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'''Process design''' in the field of [[chemical engineering]] is the design of industrial processes to produce desired physical and/or chemical transformation of substances. Process design is central to [[chemical engineering]] and it integrates most of the basic components of that field. The design starts at a conceptual level and ends with the writing of specifications for fabricating the process equipment items and development of documents needed for construction of the overall processing facility.<ref name=Sinnott>{{cite book|author=R.K. Sinnott|title=Chemical Engineering Design|edition=4th Edition|publisher=Butterworth-Heinemann|year=2005|id=ISBN 0-7506-6538-6}} Volume 6 of Coulson & Richardson's Chemical Engineering Series</ref><ref name=Silla>{{cite book|author=Harry Silla|title=Chemical Process Engineering Design and Economics|edition=1st Edition|publisher=Marcel Dekker|year=2003|id=ISBN 0-8247-42274-5}}</ref>


Process design includes the modification or expansion of existing industrial facilities as well as the design of new industrial facilities. 
Although chemical engineering is involved in the design of many equipment items used in industrial chemical processes, equipment design is not usually included in process design.
==Process design diagrams and other documents==
{{Image|Process Design.png|right|307px|Sequence of steps in a typical chemical engineering process design.}}
Process design documents serve to define the design and they ensure that the design components fit together.  They are useful in communicating ideas and plans to other engineers involved with the design, to external regulatory agencies, to equipment vendors and to construction contractors.
In order of increasing detail, process design documents include:<ref name=Sinnott/><ref name=Silla/>
*'''[[Block flow diagrams|Block Flow Diagrams (BFDs)]]''': Very simple diagrams indicating major material and/or [[energy]] flows.
*'''[[Process flow diagram|Process Flow Diagrams (PFDs]]''': Typically more complex diagrams of major unit operations that include the key equipment items as well as the key flow lines.  They usually include a material balance, and sometimes an energy balance, listing typical or design flow rates, key stream compositions, and the [[pressure]]s and [[temperature]]s of the key stream and equipment items. A PFD may include the amount of [[heat]] to be provided by any [[process furnaces]] as well as the amount of heat exchanged by any process [[heat exchangers]] and [[Continuous distillation|distillation]] [[reboiler]]s.
*'''[[Piping and Instrumentation Diagram|Piping and Instrumentation Diagrams (P&IDs)]]''': Diagrams showing all major and minor equipment items as well as each and every pipeline with piping class (e.g., carbon steel or stainless steel) and pipe size (diameter). They also show all valving along with all instrument locations and [[process control]] systems.
*'''[[Equipment specification]]s''': Written design requirements of all major equipment items.
Process designers also typically write operating manuals on how to start-up, operate and shut-down the process.
After construction and initial start-up operation of the process facility, the process design documents are retained by the facility management and operating personnel for future reference as may be needed. The documents are also  useful when facility modifications or expansions are planned.
==Design Considerations==
Designs have objectives and constraints, and even a simple process requires a trade-off among such factors.
'''Objectives''' that a process design strives to include:
:*Throughput rates
:*Product yields
:*Product purities
'''Constraints''' that must be accommodated:
:*Capital cost
:*Available space
:*Safety concerns
:*[[Environmental impact assessment|Environmental impact]] and projected [[wastewater]] effluents, [[air pollutant]] emissions and production of [[solid waste]]s.
:*Operating and maintenance costs
'''Other factors''' that designs may take into consideration are:
:*Equipment redundancy to improve operational reliability and flexibility.
:*Anticipated variability in feedstock and allowable variability in product.
==Sources of Design Information==
Designers rarely start from scratch, especially for complex projects.  Often the engineers have [[pilot plant]] data available or data from full-scale operating facilities. Other sources of information include proprietary design criteria provided by process licensors, published scientific data, laboratory experimental data and input.
==Computer Help==
The advent of low cost powerful computers has aided complex mathematical simulation of processes, and simulation software is often used by design engineers.  Simulations can identify weaknesses in designs and allow engineers to choose better alternatives.
However, engineers still rely on experience, logic and intuition when designing a process.  Human creativity is still an important  element in complex designs.
==References==
{{reflist}}
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'''Related Articles subpage'''
* [[Chemical engineering]]
* [[Chemical plant]]
* [[Process simulation]]
* [[Environmental engineering]]
* [[List of Chemical Process Simulators]]
* [[List of Dynamic Process Simulators]]
* [[Process engineering]]
* [[Process safety]]
* [[Unit operation]]
* [[Unit process]]
'''Bibliography subpage'''
*{{cite book|author=Kister, Henry Z.|title=[[Distillation Design]]|edition=1st Edition |publisher=McGraw-Hill|year=1992|isbn=0-07-034909-6}}
*{{cite book|author=Perry, Robert H. and Green, Don W.|title=[[Perry's Chemical Engineers' Handbook]]|edition=6th Edition| publisher=McGraw-Hill|year=1984|isbn=0-07-049479-7}}
*{{cite book|author=[[Robert Byron Bird|Bird, R.B.]], Stewart, W.E. and [[Edwin N. Lightfoot|Lightfoot, E.N.]]|title=[[Transport Phenomena]]|edition=Second Edition|publisher=John Wiley & Sons|year=August 2001|isbn=0-471-41077-2}}
*{{cite book| author=McCabe, W., Smith, J. and Harriott, P.|edition=7th Edition|title=[[Unit Operations of Chemical Engineering]]|publisher=McGraw Hill|location=|year=2004|isbn=0-07-284823-5}}
*{{cite book|author= Seader, J. D., and Henley, Ernest J.|title=Separation Process Principles|publisher=Wiley| location=New York|year=1998|isbn=0-471-58626-9}}
* {{cite book|author=Chopey, Nicholas P.|title=Handbook of Chemical Engineering Calculations|edition=3rdEdition|publisher=McGraw-Hill|year=2004|isbn=0071362622}}
*{{cite book|author=Himmelbau, David M.|title=Basic Principles and Calculations in Chemical Engineering|edition=6th Edition|publisher=Prentice-Hall|year=1996|isbn=0133057984}}
*{{cite book| author=Editors: Jacqueline I. Kroschwitz and Arza Seidel|edition=5th Edition|title=Kirk-Othmer Encyclopedia of Chemical Technology|publisher=Wiley-Interscience|location=Hoboken, NJ|year=2004|isbn=0-471-48810-0}}
*{{cite book|author=King, C.J.|title=Separation Processes|publisher=McGraw Hill|year=1980|isbn=0-07-034612-7 |edition=2nd }}
*{{cite book|author=Peters, M. S., and Timmerhaus K. D.|year=1991|title=Plant Design and Economics for Chemical Engineers|publisher=McGraw Hill|edition=4th edition|isbn=0-07-100871-3}}
*{{cite book|author=J. M. Smith, H. C. Van Ness and M. M. Abott|year=2001|title=Introduction to Chemical Engineering Thermodynamics|publisher=McGraw Hill|edition=6th edition|isbn=0-07-240296-2}}
'''External Links subpage'''

Revision as of 03:33, 26 April 2010

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