1. What is plant design?
Chemical engineering design of new chemical plants and the expansion or revision of existing ones require the use of engineering principles and theories combined with a practical realization of the limits imposed by industrial conditions. A successful chemical engineer needs more than a knowledge and understanding of the fundamental sciences and the related engineering subjects such as thermodynamics, reaction kinetics, and computer technology. The engineer must also have the ability to apply this knowledge to practical situations for the purpose of accomplishing something that will be beneficial to society. The course title includes three definitions namely:

2. Definition of design
1. Design: design is a creative activity and is defined as the synthesis, the putting together of ideas to achieve a desired purpose. Also it can be defined as the creation of manufacturing process to fulfill a particular need. The need may be public need or commercial opportunity.
2. Process Design: Process design establishes the sequence of chemical and physical
operations; operating conditions; the duties, major specifications, and materials of construction (where critical) of all process equipment (as distinguished from utilities and building auxiliaries); the general arrangement of equipment needed to ensure proper functioning of the plant; line sizes; and principal instrumentation. The process design is summarized by a process flowsheet.

3. Process Design Steps
1. Flowsheet development. 2. Process material and heat balances. 3. Auxiliary services material and heat balances (utilities requirements). 4. Chemical engineering performance design for specific items of equipments required for a flowsheet. 5. Instrumentation as related to process performance. 6. Preparation of specifications (specification sheets) in proper form for use by the project team as well as for the purchasing function. 7. Evaluation of bids and recommendation of qualified vendor.

4. 3. Plant Design: includes items related directly to the complete plant, such as plant layout, general service facilities, and plant location.

5. Design Development Stages
Figure (2.1), The design process

6. The Design Objectives (The Need) Chemical engineering projects can be divided into three types: A. New process development. B. New production capacity to meet growing sales. C. Modification and addition to existing plant. In the design of a chemical process the need is the public need for the product, the commercial opportunity as foreseen by the sales and marketing organization. Setting the Design Basis (Data Collection) The most important step in starting a process design is translating the customer need into a design basis. The design basis is a more precise statement of the problem that is to be solved. It will normally include the production rate and purity specifications of the main product, together with information on constraints that will influence the design, such as:

7. 1. Information on possible processes and the system of units to be used. 2. The national, local or company design codes that must be followed. 3. Details of raw materials that are available. 4. Information on potential sites where the plant might be located, including climate data, seismic conditions, and infrastructure availability. 5. Information on the conditions, availability, and price of utility services such as fuel (gas), steam, cooling water, process air, process water, and electricity, that will be needed to run the process.

8. Generation of Possible Design Concepts (Solutions) It is the creative part of the design process. This part is concerned with the generation of possible solutions for analysis, evaluation, and selection (ways of meeting objective problems). Source of solutions: a- Past experiences. b- Tried and tested methods.

9. Build Performance Model and Fitness Testi When design alternatives are suggested, they must be tested for fitness of purpose. In other words, the design engineer must determine how well each design concept meets the identified need. In the field of chemical engineering, it is usually prohibitively expensive to build several designs to find out which one works best (a practice known as “prototyping” which is common in other engineering disciplines). Instead, the design engineer builds a mathematical model of the process, usually in the form of computer simulations of the process, reactors, and other key equipment. In some cases, the performance model may include a pilot plant or other facility for predicting plant performance and collecting the necessary design data.

10. The design engineer must assemble all of the information needed to model the process so as to predict its performance against the identified objectives. For process design this will include information on possible processes, equipment performance, and physical property data. If the necessary design data or models do not exist, then research and development work is needed to collect the data and build new models. Once the data has been collected and a working model of the process has been established, then the design engineer can begin to determine equipment sizes and costs. At this stage it will become obvious that some designs are uneconomical and they can be rejected without further analysis. From this step a few candidate designs that meet the customer objective are identified.

11. Economic Evaluation, Optimization, and Selection Once the designer has identified a few candidate designs that meet the customer objective, then the process of design selection can begin. The primary criterion for design selection is usually economic performance, although factors such as safety and environmental impact may also play a strong role. The economic evaluation usually entails analyzing the capital and operating costs of the process to determine the return on investment.

12. The economic analysis of the product or process can also be used to optimize the design. Every design will have several possible variants that make economic sense under certain conditions. For example, the extent of process heat recovery is a tradeoff between the cost of energy and the cost of heat exchangers (usually expressed as a cost of heat exchange area). In regions where energy costs are high, designs that use a lot of heat exchange surface to maximize recovery of waste heat for reuse in the process will be attractive. In regions where energy costs are low, it may be more economical to burn more fuel and reduce the capital cost of the plant.

