Chemical engineering is the branch of engineering that applies the physical sciences (e.g., chemistry and physics) and/or life sciences (e.g., biology, microbiology and biochemistry) together with mathematics and economics to processes that convert raw materials or chemicals into more useful or valuable forms. In addition, modern chemical engineers are also concerned with pioneering valuable materials and related techniques – which are often essential to related fields such as nanotechnology, fuel cells and biomedical engineering. Within chemical engineering, two broad subgroups include 1) design, manufacture, and operation of plants and machinery in industrial chemical and related processes ("chemical process engineers"); and 2) development of new or adapted substances for products ranging from foods and beverages to cosmetics to cleaners to pharmaceutical ingredients, among many other products ("chemical product engineers").
A 1996 British Journal for the History of Science article cites James F. Donnelly for mentioning a 1839 reference to chemical engineering in relation to the production of sulfuric acid. In the same paper however, George E. Davis, an English consultant, was credited for having coined the term. The History of Science in United States: An Encyclopedia puts this at around 1890. "Chemical engineering", describing the use of mechanical equipment in the chemical industry, became common vocabulary in England after 1850. By 1910, the profession, "chemical engineer", was already in common use in Britain and the United States.
Chemical engineering emerged upon the development of unit operations, a fundamental concept of the discipline chemical engineering. Most authors agree that Davis invented unit operations if not substantially developed it. He gave a series of lectures on unit operations at the Manchester Technical School (University of Manchester today) in 1887, considered to be one of the earliest such about chemical engineering. Three years before Davis' lectures, Henry Edward Armstrong taught a degree course in chemical engineering at the City and Guilds of London Institute. Armstrong's course "failed simply because its graduates ... were not especially attractive to employers." Employers of the time would have rather hired chemists and mechanical engineers. Courses in chemical engineering offered by Massachusetts Institute of Technology (MIT) in the United States, Owen's College in Manchester, England and University College London suffered under similar circumstances.
Starting from 1888, Lewis M. Norton taught at MIT the first chemical engineering course in the United States. Norton's course was contemporaneous and essentially similar with Armstrong's course. Both courses, however, simply merged chemistry and engineering subjects. "Its practitioners had difficulty convincing engineers that they were engineers and chemists that they were not simply chemists." Unit operations was introduced into the course by William Hultz Walker in 1905. By the early 1920s, unit operations became an important aspect of chemical engineering at MIT and other US universities, as well as at Imperial College London. The American Institute of Chemical Engineers (AIChE), established in 1908, played a key role in making chemical engineering considered an independent science, and unit operations central to chemical engineering. For instance, it defined chemical engineering to be a "science of itself, the basis of which is ... unit operations" in a 1922 report; and with which principle, it had published a list of academic institutions which offered "satisfactory" chemical engineering courses. Meanwhile, promoting chemical engineering as a distinct science in Britain lead to the establishment of the Institution of Chemical Engineers (IChemE) in 1922. IChemE likewise helped make unit operations considered essential to the discipline.
New concepts and innovations 
By the 1940s, it became clear that unit operations alone was insufficient in developing chemical reactors. While the predominance of unit operations in chemical engineering courses in Britain and the United States continued until the 1960s, transport phenomena started to experience greater focus. Along with other novel concepts, such process systems engineering (PSE), a "second paradigm" was defined. Transport phenomena gave an analytical approach to chemical engineering while PSE focused on its synthetic elements, such as control system and process design. Developments in chemical engineering before and after World War II were mainly incited by the petrochemical industry, however, advances in other fields were made as well. Advancements in biochemical engineering in the 1940s, for example, found application in the pharmaceutical industry, and allowed for the mass production of various antibiotics, including penicillin and streptomycin. Meanwhile, progress in polymer science in the 1950s paved way for the "age of plastics".
