Site condition and design

Title: Site condition and design

Authors: Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman

Stewards: Alex Chandel, Eric Jiang, Minwook Kim, Todor Kukushliev, William Lassman

Date Revised: 1/17/2014

Introduction

All chemical processes require land for chemical storage, process equipment, and labor facilities.

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

Proximity to continental and underwater oil deposits, natural gas, coal mines, and other resources.

Weather

Its influence on ambient temperature and thus on utility cost.^{[ citation needed ]} Also rain and humidity, and the sensitivity of the process to water exposure.

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

Some states are more friendly to chemical engineering operations, or may impose additional regulations. Property costs, property taxes, corporate income taxes, and environmental contamination fines will vary between states.

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:

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:

• 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.

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Cost

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

$TC=rK+wL$

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.

Common locations

There are many common locations for chemical processes, often specific to one or more industries.

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:

• 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:

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.

(All this came from Mecklenburgh, J. C. (Ed.). (1985). Process plant layout. Godwin/Longmans.)

Site Construction

(Mecklenburgh, J. C. (Ed.). (1985). Process plant layout. Godwin/Longmans for this section). Site construction, along with process design, is an iterative process that follows a multi-step procedure.

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 (Timmerhaus 2003, PAGE 246).

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, J. C. (Ed.). (1985). Process plant layout. Godwin/Longmans.)

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 page 510-511)

References

• Gavin Towler and Ray Sinnott, Chapter 11 - General Site Considerations, Chemical Engineering Design, 2nd Ed., edited by Gavin Towler and Ray Sinnott, Butterworth-Heinemann, Boston, 2013, Pages 505-524, ISBN 9780080966595, http://dx.doi.org/10.1016/B978-0-08-096659-5.00011-0.

(http://www.sciencedirect.com/science/article/pii/B9780080966595000110)

• M.S. Peters, K.D. Timmerhaus, Plant Design and Economics for Chemical Engineers, 5th Ed., McGraw-Hill: New York, 2003.

• J.C. Mecklenburgh, Plant Design and Economics for Chemical Engineers, Halsted Press: New York, 1985.

External links

• (Relevant wikipedia article)