13. When all of the candidate designs have been optimized, the best design can be selected. Very often, the design engineer will find that several designs have very close economic performance, in which case the safest design or that which has the best commercial track record will be chosen. At the selection stage an experienced engineer will also look carefully at the candidate designs to make sure that they are safe, operable, and reliable, and to ensure that no significant costs have been overlooked.

14. Detailed Design and Equipment Selection Here the detailed specifications of equipment such as vessels, exchangers, pumps, and instruments are determined. During the detailed design stage there may still be some changes to the design, and there will certainly be ongoing optimization as a better idea of the project cost structure is developed. The detailed design decisions tend to focus mainly on equipment selection though, rather than on changes to the flowsheet. For example, the design engineer may need to decide whether to use a Utube or a floating-head exchanger, or whether to use trays or packing for a distillation column.

15. Procurement, Construction, and Operation When the details of the design have been finalized, the equipment can be purchased and the plant can be built. Procurement and construction are usually carried out by an EPC firm (Engineering, Procurement, and Construction) unless the project is very small. Because they work on many different projects each year, the EPC firms are able to place bulk orders for items such as piping, wire, valves, etc., and can use their purchasing power to get discounts on most equipment. The EPC companies also have a great deal of experience in field construction, inspection, testing, and equipment installation. They can therefore normally contract to build a plant for a client cheaper (and usually also quicker) than the client could build it on its own. Finally, once the plant is built and readied for startup, it can begin operation. The design engineer will often then be called upon to help resolve any startup issues and teething problems with the new plant.

16. Flowsheeting (special language conveying information)
Process design normally starts with a process scheme (flowsheet). The flowsheet is the key document or road map in process design. It's a diagrammatic model of the process describe the process steps in a proper sequence using symbols to represent the various components (equipment, lines, and control instrumentation) that make up the unit.

17. The Flowsheet Importance
Shows the arrangement of the equipment selected to carry out the process.
Shows the streams concentrations, flow rates & compositions.
Shows the operating conditions.
During plant start up and subsequent operation, the flow sheet from a basis for comparison of operating performance with design. It's also used by operating personnel for the preparation of operating manual and operator training.

18. Flowsheet Presentation
1- Block diagram
Represent the process in a simplified form.
No details involved.
Don’t describe how a given step will be achieved.
When is it used?
In survey studies.
Process proposal for packaged steps.
Talk out a processing idea.

19. Figure (2.2), Block diagram

20. 2- Pictorial Flow Sheet The equipments are normally drawn in a stylized pictorial form. For tender documents or company brochures actual scale drawing of the equipment are sometimes used. Types of pictorial flowsheets a) Process Flow Diagram (PFD) A PFD is a simplified flow diagram of a single process unit, a utility unit, a complete process module. The purpose of a PFD is to provide a preliminary understanding of the process system indicating only the main items of equipment, the main pipelines and the essential instruments, switches and control valves.

21. A PFD also indicates operating variables, such as mass flow, temperatures and pressures, which are tabulated at various points in the system.
The PFD is a document containing information on:
Process conditions and physical data of the main process streams.
Main process equipment with design data.
Main Process lines.
Mass (material) balance.
Heat balance (if applicable).
NOTE: If the PFD doesn’t contain any data about the flow rates, it is called a qualitative flowsheet, while if the flow rates are involved the PFD is called a combined flowsheet in which qualitative information and quantitative data are combined on the basis of one flowsheet.

22. b) Piping and Instrumentation Diagram (P & ID) (mechanical flow diagram)
A P&ID diagram shows the arrangement of the process equipment, piping, pumps, instruments, valves and other fittings. It should include:
All process equipment identified by an equipment number.
All pipes identified by a line size, material code and line number.
All valves with an identified size and number.
Fittings.
All pumps identified by a suitable code number.
All control loops and instruments.

23. c) Utility Flowsheet (Process Engineering Utility Flow Diagram (PEUFD)) Used to summarize and detail the interrelationship of utilities such as air, water (various types), steam (various types), heat transfer mediums, process vents and purges, safety relief blow-down, etc., to the basic process. The amount of detail is often too great to combine on other sheets, so separate sheets are prepared. The PEUFD is a document containing information on: Main distribution or arrangement of each individual utility system, expect electrical systems.

24. PEUFD Function: The PEUFD shall state characteristics and consumption figures of the particular utility concerned, cooling water, fire water, drinking water, steam, plant air, instrument air, fuel oil/gas, inert gas and similar utilities. d) Process Safeguarding Flow Diagram (PSFD) The PSFD is a document highlighting information on: Types and levels of protection offered by the devices installed and their inter relation to demonstrate the plant’s safety.