Lag and environmental awareness 
The years after the 1950s are viewed[by whom?] to have lacked major chemical innovations. Additional uncertainty was presented by declining prices of energy and raw materials between 1950 and 1973. Concerns regarding the safety and environmental impact of large-scale chemical manufacturing facilities were also raised during this period. Silent Spring, published in 1962, alerted its readers to the harmful effects of DDT, a potent insecticide. The 1974 Flixborough disaster in the United Kingdom resulted in 28 deaths, as well as damage to a chemical plant and three nearby villages. The 1984 Bhopal disaster in India resulted in almost 4,000 deaths. These incidents, along with other incidents, affected the reputation of the trade as industrial safety and environmental protection were given more focus. In response, the IChemE required safety to be part of every degree course that it accredited after 1982. By the 1970s, legislation and monitoring agencies were instituted in various countries, such as France, Germany, and the United States.
Recent progress 
Advancements in computer science found applications designing and managing plants, simplifying calculations and drawings that previously had to be done manually. The completion of the Human Genome Project is also seen as a major development, not only advancing chemical engineering but genetic engineering and genomics as well. Chemical engineering principles were used to produce DNA sequences in large quantities. While the application of chemical engineering principles to these fields only began in the 1990s, Rice University researchers see this as a trend towards biotechnology.
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Chemical engineering involves the application of several principles. Key concepts are presented below.
Chemical reaction engineering 
Chemical reactions engineering involves managing plant processes and conditions to ensure optimal plant operation. Chemical reaction engineers construct models for reactor analysis and design using laboratory data and physical parameters, such as chemical thermodynamics, to solve problems and predict reactor performance.
Plant design 
Chemical engineering design concerns the creation of plans and specification, and income projection of plants. Chemical engineers generate designs according to the clients needs. Design is limited by a number of factors, including funding, government regulations and safety standards. These constraints dictate a plant's choice of process, materials and equipment.
Process design 
A unit operation is a physical step in an individual chemical engineering process. Unit operations (such as crystallization, drying and evaporation) are used to prepare reactants, purifying and separating its products, recycling unspent reactants, and controlling energy transfer in reactors. On the other hand, a unit process is the chemical equivalent of a unit operation. Along with unit operations, unit processes constitute a process operation. Unit processes (such as nitration and oxidation) involve the conversion of material by biochemical, thermochemical and other means. Chemical engineers responsible for these are called process engineers.
Transport phenomena 
Transport phenomena occur frequently in industrial problems. These include fluid dynamics, heat transfer and mass transfer, which mainly concern momentum transfer, energy transfer and transport of chemical species respectively. Basic equations for describing the three transport phenomena in the macroscopic, microscopic and molecular levels are very similar. Thus, understanding transport phenomena requires thorough understanding of mathematics.
Applications and practice 
Chemical engineers "develop economic ways of using materials and energy" as opposed to chemists who are more interested in the basic composition of materials and synthesizing products from such. Chemical engineers use chemistry and engineering to turn raw materials into usable products, such as medicine, petrochemicals and plastics. They are also involved in waste management and research. Both applied and research facets make extensive use of computers.
A chemical engineer may be involved in industry or university research where they are tasked in designing and performing experiments to create new and better ways of production, controlling pollution, conserving resources and making these processes safer. They may be involved in designing and constructing plants as a project engineer. In this field, the chemical engineer uses their knowledge in selecting plant equipment and the optimum method of production to minimize costs and increase profitability. After its construction, they may help in upgrading its equipment. They may also be involved in its daily operations. 
Related fields and topics 
See also 
- From Petroleum to Penicillin. The First Hundred Years of Modern Chemical Engineering: 1859–1959. – Burnett, J. N.
- Cohen 1996, p. 172.
- Cohen 1996, p. 174.
- Reynolds 2001, p. 176.
- Cohen 1996, p. 186.
- Perkins 2003, p. 20.
- Cohen 1996, pp. 172–173.
- Cohen 1996, p. 175.
- Cohen 1996, p. 178.
- Cohen 1996, p. 180.
- Cohen 1996, p. 183.
- Cohen 1996, p. 184.
- Cohen 1996, p. 187.
- Cohen 1996, p. 189.
- Cohen 1996, p. 190.
- Cohen 1996, p. 185.
