figure1. I/O Diagram]]

====Block Flow Plant Diagram====
This model of flow diagram is used to explain the general material flows throughout an entire plant. They will be generalized to certain plant sectors or stages. These documents would help orient workers to the products and important operation zones of a chemical facility (Peters and Timmerhaus, 2003).

====Block Flow Process Diagram====
This model will concentrate on a particular sector/area of a chemical plant. This would be a separate flow diagram that details what would have been present inside of one of the blocks in the plant diagram. These diagrams may be more or less complicated than the plant diagram but will focus on only a small sub-section of the overall process (Peters and Timmerhaus, 2003).

===Conventions===
There are several conventions regarding the construction and format of BFDs that are commonly used in the engineering community. Some of the recommended conventions are:

# Operations/equipment are represented with blocks
# Material flows are represented with straight lines with arrows giving the direction of flow
# Lines are horizontal and/or vertical, with turns at 90 degree angles
# Flows go from left to right whenever possible
# If lines cross, the horizontal line is continuous and the vertical line is broken
# Light streams (gases) are typically closer to the top of the BFD than are heavy streams (liquids or solids)
# Critical information unique to the process (such as a chemical reaction) is supplied
# A simplified material balance should be provided (Seider et al., 2004)

==Example 1: Production of Benzene==
Toluene and hydrogen are used as [https://processdesign.mccormick.northwestern.edu/index.php/Define_product_and_feed feed stocks] for the production of benzene. The toluene and hydrogen are sent to a reactor, and the effluent is sent to a gas separator where the noncondensable gases are discharged from the system. The bottoms of the separator provides a liquid feed to a still where the lighter benzene gas is collected as the distillate and the bottom toluene draw is recycled back into the reactor. The BFD provided shows the reaction, the stream names, and the mass flow of the inlets and outlets. There are many components of this system (heat exchangers and pumps, etc.) that are not represented because they are not vital for an understanding of the main features of the process.
[[File:Benzene_prod_example.JPG|center|frame|Figure 2. Block flow process diagram for the production of benzene (Turton et al., 2012)]]

==Example 2: Oxidation of Propene to Acrylic Acid==
Propane is dehydrogenated to propene, which is oxidized to acrolein first and then further oxidized to acrylic acid. The products are separated in the end to give acrylic acid and various by-products. The by-products are further separated to yield a propane recycle stream. Each block in the BFD provided shows what each individual unit is doing along every step of the process. It also shows inlet and outlet streams, as well as byproducts and recycle streams. A BFD in this style is helpful so that all materials can be seen, every step of the process is outlined, and byproducts can be taken into consideration for waste removal/treatment.
[[File:Acrylicacidexample.JPG|center|frame|Figure 3. Block flow process diagram for the production of acrylic acid (Khoobiar et al., 1984)]]

==References==

Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Khoobiar S, Porcelli R, inventor; The Halcon Sd Group Inc., assignee. Conversion of propane to acrylic acid. European patent EP0117146. 1984 May 5.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Process alternatives and flowsheeting

2015-03-02T04:22:29Z

Jian: /* References */

Authors: Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: 2/9/2014

 

==Introduction==
Any given chemical process is composed of a series of chemical operations, performed by one or several related pieces of equipment working to accomplish a given task. However, as more of these elements within a process accumulate, it becomes difficult to track the progress and conditions of a process or utility stream throughout the process. For this reason, process flowsheets are developed to better visualize and summarize information about a process. Having a process flowsheet also allows design engineers to visualize the many alternatives, and how those alternatives affect the rest of the process.

==Flowsheet Presentation==
Different types of flowsheets exist for illustrating a process. These different types of flowsheets contain different degrees of detail and are usually drafted at different stages in the development of the process. This information also varies slightly from company and department to department as to what information is contained on which type of flowsheet.

===Block Diagrams===
Block diagrams are usually generated very early in the design process, and utilize labeled boxes to illustrate process equipment. These diagrams communicate the general idea behind a process in terms of what types of equipment will be present, and what order the process stream passes through the equipment, but it does not contain detailed information regarding equipment design or stream conditions. Usually, material balance information and flow rates of many streams are available, but some streams may be unspecified. For this reason, they are not useful as final engineering schematics, but are more useful as a tool for communicating during early stages in process development.

[[File:BFD Example.gif|options|A simple example of a block flow diagram.]]

===Process Flow Diagrams===
Process Flow Diagrams (PFDs) contain more detail than block diagrams. They contain details of all process equipment present; while in a Block Diagram, separations may be represented by a box labeled "separator," in a PFD all equipment, including flash separators, absorption columns, and distillation columns, are represented and connected by the appropriate piping. Additionally, PFDs contain all pumps, compressors, and heat exchangers as well, while these less important pieces of equipment may be absent from a Block Diagram.

Furthermore, industry standard symbols are used to represent different types of equipment within a PFD. Examples of some symbols used in PFDs to denote certain types of equipment can be found at the following website: http://www.edrawsoft.com/pfdsymbols.php. These symbols also come standard with the flowsheeting software tool Microsoft Visio.

While mass flow rate data may or may not be specified on Block Diagrams, PFDs contain detailed information about every stream including flow rate, composition, pressure, temperature, enthalpy, and any other relevant information. If this information is difficult to display on a PFD in an organized way, a stream table may be attached as a reference, containing this information. Typically, the operating basis, such as the operating hours per year, is also indicated on the PFD. It is normal practice not to display utilities on the PFD in order to avoid clutter.

A PFD is typically organized to reflect the proposed layout of the chemical plant, with different layouts already being experimented with at this early phase of design.

[[File:pfd example.gif|options|]]

===Piping and Instrumentation Diagrams===
The most detailed level of flowsheeting is a Piping and Instrumentation Diagram (P&ID). A P&ID will contain all of the detail on a PFD, but will another level of detail such as pipe diameters and construction, valves, actuators, measuring equipment, and all equipment related to process controls. P&IDs will also contain relevant utility information.

==The Anatomy of a Chemical Manufacturing Process==
Chemical manufacturing process
Components of a chemical process can be divided by these categories: raw material storage, feed preparation, reaction, product separation, purification, and product storage. Unless made on site or provided by neighboring companies, raw material or supply of reactant has to be bought and stored. The feeds have to be prepared and let the reaction run. The product has to be separated and maybe sometimes recycled. The product is purified as a product and is stored for its final usage or transportation.
Continuous and batch processes
Processes are usually continuous or batch. Batch processes are commonly used for food products, pharmaceutical products, personal care product, and specialty chemicals. Continuous processes are economical for large scale production. Batch allows production of multiple different products based on the reactor time; quality control is much easier. It is also easier to clean and maintain a sterility. Downside of the batch is that the scale of the production is limited and scale up is hard. Recycle and heat recovery is much harder, producing more waste byproduct and energy loss.
Conversion and yield
Conversion measures a fraction of the reagent that has reacted. Yield is a measure of a plant performance. Yield is usually defined by moles of product formed over moles of reactant times multiplied by a stoichiometric factor. One thing to note is that the conversion is related to reactants and yield is related to the products. Selectivity measures efficiency of the reactor in converting reagent to the desired product. It is calculated by moles of product produced over moles of product that could have been formed if all the reactant had converted completely.
Recycles and Purges
Recycle refers to processes in which a flow stream is returned to an earlier stage. This is common process when valuable reagent is not fully reacted; unreacted material is separated and added back. Recycle stream complicates the mass balance of the processes and necessitates a purge stream, which prevents a buildup of unwanted material in the process.

==Selection Modification, and Improvement of Commercially-Proven Processes==
Modification and Improvement of Processes
When in designing processes, companies usually do not invest heavily on risk inherent project. They hire design teams that evaluate and optimize the different existing designs. The processes may need modification to fit the desired products such as addition or substitution of streams or interchange reactions and catalysts.
Information on modification
The chemical process industries are competitive, so the details of the processes are restricted and limited. Detailed information on reaction kinetics and process conditions can be found using the references such as Encyclopedia of Chemical Technology and Ullmann’s Encyclopedia of Industrial Technology. Patents are another useful information source on designing processes. Since the patent gives its owner the right of particular information, extracting the details may be limited. Other times, companies hire consulting firms to collect necessary information on designing processes.
Modification
Improvements in the process economics are very desirable. This is usually achieved by improving following parameters: reactor selectivity, process yield, process energy efficiency, and process fixed costs. Capital investment and working capital can be reduced to give improved process economics as well. Other factors that can be improved on process designs are plant safety, reliability, and environmental impact. These factors can be achieved by substituting less hazardous material and using reliable pieces of equipment.

==Synthesis of Novel Flowsheets==
Design of completely new flowsheets are usually avoided due to the financial and safety risk they carry. Process synthesis attempt to minimize risk and maximize potential process such that the financial reward is greater than the risk. Process synthesis has been aided by process simulation programs as well as experience in similiar processes.

===Procedure for Flowsheet Synthesis===
# Generate Process. Conduct initial design basis with as much of available data as possible.
# Initial Economics. Collect cost of feeds and price of products to determine profitability of process.
# Set Yield Targets. Estimate target yields in order to yield profitability.
# Preliminary Economic Assessment. Obtain a preliminary cost of production.
# Refine Process Structure. Create a complete PFD containing all processes and equipment.
# PFD Review. Review PFD with a committee consisting of the design team and experts.
# Preliminary Process Hazard Analysis (PHA). Identify hazard in the process and rectification steps.
# Revise Economic Assessment. Conduct economic assessment based on additional modification and ensure similar profit from products.
# Optimization. While it might not be possible to have sufficient data to properly optimize the system at the time the design team is performing processes, the design team should optimize the design based on the data available. While it might be necessary to perform optimization on different sections of the process due to complexity, the overall optimization with advantages and disadvantages should be considered.

===Set Targets in Process Synthesis===
Applicable heuristics can be used to check answers or generate preliminary values if insufficient data are available.

==PFD Review==
Review of the PFD is an important part of the design process whether the flow sheet is newly generated or altered from existing designs. The process of PFD is usually done in committee consisting of the design team and relevant unbiased consultants.

===PFD Review Procedures===
# PFD Printout. Display the PFD on a wall such that it is visible to all members of the review committee. Allow enough space between equipment for addition and notes.
# Walkthrough. Introduce the PFD, describing all streams and process operations.
# Questions. The review group should challenge the design team, paying special attention to potential missing equipment or redundant equipment. Safety and adequate control systems should also be questioned.
# Follow-up. If there are unanswered questions which need to be addressed, the design team should perform the necessary analysis. Corrections made during the review should be noted and added to the PFD. Notes describing issues, concerns, and future steps should be distributed after the meeting adjourns.
# More PFD Reviews. Depending on the number of changes performed during the review process, further review process may be necessary.

==Conclusion==
Process alternatives and flowsheeting offers a methodological way of organizing and presenting design processes. Numerous tools has been introduced to aid with process presentation to offer organized design processes and allow further modification of them.

==References==
Towler G, Sinnott R. Process Flowsheet Development. In: Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013. p. 33–102.

Reactors

2015-03-02T04:22:13Z

Jian: /* References */

Title: Reactors

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: February 4, 2014


__TOC__

=Introduction=

The center of any chemical process is the reactor, where chemical reactions are carried out to transform feeds into products. Reactor design is a vital step in the overall design of a process. It is important to ensure that the equipment specified will be capable of achieving the desired yields and selectivity.

==Ideal Reactors==

===Batch Reactors===

In a batch reactor, the reagents are added together and allowed to react for a given amount of time. The compositions change with time, but there is no flow through the process. Additional reagents may be added as the reaction proceeds, and changes in temperature may also be made. Products are removed from the reactor after the reaction has proceeded to completion.

Batch processes are suitable for small-scale production (less than 1,000,000 lb/yr) and for processes where several different products or grades are to be produced in the same equipment (Douglas, 1988). When production volumes are relatively small and/or the chemistry is relatively complex, batch processing provides an important means of quality control.

===Plug Flow Reactor (PFR)===

A PFR with tubular geometry has perfect radial mixing but no axial mixing. All materials hav the same residence time, τ, and experience the same temperature and concentration profiles along the reactor. Equation for PFR is given by:

<math>dM = \Re dV</math>

where M = molar flow rate, dV is the incremental volume, and <math>\Re</math> is the rate of reaction per unit volume.

This equation can be integrated along the length of the reactor to yield relationships between reactor resident time and concentration or conversion.

===Continuously Stirred Tank Reactor (CSTR)===

The stirred tank reactor models a large scale conventional laboratory flask and can be considered to be the basic chemical reactor. In a CSTR, shown in Figure 1, there is no spatial variation- the entire vessel contents are at the same temperature, pressure, and concentration. Therefore the fluid leaving the reactor is at the same temperature and concentration as the fluid inside the reactor.

The material balance across the CSTR is given by:

<math>M_\text{in}-M_\text{out}= \Re V</math>

Some of the material the enters the reactor can leave immediately, while some leaves much later, so there is a broad distribution in residence time as shown in Figure 1.

[[File:CSTR.PNG]]

''Figure 1.'' Continuously Stirred Tank Reactor (Towler and Sinnott, 2013)

More information on stirred tanks can be found in the [[#Mixing in Industrial Reactors|Mixing]] section.

=General Reactor Design=

The design of the reactor should not be carried out separately from the overall process design due to the significant impact on capital and operating costs on other parts of the process (Towler and Sinnott, 2013).

==Step 1: Collect Required Data==

Out of all process equipment, reactor design requires the most process input data: reaction enthalpies, phase-equilibrium constants, heat and mass transfer coefficients, as well as reaction rate constants. All of the aforementioned parameters can be estimated using simulation models or literature correlations except for reaction rate constant constants, which need to be determined experimentally (Towler and Sinnott, 2013).

===Enthalpy of Reaction===

: The heat given out in a chemical reaction is based on the enthalpies of the component chemical reactions, which are given for standard temperature and pressure (1 atm, 25 C). Values for standard heats of reaction can be found tabulated in literature, or can be calculated from heats of formation or combustion. Care must be taken to quote the basis for the heat of reaction and the states of reactants and products.

: The following equation is used to convert enthalpies from standard conditions to the process conditions:

: <math>\Delta H_\text{r,P,T} = \Delta H_\text{r}^{\circ} + \int_{1}^{P}\left[ \left ( \frac{\partial H_{prod.}}{\partial P} \right )_T - \left ( \frac{\partial H_{react.}}{\partial P} \right )_T \right ] dP + \int_{298}^{T}\left[ \left ( \frac{\partial H_{prod.}}{\partial T} \right )_P - \left ( \frac{\partial H_{react.}}{\partial T} \right )_P \right ] dT </math>

: If the effect from pressure is not significant and only Temperature needs to be accounted for, the following equation should be used:

: <math>\Delta H_\text{r,T} = \Delta H_\text{r}^{\circ} + \Delta H_\text{prod.} + \Delta H_\text{react.}</math>

===Equilibrium Constant and Gibbs Free Energy===

: <math>\Delta G = -\mathbf{R} T \ln K </math>

: Where <math>\Delta G</math> is the change in Gibbs free energy from the reaction at temperature <math>T</math>, <math>\mathbf{R}</math> is the ideal gas constant, and <math>K</math> is the reaction equilibrium constant, given by:

: <math>K = \prod_{i=1}^n {a_i}^{\alpha_i} </math>

: where <math>a_i</math> is the activity of component i, <math>\alpha_i</math> is the stoichiometric coefficient of component <math>i</math>, and <math>n</math> is the total number of components.

: Equilibrium constants can be found in the literature and are useful for evaluating the rates of forward and reverse reactions. Care must be taken to the experimental design used for the literature equilibrium constants to make sure they are consistent with the conditions of the actual process reactor. For more complicated reactions consisting of several sequential or simultaneous reactions, the equilibrium is found by minimizing the Gibbs free energy (Towler and Sinnott, 2013). Commercial process simulation programs use the Gibbs reactor model in this way.

===Reaction Mechanisms, Rate Equations, and Rate Constants===

: In most cases the main process reaction rate equations and rate constants cannot be predicted from first principles and must be approximated (Towler and Sinnott, 2013). This is due to the following:

* Use of heterogeneous catalysis or enzymes which lead to Langmuir-Hinshelwood-Hougen-Watson or Michaelis-Menten kinetics
* Mass transfer between vapor and liquid or two liquid phases
* Multistep mechanisms whose rate expressions do not follow overall reaction stoichiometry
* Competing side reactions

: As a result the main process reaction is usually approximated as first- or second-order over a narrow range of process conditions (temperature, pressure, species concentrations) to estimate the residence time required for a target conversion. Rate equations are always a fit for experimental data and should thus be used for interpolation within the data. It is important to collect more data when extrapolating, especially for exothermic reactions which have the potential for runaway (Towler and Sinnott, 2013).

===Heat and Mass Transfer Properties===

====Heat Transfer====
:: The design of internal heating or cooling devices can be found in [https://processdesign.mccormick.northwestern.edu/index.php/Heat_Transfer_Equipment Heat Transfer Equipment]. Correlations for tube-side heat-transfer coefficients for catalyst-packed tubes of a heat exchanger are given below:

:: For heating: <math> {{h_i d_t} \over \lambda_f} = .813 {\left ( \frac{\rho_f u d_p}{\mu} \right )}^{.9} e^{-6 d_p / d_t} </math>

:: and for cooling: <math> {{h_i d_t} \over \lambda_f} = 3.50 {\left ( \frac{\rho_f u d_p}{\mu} \right )}^{.7} e^{-4.6 d_p / d_t} </math>

:: where <math>h_i</math> is the tube-side heat transfer coefficient for a packed tube, <math>d_t</math> is the tube diameter, <math>\lambda_f</math> is the fluid thermal conductivity, <math>\rho_f</math> is the fluid density, <math>u</math> is the superficial velocity, <math>d_p</math> is the effective particle diameter, and <math>\mu</math> is the fluid viscosity.

====Diffusion Coefficients====

:: Diffusion coefficients are necessary when mass transfer can limit the rate of reaction, such as in catalytic reactions or reactions involving mass transfer processes such as gas absorption, distillation, and liquid-liquid extraction.

:: The diffusivity for gases can be estimated by the following correlation (Fuller, Schettler, Giddings):

:: <math> D_v = \frac{1.013 \times 10^{-7} T^{1.75} {\left ( \frac{1}{M_a} + \frac{1}{M_b} \right )}^{1/2} }{P {\left [ {\left ( \sum_{a} v_i \right )}^{1/3} + {\left ( \sum_{b} v_i \right )}^{1/3} \right ]}^2 } </math>

:: where <math>D_v</math> is the diffusivity, <math>T</math> is temperature, <math>M_a , M_b</math> are the molecular masses of components <math>a</math> and <math>b</math>, <math>P</math> is the total pressure, and <math>\sum_{a} v_i , \sum_{b} v_i</math> are the summation of special diffusion volume coefficients for components <math>a</math> and <math>b</math>, given in the table below:

:: (volume coefficient table from towler)

:: Wilke and Chang developed a correlation for estimating the diffusivity of components in the liquid phase:

:: <math> D_L = \frac{1.173 \times 10^{-13} {(\phi M_w)}^{1/2} T}{\mu V_m^{.6}} </math>

:: where <math>D_L</math> is the liquid diffusivity, <math>\phi</math> is an association factor for the solvent, <math>M_w</math> is the molecular mass of the solvent, <math>\mu</math> is the solvent viscosity, <math>T</math> is the temperature, and <math>V_m</math> is the molar volume of the solute at its boiling point. This correlation holds for organic compounds in water but not for water in organic solvents.

====Mass Transfer====

:: For multiphase reactors it is necessary to estimate the mass transfer coefficient.

:: The equation of Gupta and Thodos predicts the mass transfer coefficient for a packed bed of particles:

:: <math>\frac{k d_p}{D} = 2.06 \frac{1}{\epsilon} {Re}^{.425} {Sc}^{.33} </math>

:: where <math>k</math> is the mass transfer coefficient, <math>d_p</math> is the particle diameter, <math>D</math> is the diffusivity, <math>Re</math> is the Reynolds number calculated using the superficial velocity through the bed, <math>Sc</math> is the Schmidt number, and <math>\epsilon</math> is the bed void fraction.

:: Mass transfer between vapor and liquid in an agitated vessel can be described by the Van't Riet equations:

:: For air-water: <math> k_L a = 0.026 {\left ( \frac{P_a}{V_{liq}} \right )}^{.4} Q^{1/2} </math>

:: and for air-water-electrolyte: <math> k_L a = 0.002 {\left ( \frac{P_a}{V_{liq}} \right )}^{.7} Q^{.2} </math>

:: where <math>k_L</math> is the mass transfer coefficient, <math>a</math> is the interfacial area per unit volume, <math>Q</math> is the gas volumetric flow rate, <math>V_{liq}</math> is the liquid volume, and <math>P_a</math> is the agitator power input.

:: Fair's method for calculating the mass transfer coefficient for low viscosity systems is given by:

:: <math>\frac {{(k_L a)}_{system}}{{(k_L a)}_{air-water}} = {\left ( \frac{D_{L,system}}{D_{L, air-water}} \right )}^{1/2} </math>

:: where <math>D_L</math> is the liquid phase diffusivity.

:: Mass transfer correlations for vapor-liquid systems should be used with caution when there are surfactants (Towler and Sinnott, 2013).

==Step 2: Select Reaction Conditions==

A major determining factor in reactor type selection is the choice of operating conditions. Optimal process operation usually involves optimizing process yield and not necessarily reactor yield. Based on the preliminary economical analysis a target range of yields and selectivities can be chosen. The final reaction conditions must be verified experimentally to ensure target yields and selectitivities are realized (Towler and Sinnott, 2013).

===Chemical or Biochemical Reaction===

If the desired product is to be produced by a biochemical reaction the chosen conditions must maintain the viability of the biological agent (e.g. microorganisms or enzymes). Proteins denature outside of their specific temperature and pH ranges, while living organisms require specific concentrations of oxygen and other solutes to survive and cannot withstand high shear rates. See [[Reactors#Bioreactors|bioreactors]] for further information on their design.

===Catalyst===

A catalyst is used to increase the reaction rate by lowering the activation energy without being consumed in the reaction. The use of catalyst imposes operating condition constraints as the catalyst must maintain activity for a period of time between catalyst regenerations. Catalyst deactivation can be accelerated by high temperatures as well as contaminants in the feed or recycle streams.

===Temperature===

Increasing the reaction temperature will increase the reaction rate, diffusivities, and mass-transfer rates. Temperature also affects the equilibrium constant: higher temperature increases equilibrium constant for endothermic reactions and decreases it for exothermic reaction- see the figure below.

[[File:Temperature equilibrium constant.PNG|Effect of temperature on equilibrium constant (Towler and Sinnott, 2013)]]

:: Figure 2. Effect of temperature on equilibrium constant (Towler and Sinnott, 2013)

Increased reaction temperature will reduce the cost of reactor design except for the following scenarios/considerations (Towler and Sinnott, 2013):

* Biochemical reactions where living organisms could die at high temperatures
* Presence of organic compounds that undergo thermal degradation
* Unwanted side reactions that accelerate with higher temperature, such as polymerization or auto-oxidation
* Oxidation reactions where selectivity decreases at higher temperatures as product oxidation tends to increase
* Exothermic reactions as it is more difficult to control the temperature and there is risk of reaction run away
* Construction cost of the reactor can become prohibitive at extremely high temperatures

===Pressure===

The main consideration when choosing the reactor pressure is to maintain the reaction at the desired phase for the selected temperature. The pressure can also be chosen to allow for vaporization of a component, making separation of a product easier, shifting the reaction equilibrium, or removing heat from the reactor. Increasing pressure for reactions that take place in the gas phase increases reactant activity and thus the reaction rate. Reactor yields follow Le Chatelier's principle: for reactions that increase number of moles lower pressure will increase equilibrium conversion, for reactions that decrease number of moles lower pressure will decrease equilibrium conversion. Increasing the pressure in gas-liquid reactions increases the solubility of the gas in the liquid which increases the reaction rate.

===Reaction Phase===

Reactions are usually carried out in liquid or gas phases as fluids are easier to handle, heat and cool, and transport than solids. For reagents or products in the solid phase a suspension in liquid or gas is usually used. The phase of the reaction is usually determined by reactor temperature and pressure. Liquid-phase operation is usually preferred due to the highest concentrations and greatest compactness. However, at temperatures above the critical temperature there cannot be a liquid phase. The pressure can sometimes be adjusted to keep all reagents in the liquid phase, however when this is not possible a multiphase reactor will be necessary. If mass transfer limitations become too significant it can be beneficial to reduce the pressure such that the reaction temperature is above the dew point and the reaction is carried out in the vapor phase.

===Solvent===

Solvents are used for liquid-phase reactions and can be used for the following:

* Dilution of feed to improve selectivity
* Increasing solubility of gas-phase components
* Dissolving solids in the reacting phase
* Increasing thermal mass which lowers temperature change per unit volume from reaction
* Improving miscibility of mutually insoluble components

Solvents should be inert in the main reaction and should not react with products or feed contaminants. Solvents should also be inexpensive and easily separated from the reaction products. Some widely used process solvents and their properties are given in the table below:

[[File:Commonly_used_process_solvents_part1.PNG|850px|]]

[[File:Commonly_used_process_solvents_part2.PNG|850px|Commonly used process solvents (Towler and Sinnott, 2013)]]

::Commonly used process solvents (Towler and Sinnott, 2013)

===Concentrations===

Higher concentrations of feed can lead to higher reaction rate, however for exothermic reactions high feed concentrations should be avoided. Feed compounds are usually not supplied in stoichiometric ratio as using a higher concentration of one feed can lead to increased selectivity towards the desired product.

Understanding the effect of feed contaminants and by-products is essential to reactor design; they can play significant roles in reactor selectivity and performance. When recycling attention must be paid to by-products; those formed through reversible reactions can be recycled leading to improved overall selectivity. Feed contaminants generally pose a greater issue than by-products due to their ability to poison catalysts or kill biological organisms. If a feed contaminant is particularly detrimental to the reactor performance it should be removed upstream of the reactor.

Inert compounds will usually increase reactor cost due to the larger volume required, as well as increase downstream separation costs; they can still be advantageous for the following circumstances:

* Inerts in gas-phase reactions reduce partial pressure of reagents which can increase equilibrium conversion in reactions that lead to an increase in number of moles
* Feed compound reacting with itself or products can be reduced by dilution using inerts
* Inerts can allow operation outside of the flammability envelope
* Reaction solutions can be buffered to control pH

==Step 3: Determine Materials of Construction==

A preliminary analysis of the materials of construction for the reactor can be conducted after the reaction conditions have been specified. Particularly important in this analysis are the temperatures and pressures the process will run at. At extreme conditions, costly alloys may need to be used. In addition, the designer must ensure that process streams will not react with materials used in process equipment.

==Step 4: Determine Rate-Limiting Step and Critical Sizing Parameters==

The key parameters that determine the extent of reaction must be identified by carrying out an experiment plan with a broad range of conditions. In general, the rate of reaction is usually limited by the following fundamental processes. The first three have been discussed in previous sections. Mixing will be developed in more detail in its own section.

* '''Intrinsic kinetics:''' There will usually be one slowest step that governs the overall rate.
* '''Mass-transfer rate:''' In multiphase reactions and processes that use porous heterogeneous catalysis, mass transfer can be particularly important. Often, careful experimentation will be needed to separate the effects of mass transfer and the rate of reaction to determine which is the rate-limiting step.
* '''Heat-transfer rate:''' The rate of heat addition can become the governing parameter for endothermic reactions. Heat-transfer devices such as heat exchangers or fired heaters may need to be used.
* '''Mixing:''' The time taken to mix the reagents can be the limiting step for very fast reactions.

Once rate data have been collected, the designer can fit a suitable model of reaction kinetics. Next, a critical sizing parameter can be specified for the reactor. This will usually be one of the parameters given in Figure 1.

:: [[File:Sizing_Parameters.PNG]]

:: Figure 1. Reactor Sizing Parameters (Towler and Sinnott, 2013)

==Step 5: Preliminary Sizing, Layout, and Costing of Reactor==

The designer can estimate the reactor and catalyst volume from the sizing parameter. This calculation will yield a value for the active reacting volume necessary. Clearly, the actual reactor will need additional space. The geometry of the reactor will depend on the desired flow pattern and mixing requirements (Towler and Sinnott, 2013). The cost of most reactors can be estimated by determining the cost of a pressure vessel with the same dimensions and adding in the cost of the internals (Towler and Sinnott, 2013).

==Step 6: Estimate Reactor Performance==

At this point in the design process, it is important to verify that the proposed reactor will achieve the target conversions and selectivities. A combination of experimental methods, such as pilot plants, and computer simulations can be used to predict the full-scale reactor performance.

==Step 7: Optimize the Design==

The reactor is typically a relatively small fraction of the total capital cost (Towler and Sinnott, 2013), so minimal time should be devoted to optimization to reduce the reactor cost. However, if the target conversion, yields, and selectivities are not met, the process economics could be significantly impacted. Therefore, steps 2 to 6 should be repeated at least until the minimum specifications are met (Towler and Sinnott, 2013).

=Mixing in Industrial Reactors=

Mixing plays an important role in many processing stages, including reactor performance. It is critical to select the appropriate method of mixing in order to ensure the process produces the desired process yields, product purity, and cost effectiveness.

Correlations such as the Reynolds number can be used to determine the extent of mixing and correlate power consumption and heat transfer to the reactor shell (Towler, 2012). In some cases, simple correlations may not be adequate:
* If dead zones cannot be tolerated for reasons of product purity, safety, etc.
* If reactor internals are complex
* If reaction selectivity is very sensitive to mixing
In these cases, it is usually necessary to carry out a more sophisticated analysis of mixing:
* Use computational fluid dynamics to model the reactor
* Use physical modeling (“cold flow”) experiments
* Use tomography methods to look at performance of real reactor

==Gas Mixing==
Gases mix easily because of their low viscosities. The mixing given by turbulent flow in a length of pipe is usually sufficient for most purposes (Towler and Sinnott, 2013). Orifices, vanes, and baffles can be used to increase turbulence.

==Liquid Mixing==
*'''Inline Mixing''' Inline mixers can be used for the continuous mixing of low-viscosity fluids. One inexpensive method involves the use of static devices that promote turbulent mixing in pipelines. Some typical designs are shown in Figures 2(a), (b), and (c).

::[[File:Static_Mixers.PNG]]

::''Figure 2.'' Inline mixers: (a) tee; (b) injection; (c) annular (Towler and Sinnott, 2013)

:: When mixing low viscosity fluids (<50 mNs/m2) with similar densities and flow rates, a simple mixing tee, Figure 2(a), followed by a length of pipe equal to 10 to 20 pipe diameters, is suitable (Towler and Sinnott, 2013).
:: When one flow is much lower than the other, an injection mixer, Figure 2(b&c), should be used. A satisfactory blend will be achieved in about 80 pipe diameters (Towler and Sinnott, 2013). Baffles or other flow restrictions can be used to reduce the mixing length required. These mixers work by introducing one fluid into the flowing stream of the other through a concentric pipe or an annular array of jets (Towler and Sinnott, 2013).

*'''Stirred Tanks''' Stirred tanks were discussed in the [[#Ideal Reactors|Ideal Reactors]] section. Mixing is conducted by an impeller mounted on a shaft driven by a motor. The reactor usually contains baffles or other internals to induce turbulence and prevent the contents from swirling and creating a vortex. Typically, baffles are 1/10 of diameter and located 1/20 of diameter from wall (Towler, 2012). A typical arrangement of agitator and baffles in a stirred tank, and the flow pattern generated, is shown in Figure 3. Mixing occurs through the bulk flow of the liquid and by the motion of the turbulent eddies created by the agitator. Bulk flow is the predominant mixing mechanism required for the blending of miscible liquids and for solids suspension. Turbulent mixing is important in operations involving mass and heat transfer, which can be considered as shear-controlled processes (Towler and Sinnott, 2013).

::[[File:Agitator_Arrangements.PNG]]

::''Figure 3.'' Agitator arrangements and flow patterns (Towler and Sinnott, 2013)

:At high Reynolds numbers (low viscosity), one of the three basic types of impeller shown in Figure 4 should be used. For processes controlled by turbulent mixing, the flat-bladed (Rushton) turbines are appropriate. For bulk mixing, the propeller and pitched-bladed turbines are appropriate (Towler and Sinnott, 2013).

::[[File:Impeller_Types.PNG]]

::''Figure 4.'' Basic impeller types (Towler and Sinnott, 2013)

:For more viscous fluids, paddle, anchor, and helical ribbon agitators (Figures 5(a), (b), and (c)), are used (Towler and Sinnott, 2013). The selection chart given in Figure 6 can be used to make a preliminary selection of the agitator type, based on the liquid viscosity and tank volume (Towler and Sinnott, 2013).

::[[File:Low_Speed_Agitators.PNG]]

::''Figure 5.'' Low-speed agitators (Towler and Sinnott, 2013)

::[[File:Agitator_Selection_Guide.PNG]]

::''Figure 6.'' Agitator selection guide (Towler and Sinnott, 2013)

==Gas-Liquid Mixing==

Gases can be mixed into liquids using the inline mixing or stirred tank methods discussed previously. A special type of gas injector, called a sparger (shown in Figure 7) can also be used. This is a long injection tube with multiple holes drilled in it.

[[File:Gas_Sparger.PNG]]

''Figure 7.'' Gas sparger (Towler and Sinnott, 2013)

A small flow of liquid can be dispersed into a gas stream using a spray nozzle (Figure 8).

[[File:Liquid_Injection.PNG]]

''Figure 8.'' Liquid injection into gas (Towler and Sinnott, 2013)

==Solid-Liquid Mixing==

Solids are usually added to a liquid in a stirred tank at atmospheric pressure. In order to allow more accurate control of dissolved solid concentration, mixing of solids and liquids is often carried out as a batch operation (Towler and Sinnott, 2013).

=Types of Reactors=

Most reactors used in industry approximate the ideal batch reactor, PFR, or CSTR. In fact, real reactors can be modeled as networks or combinations of multiple plug-flow and stirred-tank reactors (Towler and Sinnott, 2013). Examples of real reactors that approximate the flow pattern of ideal reactors are shown in Figure 10. These reactors will be discussed in more detail in the following sections.

[[File:Types_of_Reactors.PNG]]

''Figure 10.'' Ideal reactors and some real reactors that approximate the same flow pattern (Towler and Sinnott, 2013)

==Vapor-Liquid Reactors==

Vapor-liquid reactions are important in many chemical processes. For example, oxygenation and hydrogenation reactions are usually carried out with the organic component in the liquid phase (Towler and Sinnott, 2013). A summary of common goals for vapor-liquid reactors and the reactors used to achieve those goals is shown in Table 1.

{| class="wikitable"
|-
! Goal !! Types of Vapor-Liquid Reactors !! Examples
|-
| Maintain low concentration of gas component in liquid ||
* Sparged stirred tank reactor
* Sparged tubular reactor
||
* Liquid phase oxidations using air
* Fermenters
|-
| Contact gas and liquid over catalyst ||
* Trickle bed reactor
*Slurry phase reactor
||
* Catalytic hydrogenation
|-
| React a component out of the gas phase to high conversion ||
* Multi-stage V/L contactor (reactive absorption column)
* Venturi scrubber
||
*Chemisorption
*Acid gas scrubbing
|}

''Table 1.'' Summary of Vapor-Liquid Reactors (Towler, 2012)

If the residence time requirements are short enough, vapor-liquid contacting columns are preferred because of the high area for mass transfer. Trayed or packed columns can be used to contact vapor and liquid for reaction. The column packing may be catalytically active or could be inert packing (Towler, 2012). Please see the [[separation processes]] section of this website for more information on the types of processes used for the third goal listed.

Stirred tanks or tubular reactors are used when long residence time is needed for the liquid phase (Towler and Sinnott, 2013). These types of reactors and more will be discussed in the [[#Catalytic Processes|catalytic processes]] section of this page.

The reactors listed under the first goal in the table are unique to vapor-liquid processes. The basic concept of a sparger was discussed in the [[#Mixing in Industrial Reactors|mixing]] section. Sparged reactors are shown in Figure 11.

[[File:Sparged_Reactors.png]]

''Figure 11.'' Sparged stirred tank and tubular reactors (Towler, 2012)

The gas is bubbled up through the liquid in a sparged reactor. For smaller bubbles, a porous pipe diffuser can be used instead (Towler, 2012). The designer must allow some disengaging space at the top of the reactor, or entrainment will be excessive. If the gas flow rate is large then the gas flow can be used as the primary means of agitation. Perry's Handbook suggests the following air rates (ft3/ft2min) for agitating an open tank full of water at 1 atm:

{| class="wikitable"
|-
! Degree of agitation !! Liquid depth 9 ft !! Liquid depth 3 ft
|-
| Moderate || 0.65 || 1.3
|-
| Complete || 1.3 || 2.6
|-
| Violent || 3.1 || 6.2
|}

''Table 2.'' Summary of suggested flow rates for gas flow as agitation (Towler, 2012)

==Catalytic Processes==
A catalyst increases the rate of a chemical reaction without itself becoming permanently changed by the reaction. Catalysts allow reactions to be run in smaller reactors and operated at lower temperatures and improve selectivity. Therefore, catalysts will almost always lead to a more economically attractive process than a noncatalytic route (Towler and Sinnott, 2013). Catalysts are normally selected based on performance rather than price since increases catalysts selectivity will almost always quickly pay back any price premium expected by the manufacturer. It is important to test the catalysts under conditions that are representative of process conditions (Towler and Sinnott, 2013).

Catalyst activity often deteriorates over time (Towler, 2012). Common causes of deactivation include:
* Poisoning by components in feed (e.g. base destroys acid catalyst)
* Blockage of pores or active sites by byproducts such as coke
* Thermal or hydrothermal modification of catalyst structure
Slow activity loss can be compensated by:
* Putting in more catalyst (lower space velocity)
* Slowly raising reactor temperature
Rapid activity loss may require moving the catalyst to a continuous regeneration zone (Towler, 2012).

Catalytic reactions can be either homogenous (catalyst is in the same phase as the reagents) or heterogeneous (catalyst is not in the same phase as the reagents).

===Homogeneous Catalysis===

:Homogeneous catalysis can be conducted in the basic batch reactors, PFRs, or CSTRs that have already been discussed. However, when the catalyst is in the same phase as the reagent, recovering this catalyst after the reaction can be difficult and expensive, particularly if the catalyst is sensitive to high temperatures (Towler, 2012). Providing adequate interfacial area is also a challenge of homogeneous catalysis. A reaction often only occurs at the interface or in the boundary layer between the catalyst and the reagents. Increased mixing can increase the rate and selectivity of the reaction, but this can require detailed and expensive mixing equipment (Towler, 2012). For these reasons, reactions requiring homogenous catalysts are not usually used unless an easy separation can be found to recover the catalyst.

===Heterogeneous Catalysis===

: Catalyst recovery in processes involving heterogeneous catalysis is much easier. However, the rate of reaction is limited by the available inter-phase surface area and the mass transfer of reagents and products to and from the interface (Towler, 2012). Therefore, reactors for these processes are design to reduce these limitations.

* '''Fixed Bed Reactors'''

:: In a fixed-bed reactor, the reagent flows over a stationary bed of packed catalyst (Towler and Sinnott, 2013). This is the most common type of reactor used for heterogeneous catalysis as long as the catalyst does not require continuous regeneration and the reaction mixture does not require high agitation (Towler, 2012). The amount of catalyst necessary can be found using the following equations:

::[[File:Catalyst_Calcs.png]]

:: The ratio of the bed height (L) to the diameter (D) determines the distribution of reagents and the pressure drop across the bed. An increased L/D ratio creates a more even distribution and less change of localized deactivation or "hot spots." However, increasing the L/D ratio increases the pressure drop, requiring higher compression and pumping costs (Towler, 2012). The Ergun equation can be used to calculate the pressure drop in packed beds.

:: [[File:Ergun.png]]

::Where V is the superficial velocity (volume flowrate divided by cross-sectional area), μ is the viscosity, Dp is the particle diameter and ε is the porosity of the packed bed (Towler, 2012). Given these trade-offs, it may make sense to split the catalyst over several beds (Towler, 2012).

* '''Radial Flow Reactors'''

:: When there is very little pressure drop available, the L/D ratio must be much less that one (Towler, 2012). A common solution to this is to use a radial flow reactor with the catalyst contained in an annulus between vertical perforated or slotted screens. The fluid flows radially through the bed and the direction of flow can be either inwards or outwards (Towler and Sinnott, 2013). An example of a radial flow reactor is shown in Figure 12.

:: [[File:Radial_flow.png]]

::''Figure 12.'' Radial flow reactor (Towler, 2012)

* '''Moving Bed Reactors'''

:: A moving bed reactor is similar to a radial flow reactor, but the catalyst is moved through the annular space (Towler, 2012).

* ''' Fluidized Bed Reactors'''

:: If the fluid flow is up through the catalyst bed then the bed can become fluidized if the pressure drop is high enough to support the weight of the catalyst. Fluidized beds usually have a lower pressure drop than down flow at high flow rates (Towler, 2012). In addition, fluidizing the catalyst eases the transition from one reaction zone to another.

:: The catalyst bed is fluidized using a distributor to inject fluidization fluid, which is not necessarily the feed. Fluidization occurs when the bed pressure drop balances the weight of the particles, or

::[[File:Fluid_Eqn.png]]

::Where ∆P is the pressure drop, ρp and ρg are the densities of the particle and gas respectively, εm is the porosity at minimum fluidization, and L is the height of the bed (Towler, 2012). Fluidization can only be used with relatively small sized particles (<300 micrometers with gases). The solid material must be strong enough to withstand attrition in the fluidized bed and cheap enough to allow for make-up to replace attrition losses (Towler and Sinnott, 2013). A fluidized-bed reactors must also make allowance for separating the fluid-phase product from entrained solids so that solids are not carried out of the reactor (Towler and Sinnott, 2013).

* '''Trickle Bed Reactors'''

:: Trickle bed reactors are used when all three phases are involved in the reaction. They must ensure good distribution of both the vapor and the liquid, without channeling of either phase (Towler, 2012). In a trickle bed reactor, the liquid flows down over the surface of a stationary bed of solids. The gas phase usually also flows downwards with the liquid, but countercurrent flow is feasible as long as flooding conditions are avoided (Towler and Sinnott, 2013). This requires a more sophisticated distributor like those used for packed distillation columns (Towler, 2012). An example of a trickle bed reactor is shown in Figure 13.

::[[File:trickle_bed.png]]

::''Figure 13.'' Example of trickle bed reactor (Towler, 2012)

* ''' Slurry Reactors'''

::Liquid is mixed up in the liquid in slurry phase reactions. Slurry reactors are prone to attrition of the solids, caused by pumping or agitation of the liquid (Towler and Sinnott, 2013). Slurry-phase operation is usually not preferred for processes that use heterogeneous catalysts because the catalyst tends to become eroded and can be difficult to recover from the liquid (Towler and Sinnott, 2013).

==Bioreactors==

Bioreactors have requirements that add complexity compared to simpler chemical reactors. These reactions often are three-phase (cells, water, and air), need sterile operation, and require heat removal (Towler, 2012). However, biological systems have the following advantages:
* Some products can only be made by biological routes
* Large molecules such as proteins can be made
* Selectivity for desired product can be very high
* Products are often very valuable

===Enzyme Catalysis===

Enzymes are the biological equivalent of catalysts. They can sometimes be isolated from host cells. They are usually proteins and, therefore, most are thermally unstable above ~60 degrees Celsius and active only in water at a restricted pH (Towler, 2012). Enzymes can sometimes be absorbed onto a solid or encapsulated in a gel without losing their structure. In this case, they can be used in a conventional fixed bed reactor. Typically, homogenous reactions are carried out in batch reactors.

===Cell Growth===

Cell growth goes through several phases during a batch, shown in Figure 15.

[[File:Cell_Growth_Rate.png]]

''Figure 15.'' Cell growth and product formation in batch fermentation (Towler and Sinnott, 2013)

* I: Innoculation: slow growth while cells adapt to new environment
* II: Exponential growth: growth rate proportional to cell mass
* III: Slow growth as substrate or other factors begin to limit rate
* IV: Stationary phase: cell growth rate and death rate are equal
* V: Decline phase: cells die or sporulate, often caused by product build-up

Intracellular product accumulation is slow at first because there are a limited number of cells (Towler, 2012). However, it is important to note that product accumulation continue even after the live cell count falls, since dead cells still contain product.

The growth rate of cells can be limited by factors such as:
* The availability of the primary subtrate
** Typically glucose, fructose, sucrose, or other carbohydrate
* The availability of other metabolites
** Vitamins, minerals, hormones, or enzyme cofactors
* The availability of oxygen
* Mass transfer properties of the reaction system
* Inhibition or poisoning by products or byproducts
* High temperature caused by inadequate heat removal

All of these factors are exacerbated at higher cell concentrations (Towler, 2012). Clearly, biological reactions must be carefully controlled. An addition complication in dealing with biological reactions is that the product formation is often not closedly tied to the rate of consumption of the substrate (Towler, 2012). This is because of the fact that the product may be made by the cells at a relatively low concentration and the fact that some cell metabolic processes may not be involved in formation of the desired product (Towler, 2012).

===Types of Bioreactors===

* '''Stirred Tank Fermenter'''

:: The stirred tank fermenter is the most common reactor used for biological reactions (Towler, 2012) and is similar to the stirred tanks discussed previously. It can be used in both batch and continuous mode. Figure 14 shows a stirred tank fermenter.

::[[File:Fermentation.png]]

::''Figure 14.'' Fermentation reactor (Towler and Sinnott, 2013)

* '''Shaftless Bioreactors'''

:: Shaftless bioreactors are used when the pump shaft seal is considered a non-permissible source of contamination. These reactors use gas flow to provide agitation of the liquid. The design requires careful attention to hydraulics (Towler, 2012). Examples of shaftless bioreactors are shown in Figure 15.

::[[File:Shaftless.png]]

::''Figure 15.'' Examples of shaftless bioreactors (Towler, 2012)

=Heating and Cooling of Reacting Systems=

Exothermic and endothermic reactions will require reactors with heat control systems to prevent operating conditions from falling out of the desired range. Reactor performance is often limited by the ability to add or remove heat. Insufficient heat removal can cause runaway reactions, particularly dangerous situations in chemical processing (Turton et al., 2012). Before considering the design of a heating or cooling system to couple with a reactor, a few important questions should be asked (Towler and Sinnott, 2013).

1. Can the reaction be carried out adiabatically?

2. Can the feeds provide the required heating or cooling? Staged addition of feed can help alleviate the cost of adding a heat exchange network or heat transfer jacket. Also consider adding an inert diluent or hot/cold shots (Seider et al., 2004).

3. Would it be more cost effective to carry out the heat exchange outside of the reactor?

4. Would it be more effective to carry out the reaction inside of a heat transfer device? If a reaction requires only a small volume or small quantities of catalyst, it may be possible to utilize a heat exchanger as a temperature controller and as a reaction location.

5. Does the proposed design allow the process to be started up and shut down smoothly?

6. Are there safety concerns with heating or cooling the reactor?

After considering these aspects of the design, commercial design software such as HYSYS or UniSim can be utilized to estimate heating/cooling requirements. Once this is done, design of the heat exchange system can begin, with different reactor types and reactions requiring different design approaches (Towler and Sinnott, 2013).

==Stirred Tank Reactors==

Heating and cooling of a stirred tank reactor is done to ensure a uniform reaction temperature, so that there do not exist hot or cold spots within the reactor that can negatively affect selectivity (Towler and Sinnott, 2013).

For indirect heat transfer, there are three main alternatives: a heat transfer jacket, an internal coil, and an external heat transfer circuit. A jacket is utilized as long as there is sufficient heat transfer area for the heat exchange to take place. If this is not the case, coils are used, although the inclusion of a heating coil will significantly increase reactor volume and utility requirements, leading to a large increase in price for the reactor. External circuits contain a heat exchanger that will heat or cool the product stream as required and recycle this material to the reactor to control temperature. External circuits are useful because they can be designed independently of the reactor; sizing the required pumps and heat exchangers will not fundamentally change the activity of the reactor. For any of these choices, it should be ensure that no corrosion of the involved piping will occur, as utility streams bleeding into the reactor can have a very negative impact on the selectivity of the reaction and on the operation of the reactor on a whole (Towler and Sinnott, 2013).

Some direct heat transfer alternatives also exist, as long the reaction in question is compatible with the addition of extra water. Steam can be pumped into the reactor to maintain temperature, which will eliminate the need to design heat transfer surfaces. However, steam injected into the system cannot be recovered, so this will lead to an increase in annual utility costs. Additionally, vapor will be produced if it did not exist previously, so reactors will need to be redesigned to accommodate a vapor removal system (Towler and Sinnott, 2013).

==Catalytic Reactors==

===Slurry Reactors===

Since slurry reactors already use a mix of solid catalyst and liquid reactants, any of the methods described in the Stirred Tank Reactors section can be applied to slurry reactors. It is not recommended to use internal coils in such a design, as reactor slurry will often corrode heat exchange material very easily (Towler and Sinnott, 2013).