25. The P&ID contains all information required for a PSFD; however, the PSFD highlights protection in case of extreme conditions and measures to be taken to safeguard personnel and environment. Note: In general these schemes will only be made for complex installations like offshore process platforms. For simple applications the information shown on the P&ID is usually sufficient to highlight safety devices and aspects.

26. What is meant by the following identifications? PFD, P&ID, PEUFD and
PSFD State the information you can get from the following schemes: PFD, P&ID, PEUFD and PSFD?

27. Figure (2.3), PFD [Qualitative flow diagram for the manufacture of nitric acid by the
ammonia-oxidation process]

28. ammonia-oxidation process]
Figure (2.4), PFD [Combined flow diagram for the manufacture of nitric acid by the
ammonia-oxidation process]

29. Figure (2.5), Process and Instrument Diagram (P&ID)

30. Figure (2.6), Typical utility flow diagram

31. Figure (2.7), Engineering P&I flowsheet of the reaction section of plant for dealkylation of benzene

32. Flowsheet Symbols To reduce detailed written descriptions on flowsheets, it is usual practice to develop or adopt a set of symbols and codes which suit the purpose. Many symbols are pictorial which is helpful in representing process as well as control and mechanical operations. See Fig. (2.8). Line Symbols and Designation The two types of lines on a flowsheet are (1) those representing outlines and details of equipment, instruments, etc., and (2) those representing pipe carrying process or utility liquids, solids, or vapors and electrical or instrument connections. The latter must be distinguished among themselves as suggested by Fig. (2.9).

33. The usual complete line designation contains the following: (1) line size (nominal); (2) material cod; (3) sequence number; and (4) materials of construction. Examples: 2"-CL6-CS40 3"-CL6a-CS40 Equipment Designation Equipment code designations can be developed to suit the particular process, or as is customary a master coding can be established and followed for all projects. A suggested designation list (not all inclusive for all processes) for the usual process plant equipment is given in Table (2.1). The various items are usually numbered by type and in process flow order as set forth on the flowsheets. For example:

34. Item code Designation
S-1 First separator in a processs
S-2 Second separator in a process
C-1 First compressor in a process

36. Figure (2.8.a), Flowsheet symbols.

38. Figure (2.9), Line symbols.

39. Types of Designs The methods for carrying out a design project may be divided into the following classifications, depending on the accuracy and detail required: Preliminary or quick-estimate designs Used as a basis for determining whether further work should be done on the proposed process. This type of design is based on approximate process methods, and rough cost estimates are prepared. Few details are included, and the time spent on calculations is kept at a minimum.

40. Detailed-estimate designs
In this type of design, the cost and profit potential of an established process is determined by detailed analysis and calculations. However, exact specifications are not given for the equipment, and drafting-room work is minimized. The following factors should be established within narrow limits before a detailed-estimate design is developed:
Manufacturing process
Material and energy balances
Temperature and pressure ranges

41. Raw-material and product specifications
Yields, reaction rates, and time cycles
Materials of construction
Utilities requirements
Plant site
i.e. the above factors should be determined after a preliminary design.

42. Before proceeding any further with the development of a process design and its associated economics, it will be desirable to consider an overall view of the various functions involved in a complete plant design. Particular emphasis in this discussion will be placed on important health, safety, loss prevention, and environmental considerations. Other items that will be noted briefly include plant location, plant layout, plant operation and control, utilities, structural design, storage, materials handling, patents, and legal restrictions.

43. I. Plant Location The geographical location of the final plant can have strong influence on the success of an industrial venture. Considerable care must be exercised in selecting the plant site, and many different factors must be considered. Primarily, the plant should be located where the minimum cost of production and distribution can be obtained, but other factors, such as room for expansion and safe living conditions for plant operation as well as the surrounding community, are also important.

44. A general consensus as to the plant location should be obtained before a design project reaches the detailed estimate stage, and a firm location should be established upon completion of the detailed-estimate design. The choice of the final site should first be based on a complete survey of the advantages and disadvantages of various geographical areas and, ultimately, on the advantages and disadvantages of available real estate. The following factors should be considered in selecting a plant site:

45. 1. Raw materials availability 2. Markets 3. Energy availability 4
1. Raw materials availability 2. Markets 3. Energy availability 4. Climate 5. Transportation facilities 6. Water supply 7. Waste disposal 8. Labor supply 9. Taxation and legal restrictions 10. Site characteristics 11. Flood and fire protection 12. Community factors

46. The factors that must be evaluated in a plant-location study indicate the need for a vast amount of information, both quantitative (statistical) and qualitative. Fortunately, a large number of agencies, public and private, publish useful information of this type greatly reducing the actual original gathering of the data. Raw materials availability: The source of raw materials is one of the most important factors influencing the selection of a plant site. This is particularly true if large volumes of raw materials are consumed, because location near the raw materials source permits considerable reduction in transportation and storage charges. Attention should be given to the purchased price of the raw materials, distance from the source of supply, freight or transportation expenses, availability and reliability of supply, purity of the raw materials, and storage requirements.