- Ogawa 2007, p. 2.
- Perkins 2003, p. 29.
- Perkins 2003, p. 30.
- Perkins 2003, p. 31.
- Reynolds 2001, p. 177.
- Perkins 2003, pp. 32–33.
- Kim 2002, p. 7S.
- Perkins 2003, p. 34.
- Kim 2002, p. 8S.
- Perkins 2003, p. 35.
- Kim 2002, p. 9S.
- American Institute of Chemical Engineers 2003a.
- Rice University.
- Carberry 2001, pp. 1–2.
- Towler & Sinnott 2008, pp. 2–3.
- McCabe, Smith & Hariott 1993, p. 4.
- Silla 2003, pp. 8–9.
- Bird, Stewart & Lightfoot 2002, pp. 1–2.
- Garner 2003, pp. 47–48.
- American Institute of Chemical Engineers 2003, Article III.
- Garner 2003, pp. 49–50.
- American Institute of Chemical Engineers (2003-01-17), AIChE Constitution, retrieved 2011-08-13.
- Bird, R. Byron; Stewart, Warren E.; Lightfoot, Edwin N. (2002), Kulek, Petrina, ed., Transport Phenomena (2nd ed.), United States: John Wiley & Sons, ISBN 0-471-41077-2, LCCN 2001023739, LCC QA929.B% 2001,.
- Carberry, James J. (2001-07-24), Chemical and Catalytic Reaction Engineering, McGraw-Hill Chemical Engineering Series, Canada: General Publishing Company, ISBN 0-486-41736-0, LCCN 2001017315, LCC TP155.7.C37 2001,.
- Cohen, Clive (June 1996), "The Early History of Chemical Engineering: A Reassessment", The British Journal for the History of Science (Cambridge University Press) 29 (2), JSTOR 4027832.
- Rice University, Engineering the Future of Biology and Biotechnology, retrieved 2011-08-07.
- Garner, Geraldine O. (2003), Careers in engineering, VGM Professional Career Series (2nd ed.), United States: McGraw-Hill, ISBN 0-07-139041-3, LCCN 2002027208, LCC TA157.G3267 2002,.
- Kim, Irene (January 2002), "Chemical engineering: A rich and diverse history", Chemical Engineering Progress (Philadelphia: American Institute of Chemical Engineers) 98 (1), ISSN 0360-7275.
- McCabe, Warren L.; Smith, Julian C.; Hariott, Peter (1993), Clark, B.J.; Castellano, Eleanor, eds., Unit Operations of Chemical Engineering, McGraw-Hill Chemical Engineering Series (5th ed.), Singapore: McGraw-Hill, ISBN 0-07-044844-2, LCCN 9236218, LCC TP155.7.M393 1993,.
- Ogawa, Kōhei (2007), "Chapter 1: Information Entropy", Chemical engineering: a new perspective (1st ed.), Netherlands: Elsevier, ISBN 978-0-444-53096-7.
- Perkins, J.D. (2003), "Chapter 2: Chemical Engineering — the First 100 Years", in Darton, R.C.; Prince, R.G.H.; Wood, D.G., Chemical Engineering: Visions of the World (1st ed.), Netherlands: Elsevier Science, ISBN 0-444-51309-4.
- Reynolds, Terry S. (2001), "Engineering, Chemical", in Rothenberg, Marc, History of Science in United States: An Encyclopedia, New York City: Garland Publishing, ISBN 0-8153-0762-4, LCCN 99043757, LCC Q127.U6 H57 2000,.
- Silla, Harry (2003), Chemical Process Engineering: Design and Economics, New York City: Marcel Dekker, ISBN 0-8247-4274-5.
- American Institute of Chemical Engineers (2003a), "Speeding up the human genome project", Chemical Engineering Progress (Philadelphia) 99 (1), ISSN 0360-7275.
- Towler, Gavin; Sinnott, Ray (2008), Chemical engineering design: principles, practice and economics of plant and process design, United States: Elsevier, ISBN 978-0-7506-8423-1.