===Fixed-bed Reactors===

Indirect heat transfer is not often utilized to control the temperature in fixed-bed reactors, as it hard to maintain uniform temperature across the radial section of the catalyst bed. In cases where temperature control is required, the reactor will be split into smaller sections. After each bed, there will be an heat transfer stage, where the product stream is heated or cooled as necessary and returned to the next catalytic segment (Towler and Sinnott, 2013).

===Fluidized-bed Reactors===

Fluidized bed reactors have high heat-transfer coefficients, so indirect heat transfer is highly effective. The heat capacity of the solid catalyst particles can be used as a heat transfer medium themselves; heated catalyst contains a reaction location and the necessary heat to maintain the required temperature. Deactivated catalyst is heated during reactivation and recycle (Towler and Sinnott, 2013).

==Heat Exchangers as Reactors==

It is sometimes necessary to design a reactor as a heat transfer device, like when it is necessary to operate a reactor isothermally and there is a large heat of reaction. Some common situations include high-temperature endothermic reactions that quickly quench without continuous heat input and low-temperature exothermic reactions that must be kept at constant temperature to maintain selectivity. The most common heat transfer equipment used for reactions are shell and tube heat exchangers and fired heaters (Towler and Sinnott, 2013).

===Homogenous Reactions===

If the reaction does not required a catalyst, than the heat transfer design is the same as a conventional heat transfer device, with some important changes in the thermal design. The usual heat exchanger equations will not apply to the design of a heat exchanger reactor due to the nonlinear behavior of the reaction rate with regards to temperature. In these cases, the usual practice of conservative temperature estimations will not aid in heat transfer design, as greater detail will be required to ensure the proper operation of the reactor. Detailed kinetic models should be developed before designing the internals of the heat transfer device (Towler and Sinnott, 2013).

===Heterogenous Reactions===

The problems of designing for homogenous reactions still hold for heterogenous ones, with the added complication of solid catalyst beds. Catalyst can be loaded into the tubes of a shell and tube exchanger if the exchanger is mounted vertically and a suitable retaining screen is included at either end of the design. In this instance, hot catalyst can be reliably recycled and heat treated to reactivate the catalysts and reduce the presence of reactor hot spots. High-temperature endothermic reactions will be even more difficult to design for, as their heat requirements often exceed the amount provided by a heated catalyst. In these cases, a "tube in tube" design is utilized, where feed and catalyst are heated simultaneously by an external fired heater. This can be done as long as thermal expansion does not cause damage to the tubes, or else significant catalyst poisoning can occur. The same concerns as detailed in homogenous reactions will still apply for any design utilized for heterogenous ones, so it is again recommended to develop a detailed kinetic model before determining the amount of heat transfer required to maintain proper selectivity (Towler and Sinnott, 2013).

=Safety Considerations in Reactor Design=

Reactors require much attention to safety details in the design process due to the hazards they impose. They are often the highest temperature point in the process, heat of reaction may be released, and residence times can be long leading to a large inventory of chemicals. Guidelines exist for inherently safer design principles which seek to remove or reduce process hazards, limiting the impact of unforeseen events. These design methods should be applied throughout the design process as part of good engineering practice; they cannot be retroactively added by a process safety specialist. Some examples are given in the table below:

[[File:Some applications of inherently safer design approaches in reactor design_part1.png|850px|]]

[[File:Some applications of inherently safer design approaches in reactor design_part2.png|850px|]]

Some Applications of Inherently Safer Design Approaches in Reactor Design (Towler and Sinnott, 2013)

Exothermic reactions require special consideration due to their potential to runaway (temperature rises from heat of reaction being released, increasing reaction rate, releasing more heat, and so on). The reactor must be designed such that temperature can be precisely controlled and the reaction shut down if temperature control is lost. The use of solvents or inert species also allows for temperature control by adjusting heat capacity flow rate relative to rate of heat release from the reaction. An additional safety feature would allow the reactor to be flooded with cold solvent or diluent.

If there is a cooling system it should be designed to return the process to desired temperature if the maximum temperature is reached.

Venting and relief of reactors is complicated by the potential to keep reacting if containment is lost or material is discharged into the pressure relief system. The relief system should be designed according to guidelines outlined in the Design Institute for Emergency Relief Systems (DIERS) methodology. The reactor design team must understand the reaction mechanism and kinetics, including the role of any compounds which may accelerate the reaction. Details may be found on the AIChE website, [http://www.aiche.org/diers here].

=Capital Cost of Reactors=

Reactors are classified as pressure vessels, and as such the pressure vessel design methods can be used to estimate wall thickness and thus determine capital cost. Additional costs come from reactor internals or other equipment. Jacketed stirred-tank reactors require more in depth analysis than that provided by pressure vessel design. The wall of the reaction vessel may be in compression due to the jacket. For preliminary cost estimating a correlation for jacketed stirred tank reactors operating at pressures below 20 bar can be used:

<math>C_e = a + b S^n</math>

where <math>C_e</math> is the purchased equipment cost on a U.S. Gulf Coast Basis, <math>a, b</math> are cost constants, <math>S</math> is the size parameter, and <math>n</math> is the exponent for that type of equipment. Values for <math>a, b, S, n</math> are given in the table below:

[[File:Purchased equipment cost_part1.png|850px|]]

[[File:Purchased equipment cost_part2.png|850px|]]

[[File:Purchased equipment cost_part3.png|850px|]]

Purchased Equipment Cost Factors (Towler and Sinnott, 2013)

=Conclusions=

The conversion of feed to products is the essence of a chemical process and, thus, the reactor is the heart of a chemical plant. When designing a reactor, an engineer must first collect data about the chemical reaction and then select appropriate reaction conditions, which will help determine suitable materials of construction. Next, the designer should determine the rate-limiting step and, from this, the critical sizing parameter. Next, preliminary sizing, layout, and costing can be conducted for the reactor. At this point, simulations and experiments can be conducted to verify that the proposed reactor will meet the desired specifications. The design is optimized until these targets are met. Throughout the design process, it is important for the engineer to consider the most appropriate type of reactor to use, any mixing or heat transfer equipment that must be added, and safety considerations.

=References=

Douglas JM. Conceptual Design of Chemical Processes. New York: McGraw-Hill; 1988.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G. Chemical Engineering Design. PowerPoint presentation; 2012.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Process hydraulics

2015-03-02T04:21:37Z

Jian: /* References */

Authors: Thomas Considine, Sean Kelton, Michael Gleeson

Steward: David Chen, Fengqi You

Date Presented: Feb. 2, 2014

==Introduction==

The transportation and storage of fluids is essential to a chemical process plant. Piping, valves, pumps and compressors comprise the major components of fluid handling equipment. The goal of process hydraulics in a design setting is to overcome frictional losses in piping and equipment, provide correct operating conditions, and overall assist in the controls of the plant. All three objectives must be designed in concert, and before the final controls system is designed (Towler and Sinnott, 2012).

==Hydraulic systems & Pressure drop==

Overall pressure drops created by pumps and compressors must also include those created by the connecting pipes. These components must be designed in concert, to account for changes in elevation and friction losses in the pipe.

===Total Pressure Drop===

Pressure drops throughout the flow of a fluid can be summed to find the overall pressure drop of a defined system. For example: If a fluid A, initially at zero gauge pressure, is pumped to a pressure of 300 kPa, then flows through 10 meters of pipe resulting in a loss of 50 kPa, the final gauge pressure at the end of the pipe is 250 kPa. This type of analysis is useful when designing pressure systems over many components.

<math>Total Pressure Drop = \sum_i \Delta P_i = +300 kPa - 50 kPa = 250 kPa</math>

===Pressure Drop in Pipes===

When designing pumps and compressors, the loss of pressure due to piping is not negligible, and must be appropriately accounted for (Turton et al., 2003). The <math>\Delta P</math> across a pipe is calculated as follows:

<math>P = (4*c*L/d)*(rho*v^2/2)</math>

where <math>c</math>, is the specific coefficient (typically 0.005 for turbulent flows)
<math>L</math> is the length of piping,
<math>d</math> is the diameter of piping,
<math>rho</math> is the density of the fluid, and
<math>v</math> is the velocity of the fluid.

An added term accounting for the pressure difference due to height is also necessary if there is a change in elevation.

Additionally, the first term in the equation can be altered to include an additional factor:

<math>(n + 4*c*L/d)</math>

where <math>n</math> is an empirical value to account for piping bends, restrictions, and other variables.

===Heuristics===

Both the process hydraulics and the economics of a system is affected by pipe sizing (Peters and Timmerhaus, 2003). Heuristics, or "Rules-of-thumbs" have been developed to assist in optimizing pipe selection. While more detailed optimization techniques are available and commonly used, the rules of thumb provide a good starting point for pipe selection.

Suggested pipe velocities, in ft/s, for gases, liquids, and super-heated steam are approximately 60-100, 6, and 150, respectively (Towler and Sinnott, 2012). Additionally, for liquid flow, the following equation provides a rule-of-thumb for optimal pipe diameter, in inches:

<math>D = \sqrt{Flow/10}</math>

Where D is the optimal diameter, and Flow is in units of gallons/minute.

==Pumps & Compressors==
Pumps and Compressors are used to pressurize liquids and gases, respectively, and to transfer them from one location to another. In general, it is preferable to increase the pressure of a stream by pumping a liquid rather than compressing a gas because it is far less expensive. This is because the power needed to increase the pressure of a stream is:

<math>W = \int\limits_{P_1}^{P_2} V\, dP</math>

where V is the volumetric flow rate. Generally, the volumetric flow rate of a liquid is approximately two orders of magnitude less than the volumetric flow rate of a gas, which means a 10hp pump is comparable in fluid pressurizing capacity to a 1000hp compressor. (Seider et al., 2004).

===Pumps===
As stated above, pumps require relatively little power compared to gas compressors. However, they are easily vapor locked when pumping liquids near the bubble point because small amounts of vapor can become trapped within their rotating blades. Pumps increase the pressure energy of the effluent fluid by the transfer of kinetic energy from the motor to the fluid, through the impeller (Seider et al., 2004). Selection of pumps for specific services requires knowledge of the liquid to be handled, the total dynamic head required, the suction and discharge heads, and in most cases, the temperature, viscosity, vapor pressure, and density of the fluid. The different types of pumps used in industry can be classified as centrifugal pumps, positive displacement pumps, jet pumps, and electromagnetic pumps (Peters and Timmerhaus, 2003).

====Centrifugal Pumps====
This type of pumps is the most widely used in industry. They range in capacity from .5 to 20,000 meters cubed per hour. In the centrifugal pump, the fluid enters the pump are the center of a rotating impeller, where it is thrown outward by centrifugal force. The fluid at the edge of the impeller gains a high kinetic energy, which is then converted into pressure energy, which supplies the pressure difference between the suction side and the delivery side of the pump (Peters and Timmerhaus, 2003).

[[File:centrifugal pump.jpg|300px]]

Figure 1: Example Centrifugal Pump (Enggcyclopedia.com)

====Positive Displacement Pumps====
In positive displacement pumps, a fixed volume is alternately filled and emptied of the pump fluid by action of the pump. In general, overall efficiencies of positive displacement pumps are higher than those of centrifugal pumps because internal losses are minimized. However, the range of capacities that these pumps can handle is somewhat limited. There are two classes of positive displacement pump, reciprocating and rotary. Reciprocating pumps use valves that are operated by pressure difference to introduce and discharge the liquid being pumped. They generally can deliver fluids with high efficiency against high pressure. In rotary pumps, two intermeshing gears are fitted into a casing. Fluids becomes trapped between the teeth of the gears and is transported to the discharge side of the pump (Peters and Timmerhaus, 2003).

[[File:reciprocating piston pump.jpg|300px]]

Figure 2: Example Positive Displacement Pump (Marineengineeringonline.com)

====Jet Pumps====
Jet pumps use the momentum of one fluid to transport the desired fluid. Efficiency of jet pumps is generally low, and these are mainly useful for situations in which the head to be attained is low and less than the head of the fluid used from pumping (Peters and Timmerhaus, 2003).

====Electromagnetic Pumps====
Electromagnetic pumps use the principle that a conductor in a magnetic field, carrying a current that flows at right angles to the field, has a force exerted on it. These pumps are used to move fluids that exhibit electromagnetic properties (Peters and Timmerhaus, 2003).

===Compressors===
Gas compressors are designed to increase the pressure of gases. Even small amounts of liquids can cause significant amounts of degradation to the compressor blades, so most compressors are designed to avoid condensation. Like pumps, the feed enters the eye of the impeller unit. Compressors are generally much larger than pumps, and they are well insulated to facilitate operation on light gases. To avoid excessively high temperatures, individual compressors are designed to operate at small compressor ratios <math>P_2/P_1</math>, typically less than 5. If the compression ratio is greater than 5, multistage compressors are used. (Seider et al., 2004). Compressors are generally classified into two major categories; continuous flow compressors and positive displacement compressors.

====Continuous Flow Compressors====
Centrifugal and Axial Compressors are the two main types of continuous flow compressors. Centrifugal compressors are used for higher pressure ratios and lower flow rates, while axial compressors are used for lower stage pressure ratios and high flow rates. The pressure ratio of a single stage centrifugal compressor is roughly 1.2:1, while the pressure ratio of axial flow compressors is between 1.05:1 and 1.15:1. Because of the low pressure ratios for each stage, a single compressor may include a number of stages in one casing to achieve the desired overall pressure ratio (Peters and Timmerhaus, 2003).

[[file:compressor.jpg|300px]]

Figure 3: Example Continuous Flow Compressor (Spakovszky)

====Positive Displacement Compressors====
These units are essentially volume gas movers with variable discharge pressures. They operate in much the same way as positive displacement pumps (Peters and Timmerhaus, 2003).

===Economics of Pumps and Compressors===
Pumps are relatively cheap in terms of processing equipment. In 1997 dollars, they would cost between $390 and $1500 base cost multiplied by a ~2.38 (because pumps usually cost much less than $200,000) factor for the installation costs. Therefore their total installed costs today is $1000-$3500 multiplied by some time correction factor to account for inflation. For this reason it is typically preferable to condense a vapor to liquid, pump up the liquid, then evaporate the liquid, rather than compress a gas (Biegler et al., 1997).

Compressors are one of the most expensive pieces of process equipment. In 1997 dollars they cost about $23,000 as a base cost multiplied by a ~3.11 (because compressors are typically less than $200,000) factor to account for installation costs. Therefore their total installed cost today is ~$71,500 multiplied by a correction factor to account for the inflation over time; nearly 70 times as expensive as a pump! For this reason in industry compressing a gas within your process is avoided if at all possible (Biegler et al., 1997).

==Valves==
A valve is a mechanical tool used to control the flow of material in a system by blocking or restricting the materials flow path; typically used on piping. Valves serve many purposes including but not limited to: beginning or quenching the flow of a material through a system, regulating the flow rate of the material traveling through a system, regulating the pressure of a material flowing through a system, prevent back-flow of a material and changing the flow direction at intersection points. Any valve in a piping system will cause a pressure drop. As a rule of thumb, 10 psi change in pressure should be accounted for across each valve when designing a plant (Towler and Sinnott, 2012).

More specifically, the table below gives the pressure drop of different types of valves in the number of velocity heads lost.

Table 1: Pressure Drops Across Valves (Cole, 2013).
{| class="wikitable"
|-
!Valve or Fitting Type
!No. Velocity Heads, n
!Valve or Fitting Type
!No. Velocity Heads, n
|-
|45 degree ell, standard
|0.35
|Globe valve, bevel seat, open
|6
|-
|90 degree ell, standard
|0.75
|Globe valve, bevel seat, ½ open
|9.5
|-
|180 degree bend, close return
|1.5
|Globe valve, plug disk, open
|9
|-
|Tee, along run, branch blanked off
|0.4
|Globe valve, plug disk, ¾ open
|13
|-
|Tee, entering run or entering branch
|1
|Globe valve, plug disk, ½ open
|36
|-
|Tee, branching flow
|1
|Globe valve, plug disk, ¼ open
|112
|-
|Gate valve, open
|0.17
|Plug valve, 5 degrees open
|0.05
|-
|Gate valve, ¾ open
|0.9
|Plug valve, 20 degrees open
|1.56
|-
|Gate valve, ½ open
|4.5
|Plug valve, 40 degrees open
|17.3
|-
|Gate valve, ¼ open
|24
|Plug valve, 60 degrees open
|206
|-
|Check valve, swing
|2
|Pipe union
|0.04
|}

=== Gate Valve ===
A gate valve is comprised of a wedge that slides up and down perpendicular to the path of fluid flow on screw type mechanism, which spins in opposite directions to open/close the valve, in order to allow and block fluid flow respectively. This type of valve is an ON/OFF valve and therefore should either be operated fully open or fully closed. Operating partially open can degrade the seal on the valve. The fluid path is straight through the valve and therefore minimal pressure drop results (Towler and Sinnott, 2012).

[[File:Example.jpg|center|frame|Figure 1. Gate Valve Example (Cole, 2013).]]

===Ball Valve===
A ball valve is another type of ON/OFF valve that only operates fully opened or closed with the flow path straight through the valve. However, these valves only require a quarter turn to open or close the valve and therefore can quench flow much faster than a gate valve. Rather than blocking flow with a wedge, a ball valve turns so that the opening aligns with the pipe to allow flow or pipe wall to block flow (Towler and Sinnott, 2012).

[[File:Example3.jpg|center|frame|Figure 2. Ball Valve Example (Cole, 2013).]]

===Butterfly Valve===
A butterfly valve also requires only a quarter turn to switch between the open and closed position. A flat plate switches positions between being parallel or perpendicular to flow in order to allow or prevent flow through the valve respectively. This valve does not seal well on its own and, unaided, can be pushed open by fluid flow, therefore extra materials are required for complete shutdown of flow (Towler and Sinnott, 2012).

[[File:Example4.jpg|center|frame|Figure 3. Butterfly Valve Example (Cole, 2013).]]

===Plug Valve===
A plug valve is very similar to a ball valve, except it is used in situations in which a better seal is needed. The valve uses plug stationed in lubricated lining to provide the seal and once again a quarter turn will open/close the valve by aligning the hole within the plug to the pipe/wall respectively. There is an upper limit to the temperature a which a plug valve can be used, ~450 F, because after this point heat expansion differences of the liner and plug ruins the seal (Towler and Sinnott, 2012).

[[File:Example5.jpg|center|frame|Figure 4. Plug Valve Example (Cole, 2013).]]

===Globe Valve===
A globe valve is a type of throttling valve, controlling the fluid flow rate, in which the height of a disk is adjusted between two vertical plates. The gap between the disk and the second vertical plate, known as the seat, can be adjusted to regulate flow rate, however, the valve should not be run at very slow flow rates (<10% open) because the flowing fluid will cause damage to the seat. The two vertical directional changes of the fluid flow path cause greater pressure drops across these valves. This type of valve can be adjusted automatically (using a machine program) or manually by a worker (Towler and Sinnott, 2012).

[[File:Example6.jpg|center|frame|Figure 5. Globe Valve Example (Cole, 2013).]]

===Needle Valve===
A needle valve is much like a globe valve, however, a stem with a conical head is used to control the flow rate. The conical head provides a more accurate and precise flow rate control. Additionally, the conical head does not have problems at low flow rates as the flat disk of a globe valve exhibits (Towler and Sinnott, 2012).

[[File:Example7.jpg|center|frame|Figure 6. Needle Valve Example (Cole, 2013).]]

===Control Valve===
Control valves are a classification of automatic globe valves. These valves use an electric actuator or some type of compressed air system to adjust the flow rate through the valve via signaling from an electric control program (Towler and Sinnott, 2012).

[[File:Example8.png|300x300px|center|frame|Figure 7. Control Valve Example (Cole, 2013).]]

===Check Valve===
Check valves are valves that are used to control the flow direction within the pipe (i.e. prevent back-flow). The three main types are swing valves, lift valves and wafer valves (respectively below). Swing valves push a swinging mechanism forward to allow forward flow, but is blocked in the other direction because the weight of the disc holds itself in place. These valves are most common in industry. These valves are not good when flow rate pulsates or is very high, nor if the fluid is a slurry or a gas. Lift valves use vertical plates, as in a throttling valve, to divert flow in an upward direction to lift a move-able piece that is otherwise held in place by gravity preventing reverse flow. Wafer valves use a circular wafer that can only twist in one direction so that forward flow in the pipe spins the wafer to align with the fluid flow and move forward, however, in the reverse direction the hinge is blocked so the wafer can not spin allow flow. These valves require a smaller pressure drop to open and are generally cheaper however they must be used in a very strict flow rate range (~3-11 ft/s) (Towler and Sinnott, 2012).

<center>
{|
|[[File:Example9.png|center|frame|Figure 8. Swing Check Valve Example (Cole, 2013).]]
|
|[[File:Example10.png|200x200px|center|frame|Figure 9. Lift Check Valve Example (Cole, 2013).]]
|
|[[File:Example11.png|200x200px|center|frame|Figure 10. Wafer Check Valve Example (Cole, 2013).]]
|}</center>

==Conclusion==

The transportation and storage of fluids is a key variable in the design and optimization of a chemical process facility. The major components involved in this step of process design are the piping, valves, pumps and compressors. Process hydraulics design aims to overcome frictional losses in piping and equipment, provide correct operating conditions, and overall assist in the controls of the plant. These three objectives must be designed in concert, as together they effect many variables within both the chemistry, engineering, and economics of the plant.

==References==

Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Cole JL. Chemical Engineering 351 Process Economics, Design, and Evaluation [Lecture Slides]. Evanston: Northwestern University; 2013.

Enggcyclopedia.com. Pumps [Internet]. [cited 2015 February 24]. Available from: http://www.enggcyclopedia.com/2011/05/pumps/.

Marineengineeringonline.com. Reciprocating Positive Displacement Pump with Air Vessel [Internet]. [cited 2015 February 24]. Available from: http://marineengineeringonline.com/reciprocating-positive-displacement-pumps/.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Spakovszky ZS. 12.4 Multistage Axial Compressors [Internet]. [cited 2015 February 24]. Available from: 2014.http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node92.html.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Pressure Vessels

2015-03-02T04:20:49Z

Jian: /* References */

Title: Pressure Vessels

Author: David Chen

Steward: Fengqi You

Date Presented: January 13, 2014 /Date Revised: January 14, 2014

 


__TOC__

=Introduction=
[[File:Pressure Vessel.png|thumb|right|300px|Example of a pressure vessel.]]
Codes for pressure vessels can be found in the ASME Boiler and Pressure Vessel Code (ASME BPV code). While there is no formal definition, generally any closed vessel over 150 mm in diameter and that will experience a pressure difference of greater than 0.5 bar can be classified as pressure vessels. Types of equipment that can fit these descriptions include many reactors, separation columns, flash drums, heat exchangers, surge tanks, and storage vessels. Pressure vessels with a wall-thickness:diameter ratio of less than 1:10 can be classified as thin-walled, and the rest, thick-walled (Towler and Sinnott, 2013). Pressure vessels typically consist of a cylindrical shell and elliptical or hemispherical heads at the ends (Peters and Timmerhaus, 2003). Generally, chemical engineers will not be directly involved in detailed mechanical design of pressure vessels. This will be handled by mechanical engineers with experience in the field. However, chemical engineers will need to understand basic concepts of pressure vessel design in order to estimate costs and communicate specifications to those who will carry out the design. Most correlations for estimating cost depend heavily on the weight and type of material used. (Peters and Timmerhaus, 2003;Towler and Sinnott, 2013).

Basic data required by pressure vessel design engineer. It will be important for chemical engineer and vessel design engineer to communicate very closely (Towler and Sinnott, 2013):

1. Vessel function

2. Process materials and services (corrosion, deposits, etc.)

3. Operating conditions (temperature and pressure)

4. Materials of construction

5. Dimensions and orientation

6. Type of vessel heads to be used

7. Openings and connections required

8. Heating/cooling requirements

9. Agitation requirements

10. Specification of internal fittings

=Designs and Codes=
Many countries have codes and standards concerning pressure vessels. Compliance is usually legally required. The codes provide guidance on design, materials of construction, fabrication, inspection, and testing. In North America, the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPV Code) is used. There are twelve sections, and section VIII has three subdivisions. The section titles are listed below. Other sets of codes exist for storage tanks, fittings, and piping. It is important to always use the most recent revisions in design (Towler and Sinnott, 2013).

TABLE "American Society of Mechanical Engineers Boiler and Pressure Vessel Design Codes"

I Rules for construction of power boilers

II Materials

III Nuclear power plant components

IV Rules for construction of heating boilers

V Nondestructive examination

VI Recommended rules for the care and operation of heating boilers

VII Recommended guidelines for the care of power boilers

VIII Rules for the construction of pressure vessels

VIII. D1

VIII. D2 Alternative rules

VIII. D3 Alternative rules for the construction of high pressure vessels

IX Welding and brazing qualifications

X Fiber-reinforced plastic vessels

XI Rules for in service inspection of nuclear
power plant components

XII Rules for construction and continued service of transport tanks

=Design Temperature=
Different temperature allowances are used above and below normal operating tempratures. For temperatures between -30 and 345 ⁰C, Turton gives a maximum allowance of 25 ⁰C above maximum operating temperature should be included (Turton et al., 2012). Above this, an even higher design allowance is used (Towler and Sinnott, 2013). Towler/UOP gives 50 ⁰F above the maximum operating temperature and -25 ⁰F below the minimum (Towler and Sinnott, 2013).

Maximum allowable stress is highly dependent on temperature, because metals weaken with increasing temperature. The vessel should not operate at higher temperature than the highest at which the maximum allowable stress was evaluated.

There is also a minimum temperature for which the vessel can be guaranteed to operate safely. Metals may become brittle at very low temperatures (Towler and Sinnott, 2013).The minimum design metla temperaure (MDMT) is the lowest temperature that can be expected in the vessel (Towler and Sinnott, 2013).

In specifying the maximum and minimum temperatures, disturbances caused by upstream processes and external factors need to be taken into account. These disturbances may include:transient conditions, upsets, auto-refrigeration, climate, other cooling factors (Towler and Sinnott, 2013).

=Design Pressure=
Vessels are often overdesigned relative to the maximum operating pressure. Turton suggests deisgn pressures of either 10% or 0.69-1/7 bar above the maximum operating pressure, whichever is greater. The maximum operating pressure is taken a 1.7 bar above normal operation. for example, the design pressure of a vessel that normall operates at 0-0.69 bar and 95-540 ⁰C is 2.76 barg (Turton et al., 2012). Towler suggests overdesign of vessel pressures by 5-10%.

For vessels that will experience external pressure, design pressure is based on the maximum difference between internal and external pressure.
[[File:Vacuum Collapse.jpg|thumb|right|300px|Collapse of railroad tank car due to steam condensation caused by cold external temperatures. The relief valve allowed vapor to vent outwards, but there was no vacuum relief.]]
Vessels that may potentially experience vacuum conditions must be designed to resist a negative pressure of one full atmosphere. Because of the large surface areas of some vessels, even a modest vacuum can lead to collapse. Circumstances that may lead to vacuum conditions include: startup/shutdown procedures, cooling vessels with condensable vapors, pumping or draining without proper venting, or some other unexpected disturbance (Towler and Sinnott, 2013).

=Design Loads=

Pressure vessels and the structures used to support them must be able to resist deformation and collapse when subjected to various loads, classified into major and subsidiary loads. Major loads must always be considered in the design of a pressure vessel, while subsidiary loads only need to be subjected to formal stress analysis when there is no other way to show that they can be supported. Subsidiary loads can often be evaluated by comparison with existing vessels.

Loads classified as major loads include design pressure, taking into account pressure heads; maximum operational weight, maximum weight under testing, wind, earthquake, and loads supported by the vessel.

Loads classified as subsidiary loads include: local stresses caused by supports, internal structures, and connecting pipes, shock loads caused by water hammer or surging, bending moments due to displacement of center of pressure, loads caused by differences in temperature and thermal expansion coefficients, and those caused by fluctuations of temperature and pressure.

The “worst case scenario” should be considered, and that the design should be based around that loading.

=Maximum Allowable Stress=
The maximum allowable stress is obtained by applying a safety factor to the maximum stress that the material can withstand under standard testing conditions. This allows for possible deviations from ideal material properties and ideal vessel construction.

The ASME BPV Code Section II Part D, Mandatory Appendix 1 details methods on obtaining maximum allowable stress. It is different depending on whether creep and stress rupture are dominant among the various stresses that are present.

=Materials=
Steel is the most common material used in construction of tanks and pressure vessels. Other construction materials include other alloys, wood, concrete, or fiber-reinforced plastics (some low-pressure applications).

Materials must be chosen that will be able to resist deformation and failure at the process temperature and pressure, and be compatible with the internal material. (Peters and Timmerhaus, 2003;Towler and Sinnott, 2013). Other factors for selection include ease of fabrication, availability of parts, and cost (Towler and Sinnott, 2013).

=Wall Thickness=
The required wall thickness of a vessel will depend on many factors, including: the strength of the metal at operating conditions (temperature and pressure), diameter of the tank, and the joint efficiencies. According to Peters, in "Plant Design and Economics for Chemical Engineers," minimum wall thickness, not including corrosion allowances, should not be less than 2.4mm for welded or brazed construction and 4.8mm for riveted construction. Thickness for unfired steam boilers should not be less than 6.35 mm. (Peters and Timmerhaus, 2003) Turton gives heuristics for wall thickness for rigidity based on vessel diameter: 4 mm (0.25 in) for 1.07 m (42 in) diameter and less than 8.1mm (0.32 in) for 1.07-1.52 m (42-60 in) diameter, and 11.7 mm (0.38 mm) for more than 1.52 m (60 in) diameter (Turton et al., 2012).

ASME BPV Code Section VIII D.1 states that wall thickness should always be at least 1/16 in, not considering corrosion allowance, material, or dimensions.

Minimum wall thicknesses do not include corrosion allowances. (11-13)

=Corrosion Allowances=

In general, corrosion allowances will range from 1.5-5mm. Corrosion allowances for heat transfer equipment are smaller, because wall thickness has an important effect on heat transfer (Towler and Sinnott, 2013).

Corrosion and erosion will lead to eventual thinning of walls, which compromises mechanical integrity. Corrosion allowance is constructing the vessels with thicker walls to allow for the thinning. the
Peters, Timmerhaus, and West suggest 0.25 to 0.38mm annually or 3mm for 10 years.

Turton et al.(2012) suggest a corrosion allowance 8.9 mm (0.35 in) for known corrosive conditions, 3.8 mm (0.15 in) for noncorrosive streams, and 1.5 mm (0.6 in) for stream drums and air receivers.

In cases where corrosion is negligible over the lifetime of a vessel or does not occur, the vessel can be designed without the corrosion allowance (Towler and Sinnott, 2013).

=Construction=
Most pressure vessels are cylindrical (swaged vessels are an exception) and have integer length:diameter ratios (2:1, 3:1, 4:1). Vertical vessels are more commonly used than horizontal ones. This is because it is easier to have uniform distribution across the cross section, and they take up less space. However, there may be cases in which horizontal vessels may be preferable. They can be used to promote phase separation (in decanters, settling tanks, separators, and flash vessels), and to allow easy access to clean the inside (in heat exchangers).

==Fabrication==
In general, vessel shells are made by rolling and welding. It is easier for thin walls, however there may still be difficulty for small diameters. Vessels with thicker walls may need to be drum forged. The end closures are usually forged, and auxiliary components such as nozzles and support rings are welded on. Post weld heat treating (PWHT) is used to relieve residual stresses caused by forming and joining.

==End Closures==
[[File:End Caps.JPG|thumb|right|300px|Different geometries of end caps: a) hemispherical b) ellipsoidal c) torispherical]]
The heads on the ends of the vessels can be hemispherical, ellipsoidal, or torispherical.
Hemispherical heads have greater internal volumes than ellipsoidal heads, which have greater internal volumes than torispherical heads. The internal volumes are correlated with the cost of each type of head.
Tangent and weld lines usually are not the same. Tangent lines are where the curvature ends. Weld lines are where the closures are attached.
Different kinds of welds can be used. ASME BPV Code has guidelines concerning weld types and inspection.

Gasketed joints can be used then vessels need to be frequently opened, and for instrument connections. However, they are not used at high temperature or pressures because they may fail, and welds are stronger. They are also more prone to leaks than welded joints (Towler and Sinnott, 2013).

==Supports==
Different saddles will be used depending on a variety of factors. These factors include vessel dimensions and weight, temperature and pressure, arrangement, and fittings and attachments.
Saddles are usually used for horizontal vessels. Skirt supports – vertical columns. Brackets – all types of vessels.

==Welded Joints==
The ASME BPV Code Section VIII D.1 defines four kinds of welds and criteria for their evaluation (Towler and Sinnott, 2013).

A. Longitudinal or spiral welds in the main shell, necks, or nozzles, or circumferential welds connecting hemispherical head sto the main shell, necks or nozzles

B. Circumferential welds int he main shell, necks, or nozzles or connecting a formed head other than hemispherical

C. Welds connecting flanges, tubesheets, or flat heads to the main shell, a formed head, neck or nozzle

D. Welds connecting communicating

==High Pressure Vessels==
High pressures are often required to carry out chemical processes. Section VIII Division 2 of the ASME BPV Code provides guidelines for pressure vessels that will experience pressures above 2000 psia. There are stricter restrictions and requirements regarding operating temperatures and stress analysis and testing. Divison 3 of Section 8 provides guidelines for pressures above 10,000 psia (680 bar).

At high pressures, compound vessels are often used instead of single-walled vessels, which may have difficulty providing the necessary strength (Towler and Sinnott, 2013).

===Shrink-fitted cylinders===
[[File:Shrink fit.PNG|thumb|right|300px|Diagram of shrink-fitted cylinders. The inner cylinder is under compression by the outer cylinder.]]
One way of creating compound vessels is to use multiple cylinders such that the outer diameter of the inner cylinder is larger than the inner diameter of the outer one. The outer cylinder can be expanded by heating, and compresses the inner cylinder when cooled. Multiple cylinders may be used.

===Multilayer cylinders===
Multilayer cylinders are made by wrapping thin plates around a tube in layers. They are heated, tightened, and welded.

===Wound vessels===
[[File:Wound Vessel.jpg|thumb|right|300px|Fibreglass wound underground vessel from ZCL Composites.]]
Wound vessels are cylindrical vessels reinforced by winding on wire or thin ribbons under tension. The strips can be interlocked to provide more strength for high-pressure applications.

===Autofrettage===
The internal surface of the vessel is subject to enormous pressures to prestress it. When released, the inside will be under compression by the outside. The vessel can be used up to the “autofrettage” pressure without further deformation.

=Liquid Storage Tanks=
Vertical cylindrical tanks are common in industry for storage of liquid. Volumes can range from a few hundred to several thousand gallons. The main load for these tanks is the hydrostatic head. However, tanks with large vertical profiles may need to account for wind loading, and perhaps snow on the top as well.

=Testing=
==Nondestructive testing==

Nondestructive testing methods are ways of evaluating the integrity of a vessel without compromising it. Inspections need to be carried out for new vessels and regularly once operation begins.

The simplest is a visual inspection for cracks or defects on the surface. It is also the cheapest, requiring only an inspector.

Radiography is used to detect subsurface cracks and defects. It is difficult and expensive, and may require specialized inspectors. It is required by the code in certain cases.

Ultrasonic detection can be used during operation to detect wall thinning.

==Pressure Testing==
The ASME BPV Code requires pressure testing with an inspector present before vessels can be approved.

Both hydraulic and pneumatic pressure tests are used. Hydraulic testing is preferred to pneumatic for safety reasons because much less energy is stored in compressed liquid than in compressed gas (Towler and Sinnott, 2013).

The equation below is typically used to determine an appropriate test pressure (Towler and Sinnott, 2013).

<math>Test Pressure = 1.30 \left[ P_d \frac{S_a}{S_n} \times \frac{t}{t-c} \right] </math>

Where:

<math>P_d</math> = design pressure, N/mm^2

<math>S_a</math> = maximum allowable stress at test temperature, N/mm^2

<math>S_n</math> =maximum allowable stress at the design temperature, N/mm^2

<math>c</math> = corrosion allowance, mm

<math>t</math> = actual plate thickness, mm

Adjustments are made for the testing and design temperature. If the thickness cannot be calculated using known methods, a hydraulic proof test is required by the ASME BPV Code (Towler and Sinnott, 2013).

=Fatigue-induced failure=

Stress cycles can occur as a result of normal operations. Possible periodic causes include:

1. Fluctuations in pressure

2. Temperature cycling

3. Vibrations

4. Water hammer

5. Fluctuations in flow of fluids or solids

6. Fluctuations in external load

The endurance limit is the number of cycles for failure at a given set of conditions of cyclic stress. If this number of cycles is
exceeded, the vessel will fail (Towler and Sinnott, 2013).

=Conclusion=
Many processes in the chemical industry are carried out at pressures greater than the atmosphere. Gases are also compressed and stored. Any vessel that will experience a pressure difference between the sides of the walls must be strong enough to withstand it. Usually the difference is between the inside and the external atmosphere, but it can also exist internally, as in a heat exchanger. A large amount of potential energy can exist as a pressure difference, and correct design of pressure vessels is an integral part to plant safety. As such, there are codes and standards guiding all aspects of using them. In North America, the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPV Code) is used. While chemical engineers will generally not carry out the immediate design, they will need to communicate specifications based on their understanding of process conditions to the vessel design engineers.

=References=

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Estimation of capital

2015-03-02T04:20:02Z

Jian: /* References */

Authors: Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: 2/9/2014

 

==Introduction==

One of the most important aspects of determining the overall economic viability of a chemical process is determining the capital cost. In addition to the purchase price of the equipment, capital costs include delivery and installation of equipment, preparation of land for construction, salaries of contractors and construction workers, and any other costs associated with building a chemical plant. For this reason, the cost associated with process equipment is not as straightforward as the sticker price.

==Components of Capital Cost==

===Fixed Capital Investment===

The fixed capital investment is the total cost associated with constructing the plant. This cost includes design, site remediation, purchasing process equipment, developing infrastructure, and contingency charges, and includes the raw material costs as well as labor. It is divided into four categories.

====ISBL (Inside Battery Limits) Plant Costs====

ISBL (Inside Battery Limits) plant costs are the cost of procuring and installing all process equipment. ISBL costs include purchasing and shipping costs of equipment, land costs, infrastructure, piping, catalysts, and any other material needed for final plant operation, or construction of the plant. ISBL costs also include any associated fees with construction such as permits, insurance, or equipment rental, even if these items are not needed once the plant is operational.

ISBL is often defined as the "inner" cost of the plant, in that it is the cost associated with building the plant itself, from unloading the raw materials to shipping final products. Any costs associated with developing the plant itself is considered ISBL. It is important and relatively straightforward to obtain an estimate for the ISBL of the plant, and as other costs are often estimated based on the result of the ISBL, it is critical that this value is as accurate as possible.

====OSBL (Outside Battery Limits) Plant Costs====

OSBL (Outside Battery Limits), or off-site costs, are still an important component of the plant cost, but deals with calculating costs associated with off-site developments that require the plant to run. For example, if water or electricity are being utilized from the main grid, and infrastructure needs to be expanded to accommodate the chemical plant's addition to these systems, these costs are considered OSBL because they are not directly associated with elements between the input and output of the chemical plant.

Other examples of OSBL costs include fencing and security, utilities such as steam or electricity generators, sewers and waste treatment, firefighting and emergency equipment, offices and laboratories, and employee amenities. These facilities and pieces of equipment are not directly affiliated with the process but are critical costs associated with constructing any work site, and are filed under OSBL cost.

OSBL costs are initially estimated as a percentage of the ISBL costs. If not a lot of information ins available, a rule of thumb is to use 40% of the ISBL costs as an estimate for OSBL. However, once detailed information such as the exact site and plant layout are known, OSBL costs can be calculated in a manner similar to the ISBL costs.

====Engineering Costs====

Many of the steps involved in designing detailed equipment or structures onsite fall outside the scope of chemical process design. Rather than having the plant engineer do these designs anyway, a contractor is usually hired to do this design. The costs associated with generating a design, and in some cases all the way through finished fabrication and installation of equipment is filed under engineering costs. Depending on the size of the project and the amount contracted to the outside, engineering costs may include 30% of the ISBL and up to all of the OSBL, or only 10% of the ISBL. This cost depends largely on the size of the parent company, and whether or not it has in-house capability to do detailed design of the many different processes and equipment within a chemical plant.

====Contingency Charges====

Once costs are determined, if one could instantaneously construct the plant, then there would be no need for contingency charges. Contingency charges exist though because prices change, unanticipated costs arise, and other unexpected events can cause changes in costs. Contingency charges ensure that there is enough capital on hand to deal with these unexpected changes. Usually, contingency charges are billed to the parent organization, or of the design is done by a contractor to the contracting organization directly at the start of the project, rather than asking for increased funding mid-project. An absolute minimum for contingency charges is 10% of the ISBL and OSBL, with a more realistic value being closer to 40%.

===Working Capital===

In addition to installation and construction costs, all equipment and buildings need maintenance. To handle this, a certain amount of capital is kept in reserve to handle maintenance costs. This is termed the "working capital" of the plant, in addition to the fixed investment. Working capital is not money that has been spent yet, but is tied up for use in maintaining the plant. Due to the time-value of money, calculating the costs associated with keeping this money but not having spent it on depreciating equipment is non straightforward.

==Accuracy and purpose of Capital Cost Estimates==
The accuracy of the total cost of a project will become more accurate as the project continues. The Association for the Advancement of Cost Estimating International (AACE International) classifies five types of estimates of capital cost.
# Order of Magnitude. (±30–50%) First estimation conducted for screening purposes based on cost of similar processes.
# Preliminary Estimates. (±30%) Based on only a few design detail.
# Definitive Estimates. (±10–30%) Improved estimation with incorporation of more equipment detail.
# Detailed Estimates. (±5-10%) Incorporation of individual equipment cost.
# Check Estimates. (±5–10%) Final estimation based on completed design.

==Order of Magnitude Estimates==
For the early stages of the design process, it is often necessary to make quick capital cost estimates of total plant cost. The accuracy of these order of magnitude estimates are usually within ±50% accuracy. The quickest and most often employed order of magnitude process scales the cost of the new design based on the cost of similar processes.

Towler gives the following equation to estimate the new design cost based on values which can be found in Towler and Sinnott (2013) Table 7.1:

<math>C=aS^n</math>

C = cost of new plant

a = constants

S = size parameters, based on existing plants

n = exponent constant

==Estimating Purchased Equipment Costs==
===Sources of Equipment Cost Data===
Obtaining accurate and updated equipment costs is an important matter and there are a variety of sources to obtain this information.
* Engineering, Procurement, and Construction (Contractors) companies
* Cost engineering department (common in large companies)
* Catalog or list prices
* Cost estimation software
* Cost correlations
* Estimate total cost based on cost of components

===Cost Correlation===
Cost curves can be used as preliminary estimation of equipment costs if updated cost data is not available.

<math>C_e=a+bS^n</math>

C_e = purchased equipment on a U.S. Gulf Coast basis

a,b = constants

S = size parameters

n = exponent constant

Correlations for constants can be found in Towler's Chemical Engineering Design (Towler and Sinnott, 2013).

Example: Estimate the cost of a 30 m^2 double pipe heat exchanger.
C_e = 1900 + 2500*S^1.0 for S = [1 m^2, 80 m^2]
C_e = $76900

===Estimation based on component cost===
If the process of design and construction of a piece of equipment is known, then it is preferred by professional cost estimators to estimate total cost based on the cost of materials, labor, and manufacturer profit. Estimation of cost based on component cost will allow an unbiased estimation of real cost, allowing accurate estimation as well as possible price negotiation.

==Estimating Installed Costs: The Factorial Method==
Before the chemical plants can be built, capital cost estimates must be made. This is done by using the factorial method. Accuracy and the reliability of the estimate will heavily depend on the availability of the data and the level of the design at the time. Lang proposed capital cost equipment by given equation:
C = F * Sum(C_e)
C is the total capital cost, F is the installation factor also known as Lang factor, and C_e is the cost of major equipment. Lang factor is 3.1 for solid processing plant and 4.74 for fluids processing plant. Better estimate can be made when the different factors are used for corresponding equipment. Lang factor for different equipment can be found in calibrated data chart.
Usually, the above method is used as a preliminary estimate. When more detail has been acquired, installation factor are more rigorously estimated. In detailed factorial estimates, other direct costs are compounded into the Lang factor. Installation factors are usually based on a specific material for its equipment, usually carbon steel. Failure to properly correct installation factors for materials of construction is one of the most common sources of error with the factorial method. Material factor, however, does not linearly scale with the installation factor since the transportation cost, labor cost, and fabricator’s cost does not scale with the material of the equipment. Many variations of the factorial method exist as different assumptions can be made which will determine the rigorousness and the accuracy of the estimate.

==Cost Escalation==

Cost estimation is a method base that basis its calculation from historical data. The prices of the construction and the labor are subject to inflation; therefore, a method has to be used to update old cost data. The method relates present costs to past costs that are based on statistical digests. To get the best estimate, each job should be broken down into its components and separate indices should be used for labor and materials. A composite index for the United States process plant industry is published in the journal Chemical Engineering. For oil refinery and petrochemicals projects, the Oil and Gas Journal publishes the Nelson-Farrer Refinery Construction Index. Both indices are updated monthly and indices for forty types of equipment are updated quarterly. There are also other indices for building the plants offsite. All cost indices should be used with caution and judgment. They do not fully represent the true costs for any particular piece of equipment or plant, nor the effect of supply and demand on prices. The closer the date of the estimate made from the date of indices published, estimate is more reliable.

==Location Factors==
Because of the abundance of chemical engineering plants in the U.S Gulf Coast, it is often the standard for plant and equipment cost. Cost of plant construction will differ based on:
* Construction Infrastructure
* Labor costs
* Transportation costs
* Tax Rates
* Exchange Rates

It is common to convert cost of construction to locations other than the U.S. Gulf Coast by applying a location factor around the U.S. Gulf Coast in which: <math>\mbox{Cost of Plant Construction} = (\mbox{Cost of Plant in Gulf Coast}) \mbox{X} (\mbox{Location Factor})</math>

Location Factors fluctuate with currency exchange rates and time. A rule of thumb is to that every 1000 miles away from the nearest major industrial center adds 10% to the location factor. Specific location factors can be found in the most recent edition of Aspen Richardson's International Construction Cost Factor Location Manual (Costdataonline.com).

==Estimating Offsite Capital Costs==

As mentioned above, OSBL costs are usually estimated as a percentage of ISBL costs until detailed site information and site layout are available for design.

For new sites, the OSBL costs are often estimated as a higher percentage of the ISBL due to a greater need for remediation. Especially in cases involving handling solids, OSBL costs can be as high as 100% of the ISBL cost.

The other extreme is utilizing an existing, underused site with no solids handling requirement, when fabricating a low-volume specialty chemical. In these cases, OSBL will be as low as 20% of the ISLB. For most cases, however, a typical value is 40%, and will be slightly higher for new plants, lower for existing sites with high capacities.

Once requirements for onsite steam and electricity are determined, more detailed design can be done. Usually, specialized suppliers install the entire utilities system, or the entire fencing system, or provide the entire firefighting service, so many of the components of OSBL capital costs are simply negotiated with contractors.

If the scope of the project changes, or if the project undergoes "scope creep," it is often easier to add capacity buy purchasing additional utilities from the outside once existing utilities have been constructed. However, this can lead to rapid changes in utility costs and the engineer should be aware of scope creep, as it can quickly change a viable process into an economically undesirable one.

==Computer Tools for Cost Estimating==
It is difficult for smaller companies that do not specialize in process design to maintain accurate data on process costs and perform the necessary analysis for this data to be useful. Instead, most companies use costing software and other computer tools to perform economic analysis.

Several computer tools by Aspen Tech are available for estimating capital costs. Aspen's Economic Evaluation Product Family builds off of its original ICARUS technology. In the aspenONE product suite, the primary capital estimation tool is Aspen Capital Cost Estimator. It couples with Aspen Economic Evaluation to provide capital evaluations during process design and operation.

Some issues that have arisen in the past utilizing ICARUS, or Aspen Capital Cost Estimator are as follows:

*Mapping equipment from process simulations to ICARUS can simplify design or map dummy equipment that is not real process equipment.

*It is good practice to include design factors for safety throughout the process. However, Aspen will map the equipment exactly as specified in HYSYS and therefore will not include an design factors in calculating the capital costs

*Pressure vessels are costed exactly according to ASME Boiler and Pressure Vessel Code Section VIII Division 1. However, in some cases, this may an inadequate pressure vessel design. In these cases, the design should be manually entered.

*Some processes require nonstandard components that HYSYS has no way of modeling correctly and for which ICARUS has no appropriate equipment category. Aspen has the capability to include non-standard equipment libraries which often can be obtained by equipment manufacturers. Adding these libraries allows use of the costing software for cost estimates.