47. Markets: The location of markets or intermediate distribution centers affects the cost of product distribution and the time required for shipping. Proximity to the major markets is an important consideration in the selection of a plant site, because the buyer usually finds it advantageous to purchase from nearby sources. It should be noted that markets are needed for by-products as well as for major final products. Energy availability: Power and steam requirements are high in most industrial plants, and fuel is ordinarily required to supply these utilities. Consequently, power and fuel can be combined as one major factor in the choice of a plant site. Electrolytic processes require a cheap source of electricity, and plants using electrolytic processes are often located near large hydroelectric installations. If the plant requires large quantities of coal or oil, location near a source of fuel supply may be essential for economic operation. The local cost of power can help determine whether power should be purchased or self-generated.

48. Climate: If the plant is located in a cold climate, costs may be increased by the necessity for construction of protective shelters around the process equipment, and special cooling towers or air-conditioning equipment may be required if the prevailing temperatures are high. Excessive humidity or extremes of hot or cold weather can have a serious effect on the economic operation of a plant, and these factors should be examined when selecting a plant site.

49. Transportation facilities: Water, railroads, and highways are the common means of transportation used by major industrial concerns. The kind and amount of products and raw materials determine the most suitable type of transportation facilities. In any case, careful attention should be given to local freight rates and existing railroad lines. The proximity to railroad centers and the possibility of canal, river, lake, or ocean transport must be considered: Motor trucking facilities are widely used and can serve as a useful supplement to rail and water facilities. If possible, the plant site should have access to all three types of transportation, and, certainly, at least two types should be available. There is usually need for convenient air and rail transportation facilities between the plant and the main company headquarters, and effective transportation facilities for the plant personnel are necessary.

50. Water supply: The process industries use large quantities of water for cooling, washing, steam generation, and as a raw material. The plant, therefore, must be located where a dependable supply of water is available. A large river or lake is preferable, although deep wells or artesian wells may be satisfactory if the amount of water required is not too great. The level of the existing water table can be checked by consulting the state geological survey, and information on the constancy of the water table and the year-round capacity of local rivers or lakes should be obtained. If the water supply shows seasonal fluctuations, it may be desirable to construct a reservoir or to drill several standby wells. The temperature, mineral content, silt or sand content, bacteriological content, and cost for supply and purification treatment must also be considered when choosing a water supply.

51. Waste disposal: In recent years, many legal restrictions have been placed on the methods for disposing of waste materials from the process industries. The site selected for a plant should have adequate capacity and facilities for correct waste disposal. Even though a given area has minimal restrictions on pollution, it should not be assumed that this condition will continue to exist. In choosing a plant site, the permissible tolerance levels for various methods of waste disposal should be considered carefully, and attention should be given to potential requirements for additional waste-treatment facilities.

52. Labor supply: The type and supply of labor available in the vicinity of a proposed plant site must be examined. Consideration should be given to prevailing pay scales, restrictions on number of hours worked per week, competing industries that can cause dissatisfaction or high turnover rates among the workers, and variations in the skill and productivity of the workers.

53. Taxation and legal restrictions: State and local tax rates on property income, unemployment insurance and similar items vary from one location to another. Similarly, local regulations on zoning, building codes, nuisance aspects, and transportation facilities can have a major influence on the final choice of a plant site. In fact, zoning difficulties and obtaining the many required permits can often be much more important in terms of cost and time delays than many of the factors discussed in the preceding sections.

54. Site characteristics: The characteristics of the land at a proposed plant site should be examined carefully. The topography of the tract of land and' the soil structure must be considered, since either or both may have a pronounced effect on construction costs. The cost of the land is important, as well as local building costs and living conditions. Future changes may make it desirable or necessary to expand the plant facilities. Therefore, even though no immediate expansion is planned, a new plant should be constructed at a location where additional space is available.

55. Flood and fire protection: Many industrial plants are located along rivers or near large bodies of water, and there are risks of flood or hurricane damage. Before selecting a plant site, the regional history of natural events of this type should be examined and the consequences of such occurrences considered. Protection from losses by fire is another important factor in selecting a plant location. In case of a major fire, assistance from outside fire departments should be available. Fire hazards in the immediate area surrounding the plant site must not be overlooked.

