CHEMICAL ENGINEERING

the development of processes and the design and operation of plants in which materials undergo changes in their physical or chemical state. Applied throughout the process industries, it is founded on the principles of chemistry, physics, and mathematics. The laws of physical chemistry and physics govern the practicability and efficiency of chemical engineering operations. Energy changes, deriving from thermodynamic considerations, are particularly important. Mathematics is a basic tool in optimization and modeling. Optimization means arranging materials, facilities, and energy to yield as productive and economical an operation as possible. Modeling is the construction of theoretical mathematical prototypes of complex process systems, commonly with the aid of computers. the development of processes and the design and operation of plants in which materials undergo changes in their physical or chemical state. Although the basic concepts were developed only about a century ago, several aspects that are now accepted within the definition of chemical engineering have been known for thousands of years, the most notable examples being the distillation of alcoholic beverages and the evaporation of brine. The chemical industry began to develop to a significant extent during the second decade of the 20th century. There are two distinct ancestral lines of this industry as it is today, notably that originating in the chemical industries of western Europe, particularly those based on coal as the raw material, and that with its roots in the oil-refining industry of North America. The impetus for the development of the chemical-engineering industry in Europe arose during World War I. Many countries were at that time cut off from their traditional suppliers of chemicals (particularly Germany) and were therefore forced to build their own chemical industries. Simultaneously with the evolution of the European industry from this base, there was a growing demand in North America for petroleum-based products for the motor industry. This oil boom created a demand for entirely new techniques and plants. Such new techniques were not of great interest in Europe, where there was no oil-refining industry at that time. Between the two World Wars, the chemical industry in general was characterized by a period of slow growth, but during World War II the technology base of North America grew very quickly. A vast secondary industry based on oil feedstocks took shape in North America, developing products such as synthetic rubbers, man-made fibres, and plastics. During this period, completely different techniques of chemical and process engineering were used in Europe, where the industry was still coal-based and mainly concerned with inorganic- and general-chemicals processing rather than with oil and petrochemicals. Only over the past few decades have the two branches coalesced. There are six main types of activity in the chemical-engineering field, namely research, design, construction, operation, sales, and management. Several of these activities frequently overlap. The original chemical engineers were usually trained formally as either chemists or mechanical engineers, gaining appropriate experience of the other aspects of their profession on the job, but over the past 50 years the profession has gradually become recognized in its own right. A chemical engineer must be well versed in the three main disciplines used in the profession, namely chemistry, physics, and mathematics. In addition, the competent chemical engineer must be an industrial economist, thinking habitually in terms of world resources of raw materials and of world markets for finished products and also taking into consideration the capital and operating costs of a processing plant. The chemical engineer is concerned not only with the nature of chemical reactions but also with such aspects as the effects of temperature and pressure on reaction equilibria and the effects of catalysts on rates of reaction. However, the major part of the work of a chemical engineer is concerned not with chemical reactions but with the unit operations of chemical engineering. These are the engineering science and technology of fluid flow, heat transfer, evaporation, distillation, absorption, filtration, extraction, crystallization, and various other operations. As well as working in the chemical and oil industries, chemical engineers are employed in a wide range of other process industries, such as the food and paper industries, with some of the newer industries (nuclear, biotechnology) also claiming a growing number of chemical engineers. Additional reading A treatment of the history of the field is contained in W.F. Furter (ed.), History of Chemical Engineering (1980), and A Century of Chemical Engineering (1982). Classic works include George E. Davis, A Handbook of Chemical Engineering, 2nd ed., 2 vol. (1904); and William H. Walker et al., Principles of Chemical Engineering, 3rd ed., rev. and rewritten (1937). More recent information may be found in Don W. Green and James O. Maloney (eds.), Perry's Chemical Engineers' Handbook, 6th ed. (1984), a comprehensive handbook; D.J. Hagerty, E. Gearhard, and C. Plank, Chemical Engineering (1989); J.M. Coulson, Chemical Engineering: An Introduction to Design (1983); and J.M. Coulson et al., Chemical Engineering, 6 vol. in various editions (1977-96), a general textbook. Carl Hanson The Editors of the Encyclopdia Britannica