==Validity of Cost Estimates==

One thing to keep in mind is that cost estimates are inherently associated with relatively high uncertainty. By leaving many aspects of the plant unspecified, the error grows dramatically. This should be kept in mind when utilizing cost estimates to perform economic analysis of the chemical process. A process that appears viable but has 50% error associated with capital costs, may quickly become undesirable as the project evolves. For this reason, it is essential that cost estimates include the most detailed design data possible.

==Conclusions==
While determining the capital cost of a chemical plant is difficult, it is an extremely vital aspect of determining of construction of a given plant is feasible given realistic financial constraints. For this reason, a number of tools have been developed to produce capital cost estimates at relatively early phases of plant construction including order of magnitude estimates, cost curve calculations, and more detailed costing of designed process equipment and other ancillary buildings and equipment.

==References==

Costdataonline.com. Richardson International Construction Factors Manual [Internet]. Pahrump: Cost Data On Line, Inc.; c2008- [cited 2015 Feb 26]. Available from: http://www.icoste.org/Book_Reviews/CFM-Info.pdf.

Mecklenburgh JC. Plant Design and Economics for Chemical Engineers. New York: Halsted Press; 1985.

Peters MS, Timmerhaus KD, West RE. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw-Hill; 2002.

Towler G, Sinnott R. Capital Cost Estimating. In: Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013. p. 307–354.

Estimation of production cost and revenue

2015-03-02T04:19:42Z

Jian: /* References */

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design (Towler and Sinnott, 2013).
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD (Turton et al., 2013).There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities (Towler and Sinnott, 2013). Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD (Turton et al., 2013). This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP (Towler and Sinnott, 2013). The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment (Turton et al., 2013). These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges (Towler and Sinnott, 2013).

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton (Towler and Sinnott, 2013).

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant (Turton et al., 2013).

The number of operators required per shift, <math>N_{OL}</math> can be estimated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps (Turton et al., 2013). For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year (Turton et al., 2013). The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
These are the costs associated with labor and materials necessary to maintain plant production. An estimate of these are 6% of the fixed capital investment (Turton et al., 2013).

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies. An estimate of these costs are 5% of the total manufacturing cost (Turton et al., 2013).

===Taxes and Insurance===
Taxes vary by location, but a first estimate of property taxes and liability insurance is 3% of the fixed capital investment (Turton et al., 2013).

===Plant Overhead===
Overhead costs are the miscellaneous but necessary costs of running a business, including payroll, employee benefits, and janitorial services. This may be estimated as 70% of the operating labor costs, added to 4% of the fixed capital costs (Turton et al., 2013).

===Licensing and Royalties===
The costs of paying for the use of intellectual property clearly varies, but an estimate that may be used is 3% of the total manufacturing cost (Turton et al., 2013).

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost (Towler and Sinnott, 2013).

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher (Towler and Sinnott, 2013).

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

<math>CCOP = VCOP + FCOP</math>

where <math>VCOP</math> is the variable cost of production and <math>FCOP</math> is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

<math>Gross\ profit = Main\ product\ revenues - CCOP</math>

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

<math>Net\ profit = gross\ profit - taxes</math>

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==Example Case: Estimating Cost of Production==

Use the following information to estimate the manufacturing cost of a plant producing 120*10^6 lb/year with a product price of $0.20/lb.

:Fixed Capital: $15,000,000
:Working Capital: $3,000,000
:'''Fixed and Working Capital = FC + WC = $18,000,000'''
:Raw Material Cost: $9,600,000/yr
:Utilities: $1,440,000/yr
:Labor: $1,800,000/yr
:Maintenance (6% yr f.c.): $900,000/yr
:Supplies (2% yr f.c.): $300,000/yr
:Depreciation (8%/yr): $1,200,000/yr
:Taxes, insurance (3%/yr): $450,000/yr
:'''Total Manufacturing Cost = RMC + U + L + M + S + D + T = $15,690,000/yr'''
:'''Gross Sales = Production * Product price = $24,000,000/yr'''
:'''Gross Profit = Gross Sales - Manufacturing Cost = $8,310,000/yr'''

==Conclusion==
Thermodynamics and kinetics are essential to designing an operational plant, but at the end of the day profits and margins are what make plants go from the engineering paper pad to operating continuously. Before any ground is broken, estimation of production costs and revenues are absolutely necessary to assure CEO's and shareholders that this process is a profitable and worth while venture. There are many avenues to achieve these answers with some being more accurate than others. The best indicator of these answers will be in pilot plant design which will provide appropriate estimations for scaled up processes.

==References==

Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Sensitivity analysis and design optimization

2015-03-02T04:19:16Z

Jian: /* References */

Author: Anne Disabato, Tim Hanrahan, Brian Merkle

Steward: David Chen, Fengqi You

Date Presented: February 23, 2014

 


__TOC__

=Introduction=
Optimization and sensitivity analysis are key aspects of successful process design. Optimizing a process maximizes project value and plant performance, minimizes project cost, and facilitates the selection of the best components (Towler and Sinnott, 2013).

=Design Optimization=
Economic optimization is the process of finding the condition that maximizes financial return or, conversely, minimizes expenses. The factors affecting the economic performance of the design include the types of processing technique and equipment used, arrangement, and sequencing of the processing equipment, and the actual physical parameters for the equipment. The operating conditions are also of prime concern.

Optimization of process design follows the general outline below:

#Establish optimization criteria: using an objective function that is an economic performance measure.
#Define optimization problem: establish various mathematical relations and limitations that describe the aspects of the design
#Design a process model with appropriate cost and economic data

Although profitability or cost is generally the basis for optimization, practical and intangible factors usually need to be included as well in the final investment decision. Such factors are often difficult or impossible to quantify, and so decision maker judgment must weigh such factors in the final analysis (Peters and Timmerhaus, 2003; Ulrich, 1984).

=Defining the Optimization Problem and Objective Function=
In optimization, we seek to maximize or minimize a quantity called the goodness of design or objective function, which can be written as a mathematical function of a finite number of variables called the decision variables.

<math> z = f(x_1 , x_2 , ... x_n) </math>

The decision variables may be independent or they may be related via constraint equations. Examples of process variables include operating conditions such as temperature and pressure, and equipment specifications such as the number of trays in a distillation column. The conventional name and strategy of this optimization method varies between texts; Turton et al suggests creating a base case prior to defining the objective function and Seider et al classifies the objective function as a piece of a nonlinear program (NLP) (Seider et al., 2004; Turton et al., 2012).

A second type of process variable is the dependent variable; a group of variables influenced by process constraints. Common examples of process constraints include process operability limits, reaction chemical species dependence, and product purity and production rate. Towler & Sinnott define equality and inequality constraints (Towler, 2012). Equality constraints are the laws of physics and chemistry, design equations, and mass/energy balances:

<math> h(x_1 , x_2 , ... x_n ) = b_1 </math>

For example, a distillation column that is modeled with stages assumed to be in phase equilibrium often has several hundred MESH (material balance, equilibrium, summation of mole fractions, and heat balance) equations. However, in the implementation of most simulators, these equations are solved for each process unit, given equipment parameters and steam variables. Hence, when using these simulators, the equality constraints for the process units are not shown explicitly in the nonlinear program. Given values for the design variables, the simulators call upon these subroutines to solve the appropriate equations and obtain the unknowns that are needed to perform the optimization (Seider et al., 2004).

Inequality constraints are technical, safety, and legal limits, economic and current market:

<math> g(x_1 , x_2 , ... x_n ) \frac {\geq} {\leq} b_2 </math>

Inequality constraints also pertain to equipment; for example, when operating a centrifugal pump, the head developed is inversely related to the throughput. Hence, as the flow rate is varied when optimizing the process, care must be taken to make sure that the required pressure increase does not exceed that available from the pump (Seider et al., 2004).

It is important that a problem is not under or over-constrained so a possible solution is attainable. A degree-of-freedom (DOF) analysis should be completed to simply the number of process variables, and determine if the system is properly specified.

==Trade-Offs==
A part of optimization is assessing trade-offs; usually getting better performance from equipment means higher cost. The objective function must capture this trade-off between cost and benefit.

Example: Heat Recovery, total cost captures trade-off between energy savings and capital expense.

[[File:SAO1.PNG|center|600px]]
Figure 1: Trade-off example (Towler and Sinnott, 2013)

Some common design trade-offs are more separations equipment versus low product purity, more recycle costs versus increased feed use and increased waste, more heat recovery versus cheaper heat exchange system, and marketable by-product versus more plant expense.

==Parametric Optimization==
Parametric optimization deals with process operating variables and equipment design variables other than those strictly related to structural concerns. Some of the more obvious examples of such decisions are operating conditions, recycle ratios, and steam properties such as flow rates and compositions. Small changes in these conditions or equipment can have a diverse impact on the system, causing parametric optimization problems to contain hundreds of decision variables. It is therefore more efficient to analyze the more influential variables effect on the overall system. Done properly, a balance is struck between increased difficulty of high-variable-number optimization and optimization accuracy (Seider et al., 2004).

==Suboptimizations==
Simultaneous optimization of the many parameters present in a chemical process design can be a daunting task due to the large number of variables that can be present in both integer and continuous form, the non-linearity of the property prediction relationships and performance models, and frequent ubiquity of recycle. It is therefore common to seek out suboptimizations for some of the variables, so as to reduce the dimensionality of the problem (Seider et al., 2004). While optimizing sub-problems usually does not lead to overall optimum, there are instances for which it is valid in a practical, economic sense. Care must always be taken to ensure that subcomponents are not optimized at the expense of other parts of the plant.

Equipment optimization is usually treated as a subproblem that is solved after the main process variables such as reactors conversion, recycle ratios, and product recoveries have been optimized.

=Optimization of a Single Decision Variable=
If the objective is a function of a single variable, x, the objective function f(x) can be differentiated with respect to x to give f’(x). The following algorithm summarizes the procedure:

[[File:SAO5.PNG|center|600px]]

Below is a graphical representation of the above algorithm.

[[File:SAO2.PNG|center|500px]]
Figure 2. Graphical Illustration of (a) Continuous Objective Function (b) Discontinuous Objective Function

In Figure2a, <math> x_L </math> is the optimum point, even though there is a local minimum at <math> x_S1 </math>; In Figure 2b, the optimum is at <math> x_DI </math>.

==Search Methods==
Search methods are at the core of the solution algorithms for complex multivariable objective functions. The four main search functions are unrestricted search, three-point interval search, golden-section search, and quasi-newton method (Towler and Sinnott, 2013).

===Unrestricted Search===
Unrestricted Searching is a relatively simple method of bounding the optimum for problems that are not constrained. The first step is to determine a range in which the optimum lies by making an initial guess of x and assuming a step size, h. The direction of search that leads to improvement in the value of the objective is determined by z1, z2, and z3 where

<math> z_1 = f(x) </math>

<math> z_2 = f(x+h) </math>

<math> z_3 = f(x-h) </math>

The value of x is then increased or decreased by successive steps of h until the optimum is passed. In engineering design problems it is almost always possible to state upper and lower bounds for every parameter, so unrestricted search methods are not widely used in design.

The three-point interval is done as follows:
# Evaluate f(x) at the upper and lower bounds, <math> x_L </math> and <math> x_U </math>, and at the center point, <math> \frac {x_L+ x_U} {2} </math>.
# Two new points are added in the midpoints between the bounds and the center point, at <math> \frac {3x_L + x_U} {4} </math> and <math> \frac {x_L + 3x_U} {4} </math>
# The three adjacent points with the lowest values of f(x) (or the highest values for a maximization problem) are then used to define the next search range.

By eliminating two of the four quarters of the range at each step, this procedure reduces the range by half each cycle. To reduce the range to a fraction ε of the initial range therefore takes n cycles, where <math> \epsilon = 0.5^n </math>. Since each cycle requires calculating f (x) for two additional points, the total number of calculations is <math> 2n = \frac {2 log \epsilon} {log 0.5} </math>.
The procedure is terminated when the range has been reduced sufficiently to give the desired precision in the optimum. For design problems it is usually not necessary to specify the optimal value of the decision variables to high precision, so <math> \epsilon </math> is usually not a very small number.

The golden-section search is more computationally efficient than the three-point interval method if <math> \epsilon < 0.29 </math>. In the golden-section search only one new point is added at each cycle. The golden-section method is illustrated in Figure 3.

[[File:SAO3.PNG|center|500px]]
Figure 3: Golden-Section Method

We start by evaluating <math> f(x_L) </math> and <math> f(x_U) </math> corresponding to the upper and lower bounds of the range, labeled A and B in the figure. We then add two new points, labeled C and D, each located a distance ωAB from the bounds A and B, i.e., located at

[[File:SAO6.PNG|left|100px]]

and

[[File:SAO7.PNG|left|100px]]

For a minimization problem, the point that gives the highest value of f(x) is eliminated. In Figure 3, this is point B. A single new point, E, is added, such that the new set of points AECD is symmetric with the old set of points ACDB. For the new set of points to be symmetric with the old set of points,

<math> AE = CD = </math>ω<math>AD </math>

But we know

<math> DB = </math>ω<math>AB </math>

so

<math> AD = (1 - </math>ω<math>)AB </math>

<math> CD = (1 - 2</math>ω<math>)AB </math>

<math> (1 - 2</math>ω<math>) = </math>ω<math> (1- </math>ω<math>) </math>

<math> </math>ω<math> = \frac{(3 \pm \sqrt{5})} {2} </math>

Each new point reduces the range to a fraction 1 − ω = 0.618 of the original range. To reduce the range to a fraction <math> \epsilon </math> of the initial range therefore requires <math> n = \frac {log \epsilon} {log 0.618} </math> function evaluations. The number 1 − ω is known as the golden mean.

The Quasi-Newton method is a super-linear search method that seeks the optimum by solving f’(x) and f’’(x) and searching for where f’(x) = 0. The value of x at step k + 1 is calculated from the value of x at k using

<math> x_(k+1) = x_k - \frac {f'(x_k)} {f''(x_k)} </math>

and the procedure is repeated until <math> (xk+1 - xk) </math> is less than a convergence tolerance, <math> \epsilon </math>.
If we do not have explicit formulate for f’(x) and f’’(x), then we can make a finite difference approximation about a point:

<math> x_(k+1) = x_k - \frac {\frac {f(x_k+h)-f(x_k-h)} {2h}} {(f(x_k+h)- 2f(x) + \frac {f(x_k - h)} {h^2} )} </math>

The Quasi-Newton method generally gives fast convergence unless f’’(x) is close to zero, in which convergence is poor.

All of the methods discussed in this section are best suited for unimodal functions, functions with no more than one maximum or minimum within the bounded range.

=Optimization of Two or More Decision Variables=
A two-variable optimization method can be solved in one of the following ways:
#Convexity: Solve graphically using constraint boundaries.
#Searching in two dimensions: Extensions of the methods used for single variable line searchers
#Probabilistic Methods

Multivariable optimization is much harder to visualize in the parameter space, but the same issues of initialization, convergence, convexity, and local optima are faces. The best means to optimize systems with multiple variables is an area researched today.

Some of methods are listed below:
#Linear programming
#Nonlinear Programming (NLP)
##Successive Linear Programming (SLP)
##Successive Quadratic Programming (SQP)
##Reduced Gradient Method
#Mixed Integer Programming
##Superstructure Optimization

Seider gives simple case studies on how to solve an NLP using ASPEN PLUS and HYSYS, beginning with simulation model of the process to be optimized and simple case studies in which the objective function is evaluated with using an automated optimization algorithm.

=Optimization in Industrial Practice=
Many of the methods listed above are used industrially, especially linear programming and mixed-integer linear programming, to optimize logistics, supply-chain management, and economic performance. The specifics are traditionally a topic for industrial engineers.

==Optimization in Process Design==
Few industrial designs are rigorously optimized because:

#The errors introduced by uncertainty in process models may be larger than the differences in performance predicted for different designs. Thus rendering the models ineffective.
#Price uncertainty usually dominated the difference between design alternatives.
#A substantial amount of design work foes into cost estimates, and revisiting these design decisions at a later stage is usually not justified.
#Safety, operability, reliability, and flexibility are top priorities in design. A safe, operable, plant will often require be more expensive then the economically optimal design.

Experienced design engineers usually think through constraints, trade-offs, major cost components, and the objective function to satisfy themselves that their design is “good enough” (Towler and Sinnott, 2013).

=Sensitivity Analysis=
A sensitivity analysis is a way of examining the effects of uncertainties in the forecasts on the viability of a project (Towler and Sinnott, 2013). First a base case for analysis is established from the investment and cash flows. Various parameters in the cost model are then modified, measuring the range of error in the forecast figures; this shows how sensitive the cash flows and economic criteria are to errors in the forecast figures. The results are usually presented as plots of economic criterion, and give some idea of the risk involved in making judgments on the forecast performance of the project.

==Parameters to Study==
The purpose of sensitivity analysis is to identify the parameters that have a significant impact on project viability over the expected range of variation of the parameter. Table 1 contains typical parameters and their range of variation.

[[File:SAO4.PNG|center|300px]]
Table 1: Parameters to study in sensitivity analysis

==Statistical Methods of Risk Analysis==
In formal methods of risk analysis statistical methods are used to examine the effect of variation in all parameters. A simple method described in Towler uses estimates based on the most likely value, upper value, and lower value: ML, H, and L respectively. The upper and lower values are estimated from Table 1, and the mean and standard deviation are then estimated as

<math> \bar{x} = \frac {H + 2ML + L} {4} </math>

<math> S_x = \frac {H-L} {2.65} </math>

It is important to recognize that values of this statistical method will likely be skewed if the distribution is incorrect. The mean and standard deviation of other parameters can be calculated as a function of the equations above. This allows relatively easy estimation of the overall error in a completed cost estimate, and can be extended to economic criteria such as NPV, TAC, or ROI. Commercial programs are available for more sophisticated analyses such as the Monte Carlo method (Towler and Sinnott, 2013).

==Contingency Costs==
A minimum contingency charge of 10% is normally added to ISBL plus OSBL fixed capital to account for variations in capital cost. If the confidence interval of the estimate is known, the contingency charges can be estimated based on the desired level of certainty that the project will not exceed projected costs.

=Conclusion=
Design optimization and sensitivity analysis are essential to designing and operating a successful chemical process. Optimization can be tricky due to high levels of uncertainty and magnitude of variables, but can help minimize costs and increase efficiency. Chemical engineers need to understand the optimization methods, the role of constraints in limiting designs, recognize design trade-offs, and understand the pitfalls of their analysis. In a similar respect, sensitivity analysis is a way of examining the effects of uncertainties in the forecasts on the viability of a project. If an engineer can optimize a process and perform a sensitivity analysis, the project will be cost effective and run more smoothly.

=References=
Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G. Chemical Engineering Design. PowerPoint presentation; 2012.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Ulrich GD. A Guide to Chemical Engineering Process Design and Economics. New York: Wiley; 1984.

Materials of construction

2015-03-02T04:18:45Z

Jian: /* References */

Author: Katie Johnson [2015] 

Stewards: Jian Gong and Fengqi You

 


__TOC__

=Material Properties=
There are several properties of a material that can affect its suitability for the design. Before choosing a material, the designer should be aware of the following properties. Note that these properties for different common materials are often already collected and are available in various forms from manufacturers or in various textbooks.
==Tensile Strength==
The tensile strength, or tensile stress, of a material is the maximum amount of stress it can withstand before fracture. Proof stress, or yield stress, is similar, but measures that maximum amount of stress a material can withstand before deformation becomes permanent. Figure 1 below demonstrates where tensile strength (point u) and yield stress (point y) lay on the stress-strain curve for a material. There are standard tensile tests that measure tensile strength; however, strength is a common material property that is often already tabulated (Towler et al., 2013).

[[File:Stress_strain.png|thumb|center|upright=2.7|'''Figure 1:''' The stress strain curve for a typical ductile material (Engineering Archives)]]

In addition to considerations such as the pressure of the process, there are often guidelines that specify maximum allowable stress. One such set of guidelines is laid out by ASME in their Boiler and Pressure Vessel Code (Towler et al., 2013). This should be consulted while designing pressure vessels. There are also equations that can estimate these values. The maximum pressure that a cylindrical vessel can withstand is given by the following equations, where t is shell thickness, p is pressure, R is the inside vessel radius, and S is the allowable tensile stress:

<math> t = {p * R \over {0.9 * S - 0.6 * p}} </math>

<math> p = {0.9 * S * t \over {R + 0.6 * t}} </math>

There are tabulations of S for various metals found in Perry’s Handbook (Ulrich, 1984).

==Modulus of Elasticity==
The modulus of elasticity of a material, sometimes called its stiffness, measures the amount a material deforms when a certain amount of stress is placed on it. This measure applies when elastic deformation occurs, that is, when all deformation is reversible and is linearly proportional to stress (Callister et al., 2011). In Figure 1, the modulus of elasticity for the material would apply between the origin and point y. This is important because it measures the resistance of a material to bending and buckling (Towler et al., 2013).

==Ductility==
Ductility measures the amount a material will deform before it fractures (Towler et al., 2013). The equation for ductility is as follows:

<math> \%EL={{l_f - l_0} \over l_o} * 100\% </math> (Callister et al., 2011).

When a material has very low ductility it is defined as brittle. For example, in Figure 1 above, point f will be much closer to point u for a brittle material than for a ductile material. Brittle materials undergo very little deformation before they fracture, which means that in processes, there can be very little warming before a rupture. Some materials have a ductile-brittle transition points at low temperature. While these materials generally exhibit ductile properties, at low enough temperatures, they will not deform and will exhibit brittle fracture (Peters et al., 2003).

==Hardness==
The material’s ability to resist plastic deformation such as dents (Towler et al., 2013). There are many simple and relatively inexpensive tests, such as Rockwell Hardness Tests and Brinell Hardness Tests, which can determine the hardness of a material. It is useful to know the hardness of a material because it can be used to predict other mechanical properties such as tensile strength and can often be easier to determine (Callister et al., 2011). Figure 2 below shows an example of the correlation between Brinell hardness number and tensile strength.

[[File:TensileStrength_vs_Hardness.gif|frame|center|border|'''Figure 2:''' Tensile strength versus hardness for various materials (VanAken, 2001)]]

==Fatigue Resistance==
Fatigue is failure of a material that can occur when there is cyclic loading on equipment, for example, in pumps. It can also occur if there are cycles of temperature or pressure (Towler et al., 2013). When there is cyclic loading, failure can occur at lower stress levels than the normal tensile strength. Fatigue failure is generally very similar to brittle failure with very little plastic deformation (Callister et al., 2011).

==Other considerations==
There are many other properties to consider while selecting a material. For example, creep is the amount a material deforms while it is under constant tensile stress over long periods of time and can especially be a problem for metals at high temperatures. Other considerations include the ease of fabrication, including welding ability and flexibility, the availability and cost of material, thermal conductivity (which is especially important for equipment like heat exchangers), electrical resistance, and magnetic properties for certain cases (Towler et al., 2013).

=Process Considerations=
Before choosing a material for a process, basic information must be collected, including temperature, pressure, and chemicals involved. The properties could affect the choice of materials.

==Process Temperature and Pressure==
In addition to knowledge of the average temperature a process with operate at, the engineer must be aware of the maximum and minimum temperature that could occur. While picking materials, the effect of temperature of material properties must be considered. Higher temperatures generally decrease the tensile strength and elastic modulus of metals (Towler et al., 2013).

Additionally, very low temperatures can cause some materials to brittle fracture. Therefore, if the minimum process temperature is below the minimum allowable temperature for a material, a different material (such as low temperature carbon steel) must be selected. Note that the expected, maximum, and minimum environmental conditions should be considered in addition to internal conditions.

{| class="wikitable"
|-
|+'''Table 1:''' Recommended materials for strength at high and low temperatures (Biegler et al., 1997)
! colspan="2" | High temperature service
! colspan="2" | Low temperature service
|-
! T_max (F)
! Steel
! T_min (F)
! Steel
|-
| 950
| Carbon steel
| -50
| Carbon steel
|-
| 1300
| 330 stainless steel
| -75
| Nickel steel (A203)
|-
| 1500
| Stainless steels (304,321,347,316)
| -320
| Nickel steel (A325)
|-
| 2000
| Cast stainless, HC
| -425
| Stainless steels (302,304,310,347)
|-
|}

Similarly, the maximum and minimum pressures must be examined in relation to material properties. Different materials have different tensile stresses which affect that maximum pressure that can be used. When internal pressure is less than external pressure (that is, the process operates in a vacuum), either materials with higher allowable tensile stresses should be used or thickness should be increased.

==Corrosion==
If a process included certain corrosive chemicals such as oxygen, special allocations must be made for the materials. Additionally, environmental conditions such as salt from a nearby ocean should be considered. If corrosion is expected, the engineer should consider this in the material selection. This could involve picking a material that is naturally corrosive-resistant or by coating the inside of the pipe of equipment. These coatings can be made of paint or other organic coatings, especially for resistance to atmospheric corrosion (Towler et al., 2013). For internal protection, materials can be lined with rubber, glass, stainless steel or various polymers (Ulrich, 1984; Turton et al., 2012).

==Cycling==
Cycling occurs when a certain aspect of a process (temperature, pressure, or material levels) continually cycles between high and low levels. Cycling puts additional stress on the system and should be considered when selecting materials (Callister et al., 2011).

=Common Materials=
==Metals==
Carbon steel and stainless steels are some of the most common metals used in construction. Carbon steel is an alloy between carbon and iron. Also known as mild steel, carbon steel is one of the most commonly used engineering materials. It is favored because it is relatively cheap and widely available. It also has good tensile strength and ductility. However, carbon steel is not generally resistant to corrosion which can be an issue in many environments. When corrosion is expected, stainless steel is often favored. Stainless steel, especially with higher levels of chromium, is more resistant to corrosion (Towler et al., 2013). Stainless steel is also a better choice for low temperatures, as it has a minimum rating of -425 F, as opposed to the minimum rating of carbon steel of -50 F. Stainless steels are also a better choice than carbon steel when temperatures above 1000 F are expected (Biegler et al., 1997)

Other options include nickel and alloys, including Monel, a nickel-copper alloy (Ulrich, 1984). These are also corrosion-resistant to sulfuric and hydrocholoric acids and salt water. Nickel-chromium alloys are good to chemical resistance at high temperatures (Turton et al., 2012). Copper and alloys have the advantage of corrosion resistance and good thermal conductivity. Thus, copper is often favored for heat transfer equipment (Ulrich, 1984). Aluminum and its alloys are more moderately priced than copper metals, are lightweight, and are better for low temperatures than carbon steel, however, they have lower strength and can also be susceptible to corrosion (Ulrich, 1984). Aluminum is often appropriate for cryogenic operations (Turton et al., 2012).

{| class="wikitable"
|-
|+ '''Table 2:''' Metal properties (Towler et al., 2013)
! Material
! Tensile strength (N/mm^2)
! Modulus of elasticity (kN/mm^2)
! Brinell Hardness
! Specific Gravity
! Max Allowable Stress (ksi)
! Relative Cost
|-
| Mild (carbon) steel
| 430
| 210
| 100-200
| 7.9
| 12.9
| 1
|-
| Stainless steel
| >540
| 210
| 160
| 8.0
| 20
| 2.0-3.0
|-
| Copper
| 200
| 110
| 30-100
| 8.9
| 6.7
| 22.8
|-
| Nickel
| 500
| 210
| 80-150
| 8.9
| 10
| 39.2
|-
| Monel
| 650
| 170
| 120-250
| 8.8
| 18.7
| 16.4
|-
| Titanium
| 500
| 110
| 150
| 4.5
| 10
| 6.8
|}

==Plastics==
Plastics are becoming more commonly used when corrosion is expected. Plastics are also favored because they are inexpensive. However, they have low strength compared to metals (Ulrich, 1984). Plastics can be subdivided into several categories. The first of these is thermoplastic materials, which soften with increasing temperature. PVC falls within this category, and is the most commonly used thermoplastic material in chemical plants. The second category is thermosetting materials, which have a more rigid structure due to cross-linking. Rubber is also often used in linings for tanks and pipes (Towler et al., 2013). Table 3 lists some properties of common plastics.

{| class="wikitable"
|-
|+ '''Table 3:''' Mechanical Properties and Relative Costs of Polymers (Towler et al., 2013)
! Material
! Tensile Strength (N/mm^2)
! Elastic Modulus (kN/mm^2)
! Density (kg/m^3)
! Relative Cost
|-
| PVC
| 55
| 3.5
| 1400
| 1.5
|-
| Polyethylene (low density)
| 12
| 0.2
| 900
| 1.0
|-
| Polypropylene
| 35
| 1.5
| 900
| 1.5
|-
| PTFE
| 21
| 1.0
| 2100
| 30.0
|}

==Inorganic Nonmetals==
Inorganic nonmetals include glass, stoneware, brick and cements (Peters et al., 2003). Ceramics are generally stronger than other materials, especially at higher temperatures, they are much more brittle (Ulrich, 1984). Glass is good for corrosion resistance; stoneware is generally corrosive-resistant with more strength, but has poor thermal conductivity (Peters et al., 2003).

=Case Study=
Chlorobenzene is produced by reacting liquid benzene with gaseous chlorine. The reaction takes place at 328K and 2.4 bar. If both the feeds are at 293K and atmospheric pressure, what are appropriate materials for the inlet piping and the reactor? (Adapted from ''Chemical Engineering Design'' (Towler et al., 2013)).

Both benzene and dry chlorine are not corrosive and therefore, carbon steel can be used as the inlet piping. Note that if the gaseous chlorine is actually wet chlorine, it becomes very corrosive to most metals and a plastic should likely be used. While the reactor is at higher pressure than atmospheric pressure, it is well below the maximum allowable stress for all common materials (Towler et al., 2013). However, a side product of the reactor is HCl which is corrosive. Likely, the HCl concentration will not be high enough to corrode the material but this should be investigated further. If concentration is >50% either in the reactor or later in the process, another material such as a plastic should be

=References=
Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Callister W, Rethwisch D. Materials Science and Engineering. Wiley: New York, 2011.

Engineering Archives Website. Stress Strain Diagram. http://www.engineeringarchives.com/les_mom_stressstraindiagram.html.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Ulrich, GD. A Guide to Chemical Engineering Process Design and Economics. Wiley: New York, 1984.

VanAken D. Industrial Heating Website [Internet]. Relationship between hardness and strength [updated 2001 Mar 7; cited 2015 Mar 1]. Available from: http://www.industrialheating.com/articles/84495-engineering-concepts-relationship-between-hardness-and-strength?v=preview.

Process hazards

2015-03-02T04:16:50Z

Jian: /* References */

Title: Process Hazards

Authors: Anne Disabato, Tim Hanrahan, Brian Merkle (Winter 2014)

Steward: David Chen, Fengqi You

 


__TOC__

=Introduction=
The design and production of chemical processes is inherently hazardous, which is why process safety is of paramount importance to every company working in the chemical, fuels, and pharmaceuticals industry. While “process safety” focuses on the prevention of dangerous situation throughout the design, “process hazards” focuses on how to manage the unavoidable hazards in the final design. In the case of fires, explosions, or the release of toxic chemicals, proper safety hazard analysis will help minimize injuries and damage to the facility and environment.

In addition to moral and ethical obligations to safety, law requires it and the costs (human, social, economic) of non-compliance can be catastrophic. Listed below are three major pieces of safety legislation (Towler and Sinnott, 2013):

1. The Occupational Safety and Health Act (OSHA); 29 U.S.C. 651 et seq. (1970)
*Employers must provide a place of employment free from recognized hazards to safety and health, such as exposure to toxic chemicals, excessive noise levels, mechanical dangers, heat or cold stress, or unsanitary conditions.
2. The Emergency Planning & Community Right-To-Know Act (EPCRA); 42 U.S.C. 11011 et seq. (1986)
*To help local communities protect public health, safety, and the environment from chemical hazards.
3. The Toxic Substances Control Act (TSCA); 15 U.S.C. s/s 2601 et seq. (1976)
*Allows EPA to track industrial chemicals and ban their manufacture or import

For safety organization and terminology, safe design tactics, and the economic cost of safety, please see [[Process safety]].

=Chemical Plant Hazards=
The complex nature of chemical plants increases the number of hazards associated with operation and facility maintenance. Understanding the scope of (1) material and (2) process hazards is essential to safe design and operation. Below are examples of chemical plant hazards.

==Material Hazards==

===Toxicity===
Nearly every chemical plant is holding large quantities of various chemicals, which can be of serious concern for workers and local residents. Even chemicals with low toxicity can be deadly in the quantities used in manufacturing. Most exposure to high toxicity chemicals occurs from inhalation (Peters and Timmerhaus, 2003). Process design needs to consider the elimination or substitution of the most hazardous compounds, prevention of releases, containment, disposal, ventilation, and emergency procedures.

The following are important toxicity definitions
* Acute Effects- Symptoms that develop rapidly, usually as a result of short-term exposure. These effects can be a result of oral, dermal, gas, vapor, dust, or mist inhalation.
* Chronic Effects: Symptoms that develop over a long period of time, often as a result of long-term exposure. Example: Cancer
* LD50- Lethal dose at which 50% of test animals are killed. Indicates acute effects only, expressed in mg/kg body mass
* Threshold Limit Value (TLV) or Permissible Exposure Limit (PEL)- Concentration the average worker can safely be exposed to for 40 hr/week
**PEL published by OSHA : http://www.osha.gov/SLTC/healthguidelines/
**TLV published by American Conference of Government Industrial Hygienists. http://www.acgih.org/home.htm

Toxic Substance Control Act or TSCA (15 U.S.C. s/s 2601 et seq., 1976) is USEPA’s version of the Food and Drug Act. The TSCA allows EPA to regulate the 75,000 chemical substances used in industry (including confidential materials). Additionally, it requires extensive review before approval is given by USEPA to manufacture, import and sell a new chemical in the USA. Under TSCA, USEPA can ban or restrict the import, manufacture and use of any chemical, and anyone has the right and obligation to report information about new or alleged health/environmental effects caused by a chemical.

===Flammability===
Flammability is the measurement of how easily a material will burn or ignite, resulting in a fire or combustion. A fire requires three things: fuel, oxidant, and source of ignition (or auto-ignition). Possible sources of ignition at a chemical facility should be assessed and eliminated; this include electrical equipment such as motors or actuators, open flames from furnaces, incinerators or flare stacks, and undefined sources such as matches, lighter or mobile phones (Biegler et al., 1997).

Important flammability related properties must be measured:
* Flash Point – function of vapor pressure; lowest temperature at which the material will ignite from an open flame
* Auto-ignition temperature- temperature at which the substance ignites in air spontaneously
* MSDS information
* Flammability limits- highest and lowest concentrations in air (NTP) at which a flame will propagate through the mixture (Peters and Timmerhaus, 2003)
** LFL (lower flammable limit): mixture of fuel and air below this is too lean
** UFL (Upper flammable limit): mixture of fuel and air below this will not burn

The LFL and UFL of mixtures can be calculated using Le Chatelier’s Equation (Seider et al., 2004):

<math> FL_m = \frac {1} {\sum_{i=1}^C (y_i/FL_i)} </math>

where <math> FL_i </math> is the flammability limit of a specific component, and <math> y_i </math> is the concentration. While the LFL is relatively independent of pressure, the UFL changes at different pressures according to the following equation:

<math> UFL_P = UFL + 20.6[log(P)+1] </math>

where P is in MPa and UFL is the upper flammability limit at 1 atmosphere.

Fire protection is best accomplished by containing flammable materials. Other tactics include:
* Inerting- an inert gas is added to reduce the oxygen concentration below the minimum oxygen concentration (MOC) at which explosions can occur
* Reducing static electricity- by installing ground devices or using antistatic additive to increase conductivity
* Explosion-proof equipment- designed to absorb shock after explosion and prevent the combustion from spreading.
* Flame arrestors- specified on vent lines of equipment that contains flammable materials to prevent a flame from propagating back from the vent
* Sprinkler systems

===Incompatibility===
When certain hazardous chemicals are stored or mixed together, violent reactions may occur because the chemicals are incompatible. Combination of interest include:

# Acids and Bases
# Acids and Metals
# Fuels and Oxidants
# Free radical initiators and Epoxides, Peroxides, or Unsaturates.

Chemical incompatibility can lead to runaway reactions, and material incompatibility can lead to corrosion of vessels, internals, and instruments as well as the softening of gaskets, seals, and linings.

===Material Hazards Conclusions===
Material hazards account for a wide variety of incidents. Six factors should be considered in design for material hazards: (1) substitution, (2) containment, (3) prevention of releases, (4) ventilation, (5) disposal, and (6) provision of emergency equipment. Consulting the Material Safety Data Sheets (MSDS) is also essential in accounting for hazards. Please see the MSDS section under “Process Hazard Analysis Tools.”

==Process Hazards==
===Overpressure===
Overpressure occurs when mass, moles or energy accumulates in a contained volume (or space with restricted outflow), and can be extremely dangerous. The rise in pressure is determined by the rate of accumulation. Process controls are one tool used to control process pressures, but in the case of overpressure, they may not be able to response quickly enough. If pressure is not released by a pressure safety value, a vessel could rupture or explode resulting in the loss of containment. Please see [[Process hydraulics]] and [[Pressure Vessels]] for help with creating an appropriate design. Pressure relief values and rupture disks should be installed on all pressure vessels.

===Fires and Explosions===
Chemical plant fires can quickly damage control systems and equipment, causing overpressure, loss of containment, and explosions. In addition to protecting expensive equipment, the safety and lives of workers, local residents, and the environment are put at risk if a fire starts. It is important to follow fire protection guidelines (NFPA 30, API RP 2001, API Publ 2218) and legal requirements set by OSHA (29 CFR 1910 L) (Towler and Sinnott, 2013).

As mentioned in the “Flammability” section, the use of electrical equipment in chemical plants can ignite a fire. Electrical equipment use is regulated by law through OSHA standard 29 CFR 1910.307 and industry design codes, National Electrical Code NFPA 70 and NFPA standards 496,497, API RP 500, 505 (Towler and Sinnott, 2013). These codes define equipment and installation regulations, and specific precautions that must be taken in risky areas.

An explosion is a worst-case result of a fire, defined as the sudden, catastrophic release of energy causing a pressure wave. The following are explosion related definitions:
* Deflagration- an exposition where combustion zone propagates at subsonic flame speed, usually < 30 m/s, and pressure wave < 10 bar. Deflagration can turn into detonation when propagating along a pipe.
* Detonation- an exposition where combustion zone propagates at supersonic velocity, 2000 – 3000 m/s, and pressure wave 20 bar. The principal heating mechanism is shock compression, and requires confinement of a high-intensity source
* Expansion factor- measure of the increase in volume resulting from combustion:

<math> E = \frac{\rho_R} {\rho_P} </math>

where <math> \rho_R </math> is the molar density of the reagents and <math> \rho_P </math> is the molar density of the products, and the maximum value of E is for adiabatic combustion (Towler and Sinnott, 2013).

* Flame speed- the rate of propagation of a flame front through a flammable mixture, with respect to a fixed observer

Explosivity properties can be found in textbooks such as An Introduction to Fire Dynamics by Dugdale (1985), as shown below.

[[File:Hazards 1.PNG|center|800px|frame|Figure 1. Explosivity Properties (Dugdale, 1985).]]

===Loss of Containment===
Loss of containment can occur due to pressure relief, operator error, poor maintenance procedures, such as failure to drain and purge properly, or leaks from degraded equipment.

Containment is one of the six principles of “Inherently Safe Design,” laid out in the wiki page for [[Process safety]] (Turton et al., 2003). If hazardous materials cannot be eliminated, they should at least be stored in vessels with mechanical integrity beyond any reasonably expected temperature or pressure excursion. This is an old but effective strategy to avoid leaks. However, it is not as inherently safe as substitution, intensification, or attenuation.

===Noise===
Noise may not seem like a process hazard when compared to explosions, but can cause permanent damage to hearing. Compressors, turbines, motors, and solids handling can be very noisy, both within the plant and in the surrounding neighborhood.

Sound is measured in decibels, defined by the following equation:

<math> SL = 20 \log_{10} \frac{P_S} {0.00002} </math>

where <math> P_S </math> is the root mean squared sound pressure and the result (SL) is a sound level in dB. It is advised to wear ear protection in areas over 80 dB, as permanent damage can be caused by noise over 85 dB (Towler and Sinnott, 2013).

=Process Hazard Analysis Tools=
==Exposure Evaluation==
At each stage of the process, every chemical, intermediate, and catalyst must be inventoried and analyzed. Risk can then be prioritized through a combination of chemical toxicity and exposure source (valve, pump, etc.). Exposure is highly variable, and should be measure over relatively large time period, longer than chemicals with long half-life. Finally, compliance with OSHA requires designer to make calculations of concentrations and exposure time of plant personnel during normal operation (Peters and Timmerhaus, 2003).

==MSDS==
Material Safety and Data Sheet - Every chemical has an MSDS which contains all the information regarding safe handling and how to deal with spills or other accidents involving the substance. Relevant information includes how to identify the substance, hazard information, and how to handle spills, fires, and exposure, among other things.

In process design, it is important to collect the MSDS of all components used in the process at as early a stage as possible in order to identify potential hazards that may arise later.

==Hazard and Operability Study (HAZOP)==
A HAZOP is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risk to personnel or equipment, or prevent efficient operation (Peters and Timmerhaus, 2003). HAZOP analysis is required by the following government regulations:
* USA OSHA 29 CFR 1910.119 [Process Safety Management Standard]
* USA EPA 40 CFR 68 [Risk Management Program]
* Regulations under the European Seveso Directive

[[File:Hazards 2.PNG|center|300px|frame|Figure 2. Flowsheet depicting general guidelines for how to do a HAZOP.]]

==Fault-Tree Analysis (FTA)==
Along with a reliability analysis, a fault tree analysis is a quantitative method to estimate the probability of an event based on known probabilities such as the probability of failure of an instrument.

In a FTA, designers form an event diagram that describes the routes by which a hazard may occur; Boolean algebra and component probabilities are used to determine overall probability of the hazard. The design can then be modified until desired hazard rate is achieved.

For example, imagine that you are tasked with performing a FTA on a pressure vessel. First, all of the possible causes of hazards associated with the pressure vessel are explored. These hazard sources are then analyzed to see how they dangerously affect the system, and then to see the final result if left unchecked. An example FTA is shown in Figure 3 below.

[[File:Hazards 3.PNG|center|500px|frame|Figure 3. Example FTA for Pressure Vessel (Cole, 2013).]]

==Failure Mode-and-Effect Analysis (FMEA)==
FMEA is an early stage approach to identifying critical technical risks using a semi-quantitative procedure. See the [[Process safety]] wiki page for more information.

=Conclusions=
In conclusion, the hazards described above are only a few of the hazards that can be present in chemical processes, and it is important that steps are being taken to mitigate these hazards at every stage of the design process, be it through FMEA, FTA, HAZOP, or other safety analyses. Proper safety hazard analysis will help minimize injuries and damage to the facility and environment, thus saving a company time and money, all while protecting the health of its employees.

=References=

Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997.

Cole JL. Chemical Engineering 351 Process Economics, Design, and Evaluation [Lecture Slides]. Evanston: Northwestern University; 2013.

Dugdale D. An Introduction to Fire Dynamics. New York: Wiley; 1985.

Peters MS, Timmerhaus KD. Plant Design and Economics for Chemical Engineers. 5th ed. New York: McGraw Hill; 2003.

Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Turton R, Bailie RC, Whiting WB, Shaewitz JA, Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 4th ed. Upper Saddle River: Prentice-Hall; 2012.

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:14:37Z

Jian: /* Storage */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning (Detroitmi.gov) and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 (US Department of Energy). Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve” (Airproducts.com).

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart (Sae.org).

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

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Drop-in Hydrogen Fueling (2014)

2015-03-02T04:14:01Z

Jian: /* References */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning (Detroitmi.gov) and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 (US Department of Energy). Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve” (Airproducts.com).

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart (Sae.org).

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

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Drop-in Hydrogen Fueling (2014)

2015-03-02T04:10:26Z

Jian: /* Emission Analysis */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning (Detroitmi.gov) and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 (US Department of Energy). Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve” (Airproducts.com).

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart (Sae.org).

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

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17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:09:57Z

Jian: /* Permitting */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning (Detroitmi.gov) and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve” (Airproducts.com).

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart (Sae.org).

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:09:21Z

Jian: /* Consumer Interface and Education */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve” (Airproducts.com).

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart (Sae.org).

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:08:09Z

Jian: /* Noise Analysis */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB (Airconco.com). Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB (Sengpielaudio.com), which is well below safety limits for long-term exposure (Airconco.com).

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 (Zoro.com).

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:06:26Z

Jian: /* Maintenance */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish (HyApproval WP2, 2008). If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

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Drop-in Hydrogen Fueling (2014)

2015-03-02T04:06:17Z

Jian: /* Maintenance */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 (HyApproval WP2, 2008).

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 (HyApproval WP2, 2008).

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

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17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:06:01Z

Jian: /* Operations */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary (HyApproval WP2, 2008). Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:05:18Z

Jian: /* Detroit, Michigan */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below (Trulia.com).

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:04:52Z

Jian: /* General Siting */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck (HyApproval WP2, 2008). The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:03:34Z

Jian: /* Failure Modes and Effects Analysis (FMEA) */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ (Asq.org) with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station (US Department of Energy, 2004; Hydrogencontest.org). From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

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Drop-in Hydrogen Fueling (2014)

2015-03-02T04:02:07Z

Jian: /* Safety Codes and Standards */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference (US Department of Energy, 2004).

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

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17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:00:56Z

Jian: /* Storage */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnott, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T04:00:20Z

Jian: /* Resource Analysis */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnot, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg (Towler and Sinnott, 2013a). Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T03:59:31Z

Jian: /* Safety Equipment */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnot, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens (Siemens.com, a) that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning (Siemens.com, b). It is estimated that these two units will cost approximately $4,100 (Siemens.com, a; Siemens.com, b; Hoodmart.com). If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 (Circuitbreakerguys.com). In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg [1]. Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T03:56:50Z

Jian: /* HVAC System */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnot, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity (Gwkent.com).

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen (Gwkent.com). Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously (Wastereductionpartners.org). Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens [17] that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning [18]. It is estimated that these two units will cost approximately $4,100 [17-19]. If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 [20]. In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg [1]. Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

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30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

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Drop-in Hydrogen Fueling (2014)

2015-03-02T03:55:31Z

Jian: /* Storage */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards (Towler and Sinnot, 2013b; The American Society of Mechanical Engineers, 2004). The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance (Cumalioglu, 2006). The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank (Keytometals.com; Alibaba.com).

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed (The American Society of Mechanical Engineers, 2004).

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures (Sakintuna, 2012).

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity [15].

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen [15]. Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously [16]. Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens [17] that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning [18]. It is estimated that these two units will cost approximately $4,100 [17-19]. If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 [20]. In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg [1]. Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

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18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T03:50:51Z

Jian: /* Storage */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity (Sandler, 2006; Couper et al., 2012). The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards [7-8]. The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance [9]. The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank [10, 14].

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed [11].

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures [12].

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity [15].

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen [15]. Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously [16]. Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens [17] that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning [18]. It is estimated that these two units will cost approximately $4,100 [17-19]. If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 [20]. In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg [1]. Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

33. "Compressed Hydrogen Surface Vehicle Refueling Connection Devices." J2600: Compressed Hydrogen Surface Vehicle Refueling Connection Devices. SAE International, 10 Oct. 2002. (Accessed 3/14/14).

Drop-in Hydrogen Fueling (2014)

2015-03-02T03:48:29Z

Jian: /* Compressor */

Authors: Matthew Ardagh, Michael Ashley, Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman (ChE 352 in Winter 2014)

Steward: David Chen, Fengqi You

Date Presented: Winter 2014

 

==Executive Summary==

With ongoing energy crisis, constant efforts are made to reach a sustainable energy. Major attention nowadays has been to shift the heavy demand of petroleum fuel to natural gas. Big effort has been made to make such a shift into a reality by making noticeable improvements in the fuel cell vehicle. To facilitate the shift, proper and reliable fueling station for fuel cell vehicle is essential.

The report proposes a design for a portable hydrogen station that can maximize the revenue and therefore facilitate a hydrogen fuel market. The stations can be installed in places where the demand is saturated. Also, when the demand falls low, the portable station can be transferred to different place where the hydrogen demand is higher.
The fueling module consists of a compressor, a storage vessel, a dispensing module, and necessary valving systems. The design is kept as minimalistic to minimize the capital cost yet enhance the portability. The site chosen was 2580 S Schaefer Highway in Detroit, Michigan. The site has commodious space of 280x100 ft. and necessary utilities and hookups available to support the designed station along with the car wash and/or oil change center. Despite the portability, the infrastructure will accommodate the state-of-the-art fueling dispensing features.

Economic analysis was made without accounting for the tax and restructuring cost. The initial cost of the actuating the design will cost $189,000 in initial capital cost. The sales revenue is estimated to be around $324,000; the annual cost amounts to be $296,355 per year. The income of a single station is $27,645 which will set the payback period to be 8 years.