56. Community factors: The character and facilities of a community can have quite an effect on the location of the plant. If a certain minimum number of facilities for satisfactory living of plant personnel do not exist, it often becomes a burden for the plant to subsidize such facilities. Cultural facilities of the community are important to sound growth. Churches, libraries, schools, civic theaters, concert associations, and other similar groups, if active and dynamic, do much to make a community progressive. The problem of recreation deserves special consideration. The efficiency, character, and history of both state and local government should be evaluated. The existence of low taxes is not in itself a favorable situation unless the community is already well developed and relatively free of debt.

57. Selection of the Plant Site The major factors in the selection of most plant sites are (1) raw materials, (2) markets, (3) energy supply, (4) climate, (5) transportation facilities, and (6) water supply. For a preliminary survey, the first four factors should be considered. Thus, on the basis of raw materials, markets, energy supply, and climate, acceptable locations can usually be reduced to one or two general geographical regions. For example, a preliminary survey might indicate that the best location for a particular plant would be in the south-central or south-eastern part of the United States.

58. In the next step, the effects of transportation facilities and water supply are taken into account. This permits reduction of the possible plant location to several general target areas. These areas can then be reduced further by considering all the factors that have an influence on plant location. As a final step, a detailed analysis of the remaining sites can be made. Exact data on items such as freight rates, labor conditions, tax rates, price of land, and general local conditions can be obtained. The various sites can be inspected and appraised on the basis of all the factors influencing the final decision. Many times, the advantages of locating a new plant on land or near other facilities already owned by the concern that is building the new plant outweigh the disadvantages of the particular location. In any case, however, the final decision on selecting the plant site should take into consideration all the factors that can affect the ultimate success of the overall operation.

59. II. Plant Layout After the process flow diagrams are completed and before detailed piping, structural, and electrical design can begin, the layout of process units in a plant and the equipment within these process units must be planned. This layout can play an important part in determining construction and manufacturing costs, and thus must be planned carefully with attention being given to future problems that may arise. Since each plant differs in many ways and no two plant sites are exactly alike, there is no one ideal plant layout. However, proper layout in each case will include arrangement of processing areas, storage areas, and handling areas in efficient coordination and with regard to such factors as:

60. 1. New site development or addition to previously developed site
2. Type and quantity of products to be produced
3. Type of process and product control
4. Operational convenience and accessibility
5. Economic distribution of utilities and services
6. Type of buildings and building-code requirements
7. Health and safety considerations
8. Waste-disposal requirements
9. Auxiliary equipment
10. Space available and space required
11. Roads and railroads
12. Possible future expansion

61. Preparation of the Layout
Scale drawings, complete with elevation indications can be used for determining the best location for equipment and facilities. Elementary layouts are developed first. These show the fundamental relationships between storage space and operating equipment. The next step requires consideration of the safe operational sequence and gives a primary layout based on the flow of materials, unit operations, storage, and future expansion.

62. By analyzing all the factors that are involved in plant layout, a detailed recommendation can be presented, and drawings and elevations, including isometric drawings of the piping systems, can be prepared. Templates, or small cutouts constructed to a selected scale, are useful for making rapid and accurate layouts, and three-dimensional models are often made. The use of such models for making certain a proposed plant layout is correct has found increasing favor in recent years.

63. III. Storage Adequate storage facilities for raw materials, intermediate products, final products, recycle materials, off-grade materials, and fuels are essential to the operation of a process plant. A supply of raw materials permits operation of the process plant regardless of temporary procurement or delivery difficulties. Storage of intermediate products may be necessary during plant shutdown for emergency repairs while storage of final products makes it possible to supply the customer even during a plant difficulty or unforeseen shutdown. An additional need for adequate storage is often encountered when it is necessary to meet seasonal demands from steady production.

64. Bulk storage of liquids is generally handled by closed spherical or cylindrical tanks to prevent the escape of volatiles and minimize contamination. Since safety is an important consideration in storage-tank design, the American Petroleum Institute? and the National Fire Protection Association publish rules for safe design and operation. Floating roof tanks are used to conserve valuable products with vapor pressures which are below atmospheric pressure at the storage temperature. Liquids with vapor pressures above atmospheric must be stored in vapor-tight tanks capable of withstanding internal pressure. If flammable liquids are stored in vented tanks, flame arresters must be installed in all openings except connections made below the liquid level.

65. Gases are stored at atmospheric pressure in wet- or dry-seal gas holders. The wet-gas holder maintains a liquid seal of water or oil between the top movable inside tank and the stationary outside tank. In the dry-seal holder the seal between the two tanks is made by means of a flexible rubber or plastic curtain. Recent developments in bulk natural gas or gas-product storage show that pumping the gas into underground strata is the cheapest method available.

66. High-pressure gas is stored in spherical or horizontal cylindrical pressure vessels. Solid products and raw materials are either stored in weather-tight tanks with sloping floors or in outdoor bins and mounds. Solid products are often packed directly in bags, sacks, or drums.