==Introduction==

Around the turn of the 21st century, engineering and design were fundamentally changed with the advent of energy and environmental sustainability. With energy prices and harsher standards set by regulating organizations, the modern engineer emphasizes carbon footprint and sustainable design in developing new products and systems. One key technology that is now known to be unsustainable is petroleum, especially as used for automobile fuels. The rising cost of gasoline has motivated the investigation of alternative technologies, such as hydrogen, to be used to power automobiles.

The objective of this study was to design a mobile hydrogen refueling module for high-pressure hydrogen vehicles. The design was required to fulfill the following criteria:
*Dispense 5kg H2 gas in under five minutes
*Refuel vehicles up to 70 MPa
*Support two simultaneous refueling
*Support a 100kg/day demand, plus an additional 48 hours in the event of upstream equipment failure
*Mobile: able to disassemble and reassemble the entire process in under 7 days
*Fit inside a standard ISO container
*Capital investment that is a fraction of 2-4 million USD

[[File:Fig1-1.png]]

Figure 1 shows a capture of a 3-dimension scale model of the process, in its deployed form.

==Process Narrative==

To deliver hydrogen gas to vehicles, the fueling module requires the following equipment: a means to receive delivered hydrogen or capacity for generating it on site, a compressor capable of compressing the hydrogen to the requisite storage conditions, a storage tank, a dispensing system, as well as HVAC and utility equipment and safety equipment (Figure 2).

[[File:Fig2-1.png]]

Figure 2: contains a Piping and Instrumentation Diagram (P&ID) including all major process equipment and safety equipment.

===Hydrogen Delivery===

We currently recommend buying hydrogen as the main method for procurement of hydrogen by simply purchasing it from existing suppliers at market price. This will avoid capital costs of the upstream production units, which may lower the price of the hydrogen dispensed to clients. Currently, pressurized hydrogen may be purchased at a market price of roughly $7 per kilogram from existing suppliers with the added benefits of requiring fewer stages in the mobile fueling station compressor. In this case, the compressor would only require only two stages to supply hydrogen at the desired dispensing pressure, and so less time to move and construct the station itself. We currently desire to purchase hydrogen gas from a supplier of industrial gas, Praxair. Praxair’s primary method of delivery is by truck, so it will be ideal to choose locations close by Praxair distribution factories and major highways. Our design will allow our storage equipment to directly hook up to the delivery tank of Praxair and allow dispensing to occur.

Two alternatives were also explored for the procurement of hydrogen for the use in the mobile fueling station: steam reforming of methane and water electrolysis. However, these two alternatives are accompanied by significant capital costs, with steam reforming accompanied with complications with the mobility aspect of any ultimate design scheme.
Steam reforming of methane utilizes natural gas as a feedstock. Because natural gas is inexpensive, this is the most economically advantageous feedstock for gaseous hydrogen. The hydrogen produced in this manner would then need to be pressurized from atmospheric pressure to the desired dispensing pressures, which would also increase the stages of the compressor chosen to achieve the pressurization. This same problem arises in producing hydrogen through water electrolysis, where hydrogen and oxygen gas are non-spontaneously produced from pure water by a running current. In addition, reforming also runs the disadvantage of being relatively large and immobile. Also, although hydrogen is usually suggested as a sustainable fuel, steam reforming also produces substantial amounts of CO2, creating an irony to “sustainable fuel”. The size and CO2 production inherent in steam reforming discourages its use in our dispensing station.

The electrolyzer requires pure water as a raw material, which will require purification units upstream in the production process. The HG-50 generator offered by HGenerators is capable of producing the specified 200 kg of H2 per day if it is running at full capacity, 24 hours a day. Initial pricing of the HG-50 is estimated at $1.49 million. Operation of this electrolyzer system consumes 215 kWh per hour of operation (costing around $600 per day assuming the average price of electricity in the US at $0.13 per kWh) and 41.667 L of water (costing around $0.40 assuming an average price of electiricty at $1.50 per 1000 gallon in the US). The most favorable selling point of electrolysis is the fact that no carbon dioxide is produced, resulting in more truly clean energy assuming if the source electricity is not dependent on carbon sources. While production of hydrogen would be ideal in our dispensing station due to advantages of sustainability and not requiring additional utilities outside of water and electricity, it is not currently recommended. Due the incredible high capital, which takes up more than half of our intended budget of $2 million, it is not recommended for hydrogen production.

===Compressor===

To compress the hydrogen gas to the designated storage conditions, 1000 bar, from the delivered pressure of 200 bar, at least 2 stages of compression are required. Hydrogen gas may turn various metal brittle with prolonged exposure, known as hydrogen embrittlement; therefore, the compressor needs to be designed with caution (Towler and Sinnott, 2013a). Because of the low flow rate requirement, a reciprocating compressor may be used (Wikipedia.org). The advantages of the reciprocating compressor are a broad range of pressure ranges, easy maintenance, and relatively cheap price. The downside of the reciprocating compressor is that it generates loud noise.

A suitable compressor that meets above design specification was chosen from the vendor Hydro-Pac (Hydropac.com). A 20-hp compressor that are 94 inches long, 27 inches wide, and 52 inches tall will compress the incoming hydrogen of pressure 200 bar to 1000 bar and send it to the storage. The compressor has the adiabatic efficiency of 35% and generates the noise level of 95 decibels at 1- meter distance, which is under the legal limit. The cost of the compressor was estimated to be 95,000 dollars.

Had the hydrogen was supplied from the electrolysis generation method instead of purchasing directly from the vendor, the compression would require another compressor, intermittent storage, and additional piping systems, which altogether was quoted to be around 250,000 dollars from the same vendor, Hydro-Pac. Both the capital cost and the operating cost for the compressor phase will be higher for the generation method, which validate the decision to purchase the hydrogen directly from the vendor.

===Storage===

Once the hydrogen is brought to pressure, it passes into the primary storage tank. The storage conditions for the hydrogen gas were selected to be 100 MPa, and -70˚C for the following reasons: 100 MPa ensures that the tank can maintain a sufficient pressure differential to increase the speed at which is filled, and -70˚C ensures that upon expansion, the hydrogen gas is at a temperature range that complies with dispensing guidelines outlined in SAE J2601.

The design specification stated that the refueling module needs to be able to dispense 100kg of H2 fuel per day, with an additional 48 hours supply in event of compressor failure. In the event that the compressor fails before recharging the tank from dispensing its initial 100kg, the tank was therefore designed to have a deliverable capacity of 300kg.

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:

[[File:Eqn1.png]]

In order to successfully fill an automobile’s fuel tank to full capacity, a minimum tank pressure of 70Mpa is required. Therefore the following equation was solved to determine the capacity of the tank:
Where M is the total gravimetric capacity of the storage tank, is the gravimetric density of hydrogen gas at the specified storage conditions of 100MPa and -70˚C, and is the gravimetric storage capacity at 70MPa and -70˚C. The density was calculated using the Peng-Robinson Equation of State [4]. M was determined to be 1568.25kg, and the corresponding minimum volume was found to be 25m3.

One safety concern was loss of temperature control of the storage tank, and the resulting over pressurization of the storage tank. To accommodate this, a safety factor in the volume of the tank was designed, so the final volume was 26.5m3.

Common engineering practice is to fix length to diameter ratio of a high pressure storage tank to 1:5, and to use a horizontal storage tank for volumes of this capacity [5-6]. The corresponding inside diameter and height of the tank were determined to be 1.9 and 9.4 meters respectively.

The tank was then designed according to ASME BPV Section VIII standards [7-8]. The tank will be multilayered with three 5cm layers, manufactured out of A203 stainless steel for low temperature tolerance [9]. The heads of the tank are torispherical, with all welds spot checked. The tank will include a pressure and temperature sensor.

The tank will be coated with a thermo-regulating jacket which will have coolant from the HVAC pass through it as part of the refrigeration loop.

A detailed cost estimate was not obtained due to reluctance of vendors to generate a quote for this complicated tank for a student design competition. However, based on heuristics and comparisons to existing tanks, with some extrapolation, a cost estimate on the order of $100,000 was used in determining the capital investment associated with the storage tank [10, 14].

Much of the cost associated with the storage tank is due to the challenging storage conditions of -70 ˚C and 100 MPa. A number of alternatives were considered.

The first alternative was to use a metal hydride to chemisorb the hydrogen gas at low pressure. However, it was determined that metal hydride technologies are not mature enough to meet the storage needs of this project, primarily due to the high heat of adsorption; the adsorbate binds too strongly to the hydrogen and requires heating to drive the gas off when the gas is needed [11].

The second alternative considered was to use a Metal Organic Framework (MOF) as an adsorbate. The principal is similar to metal hydrides, but MOFs utilize physisorption instead of chemisorption to bind the hydrogen. For this reason, it suffers from the opposite setback, in that while MOFs can adsorb hydrogen at 77K, they do not perform well at higher temperatures [12].

The main benefit of using an adsorbate is the elimination of the compression stage, which constitutes the largest capital investment and most energy intensive step of preparing hydrogen for fuel conditions. Therefore, these adsorbate technologies make more sense as an onboard storage solution, and as current vehicles do not use these technologies, there is no gain to bypassing the compression stage. Therefore, the final decision to use high-pressure storage was made.

===Dispensing System===

Hydrogen fuel is dispensed to the consumer’s vehicle from the high-pressure storage tank via a system of three adiabatic expansion valves and three bypass valves. These are required by the J2601 standard, which stipulates that the pressure at the nozzle be no more than 20 MPa above the pressure of the vehicle’s tank. By selective expansion the fuel through either expansion or bypass valves, the hydrogen stream is reduced to a safe pressure for fueling. Additionally, since the storage tank is maintained at -70ºC, the fuel stream will heat up to -40ºC during expansion, providing pre-cooled hydrogen as recommended by J2601 and this contest.

===HVAC System===

The HVAC system will primarily serve to maintain the extreme cold required to properly store the gaseous hydrogen. This system will use GW Kent’s 10 ton Glycol Chiller, 3 Phase to circulate refrigerant R-22A (which is built-in upon purchase) through a jacket lining the main hydrogen storage unit and the pipes that send hydrogen to the dispensing units. Built for outdoor industrial processing needs, this chiller contains a stainless steel pump and insulated poly tank built into a single cabinet. It is designed to properly cycle such that the compressor runs only when necessary in an effort to conserve energy. Installation will only require water in, water out, and a single point connection to electricity [15].

The refrigerant associated with this HVAC unit removes 120,000 BTU/hr from its target, in this case the pressurized hydrogen [15]. Based on our heat duty calculations, this will require 0.4 m3 (or 400 kg) of R-22A. And, considering a typical HVAC efficiency 0.83 kW/ton (where a ton represents 12,000 BTU/hr), this system will require 8.3 kW to run continuously [16]. Accordingly, it will have the capacity to keep the compressed hydrogen at -70˚C.

===Safety Equipment===

The module incorporates the Sinorix™ Waterless Fire Extinguishing system from Siemens [17] that will be installed both in the canopy roofing the dispensing station as well as in the box that houses the main storage tank. This system has proven its ability to suppress a fire before it becomes large enough to warrant the activation of a traditional sprinkler system. Additionally, the Cerberus PRO fire alarm system from Siemens will be installed to serve both as an acoustical and visual warning [18]. It is estimated that these two units will cost approximately $4,100 [17-19]. If the electrical wiring system begins to contain too much current flowing through it (thus showing warning signs of shorting out), a Siemens Q330H circuit breaker will be connected to the system. It operates at 240 V and up to 30 A, and will cost approximately $100 [20]. In addition, lighting will be provided for hydrogen delivery at night as well as locks to access storage equipment.

==Economic Analysis==

===Results===

The primary financial measures of the success and feasibility of this project are whether the project will meet the 10-year payback period and the $2MM capital cost limit imposed by the contest. This proposal meets both of these criteria, costing only $189,000 in initial capital and paying back this initial investment in 8.0 years.

===Discussion===

The initial capital investment is limited to equipment and installation costs. The payback period is obtained by dividing this investment by the Net Income (NI), which is the sales revenue, less all costs. Direct costs of this proposal include to the cost of purchasing hydrogen and electricity usage of our equipment, while indirect costs include fixed yearly expenses such the rent on the station’s land and maintenance expenses. Sales revenue is estimated to yield $324,000, while annual costs amount to $296,355 per year. Thus, the yearly income of a single station is $27,645 (an ROI of 12.5%), and the payback period is 8.0 years.

===Assumptions===

For simplicity, this analysis ignores all taxes, restructuring costs, and other accounting complications, and thus Net Income is equal to Operating Income. This analysis also assumes the station sells 100 kilograms per day and operates 360 days per year. Because the gross profit is relatively low in magnitude, it is assumed that a corporation entering the hydrogen fuel market will construct this station, and only in areas where the consumer market is saturated.

==Safety==

Safety is an important aspect of our hydrogen dispensing station and care is taken to ensure the safety of our consumers and prolonged operation of our equipment. We will consider relevant codes and standards, identify potential risks with Failure Mode Analysis (FMEA), and derive appropriate safety procedure to mitigate risks.

===Safety Codes and Standards===

Safe operation and accident prevention are one of the primary objectives for design of hydrogen dispenser. In order to facilitate this objective, the safety codes and standards listed in the table below will be used to minimize injury to consumers, equipment, and infrastructure. The following safety considerations listed in this section will be our methods of adhering to the codes and standards to ensure the safety of our customers and equipment. A more exhaustive list of codes and standards can be found in reference [21].

[[File:Table1.PNG]]

===Failure Modes and Effects Analysis (FMEA)===

The Failure Mode and Effects Analysis (FMEA) is an important analysis tool to help identify areas of risk in a process. The template for the following FMEA comes from ASQ [22] with the information from the actual analysis derived from other FMEA analysis on fuel dispensing station [21,23]. From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station.

[[File:Table2.png]]

===Safety Strategies for Risk Mitigation===

From our FMEA, we have identify considerable high risk areas associated with the storage equipment and dispensing station. Using the appropriate codes and standards, we have derived the following safety strategies. To prevent single-point failure, we aim to provide redundancy in our safety equipment to further minimize risk.

Hydrogen quality either purchased or produced will follow CGA standards for commercial specification to fuel grade hydrogen and prevent fuel cell damage. Storage and piping will adhere to ASME standards for pressure vessels and piping. Pressure and temperature will be monitored using sensors installed on all storage and piping equipment. Storage tanks will be designed to prevent pressure from rising 10% above maximum working pressure. In the event of overpressurization, a pressure relief device consisting of a frangible disk to a relief valve. Adhering to CGA G5.4, NFPA 50A chapter 2, NFPA 50 B chapter 2, pressure relief valves will be installed for all systems with the potential of overpressurization. Vents will point towards where hydrogen cannot be trapped as well as withstand ice, wind, and seismic variations. Storage devices will separated 20 ft away from dispensing station and separated with a 5 ft high fire barrier. Storage vessels will be open-top to minimize accumulation of hydrogen. The location of the dispensing station will not be beneath power lines and far away from other flammable and/or sparking material. Flammable gas detectors will be located near pipe/storage junctions to set off alarms at 1% hydrogen using visual and audio recognizable alarms to warn consumers of possible hydrogen leaks.

Safety code relating to distribution will hold similarities with more common and established gasoline dispensing stations. Breakaway mechanism will be incorporated into the hose to prevent unrestricted hydrogen leakage in the event the dispensing equipment is still attached to a vehicle when the vehicle leaves the station. A maximum of two cars will be allowed into the dispensing station. Hydrogen sensors will be installed around the station to alert possible possible hydrogen leakage. Sensors will go off if it reaches to above 4% of lower flammable limit of air. In addition, "NO SMOKING, NO OPEN FLAMES" will be clearly displayed to minimize potential fire hazards due to consumers. Compressed hydrogen storage will be locked to minimize tampering of non-consumer equipment. The user interface equipment will also instruct consumers to safe areas away from the dispensing station during emergencies.

In addition, all communication between site and operation headquarters will be encrypted with RSA cryptosystem to prevent cyberattacks. Transportation of hydrogen will follow ASME and DOT codes. In case of emergencies, first responders and NVFEL personnel will be contacted for containment and removal.

== Siting, Permitting, and Maintenance Codes==

=== Siting===

==== General Siting ====

During the initial search for the fuel station site, a review of the pertinent literature was performed. There are strict regulations concerning the local zoning requirements, transport of hydrogen to the site, and transfer to the station from the fuel truck [24]. The route to the site must not impede hydrogen shipment, so locations near major highways and larger thoroughfares were preferentially considered. Additionally, there needs to be room at the site for the truck to position and unload hydrogen. The only production equipment with major required safety distances is the high pressure gas storage system. These tanks need to be at least 25 feet from neighboring buildings that do not have sprinkler systems1.

==== Detroit, Michigan====

Following the rules outlined in the general section, the site chosen was 2580 S Schaefer Highway in Detroit, Michigan. This lot is fairly large, 280x100 ft., and has the hookups available to support a car wash and/or oil change center (therefore, water and electricity systems can be used here). The initial capital investment here is substantial at ~$80,000, but insignificant compared to the total cost incurred from the compressors and the high pressure storage tanks. An idea of the surrounding area can be seen in the snapshot below [25].

[[File:Fig5-1.png]]
Figure 3. Proposed Site for Hydrogen Fueling Station

It can be inferred from Figure 3 that the fueling station will be highly accessible to both customers and suppliers alike. Being only 1-2 miles off a major expressway, Interstate 75, consumers will be able to find the location easily. Because this lot is on the corner of Schaefer Hwy, there should be room to accommodate fueling operations regardless traffic and congestion.

=== Permitting ===

Commercial construction requires adherence to the building permit checklist produced by the Buildings & Safety Engineering Department (BSED) of Detroit, MI. First, the design must meet zoning [26] and construction codes (Building, Residential, Mechanical, Electrical, Plumbing, and Uniform Energy codes). A Building Permit Application, which includes the project location and description, property legal description and owner information, our personal information, and notarized signatures of both our organization and the owner, must be prepared and submitted. The major sections of the construction document are the site plan, architectural plan, plumbing and mechanical plan, electrical plan, and structural and detail drawings.

==== Site Plan====

*Address of our hydrogen fueling station
*Size and shape of the lot with property lines identified and all buildings and structures shown
*The distances between these components
*The infrastructure of our utilities systems

====Architectural Plan====

*Building information block noting the area of each building and their capacities, specifications on sprinklers, fire alarms, exits
*Detailed floor layout with equipment, dimensions of the rooms, all doors and windows, and heights of all the walls
*Location of restrooms

====Plumbing and Mechanical Plan====

*Complete floor plan of the mechanical layout, including ductwork, ventilation system (and associated mechanical calculations), etc.
*Floor plan showing restrooms, sinks, water closets with plumbing isometric drawings
*Roof and site drainage calculations
*Gas pipeline isometric drawing

====Electrical Plan====

*Locations of the Service Connection and each sub panel
*Lighting floor plan, power floor plan showing switches, outlets, etc.
*Drawing of the complete electrical system, including the service voltage, ampacity, phases, and overcurrent devices, maximum available fault current, sizes and types of wire, with grounding detail
*Exterior lighting plan
*Size of main breaker
*Location of any hazardous areas

====Structural and Detail Drawing====

*Foundation, floor framing, roof framing plans
*Cross-sectional views
*Connection details, calculations, soils report
*Wall details
*Material list for finishes
*Door and window schedules
*Hardware schedule

==Operations and Maintenance==

===Operations===

At this stage of the design process, specifics about the operation of individual process equipment are unnecessary. However, the general plan for training the remote operator is critical. Technical training concerning the potential hazards of hydrogen, safety regulations, and emergency procedures is necessary [27]. Once specific vendors are selected, detailed operating instructions will be provided based on the operating manual and industry best practices.

===Maintenance===

Due to the lack of on-site personnel, active preventative maintenance will be crucial to ensure safe operations. Since there are strict flammability concerns, the facility grounds must be free of debris, weeds, and other rubbish [27]. If there is grass near the site, it must be regularly cut to prevent the accumulation of rotting grass, which is capable of self-ignition. In terms of process safety, the flexible fueling hoses appear to be the most probable hazard1. Therefore, preventative maintenance in this area will require high scrutiny. Based on initial studies done prior to establishing hydrogen fueling stations in Europe, a sample maintenance plan can be seen in Table 1 [27].

Table 1: Proposed Maintenance Plan for High Pressure Fueling Station

[[File:Table3.png]]

Because the high pressure compressors are the main wear pieces in the fueling process, great care needs to be taken. The contents of the stated overhaul modes are shown in Table 2 [27].

Table 2: Inspection Plans for Dispensing Compressors

[[File:Table4.png]]

== Environmental Analysis==

One of the principal driving forces for using hydrogen fuel cells is the fact that byproducts of the energy-producing step are just water, eliminating the emission of carbon-based greenhouse gases. However, it is important to perform an environmental analysis of the process to ensure that the entire process of using hydrogen gas for fuel is superior to other technologies. Resource consumption, emissions, and noise were analyzed to determine the environmental impact of this process.

=== Resource Analysis===

In order to transform the feedstock hydrogen into fuel condition hydrogen, this process consolidates all of its resource needs into electricity drawn from the local electrical grid. In this section, the thermodynamic efficiency for each piece of process equipment, as well as the overall process efficiency are calculated.

To determine the overall efficiency of this process, an energy balance was performed on each module. The general form of an energy balance is shown below:

[[File:Eqn2.png]]

where i refers to the inlet, o refers to the outlet, indicates a mass flow rate and refers to the enthalpy per unit mass, Q is the rate of heat transfer, and W is the work performed on the system. Because the equipment operates in steady state, . Table 3 contains the values that were used in performing this calculation across each piece of process equipment, with enthalpy, Q and W values determine using the Peng-Robinson equation of state implemented in AspenTech HYSYS Process Simulation software, with inlet and storage conditions as stated above. The outlet conditions were assumed to be -40 degrees C, 200bar, as this is the largest temperature gradient that will be experienced during dispensing, and therefore maximizes inefficiencies.

Table 3: Energy Balance Values

[[File:Table5.PNG]]

All values of heat transfer rates are ultimately turned into work done by the HVAC unit, which has an efficiency factor given by the manufacturer.

The efficiency of a given piece of equipment is given by the following expression:

[[File:Eqn3.png]]

where D is the duty of the process equipment, either as work or heat transfer, required to produce one kg of fuel grade H2 gas. The efficiency of each piece of equipment can be found in Table 4.

Table 4: Energy Balance Values

[[File:Table6.PNG]]

The total process efficiency factor is the total energy used to produce a single kg of H2 fuel divided by the minimum energy required by thermodynamics, or the following:

[[File:Eqn4.png]]

The value of η was determined to be 1.5.

Finally the total energy requirement to produce one kilogram of hydrogen fuel at dispensing conditions was found to be approximately 19,500kj. The energy density of hydrogen gas was found to be 120,000 kj/kg [1]. Based on this value, the process efficiency was calculated as the usable energy per kg of hydrogen divided by that value plus the processing energy as shown below:

[[File:Eqn5.png]]

ε was found to be 0.86.

=== Emission Analysis===

Following the design decision to deliver hydrogen to the fueling station from outside sources, emissions analysis was conducted using the centralized hydrogen production document from the US DoE hydrogen analysis1. The state of the art technology for large companies in this field is to produce hydrogen using coal gasification followed by catalytic reforming. A second water gas shift reactor is used to convert remaining water to hydrogen (and carbon monoxide to carbon dioxide) 1. A significant amount of the carbon dioxide produced is sequestrated before the hydrogen stream is compressed for delivery.

The DoE analysis was performed to include estimates for downstream energy costs at the hydrogen fueling station. Their final calculated values can be seen in Table 5, and significant discrepancies between their analysis and our design plan are detailed below.

Table 5 [28]. Well to Wheels Energy and Greenhouse Gas (GEG) Data

[[File:Table7.PNG]]

It should be noted that the basis used in these calculations was for a 350 bar fueling tank. Therefore, the total energy use and GEG emissions are slight underestimations, because additional work is needed to compress the gas to 1000 bar during storage and 700 bar during fueling. Here, 85% of carbon dioxide produced during hydrogen production was assumed to be sequestered. This appears to be overly optimistic for most large scale firms; so again, the GEG emissions shown here are likely a significant underestimate.

=== Noise Analysis===

The major sources of noise produced by this process are the compressor, the HVAC unit, and the expansion valves in the dispenser unit.

Of these three pieces of equipment, the compressor is the loudest, with a high-end estimate of 95dB at a distance of 1 meter from the equipment. A high-end estimate for the sound output of an industrial strength cooling unit is 70dB [29]. Adding these two sound signals together results in a total output of 95.04dB. This justifies neglecting all sound output relative to the compressor.

Because sound energy dissipates proportional to the distance from the source cubed, and other safety requirements require a minimum of 8 meters separation between users and the sound source, no users are in immediate danger. A rule of thumb for calculating sound reduction is that sound reduces by 6dB per doubling of distance between the source and observer. Therefore, at 8 meters, the sound of the compressor would be reduced to 77dB [30], which is well below safety limits for long-term exposure [29].

To further reduce noise for the benefit of neighbors to the process, a low cost sound containment wall that will reduce the noise output by 20dB across the 2” barrier can be purchased for under $1000 [31].

Therefore, with appropriate sound containment equipment installed, noise pollution is not anticipated to be a concern.

== Consumer Interface and Education==

The hydrogen fuel dispenser is not a novel apparatus; in fact many companies have developed their own hydrogen dispensers to be used specifically in hydrogen fueling stations such as the one designed and proposed in this report (Figure 7-1). These dispensers have been designed to mimic the conventional consumer experience at the “gas station” as closely as possible in order to maximize consumer comfort in incorporating the new technology and minimize a possible “learning curve.” [32]

=== Fuel Dispenser Visual Interface===
In view of these efforts, however, certain aspects of the consumer experience at the hydrogen fueling pump will be intrinsically different as a result of the nature of hydrogen fuel. Firstly, it is the industry standard that hydrogen fuel loaded be reported on fueling apparatuses in kilograms and its price in dollars per kilogram; having the units be the conventional gallons and dollars per gallon as seen with gas stations would not only burden suppliers but also consumers. Furthermore it is of importance to note that the hydrogen fueling pump is a closed process – specifically, the dispensing nozzle needs to be attached to the consumer vehicle in a matter which is not open to the atmosphere and meets a long list of standardized requirements, unlike its “gas station” counterpart. [33]

[[File:Fig7-1.png]]
Figure 4: Air Products hydrogen fueling pump.

Due to the nature of hydrogen fuel, fuel grade is no longer of relevance to the consumer experience. This is the case because hydrogen gas is the energy carrier to be utilized by all vehicles and no additives are included in the gas supplied to consumer vehicles. Additionally, due to the mobile and unmanned nature of the fueling station proposed in this report, the option of a car wash, which would also impact the per-kilogram price of hydrogen fuel, is also not planned to be available to the consumer. All of the mentioned changes to the conventional fueling station experience will be reflected in the customer visual interface by way of additional instructions, or lack thereof, for the case of nozzle fastening and car wash availability respectively (see Appendix B).

=== Consumer Education Strategy===

To further enhance existing consumer education efforts in preparation for the eventual widespread incorporation of hydrogen fuel for consumer transportation needs, a tri-fold brochure design was created. The brochure incorporates information about hydrogen fuel and its potential for the future and a special effort was made to keep the publication-ready brochure as purely educational. This means that no propagandizing about hydrogen fuel was allowed – all information was provided in a balanced and factually sound manner, with reputable sources being the only sources acceptable for the ask and cited properly on the brochure itself (see Appendix C).

The tri-fold brochure is to be strategically located in places where consumers will have sufficient time to invest to reading the brochure and learning from it. For drivers of all ages, the Department of Motor Vehicles offices would be ideal locations to stock with hydrogen fuel informational brochures such as the one designed. For young and soon-to-be drivers, the brochure would be made available at the driving schools consumers of the age group are required to attend and also high schools which are capable of instructing their own driving courses.

==Appendix A: Calculation Calculations==
[[File:AppA.PNG]]

==Appendix B: Pump and Interface Touch Screen Display Logic==
[[File:AppB-1.png]]
[[File:AppB-2.png]]
[[File:AppB-3.png]]
[[File:AppB-4.png]]
[[File:AppB-5.png]]
[[File:AppB-6.png]]

==Appendix C: Hydrogen Fuel Brochure==
[[File:AppC-1.png]]
[[File:AppC-2.png]]

==References==

1. Towler, G.; Sinnot, R. “Chapter 9: Safety and Loss Prevention” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.
2. "Hydrogen Embrittlement." Wikipedia. Wikimedia Foundation, 15 Mar. 2014. Web. 15 Mar. 2014. http://en.wikipedia.org/wiki/Hydrogen_embrittlement. (Accessed 3/15/14).

3. "High Pressure Hydrogen Compressors." High Pressure Hydrogen Compressors. N.p., n.d. Web. 15 Mar. 2014. http://www.hydropac.com/HTML/hydrogen-compressor.html. (Accessed 3/15/14).

5. Sandler, S. Chemical, Biological, and Engineering Thermodynamics, 4th ed.; John Wiley and Sons: Hobeken, 2006.

6. Couper, K.; Penney, R.; Fair, J.; Walas, S. Chapter 0: Rules of Thumb Summary, Chemical Process Equipment: Selection and Design, 3rd Ed.; Elsevier: Boston, 2012.

7. Towler, G.; Sinnot, R. “Chapter 14: Design of Pressure Vessels” Chemical Engineering Design, 3rd Ed.; Elsevier: Boston, 2013.

8. ASME Boiler and Pressure Vessel Code Section VIII. (2004). Rules for the Construction of Pressure Vessels. ASME International

9. Cumalioglu, Y.; Ma, E.; Maxwell, T. High Pressure Hydrogen Storage Tank: A Parametric Study J. Pressure Vessel Technol. 129, 216-222 (2006) (7 pages); doi:10.1115/1.2389036

10. Total Materia. “Steels for Cryogenic and Low-Temperature Service” http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&NM=61, (Accessed 3/6/2014).

11. FuelCellStandards.com “American Society of Mechanical Engineers Boiler and Pressure Vessel Code” http://www.fuelcellstandards.com/BPVC.htm. (Acessed 3/12/2014)

12. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review International Journal of Hydrogen Energy. 2007, 32, 1121-1140.

13. Sculley, J; Yuan, D.; Zhou, H.; The current status of hydrogen storage in metal-organic-frameworks updated. Energy and Environ. Sci., 2011, 4, 2721-2735.

14. Alibaba “Hydrogen Storage Tank” http://www.alibaba.com/showroom/hydrogen-storage-tank.html. (Accessed 3/12/2014).

15. GW Kent. “10 ton Glycol Chiller 3-Phase.” http://www.gwkent.com/10-ton-glycol-chiller-3-phase.html (Accessed 3/7/2014).

16. Waste Reduction Partners. “Chillers: Energy Saving Fact Sheet.” http://wastereductionpartners.org/phocadownload/userupload/Resources/Energy_Saving_Fact_Sheet_Chillers.pdf (Accessed 3/7/2014)

17. Siemens. “Fire Suppression Systems.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-suppression-system/Pages/fire-suppression-system.aspx (Accessed 3/7/2014)

18. Siemens. “Cerberus PRO – An Intelligent Fire Protection System.” http://w3.usa.siemens.com/buildingtechnologies/us/en/fire-products-and-systems/fire-alarm-systems/cerberus-pro/Pages/cerberus-pro.aspx (Accessed 3/7/2014).

19. HoodMart. “Restaurant Fire Suppression Systems.” http://www.hoodmart.com/restaurant-fire-suppression-system-pfs19.aspx?utm_medium=shoppingengine&utm_source=googlebase&gclid=CIrkm5nHgb0CFeZDMgodq38ASA#.UxpTaF5kLGo (Accessed 3/7/14).

20. Circuit Breaker Guys. “Q330H.” http://www.circuitbreakerguys.com/q330h/?gclid=CM_P2pbJgb0CFbFaMgod_hUAIw (Accessed 3/7/14).

21. http://www.pnnl.gov/fuelcells/docs/permit-guides/module2_final.pdf

22. "Failure Mode Effects Analysis (FMEA)." - ASQ. http://asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html. (Accessed 3/15/14).

23. 2011 Winners of Hydrogen design contest; University of Waterloo, University of California – Riverside, Imperial College London

24. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

25. Trulia. http://www.trulia.com/property/1033919029-2580-S-Schaefer-Hwy-Detroit-MI-48217 (Accessed 3/15/14).

26. Detroit, Michigan Building Permits. “Building Codes/Construction Information: Commercial Building Permit/Submittal Checklist.” http://www.detroitmi.gov/DepartmentsandAgencies/BuildingsSafetyEngineeringEnvironmental/Divisions/LicensesPermits/Permits.aspx (Accessed 3/6/2014)

27. HyApproval WP2. Handbook for Hydrogen Refueling Station Approval. Prepared during June 2008.

28. US Department of Energy. Centralized Hydrogen Production from Coal Gasification with Sequestration.

29. Air Conoco. “Decibel Scale—Amacing Decibel Infographic” http://www.airconco.com/decibel_scale/, (Accessed 3/5/2014)

30. http://sengpielaudio.com/calculator-distance.htm, (Accessed 3/5/14).

31. http://www.zorotools.com/g/00060581/k-G2499777?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CPmd_MG9_LwCFaw-MgodQzYAHQ, (Accessed 3/5/14).

32. "News Release: Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser." Air Products Introduces Advanced Retail Hydrogen Fuel Dispenser. Air Products, 11 June 2013. Web. (Accessed 3/15414).

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Design S1

2015-02-28T22:44:46Z

Jian: /* Appendix 10 */

Design Report Authors: Michael Gleeson, Thomas Considine, Sean Kelton

Steward: Fengqi You

Date Presented: March 11, 2014

 

==Executive Summary==
The Chemical Intermediary Division ($1) of Evanston Chemical Corporation is interested in evaluating the economic benefit of adding 1,4 Butanediol (BDO) to its already robust offering of chemical intermediaries. It plans on producing 50,000 tonnes of 99.5%wt BDO using a modified Davy Process through a Gas Liquid Induction Reactor (GLIR) with a rare earth metal catalyst. The facility will be located in Lake Providence, LA , due to proximity to raw material productions sites and ease of transportation of the final product.

BDO is produced from Succinic Acid (SUC) by a hydrogenation reaction at very high pressures. This particular process uses a rare earth catalyst to because of the high conversion of SUC and the high selectivity toward BDO. Side products of the reaction include the highly valuable chemicals tetrahydrofuran (THF) and γ-butyrolactone (GBL), as well as water, n-butanol, and various other low value chemicals. The reaction occurs at 165oC and 150 bar, so special attention must be paid to reactor design to account for these extreme conditions.

Aspen HYSYS was used to model this process, and equipment sizes were calculated as specified by Towler. Equipment costs were estimated using Aspen Process Economic Analyzer (formerly known as Icarus). In order to meet the process specifications within the given time-frame, some simplifying assumptions were made that impose limits on the accuracy of the model; specifically, the GLIR was modelled using a conversion reaction. This means that the conversion remained unchanged at unideal operating conditions, which, clearly, is inaccurate. Additionally, only one reaction was modelled; in real world conditions, dozens of reactions would occur within the reactor, which would have a potentially massive effect on the accuracy of this model. Despite these limitations, the possibility of producing BDO for sale in the open market should be investigated because of the extremely encouraging economic potential of this endeavor.

Economic analysis of this process indicates a 10 year NPV of $163M, a 20 year NPV of $258M, and a total capital cost of $17.5M. The variable operational costs are approximately $131M. At a selling point of $3/kg for BDO and $35/kg for GBL, the total revenue will exceed $190M/yr, so it is strongly recommended the ECC pursue this opportunity.

==Introduction==
===Project Justification===
1,4 Butanediol is an important organic chemical used mainly as an intermediate for the production of Tetrahydrofuran (THF), Gamma-Butyrolactone (GBL) and Polybutylene Terephthalate (PBT). In 2011, the global market for BDO reached 1,725.0 kilo tons. Current projections suggest that worldwide BDO consumption will grow to 2550 kilo tons by 2017. The Technology Division of Evanston Chemicals has requested a preliminary design and economic evaluation on the feasibility of producing 1,4 Butanediol from a biomass derived succinic acid.

===Technology Review===
BDO can be produced by hydrogenation of succinic acid in the presence of a catalyst, at high temperatures and pressures (approximately 150-200°C and 20,000 kPa). However, to the best of the authors’ knowledge, there does not exist a means to produce only BDO. Instead, a mixture of THF, GBL, and BDO is produced. The choice of catalyst is the major factor in controlling yields and selectivity of a certain product. Current research suggests that bimetallic catalysts have a stronger activity and lead to higher conversion to BDO. TiO supported 2%Pd/X%Re catalyst and Carbon supported 2%Ru/4%Re catalyst both have been shown to be particularly effective. It is interesting to note that both catalysts contain Re. Research suggests that the synergy between Re and Pd/Ru leads to higher selectivity for BDO. Additionally, the chosen catalyst for this study was a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5 mm carbon support. Taken from an ISP Investments patent from 2011, this catalyst has exceptionally high yields, upwards of 99.7% conversion of succinic acid, as well as high yields of BDO. In total, the percentage conversions of succinic acid to various products are:
BDO: 85.51 wt %
GBL: 2.04 wt %
THF: 9.28 wt %
Butanol: 2.87 wt %
The lifetime of the catalyst is approximately 5 years. Furthermore, multiple reactor types have been discussed in the literature, including CSTRs and PFRs. However, the literature also shows that gas liquid induction reactors are the best for hydrogenation reactions in industry. They are preferred for their safety with respect to explosive gas phase reactants and complete utilization of the gas phase reactant; being especially useful for expensive inputs. These reactors use energy efficient impellers for gas induction and dispersion along with special recovery equipment to prevent waste of the gas phase, thus GLIR was chosen for this study.

===Design Basis===
The plant has been proposed to be built in Lake Providence, Louisiana. This is due primarily to its proximity to suppliers of succinic acid in the south east region, as well as close to distributors by way of the Mississippi River and the Gulf of Mexico. Additionally, the plant has been designed to have a capacity of approximately 50MM kg/yr of BDO production. This will require feeds of compressed hydrogen gas, and an aqueous feed of water and succinic acid, in a 50/50 wt % composition.

==Technical Approach==
The primary tool used to model the plant process was Aspen HYSYS. Because of the non-idealities involved in the NRTL HYSYS fluid package, an additional fluid package was created in Aspen. Additionally, the GLIR reactor chosen was modeled as a conversion reactor. Selectivity and yield of the reactor was modeled based off the specific data from the ISP Investments patent (discussed in Introduction: Technology Review). Although this provided very accurate modeling, the operating pressure and temperature were required to be held constant. This prevented any optimization within the reactor with respect to these operating conditions. The distillation columns were modeled as fractional distillation columns, with bottoms or distillate flow rate, and component recovery as active constraints. Additionally, Aspen Energy Analyzer was used to create the heat exchanger network, which can be seen in the Appendix. The economic analysis was performed in Aspen ICARUS.

[[File:Hysys.JPG]]

Figure 1. Screenshot of Aspen HYSYS process simulation.

As mentioned above, this plant will produce technical grade BDO and GBL, but the THF stream will be treated as waste. Originally, attempts were made to purify the THF stream in order to sell it; this process produces approximately 5M kg/yr, and at a selling point of ~$3.00/kg, this would generate an additional $15M/yr in revenue. However, the stream containing THF also contains water and n-butanol. As shown in Appendix XX, THF and water have a pressure dependent azeotrope; Figures XX1 and XX2 show that the azeotrope can be broken by pressurizing the stream after initial separation and atmospheric pressure. However, the presence of n-butanol makes separation of THF and water impossible; butanol and water have a tight azeotrope that cannot be broken simply by pressurizing the stream. Instead, absorption or ion exchange must be used to purify the stream. After extensive efforts were made to purify the THF, it was decided that the undertaking would not be profitable. In future iterations of this project, redoubled efforts would be made to force separation of THF to generate large revenues.

===Process Description===

There are three main component of our process: pre-treatment, reaction and separation. See Appendix 15 for a detailed PFD of the process to reference.

===Pre-treatment Phase===

In the pretreatment phase of our process we bring all of the components to the correct conditions in order to be fed into the reactor. For example the 50% succinic acid in water feed in pumped to a pressure of 3250 psia and then heated to about 160oC, which are the operating conditions of the gas-liquid induction reactor used in the process. The operating temperature is relatively low in order to promote selectivity toward BDO and prevent other side reactions. At higher temperatures the hydrogenation of succinic acid continues past BDO and creates unwanted products. See Appendix 14 for the full reaction scheme of this process. At this point the feed can be mixed with a recycled steam coming off of our second gas-liquid separator, which is composed of water, BDO and BGL. It was advantageous to combine these two steams entering the reactor because the recycle stream saves excess water that was separated out before the final product and further dilutes the succinic acid concentration, for stabilization purposes, within the feed stream. Furthermore, the excess BDO that is filtered out and would be lost is recycled back into the system to improve the system recovery. Finally the GBL can be further reacted in the presence of hydrogen in order to form BDO, or once again recovered at the end of the process to be purified and sold rather than wasted. Of course the recycled stream must be pressurized and heated to the correct conditions as well, however, we first cool the recycle stream to form a liquid so that it can be pumped to the correct pressure of 3250 psia (rather than compressed as a gas, since compressors are much more expensive) and finally heated back to a temperature of 160oC.
On the other side of the GLIR the hydrogen feed enters the process. Hydrogen purchased at 3000 psia is compressed to 3250 psia and then mixed with recycled hydrogen coming off the top of our first gas-liquid separator. The hydrogen from the top of the separator is split so that some is purged while the rest is recycled (still at high pressure) and mixed with the newly purchased hydrogen. It was necessary to recycle hydrogen because it is such an expensive input, and used in major excess to simply sending all of it out in the purge to a flare would be very wasteful. In future iterations of the project, the energy created from hydrogen burned off at a flare should be captured and used in the heat exchange network (explained later). The mixed streams, still at high pressure, are then heated to 160oC and fed into the reactor.

===Reaction Phase===

The reaction is to take place in a gas-liquid induction reactor, GLIR for short. The GLIR was chosen because it is best suited for multi-phase gas-liquid reactions. In particular the GLIR has special safety features to ensure worker’s safety under intense operating conditions, such as the high pressure used in our reactor, or when the reactant gas is highly combustible, as hydrogen is in our case. Additionally, GLIR’s are known for their complete utilization of the gas feed and great recovery specs with few losses, which is important for an expensive input feed. In our case, hydrogen can cost upwards of $7/kg and so this is a worthwhile investment. The GLIR will be a sort of fluidized bed reactor holding the catalyst with the liquid feed being pumped through downward as the gas bubbles through the liquid upward while an impeller stirs the mixture to increase contact times. Using a catalyst composed of a combination of Pd/Re/Ag/Na, typical for a hydrogenation process, high conversion of succinic acid and selectivity toward BDO can be achieved. Adding Fe to the catalyst has been shown to further increase conversion of succinic acid and selectivity toward BDO and so that will be done as well. Using a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10% Re catalyst with the balance of the 1.5mm diameter carbon support, we are able to achieve 99.7% conversion of succinic acid with 85.5% selectivity to BDO, 2.04% selectivity to GBL, 9.3% selectivity to THF and the balance to other side products but namely butanol (but also possibly propanol and methane, etc.). The reactor operates isothermally and isobarically at 160oC and 3250 psia. Since the reaction is exothermic a cooling jacket will be placed on the GLIR in order to remove the excess heat generated. The jacket will contain a high heat capacity oil, namely Dowtherm A, that will then be put through a heat exchanger in order to maintain the oil at about 160oC at all times.

===Separation Phase===

The separation of the reactor effluent is the final part of our process. Since the effluent contains so many different components, many different reflux drums (gas-liquid separators) and fractionation columns are necessary. First, the effluent is cooled in a heat exchanger in order to allow for better separation of the hydrogen and liquid products in the reflux drum that follows where the hydrogen is taken out of the effluent mixture and either burned or recycled as described above. Next the remaining products and sent to a let-down valve to depressurize them and then reheated to promote better separation in the distillation column that follows which will separate out the main wastes (THF, water, butanol) from the main products (GBL, BDO). The first waste stream coming off of the top of this column is cooled and then sent to a waste tank as it is highly concentrated with butanol and THF. The other stream is further depressurized and sent to a distillation column to separate a stream highly concentrated in butanol and THF (as above) out, to be put into a waste container, from a stream that is >99% water which will be let out into the Mississippi River. The bottoms stream from the first fractionation column containing the main products is once again depressurized and heated to promote a better separation and then put into a new reflux drum. Here a stream high in water content is separated and recycled from a stream highly concentrated with the desired products. The non-recycled stream is sent to, yet another, distillation column which separates out our major product, 99.7% BDO in the bottoms from the GBL and water. The distillate stream is, once again, heated for better separation and sent to our last distillation column which separates out our other major product, >99% GBL, out of the bottoms from a water waste stream in the distillate which will also be let out into the Mississippi. Further iterations of the project could look at better ways to separate our products (using less columns/drums) or isolating other side-products to be resold (like THF). Additionally, other ways to handle side-product waste should be explored. Please see Appendix 6 for a closer look at our modeled HYSYS simulation.

===Heat Exchange Network (HEN)===

Since there are 9 streams that must be heated or cooled in our plant as well as a stream from the reactor jacket, a heat exchange network is necessary to minimize our total plant utilities in a heat exchange network (HEN). Using pinch point analysis it was determined that the best network contained 12 total heat exchangers with one stream split using a total of 3.87 x 107 kJ/h of hot utility and 3.99 x 106 kJ/h of total cold utility. These were necessary due to the complex nature of optimizing 10 different process streams needing temperature adjustment while avoiding temperature crosses, etc. Most of the streams exchange energy between different process streams while only one uses a cooling water and five use small amounts of high pressure steam, which account for the utilities needed. For more details of the HEN see Appendix 13. Further iterations of the project should consider adding the duties of the four reboilers and four condensers used on our distillation columns to the heat exchange network. As is, the network only considers the heat exchangers needed for process streams in order to minimize total utilities used within the process, however, a significant portion of our utilities is used in our distillation columns and thus future iterations could further reduce this number and make the plant more profitable by incorporating them into the network.

==Process Flow Diagram & Flow Sheets==
Below is listed a complete flow sheet, with data taken from Aspen HYSYS.

Table 1

[[File:Streams.JPG]]

A detailed sizing list of the relevant components is listed below. Of particular interest are the distillation columns, which have heights between 8 and 12 meters. Furthermore, the reactor has a length of 6.2 meters and a diameter of 2.1 meters. A more complete table of sizing and sizing methodologies is listed in the Appendix.

Table 2

[[File:Components.JPG]]

==Economic Analysis==
Table 3

[[File:Econ.JPG]]

Table 3 is a summary of the capital and operating costs required for the production of BDO and GBL. The expenditure on succinic acid clearly stands out; it makes up roughly 80% of the annual operating costs of this plant. The production plant consumes approximately 75.6M kg/yr of succinic acid, and at $1.47/kg, the costs add up quickly. Some other things to note from Table XX; the reactor is the most expensive singular piece of equipment; because it operates at exceedingly high pressure, it has extremely thick walls and is made of a high strength steel alloy. Additionally, the total cost of the heat exchangers is more than $3M; however, the production plant uses twelve heat exchangers, so the average individual cost comes out to a more reasonable $280,000. Lastly, this plant has a high annual utilities cost, mainly because of the 4 distillation columns and the large amount of cooling water necessary to keep the process running at the correct temperature.
Below in Table 4 is a summary of the economic measures of return of this process.

Table 4

[[File:Econ2.JPG]]

As shown clearly in Table 4, this plant has extremely encouraging economic potential, with an average yearly cash flow of $40.8M, a simple payback period of less than 6 months, and a breakeven point of approximately 9 months. These capital projections assume a 2 year construction time, 38% tax rate, 50% capacity in the first year of production, and a 7 year MACRS depreciation method.
Revenue is split into two streams; main product (BDO) and by-product (GBL). The main product revenue is approximately $150M/yr, while the by-product revenue is $40M/yr, despite producing nearly 50 times less GBL than BDO. In future iterations of this design, it may be worthwhile to examine if it is more profitable to convert all of the succinic acid directly to GBL instead of producing the intermediary, BDO.
If the economic returns seem astronomical, it is because they are; no economic investment actually produces these kinds of returns. The extremely favorable prediction could stem from several sources of error; supply and demand, bulk pricing, waste removal, and side reactions. The yearly supply of BDO is approximately 1M metric tons, meaning that this plant would produce 5% of the world’s supply. If the supply of BDO outpaced the demand, the selling price would fall, cutting into main product revenues. Additionally, the estimate of GBL selling price was based off a per kg price; if bulk pricing were used, the selling price of GBL would be between 40-50% lower than the price used. In addition to economic discontinuities, the problem of waste removal was never fully solved. Based on past estimates, waste removal could cost as must as $10M/year, further reducing the profitability of this plant. Lastly, the process of BDO synthesis was simplified for modelling purposes. In actual production, many side reactions would occur; driving down conversion and increasing separation costs.

A sensitivity analysis was performed on all important variables.

[[File:Sensitivity.JPG]]

Figure 1: Sensitivity analysis

Figure 1 shows that the profitability of the plant (based on the 10 year NPV), is most sensitive to the selling price of BDO and GLB, the cost of raw materials, and the construction time. It is least sensitive to changes in the utilities cost and fixed capital costs. It is clear from the figure that this undertaking is profitable in the face of any singular change. However, if several of these variables react unfavorably to the coming economic climate, the plant could potentially make very little money. For example, if the construction time doubles (which happens frequently) and the selling prices of BDO and GBL are driven down by market saturation, the plant could have a 10 year NPV falls to approximately 0.

==Conclusion==
To conclude, this project is highly feasible, and our company stands to make a very high profit from the construction of this plant. Based on a two year construction time, a 38% tax rate, and 50% production over the first year, our simple payback period would be 0.45 years, with yearly revenue of over $190M. We strongly recommend Evanston Chemical to move forward with this facility. However, there are key next steps to be considered. First, a more detailed reaction scheme for the reactor is required. This scheme must be able to handle variable operating pressure and temperature, as well as contain a more detailed and complete incorporation of side reactions. Namely, the reaction of GBL to BDO is a necessary consideration. Moreover, a fully life cycle analysis and environmental health and safety analysis will be required. The removal of waste will also need to be addressed. Additionally, profits may be increased by performing a plant wide optimization project. Also, the assumption of a 5 year catalyst lifetime will need to be addressed in more detail, as the high cost of this component will greatly affect the bottom line. Another factor which may affect the overall profitability is the flocculating prices of rare metals, which make up the catalyst. Also, the market price of these commodity chemicals will almost certainly be affected by a 10% influx of global supply. Finally, while we have planned on also selling GBL, looking into purifying the THF will also be profitable.

==Appendices==
===Appendix 1===
Sizing and construction information.

[[File:Sizing and Construction Info.JPG]]

===Appendix 2===
Equipment Costs

[[File:Equipment Costs.JPG]]

===Appendix 3===
Economic Summary

[[File:Assorted Economic Data.JPG]]

===Appendix 4===
Energy Stream Summary

[[File:Energy Stream Table.JPG]]

===Appendix 5===
HYSYS Simulation

[[File:HYSYS Simulation.JPG]]

===Appendix 6===
Stream Summary Table

[[File:Stream Summary Table.JPG]]

===Appendix 7===
Summary of HYSYS stream compositions.

[[File:Stream Composition Table.JPG]]

===Appendix 8===
Heat exchanger network.

[[File:Heat Exchanger Network.jpg]]

===Appendix 9===
Reaction mechanism summary

[[File:Reaction Mechanism.jpg]]

===Appendix 10===
Process Flow Diagram

[[File: PFDFinal.jpg|1200px]]

==References==
Alibaba.com [Internet]. Hangzhou: Alibaba.com; c1999-2015 [cited 2014 Mar 3].

Bhattacharyya A, Manila MD, inventor; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-butanediol. United States Patent US 7935834 B2. 2011 May 3.

Budge JR, Attig TG, Pedersen SE, inventor; The Standard Oil Co., assignee. United States Patent US 6486367 B1. 2002 Nov 26.

Chung SH, Kim MS, Eom HJ, Lee KY. Hydrogenation of Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts. Proceedings of 2013 AIChE Annual Meeting; 2013 Nov 6; San Francisco, USA.

Deshpandea RM, Buwaa VV, Rodea CV, Chaudharia RV, Millsb PL. Tailoring of activity and selectivity using bimetallic catalyst in hydrogenation of succinic acid. Catal Commun. 2002 July;3(7):269–74.

Ly BK et al. Effect of Addition Mode of Re in Bimetallic Pd-Re/TiO2 Catalysts Upon the Selective Aqueous-Phase Hydrogenation of Succinic Acid to 1,4 Butanediol. Top Catal. 2012 July;55:466-73.

Minh DP, Besson M, Pinel C, Fuertes P, Petitjean C. Aqueous-Phase Hydrogenation of Biomass-Based Succinic Acid to 1,4-Butanediol Over Supported Bimetallic Catalysts. Top Catal. 2010 Sep;53:1270-3.

Newmultifabengineers.com. Hydrogenator, Grease Kettle Manufacturers India–New Multifab Engineers Pvt Ltd–Hydrogenator, Grease Kettle Manufacturers from India [Internet]. Maharashtra: New Multifab Engineers Pvt Ltd.; c2015 [cited 2015 Feb 26]. Available from: http://www.newmultifabengineers.com/hydrogenator/.

Orbichem.com. Chemical Market Insight & Foresight-On A Single Page 1,4-Butanediol [Internet]. Tecnon OrbiChem; c2004-15 [cited 2015 Feb 26]. Available from: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf.

Sigmaaldrich.com [Internet]. St. Louis: Sigma-Aldrich Co. LLC.; c2015 [cited 2014 Mar 3].

Smith R, Varbanov P. What's the price of steam? Chem Eng Prog. 2005 July:29-33.

Wisbiorefine.org. Biobased Products: Succinic Acid [Internet]. Wisconsin Biorefining Development Initiative; c2004-10 [cited 2015 Feb 26]. Available from: http://www.wisbiorefine.org/prod/sacid.pdf.

Design S2

2015-02-28T22:43:17Z

Jian: /* References */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years (Nexant.com). Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products (Orbichem.com). These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes (Ingram and Le, 2013). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation (Burk et al., 2011), but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways (Chung et al., 2013).

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL (Bhattacharyya and Manila, 2011). The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid (Bhattacharyya and Manila, 2011). Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent (Bhattacharyya and Manila, 2011) and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
Bhattacharyya A, Manila MD, inventor; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-butanediol. United States Patent US 7935834 B2. 2011 May 3.

Burk MJ, Stephen J, Dien SJV, Burgard AP, Niu W, inventor; Genomatica Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. United States Patent US8067214 B2. 2011 Nov 29.

Chung SH, Kim MS, Eom HJ, Lee KY. Hydrogenation of Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts. Proceedings of 2013 AIChE Annual Meeting; 2013 Nov 6; San Francisco, USA.

Icis.com. Chemical industry awaits for bio-succinic acid potential [Internet]. Surrey: Reed Business Information Limited; c2015 [cited 2015 Feb 26]. Available from: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/.

Ingram A, Le B. 1,4-butanediol/tetrahydrofuran (BDO/THF) [Internet]. Wheaton: Nexant Inc.; c2011- [updated 2013 Apr; cited 2015 Feb 28]. Available from: http://thinking.nexant.com/sites/default/files/report/field_attachment_abstract/201304/2012_3_abs.pdf.

Nexant.com. Is Bio-Butanediol Here to Stay [Internet]? Wheaton: Nexant Inc.; c2000–15 [cited 2015 Feb 28]. Available from: http://www.nexant.com/about/news/bio-butanediol-here-stay.

Nicnas.gov.au. Butanediol (1,4-butanediol) factsheet [Internet]. Sydney: National Industrial Chemicals Notification and Assessment Scheme [cited 2015 Feb 28]. Available from: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets.

Orbichem.com. Chemical Market Insight & Foresight-On A Single Page 1,4-Butanediol [Internet]. Tecnon OrbiChem; c2004-15 [cited 2015 Feb 26]. Available from: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf.

Design S2

2015-02-28T22:42:51Z

Jian: /* References */

Design S2

2015-02-28T22:40:32Z

Jian: /* Equipment costing */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years (Nexant.com). Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products (Orbichem.com). These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes (Ingram and Le, 2013). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation (Burk et al., 2011), but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways (Chung et al., 2013).

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL (Bhattacharyya and Manila, 2011). The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid (Bhattacharyya and Manila, 2011). Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent (Bhattacharyya and Manila, 2011) and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2015-02-28T22:40:14Z

Jian: /* Reactor */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years (Nexant.com). Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products (Orbichem.com). These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes (Ingram and Le, 2013). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation (Burk et al., 2011), but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways (Chung et al., 2013).

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL (Bhattacharyya and Manila, 2011). The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid (Bhattacharyya and Manila, 2011). Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2015-02-28T22:39:18Z

Jian: /* Process alternatives */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years (Nexant.com). Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products (Orbichem.com). These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes (Ingram and Le, 2013). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation (Burk et al., 2011), but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways (Chung et al., 2013).

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2015-02-28T22:36:49Z

Jian: /* Market analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years (Nexant.com). Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products (Orbichem.com). These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2015-02-28T22:36:22Z

Jian: /* General information */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures (Nicnas.gov.au).

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2015-02-28T22:35:52Z

Jian: /* Introduction */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes (Nexant.com). Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO (Nexant.com). It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid (Icis.com). Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design G1

2015-02-28T22:13:34Z

Jian: /* References */

Team BAT Final Report

Authors: Anne Disabato, Tim Hanrahan, Brian Merkle

Instructors: Fengqi You, David Wegerer, David Chen

Date Presented: March 14, 2014

 


__TOC__

=Executive Summary=
In an effort to build a new bio-product facility for Evanston Chemical, Team BAT is considering producing 99.7% propylene glycol solution. Team BAT designed a small-scale process to use the crude glycerin waste from an up-steam biodiesel facility. It was assumed that capital is available at 12%.

Research on an industrially available propylene glycol manufacturing process, patented by GTC Technology, and a universal process for purifying crude glycerin were used guided the final design (Ding et al., 2013; Xiao et al., 2013). The facility is divided into two sub-processes: pre-treatment of crude glycerin and continuous hydrogenolysis of glycerin to propylene glycol. Microsoft Visio and Aspen HYSYS were used to design the process flow diagram and simulate the production. All other calculations were performed in Microsoft Excel. The plant was designed to operate safely, and have minimal environmental impact.

Team BAT’s plant produces 18.6 tonnes per year of 99.7% propylene glycol. Economic analysis predicts a net present value of - $4.2 million on a twenty-year basis. Based on this analysis, the proposed propylene glycol production facility would be not be economically viable without considerable scale-up and optimization.

=Introduction=
Propylene glycol, C3H8O2, is a non-corrosive, non-toxic, low volatility liquid, used as chemical feedstock for the production of unsaturated polyester resins, and in the food, beverage, cosmetic, and pharmaceutical industry (Propylene-glycol.com). The freezing point of water is lowered when mixed with propylene glycol, and the latter is therefore used as an anti-freeze and de-icing fluid. Propylene glycol also lowers vapor pressure, making it an ideal burst protection fluid in pipes and vessels. As a cleaning product additive, propylene glycol acts as a stabilizer for the dirt-removing ingredients and helps retain their function at low temperatures.

In food and beverage products, propylene glycol is mainly used as a solvent and carrier of flavor and color, or as a thickener, clarifier, and stabilizer in items such as beer, salad dressing, and baking mixtures. It provides lipstick with its consistent texture, preserves the homogenous consistency of body lotions containing both oil and water, and ensures that shampoos foam nicely. In the pharmaceuticals industry, propylene glycol is used to solubilize and provide equal distribution of the active ingredient in the formulation.

The market for propylene glycol is currently dominated by Dow Chemical and BASF, with 1.8 million tonnes produced globally in 2011 (Dow.com, a). Assuming a price of $1.16 per lb, the current market value is $3.97 billion per year (Propylene-glycol.com). Evanston Chemical Technology Division challenged their employees to design a bioproducts facility in Blue Island, IL capable of taking advantage of a small fraction of this market.

The goal of this report is to evaluate Team BAT’s design of a propylene glycol plant, to determine if Evanston Chemical should invest in independent production. The design of our plant was driven by current manufacturing processes found in literature. The design is split into two sections for simplicity: batch purification of crude glycerin and continuous hydrogenolysis of glycerin to propylene glycol. The facility, project economics, and process flow diagram were modeled on Aspen, Aspen Process Economic Analyzer, and Microsoft Visio, respectively.

=Design Basis=
As a part of Evanston Chemicals, Team BAT studied an industrial method of producing propylene glycol through continuous hydrogenolysis as described in the GTC Technology 2013 patent (Ding et al., 2013). Evanston Chemicals corresponding biodiesel facility produces 4,700 lbs / week crude glycerin as a byproduct. With crude glycerin being a commodity in excess, the option of selling crude glycerin will be ignored and the available 4,700 lbs / week will be considered free. Our process was designed to increase biodiesel facility profits by taking advantage of the unwanted crude glycerin byproduct.

Team BAT also considered the Davy Process Technology Limited patent, which uses minimal hydrogen and carried out the reaction in multiple stages (Tuck, 2012). After careful process and market considerations, the GTC process was chosen based on low capital-costs, possible reduced operating costs due to multiple energy integration options, high selectivity in a one-step reaction, and relatively low temperatures.

If the GTC style facility produces the maximum possible 18.6 tonnes per year of propylene glycol, Evanston Chemical will account for less than 0.01% of the market. Team BAT decided not to produce and market additional propylene glycol because it is not the primary objective of the larger biodiesel facility.

=Project Economics=
The total fixed capital cost of the current design is $1.3 MM. The ISBL is $800K, and the OSBL is $300K, with an engineering and contingency cost of $200K. This cost, and all other price data, were adjusted for US Midwest and 2014 dollars. The propylene glycol product revenue is a net of $73K. The cost of raw material is $109K, assuming crude glycerol is free, and the annual cost of hydrogen, 37 wt% HCl and NaOH pellets is $60 K, $1K, and $42K, respectively. Other variable capital costs include $5K in continuous process utilities, $500K in salaries and overhead, and $10K in maintenance. The catalyst costs approximately $1,170 per year, and would need to be changed during the annual scheduled downtime.

Using a 10 year MACRS depreciation method, a tax rate of 28% and capital available at 12%, the project is not economically feasible, with the 10 and 20 year NPV coming in at -$3.2 MM and -$4.2 MM, respectively.

See Appendix I and II for the equipment costs and full economic analysis, respectively. The majority of equipment costing was done on ASPEN Economic Evaluation, with some smaller equipment costs found on Northern Tool & Equipment, Global Industrial, and PKG Equipment (Northerntool.com; Globalindustrial.com; Pkgequipment.com). Utility costs for water and steam were estimated from the City of Chicago website and DailyFinance.com, respectively (Cityofchicago.org; Dailyfinance.com).

=Plant Location=
The propylene glycol plant will be located at 13636 Western Ave, Blue Island, Illinois 60406. The 10,000 square foot site includes: a truck loading dock, potential rail access, and connections to electric, water, and natural gas. The lease cost is $1,400 per month. Due to other operations at the site, including the biodiesel process, only 2,000 square feet will be allocated to the PG process. The effective lease cost will be spatially prorated for the PG process at $280/month.

=Process Overview=
In order to obtain purified glycerin, crude glycerin from the upstream biodiesel is batch purified in a network of vessels. After initial micro-filtration, the glycerin is sent to a vessel that undergoes five stages (A-E) of purification. In Stage A, it is sent to a vacuum evaporation unit, where methanol and water are removed. In Stage B, impurities are converted to more easily separated substances via saponification. After cooling, Stage C consists of acidification to further convert impurities. In stage D, the batch is neutralized. In stage E, the batch undergoes vacuum evaporation for a second time to remove water. Subsequent stages include a settling tank to separate liquid phases and extraction via petroleum ether and denatured ethanol.

In the GTC Technology process, a feed mixture comprising of purified glycerin, hydrogen, and methanol is preheated in a heat exchanger, and fed to a fixed-bed reactor. The reactor effluent is sent to a heat exchanger, where the stream is cooled. It is then separated into a vapor phase stream and a liquid phase stream. The vapor phase stream is released into the atmosphere. The liquid-phase stream is distilled in three distillation columns to obtain purified propylene glycol.

The following sections explain the above process in detail, outlining the results from HYSYS simulations and the rationale for design choices. See Appendix III for Process Flow Diagram of both the batch purification and continuous process.
==Production Schedule==
Calculations assume 8,424 hr/yr operation, implying approximately 351 days of continuous operation, leaving adequate time for maintenance. The primary maintenance consideration remains the catalyst regeneration, which must occur every year. This involves emptying the reactor tubes and refilling with new catalyst. A second maintenance consideration is cleaning the batch equipment. This issue is not pressing as the batch sub process is not run at full capacity. The shutdown, cleanup, and refilling should not require more than a week, ensuring compliance with the production schedule.

==Design Considerations==
===Batch Purification===
The batch purification of crude glycerin is essential in achieving reactor efficiency and final product purity. In order to accomplish this, ethanol must be added to remove salts. Ethanol has an adverse affect on glycerol solubility; salts have lower solubility in an ethanol-glycerol solution than the corresponding sole-glycerol solution. Ethanol allows a significant amount of salt to precipitate out the solution, which can then be removed by microfiltration. The presence of salts can be detrimental to catalyst activity, making this process important in following the production schedule.

====Raw Materials====
The raw materials used in the batch purification process include sodium hydroxide pellets (balance water to make 12.5 M basic solution), 37% hydrochloric acid, water, petroleum ether, and denatured ethanol. The sodium hydroxide pellets and hydrochloric acid are laboratory grade. Petroleum ether and denatured ethanol are completely recycled in the batch process. Due to this as an imperfect assumption, the two solvents will need to be replenished twice per year.

====Modeling and Sizing the Batch Process====
Mass balances on the batch sub process are based a similar analysis by Xiao et al. (2013) published in Industrial & Engineering Chemistry Research. In the paper, the compositions of various samples were analyzed at different stages of the laboratory scale procedure. Those compositions were assumed to be identical our scaled-up batch process, and mass balances were subsequently conducted around each stage. Fatty Acid Methyl Esters (FAME’s) and Glycerides were converted into soap in the saponification stage and Free Fatty Acids (FFA’s) in the acidification stage. The conversion was determined by analyzing the sample compositions before and after the respective stages. The mass and compositions of important streams involved in the batch sub process can be found in Appendix IV.

The amount of sodium hydroxide and hydrochloric acid added in the saponification, acidification, and neutralization stages was calculated from a salt mass balance. The procedures are at pH = 11, pH =1, and pH = 7, respectively. Rather than calculate the amount of acid and base required to reach these conditions, the amount of salt in each sample reported by Xiao et al. was used to back calculate how much acid and base was needed. This methodology makes the mass balance complete and comprehensive, but slightly inaccurate.

The Glycol Package in Aspen HYSYS was used to evaluate various batch process stream densities. Denatured ethanol, along with a mixture of ethanol, methanol, and other additives, were modeled as pure ethanol. Petroleum ether, a solution of hydrocarbons, was modeled as n-decane. FAME’s, FFA’s, and Glycerides were modeled as Methyl Oleate, Oleic Acid, and Triolein, respectively. While these assumptions affect the reported solution density, the results have relatively low dependence on compositional. The batch vessel volumes were found using physical properties from HYSYS and a factor for vapor space of 1.5, or storage capacity of 10 days where applicable, see Appendix V for equipment specification

====Batch Process Assumptions and Limitations====
Along with the assumptions stated in the previous sections, the following simplifications were made in order to model the batch process. First, a dynamic model was not constructed to simulate the saponification and acidification reactions. Instead, we assumed the laboratory procedure conducted by Xiao et al. (2013) could be scaled up. In addition we assumed a 30 minute cool down time because this information was not reported. Liquid pumps were assumed to transfer liquid from tank to tank in 5 minutes. A Gantt chart for the proposed time schedule of the batch sub process can be seen below, see Appendix VI.

Second, complete recovery of glycerol was assumed throughout the process. The amount of glycerol lost to vacuum evaporation can be considered negligible, but losses associated with liquid-liquid extraction and separation can be significant. This assumption will have the effect of overestimating the amount of glycerol purified, although it should have a negligible effect on the compositions stated in Appendix IV. Third, we assumed perfect removal of water, methanol, ethanol, and petroleum ether. Fourth, the first filter was assumed to have no effect on the overall mass balance. The amount of salts removed in the second filter, in actuality, would be the sum of salt and ash removed by Filters 101 and 102.

Both the mass related assumptions and dynamic assumptions listed above are justifiable when the batch process is treated as a single entity, directly scaled up from the laboratory procedure. It is a substantial limitation, however, when attempting to make beneficial changes necessary to optimize the process. One such example is the extreme conditions associated with the saponification and acidification stages. The conditions are not only dangerous, but produce a difficult and potentially expensive material decision regarding vessel V-101. The short solution was to line a stainless steel vessel with an acidic and basic resistant liner that can withstand elevated temperatures. A quote from the manufacturer PKG Equipment Inc. and can be found in Appendix I. Reducing these extreme conditions could be beneficial to the capital cost, operating cost, and safety conditions.

====Batch Optimization====
There exist numerous opportunities for optimization in the batch purification process. Over the course of our design, the batch PFD was optimized as follows: the neutralization stage was temporally moved from post-extraction (via petroleum ether) to directly after acidification. This decision is beneficial because it reduces capital costs and improves the safety conditions of the extremely acidic conditions found in the acidification stage to Vessel V-101.

The current batch PFD suggests nine liquid pumps are needed. In actuality, the number of pumps can be consolidated, as they are never running simultaneously. This will reduce the capital cost. Similar rationale can be used to consolidate the number of condensers and vacuum pumps.

As seen in the current Gantt chart, the batch process takes a substantial amount of time to conduct. The first step in scaling up the batch process would be to conduct laboratory experiments to accurately measure the effects of pH on saponification and acidification. Likewise, experiments would be conducted to analyze the necessary time at each stage of the batch process. Consequently, a dynamic, semi-empirical model could be created to analyze and optimize the process.

Other optimization opportunities include: 1. adapting the batch process to accommodate an upstream, unused glycerol stream, 2. analyzing the trade-off between batch vessels being operated under vacuum and heating them to elevated temperatures and 3. using less expensive, industrial grade reagents.

===Continuous Conversion to Propylene Glycol===
As mentioned in the process overview, the continuous conversion is modeled from the GTC Technology patent. Purified glycerin is heated, sent to a reactor where it is converted to propylene glycol, cooled, and then purified. See Table 1 for a summary of the equipment. In the following sections, the continuous process is explained in detail.

Table 1: Equipment Summary for Continuous Sub-process
[[File:EquipSummary.PNG|center|600px]]

====Raw Materials====
The raw material inputs to the second part of the process, the conversion of purified glycerol to propylene glycol, include purified glycerol and hydrogen gas. The purified glycerol is produced from the batch process described earlier, and is pumped in from a large storage tank. The hydrogen gas, supplied at a pressure of 30 atmospheres, is fed in excess at a rate of 1 kg / hour and is supplied by Praxair at $7 / kg (Dailyfinance.com).

====Reactor====
=====Modeling and Sizing=====
The reactor used to convert glycerol to propylene glycol is modeled from the GTC Technology patent (Ding et al., 2013). The reactor is a fixed-bed reactor packed with catalyst, and operates at 190 °C and 30 atmospheres. The reactor was modeled in HYSYS as a generic conversion reactor using conversion and selectivity data from the article “Kinetics of Hydrogenolysis of Glycerol to Propylene Glycol over Cu-ZnO-Al2O3 Catalysts” by Zhou et al. (2010). The reactor is able to achieve 81.5% conversion of glycerol with selectivity towards propylene glycol of 93%.

Using a LHSV of 4.6 hr-1 and a reactant feed of just under 5 kg / hour, Team BAT determined the size of the reactor to be 0.39 meters in diameter with a tangent length of 1.17 meters, resulting in a total volume of 0.141 cubic meters. The reactor was designed as a stainless steel 304 pressure vessel according to ASME standards, giving a shell thickness of 13 millimeters.

=====Catalyst=====
Team BAT decided to use a Cu-ZnO-Al2O3 catalyst with a Cu: ZnO: Al2O3 molar ratio of 1: 1: 0.5. This catalyst was chosen because of its relatively high conversion of glycerol (81.5%) and extremely high selectivity towards propylene glycol (93%) (Zhou et al., 2010). The catalyst was modeled as a collection of spherical particles, each with a diameter of 0.34 millimeters. Using a void fraction in the reactor of 0.5, the total amount of catalyst needed is 467 kg.

====Design of Heat Transfer Equipment====
There are two main pieces of heat transfer equipment in the continuous part of the process: a heat exchanger to heat the reactor feed to the desired operating conditions as well as a heat exchanger to cool the reactor effluent before the separation equipment.

=====E-201: Heating Reactor Feed=====
The first heat exchanger in the continuous reaction process using superheated steam at 600 psi and 300 °C to heat the mixture of glycerol and hydrogen to the desired reactor operating temperature of 190 °C. The heat exchanger was designed following TEMA recommendations as an AEL-type exchanger with the reactant feed being heated on the tube side by the high-pressure steam on the shell side.

This unit requires a heat transfer area of 0.018 square meters and consists of 157 tubes (stainless steel 304) with a 12 mm inner diameter, 17 mm outer diameter and a length of 0.5 meters. These tubes are arranged in a square pitch resulting in a shell diameter of 0.4 meters. The shell is also constructed from stainless steel 304 and has a wall thickness of 20 mm.

=====E-202: Cooling Reactor Effluent=====
The second heat exchanger in the continuous process uses cooling water at 10 °C to cool the reactor effluent from 222 °C to room temperature. A reduce in temperature increases separation efficiency. This heat exchanger is also an AEL-type exchanger with the cooling water on the tube side and reactor effluent on the shell side.

This unit requires a heat transfer area of 0.043 square meters and consists of 215 stainless steel 304 tubes with an 8 mm inner diameter, 13 mm outer diameter and a length of 1.5 meters. The shell, also constructed from stainless steel 304, has a diameter of 0.31 meters and has a wall thickness of 11 mm.

====Product Purification====
After the glycerol is converted to propylene glycol in the fixed-bed reactor, the desired product must be separated from the other components, including water, unreacted hydrogen and glycerol, as well as unwanted side products, such as methanol, acetol and ethylene glycol. This is achieved using four different pieces of equipment: a liquid-gas separator and three distillation columns in series.

=====Liquid-Gas Separator=====
After the reactor effluent is cooled, it is sent to the first of four separation units. The first unit takes the multiphase stream and separates the vapor components (unreacted hydrogen and other trace components) from the liquid products. The liquid-gas separator was designed as a pressure vessel that can hold 30 minutes worth of product. The unit has a diameter of 1.35 meters and a height of 4.05 meters, giving the vessel a total volume of just over 5.8 cubic meters. The vessel is constructed from stainless steel 304 and has a wall thickness of 4.7 mm. The vapor stream is vented to the atmosphere and the liquid products are sent to a series of three distillation columns.

=====C-201 Distillation Column=====
The first of three distillation columns separates water and alcohols (methanol and acetol) from the unreacted glycerol, ethylene glycol, and the propylene glycol product. The column operates at atmospheric pressure and has 6 sieve trays, with the feed entering on the second tray from the top. The column has a height of 1.8 meters and a diameter of 0.11 meters, and the energy consumed and generated from the reboiler and condenser are 1.63 kW and 1.14 kW respectively.

=====C-202 Distillation Column=====
The second distillation column separates the unreacted glycerol, which can be sent back to the batch process to be purified, from the unreacted ethylene glycol and propylene glycol products, which come off the top of the column and are condensed and pumped to the last column. The column operates at atmospheric pressure and has 10 sieve trays, with the feed entering on the fifth tray from the top. The column has a height of 3 meters and a diameter of 5.6 centimeters, and the energy consumed and generated from the reboiler and condenser are 1.29 kW and 1.25 kW, respectively.

=====C-203 Distillation Column=====
The last distillation column separates the propylene glycol product from the ethylene glycol. The column operates at atmospheric pressure and has 16 sieve trays. The feed to the third column comes from the overhead of the second column, and enters on the sixth tray from the top. The column has a height of 4.8 meters and a diameter of 0.19 meters, and the energy consumed and generated from the reboiler and condenser are each 3.73 kW. The propylene glycol is taken off the top of the tower and has a purity of 99.7 wt%.

====Assumptions and Limitations====
A number of assumptions were made in designing the continuous part of the process. In the reactor, it was assumed that the conversion and selectivity presented by Zhou et al are applicable for the slightly scaled-up process discussed above. It was also assumed that the production of side products other than acetol and ethylene glycol is negligible, though in reality that may not be true. It was also assumed that the design of each piece of equipment is applicable despite the extremely small scale of the proposed process.

==Sensitivity Analysis==
A sensitivity analysis is necessary to analyze the viability of any process. While our process is not economically feasible, a sensitivity analysis was conducted to examine the effects of uncertain parameters. If the sale price of propylene glycol increases by 20%, the change to our NPV is negligible; the process is still unfeasible. Similarly, if the ISBL capital costs or OSBL capital cost are decreased by 20%, the process is still unable to make a profit in the first 20 years. If the main product revenue increases to $900K, the NPV will be positive after 7 years.

==Safety and Environment==
Chemical plant safety is one of the primary requirements in process design at Evanston Chemical. From the delivery of raw materials to final product transport, the employees of Evanston Chemical have the right to a safe workplace. All OSHA standards for exposure, personal protective equipment, and operation control will be strictly followed. Pressures are kept low and should not constitute a major hazard; moreover, vessel wall thickness exceeds ASME BPV code requirements for maximum safety. All process equipment will be fitted with pressure relief valves for safety. The highest temperature is 275 °C, found in the second distillation column bottoms. In the event of a sudden temperature increase, the valves can be shut off.

Neither glycerin nor propylene glycol constitutes a major threat to safety. As additives to consumer products, the chemicals are only slightly dangerous in large quantities (Dow.com, b). Eye contact may result in temporary irritation; corneal injury is unlikely. Prolonged skin contact is unlikely to cause irritation. Inhalation of vapors appears to present no significant hazard in ordinary applications, and this is reflected in the fact that OSHA has not found it necessary to establish a permissible exposure level in the workplace.

The lifecycle of propylene glycol production is relatively environmentally friendly. The fundamental raw material, glycerin, is obtained from a up-stream facility which converts local restaurant vegetable oil into biodiesel. The environmental cost of transportation is minimized.

The product, propylene glycol, is considered to be practically nontoxic to fish on an acute basis (LC50 > 100 mg/L) and practically nontoxic to aquatic invertebrates (Dow.com, b). Additionally, the products of PG degradation are less toxic than the product itself.

=Conclusion=
Team BAT’s proposed plant will produce 18.6 tonnes/yr of 99.7 wt% propylene glycol. Economic analysis of the proposed plant, on a twenty year basis, yields a net present value (NPV) of -$4.2 MM. Hence, the current project is not economically feasible. Please see above Design Consideration sections on optimization for possible ways to improve profitability. While optimization can improve efficiency and reduce costs, scaling-up the process is recommended.

=References=
Cityofchicago.org. Water Sewer Rates [Internet]. Chicago: City of Chicago; c2010-15 [cited 2015 Feb 26]. Available from: http://www.cityofchicago.org/city/en/depts/water/provdrs/cust_serv/svcs/know_my_water_sewerrates.html.

Dailyfinance.com [Internet]. New York: AOL Inc.; c2015 [cited 2015 Feb 26]. Available from: http://www.dailyfinance.com/.

Ding Z, Chiu J, Jin W, inventor; GTC Technology US LLC, assignee. Process for converting glycerin into propylene glycol. US Patent 08394999 B2. 2013 Mar 12.

Dow.com. About propylene glycols [Internet]. Midland: The Dow Chemical Company; c1995-2015a [cited 2015 Feb 26]. Available from: http://www.dow.com/propyleneglycol/about/.

Dow.com. Product Safety Assessment [Internet]. Midland: The Dow Chemical Company; c1995-2015b [cited 2015 Feb 26]. Available from: http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_091a/0901b8038091a41a.pdf?filepath=productsafety/pdfs/noreg/233-00490.pdf&fromPage=GetDoc.

Globalindustrial.com [Internet]. Global Equipment Company Inc.; c2015 [cited 2015 Feb 26]. Available from: http://www.globalindustrial.com/.

Northerntool.com [Internet]. Burnsville: Northern Tool + Equipment [cited 2015 Feb 26]. Available from: http://www.northerntool.com/.

Pkgequipment.com [Internet]. Rochester: PKG Equipment Inc.; c2013 - [cited 2015 Feb 26]. Available from: http://www.pkgequipment.com/index.html.

Praxair.com [Internet]. Danbury: Praxair Technology, Inc.; c2013-15 [cited 2015 Feb 26]. Available from: http://www.praxair.com/.

Propylene-glycol.com [Internet]. Brussels: PO/PG Sector group of Cefic [cited 2015 Feb 26]. Available from: http://www.propylene-glycol.com/.

Sciencelab.com. Material Safety Data Sheet Propylene glycol MSDS [Internet]. Houston: ScienceLab.com, Inc.; c1997-2005 [cited 2015 Feb 26]. Available from: https://www.sciencelab.com/msds.php?msdsId=9927239.

Tuck MWM, inventor; Davy Process Technology Limited, assignee. Process for the hydrogenation of glycerol to propylene glycol. US patent 08227646 B2. 2012 Jul 24.

Xiao Y, Xiao G, Varma A. A universal procedure for crude glycerol purification from different feedstocks in biodiesel production: experimental and simulation study. Ind Eng Chem Res. 2013;52(39):14291-6.

Zhou Z, Li X, Zeng T, Hong W, Cheng Z, Yuan W. Kinetics of hydrogenolysis of glycerol to propylene glycol over Cu-ZnO-Al2O3 catalysts. Chin J Chem Eng. 2010;18(3);384-90.

=Appendix I: Equipment Costs=
[[File:Appendix1.PNG|center|300px]]

=Appendix II: Economic Analysis=
[[File:Appendix2.PNG|center|400px]]

=Appendix III: Process Flow Diagrams=
Batch Sub-process PFD:
[[File:BatchPFD.PNG|center|1000px]]

Continuous Sub-process PFD:
[[File:ContinuousPFD.PNG|center|1000px]]

=Appendix IV: Mass and Energy Balances=
For Mass and Energy Balances for both the batch and continuous sub-processes, please refer to the hard copy of the final report.

=Appendix V: Equipment Specification=
[[File:Appendix5.PNG|center|300px]]

=Appendix VI: Batch Process Gantt Chart=
[[File:Appendix6.PNG|center|1000px]]

=Appendix VII: Design Basis=
[[File:DesignBasis.PNG|center|500px]]

Design S1

2015-02-28T22:13:01Z

Jian: /* References */

Design Report Authors: Michael Gleeson, Thomas Considine, Sean Kelton

Steward: Fengqi You

Date Presented: March 11, 2014

 

==Executive Summary==
The Chemical Intermediary Division ($1) of Evanston Chemical Corporation is interested in evaluating the economic benefit of adding 1,4 Butanediol (BDO) to its already robust offering of chemical intermediaries. It plans on producing 50,000 tonnes of 99.5%wt BDO using a modified Davy Process through a Gas Liquid Induction Reactor (GLIR) with a rare earth metal catalyst. The facility will be located in Lake Providence, LA , due to proximity to raw material productions sites and ease of transportation of the final product.

BDO is produced from Succinic Acid (SUC) by a hydrogenation reaction at very high pressures. This particular process uses a rare earth catalyst to because of the high conversion of SUC and the high selectivity toward BDO. Side products of the reaction include the highly valuable chemicals tetrahydrofuran (THF) and γ-butyrolactone (GBL), as well as water, n-butanol, and various other low value chemicals. The reaction occurs at 165oC and 150 bar, so special attention must be paid to reactor design to account for these extreme conditions.

Aspen HYSYS was used to model this process, and equipment sizes were calculated as specified by Towler. Equipment costs were estimated using Aspen Process Economic Analyzer (formerly known as Icarus). In order to meet the process specifications within the given time-frame, some simplifying assumptions were made that impose limits on the accuracy of the model; specifically, the GLIR was modelled using a conversion reaction. This means that the conversion remained unchanged at unideal operating conditions, which, clearly, is inaccurate. Additionally, only one reaction was modelled; in real world conditions, dozens of reactions would occur within the reactor, which would have a potentially massive effect on the accuracy of this model. Despite these limitations, the possibility of producing BDO for sale in the open market should be investigated because of the extremely encouraging economic potential of this endeavor.

Economic analysis of this process indicates a 10 year NPV of $163M, a 20 year NPV of $258M, and a total capital cost of $17.5M. The variable operational costs are approximately $131M. At a selling point of $3/kg for BDO and $35/kg for GBL, the total revenue will exceed $190M/yr, so it is strongly recommended the ECC pursue this opportunity.

==Introduction==
===Project Justification===
1,4 Butanediol is an important organic chemical used mainly as an intermediate for the production of Tetrahydrofuran (THF), Gamma-Butyrolactone (GBL) and Polybutylene Terephthalate (PBT). In 2011, the global market for BDO reached 1,725.0 kilo tons. Current projections suggest that worldwide BDO consumption will grow to 2550 kilo tons by 2017. The Technology Division of Evanston Chemicals has requested a preliminary design and economic evaluation on the feasibility of producing 1,4 Butanediol from a biomass derived succinic acid.

===Technology Review===
BDO can be produced by hydrogenation of succinic acid in the presence of a catalyst, at high temperatures and pressures (approximately 150-200°C and 20,000 kPa). However, to the best of the authors’ knowledge, there does not exist a means to produce only BDO. Instead, a mixture of THF, GBL, and BDO is produced. The choice of catalyst is the major factor in controlling yields and selectivity of a certain product. Current research suggests that bimetallic catalysts have a stronger activity and lead to higher conversion to BDO. TiO supported 2%Pd/X%Re catalyst and Carbon supported 2%Ru/4%Re catalyst both have been shown to be particularly effective. It is interesting to note that both catalysts contain Re. Research suggests that the synergy between Re and Pd/Ru leads to higher selectivity for BDO. Additionally, the chosen catalyst for this study was a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5 mm carbon support. Taken from an ISP Investments patent from 2011, this catalyst has exceptionally high yields, upwards of 99.7% conversion of succinic acid, as well as high yields of BDO. In total, the percentage conversions of succinic acid to various products are:
BDO: 85.51 wt %
GBL: 2.04 wt %
THF: 9.28 wt %
Butanol: 2.87 wt %
The lifetime of the catalyst is approximately 5 years. Furthermore, multiple reactor types have been discussed in the literature, including CSTRs and PFRs. However, the literature also shows that gas liquid induction reactors are the best for hydrogenation reactions in industry. They are preferred for their safety with respect to explosive gas phase reactants and complete utilization of the gas phase reactant; being especially useful for expensive inputs. These reactors use energy efficient impellers for gas induction and dispersion along with special recovery equipment to prevent waste of the gas phase, thus GLIR was chosen for this study.

===Design Basis===
The plant has been proposed to be built in Lake Providence, Louisiana. This is due primarily to its proximity to suppliers of succinic acid in the south east region, as well as close to distributors by way of the Mississippi River and the Gulf of Mexico. Additionally, the plant has been designed to have a capacity of approximately 50MM kg/yr of BDO production. This will require feeds of compressed hydrogen gas, and an aqueous feed of water and succinic acid, in a 50/50 wt % composition.

==Technical Approach==
The primary tool used to model the plant process was Aspen HYSYS. Because of the non-idealities involved in the NRTL HYSYS fluid package, an additional fluid package was created in Aspen. Additionally, the GLIR reactor chosen was modeled as a conversion reactor. Selectivity and yield of the reactor was modeled based off the specific data from the ISP Investments patent (discussed in Introduction: Technology Review). Although this provided very accurate modeling, the operating pressure and temperature were required to be held constant. This prevented any optimization within the reactor with respect to these operating conditions. The distillation columns were modeled as fractional distillation columns, with bottoms or distillate flow rate, and component recovery as active constraints. Additionally, Aspen Energy Analyzer was used to create the heat exchanger network, which can be seen in the Appendix. The economic analysis was performed in Aspen ICARUS.

[[File:Hysys.JPG]]

Figure 1. Screenshot of Aspen HYSYS process simulation.

As mentioned above, this plant will produce technical grade BDO and GBL, but the THF stream will be treated as waste. Originally, attempts were made to purify the THF stream in order to sell it; this process produces approximately 5M kg/yr, and at a selling point of ~$3.00/kg, this would generate an additional $15M/yr in revenue. However, the stream containing THF also contains water and n-butanol. As shown in Appendix XX, THF and water have a pressure dependent azeotrope; Figures XX1 and XX2 show that the azeotrope can be broken by pressurizing the stream after initial separation and atmospheric pressure. However, the presence of n-butanol makes separation of THF and water impossible; butanol and water have a tight azeotrope that cannot be broken simply by pressurizing the stream. Instead, absorption or ion exchange must be used to purify the stream. After extensive efforts were made to purify the THF, it was decided that the undertaking would not be profitable. In future iterations of this project, redoubled efforts would be made to force separation of THF to generate large revenues.

===Process Description===

There are three main component of our process: pre-treatment, reaction and separation. See Appendix 15 for a detailed PFD of the process to reference.

===Pre-treatment Phase===

In the pretreatment phase of our process we bring all of the components to the correct conditions in order to be fed into the reactor. For example the 50% succinic acid in water feed in pumped to a pressure of 3250 psia and then heated to about 160oC, which are the operating conditions of the gas-liquid induction reactor used in the process. The operating temperature is relatively low in order to promote selectivity toward BDO and prevent other side reactions. At higher temperatures the hydrogenation of succinic acid continues past BDO and creates unwanted products. See Appendix 14 for the full reaction scheme of this process. At this point the feed can be mixed with a recycled steam coming off of our second gas-liquid separator, which is composed of water, BDO and BGL. It was advantageous to combine these two steams entering the reactor because the recycle stream saves excess water that was separated out before the final product and further dilutes the succinic acid concentration, for stabilization purposes, within the feed stream. Furthermore, the excess BDO that is filtered out and would be lost is recycled back into the system to improve the system recovery. Finally the GBL can be further reacted in the presence of hydrogen in order to form BDO, or once again recovered at the end of the process to be purified and sold rather than wasted. Of course the recycled stream must be pressurized and heated to the correct conditions as well, however, we first cool the recycle stream to form a liquid so that it can be pumped to the correct pressure of 3250 psia (rather than compressed as a gas, since compressors are much more expensive) and finally heated back to a temperature of 160oC.
On the other side of the GLIR the hydrogen feed enters the process. Hydrogen purchased at 3000 psia is compressed to 3250 psia and then mixed with recycled hydrogen coming off the top of our first gas-liquid separator. The hydrogen from the top of the separator is split so that some is purged while the rest is recycled (still at high pressure) and mixed with the newly purchased hydrogen. It was necessary to recycle hydrogen because it is such an expensive input, and used in major excess to simply sending all of it out in the purge to a flare would be very wasteful. In future iterations of the project, the energy created from hydrogen burned off at a flare should be captured and used in the heat exchange network (explained later). The mixed streams, still at high pressure, are then heated to 160oC and fed into the reactor.

===Reaction Phase===

The reaction is to take place in a gas-liquid induction reactor, GLIR for short. The GLIR was chosen because it is best suited for multi-phase gas-liquid reactions. In particular the GLIR has special safety features to ensure worker’s safety under intense operating conditions, such as the high pressure used in our reactor, or when the reactant gas is highly combustible, as hydrogen is in our case. Additionally, GLIR’s are known for their complete utilization of the gas feed and great recovery specs with few losses, which is important for an expensive input feed. In our case, hydrogen can cost upwards of $7/kg and so this is a worthwhile investment. The GLIR will be a sort of fluidized bed reactor holding the catalyst with the liquid feed being pumped through downward as the gas bubbles through the liquid upward while an impeller stirs the mixture to increase contact times. Using a catalyst composed of a combination of Pd/Re/Ag/Na, typical for a hydrogenation process, high conversion of succinic acid and selectivity toward BDO can be achieved. Adding Fe to the catalyst has been shown to further increase conversion of succinic acid and selectivity toward BDO and so that will be done as well. Using a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10% Re catalyst with the balance of the 1.5mm diameter carbon support, we are able to achieve 99.7% conversion of succinic acid with 85.5% selectivity to BDO, 2.04% selectivity to GBL, 9.3% selectivity to THF and the balance to other side products but namely butanol (but also possibly propanol and methane, etc.). The reactor operates isothermally and isobarically at 160oC and 3250 psia. Since the reaction is exothermic a cooling jacket will be placed on the GLIR in order to remove the excess heat generated. The jacket will contain a high heat capacity oil, namely Dowtherm A, that will then be put through a heat exchanger in order to maintain the oil at about 160oC at all times.

===Separation Phase===

The separation of the reactor effluent is the final part of our process. Since the effluent contains so many different components, many different reflux drums (gas-liquid separators) and fractionation columns are necessary. First, the effluent is cooled in a heat exchanger in order to allow for better separation of the hydrogen and liquid products in the reflux drum that follows where the hydrogen is taken out of the effluent mixture and either burned or recycled as described above. Next the remaining products and sent to a let-down valve to depressurize them and then reheated to promote better separation in the distillation column that follows which will separate out the main wastes (THF, water, butanol) from the main products (GBL, BDO). The first waste stream coming off of the top of this column is cooled and then sent to a waste tank as it is highly concentrated with butanol and THF. The other stream is further depressurized and sent to a distillation column to separate a stream highly concentrated in butanol and THF (as above) out, to be put into a waste container, from a stream that is >99% water which will be let out into the Mississippi River. The bottoms stream from the first fractionation column containing the main products is once again depressurized and heated to promote a better separation and then put into a new reflux drum. Here a stream high in water content is separated and recycled from a stream highly concentrated with the desired products. The non-recycled stream is sent to, yet another, distillation column which separates out our major product, 99.7% BDO in the bottoms from the GBL and water. The distillate stream is, once again, heated for better separation and sent to our last distillation column which separates out our other major product, >99% GBL, out of the bottoms from a water waste stream in the distillate which will also be let out into the Mississippi. Further iterations of the project could look at better ways to separate our products (using less columns/drums) or isolating other side-products to be resold (like THF). Additionally, other ways to handle side-product waste should be explored. Please see Appendix 6 for a closer look at our modeled HYSYS simulation.

===Heat Exchange Network (HEN)===

Since there are 9 streams that must be heated or cooled in our plant as well as a stream from the reactor jacket, a heat exchange network is necessary to minimize our total plant utilities in a heat exchange network (HEN). Using pinch point analysis it was determined that the best network contained 12 total heat exchangers with one stream split using a total of 3.87 x 107 kJ/h of hot utility and 3.99 x 106 kJ/h of total cold utility. These were necessary due to the complex nature of optimizing 10 different process streams needing temperature adjustment while avoiding temperature crosses, etc. Most of the streams exchange energy between different process streams while only one uses a cooling water and five use small amounts of high pressure steam, which account for the utilities needed. For more details of the HEN see Appendix 13. Further iterations of the project should consider adding the duties of the four reboilers and four condensers used on our distillation columns to the heat exchange network. As is, the network only considers the heat exchangers needed for process streams in order to minimize total utilities used within the process, however, a significant portion of our utilities is used in our distillation columns and thus future iterations could further reduce this number and make the plant more profitable by incorporating them into the network.

==Process Flow Diagram & Flow Sheets==
Below is listed a complete flow sheet, with data taken from Aspen HYSYS.

Table 1

[[File:Streams.JPG]]

A detailed sizing list of the relevant components is listed below. Of particular interest are the distillation columns, which have heights between 8 and 12 meters. Furthermore, the reactor has a length of 6.2 meters and a diameter of 2.1 meters. A more complete table of sizing and sizing methodologies is listed in the Appendix.

Table 2

[[File:Components.JPG]]

==Economic Analysis==
Table 3

[[File:Econ.JPG]]

Table 3 is a summary of the capital and operating costs required for the production of BDO and GBL. The expenditure on succinic acid clearly stands out; it makes up roughly 80% of the annual operating costs of this plant. The production plant consumes approximately 75.6M kg/yr of succinic acid, and at $1.47/kg, the costs add up quickly. Some other things to note from Table XX; the reactor is the most expensive singular piece of equipment; because it operates at exceedingly high pressure, it has extremely thick walls and is made of a high strength steel alloy. Additionally, the total cost of the heat exchangers is more than $3M; however, the production plant uses twelve heat exchangers, so the average individual cost comes out to a more reasonable $280,000. Lastly, this plant has a high annual utilities cost, mainly because of the 4 distillation columns and the large amount of cooling water necessary to keep the process running at the correct temperature.
Below in Table 4 is a summary of the economic measures of return of this process.

Table 4

[[File:Econ2.JPG]]

As shown clearly in Table 4, this plant has extremely encouraging economic potential, with an average yearly cash flow of $40.8M, a simple payback period of less than 6 months, and a breakeven point of approximately 9 months. These capital projections assume a 2 year construction time, 38% tax rate, 50% capacity in the first year of production, and a 7 year MACRS depreciation method.
Revenue is split into two streams; main product (BDO) and by-product (GBL). The main product revenue is approximately $150M/yr, while the by-product revenue is $40M/yr, despite producing nearly 50 times less GBL than BDO. In future iterations of this design, it may be worthwhile to examine if it is more profitable to convert all of the succinic acid directly to GBL instead of producing the intermediary, BDO.
If the economic returns seem astronomical, it is because they are; no economic investment actually produces these kinds of returns. The extremely favorable prediction could stem from several sources of error; supply and demand, bulk pricing, waste removal, and side reactions. The yearly supply of BDO is approximately 1M metric tons, meaning that this plant would produce 5% of the world’s supply. If the supply of BDO outpaced the demand, the selling price would fall, cutting into main product revenues. Additionally, the estimate of GBL selling price was based off a per kg price; if bulk pricing were used, the selling price of GBL would be between 40-50% lower than the price used. In addition to economic discontinuities, the problem of waste removal was never fully solved. Based on past estimates, waste removal could cost as must as $10M/year, further reducing the profitability of this plant. Lastly, the process of BDO synthesis was simplified for modelling purposes. In actual production, many side reactions would occur; driving down conversion and increasing separation costs.