67. IV. Materials Handling Materials-handling equipment is logically divided into continuous and batch types, and into classes for the handling of liquids, solids, and gases. Liquids and gases are handled by means of pumps and blowers; in pipes, flumes, and ducts; and in containers such as drums, cylinders, and tank cars. Solids may be handled by conveyors, bucket elevators, chutes, lift trucks, and pneumatic systems. The selection of materials-handling equipment depends upon the cost and the work to be done. Factors that must be considered in selecting such equipment include: 1. Chemical and physical nature of material being handled 2. Type and distance of movement of material 3. Quantity of material moved per unit time 4. Nature of feed and discharge from materials-handling equipment 5. Continuous or intermittent nature of materials handling

68. The major movement of liquid and gaseous raw materials and products within a plant to and from the point of shipment is done by pipeline. Many petroleum plants also transport raw materials and products by pipeline. When this is done, local and federal regulations must be strictly followed in the design and specification of the pipeline. Movement of raw materials and products outside of the plant is usually handled either by rail, ship, truck, or air transportation. Some type of receiving or shipping facilities, depending on the nature of the raw materials and products, must be provided in the design of the plant. Information for the preparation of such specifications can usually be obtained from the transportation companies serving thearea.

69. In general, the materials-handling problems in the chemical engineering industries do not differ widely from those in other industries except that the existence of special hazards, including corrosion, fire, heat damage, explosion, pollution, and toxicity, together with special service requirements, will frequently influence the design. Themost difficult of these hazards often is corrosion. This is generally overcome by the use of a high-first-cost, corrosion-resistant material in the best type of handling equipment or by the use of containers which adequately protect the equipment.

70. Firm process designs or detailed designs
When the detailed-estimate design indicates that the proposed project should be a commercial success, the final step before developing construction plans for the plant is the preparation of a firm process design. In this type complete specifications are presented for all components of the plant, without any change in the process flowsheet and accurate costs based on quoted prices are obtained. The firm process design includes blueprints and sufficient information to permit immediate development of the final plans for constructing the plant.

71. Design Information (literature survey) General information and specific data required to the development of a design project can be obtained from many different sources such as: A. Textbooks A large number of textbooks covering the various aspects of chemical engineering principles and design are available. In addition, many handbooks have been published giving physical properties and other basic data which are very useful to the design engineer. A primary source of information on all aspects of chemical engineering principles, design, costs, and applications is “The Chemical Engineers’ Handbook” published by McGraw-Hill Book Company with R. H. Perry and D. W. Green as editors and Encyclopedia of Chemical Technology by Kirk Othmer.

72. B. Technical journals Regular features on design-related aspects of equipment, costs, materials of construction, and unit processes are published in Chemical Engineering. In addition to this publication, there are many other periodicals that publish articles of direct interest to the design engineer. The following periodicals are suggested as valuable sources of information for the chemical engineer who wishes to keep abreast of the latest developments in the field:

73. American Institute of Chemical Engineers journal (AICHE)
Chemical Engineering Progress
Chemical and Engineering News
Chemical Engineering Science
Industrial and Engineering Chemistry Fundamentals
Industrial and Engineering Chemistry Process Design and Development
Journal of the American Chemical Society, Journal of Physical Chemisty
Journal of the American Chemical Society
Hydrocarbon Processing
Oil and Gas Journal
Engineering News-Record
Canadian Journal of Chemical Engineering

74. C. Trade bulletins Trade bulletins are published regularly by most manufacturing concerns, and these bulletins give much information of direct interest to the chemical engineer preparing a design. Some of the trade-bulletin information is condensed in an excellent reference book on chemical engineering equipment, products, and manufacturers. This book is known as the “Chemical Engineering Catalog”, and contains a large amount of valuable descriptive material. New information is constantly becoming available through publication in periodicals, books, trade bulletins, government reports, university bulletins, and many other sources. Many of the publications are devoted to shortcut methods for estimating physical properties or making design calculations, while others present compilations of essential data in the form of nomographs or tables. The effective design engineer must make every attempt to keep an up-to-date knowledge of the advances in the field.

75. D. Patents A patent is essentially a contract between an inventor and the public. In consideration of full disclosure of the invention to the public, the patentee is given exclusive rights to control the use and practice of the invention. A patent gives the holder the power to prevent others from using or practicing the invention for a period of 17 years from the date of granting. In contrast, trade secrets and certain types of confidential disclosures can receive protection under common-law rights only as long as the secret information is not public knowledge. A new design should be examined to make certain no patent infringements are involved. If the investigation can uncover even one legally expired patent covering the details of the proposed process, the method can be used with no fear of patent difficulties.