A sensitivity analysis was performed on all important variables.

[[File:Sensitivity.JPG]]

Figure 1: Sensitivity analysis

Figure 1 shows that the profitability of the plant (based on the 10 year NPV), is most sensitive to the selling price of BDO and GLB, the cost of raw materials, and the construction time. It is least sensitive to changes in the utilities cost and fixed capital costs. It is clear from the figure that this undertaking is profitable in the face of any singular change. However, if several of these variables react unfavorably to the coming economic climate, the plant could potentially make very little money. For example, if the construction time doubles (which happens frequently) and the selling prices of BDO and GBL are driven down by market saturation, the plant could have a 10 year NPV falls to approximately 0.

==Conclusion==
To conclude, this project is highly feasible, and our company stands to make a very high profit from the construction of this plant. Based on a two year construction time, a 38% tax rate, and 50% production over the first year, our simple payback period would be 0.45 years, with yearly revenue of over $190M. We strongly recommend Evanston Chemical to move forward with this facility. However, there are key next steps to be considered. First, a more detailed reaction scheme for the reactor is required. This scheme must be able to handle variable operating pressure and temperature, as well as contain a more detailed and complete incorporation of side reactions. Namely, the reaction of GBL to BDO is a necessary consideration. Moreover, a fully life cycle analysis and environmental health and safety analysis will be required. The removal of waste will also need to be addressed. Additionally, profits may be increased by performing a plant wide optimization project. Also, the assumption of a 5 year catalyst lifetime will need to be addressed in more detail, as the high cost of this component will greatly affect the bottom line. Another factor which may affect the overall profitability is the flocculating prices of rare metals, which make up the catalyst. Also, the market price of these commodity chemicals will almost certainly be affected by a 10% influx of global supply. Finally, while we have planned on also selling GBL, looking into purifying the THF will also be profitable.

==Appendices==
===Appendix 1===
Sizing and construction information.

[[File:Sizing and Construction Info.JPG]]

===Appendix 2===
Equipment Costs

[[File:Equipment Costs.JPG]]

===Appendix 3===
Economic Summary

[[File:Assorted Economic Data.JPG]]

===Appendix 4===
Energy Stream Summary

[[File:Energy Stream Table.JPG]]

===Appendix 5===
HYSYS Simulation

[[File:HYSYS Simulation.JPG]]

===Appendix 6===
Stream Summary Table

[[File:Stream Summary Table.JPG]]

===Appendix 7===
Summary of HYSYS stream compositions.

[[File:Stream Composition Table.JPG]]

===Appendix 8===
Heat exchanger network.

[[File:Heat Exchanger Network.jpg]]

===Appendix 9===
Reaction mechanism summary

[[File:Reaction Mechanism.jpg]]

===Appendix 10===
Process Flow Diagram

[[File: PFDFinal.jpg]]

==References==
Alibaba.com [Internet]. Hangzhou: Alibaba.com; c1999-2015 [cited 2014 Mar 3].

Bhattacharyya A, Manila MD, inventor; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-butanediol. United States Patent US 7935834 B2. 2011 May 3.

Budge JR, Attig TG, Pedersen SE, inventor; The Standard Oil Co., assignee. United States Patent US 6486367 B1. 2002 Nov 26.

Chung SH, Kim MS, Eom HJ, Lee KY. Hydrogenation of Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts. Proceedings of 2013 AIChE Annual Meeting; 2013 Nov 6; San Francisco, USA.

Deshpandea RM, Buwaa VV, Rodea CV, Chaudharia RV, Millsb PL. Tailoring of activity and selectivity using bimetallic catalyst in hydrogenation of succinic acid. Catal Commun. 2002 July;3(7):269–74.

Ly BK et al. Effect of Addition Mode of Re in Bimetallic Pd-Re/TiO2 Catalysts Upon the Selective Aqueous-Phase Hydrogenation of Succinic Acid to 1,4 Butanediol. Top Catal. 2012 July;55:466-73.

Minh DP, Besson M, Pinel C, Fuertes P, Petitjean C. Aqueous-Phase Hydrogenation of Biomass-Based Succinic Acid to 1,4-Butanediol Over Supported Bimetallic Catalysts. Top Catal. 2010 Sep;53:1270-3.

Newmultifabengineers.com. Hydrogenator, Grease Kettle Manufacturers India–New Multifab Engineers Pvt Ltd–Hydrogenator, Grease Kettle Manufacturers from India [Internet]. Maharashtra: New Multifab Engineers Pvt Ltd.; c2015 [cited 2015 Feb 26]. Available from: http://www.newmultifabengineers.com/hydrogenator/.

Orbichem.com. Chemical Market Insight & Foresight-On A Single Page 1,4-Butanediol [Internet]. Tecnon OrbiChem; c2004-15 [cited 2015 Feb 26]. Available from: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf.

Sigmaaldrich.com [Internet]. St. Louis: Sigma-Aldrich Co. LLC.; c2015 [cited 2014 Mar 3].

Smith R, Varbanov P. What's the price of steam? Chem Eng Prog. 2005 July:29-33.

Wisbiorefine.org. Biobased Products: Succinic Acid [Internet]. Wisconsin Biorefining Development Initiative; c2004-10 [cited 2015 Feb 26]. Available from: http://www.wisbiorefine.org/prod/sacid.pdf.

Design G2

2015-02-28T22:11:44Z

Jian: /* References */

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

=Executive Summary=
Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol. This reaction alone accounted for approximately 65% of total glycerol production in 2011. The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol. After conducting a thorough review of the literature, a process was developed based on existing UOP patented technology. This process produces propylene glycol via hydrogenolysis of glycerol. The reaction is carried out at 370 °F and 800 psi, which results in 85% conversion of glycerol with a 91% selectivity to propylene glycol, balance ethylene glycol. The main product is purified to 99.8 wt% to meet USP/EP grade. The main byproduct, ethylene glycol, is sold at 99.9 wt%. The process was simulated in Aspen HYSYS V7.3 to determine material balances and overall energy requirements. The process uses 16,919 tons of crude glycerol a year to produce 9,601 tons of propylene glycol and 759 tons of ethylene glycol year. This requires 823,680 tons of water, 609,840 tons of steam and 229,680 kWh a year. The sizing and cost analysis for each of the individual machines and utilities as well as the overall economic analysis have also been examined. The project is estimated to cost 7.63 $MM in capital and 12.3 $MM annual cost of production. The total project revenue comes out to 25.9 $MM each year. After an economic analysis the process was determined to have a 10 year NPV of 4.11 $MM and 20 year NPV of 7.9 $MM with respective IRR of 30% and 34%. These numbers were calculated using 20% cost of capital, a 34% tax rate and a 10 year MACRS depreciation. The project was deemed to be highly profitable and is recommended to move forward when possible.

=Introduction=
Various political, economic, and environmental concerns over the past decades have led to a desire to decrease dependence on fossil fuels for energy. One alternative is biofuel, or fuel derived from living organisms. Several countries and organizations have worked to promote the use of biofuels. In the United States, the Energy Independence and Security Act (EISA) of 2007 mandated that the volume of renewable fuels blended into transportation fuels be 36 billion gallons by 2022 (The Energy Independence and Security Act of 2007, 2007). Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol (Davyprotech.com). This reaction alone accounted for approximately 65% of total glycerol production in 2011 (Transparencymarketresearch.com). The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol.

=Design Basis=

==Market Analysis==

The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $200/ton (Alibaba.com; Bozell and Petersen, 2010). As shown in Figure 1, the supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum (Oleoline.com).

[[File:Glycerol.png]]

''Figure 1. Global glycerine production in various industrial sectors.''

The production grades of glycerol are crude, technical grade, and USP (United States Pharmaceutical) grade. Crude glycerol comes from production of biodiesel and contains 40-88% glycerol with significant amounts of salt, water, soaps, and methanol. Technical grade glycerol is a refined product with a minimum 98% glycerol content and no salt, soaps, methanol, or other contaminants. USP grade glycerol is a pharmaceutical grade for use in the food, pharmaceutical, and cosmetics industries (Srsbiodiesel.com).

Commercial sources of glycerol other than biodiesel production include fatty acids, fatty alcohols and from the soap industry via the saponification process (Bozell and Petersen, 2010). Glycerol is recognized as safe for animals and humans and environmentally benign, with no significant environmental regulations.

Propylene glycol is conventionally produced using propylene oxide. It is, therefore, sensitive to the price and availability of petroleum and associated products (Davyprotech.com). For this reason, propylene glycol is relatively expensive at around $2500/ton (Interview with Dow Chemical). Supply of propylene glycol struggles to keep up with an increasing annual global demand currently at 1.8m tons (Prweb.com). The ability to isolate propylene glycol production from petroleum by using inexpensive glycerol as a feedstock would be hugely advantageous.

Propylene glycol is used in several applications, including the food, pharmaceutical, and cosmetics industries, as well as in liquid detergents, functional fluids, and unsaturated polyesters (Nizamoff). The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity) (Oleoline.com). Like glycerol, propylene glycol is recognized as safe for animals and humans. Because propylene glycol is biodegradable, it is not considered harmful to the environment and, thus, there are no significant environmental regulations.

==Process Technology==
Several different processes have been proposed for the conversion of glycerol to propylene glycol. These include UOP (Bricker and Leonard, 2012), Davy Process Technology (Tuck, 2012), GTC Technology (Ding et al., 2013), the Lanzhou Institute process (Cui et al., 2009), the Petroleo Brasileiro (Rabello et al., 2011) process, and ADM (Bloom, 2011). These methods all employ catalytic hydrogenolysis and proceed using the same general pathway, show in Figure 2.

[[File:BFD.PNG]]

''Figure 2.'' Block Flow Diagram of process alternatives

====Pre-Treatment====

: The production of propylene glycol from glycerol requires technical grade glycerol, which means a crude glycerol feed must undergo pre-treatment before entering the reactor. For different grades of glycerol the specific process will change, but it will generally be necessary for feeds to be purified, mixed, and heated before high purity glycerol is sent to the synthesis stage. In the GTC process, glycerol, hydrogen and methanol are mixed and heated to anywhere from 150 °C to 240 °C, at pressures between 20 and 80 atm. The preferred composition of the mixture assumes an already pure glycerol feed to be mixed, so any glycerol purchased at lower purities must be distilled to purity before entering the mixer and heater. The Lanzhou and Petroleo Brasileiro processes describe vacuum filtration and distillation of crude glycerol to remove impurities such as sodium, chloride, sulfur and phosphorous salts, fatty acids, phospholipids, glycerides, soaps and biodiesel residues. Any of these impurities can kill the catalyst used downstream. The treated glycerol purity is between 90 – 100%.

====Synthesis====

:In all process technologies considered, the basis of the synthesis is hydrogenolysis of glycerol via packed bed reactors with some form of a catalyst, usually copper based. This reaction is shown in Figure 3. In some cases, the process allows for more reactors to be used in series to achieve a higher conversion. Much of the variation in the processes being examined is based on different operating conditions and the desired purity of the product, propylene glycol.

:[[File:Reaction.PNG]]
:''Figure 3.'' Catalytic hydrogenolysis of glycerol to propylene glycol

====Separation====

:A series of separations is used to separate by-products from propylene glycol. Three step distillations are common; some procedures allow for additional steps, which can change the purity of the product. Common byproducts that need to be separated are methanol, acetol, water, and various other minor alcohol solutions.

==Site Conditions and Capacity==

In the United States, the EPA biofuel mandate for 2014 will be reduced from 18.15 billion gallons to 15-15.52 billion gallons (United States Environmental Protection Agency), so the production of biodiesel will decrease, decreasing the supply of crude glycerol in the United States. In South America, Argentina and Brazil are the largest producers of biodiesel, with production in Brazil growing at the fastest rate. It is estimated that 25-30% of Brazilian glycerol production went to drain in 2010 and 2011, indicating a large supply of inexpensive feedstock (Oleoline.com). Building a facility in Salvador da Bahia, Brazil not only enables access to this supply of inexpensive glycerol, but also provides access to a port city and thus allows export of propylene glycol to high demand markets such as China and the U.S. Additional benefits of building in Brazil include the lower corporate tax rate at 34% compared to 40% in the United States (Kpmg.com) and the temperate climate with an almost constant average temperature of 80 °F (Wmo.int). Dow Chemical currently operates a conventional propylene glycol facility near Salvador, indicating a potentially strong market in the area (Dow.com). The capacity selected for this project is 10,000 ton/year. Current plants using comparable technology, such as ADM and Oleon operate at 100,000- and 200,000-tons, respectively (Icis.com, a). The plant capacity is therefore relatively small, which leaves room for increased production.

==Process Model Basis and Assumptions==

===Reactor===

The process is based on the design outlined by UOP (Bricker and Leonard, 2012). The reaction is catalytic hydrogenolysis of glycerol to propylene glycol over a Co/Pd/Re catalyst consisting of 2.5 wt% Co, 0.4 wt% Pd, and 2.4 wt% Re on NORIT ROX 0.8. The catalyst was reduced at 320 °C in the presence of only H2 prior to use in the reactor. The reaction is carried out at 225.6 °C and 5516 kPa with a 1.17 LHSV. The feed enters the reactor at a Hydrogen to glycerol feed ratio of 2.5:1 and at a pH of 12. At these reactor conditions glycerol conversion and selectivities toward propylene glycol and ethylene glycol are 85%, 91%, and 9%, respectively. The upper bound for reactor methanol concentration was set at 7 wt% to maintain catalyst performance according to specifications outlined by UOP (Bricker and Leonard, 2012).

===Feedstocks and Products===

The reactor feed glycerol (including pre-treated and recycled glycerol) is at 23.16 °C and 5516 kPa and has a composition of 37.77 wt% glycerol, 54.42 wt% water, .77 wt% NaOH, 3.36 wt% sodium sulfate, 3.63 wt% methanol, and .04 wt% acetic acid (Bricker and Leonard, 2012). Hydrogen gas is purchased at 187.8 °C and 5516 kPa. Our main product, propylene glycol, can be sold at industrial grade purity of 99.5 wt% or USP grade purity of 99.8 wt% (Dow.com). One of our byproducts, ethylene glycol, can be sold at a variety of grades, including Polyester grade (99.9 wt%) and Industrial grade (99.1 wt%) (Meglobal.biz).

=Process Overview=

The process flow diagram (PFD) can be found in Figure 4. Incoming glycerol is a byproduct of biodiesel production, usually 40 to 85% glycerol, so it contains fatty acids that must be removed before contacting the fixed-bed reactor catalyst. M-101 mixes the incoming feed with sulfuric acid to remove the fatty acids and produce acidulated glycerol. Acidulated glycerol can contain some amount of methanol, sodium, potassium, sulfur, iron, nickel, chloride or trace impurities. The presence of such impurities in small enough amounts will not negatively affect the production of propylene glycol. The best way to ensure the glycerol mixture will be usable is to ensure that methanol content is <1.5% by weight. The acidulated glycerol is then moved to mixer M-102, where it is contacted with 1.77 wt% aqueous sodium hydroxide. This mixer will increase pH to ~12; a basic glycerol solution will have a much higher selectivity towards propylene. The pH corrected glycerol stream is then heated to 148.9 °C and mixed with water and glycerol recycle streams in M-103. The outgoing glycerol mixture is then mixed with compressed hydrogen gas in a 2.5:1 hydrogen to glycerol mole ratio. The hydrogen comes from an external gas feed. The resulting liquid/gas mixture is sent to the fixed-bed reactor R-101.

[[File:PFD_final.png|1100px]]

''Figure 4. Process Flow Diagram for the production of propylene glycol.''

Hydrogenolysis of glycerol to propylene glycol is carried out in R-101 at 187.8 °C and 5516 kPa. Due to the exothermic nature of the reaction, it is necessary to provide a quench gas stream. In this case, the recycled hydrogen comes in at 72.8 °C, which maintains the reactor temperature at 187.8 °C. The catalyst utilized is a Pd/Co/Re on NORIT ROX 0.8, which provides an 85% conversion of glycerol, with a 91% selectivity to propylene glycol at the given operating conditions. The reactor effluent contains propylene glycol, unreacted glycerol and other byproducts and hydrogen gas. The effluent is sent to V-101, a flash evaporator, where the hydrogen gas is removed from the stream and split into two directions: to be sent off as waste and to be recycled. The waste stream is useful to remove any unwanted gasses that may accumulate over repeated reaction cycles. The resulting propylene glycol mixture is then sent to V-102 for separation and purification.

V-102, a fractionation tower, removes water and C2 alcohols from the propylene glycol reactor effluent. The overhead stream, containing 96 wt% water and balance C2 alcohols, is recycled. The bottoms of V-102 contain water-free propylene glycol, which is then sent to V-103, another fractionation tower which will separate the desired product from the unreacted glycerol and other byproducts. The overhead stream contains 92.6 wt% propylene glycol. The bottoms stream contains unreacted glycerol, ethylene glycol, sodium salts and other impurities. This is sent to F-101, a solid/liquid filter that will remove the solid salt impurities for disposal. The resulting purified liquid stream can be recycled to the beginning of the process and mixed with incoming feed in M-103.

The overheads of V-103 are sent to V-104, which will separate propylene glycol from ethylene glycol. The resultant overheads are 99.8 wt% propylene glycol, which is sent to a storage tank. Additionally, the bottoms are 99.9 wt% ethylene glycol, which is also stored in a tank.

=Process Simulation=

The process is modeled in Aspen HYSYS V7.3 using the non-random two-liquid (NRTL) model as the fluid package, the results of which are shown in Figure 5.

[[File:hysys.png|1100px]]

''Figure 5. HYSYS simulation for the production of propylene glycol.''

=Optimization=

Simple distillation columns in HYSYS were used to find initial estimates for tray numbers, reflux ratios, and optimal feed stage location. Once complex columns were simulated, these specifications were further optimized. Liquid returned to columns via reflux is cooler than up-flowing vapors. Heat transfer between the two components improves the efficacy of the distillation tower, reducing the number of trays needed. However, if a column is operated in total reflux, no product will ever be collected. The price of each column, utilities costs, product yields were optimized by testing several combinations of reflux ratios and tray numbers. The temperature of the inlet stream and component fractions should be similar to the tray the feed enters on. This knowledge was used to optimize the feed tray numbers for each distillation column, decreasing the number of trays needed, the cost of utilities, and increasing the product purity.

Reactor Cost was optimized using Solver in Microsoft Excel 2010. The cost accounted for the pressure drop across the reactor (Ergun equation), minimum volume necessary to meet target LHSV, and design specifications for pressure vessels including wall thickness and diameter, and minimum heat transfer specifications such as area, jacket spacing, jacket type, and heat transfer fluid type. Also, several materials were evaluated, including SS304 and SS407, to find the lowest overall cost.

=Waste Streams=

The water purge is a dilute aqueous waste stream and will be treated in a wastewater facility at a cost of $1.5/t. The hydrogen and glycerol purge can be used as heating fuels due to their high heating values. This will offset waste treatment costs as well as fuel costs. If the price of heating fuel is taken to be $4.50/GJ (Interview with Dave Wegerer), this results in savings of $638.10/t H2 and $68/t Glycerol purge. The solid waste, Na2SO4, can be sold at around $100/t (Kostick).

=Equipment Costs=
Figure 6 below shows the approximated costs of each of the pieces of equipment calculated using Aspen Economic Evaluator v7.3.1. The major components running through the equipment are not corrosive, except basic water. In addition most of the vessels are under fairly standard temperatures and pressures. The key exception is the jacketed reactor, which is subject to extreme conditions. The selection of SS407 allowed for a cheaper reactor as compared to SS304 due to the higher tensile strength. The total ISBL equipment cost is 4.8 $MM in 2010 Gulf Coast USD. The NF cost index is 2250 in 2010 and will conservatively be 2050 in 2014 (Towler and Sinnott, 2013), which adjusts project cost to 5.33 $MM in 2014 Gulf Coast USD. The 2003 location factor for Brazil is 1.14 (Towler and Sinnott, 2013), and the exchange rate in 2003 was 1 Real = $.3402 (Oanda.com). The average rate for the past 3 months has been 1 Real = $.427 (Bloomberg.com, a). The adjusted capital cost for Brazil in 2014 is therefore 7.63 $MM. Since the project is large-volume chemical on a new site, OSBL is taken as 40% of ISBL, or 3.05 $MM. Engineering and contingency costs are taken as 10 and 15%, respectively, of combined ISBL and OSBL costs.

[[File:EquipCosts.PNG]]

''Figure 6.'' Equipment Cost Breakdown

=Prices=

The price of feedstocks crude glycerol and hydrogen are $200/t (Alibaba.com; Bozell and Petersen, 2010) and $1100/t (Icis.com, b). The price of products propylene glycol and ethylene glycol are $2557/t (Interview with Dow Chemical) and $1400/t (Meglobal.biz). The price of consumables NaOH and H2SO4 are $635/t (Icis.com, c) and $80/t (Icis.com, d). The catalyst must be replaced every 2 years, at a cost of 5.13 $MM (Basf.com; Lme.com; Sigmaaldrich.com). The price of electricity has been fluctuating recently due to lack of rainfall, and is taken as 0.202 $/kWh (Bloomberg.com, b). Utilities prices for high pressure steam, medium pressure steam, and cooling water are $14.3/t, $12/t, and $.024/t, respectively (Towler and Sinnott, 2013).

=Fixed Operating Costs=

Based on the plant size, three shift positions with 4.8 operators per shift will comprise the operating labor. A salary of $35,000 is a reasonable estimate of operator wages in Brazil. Supervision is taken as 25% of operating labor, and direct overhead is 45% of labor and supervision. Maintenance is taken as 3% of ISBL Cost, and plant overhead is 65% of labor and maintenance costs. Property and local tax and insurance are both typically 1% of ISBL plus OSBL Cost. Repayment of debt associated with fixed investment is accounted for in the weighted average cost of capital so 0% is taken as fixed cost of production. However, working capital will be funded entirely by debt, so 5% interest of working capital is taken as interest on debt financing.

The plant is scheduled to be constructed over two years, with 40% of capital expenditure being accounted for in year 1. The plan will operate at 70% capacity in year 3 and 100% in the subsequent years. Cost of equity is taken to be 30% based on chemical industry companies (Towler and Sinnott, 2013), adjusting for increased risk in South American ventures. The debt ratio is taken to be 0.4 which allows this project to be financed by corporate bonds that are rated A and above, with a debt cost of capital of 5%. The resulting weighted average cost of capital is therefore 20%. The project will be depreciated using MACRS 10 year depreciation (Icis.com, e) which allows larger tax savings in the near-term, resulting in higher project NPV. The corporate tax rate in Brazil is 34% (Kpmg.com). Working capital is calculated as seven weeks Cash Cost of Production (CCOP) minus two weeks feed plus 1% of Fixed Capital Cost (Towler and Sinnott, 2013).

=Utilities and Pinch Analysis=

The total cost of utilities was found using the energy outputs from HYSYS and known costs of natural gas, water, and electricity in Brazil from commodity indices and surveys from the Brazilian government. The results are presented visually in Figure 7 below. The total utility bill comes to $2,424,000 per year. $1,110,000 from heating gas required to create steam for heating in the process, $1,304,000 in water for both steam generation and cooling water, and approximately $10,000 for electricity to power the pumps and any local offices or break rooms. One important note to consider is that the price of gas in Brazil has risen 40% in the past three months. Continuing fluctuations in energy prices could greatly affect these estimates from year to year.

In order to determine the annual cost of utilities, it was necessary to carry out some heat exchanger design calculations and estimations. After surveying the energy requirement of each exchanger, it was determined that cooling water and steam will be the simplest heat transfer fluids to use, due to the relatively small heat requirements and change in temperature of each process stream. In the case of the three reboilers and three condensers, which are designed with the distillation columns, it was only necessary to find a mass flow rate of steam and water respectively. For the cooling water, once the mass flow rate was calculated, this was sufficient to price. For steam, in addition to purchasing the required mass of water, it was necessary to determine the heat required to raise the steam to the required temperatures. For the one cooler and one heater, we also utilized water and steam, and more thorough design was developed in order to accurately price the two exchangers and to help make a pinch analysis viable.

[[File:Fig4.PNG]]

''Figure 7.'' Utilities Breakdown

=Economic Analysis=

Gross profits are 8.1 $MM from year 4 onward and the project has a simple payback period of 2.6 years. The project Net Present Value (NPV) for 10 and 15 years is 4.1 $MM and 6.8 $MM. The expected return on this project (10 year IRR) is 30.3%, indicating this project is highly profitable and can be scaled up for higher NPV. Accelerating the project schedule to complete the plant in less than 2 years will also greatly increase the NPV.

=Sensitivity Analysis=

A sensitivity analaysis was carried out for a variety of process parameters. For catalyst, PG, HP and MP Steam prices, best- and worst-case were taken as +/- 10% of the base price. The project NPV is most sensitive to the price of Propylene Glycol and Glycerol, which is expected as these are the main product and feedstock. The NPV is also highly sensitive to the cost of capital. The results are presented below, in Figure 8.

[[File:Fig5.PNG]]

''Figure 8.'' Sensitivity Analysis

=Conclusion=

Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years, although there are some existing environmental and safety concerns. Our current plans involve burning an effluent stream in which the key components are hydrogen, ethylene glycol and some fatty acids. In this case an analysis will need to be done in order to determine the extent of the damage to the local air and if a purification step is necessary. The main safety concerns involve the acid streams and the reactor itself. Operators will needs to be thoroughly educated on acid burn precaution and treatment procedures due to the acidic requirements of the streams. The reactor runs at very high pressures and given the exothermic nature of the reaction appropriate steps will need to be taken in order to ensure that runaway reactions can be safely dealt with and pressure relief systems will be put in place. Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years. However, there is definite room for expansion in the design; our low NPV values and high IRR values indicate the ability to leverage economies of scale and dramatically expand our profit margins. As it stands, we recommend maximizing the NPV of the project with full scale optimization. This entails the addition of parallel reaction trains and the inclusion of a heat exchange network to fully maximize our profit margins. A plant layout should be developed along with the inclusion of automated control schemes to better optimize the process operation. The project currently holds great economic potential and with some more detailed engineering, could provide a very high return for our shareholders.

=References=

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Bloomberg.com. BRAZIL REAL-US DOLLAR Exchange Rate [Internet]. New York: Bloomberg L.P.; c2015a [cited 2015 Feb 26]. Available from: http://www.bloomberg.com/quote/BRLUSD:CUR.

Bloomberg.com. Brazilian Power Price Surges to Record Amid Dry Spell [Internet]. New York: Bloomberg L.P.; c2015b [cited 2015 Feb 26]. Available from: http://www.bloomberg.com/news/2014-01-31/brazilian-power-price-surges-to-record-amid-dry-spell.html.

Bozell JJ, Petersen GR. Technology development for the production of biobased products from biorefinery carbohydrates—the US Department of Energy’s “Top 10” revisited. Green Chem. 2010 Apr;12:539-54.

Bricker ML, Leonard LE, inventors; UOP LLC, assignee. Methods for Converting Glycerol to Propanol. United States patent 08101807 B2. 2012 Jul 24.

Cui F, Chen J, Xia C, Kang H, inventors; Lanzhou Institute of Chemical Physics, Chinese Academy of Science, assignee. Method for Producing 1,2-Propylene Glycol using Bio-based Glycerol. United States patent 7586016 B2. 2009 Sep 8.

Davyprotech.com. Licensed Processes Propylene Glycol [Internet]. Johnson Matthey Davy Technologies Limited 2014 [cited 2015 Feb 28]. Available from: http://www.davyprotech.com/what-we-do/licensed-processes-and-core-technologies/licensed-processes/propylene-glycol/specification/.

Ding Z, Chiu J, Jin W, inventors; GTC Technology US LLC, assignee. Process for Converting Glycerin into Propylene Glycol. United States patent 08394999 B2. 2013 Mar 12.

Dow.com. Product Safety Assessment [Internet]. Midland: The Dow Chemical Company; c1995-2015a [cited 2015 Feb 26]. Available from: http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_091a/0901b8038091a41a.pdf?filepath=productsafety/pdfs/noreg/233-00490.pdf&fromPage=GetDoc.

Dow.com. Products [Internet]. Midland: The Dow Chemical Company; c1995-2015b [cited 2015 Feb 26]. Available from: http://www.dow.com/propyleneglycol/products/.

Icis.com. Oleochemicals: Oleon enters glycerin-based propylene glycol [Internet]. Surrey: Reed Business Information Limited; c2015a [cited 2015 Feb 26]. Available from: http://www.icis.com/resources/news/2012/07/16/9577645/oleochemicals-oleon-enters-glycerin-based-propylene-glycol/.

Icis.com. Chemical Profile Hydrogen [Internet]. Surrey: Reed Business Information Limited; c2015b [cited 2015 Feb 26]. Available from: http://www.icis.com/resources/news/2005/12/08/190713/chemical-profile-hydrogen/.

Icis.com. Caustic Soda Latin America [Internet]. Surrey: Reed Business Information Limited; c2015c [cited 2015 Feb 26]. Available from: http://www.icis.com/chemicals/caustic-soda/latin-america/?tab=tbc-tab2.

Icis.com. Indicative Chemical Prices [Internet]. Surrey: Reed Business Information Limited; c2015d [cited 2015 Feb 26]. Available from: http://www.icis.com/chemicals/channel-info-chemicals-a-z/.

Icis.com. Figure depreciation under MACRS [Internet]. Surrey: Reed Business Information Limited; c2015e [cited 2015 Feb 26]. Available from: http://www.irs.gov/publications/p946/ch04.html.

Interview with Dave Wegerer on February 25, 2014.

Interview with Dow Chemical on February 13, 2014.

Kostick DS. Sodium Sulfate [Internet]. Reston: United States Geological Survey [cited 2015 Feb 26]. Available from: http://minerals.usgs.gov/minerals/pubs/commodity/sodium_sulfate/620496.pdf.

Kpmg.com. Corporate Tax Rates Table [Internet]. Amsterdam: KPMG International Cooperative; c2015 [cited 2015 Feb 28]. Available from: http://www.kpmg.com/global/en/services/tax/tax-tools-and-resources/pages/corporate-tax-rates-table.aspx.

Lme.com. LME Cobalt [Internet]. London: The London Metal Exchange Limited; c2015 [cited 2015 Feb 26]. Available from: https://www.lme.com/en-gb/metals/minor-metals/cobalt/.

Meglobal.biz. MEG Sales Specifications [Internet]. Washington, D.C.: MEGlobal [cited 2015 Feb 26]. Available from: http://www.meglobal.biz/monoethylene-glycol/sales-specs.

Nizamoff AJ. Green Glycols and Polyols [Internet]. Wheaton: Nexant Inc.; c2011- [updated 2010 Dec; cited 2015 Feb 28]. Available from: http://thinking.nexant.com/sites/default/files/report/field_attachment_abstract/201012/0910S8_abs.pdf.

Oanda.com. Historical Exchange Rates [Internet]. Toronto: OANDA Corporation; c1996-2015 [cited 2015 Feb 26]. Available from: http://www.oanda.com/currency/historical-rates/.

Oleoline.com. Glycerine Market Report [Internet]. Montmorency: HB International SAS; 2012.

Prweb.com. China to Lead PG Market Through 2017, According to Merchant Research & Consulting Ltd Study Available at MarketPublishers.com [Internet]. London: Vocus PRW Holdings, LLC.; c1997-2015 [cited 2015 Feb 28]. Available from: http://www.prweb.com/releases/2013/8/prweb11057161.htm.

Rabello CRK, et al., inventors; Petroleo Brasileiro S.A. Petrobras, assignee. Production of Propylene Glycol from Glycerine. United States patent 20110295044 A1. 2011 Dec 1.

Sigmaaldrich.com. Alternatives for product 39988 Activated Charcoal Norit (FLUKA) [Internet]. St. Louis: Sigma-Aldrich Co. LLC.; c2015 [cited 2015 Feb 26]. Available from: http://www.sigmaaldrich.com/catalog/product/fluka/39988?lang=en&region=US&fromUrlLabel=product%20details.?lang=en&region=US

Srsbiodiesel.com. Glycerin Specifications [Internet]. Temecula: SRS International; c2013- [cited 2015 Feb 28]. Available from: http://www.srsbiodiesel.com/technologies/glycerin-purification/glycerin-specifications/.

The Energy Independence and Security Act of 2007: One Hundred Tenth Congress of the United States of America, Pub. L. No. 110-40 (Dec 19, 2007).

Transparencymarketresearch.com. Glycerol Market By Source (Biodiesel, Fatty Acids & Fatty Alcohols), By Applications (Personal Care, Alkyd Resins, Polyether Polyols, Others), Downstream Opportunities (Propylene Glycol, Epichlorohydrin, 1, 3 Propanediol And Others) - Global Industry Analysis, Size, Share, Trends, Growth And Forecast 2012 - 2018 [Internet]. Transparency Market Research. 2013 March [cited 2015 Feb 28]. Available from: http://www.transparencymarketresearch.com/glycerol.market.html.

Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

Tuck MWM, inventor; Davy Process Technology Limited, assignee. Process for the hydrogenation of glycerol to propylene glycol. United States patent 08227646 B2. 2012 Jul 24.

United States Environmental Protection Agency: Office of Transportation and Air Quality. EPA Proposes 2014 Renewable Fuel Standards, 2015 Biomass-Based Diesel Volume [Internet]. [cited 2015 Feb 28]. Available from: http://www.epa.gov/otaq/fuels/renewablefuels/documents/420f13048.pdf.

Wmo.int. Salvador [Internet]. WMO; c2014 [cited 2015 Feb 28]. Available from: http://worldweather.wmo.int/en/city.html?cityId=1081.

Design G2

2015-02-28T22:10:27Z

Jian: /* Works Cited */

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

=Executive Summary=
Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol. This reaction alone accounted for approximately 65% of total glycerol production in 2011. The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol. After conducting a thorough review of the literature, a process was developed based on existing UOP patented technology. This process produces propylene glycol via hydrogenolysis of glycerol. The reaction is carried out at 370 °F and 800 psi, which results in 85% conversion of glycerol with a 91% selectivity to propylene glycol, balance ethylene glycol. The main product is purified to 99.8 wt% to meet USP/EP grade. The main byproduct, ethylene glycol, is sold at 99.9 wt%. The process was simulated in Aspen HYSYS V7.3 to determine material balances and overall energy requirements. The process uses 16,919 tons of crude glycerol a year to produce 9,601 tons of propylene glycol and 759 tons of ethylene glycol year. This requires 823,680 tons of water, 609,840 tons of steam and 229,680 kWh a year. The sizing and cost analysis for each of the individual machines and utilities as well as the overall economic analysis have also been examined. The project is estimated to cost 7.63 $MM in capital and 12.3 $MM annual cost of production. The total project revenue comes out to 25.9 $MM each year. After an economic analysis the process was determined to have a 10 year NPV of 4.11 $MM and 20 year NPV of 7.9 $MM with respective IRR of 30% and 34%. These numbers were calculated using 20% cost of capital, a 34% tax rate and a 10 year MACRS depreciation. The project was deemed to be highly profitable and is recommended to move forward when possible.

=Introduction=
Various political, economic, and environmental concerns over the past decades have led to a desire to decrease dependence on fossil fuels for energy. One alternative is biofuel, or fuel derived from living organisms. Several countries and organizations have worked to promote the use of biofuels. In the United States, the Energy Independence and Security Act (EISA) of 2007 mandated that the volume of renewable fuels blended into transportation fuels be 36 billion gallons by 2022 (The Energy Independence and Security Act of 2007, 2007). Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol (Davyprotech.com). This reaction alone accounted for approximately 65% of total glycerol production in 2011 (Transparencymarketresearch.com). The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol.

=Design Basis=

==Market Analysis==

The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $200/ton (Alibaba.com; Bozell and Petersen, 2010). As shown in Figure 1, the supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum (Oleoline.com).

[[File:Glycerol.png]]

''Figure 1. Global glycerine production in various industrial sectors.''

The production grades of glycerol are crude, technical grade, and USP (United States Pharmaceutical) grade. Crude glycerol comes from production of biodiesel and contains 40-88% glycerol with significant amounts of salt, water, soaps, and methanol. Technical grade glycerol is a refined product with a minimum 98% glycerol content and no salt, soaps, methanol, or other contaminants. USP grade glycerol is a pharmaceutical grade for use in the food, pharmaceutical, and cosmetics industries (Srsbiodiesel.com).

Commercial sources of glycerol other than biodiesel production include fatty acids, fatty alcohols and from the soap industry via the saponification process (Bozell and Petersen, 2010). Glycerol is recognized as safe for animals and humans and environmentally benign, with no significant environmental regulations.

Propylene glycol is conventionally produced using propylene oxide. It is, therefore, sensitive to the price and availability of petroleum and associated products (Davyprotech.com). For this reason, propylene glycol is relatively expensive at around $2500/ton (Interview with Dow Chemical). Supply of propylene glycol struggles to keep up with an increasing annual global demand currently at 1.8m tons (Prweb.com). The ability to isolate propylene glycol production from petroleum by using inexpensive glycerol as a feedstock would be hugely advantageous.

Propylene glycol is used in several applications, including the food, pharmaceutical, and cosmetics industries, as well as in liquid detergents, functional fluids, and unsaturated polyesters (Nizamoff). The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity) (Oleoline.com). Like glycerol, propylene glycol is recognized as safe for animals and humans. Because propylene glycol is biodegradable, it is not considered harmful to the environment and, thus, there are no significant environmental regulations.

==Process Technology==
Several different processes have been proposed for the conversion of glycerol to propylene glycol. These include UOP (Bricker and Leonard, 2012), Davy Process Technology (Tuck, 2012), GTC Technology (Ding et al., 2013), the Lanzhou Institute process (Cui et al., 2009), the Petroleo Brasileiro (Rabello et al., 2011) process, and ADM (Bloom, 2011). These methods all employ catalytic hydrogenolysis and proceed using the same general pathway, show in Figure 2.

[[File:BFD.PNG]]

''Figure 2.'' Block Flow Diagram of process alternatives

====Pre-Treatment====

: The production of propylene glycol from glycerol requires technical grade glycerol, which means a crude glycerol feed must undergo pre-treatment before entering the reactor. For different grades of glycerol the specific process will change, but it will generally be necessary for feeds to be purified, mixed, and heated before high purity glycerol is sent to the synthesis stage. In the GTC process, glycerol, hydrogen and methanol are mixed and heated to anywhere from 150 °C to 240 °C, at pressures between 20 and 80 atm. The preferred composition of the mixture assumes an already pure glycerol feed to be mixed, so any glycerol purchased at lower purities must be distilled to purity before entering the mixer and heater. The Lanzhou and Petroleo Brasileiro processes describe vacuum filtration and distillation of crude glycerol to remove impurities such as sodium, chloride, sulfur and phosphorous salts, fatty acids, phospholipids, glycerides, soaps and biodiesel residues. Any of these impurities can kill the catalyst used downstream. The treated glycerol purity is between 90 – 100%.

====Synthesis====

:In all process technologies considered, the basis of the synthesis is hydrogenolysis of glycerol via packed bed reactors with some form of a catalyst, usually copper based. This reaction is shown in Figure 3. In some cases, the process allows for more reactors to be used in series to achieve a higher conversion. Much of the variation in the processes being examined is based on different operating conditions and the desired purity of the product, propylene glycol.

:[[File:Reaction.PNG]]
:''Figure 3.'' Catalytic hydrogenolysis of glycerol to propylene glycol

====Separation====

:A series of separations is used to separate by-products from propylene glycol. Three step distillations are common; some procedures allow for additional steps, which can change the purity of the product. Common byproducts that need to be separated are methanol, acetol, water, and various other minor alcohol solutions.

==Site Conditions and Capacity==

In the United States, the EPA biofuel mandate for 2014 will be reduced from 18.15 billion gallons to 15-15.52 billion gallons (United States Environmental Protection Agency), so the production of biodiesel will decrease, decreasing the supply of crude glycerol in the United States. In South America, Argentina and Brazil are the largest producers of biodiesel, with production in Brazil growing at the fastest rate. It is estimated that 25-30% of Brazilian glycerol production went to drain in 2010 and 2011, indicating a large supply of inexpensive feedstock (Oleoline.com). Building a facility in Salvador da Bahia, Brazil not only enables access to this supply of inexpensive glycerol, but also provides access to a port city and thus allows export of propylene glycol to high demand markets such as China and the U.S. Additional benefits of building in Brazil include the lower corporate tax rate at 34% compared to 40% in the United States (Kpmg.com) and the temperate climate with an almost constant average temperature of 80 °F (Wmo.int). Dow Chemical currently operates a conventional propylene glycol facility near Salvador, indicating a potentially strong market in the area (Dow.com). The capacity selected for this project is 10,000 ton/year. Current plants using comparable technology, such as ADM and Oleon operate at 100,000- and 200,000-tons, respectively (Icis.com, a). The plant capacity is therefore relatively small, which leaves room for increased production.

==Process Model Basis and Assumptions==

===Reactor===

The process is based on the design outlined by UOP (Bricker and Leonard, 2012). The reaction is catalytic hydrogenolysis of glycerol to propylene glycol over a Co/Pd/Re catalyst consisting of 2.5 wt% Co, 0.4 wt% Pd, and 2.4 wt% Re on NORIT ROX 0.8. The catalyst was reduced at 320 °C in the presence of only H2 prior to use in the reactor. The reaction is carried out at 225.6 °C and 5516 kPa with a 1.17 LHSV. The feed enters the reactor at a Hydrogen to glycerol feed ratio of 2.5:1 and at a pH of 12. At these reactor conditions glycerol conversion and selectivities toward propylene glycol and ethylene glycol are 85%, 91%, and 9%, respectively. The upper bound for reactor methanol concentration was set at 7 wt% to maintain catalyst performance according to specifications outlined by UOP (Bricker and Leonard, 2012).

===Feedstocks and Products===

The reactor feed glycerol (including pre-treated and recycled glycerol) is at 23.16 °C and 5516 kPa and has a composition of 37.77 wt% glycerol, 54.42 wt% water, .77 wt% NaOH, 3.36 wt% sodium sulfate, 3.63 wt% methanol, and .04 wt% acetic acid (Bricker and Leonard, 2012). Hydrogen gas is purchased at 187.8 °C and 5516 kPa. Our main product, propylene glycol, can be sold at industrial grade purity of 99.5 wt% or USP grade purity of 99.8 wt% (Dow.com). One of our byproducts, ethylene glycol, can be sold at a variety of grades, including Polyester grade (99.9 wt%) and Industrial grade (99.1 wt%) (Meglobal.biz).

=Process Overview=

The process flow diagram (PFD) can be found in Figure 4. Incoming glycerol is a byproduct of biodiesel production, usually 40 to 85% glycerol, so it contains fatty acids that must be removed before contacting the fixed-bed reactor catalyst. M-101 mixes the incoming feed with sulfuric acid to remove the fatty acids and produce acidulated glycerol. Acidulated glycerol can contain some amount of methanol, sodium, potassium, sulfur, iron, nickel, chloride or trace impurities. The presence of such impurities in small enough amounts will not negatively affect the production of propylene glycol. The best way to ensure the glycerol mixture will be usable is to ensure that methanol content is <1.5% by weight. The acidulated glycerol is then moved to mixer M-102, where it is contacted with 1.77 wt% aqueous sodium hydroxide. This mixer will increase pH to ~12; a basic glycerol solution will have a much higher selectivity towards propylene. The pH corrected glycerol stream is then heated to 148.9 °C and mixed with water and glycerol recycle streams in M-103. The outgoing glycerol mixture is then mixed with compressed hydrogen gas in a 2.5:1 hydrogen to glycerol mole ratio. The hydrogen comes from an external gas feed. The resulting liquid/gas mixture is sent to the fixed-bed reactor R-101.

[[File:PFD_final.png|1100px]]

''Figure 4. Process Flow Diagram for the production of propylene glycol.''

Hydrogenolysis of glycerol to propylene glycol is carried out in R-101 at 187.8 °C and 5516 kPa. Due to the exothermic nature of the reaction, it is necessary to provide a quench gas stream. In this case, the recycled hydrogen comes in at 72.8 °C, which maintains the reactor temperature at 187.8 °C. The catalyst utilized is a Pd/Co/Re on NORIT ROX 0.8, which provides an 85% conversion of glycerol, with a 91% selectivity to propylene glycol at the given operating conditions. The reactor effluent contains propylene glycol, unreacted glycerol and other byproducts and hydrogen gas. The effluent is sent to V-101, a flash evaporator, where the hydrogen gas is removed from the stream and split into two directions: to be sent off as waste and to be recycled. The waste stream is useful to remove any unwanted gasses that may accumulate over repeated reaction cycles. The resulting propylene glycol mixture is then sent to V-102 for separation and purification.

V-102, a fractionation tower, removes water and C2 alcohols from the propylene glycol reactor effluent. The overhead stream, containing 96 wt% water and balance C2 alcohols, is recycled. The bottoms of V-102 contain water-free propylene glycol, which is then sent to V-103, another fractionation tower which will separate the desired product from the unreacted glycerol and other byproducts. The overhead stream contains 92.6 wt% propylene glycol. The bottoms stream contains unreacted glycerol, ethylene glycol, sodium salts and other impurities. This is sent to F-101, a solid/liquid filter that will remove the solid salt impurities for disposal. The resulting purified liquid stream can be recycled to the beginning of the process and mixed with incoming feed in M-103.

The overheads of V-103 are sent to V-104, which will separate propylene glycol from ethylene glycol. The resultant overheads are 99.8 wt% propylene glycol, which is sent to a storage tank. Additionally, the bottoms are 99.9 wt% ethylene glycol, which is also stored in a tank.

=Process Simulation=

The process is modeled in Aspen HYSYS V7.3 using the non-random two-liquid (NRTL) model as the fluid package, the results of which are shown in Figure 5.

[[File:hysys.png|1100px]]

''Figure 5. HYSYS simulation for the production of propylene glycol.''

=Optimization=

Simple distillation columns in HYSYS were used to find initial estimates for tray numbers, reflux ratios, and optimal feed stage location. Once complex columns were simulated, these specifications were further optimized. Liquid returned to columns via reflux is cooler than up-flowing vapors. Heat transfer between the two components improves the efficacy of the distillation tower, reducing the number of trays needed. However, if a column is operated in total reflux, no product will ever be collected. The price of each column, utilities costs, product yields were optimized by testing several combinations of reflux ratios and tray numbers. The temperature of the inlet stream and component fractions should be similar to the tray the feed enters on. This knowledge was used to optimize the feed tray numbers for each distillation column, decreasing the number of trays needed, the cost of utilities, and increasing the product purity.

Reactor Cost was optimized using Solver in Microsoft Excel 2010. The cost accounted for the pressure drop across the reactor (Ergun equation), minimum volume necessary to meet target LHSV, and design specifications for pressure vessels including wall thickness and diameter, and minimum heat transfer specifications such as area, jacket spacing, jacket type, and heat transfer fluid type. Also, several materials were evaluated, including SS304 and SS407, to find the lowest overall cost.

=Waste Streams=

The water purge is a dilute aqueous waste stream and will be treated in a wastewater facility at a cost of $1.5/t. The hydrogen and glycerol purge can be used as heating fuels due to their high heating values. This will offset waste treatment costs as well as fuel costs. If the price of heating fuel is taken to be $4.50/GJ (Interview with Dave Wegerer), this results in savings of $638.10/t H2 and $68/t Glycerol purge. The solid waste, Na2SO4, can be sold at around $100/t (Kostick).

=Equipment Costs=
Figure 6 below shows the approximated costs of each of the pieces of equipment calculated using Aspen Economic Evaluator v7.3.1. The major components running through the equipment are not corrosive, except basic water. In addition most of the vessels are under fairly standard temperatures and pressures. The key exception is the jacketed reactor, which is subject to extreme conditions. The selection of SS407 allowed for a cheaper reactor as compared to SS304 due to the higher tensile strength. The total ISBL equipment cost is 4.8 $MM in 2010 Gulf Coast USD. The NF cost index is 2250 in 2010 and will conservatively be 2050 in 2014 (Towler and Sinnott, 2013), which adjusts project cost to 5.33 $MM in 2014 Gulf Coast USD. The 2003 location factor for Brazil is 1.14 (Towler and Sinnott, 2013), and the exchange rate in 2003 was 1 Real = $.3402 (Oanda.com). The average rate for the past 3 months has been 1 Real = $.427 (Bloomberg.com, a). The adjusted capital cost for Brazil in 2014 is therefore 7.63 $MM. Since the project is large-volume chemical on a new site, OSBL is taken as 40% of ISBL, or 3.05 $MM. Engineering and contingency costs are taken as 10 and 15%, respectively, of combined ISBL and OSBL costs.

[[File:EquipCosts.PNG]]

''Figure 6.'' Equipment Cost Breakdown

=Prices=

The price of feedstocks crude glycerol and hydrogen are $200/t (Alibaba.com; Bozell and Petersen, 2010) and $1100/t (Icis.com, b). The price of products propylene glycol and ethylene glycol are $2557/t (Interview with Dow Chemical) and $1400/t (Meglobal.biz). The price of consumables NaOH and H2SO4 are $635/t (Icis.com, c) and $80/t (Icis.com, d). The catalyst must be replaced every 2 years, at a cost of 5.13 $MM (Basf.com; Lme.com; Sigmaaldrich.com). The price of electricity has been fluctuating recently due to lack of rainfall, and is taken as 0.202 $/kWh (Bloomberg.com, b). Utilities prices for high pressure steam, medium pressure steam, and cooling water are $14.3/t, $12/t, and $.024/t, respectively (Towler and Sinnott, 2013).

=Fixed Operating Costs=

Based on the plant size, three shift positions with 4.8 operators per shift will comprise the operating labor. A salary of $35,000 is a reasonable estimate of operator wages in Brazil. Supervision is taken as 25% of operating labor, and direct overhead is 45% of labor and supervision. Maintenance is taken as 3% of ISBL Cost, and plant overhead is 65% of labor and maintenance costs. Property and local tax and insurance are both typically 1% of ISBL plus OSBL Cost. Repayment of debt associated with fixed investment is accounted for in the weighted average cost of capital so 0% is taken as fixed cost of production. However, working capital will be funded entirely by debt, so 5% interest of working capital is taken as interest on debt financing.

The plant is scheduled to be constructed over two years, with 40% of capital expenditure being accounted for in year 1. The plan will operate at 70% capacity in year 3 and 100% in the subsequent years. Cost of equity is taken to be 30% based on chemical industry companies (Towler and Sinnott, 2013), adjusting for increased risk in South American ventures. The debt ratio is taken to be 0.4 which allows this project to be financed by corporate bonds that are rated A and above, with a debt cost of capital of 5%. The resulting weighted average cost of capital is therefore 20%. The project will be depreciated using MACRS 10 year depreciation (Icis.com, e) which allows larger tax savings in the near-term, resulting in higher project NPV. The corporate tax rate in Brazil is 34% (Kpmg.com). Working capital is calculated as seven weeks Cash Cost of Production (CCOP) minus two weeks feed plus 1% of Fixed Capital Cost (Towler and Sinnott, 2013).

=Utilities and Pinch Analysis=

The total cost of utilities was found using the energy outputs from HYSYS and known costs of natural gas, water, and electricity in Brazil from commodity indices and surveys from the Brazilian government. The results are presented visually in Figure 7 below. The total utility bill comes to $2,424,000 per year. $1,110,000 from heating gas required to create steam for heating in the process, $1,304,000 in water for both steam generation and cooling water, and approximately $10,000 for electricity to power the pumps and any local offices or break rooms. One important note to consider is that the price of gas in Brazil has risen 40% in the past three months. Continuing fluctuations in energy prices could greatly affect these estimates from year to year.

In order to determine the annual cost of utilities, it was necessary to carry out some heat exchanger design calculations and estimations. After surveying the energy requirement of each exchanger, it was determined that cooling water and steam will be the simplest heat transfer fluids to use, due to the relatively small heat requirements and change in temperature of each process stream. In the case of the three reboilers and three condensers, which are designed with the distillation columns, it was only necessary to find a mass flow rate of steam and water respectively. For the cooling water, once the mass flow rate was calculated, this was sufficient to price. For steam, in addition to purchasing the required mass of water, it was necessary to determine the heat required to raise the steam to the required temperatures. For the one cooler and one heater, we also utilized water and steam, and more thorough design was developed in order to accurately price the two exchangers and to help make a pinch analysis viable.

[[File:Fig4.PNG]]

''Figure 7.'' Utilities Breakdown

=Economic Analysis=

Gross profits are 8.1 $MM from year 4 onward and the project has a simple payback period of 2.6 years. The project Net Present Value (NPV) for 10 and 15 years is 4.1 $MM and 6.8 $MM. The expected return on this project (10 year IRR) is 30.3%, indicating this project is highly profitable and can be scaled up for higher NPV. Accelerating the project schedule to complete the plant in less than 2 years will also greatly increase the NPV.

=Sensitivity Analysis=

A sensitivity analaysis was carried out for a variety of process parameters. For catalyst, PG, HP and MP Steam prices, best- and worst-case were taken as +/- 10% of the base price. The project NPV is most sensitive to the price of Propylene Glycol and Glycerol, which is expected as these are the main product and feedstock. The NPV is also highly sensitive to the cost of capital. The results are presented below, in Figure 8.

[[File:Fig5.PNG]]

''Figure 8.'' Sensitivity Analysis

=Conclusion=

Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years, although there are some existing environmental and safety concerns. Our current plans involve burning an effluent stream in which the key components are hydrogen, ethylene glycol and some fatty acids. In this case an analysis will need to be done in order to determine the extent of the damage to the local air and if a purification step is necessary. The main safety concerns involve the acid streams and the reactor itself. Operators will needs to be thoroughly educated on acid burn precaution and treatment procedures due to the acidic requirements of the streams. The reactor runs at very high pressures and given the exothermic nature of the reaction appropriate steps will need to be taken in order to ensure that runaway reactions can be safely dealt with and pressure relief systems will be put in place. Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years. However, there is definite room for expansion in the design; our low NPV values and high IRR values indicate the ability to leverage economies of scale and dramatically expand our profit margins. As it stands, we recommend maximizing the NPV of the project with full scale optimization. This entails the addition of parallel reaction trains and the inclusion of a heat exchange network to fully maximize our profit margins. A plant layout should be developed along with the inclusion of automated control schemes to better optimize the process operation. The project currently holds great economic potential and with some more detailed engineering, could provide a very high return for our shareholders.

=References=

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:Icis.com. Oleochemicals: Oleon enters glycerin-based propylene glycol [Internet]. Surrey: Reed Business Information Limited; c2015a [cited 2015 Feb 26]. Available from: http://www.icis.com/resources/news/2012/07/16/9577645/oleochemicals-oleon-enters-glycerin-based-propylene-glycol/.

:Icis.com. Chemical Profile Hydrogen [Internet]. Surrey: Reed Business Information Limited; c2015b [cited 2015 Feb 26]. Available from: http://www.icis.com/resources/news/2005/12/08/190713/chemical-profile-hydrogen/.

:Icis.com. Caustic Soda Latin America [Internet]. Surrey: Reed Business Information Limited; c2015c [cited 2015 Feb 26]. Available from: http://www.icis.com/chemicals/caustic-soda/latin-america/?tab=tbc-tab2.

:Icis.com. Indicative Chemical Prices [Internet]. Surrey: Reed Business Information Limited; c2015d [cited 2015 Feb 26]. Available from: http://www.icis.com/chemicals/channel-info-chemicals-a-z/.

:Icis.com. Figure depreciation under MACRS [Internet]. Surrey: Reed Business Information Limited; c2015e [cited 2015 Feb 26]. Available from: http://www.irs.gov/publications/p946/ch04.html.

:Interview with Dave Wegerer on February 25, 2014.

:Interview with Dow Chemical on February 13, 2014.

:Kostick DS. Sodium Sulfate [Internet]. Reston: United States Geological Survey [cited 2015 Feb 26]. Available from: http://minerals.usgs.gov/minerals/pubs/commodity/sodium_sulfate/620496.pdf.

:Kpmg.com. Corporate Tax Rates Table [Internet]. Amsterdam: KPMG International Cooperative; c2015 [cited 2015 Feb 28]. Available from: http://www.kpmg.com/global/en/services/tax/tax-tools-and-resources/pages/corporate-tax-rates-table.aspx.

:Lme.com. LME Cobalt [Internet]. London: The London Metal Exchange Limited; c2015 [cited 2015 Feb 26]. Available from: https://www.lme.com/en-gb/metals/minor-metals/cobalt/.

:Meglobal.biz. MEG Sales Specifications [Internet]. Washington, D.C.: MEGlobal [cited 2015 Feb 26]. Available from: http://www.meglobal.biz/monoethylene-glycol/sales-specs.

:Nizamoff AJ. Green Glycols and Polyols [Internet]. Wheaton: Nexant Inc.; c2011- [updated 2010 Dec; cited 2015 Feb 28]. Available from: http://thinking.nexant.com/sites/default/files/report/field_attachment_abstract/201012/0910S8_abs.pdf.

:Oanda.com. Historical Exchange Rates [Internet]. Toronto: OANDA Corporation; c1996-2015 [cited 2015 Feb 26]. Available from: http://www.oanda.com/currency/historical-rates/.

:Oleoline.com. Glycerine Market Report [Internet]. Montmorency: HB International SAS; 2012.

:Prweb.com. China to Lead PG Market Through 2017, According to Merchant Research & Consulting Ltd Study Available at MarketPublishers.com [Internet]. London: Vocus PRW Holdings, LLC.; c1997-2015 [cited 2015 Feb 28]. Available from: http://www.prweb.com/releases/2013/8/prweb11057161.htm.

:Rabello CRK, et al., inventors; Petroleo Brasileiro S.A. Petrobras, assignee. Production of Propylene Glycol from Glycerine. United States patent 20110295044 A1. 2011 Dec 1.

:Sigmaaldrich.com. Alternatives for product 39988 Activated Charcoal Norit (FLUKA) [Internet]. St. Louis: Sigma-Aldrich Co. LLC.; c2015 [cited 2015 Feb 26]. Available from: http://www.sigmaaldrich.com/catalog/product/fluka/39988?lang=en&region=US&fromUrlLabel=product%20details.?lang=en&region=US

:Srsbiodiesel.com. Glycerin Specifications [Internet]. Temecula: SRS International; c2013- [cited 2015 Feb 28]. Available from: http://www.srsbiodiesel.com/technologies/glycerin-purification/glycerin-specifications/.

:The Energy Independence and Security Act of 2007: One Hundred Tenth Congress of the United States of America, Pub. L. No. 110-40 (Dec 19, 2007).

:Transparencymarketresearch.com. Glycerol Market By Source (Biodiesel, Fatty Acids & Fatty Alcohols), By Applications (Personal Care, Alkyd Resins, Polyether Polyols, Others), Downstream Opportunities (Propylene Glycol, Epichlorohydrin, 1, 3 Propanediol And Others) - Global Industry Analysis, Size, Share, Trends, Growth And Forecast 2012 - 2018 [Internet]. Transparency Market Research. 2013 March [cited 2015 Feb 28]. Available from: http://www.transparencymarketresearch.com/glycerol.market.html.

:Towler G, Sinnott R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design. 2nd ed. Boston: Elsevier; 2013.

:Tuck MWM, inventor; Davy Process Technology Limited, assignee. Process for the hydrogenation of glycerol to propylene glycol. United States patent 08227646 B2. 2012 Jul 24.

:United States Environmental Protection Agency: Office of Transportation and Air Quality. EPA Proposes 2014 Renewable Fuel Standards, 2015 Biomass-Based Diesel Volume [Internet]. [cited 2015 Feb 28]. Available from: http://www.epa.gov/otaq/fuels/renewablefuels/documents/420f13048.pdf.

:Wmo.int. Salvador [Internet]. WMO; c2014 [cited 2015 Feb 28]. Available from: http://worldweather.wmo.int/en/city.html?cityId=1081.

Design S1

2015-02-28T22:08:56Z

Jian: /* References */

Design Report Authors: Michael Gleeson, Thomas Considine, Sean Kelton

Steward: Fengqi You

Date Presented: March 11, 2014

 

==Executive Summary==
The Chemical Intermediary Division ($1) of Evanston Chemical Corporation is interested in evaluating the economic benefit of adding 1,4 Butanediol (BDO) to its already robust offering of chemical intermediaries. It plans on producing 50,000 tonnes of 99.5%wt BDO using a modified Davy Process through a Gas Liquid Induction Reactor (GLIR) with a rare earth metal catalyst. The facility will be located in Lake Providence, LA , due to proximity to raw material productions sites and ease of transportation of the final product.

BDO is produced from Succinic Acid (SUC) by a hydrogenation reaction at very high pressures. This particular process uses a rare earth catalyst to because of the high conversion of SUC and the high selectivity toward BDO. Side products of the reaction include the highly valuable chemicals tetrahydrofuran (THF) and γ-butyrolactone (GBL), as well as water, n-butanol, and various other low value chemicals. The reaction occurs at 165oC and 150 bar, so special attention must be paid to reactor design to account for these extreme conditions.

Aspen HYSYS was used to model this process, and equipment sizes were calculated as specified by Towler. Equipment costs were estimated using Aspen Process Economic Analyzer (formerly known as Icarus). In order to meet the process specifications within the given time-frame, some simplifying assumptions were made that impose limits on the accuracy of the model; specifically, the GLIR was modelled using a conversion reaction. This means that the conversion remained unchanged at unideal operating conditions, which, clearly, is inaccurate. Additionally, only one reaction was modelled; in real world conditions, dozens of reactions would occur within the reactor, which would have a potentially massive effect on the accuracy of this model. Despite these limitations, the possibility of producing BDO for sale in the open market should be investigated because of the extremely encouraging economic potential of this endeavor.

Economic analysis of this process indicates a 10 year NPV of $163M, a 20 year NPV of $258M, and a total capital cost of $17.5M. The variable operational costs are approximately $131M. At a selling point of $3/kg for BDO and $35/kg for GBL, the total revenue will exceed $190M/yr, so it is strongly recommended the ECC pursue this opportunity.

==Introduction==
===Project Justification===
1,4 Butanediol is an important organic chemical used mainly as an intermediate for the production of Tetrahydrofuran (THF), Gamma-Butyrolactone (GBL) and Polybutylene Terephthalate (PBT). In 2011, the global market for BDO reached 1,725.0 kilo tons. Current projections suggest that worldwide BDO consumption will grow to 2550 kilo tons by 2017. The Technology Division of Evanston Chemicals has requested a preliminary design and economic evaluation on the feasibility of producing 1,4 Butanediol from a biomass derived succinic acid.

===Technology Review===
BDO can be produced by hydrogenation of succinic acid in the presence of a catalyst, at high temperatures and pressures (approximately 150-200°C and 20,000 kPa). However, to the best of the authors’ knowledge, there does not exist a means to produce only BDO. Instead, a mixture of THF, GBL, and BDO is produced. The choice of catalyst is the major factor in controlling yields and selectivity of a certain product. Current research suggests that bimetallic catalysts have a stronger activity and lead to higher conversion to BDO. TiO supported 2%Pd/X%Re catalyst and Carbon supported 2%Ru/4%Re catalyst both have been shown to be particularly effective. It is interesting to note that both catalysts contain Re. Research suggests that the synergy between Re and Pd/Ru leads to higher selectivity for BDO. Additionally, the chosen catalyst for this study was a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5 mm carbon support. Taken from an ISP Investments patent from 2011, this catalyst has exceptionally high yields, upwards of 99.7% conversion of succinic acid, as well as high yields of BDO. In total, the percentage conversions of succinic acid to various products are:
BDO: 85.51 wt %
GBL: 2.04 wt %
THF: 9.28 wt %
Butanol: 2.87 wt %
The lifetime of the catalyst is approximately 5 years. Furthermore, multiple reactor types have been discussed in the literature, including CSTRs and PFRs. However, the literature also shows that gas liquid induction reactors are the best for hydrogenation reactions in industry. They are preferred for their safety with respect to explosive gas phase reactants and complete utilization of the gas phase reactant; being especially useful for expensive inputs. These reactors use energy efficient impellers for gas induction and dispersion along with special recovery equipment to prevent waste of the gas phase, thus GLIR was chosen for this study.

===Design Basis===
The plant has been proposed to be built in Lake Providence, Louisiana. This is due primarily to its proximity to suppliers of succinic acid in the south east region, as well as close to distributors by way of the Mississippi River and the Gulf of Mexico. Additionally, the plant has been designed to have a capacity of approximately 50MM kg/yr of BDO production. This will require feeds of compressed hydrogen gas, and an aqueous feed of water and succinic acid, in a 50/50 wt % composition.

==Technical Approach==
The primary tool used to model the plant process was Aspen HYSYS. Because of the non-idealities involved in the NRTL HYSYS fluid package, an additional fluid package was created in Aspen. Additionally, the GLIR reactor chosen was modeled as a conversion reactor. Selectivity and yield of the reactor was modeled based off the specific data from the ISP Investments patent (discussed in Introduction: Technology Review). Although this provided very accurate modeling, the operating pressure and temperature were required to be held constant. This prevented any optimization within the reactor with respect to these operating conditions. The distillation columns were modeled as fractional distillation columns, with bottoms or distillate flow rate, and component recovery as active constraints. Additionally, Aspen Energy Analyzer was used to create the heat exchanger network, which can be seen in the Appendix. The economic analysis was performed in Aspen ICARUS.

[[File:Hysys.JPG]]

Figure 1. Screenshot of Aspen HYSYS process simulation.

As mentioned above, this plant will produce technical grade BDO and GBL, but the THF stream will be treated as waste. Originally, attempts were made to purify the THF stream in order to sell it; this process produces approximately 5M kg/yr, and at a selling point of ~$3.00/kg, this would generate an additional $15M/yr in revenue. However, the stream containing THF also contains water and n-butanol. As shown in Appendix XX, THF and water have a pressure dependent azeotrope; Figures XX1 and XX2 show that the azeotrope can be broken by pressurizing the stream after initial separation and atmospheric pressure. However, the presence of n-butanol makes separation of THF and water impossible; butanol and water have a tight azeotrope that cannot be broken simply by pressurizing the stream. Instead, absorption or ion exchange must be used to purify the stream. After extensive efforts were made to purify the THF, it was decided that the undertaking would not be profitable. In future iterations of this project, redoubled efforts would be made to force separation of THF to generate large revenues.

===Process Description===

There are three main component of our process: pre-treatment, reaction and separation. See Appendix 15 for a detailed PFD of the process to reference.

===Pre-treatment Phase===

In the pretreatment phase of our process we bring all of the components to the correct conditions in order to be fed into the reactor. For example the 50% succinic acid in water feed in pumped to a pressure of 3250 psia and then heated to about 160oC, which are the operating conditions of the gas-liquid induction reactor used in the process. The operating temperature is relatively low in order to promote selectivity toward BDO and prevent other side reactions. At higher temperatures the hydrogenation of succinic acid continues past BDO and creates unwanted products. See Appendix 14 for the full reaction scheme of this process. At this point the feed can be mixed with a recycled steam coming off of our second gas-liquid separator, which is composed of water, BDO and BGL. It was advantageous to combine these two steams entering the reactor because the recycle stream saves excess water that was separated out before the final product and further dilutes the succinic acid concentration, for stabilization purposes, within the feed stream. Furthermore, the excess BDO that is filtered out and would be lost is recycled back into the system to improve the system recovery. Finally the GBL can be further reacted in the presence of hydrogen in order to form BDO, or once again recovered at the end of the process to be purified and sold rather than wasted. Of course the recycled stream must be pressurized and heated to the correct conditions as well, however, we first cool the recycle stream to form a liquid so that it can be pumped to the correct pressure of 3250 psia (rather than compressed as a gas, since compressors are much more expensive) and finally heated back to a temperature of 160oC.
On the other side of the GLIR the hydrogen feed enters the process. Hydrogen purchased at 3000 psia is compressed to 3250 psia and then mixed with recycled hydrogen coming off the top of our first gas-liquid separator. The hydrogen from the top of the separator is split so that some is purged while the rest is recycled (still at high pressure) and mixed with the newly purchased hydrogen. It was necessary to recycle hydrogen because it is such an expensive input, and used in major excess to simply sending all of it out in the purge to a flare would be very wasteful. In future iterations of the project, the energy created from hydrogen burned off at a flare should be captured and used in the heat exchange network (explained later). The mixed streams, still at high pressure, are then heated to 160oC and fed into the reactor.

===Reaction Phase===

The reaction is to take place in a gas-liquid induction reactor, GLIR for short. The GLIR was chosen because it is best suited for multi-phase gas-liquid reactions. In particular the GLIR has special safety features to ensure worker’s safety under intense operating conditions, such as the high pressure used in our reactor, or when the reactant gas is highly combustible, as hydrogen is in our case. Additionally, GLIR’s are known for their complete utilization of the gas feed and great recovery specs with few losses, which is important for an expensive input feed. In our case, hydrogen can cost upwards of $7/kg and so this is a worthwhile investment. The GLIR will be a sort of fluidized bed reactor holding the catalyst with the liquid feed being pumped through downward as the gas bubbles through the liquid upward while an impeller stirs the mixture to increase contact times. Using a catalyst composed of a combination of Pd/Re/Ag/Na, typical for a hydrogenation process, high conversion of succinic acid and selectivity toward BDO can be achieved. Adding Fe to the catalyst has been shown to further increase conversion of succinic acid and selectivity toward BDO and so that will be done as well. Using a 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10% Re catalyst with the balance of the 1.5mm diameter carbon support, we are able to achieve 99.7% conversion of succinic acid with 85.5% selectivity to BDO, 2.04% selectivity to GBL, 9.3% selectivity to THF and the balance to other side products but namely butanol (but also possibly propanol and methane, etc.). The reactor operates isothermally and isobarically at 160oC and 3250 psia. Since the reaction is exothermic a cooling jacket will be placed on the GLIR in order to remove the excess heat generated. The jacket will contain a high heat capacity oil, namely Dowtherm A, that will then be put through a heat exchanger in order to maintain the oil at about 160oC at all times.

===Separation Phase===

The separation of the reactor effluent is the final part of our process. Since the effluent contains so many different components, many different reflux drums (gas-liquid separators) and fractionation columns are necessary. First, the effluent is cooled in a heat exchanger in order to allow for better separation of the hydrogen and liquid products in the reflux drum that follows where the hydrogen is taken out of the effluent mixture and either burned or recycled as described above. Next the remaining products and sent to a let-down valve to depressurize them and then reheated to promote better separation in the distillation column that follows which will separate out the main wastes (THF, water, butanol) from the main products (GBL, BDO). The first waste stream coming off of the top of this column is cooled and then sent to a waste tank as it is highly concentrated with butanol and THF. The other stream is further depressurized and sent to a distillation column to separate a stream highly concentrated in butanol and THF (as above) out, to be put into a waste container, from a stream that is >99% water which will be let out into the Mississippi River. The bottoms stream from the first fractionation column containing the main products is once again depressurized and heated to promote a better separation and then put into a new reflux drum. Here a stream high in water content is separated and recycled from a stream highly concentrated with the desired products. The non-recycled stream is sent to, yet another, distillation column which separates out our major product, 99.7% BDO in the bottoms from the GBL and water. The distillate stream is, once again, heated for better separation and sent to our last distillation column which separates out our other major product, >99% GBL, out of the bottoms from a water waste stream in the distillate which will also be let out into the Mississippi. Further iterations of the project could look at better ways to separate our products (using less columns/drums) or isolating other side-products to be resold (like THF). Additionally, other ways to handle side-product waste should be explored. Please see Appendix 6 for a closer look at our modeled HYSYS simulation.

===Heat Exchange Network (HEN)===

Since there are 9 streams that must be heated or cooled in our plant as well as a stream from the reactor jacket, a heat exchange network is necessary to minimize our total plant utilities in a heat exchange network (HEN). Using pinch point analysis it was determined that the best network contained 12 total heat exchangers with one stream split using a total of 3.87 x 107 kJ/h of hot utility and 3.99 x 106 kJ/h of total cold utility. These were necessary due to the complex nature of optimizing 10 different process streams needing temperature adjustment while avoiding temperature crosses, etc. Most of the streams exchange energy between different process streams while only one uses a cooling water and five use small amounts of high pressure steam, which account for the utilities needed. For more details of the HEN see Appendix 13. Further iterations of the project should consider adding the duties of the four reboilers and four condensers used on our distillation columns to the heat exchange network. As is, the network only considers the heat exchangers needed for process streams in order to minimize total utilities used within the process, however, a significant portion of our utilities is used in our distillation columns and thus future iterations could further reduce this number and make the plant more profitable by incorporating them into the network.

==Process Flow Diagram & Flow Sheets==
Below is listed a complete flow sheet, with data taken from Aspen HYSYS.

Table 1

[[File:Streams.JPG]]

A detailed sizing list of the relevant components is listed below. Of particular interest are the distillation columns, which have heights between 8 and 12 meters. Furthermore, the reactor has a length of 6.2 meters and a diameter of 2.1 meters. A more complete table of sizing and sizing methodologies is listed in the Appendix.

Table 2

[[File:Components.JPG]]

==Economic Analysis==
Table 3

[[File:Econ.JPG]]

Table 3 is a summary of the capital and operating costs required for the production of BDO and GBL. The expenditure on succinic acid clearly stands out; it makes up roughly 80% of the annual operating costs of this plant. The production plant consumes approximately 75.6M kg/yr of succinic acid, and at $1.47/kg, the costs add up quickly. Some other things to note from Table XX; the reactor is the most expensive singular piece of equipment; because it operates at exceedingly high pressure, it has extremely thick walls and is made of a high strength steel alloy. Additionally, the total cost of the heat exchangers is more than $3M; however, the production plant uses twelve heat exchangers, so the average individual cost comes out to a more reasonable $280,000. Lastly, this plant has a high annual utilities cost, mainly because of the 4 distillation columns and the large amount of cooling water necessary to keep the process running at the correct temperature.
Below in Table 4 is a summary of the economic measures of return of this process.

Table 4

[[File:Econ2.JPG]]

As shown clearly in Table 4, this plant has extremely encouraging economic potential, with an average yearly cash flow of $40.8M, a simple payback period of less than 6 months, and a breakeven point of approximately 9 months. These capital projections assume a 2 year construction time, 38% tax rate, 50% capacity in the first year of production, and a 7 year MACRS depreciation method.
Revenue is split into two streams; main product (BDO) and by-product (GBL). The main product revenue is approximately $150M/yr, while the by-product revenue is $40M/yr, despite producing nearly 50 times less GBL than BDO. In future iterations of this design, it may be worthwhile to examine if it is more profitable to convert all of the succinic acid directly to GBL instead of producing the intermediary, BDO.
If the economic returns seem astronomical, it is because they are; no economic investment actually produces these kinds of returns. The extremely favorable prediction could stem from several sources of error; supply and demand, bulk pricing, waste removal, and side reactions. The yearly supply of BDO is approximately 1M metric tons, meaning that this plant would produce 5% of the world’s supply. If the supply of BDO outpaced the demand, the selling price would fall, cutting into main product revenues. Additionally, the estimate of GBL selling price was based off a per kg price; if bulk pricing were used, the selling price of GBL would be between 40-50% lower than the price used. In addition to economic discontinuities, the problem of waste removal was never fully solved. Based on past estimates, waste removal could cost as must as $10M/year, further reducing the profitability of this plant. Lastly, the process of BDO synthesis was simplified for modelling purposes. In actual production, many side reactions would occur; driving down conversion and increasing separation costs.

A sensitivity analysis was performed on all important variables.

[[File:Sensitivity.JPG]]

Figure 1: Sensitivity analysis

Figure 1 shows that the profitability of the plant (based on the 10 year NPV), is most sensitive to the selling price of BDO and GLB, the cost of raw materials, and the construction time. It is least sensitive to changes in the utilities cost and fixed capital costs. It is clear from the figure that this undertaking is profitable in the face of any singular change. However, if several of these variables react unfavorably to the coming economic climate, the plant could potentially make very little money. For example, if the construction time doubles (which happens frequently) and the selling prices of BDO and GBL are driven down by market saturation, the plant could have a 10 year NPV falls to approximately 0.

==Conclusion==
To conclude, this project is highly feasible, and our company stands to make a very high profit from the construction of this plant. Based on a two year construction time, a 38% tax rate, and 50% production over the first year, our simple payback period would be 0.45 years, with yearly revenue of over $190M. We strongly recommend Evanston Chemical to move forward with this facility. However, there are key next steps to be considered. First, a more detailed reaction scheme for the reactor is required. This scheme must be able to handle variable operating pressure and temperature, as well as contain a more detailed and complete incorporation of side reactions. Namely, the reaction of GBL to BDO is a necessary consideration. Moreover, a fully life cycle analysis and environmental health and safety analysis will be required. The removal of waste will also need to be addressed. Additionally, profits may be increased by performing a plant wide optimization project. Also, the assumption of a 5 year catalyst lifetime will need to be addressed in more detail, as the high cost of this component will greatly affect the bottom line. Another factor which may affect the overall profitability is the flocculating prices of rare metals, which make up the catalyst. Also, the market price of these commodity chemicals will almost certainly be affected by a 10% influx of global supply. Finally, while we have planned on also selling GBL, looking into purifying the THF will also be profitable.

==Appendices==
===Appendix 1===
Sizing and construction information.

[[File:Sizing and Construction Info.JPG]]

===Appendix 2===
Equipment Costs

[[File:Equipment Costs.JPG]]

===Appendix 3===
Economic Summary

[[File:Assorted Economic Data.JPG]]

===Appendix 4===
Energy Stream Summary

[[File:Energy Stream Table.JPG]]

===Appendix 5===
HYSYS Simulation

[[File:HYSYS Simulation.JPG]]

===Appendix 6===
Stream Summary Table

[[File:Stream Summary Table.JPG]]

===Appendix 7===
Summary of HYSYS stream compositions.

[[File:Stream Composition Table.JPG]]

===Appendix 8===
Heat exchanger network.

[[File:Heat Exchanger Network.jpg]]

===Appendix 9===
Reaction mechanism summary

[[File:Reaction Mechanism.jpg]]

===Appendix 10===
Process Flow Diagram

[[File: PFDFinal.jpg]]

==References==
:Alibaba.com [Internet]. Hangzhou: Alibaba.com; c1999-2015 [cited 2014 Mar 3].

:Bhattacharyya A, Manila MD, inventor; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-butanediol. United States Patent US 7935834 B2. 2011 May 3.

:Budge JR, Attig TG, Pedersen SE, inventor; The Standard Oil Co., assignee. United States Patent US 6486367 B1. 2002 Nov 26.

:Chung SH, Kim MS, Eom HJ, Lee KY. Hydrogenation of Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts. Proceedings of 2013 AIChE Annual Meeting; 2013 Nov 6; San Francisco, USA.

:Deshpandea RM, Buwaa VV, Rodea CV, Chaudharia RV, Millsb PL. Tailoring of activity and selectivity using bimetallic catalyst in hydrogenation of succinic acid. Catal Commun. 2002 July;3(7):269–74.

:Ly BK et al. Effect of Addition Mode of Re in Bimetallic Pd-Re/TiO2 Catalysts Upon the Selective Aqueous-Phase Hydrogenation of Succinic Acid to 1,4 Butanediol. Top Catal. 2012 July;55:466-73.

:Minh DP, Besson M, Pinel C, Fuertes P, Petitjean C. Aqueous-Phase Hydrogenation of Biomass-Based Succinic Acid to 1,4-Butanediol Over Supported Bimetallic Catalysts. Top Catal. 2010 Sep;53:1270-3.

:Newmultifabengineers.com. Hydrogenator, Grease Kettle Manufacturers India–New Multifab Engineers Pvt Ltd–Hydrogenator, Grease Kettle Manufacturers from India [Internet]. Maharashtra: New Multifab Engineers Pvt Ltd.; c2015 [cited 2015 Feb 26]. Available from: http://www.newmultifabengineers.com/hydrogenator/.

:Orbichem.com. Chemical Market Insight & Foresight-On A Single Page 1,4-Butanediol [Internet]. Tecnon OrbiChem; c2004-15 [cited 2015 Feb 26]. Available from: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf.

:Sigmaaldrich.com [Internet]. St. Louis: Sigma-Aldrich Co. LLC.; c2015 [cited 2014 Mar 3].

:Smith R, Varbanov P. What's the price of steam? Chem Eng Prog. 2005 July:29-33.

:Wisbiorefine.org. Biobased Products: Succinic Acid [Internet]. Wisconsin Biorefining Development Initiative; c2004-10 [cited 2015 Feb 26]. Available from: http://www.wisbiorefine.org/prod/sacid.pdf.

Design G2

2015-02-28T21:02:41Z

Jian: /* Works Cited */

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

=Executive Summary=
Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol. This reaction alone accounted for approximately 65% of total glycerol production in 2011. The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol. After conducting a thorough review of the literature, a process was developed based on existing UOP patented technology. This process produces propylene glycol via hydrogenolysis of glycerol. The reaction is carried out at 370 °F and 800 psi, which results in 85% conversion of glycerol with a 91% selectivity to propylene glycol, balance ethylene glycol. The main product is purified to 99.8 wt% to meet USP/EP grade. The main byproduct, ethylene glycol, is sold at 99.9 wt%. The process was simulated in Aspen HYSYS V7.3 to determine material balances and overall energy requirements. The process uses 16,919 tons of crude glycerol a year to produce 9,601 tons of propylene glycol and 759 tons of ethylene glycol year. This requires 823,680 tons of water, 609,840 tons of steam and 229,680 kWh a year. The sizing and cost analysis for each of the individual machines and utilities as well as the overall economic analysis have also been examined. The project is estimated to cost 7.63 $MM in capital and 12.3 $MM annual cost of production. The total project revenue comes out to 25.9 $MM each year. After an economic analysis the process was determined to have a 10 year NPV of 4.11 $MM and 20 year NPV of 7.9 $MM with respective IRR of 30% and 34%. These numbers were calculated using 20% cost of capital, a 34% tax rate and a 10 year MACRS depreciation. The project was deemed to be highly profitable and is recommended to move forward when possible.

=Introduction=
Various political, economic, and environmental concerns over the past decades have led to a desire to decrease dependence on fossil fuels for energy. One alternative is biofuel, or fuel derived from living organisms. Several countries and organizations have worked to promote the use of biofuels. In the United States, the Energy Independence and Security Act (EISA) of 2007 mandated that the volume of renewable fuels blended into transportation fuels be 36 billion gallons by 2022 (The Energy Independence and Security Act of 2007, 2007). Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol (Davyprotech.com). This reaction alone accounted for approximately 65% of total glycerol production in 2011 (Transparencymarketresearch.com). The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol.

=Design Basis=

==Market Analysis==

The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $200/ton (Alibaba.com; Bozell and Petersen, 2010). As shown in Figure 1, the supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum (Oleoline.com).

[[File:Glycerol.png]]

''Figure 1. Global glycerine production in various industrial sectors.''

The production grades of glycerol are crude, technical grade, and USP (United States Pharmaceutical) grade. Crude glycerol comes from production of biodiesel and contains 40-88% glycerol with significant amounts of salt, water, soaps, and methanol. Technical grade glycerol is a refined product with a minimum 98% glycerol content and no salt, soaps, methanol, or other contaminants. USP grade glycerol is a pharmaceutical grade for use in the food, pharmaceutical, and cosmetics industries (Srsbiodiesel.com).

Commercial sources of glycerol other than biodiesel production include fatty acids, fatty alcohols and from the soap industry via the saponification process (Bozell and Petersen, 2010). Glycerol is recognized as safe for animals and humans and environmentally benign, with no significant environmental regulations.

Propylene glycol is conventionally produced using propylene oxide. It is, therefore, sensitive to the price and availability of petroleum and associated products (Davyprotech.com). For this reason, propylene glycol is relatively expensive at around $2500/ton (Interview with Dow Chemical). Supply of propylene glycol struggles to keep up with an increasing annual global demand currently at 1.8m tons (Prweb.com). The ability to isolate propylene glycol production from petroleum by using inexpensive glycerol as a feedstock would be hugely advantageous.

Propylene glycol is used in several applications, including the food, pharmaceutical, and cosmetics industries, as well as in liquid detergents, functional fluids, and unsaturated polyesters (Nizamoff). The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity) (Oleoline.com). Like glycerol, propylene glycol is recognized as safe for animals and humans. Because propylene glycol is biodegradable, it is not considered harmful to the environment and, thus, there are no significant environmental regulations.

==Process Technology==
Several different processes have been proposed for the conversion of glycerol to propylene glycol. These include UOP (Bricker and Leonard, 2012), Davy Process Technology (Tuck, 2012), GTC Technology (Ding et al., 2013), the Lanzhou Institute process (Cui et al., 2009), the Petroleo Brasileiro (Rabello et al., 2011) process, and ADM (Bloom, 2011). These methods all employ catalytic hydrogenolysis and proceed using the same general pathway, show in Figure 2.

[[File:BFD.PNG]]

''Figure 2.'' Block Flow Diagram of process alternatives

====Pre-Treatment====

: The production of propylene glycol from glycerol requires technical grade glycerol, which means a crude glycerol feed must undergo pre-treatment before entering the reactor. For different grades of glycerol the specific process will change, but it will generally be necessary for feeds to be purified, mixed, and heated before high purity glycerol is sent to the synthesis stage. In the GTC process, glycerol, hydrogen and methanol are mixed and heated to anywhere from 150 °C to 240 °C, at pressures between 20 and 80 atm. The preferred composition of the mixture assumes an already pure glycerol feed to be mixed, so any glycerol purchased at lower purities must be distilled to purity before entering the mixer and heater. The Lanzhou and Petroleo Brasileiro processes describe vacuum filtration and distillation of crude glycerol to remove impurities such as sodium, chloride, sulfur and phosphorous salts, fatty acids, phospholipids, glycerides, soaps and biodiesel residues. Any of these impurities can kill the catalyst used downstream. The treated glycerol purity is between 90 – 100%.

====Synthesis====

:In all process technologies considered, the basis of the synthesis is hydrogenolysis of glycerol via packed bed reactors with some form of a catalyst, usually copper based. This reaction is shown in Figure 3. In some cases, the process allows for more reactors to be used in series to achieve a higher conversion. Much of the variation in the processes being examined is based on different operating conditions and the desired purity of the product, propylene glycol.

:[[File:Reaction.PNG]]
:''Figure 3.'' Catalytic hydrogenolysis of glycerol to propylene glycol

====Separation====

:A series of separations is used to separate by-products from propylene glycol. Three step distillations are common; some procedures allow for additional steps, which can change the purity of the product. Common byproducts that need to be separated are methanol, acetol, water, and various other minor alcohol solutions.

==Site Conditions and Capacity==

In the United States, the EPA biofuel mandate for 2014 will be reduced from 18.15 billion gallons to 15-15.52 billion gallons (United States Environmental Protection Agency), so the production of biodiesel will decrease, decreasing the supply of crude glycerol in the United States. In South America, Argentina and Brazil are the largest producers of biodiesel, with production in Brazil growing at the fastest rate. It is estimated that 25-30% of Brazilian glycerol production went to drain in 2010 and 2011, indicating a large supply of inexpensive feedstock (Oleoline.com). Building a facility in Salvador da Bahia, Brazil not only enables access to this supply of inexpensive glycerol, but also provides access to a port city and thus allows export of propylene glycol to high demand markets such as China and the U.S. Additional benefits of building in Brazil include the lower corporate tax rate at 34% compared to 40% in the United States (Kpmg.com) and the temperate climate with an almost constant average temperature of 80 °F (Wmo.int). Dow Chemical currently operates a conventional propylene glycol facility near Salvador, indicating a potentially strong market in the area (Dow.com). The capacity selected for this project is 10,000 ton/year. Current plants using comparable technology, such as ADM and Oleon operate at 100,000- and 200,000-tons, respectively (Icis.com, a). The plant capacity is therefore relatively small, which leaves room for increased production.

==Process Model Basis and Assumptions==

===Reactor===

The process is based on the design outlined by UOP (Bricker and Leonard, 2012). The reaction is catalytic hydrogenolysis of glycerol to propylene glycol over a Co/Pd/Re catalyst consisting of 2.5 wt% Co, 0.4 wt% Pd, and 2.4 wt% Re on NORIT ROX 0.8. The catalyst was reduced at 320 °C in the presence of only H2 prior to use in the reactor. The reaction is carried out at 225.6 °C and 5516 kPa with a 1.17 LHSV. The feed enters the reactor at a Hydrogen to glycerol feed ratio of 2.5:1 and at a pH of 12. At these reactor conditions glycerol conversion and selectivities toward propylene glycol and ethylene glycol are 85%, 91%, and 9%, respectively. The upper bound for reactor methanol concentration was set at 7 wt% to maintain catalyst performance according to specifications outlined by UOP (Bricker and Leonard, 2012).

===Feedstocks and Products===

The reactor feed glycerol (including pre-treated and recycled glycerol) is at 23.16 °C and 5516 kPa and has a composition of 37.77 wt% glycerol, 54.42 wt% water, .77 wt% NaOH, 3.36 wt% sodium sulfate, 3.63 wt% methanol, and .04 wt% acetic acid (Bricker and Leonard, 2012). Hydrogen gas is purchased at 187.8 °C and 5516 kPa. Our main product, propylene glycol, can be sold at industrial grade purity of 99.5 wt% or USP grade purity of 99.8 wt% (Dow.com). One of our byproducts, ethylene glycol, can be sold at a variety of grades, including Polyester grade (99.9 wt%) and Industrial grade (99.1 wt%) (Meglobal.biz).

=Process Overview=

The process flow diagram (PFD) can be found in Figure 4. Incoming glycerol is a byproduct of biodiesel production, usually 40 to 85% glycerol, so it contains fatty acids that must be removed before contacting the fixed-bed reactor catalyst. M-101 mixes the incoming feed with sulfuric acid to remove the fatty acids and produce acidulated glycerol. Acidulated glycerol can contain some amount of methanol, sodium, potassium, sulfur, iron, nickel, chloride or trace impurities. The presence of such impurities in small enough amounts will not negatively affect the production of propylene glycol. The best way to ensure the glycerol mixture will be usable is to ensure that methanol content is <1.5% by weight. The acidulated glycerol is then moved to mixer M-102, where it is contacted with 1.77 wt% aqueous sodium hydroxide. This mixer will increase pH to ~12; a basic glycerol solution will have a much higher selectivity towards propylene. The pH corrected glycerol stream is then heated to 148.9 °C and mixed with water and glycerol recycle streams in M-103. The outgoing glycerol mixture is then mixed with compressed hydrogen gas in a 2.5:1 hydrogen to glycerol mole ratio. The hydrogen comes from an external gas feed. The resulting liquid/gas mixture is sent to the fixed-bed reactor R-101.

[[File:PFD_final.png|1100px]]

''Figure 4. Process Flow Diagram for the production of propylene glycol.''

Hydrogenolysis of glycerol to propylene glycol is carried out in R-101 at 187.8 °C and 5516 kPa. Due to the exothermic nature of the reaction, it is necessary to provide a quench gas stream. In this case, the recycled hydrogen comes in at 72.8 °C, which maintains the reactor temperature at 187.8 °C. The catalyst utilized is a Pd/Co/Re on NORIT ROX 0.8, which provides an 85% conversion of glycerol, with a 91% selectivity to propylene glycol at the given operating conditions. The reactor effluent contains propylene glycol, unreacted glycerol and other byproducts and hydrogen gas. The effluent is sent to V-101, a flash evaporator, where the hydrogen gas is removed from the stream and split into two directions: to be sent off as waste and to be recycled. The waste stream is useful to remove any unwanted gasses that may accumulate over repeated reaction cycles. The resulting propylene glycol mixture is then sent to V-102 for separation and purification.

V-102, a fractionation tower, removes water and C2 alcohols from the propylene glycol reactor effluent. The overhead stream, containing 96 wt% water and balance C2 alcohols, is recycled. The bottoms of V-102 contain water-free propylene glycol, which is then sent to V-103, another fractionation tower which will separate the desired product from the unreacted glycerol and other byproducts. The overhead stream contains 92.6 wt% propylene glycol. The bottoms stream contains unreacted glycerol, ethylene glycol, sodium salts and other impurities. This is sent to F-101, a solid/liquid filter that will remove the solid salt impurities for disposal. The resulting purified liquid stream can be recycled to the beginning of the process and mixed with incoming feed in M-103.

The overheads of V-103 are sent to V-104, which will separate propylene glycol from ethylene glycol. The resultant overheads are 99.8 wt% propylene glycol, which is sent to a storage tank. Additionally, the bottoms are 99.9 wt% ethylene glycol, which is also stored in a tank.

=Process Simulation=

The process is modeled in Aspen HYSYS V7.3 using the non-random two-liquid (NRTL) model as the fluid package, the results of which are shown in Figure 5.

[[File:hysys.png|1100px]]

''Figure 5. HYSYS simulation for the production of propylene glycol.''

=Optimization=

Simple distillation columns in HYSYS were used to find initial estimates for tray numbers, reflux ratios, and optimal feed stage location. Once complex columns were simulated, these specifications were further optimized. Liquid returned to columns via reflux is cooler than up-flowing vapors. Heat transfer between the two components improves the efficacy of the distillation tower, reducing the number of trays needed. However, if a column is operated in total reflux, no product will ever be collected. The price of each column, utilities costs, product yields were optimized by testing several combinations of reflux ratios and tray numbers. The temperature of the inlet stream and component fractions should be similar to the tray the feed enters on. This knowledge was used to optimize the feed tray numbers for each distillation column, decreasing the number of trays needed, the cost of utilities, and increasing the product purity.

Reactor Cost was optimized using Solver in Microsoft Excel 2010. The cost accounted for the pressure drop across the reactor (Ergun equation), minimum volume necessary to meet target LHSV, and design specifications for pressure vessels including wall thickness and diameter, and minimum heat transfer specifications such as area, jacket spacing, jacket type, and heat transfer fluid type. Also, several materials were evaluated, including SS304 and SS407, to find the lowest overall cost.

=Waste Streams=

The water purge is a dilute aqueous waste stream and will be treated in a wastewater facility at a cost of $1.5/t. The hydrogen and glycerol purge can be used as heating fuels due to their high heating values. This will offset waste treatment costs as well as fuel costs. If the price of heating fuel is taken to be $4.50/GJ (Interview with Dave Wegerer), this results in savings of $638.10/t H2 and $68/t Glycerol purge. The solid waste, Na2SO4, can be sold at around $100/t (Kostick).

=Equipment Costs=
Figure 6 below shows the approximated costs of each of the pieces of equipment calculated using Aspen Economic Evaluator v7.3.1. The major components running through the equipment are not corrosive, except basic water. In addition most of the vessels are under fairly standard temperatures and pressures. The key exception is the jacketed reactor, which is subject to extreme conditions. The selection of SS407 allowed for a cheaper reactor as compared to SS304 due to the higher tensile strength. The total ISBL equipment cost is 4.8 $MM in 2010 Gulf Coast USD. The NF cost index is 2250 in 2010 and will conservatively be 2050 in 2014 (Towler and Sinnott, 2013), which adjusts project cost to 5.33 $MM in 2014 Gulf Coast USD. The 2003 location factor for Brazil is 1.14 (Towler and Sinnott, 2013), and the exchange rate in 2003 was 1 Real = $.3402 (Oanda.com). The average rate for the past 3 months has been 1 Real = $.427 (Bloomberg.com, a). The adjusted capital cost for Brazil in 2014 is therefore 7.63 $MM. Since the project is large-volume chemical on a new site, OSBL is taken as 40% of ISBL, or 3.05 $MM. Engineering and contingency costs are taken as 10 and 15%, respectively, of combined ISBL and OSBL costs.

[[File:EquipCosts.PNG]]

''Figure 6.'' Equipment Cost Breakdown

=Prices=

The price of feedstocks crude glycerol and hydrogen are $200/t (Alibaba.com; Bozell and Petersen, 2010) and $1100/t (Icis.com, b). The price of products propylene glycol and ethylene glycol are $2557/t (Interview with Dow Chemical) and $1400/t (Meglobal.biz). The price of consumables NaOH and H2SO4 are $635/t (Icis.com, c) and $80/t (Icis.com, d). The catalyst must be replaced every 2 years, at a cost of 5.13 $MM (Basf.com; Lme.com; Sigmaaldrich.com). The price of electricity has been fluctuating recently due to lack of rainfall, and is taken as 0.202 $/kWh (Bloomberg.com, b). Utilities prices for high pressure steam, medium pressure steam, and cooling water are $14.3/t, $12/t, and $.024/t, respectively (Towler and Sinnott, 2013).

=Fixed Operating Costs=

Based on the plant size, three shift positions with 4.8 operators per shift will comprise the operating labor. A salary of $35,000 is a reasonable estimate of operator wages in Brazil. Supervision is taken as 25% of operating labor, and direct overhead is 45% of labor and supervision. Maintenance is taken as 3% of ISBL Cost, and plant overhead is 65% of labor and maintenance costs. Property and local tax and insurance are both typically 1% of ISBL plus OSBL Cost. Repayment of debt associated with fixed investment is accounted for in the weighted average cost of capital so 0% is taken as fixed cost of production. However, working capital will be funded entirely by debt, so 5% interest of working capital is taken as interest on debt financing.