76. The Preliminary Design In order to amplify the remarks made earlier concerning the design-project procedure, it is appropriate at this time to look more closely at a specific preliminary design. Only a brief presentation of the design will be attempted at this point. However, sufficient detail will be given to outline the important steps which are necessary to prepare such a preliminary design. The problem presented is a practical one of a type frequently encountered in the chemical industry; it involves both process design and economic considerations.

77. Problem Statement A conservative petroleum company has recently been reorganized and the new management has decided that the company must diversify its operations into the petrochemical field if it wishes to remain competitive. The research division of the company has suggested that a very promising area in the petrochemical field would be in the development and manufacture of biodegradable synthetic detergents using some of the hydrocarbon intermediates presently available in the refinery. A survey by the market division has indicated that the company could hope to attain 2.5 percent of the detergent market if a plant with an annual production of 15 million pounds were to be built. To provide management with an investment comparison, the design group has been instructed to proceed first with a preliminary design and an updated cost estimate for a non biodegradable detergent producing facility similar to ones supplanted by recent biodegradable facilities.

78. Literature Survey A survey of the literature reveals that the majority of the non biodegradable detergents are alkyl benzene sulfonates (ABS). Theoretically, there are over 80,000 isomeric alkyl benzenes in the range of C10 to C15 for the alkyl side chain. Costs, however, generally favor the use of dodecene (propylene tetramer) as the starting material for ABS. There are many different schemes in the manufacture of ABS. Most of the schemes are variations of the one shown in Fig. (11) for the production of sodium dodecylbenzene sulfonate. A brief description of the process is as follows:

79. This process involves: i
This process involves: i. Reaction of dodecene with benzene in the presence of aluminum chloride catalyst (alkylation) ii. Fractionation of the resulting crude mixture to recover the desired boiling range of dodecylbenzene. iii. Sulfonation of the dodecylbenzene. iv. Neutralization of the sulfonic acid with caustic soda. v. Blending the resulting slurry with chemical “builders”; and drying.

80. Process Description Dodecene is charged into a reaction vessel containing benzene and aluminum chloride. The reaction mixture is agitated and cooled to maintain the reaction temperature of about 115°F maximum. An excess of benzene is used to suppress the formation of by-products. Aluminum chloride requirement is 5 to 10 wt% of dodecene. After removal of aluminum chloride sludge, the reaction mixture is fractionated to recover excess benzene (which is recycled to the reaction vessel), a light alkylaryl hydrocarbon, dodecylbenzene, and a heavy alkylaryl hydrocarbon.

81. Sulfonation of the dodecylbenzene may be carried out continuously or batch-wise under a variety of operating conditions using sulfuric acid (100 percent), oleum (usually 20 percent SO3), or anhydrous sulfur trioxide. The optimum sulfonation temperature is usually in the range of 100 to 140°F depending on the strength of acid employed, mechanical design of the equipment, etc. Removal of the spent sulfuric acid from the sulfonic acid is facilitated by adding water to reduce the sulfuric acid strength to about 78 percent. This dilution prior to neutralization results in a final neutralized slurry having approximately 85 percent active agent based on the solids. The inert material in the final product is essentially Na2SO4.

82. The sulfonic acid is neutralized with 20 to 50 percent caustic soda solution to a pH of 8 at a temperature of about 125°F. Chemical “builders” such as trisodium phosphate, tetrasodium pyrophosphate, sodium silicate, sodium chloride, sodium sulfate, carboxymethyl cellulose, etc., are added to enhance the detersive, wetting, or other desired properties in the finished product. A flaked, dried product is obtained by drum drying or a bead product is obtained by spray drying.

83. Chemical Process Simulators
This is a list of software used to simulate the material and energy balances of chemical processing plants.
APMonitor Modeling Language
ASCEND
Aspen Plus, Aspen HYSYS, Aspen Custom Modeler by Aspen Technology
ASSETT, D-SPICE and K-Spice by Kongsberg Oil & Gas Technologies AS
CADSIM Plus by Aurel Systems Inc.
CHEMASIM, inhouse thermodynamical simulation program at BASF
CHEMCAD by Chemstations
COCO simulator
COMSOL Multiphysics
Design II for Windows by WinSim Inc.
Distillation Expert Trainer [1]
DWSIM (open-source)
EcosimPro
EMSO, the Environment for Modelling, Simulation and Optimisation from the ALSOC Project
Dymola
FlowManager™ by FMC Technologies
GIBBSim
gPROMS by PSE Ltd