The plant is scheduled to be constructed over two years, with 40% of capital expenditure being accounted for in year 1. The plan will operate at 70% capacity in year 3 and 100% in the subsequent years. Cost of equity is taken to be 30% based on chemical industry companies (Towler and Sinnott, 2013), adjusting for increased risk in South American ventures. The debt ratio is taken to be 0.4 which allows this project to be financed by corporate bonds that are rated A and above, with a debt cost of capital of 5%. The resulting weighted average cost of capital is therefore 20%. The project will be depreciated using MACRS 10 year depreciation (Icis.com, e) which allows larger tax savings in the near-term, resulting in higher project NPV. The corporate tax rate in Brazil is 34% (Kpmg.com). Working capital is calculated as seven weeks Cash Cost of Production (CCOP) minus two weeks feed plus 1% of Fixed Capital Cost (Towler and Sinnott, 2013).

=Utilities and Pinch Analysis=

The total cost of utilities was found using the energy outputs from HYSYS and known costs of natural gas, water, and electricity in Brazil from commodity indices and surveys from the Brazilian government. The results are presented visually in Figure 7 below. The total utility bill comes to $2,424,000 per year. $1,110,000 from heating gas required to create steam for heating in the process, $1,304,000 in water for both steam generation and cooling water, and approximately $10,000 for electricity to power the pumps and any local offices or break rooms. One important note to consider is that the price of gas in Brazil has risen 40% in the past three months. Continuing fluctuations in energy prices could greatly affect these estimates from year to year.

In order to determine the annual cost of utilities, it was necessary to carry out some heat exchanger design calculations and estimations. After surveying the energy requirement of each exchanger, it was determined that cooling water and steam will be the simplest heat transfer fluids to use, due to the relatively small heat requirements and change in temperature of each process stream. In the case of the three reboilers and three condensers, which are designed with the distillation columns, it was only necessary to find a mass flow rate of steam and water respectively. For the cooling water, once the mass flow rate was calculated, this was sufficient to price. For steam, in addition to purchasing the required mass of water, it was necessary to determine the heat required to raise the steam to the required temperatures. For the one cooler and one heater, we also utilized water and steam, and more thorough design was developed in order to accurately price the two exchangers and to help make a pinch analysis viable.

[[File:Fig4.PNG]]

''Figure 7.'' Utilities Breakdown

=Economic Analysis=

Gross profits are 8.1 $MM from year 4 onward and the project has a simple payback period of 2.6 years. The project Net Present Value (NPV) for 10 and 15 years is 4.1 $MM and 6.8 $MM. The expected return on this project (10 year IRR) is 30.3%, indicating this project is highly profitable and can be scaled up for higher NPV. Accelerating the project schedule to complete the plant in less than 2 years will also greatly increase the NPV.

=Sensitivity Analysis=

A sensitivity analaysis was carried out for a variety of process parameters. For catalyst, PG, HP and MP Steam prices, best- and worst-case were taken as +/- 10% of the base price. The project NPV is most sensitive to the price of Propylene Glycol and Glycerol, which is expected as these are the main product and feedstock. The NPV is also highly sensitive to the cost of capital. The results are presented below, in Figure 8.

[[File:Fig5.PNG]]

''Figure 8.'' Sensitivity Analysis

=Conclusion=

Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years, although there are some existing environmental and safety concerns. Our current plans involve burning an effluent stream in which the key components are hydrogen, ethylene glycol and some fatty acids. In this case an analysis will need to be done in order to determine the extent of the damage to the local air and if a purification step is necessary. The main safety concerns involve the acid streams and the reactor itself. Operators will needs to be thoroughly educated on acid burn precaution and treatment procedures due to the acidic requirements of the streams. The reactor runs at very high pressures and given the exothermic nature of the reaction appropriate steps will need to be taken in order to ensure that runaway reactions can be safely dealt with and pressure relief systems will be put in place. Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years. However, there is definite room for expansion in the design; our low NPV values and high IRR values indicate the ability to leverage economies of scale and dramatically expand our profit margins. As it stands, we recommend maximizing the NPV of the project with full scale optimization. This entails the addition of parallel reaction trains and the inclusion of a heat exchange network to fully maximize our profit margins. A plant layout should be developed along with the inclusion of automated control schemes to better optimize the process operation. The project currently holds great economic potential and with some more detailed engineering, could provide a very high return for our shareholders.

=Works Cited=

:Alibaba.com [Internet]. Hangzhou: Alibaba.com; c1999-2015 [cited 2015 Feb 28]. Available from: http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=glycerol.

:Basf.com. Engelhard Industrial Bullion (EIB) Prices [Internet]. Ludwigshafen: BASF Corporation; c2015 [cited 2015 Feb 26]. Available from: http://apps.catalysts.basf.com/apps/eibprices/mp/.

:Bloom PD, inventor; Archer Daniels Midland Company, assignee. Hydrogenolysis of Glycerol and Products Produced Therefrom. United States patent WO2008051540 A2. 2011 Apr 19.

:Bloomberg.com. BRAZIL REAL-US DOLLAR Exchange Rate [Internet]. New York: Bloomberg L.P.; c2015a [cited 2015 Feb 26]. Available from: http://www.bloomberg.com/quote/BRLUSD:CUR.

:Bloomberg.com. Brazilian Power Price Surges to Record Amid Dry Spell [Internet]. New York: Bloomberg L.P.; c2015b [cited 2015 Feb 26]. Available from: http://www.bloomberg.com/news/2014-01-31/brazilian-power-price-surges-to-record-amid-dry-spell.html.

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:Cui F, Chen J, Xia C, Kang H, inventors; Lanzhou Institute of Chemical Physics, Chinese Academy of Science, assignee. Method for Producing 1,2-Propylene Glycol using Bio-based Glycerol. United States patent 7586016 B2. 2009 Sep 8.

:Davyprotech.com. Licensed Processes Propylene Glycol [Internet]. Johnson Matthey Davy Technologies Limited 2014 [cited 2015 Feb 28]. Available from: http://www.davyprotech.com/what-we-do/licensed-processes-and-core-technologies/licensed-processes/propylene-glycol/specification/.

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Design G2

2015-02-28T20:59:52Z

Jian: /* Works Cited */

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

=Executive Summary=
Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol. This reaction alone accounted for approximately 65% of total glycerol production in 2011. The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol. After conducting a thorough review of the literature, a process was developed based on existing UOP patented technology. This process produces propylene glycol via hydrogenolysis of glycerol. The reaction is carried out at 370 °F and 800 psi, which results in 85% conversion of glycerol with a 91% selectivity to propylene glycol, balance ethylene glycol. The main product is purified to 99.8 wt% to meet USP/EP grade. The main byproduct, ethylene glycol, is sold at 99.9 wt%. The process was simulated in Aspen HYSYS V7.3 to determine material balances and overall energy requirements. The process uses 16,919 tons of crude glycerol a year to produce 9,601 tons of propylene glycol and 759 tons of ethylene glycol year. This requires 823,680 tons of water, 609,840 tons of steam and 229,680 kWh a year. The sizing and cost analysis for each of the individual machines and utilities as well as the overall economic analysis have also been examined. The project is estimated to cost 7.63 $MM in capital and 12.3 $MM annual cost of production. The total project revenue comes out to 25.9 $MM each year. After an economic analysis the process was determined to have a 10 year NPV of 4.11 $MM and 20 year NPV of 7.9 $MM with respective IRR of 30% and 34%. These numbers were calculated using 20% cost of capital, a 34% tax rate and a 10 year MACRS depreciation. The project was deemed to be highly profitable and is recommended to move forward when possible.

=Introduction=
Various political, economic, and environmental concerns over the past decades have led to a desire to decrease dependence on fossil fuels for energy. One alternative is biofuel, or fuel derived from living organisms. Several countries and organizations have worked to promote the use of biofuels. In the United States, the Energy Independence and Security Act (EISA) of 2007 mandated that the volume of renewable fuels blended into transportation fuels be 36 billion gallons by 2022 (The Energy Independence and Security Act of 2007, 2007). Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol (Davyprotech.com). This reaction alone accounted for approximately 65% of total glycerol production in 2011 (Transparencymarketresearch.com). The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol.

=Design Basis=

==Market Analysis==

The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $200/ton (Alibaba.com; Bozell and Petersen, 2010). As shown in Figure 1, the supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum (Oleoline.com).

[[File:Glycerol.png]]

''Figure 1. Global glycerine production in various industrial sectors.''

The production grades of glycerol are crude, technical grade, and USP (United States Pharmaceutical) grade. Crude glycerol comes from production of biodiesel and contains 40-88% glycerol with significant amounts of salt, water, soaps, and methanol. Technical grade glycerol is a refined product with a minimum 98% glycerol content and no salt, soaps, methanol, or other contaminants. USP grade glycerol is a pharmaceutical grade for use in the food, pharmaceutical, and cosmetics industries (Srsbiodiesel.com).

Commercial sources of glycerol other than biodiesel production include fatty acids, fatty alcohols and from the soap industry via the saponification process (Bozell and Petersen, 2010). Glycerol is recognized as safe for animals and humans and environmentally benign, with no significant environmental regulations.

Propylene glycol is conventionally produced using propylene oxide. It is, therefore, sensitive to the price and availability of petroleum and associated products (Davyprotech.com). For this reason, propylene glycol is relatively expensive at around $2500/ton (Interview with Dow Chemical). Supply of propylene glycol struggles to keep up with an increasing annual global demand currently at 1.8m tons (Prweb.com). The ability to isolate propylene glycol production from petroleum by using inexpensive glycerol as a feedstock would be hugely advantageous.

Propylene glycol is used in several applications, including the food, pharmaceutical, and cosmetics industries, as well as in liquid detergents, functional fluids, and unsaturated polyesters (Nizamoff). The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity) (Oleoline.com). Like glycerol, propylene glycol is recognized as safe for animals and humans. Because propylene glycol is biodegradable, it is not considered harmful to the environment and, thus, there are no significant environmental regulations.

==Process Technology==
Several different processes have been proposed for the conversion of glycerol to propylene glycol. These include UOP (Bricker and Leonard, 2012), Davy Process Technology (Tuck, 2012), GTC Technology (Ding et al., 2013), the Lanzhou Institute process (Cui et al., 2009), the Petroleo Brasileiro (Rabello et al., 2011) process, and ADM (Bloom, 2011). These methods all employ catalytic hydrogenolysis and proceed using the same general pathway, show in Figure 2.

[[File:BFD.PNG]]

''Figure 2.'' Block Flow Diagram of process alternatives

====Pre-Treatment====

: The production of propylene glycol from glycerol requires technical grade glycerol, which means a crude glycerol feed must undergo pre-treatment before entering the reactor. For different grades of glycerol the specific process will change, but it will generally be necessary for feeds to be purified, mixed, and heated before high purity glycerol is sent to the synthesis stage. In the GTC process, glycerol, hydrogen and methanol are mixed and heated to anywhere from 150 °C to 240 °C, at pressures between 20 and 80 atm. The preferred composition of the mixture assumes an already pure glycerol feed to be mixed, so any glycerol purchased at lower purities must be distilled to purity before entering the mixer and heater. The Lanzhou and Petroleo Brasileiro processes describe vacuum filtration and distillation of crude glycerol to remove impurities such as sodium, chloride, sulfur and phosphorous salts, fatty acids, phospholipids, glycerides, soaps and biodiesel residues. Any of these impurities can kill the catalyst used downstream. The treated glycerol purity is between 90 – 100%.

====Synthesis====

:In all process technologies considered, the basis of the synthesis is hydrogenolysis of glycerol via packed bed reactors with some form of a catalyst, usually copper based. This reaction is shown in Figure 3. In some cases, the process allows for more reactors to be used in series to achieve a higher conversion. Much of the variation in the processes being examined is based on different operating conditions and the desired purity of the product, propylene glycol.

:[[File:Reaction.PNG]]
:''Figure 3.'' Catalytic hydrogenolysis of glycerol to propylene glycol

====Separation====

:A series of separations is used to separate by-products from propylene glycol. Three step distillations are common; some procedures allow for additional steps, which can change the purity of the product. Common byproducts that need to be separated are methanol, acetol, water, and various other minor alcohol solutions.

==Site Conditions and Capacity==

In the United States, the EPA biofuel mandate for 2014 will be reduced from 18.15 billion gallons to 15-15.52 billion gallons (United States Environmental Protection Agency), so the production of biodiesel will decrease, decreasing the supply of crude glycerol in the United States. In South America, Argentina and Brazil are the largest producers of biodiesel, with production in Brazil growing at the fastest rate. It is estimated that 25-30% of Brazilian glycerol production went to drain in 2010 and 2011, indicating a large supply of inexpensive feedstock (Oleoline.com). Building a facility in Salvador da Bahia, Brazil not only enables access to this supply of inexpensive glycerol, but also provides access to a port city and thus allows export of propylene glycol to high demand markets such as China and the U.S. Additional benefits of building in Brazil include the lower corporate tax rate at 34% compared to 40% in the United States (Kpmg.com) and the temperate climate with an almost constant average temperature of 80 °F (Wmo.int). Dow Chemical currently operates a conventional propylene glycol facility near Salvador, indicating a potentially strong market in the area (Dow.com). The capacity selected for this project is 10,000 ton/year. Current plants using comparable technology, such as ADM and Oleon operate at 100,000- and 200,000-tons, respectively (Icis.com, a). The plant capacity is therefore relatively small, which leaves room for increased production.

==Process Model Basis and Assumptions==

===Reactor===

The process is based on the design outlined by UOP (Bricker and Leonard, 2012). The reaction is catalytic hydrogenolysis of glycerol to propylene glycol over a Co/Pd/Re catalyst consisting of 2.5 wt% Co, 0.4 wt% Pd, and 2.4 wt% Re on NORIT ROX 0.8. The catalyst was reduced at 320 °C in the presence of only H2 prior to use in the reactor. The reaction is carried out at 225.6 °C and 5516 kPa with a 1.17 LHSV. The feed enters the reactor at a Hydrogen to glycerol feed ratio of 2.5:1 and at a pH of 12. At these reactor conditions glycerol conversion and selectivities toward propylene glycol and ethylene glycol are 85%, 91%, and 9%, respectively. The upper bound for reactor methanol concentration was set at 7 wt% to maintain catalyst performance according to specifications outlined by UOP (Bricker and Leonard, 2012).

===Feedstocks and Products===

The reactor feed glycerol (including pre-treated and recycled glycerol) is at 23.16 °C and 5516 kPa and has a composition of 37.77 wt% glycerol, 54.42 wt% water, .77 wt% NaOH, 3.36 wt% sodium sulfate, 3.63 wt% methanol, and .04 wt% acetic acid (Bricker and Leonard, 2012). Hydrogen gas is purchased at 187.8 °C and 5516 kPa. Our main product, propylene glycol, can be sold at industrial grade purity of 99.5 wt% or USP grade purity of 99.8 wt% (Dow.com). One of our byproducts, ethylene glycol, can be sold at a variety of grades, including Polyester grade (99.9 wt%) and Industrial grade (99.1 wt%) (Meglobal.biz).

=Process Overview=

The process flow diagram (PFD) can be found in Figure 4. Incoming glycerol is a byproduct of biodiesel production, usually 40 to 85% glycerol, so it contains fatty acids that must be removed before contacting the fixed-bed reactor catalyst. M-101 mixes the incoming feed with sulfuric acid to remove the fatty acids and produce acidulated glycerol. Acidulated glycerol can contain some amount of methanol, sodium, potassium, sulfur, iron, nickel, chloride or trace impurities. The presence of such impurities in small enough amounts will not negatively affect the production of propylene glycol. The best way to ensure the glycerol mixture will be usable is to ensure that methanol content is <1.5% by weight. The acidulated glycerol is then moved to mixer M-102, where it is contacted with 1.77 wt% aqueous sodium hydroxide. This mixer will increase pH to ~12; a basic glycerol solution will have a much higher selectivity towards propylene. The pH corrected glycerol stream is then heated to 148.9 °C and mixed with water and glycerol recycle streams in M-103. The outgoing glycerol mixture is then mixed with compressed hydrogen gas in a 2.5:1 hydrogen to glycerol mole ratio. The hydrogen comes from an external gas feed. The resulting liquid/gas mixture is sent to the fixed-bed reactor R-101.

[[File:PFD_final.png|1100px]]

''Figure 4. Process Flow Diagram for the production of propylene glycol.''

Hydrogenolysis of glycerol to propylene glycol is carried out in R-101 at 187.8 °C and 5516 kPa. Due to the exothermic nature of the reaction, it is necessary to provide a quench gas stream. In this case, the recycled hydrogen comes in at 72.8 °C, which maintains the reactor temperature at 187.8 °C. The catalyst utilized is a Pd/Co/Re on NORIT ROX 0.8, which provides an 85% conversion of glycerol, with a 91% selectivity to propylene glycol at the given operating conditions. The reactor effluent contains propylene glycol, unreacted glycerol and other byproducts and hydrogen gas. The effluent is sent to V-101, a flash evaporator, where the hydrogen gas is removed from the stream and split into two directions: to be sent off as waste and to be recycled. The waste stream is useful to remove any unwanted gasses that may accumulate over repeated reaction cycles. The resulting propylene glycol mixture is then sent to V-102 for separation and purification.

V-102, a fractionation tower, removes water and C2 alcohols from the propylene glycol reactor effluent. The overhead stream, containing 96 wt% water and balance C2 alcohols, is recycled. The bottoms of V-102 contain water-free propylene glycol, which is then sent to V-103, another fractionation tower which will separate the desired product from the unreacted glycerol and other byproducts. The overhead stream contains 92.6 wt% propylene glycol. The bottoms stream contains unreacted glycerol, ethylene glycol, sodium salts and other impurities. This is sent to F-101, a solid/liquid filter that will remove the solid salt impurities for disposal. The resulting purified liquid stream can be recycled to the beginning of the process and mixed with incoming feed in M-103.

The overheads of V-103 are sent to V-104, which will separate propylene glycol from ethylene glycol. The resultant overheads are 99.8 wt% propylene glycol, which is sent to a storage tank. Additionally, the bottoms are 99.9 wt% ethylene glycol, which is also stored in a tank.

=Process Simulation=

The process is modeled in Aspen HYSYS V7.3 using the non-random two-liquid (NRTL) model as the fluid package, the results of which are shown in Figure 5.

[[File:hysys.png|1100px]]

''Figure 5. HYSYS simulation for the production of propylene glycol.''

=Optimization=

Simple distillation columns in HYSYS were used to find initial estimates for tray numbers, reflux ratios, and optimal feed stage location. Once complex columns were simulated, these specifications were further optimized. Liquid returned to columns via reflux is cooler than up-flowing vapors. Heat transfer between the two components improves the efficacy of the distillation tower, reducing the number of trays needed. However, if a column is operated in total reflux, no product will ever be collected. The price of each column, utilities costs, product yields were optimized by testing several combinations of reflux ratios and tray numbers. The temperature of the inlet stream and component fractions should be similar to the tray the feed enters on. This knowledge was used to optimize the feed tray numbers for each distillation column, decreasing the number of trays needed, the cost of utilities, and increasing the product purity.

Reactor Cost was optimized using Solver in Microsoft Excel 2010. The cost accounted for the pressure drop across the reactor (Ergun equation), minimum volume necessary to meet target LHSV, and design specifications for pressure vessels including wall thickness and diameter, and minimum heat transfer specifications such as area, jacket spacing, jacket type, and heat transfer fluid type. Also, several materials were evaluated, including SS304 and SS407, to find the lowest overall cost.

=Waste Streams=

The water purge is a dilute aqueous waste stream and will be treated in a wastewater facility at a cost of $1.5/t. The hydrogen and glycerol purge can be used as heating fuels due to their high heating values. This will offset waste treatment costs as well as fuel costs. If the price of heating fuel is taken to be $4.50/GJ (Interview with Dave Wegerer), this results in savings of $638.10/t H2 and $68/t Glycerol purge. The solid waste, Na2SO4, can be sold at around $100/t (Kostick).

=Equipment Costs=
Figure 6 below shows the approximated costs of each of the pieces of equipment calculated using Aspen Economic Evaluator v7.3.1. The major components running through the equipment are not corrosive, except basic water. In addition most of the vessels are under fairly standard temperatures and pressures. The key exception is the jacketed reactor, which is subject to extreme conditions. The selection of SS407 allowed for a cheaper reactor as compared to SS304 due to the higher tensile strength. The total ISBL equipment cost is 4.8 $MM in 2010 Gulf Coast USD. The NF cost index is 2250 in 2010 and will conservatively be 2050 in 2014 (Towler and Sinnott, 2013), which adjusts project cost to 5.33 $MM in 2014 Gulf Coast USD. The 2003 location factor for Brazil is 1.14 (Towler and Sinnott, 2013), and the exchange rate in 2003 was 1 Real = $.3402 (Oanda.com). The average rate for the past 3 months has been 1 Real = $.427 (Bloomberg.com, a). The adjusted capital cost for Brazil in 2014 is therefore 7.63 $MM. Since the project is large-volume chemical on a new site, OSBL is taken as 40% of ISBL, or 3.05 $MM. Engineering and contingency costs are taken as 10 and 15%, respectively, of combined ISBL and OSBL costs.

[[File:EquipCosts.PNG]]

''Figure 6.'' Equipment Cost Breakdown

=Prices=

The price of feedstocks crude glycerol and hydrogen are $200/t (Alibaba.com; Bozell and Petersen, 2010) and $1100/t (Icis.com, b). The price of products propylene glycol and ethylene glycol are $2557/t (Interview with Dow Chemical) and $1400/t (Meglobal.biz). The price of consumables NaOH and H2SO4 are $635/t (Icis.com, c) and $80/t (Icis.com, d). The catalyst must be replaced every 2 years, at a cost of 5.13 $MM (Basf.com; Lme.com; Sigmaaldrich.com). The price of electricity has been fluctuating recently due to lack of rainfall, and is taken as 0.202 $/kWh (Bloomberg.com, b). Utilities prices for high pressure steam, medium pressure steam, and cooling water are $14.3/t, $12/t, and $.024/t, respectively (Towler and Sinnott, 2013).

=Fixed Operating Costs=

Based on the plant size, three shift positions with 4.8 operators per shift will comprise the operating labor. A salary of $35,000 is a reasonable estimate of operator wages in Brazil. Supervision is taken as 25% of operating labor, and direct overhead is 45% of labor and supervision. Maintenance is taken as 3% of ISBL Cost, and plant overhead is 65% of labor and maintenance costs. Property and local tax and insurance are both typically 1% of ISBL plus OSBL Cost. Repayment of debt associated with fixed investment is accounted for in the weighted average cost of capital so 0% is taken as fixed cost of production. However, working capital will be funded entirely by debt, so 5% interest of working capital is taken as interest on debt financing.

The plant is scheduled to be constructed over two years, with 40% of capital expenditure being accounted for in year 1. The plan will operate at 70% capacity in year 3 and 100% in the subsequent years. Cost of equity is taken to be 30% based on chemical industry companies (Towler and Sinnott, 2013), adjusting for increased risk in South American ventures. The debt ratio is taken to be 0.4 which allows this project to be financed by corporate bonds that are rated A and above, with a debt cost of capital of 5%. The resulting weighted average cost of capital is therefore 20%. The project will be depreciated using MACRS 10 year depreciation (Icis.com, e) which allows larger tax savings in the near-term, resulting in higher project NPV. The corporate tax rate in Brazil is 34% (Kpmg.com). Working capital is calculated as seven weeks Cash Cost of Production (CCOP) minus two weeks feed plus 1% of Fixed Capital Cost (Towler and Sinnott, 2013).

=Utilities and Pinch Analysis=

The total cost of utilities was found using the energy outputs from HYSYS and known costs of natural gas, water, and electricity in Brazil from commodity indices and surveys from the Brazilian government. The results are presented visually in Figure 7 below. The total utility bill comes to $2,424,000 per year. $1,110,000 from heating gas required to create steam for heating in the process, $1,304,000 in water for both steam generation and cooling water, and approximately $10,000 for electricity to power the pumps and any local offices or break rooms. One important note to consider is that the price of gas in Brazil has risen 40% in the past three months. Continuing fluctuations in energy prices could greatly affect these estimates from year to year.

In order to determine the annual cost of utilities, it was necessary to carry out some heat exchanger design calculations and estimations. After surveying the energy requirement of each exchanger, it was determined that cooling water and steam will be the simplest heat transfer fluids to use, due to the relatively small heat requirements and change in temperature of each process stream. In the case of the three reboilers and three condensers, which are designed with the distillation columns, it was only necessary to find a mass flow rate of steam and water respectively. For the cooling water, once the mass flow rate was calculated, this was sufficient to price. For steam, in addition to purchasing the required mass of water, it was necessary to determine the heat required to raise the steam to the required temperatures. For the one cooler and one heater, we also utilized water and steam, and more thorough design was developed in order to accurately price the two exchangers and to help make a pinch analysis viable.

[[File:Fig4.PNG]]

''Figure 7.'' Utilities Breakdown

=Economic Analysis=

Gross profits are 8.1 $MM from year 4 onward and the project has a simple payback period of 2.6 years. The project Net Present Value (NPV) for 10 and 15 years is 4.1 $MM and 6.8 $MM. The expected return on this project (10 year IRR) is 30.3%, indicating this project is highly profitable and can be scaled up for higher NPV. Accelerating the project schedule to complete the plant in less than 2 years will also greatly increase the NPV.

=Sensitivity Analysis=

A sensitivity analaysis was carried out for a variety of process parameters. For catalyst, PG, HP and MP Steam prices, best- and worst-case were taken as +/- 10% of the base price. The project NPV is most sensitive to the price of Propylene Glycol and Glycerol, which is expected as these are the main product and feedstock. The NPV is also highly sensitive to the cost of capital. The results are presented below, in Figure 8.

[[File:Fig5.PNG]]

''Figure 8.'' Sensitivity Analysis

=Conclusion=

Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years, although there are some existing environmental and safety concerns. Our current plans involve burning an effluent stream in which the key components are hydrogen, ethylene glycol and some fatty acids. In this case an analysis will need to be done in order to determine the extent of the damage to the local air and if a purification step is necessary. The main safety concerns involve the acid streams and the reactor itself. Operators will needs to be thoroughly educated on acid burn precaution and treatment procedures due to the acidic requirements of the streams. The reactor runs at very high pressures and given the exothermic nature of the reaction appropriate steps will need to be taken in order to ensure that runaway reactions can be safely dealt with and pressure relief systems will be put in place. Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years. However, there is definite room for expansion in the design; our low NPV values and high IRR values indicate the ability to leverage economies of scale and dramatically expand our profit margins. As it stands, we recommend maximizing the NPV of the project with full scale optimization. This entails the addition of parallel reaction trains and the inclusion of a heat exchange network to fully maximize our profit margins. A plant layout should be developed along with the inclusion of automated control schemes to better optimize the process operation. The project currently holds great economic potential and with some more detailed engineering, could provide a very high return for our shareholders.

=Works Cited=

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:Basf.com. Engelhard Industrial Bullion (EIB) Prices [Internet]. Ludwigshafen: BASF Corporation; c2015 [cited 2015 Feb 26]. Available from: http://apps.catalysts.basf.com/apps/eibprices/mp/.

:Bloom PD, inventor; Archer Daniels Midland Company, assignee. Hydrogenolysis of Glycerol and Products Produced Therefrom. United States patent WO2008051540 A2. 2011 Apr 19.

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:Cui F, Chen J, Xia C, Kang H, inventors; Lanzhou Institute of Chemical Physics, Chinese Academy of Science, assignee. Method for Producing 1,2-Propylene Glycol using Bio-based Glycerol. United States patent 7586016 B2. 2009 Sep 8.

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Design G2

2015-02-28T20:58:38Z

Jian: /* Works Cited */

Author: Sean Cabaniss, David Park, Maxim Slivinsky, and Julianne Wagoner (Winter 2014)

Steward: David Chen, Fengqi You

=Executive Summary=
Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol. This reaction alone accounted for approximately 65% of total glycerol production in 2011. The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol. After conducting a thorough review of the literature, a process was developed based on existing UOP patented technology. This process produces propylene glycol via hydrogenolysis of glycerol. The reaction is carried out at 370 °F and 800 psi, which results in 85% conversion of glycerol with a 91% selectivity to propylene glycol, balance ethylene glycol. The main product is purified to 99.8 wt% to meet USP/EP grade. The main byproduct, ethylene glycol, is sold at 99.9 wt%. The process was simulated in Aspen HYSYS V7.3 to determine material balances and overall energy requirements. The process uses 16,919 tons of crude glycerol a year to produce 9,601 tons of propylene glycol and 759 tons of ethylene glycol year. This requires 823,680 tons of water, 609,840 tons of steam and 229,680 kWh a year. The sizing and cost analysis for each of the individual machines and utilities as well as the overall economic analysis have also been examined. The project is estimated to cost 7.63 $MM in capital and 12.3 $MM annual cost of production. The total project revenue comes out to 25.9 $MM each year. After an economic analysis the process was determined to have a 10 year NPV of 4.11 $MM and 20 year NPV of 7.9 $MM with respective IRR of 30% and 34%. These numbers were calculated using 20% cost of capital, a 34% tax rate and a 10 year MACRS depreciation. The project was deemed to be highly profitable and is recommended to move forward when possible.

=Introduction=
Various political, economic, and environmental concerns over the past decades have led to a desire to decrease dependence on fossil fuels for energy. One alternative is biofuel, or fuel derived from living organisms. Several countries and organizations have worked to promote the use of biofuels. In the United States, the Energy Independence and Security Act (EISA) of 2007 mandated that the volume of renewable fuels blended into transportation fuels be 36 billion gallons by 2022 (The Energy Independence and Security Act of 2007, 2007). Biodiesel is a biofuel alternative to petroleum diesel. One of the main pathways of biodiesel production is through transesterification. For each unit of biodiesel converted using this reaction, approximately 10% by weight will be recovered as by-product glycerol (Davyprotech.com). This reaction alone accounted for approximately 65% of total glycerol production in 2011 (Transparencymarketresearch.com). The growing biodiesel market has created an abundance of inexpensive glycerol, which can be converted into higher value products such as propylene glycol.

=Design Basis=

==Market Analysis==

The overabundance of glycerol caused by the growing biodiesel market has driven prices for glycerol to about $200/ton (Alibaba.com; Bozell and Petersen, 2010). As shown in Figure 1, the supply of glycerol will continue to outpace the demand in 2014 at a growth rate of 2.5% per annum (Oleoline.com).

[[File:Glycerol.png]]

''Figure 1. Global glycerine production in various industrial sectors.''

The production grades of glycerol are crude, technical grade, and USP (United States Pharmaceutical) grade. Crude glycerol comes from production of biodiesel and contains 40-88% glycerol with significant amounts of salt, water, soaps, and methanol. Technical grade glycerol is a refined product with a minimum 98% glycerol content and no salt, soaps, methanol, or other contaminants. USP grade glycerol is a pharmaceutical grade for use in the food, pharmaceutical, and cosmetics industries (Srsbiodiesel.com).

Commercial sources of glycerol other than biodiesel production include fatty acids, fatty alcohols and from the soap industry via the saponification process (Bozell and Petersen, 2010). Glycerol is recognized as safe for animals and humans and environmentally benign, with no significant environmental regulations.

Propylene glycol is conventionally produced using propylene oxide. It is, therefore, sensitive to the price and availability of petroleum and associated products (Davyprotech.com). For this reason, propylene glycol is relatively expensive at around $2500/ton (Interview with Dow Chemical). Supply of propylene glycol struggles to keep up with an increasing annual global demand currently at 1.8m tons (Prweb.com). The ability to isolate propylene glycol production from petroleum by using inexpensive glycerol as a feedstock would be hugely advantageous.

Propylene glycol is used in several applications, including the food, pharmaceutical, and cosmetics industries, as well as in liquid detergents, functional fluids, and unsaturated polyesters (Nizamoff). The two grades of propylene glycol are industrial (99.5% purity) and USP/EP (99.8% purity) (Oleoline.com). Like glycerol, propylene glycol is recognized as safe for animals and humans. Because propylene glycol is biodegradable, it is not considered harmful to the environment and, thus, there are no significant environmental regulations.

==Process Technology==
Several different processes have been proposed for the conversion of glycerol to propylene glycol. These include UOP (Bricker and Leonard, 2012), Davy Process Technology (Tuck, 2012), GTC Technology (Ding et al., 2013), the Lanzhou Institute process (Cui et al., 2009), the Petroleo Brasileiro (Rabello et al., 2011) process, and ADM (Bloom, 2011). These methods all employ catalytic hydrogenolysis and proceed using the same general pathway, show in Figure 2.

[[File:BFD.PNG]]

''Figure 2.'' Block Flow Diagram of process alternatives

====Pre-Treatment====

: The production of propylene glycol from glycerol requires technical grade glycerol, which means a crude glycerol feed must undergo pre-treatment before entering the reactor. For different grades of glycerol the specific process will change, but it will generally be necessary for feeds to be purified, mixed, and heated before high purity glycerol is sent to the synthesis stage. In the GTC process, glycerol, hydrogen and methanol are mixed and heated to anywhere from 150 °C to 240 °C, at pressures between 20 and 80 atm. The preferred composition of the mixture assumes an already pure glycerol feed to be mixed, so any glycerol purchased at lower purities must be distilled to purity before entering the mixer and heater. The Lanzhou and Petroleo Brasileiro processes describe vacuum filtration and distillation of crude glycerol to remove impurities such as sodium, chloride, sulfur and phosphorous salts, fatty acids, phospholipids, glycerides, soaps and biodiesel residues. Any of these impurities can kill the catalyst used downstream. The treated glycerol purity is between 90 – 100%.

====Synthesis====

:In all process technologies considered, the basis of the synthesis is hydrogenolysis of glycerol via packed bed reactors with some form of a catalyst, usually copper based. This reaction is shown in Figure 3. In some cases, the process allows for more reactors to be used in series to achieve a higher conversion. Much of the variation in the processes being examined is based on different operating conditions and the desired purity of the product, propylene glycol.

:[[File:Reaction.PNG]]
:''Figure 3.'' Catalytic hydrogenolysis of glycerol to propylene glycol

====Separation====

:A series of separations is used to separate by-products from propylene glycol. Three step distillations are common; some procedures allow for additional steps, which can change the purity of the product. Common byproducts that need to be separated are methanol, acetol, water, and various other minor alcohol solutions.

==Site Conditions and Capacity==

In the United States, the EPA biofuel mandate for 2014 will be reduced from 18.15 billion gallons to 15-15.52 billion gallons (United States Environmental Protection Agency), so the production of biodiesel will decrease, decreasing the supply of crude glycerol in the United States. In South America, Argentina and Brazil are the largest producers of biodiesel, with production in Brazil growing at the fastest rate. It is estimated that 25-30% of Brazilian glycerol production went to drain in 2010 and 2011, indicating a large supply of inexpensive feedstock (Oleoline.com). Building a facility in Salvador da Bahia, Brazil not only enables access to this supply of inexpensive glycerol, but also provides access to a port city and thus allows export of propylene glycol to high demand markets such as China and the U.S. Additional benefits of building in Brazil include the lower corporate tax rate at 34% compared to 40% in the United States (Kpmg.com) and the temperate climate with an almost constant average temperature of 80 °F (Wmo.int). Dow Chemical currently operates a conventional propylene glycol facility near Salvador, indicating a potentially strong market in the area (Dow.com). The capacity selected for this project is 10,000 ton/year. Current plants using comparable technology, such as ADM and Oleon operate at 100,000- and 200,000-tons, respectively (Icis.com, a). The plant capacity is therefore relatively small, which leaves room for increased production.

==Process Model Basis and Assumptions==

===Reactor===

The process is based on the design outlined by UOP (Bricker and Leonard, 2012). The reaction is catalytic hydrogenolysis of glycerol to propylene glycol over a Co/Pd/Re catalyst consisting of 2.5 wt% Co, 0.4 wt% Pd, and 2.4 wt% Re on NORIT ROX 0.8. The catalyst was reduced at 320 °C in the presence of only H2 prior to use in the reactor. The reaction is carried out at 225.6 °C and 5516 kPa with a 1.17 LHSV. The feed enters the reactor at a Hydrogen to glycerol feed ratio of 2.5:1 and at a pH of 12. At these reactor conditions glycerol conversion and selectivities toward propylene glycol and ethylene glycol are 85%, 91%, and 9%, respectively. The upper bound for reactor methanol concentration was set at 7 wt% to maintain catalyst performance according to specifications outlined by UOP (Bricker and Leonard, 2012).

===Feedstocks and Products===

The reactor feed glycerol (including pre-treated and recycled glycerol) is at 23.16 °C and 5516 kPa and has a composition of 37.77 wt% glycerol, 54.42 wt% water, .77 wt% NaOH, 3.36 wt% sodium sulfate, 3.63 wt% methanol, and .04 wt% acetic acid (Bricker and Leonard, 2012). Hydrogen gas is purchased at 187.8 °C and 5516 kPa. Our main product, propylene glycol, can be sold at industrial grade purity of 99.5 wt% or USP grade purity of 99.8 wt% (Dow.com). One of our byproducts, ethylene glycol, can be sold at a variety of grades, including Polyester grade (99.9 wt%) and Industrial grade (99.1 wt%) (Meglobal.biz).

=Process Overview=

The process flow diagram (PFD) can be found in Figure 4. Incoming glycerol is a byproduct of biodiesel production, usually 40 to 85% glycerol, so it contains fatty acids that must be removed before contacting the fixed-bed reactor catalyst. M-101 mixes the incoming feed with sulfuric acid to remove the fatty acids and produce acidulated glycerol. Acidulated glycerol can contain some amount of methanol, sodium, potassium, sulfur, iron, nickel, chloride or trace impurities. The presence of such impurities in small enough amounts will not negatively affect the production of propylene glycol. The best way to ensure the glycerol mixture will be usable is to ensure that methanol content is <1.5% by weight. The acidulated glycerol is then moved to mixer M-102, where it is contacted with 1.77 wt% aqueous sodium hydroxide. This mixer will increase pH to ~12; a basic glycerol solution will have a much higher selectivity towards propylene. The pH corrected glycerol stream is then heated to 148.9 °C and mixed with water and glycerol recycle streams in M-103. The outgoing glycerol mixture is then mixed with compressed hydrogen gas in a 2.5:1 hydrogen to glycerol mole ratio. The hydrogen comes from an external gas feed. The resulting liquid/gas mixture is sent to the fixed-bed reactor R-101.

[[File:PFD_final.png|1100px]]

''Figure 4. Process Flow Diagram for the production of propylene glycol.''

Hydrogenolysis of glycerol to propylene glycol is carried out in R-101 at 187.8 °C and 5516 kPa. Due to the exothermic nature of the reaction, it is necessary to provide a quench gas stream. In this case, the recycled hydrogen comes in at 72.8 °C, which maintains the reactor temperature at 187.8 °C. The catalyst utilized is a Pd/Co/Re on NORIT ROX 0.8, which provides an 85% conversion of glycerol, with a 91% selectivity to propylene glycol at the given operating conditions. The reactor effluent contains propylene glycol, unreacted glycerol and other byproducts and hydrogen gas. The effluent is sent to V-101, a flash evaporator, where the hydrogen gas is removed from the stream and split into two directions: to be sent off as waste and to be recycled. The waste stream is useful to remove any unwanted gasses that may accumulate over repeated reaction cycles. The resulting propylene glycol mixture is then sent to V-102 for separation and purification.

V-102, a fractionation tower, removes water and C2 alcohols from the propylene glycol reactor effluent. The overhead stream, containing 96 wt% water and balance C2 alcohols, is recycled. The bottoms of V-102 contain water-free propylene glycol, which is then sent to V-103, another fractionation tower which will separate the desired product from the unreacted glycerol and other byproducts. The overhead stream contains 92.6 wt% propylene glycol. The bottoms stream contains unreacted glycerol, ethylene glycol, sodium salts and other impurities. This is sent to F-101, a solid/liquid filter that will remove the solid salt impurities for disposal. The resulting purified liquid stream can be recycled to the beginning of the process and mixed with incoming feed in M-103.

The overheads of V-103 are sent to V-104, which will separate propylene glycol from ethylene glycol. The resultant overheads are 99.8 wt% propylene glycol, which is sent to a storage tank. Additionally, the bottoms are 99.9 wt% ethylene glycol, which is also stored in a tank.

=Process Simulation=

The process is modeled in Aspen HYSYS V7.3 using the non-random two-liquid (NRTL) model as the fluid package, the results of which are shown in Figure 5.

[[File:hysys.png|1100px]]

''Figure 5. HYSYS simulation for the production of propylene glycol.''

=Optimization=

Simple distillation columns in HYSYS were used to find initial estimates for tray numbers, reflux ratios, and optimal feed stage location. Once complex columns were simulated, these specifications were further optimized. Liquid returned to columns via reflux is cooler than up-flowing vapors. Heat transfer between the two components improves the efficacy of the distillation tower, reducing the number of trays needed. However, if a column is operated in total reflux, no product will ever be collected. The price of each column, utilities costs, product yields were optimized by testing several combinations of reflux ratios and tray numbers. The temperature of the inlet stream and component fractions should be similar to the tray the feed enters on. This knowledge was used to optimize the feed tray numbers for each distillation column, decreasing the number of trays needed, the cost of utilities, and increasing the product purity.

Reactor Cost was optimized using Solver in Microsoft Excel 2010. The cost accounted for the pressure drop across the reactor (Ergun equation), minimum volume necessary to meet target LHSV, and design specifications for pressure vessels including wall thickness and diameter, and minimum heat transfer specifications such as area, jacket spacing, jacket type, and heat transfer fluid type. Also, several materials were evaluated, including SS304 and SS407, to find the lowest overall cost.

=Waste Streams=

The water purge is a dilute aqueous waste stream and will be treated in a wastewater facility at a cost of $1.5/t. The hydrogen and glycerol purge can be used as heating fuels due to their high heating values. This will offset waste treatment costs as well as fuel costs. If the price of heating fuel is taken to be $4.50/GJ (Interview with Dave Wegerer), this results in savings of $638.10/t H2 and $68/t Glycerol purge. The solid waste, Na2SO4, can be sold at around $100/t (Kostick).

=Equipment Costs=
Figure 6 below shows the approximated costs of each of the pieces of equipment calculated using Aspen Economic Evaluator v7.3.1. The major components running through the equipment are not corrosive, except basic water. In addition most of the vessels are under fairly standard temperatures and pressures. The key exception is the jacketed reactor, which is subject to extreme conditions. The selection of SS407 allowed for a cheaper reactor as compared to SS304 due to the higher tensile strength. The total ISBL equipment cost is 4.8 $MM in 2010 Gulf Coast USD. The NF cost index is 2250 in 2010 and will conservatively be 2050 in 2014 (Towler and Sinnott, 2013), which adjusts project cost to 5.33 $MM in 2014 Gulf Coast USD. The 2003 location factor for Brazil is 1.14 (Towler and Sinnott, 2013), and the exchange rate in 2003 was 1 Real = $.3402 (Oanda.com). The average rate for the past 3 months has been 1 Real = $.427 (Bloomberg.com, a). The adjusted capital cost for Brazil in 2014 is therefore 7.63 $MM. Since the project is large-volume chemical on a new site, OSBL is taken as 40% of ISBL, or 3.05 $MM. Engineering and contingency costs are taken as 10 and 15%, respectively, of combined ISBL and OSBL costs.

[[File:EquipCosts.PNG]]

''Figure 6.'' Equipment Cost Breakdown

=Prices=

The price of feedstocks crude glycerol and hydrogen are $200/t (Alibaba.com; Bozell and Petersen, 2010) and $1100/t (Icis.com, b). The price of products propylene glycol and ethylene glycol are $2557/t (Interview with Dow Chemical) and $1400/t (Meglobal.biz). The price of consumables NaOH and H2SO4 are $635/t (Icis.com, c) and $80/t (Icis.com, d). The catalyst must be replaced every 2 years, at a cost of 5.13 $MM (Basf.com; Lme.com; Sigmaaldrich.com). The price of electricity has been fluctuating recently due to lack of rainfall, and is taken as 0.202 $/kWh (Bloomberg.com, b). Utilities prices for high pressure steam, medium pressure steam, and cooling water are $14.3/t, $12/t, and $.024/t, respectively (Towler and Sinnott, 2013).

=Fixed Operating Costs=

Based on the plant size, three shift positions with 4.8 operators per shift will comprise the operating labor. A salary of $35,000 is a reasonable estimate of operator wages in Brazil. Supervision is taken as 25% of operating labor, and direct overhead is 45% of labor and supervision. Maintenance is taken as 3% of ISBL Cost, and plant overhead is 65% of labor and maintenance costs. Property and local tax and insurance are both typically 1% of ISBL plus OSBL Cost. Repayment of debt associated with fixed investment is accounted for in the weighted average cost of capital so 0% is taken as fixed cost of production. However, working capital will be funded entirely by debt, so 5% interest of working capital is taken as interest on debt financing.

The plant is scheduled to be constructed over two years, with 40% of capital expenditure being accounted for in year 1. The plan will operate at 70% capacity in year 3 and 100% in the subsequent years. Cost of equity is taken to be 30% based on chemical industry companies (Towler and Sinnott, 2013), adjusting for increased risk in South American ventures. The debt ratio is taken to be 0.4 which allows this project to be financed by corporate bonds that are rated A and above, with a debt cost of capital of 5%. The resulting weighted average cost of capital is therefore 20%. The project will be depreciated using MACRS 10 year depreciation (Icis.com, e) which allows larger tax savings in the near-term, resulting in higher project NPV. The corporate tax rate in Brazil is 34% (Kpmg.com). Working capital is calculated as seven weeks Cash Cost of Production (CCOP) minus two weeks feed plus 1% of Fixed Capital Cost (Towler and Sinnott, 2013).

=Utilities and Pinch Analysis=

The total cost of utilities was found using the energy outputs from HYSYS and known costs of natural gas, water, and electricity in Brazil from commodity indices and surveys from the Brazilian government. The results are presented visually in Figure 7 below. The total utility bill comes to $2,424,000 per year. $1,110,000 from heating gas required to create steam for heating in the process, $1,304,000 in water for both steam generation and cooling water, and approximately $10,000 for electricity to power the pumps and any local offices or break rooms. One important note to consider is that the price of gas in Brazil has risen 40% in the past three months. Continuing fluctuations in energy prices could greatly affect these estimates from year to year.

In order to determine the annual cost of utilities, it was necessary to carry out some heat exchanger design calculations and estimations. After surveying the energy requirement of each exchanger, it was determined that cooling water and steam will be the simplest heat transfer fluids to use, due to the relatively small heat requirements and change in temperature of each process stream. In the case of the three reboilers and three condensers, which are designed with the distillation columns, it was only necessary to find a mass flow rate of steam and water respectively. For the cooling water, once the mass flow rate was calculated, this was sufficient to price. For steam, in addition to purchasing the required mass of water, it was necessary to determine the heat required to raise the steam to the required temperatures. For the one cooler and one heater, we also utilized water and steam, and more thorough design was developed in order to accurately price the two exchangers and to help make a pinch analysis viable.

[[File:Fig4.PNG]]

''Figure 7.'' Utilities Breakdown

=Economic Analysis=

Gross profits are 8.1 $MM from year 4 onward and the project has a simple payback period of 2.6 years. The project Net Present Value (NPV) for 10 and 15 years is 4.1 $MM and 6.8 $MM. The expected return on this project (10 year IRR) is 30.3%, indicating this project is highly profitable and can be scaled up for higher NPV. Accelerating the project schedule to complete the plant in less than 2 years will also greatly increase the NPV.

=Sensitivity Analysis=

A sensitivity analaysis was carried out for a variety of process parameters. For catalyst, PG, HP and MP Steam prices, best- and worst-case were taken as +/- 10% of the base price. The project NPV is most sensitive to the price of Propylene Glycol and Glycerol, which is expected as these are the main product and feedstock. The NPV is also highly sensitive to the cost of capital. The results are presented below, in Figure 8.

[[File:Fig5.PNG]]

''Figure 8.'' Sensitivity Analysis

=Conclusion=

Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years, although there are some existing environmental and safety concerns. Our current plans involve burning an effluent stream in which the key components are hydrogen, ethylene glycol and some fatty acids. In this case an analysis will need to be done in order to determine the extent of the damage to the local air and if a purification step is necessary. The main safety concerns involve the acid streams and the reactor itself. Operators will needs to be thoroughly educated on acid burn precaution and treatment procedures due to the acidic requirements of the streams. The reactor runs at very high pressures and given the exothermic nature of the reaction appropriate steps will need to be taken in order to ensure that runaway reactions can be safely dealt with and pressure relief systems will be put in place. Our economic analysis has proven that the project as it currently stands is highly profitable and will bring in positive cash flow within three years. However, there is definite room for expansion in the design; our low NPV values and high IRR values indicate the ability to leverage economies of scale and dramatically expand our profit margins. As it stands, we recommend maximizing the NPV of the project with full scale optimization. This entails the addition of parallel reaction trains and the inclusion of a heat exchange network to fully maximize our profit margins. A plant layout should be developed along with the inclusion of automated control schemes to better optimize the process operation. The project currently holds great economic potential and with some more detailed engineering, could provide a very high return for our shareholders.

=Works Cited=

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