84. INDISS by RSI
ICAS: Integrated Computer Aided System developed by CAPEC
IDEAS by Andritz Automation
ISE Simulator by VRTech
Jacobian (Numerica Technology)
LIBPF, the C++ LIBrary for Process Flowsheeting
Mobatec Modeller by Mobatec
OLGA by SPT Group (Scandpower)
Omegaland by Yokogawa
OpenModelica
PIPE-FLO Professional by Engineered Software, Inc.
PottersWheel Matlab toolbox to calibrate parameters in chemical reaction networks (free for edu/academic usage)
Prode Sim, Properties
ProSimulator by Sim Infosystems
ProSimPlus by ProSim
Petro-SIM
PETROX
ProMax, TSWEET, and PROSIM by Bryan Research and Engineering
PRO/II,DYNSIM and ROMeo[1]ROMeo_(process_optimizer)

85. RecoVR by VRTech
Sim42 by Raul Cota and others
SimCreate by TSC Simulation
Simulis by ProSim
SPEEDUP by Roger W.H. Sargent and students
SolidSim - flowsheet simulation of solids processes by SolidSim Engineering GmbH
SuperPro Designer by Intelligen
SysCAD
System7 by Epcon International
UniSim Design & Shadow Plant by Honeywell
Usim Pac by Caspeo
VMGSim by Virtual Materials Group

86. Main principle
Process flow diagram of a typical amine treating process used in industrial plants
Process simulation is a model-based representation of chemical, physical, biological, and other technical processes and unit operations in software. Basic prerequisites are a thorough knowledge of chemical and physical properties[1] of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of a process in computers.
Process simulation software describes processes in flow diagrams where unit operations are positioned and connected by product or educt streams. The software has to solve the mass and energy balance to find a stable operating point. The goal of a process simulation is to find optimal conditions for an examined process. This is essentially an optimization problem which has to be solved in an iterative process.

88. Process simulation always use models which introduce approximations and assumptions but allow the description of a property over a wide range of temperatures and pressures which might not be covered by real data. Models also allow interpolation and extrapolation - within certain limits - and enable the search for conditions outside the range of known properties.

89. Modelling
The development of models[2] for a better representation of real processes is the core of the further development of the simulation software. Model development is done on the chemical engineering side but also in control engineering and for the improvement of mathematical simulation techniques. Process simulation is therefore one of the few fields where scientists from chemistry, physics, computer science, mathematics, and several engineering fields work together.
VLE of the mixture of Chloroform and Methanol plus NRTL fit and extrapolation to different pressures

90. A lot of efforts are made to develop new and improved models for the calculation of properties. This includes for example the description of thermophysical properties like vapor pressures, viscosities, caloric data, etc. of pure components and mixtures properties of different apparatuses like reactors, distillation columns, pumps, etc. chemical reactions and kinetics environmental and safety-related data
Two main different types of models can be distinguished:
Rather simple equations and correlations where parameters are fitted to experimental data.
Predictive methods where properties are estimated.
The equations and correlations are normally preferred because they describe the property (almost) exactly. To obtain reliable parameters it is necessary to have experimental data which are usually obtained from factual data banks[3][4] or, if no data are publicly available, from measurements.

91. Using predictive methods is much cheaper than experimental work and also than data from data banks. Despite this big advantage predicted properties are normally only used in early steps of the process development to find first approximate solutions and to exclude wrong pathways because these estimation methods normally introduce higher errors than correlations obtained from real data.
Process simulation also encouraged the further development of mathematical models in the fields of numerics and the solving of complex problems

92. History
The history of process simulation is strongly related to the development of the computer science and of computer hardware and programming languages. First working simple implementations of partial aspects of chemical processes have been made in the 1970 where, for the first time, suitable hardware and software (here mainly the programming languages FORTRAN and C) have been available. The modelling of chemical properties has been started already much earlier, notably the cubic equation of states and the Antoine equation are developments of the 19th century.

93. Steady state and dynamic process simulation
Initially process simulation was used to simulate steady state processes. Steady-state models perform a mass and energy balance of a stationary process (a process in an equilibrium state) but any changes over time had to be ignored.
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into the models via derivative terms i.e. accumulation of mass and energy. The advent of dynamic simulation means that the time-dependent description, prediction and control of real processes in real time has become possible. This includes the description of starting up and shutting down a plant, changes of conditions during a reaction, holdups, thermal changes and more.

94. Dynamic simulations require increased calculation time and are mathematically more complex than a steady state simulation. It can be seen as a multiply repeated steady state simulation (based on a fixed time step) with constantly changing parameters.
Dynamic simulation can be used in both an online and offline fashion. The online case being model predictive control, where the real-time simulation results are used to predict the changes that would occur for a control input change, and the control parameters are optimised based on the results. Offline process simulation can be used in the design, troubleshooting and optimisation of process plant as well as the conduction of case studies to assess the impacts of process modifications.