ChE-PAST, PRESENT & FUTURE

What is Chemical Engineering?

Since its birth in the last century, the fundamel7;tal paradigm of chemical engineering has gone through a series of dramatic changes,

and more are on the way.

Chemical engineering has impacted on society in many ways: it is difiicult to visualize the world with-out the large volume production of antibiotics. fer-

tilizers, agricultural chemicals, special polymers for biomedical devices, high-strength polymer composites, and synthetic fibers and fabrics . All of these require that spe-cially designed chemicals and materials be produced eco-nomically with minimal adverse impact on the environment. Developing this ability and implementing it on a practical scale are what chemical engineering is all about.

Chemical engineering. however, is more than a group of products or a pile of economic statistics. As an intellectual discipline it has its characteristic set of problems and sys-tematic methods for obtaining their solutions; that is. its paradigm. Since the birth of chemical engineering in the last century, its fundamental paradigm has gone through a series of dramatic changes, and more are on the way.

The Massachusetts Institute of Technology started a chemical engineering program in 1888 as an option in its Chemistry Dept. The curriculum largely described indus-trial operations and was organized by specific products. The detailed knowledge for one product often seemed quite different from that of another however, and the need for a paradigm soon became apparent.

The first paradigm, for solving the problems of economi-cally producing commodity products on a large scale, was based on a unifying concept of "unit operations"-proposed by Arthur D. Little in 1915. The tools of chemical engi- . nee ring analysis during this period were supplemented by 1

studies on materials and energy balances of processes (j,rid by fundamental thermodynamic studies on multicomponent systems.

The material has been adapted from The National Research Council's report, "Frontiers of Chemical Engineering." and is published with the permission of The National Academy Press. The complete report can be ordered from The National Academy Press, 2101 Constitution Avenue. N.W. . Washington. DC 20418. If ordered by an AIChE membe~ before February 1, the cost is $15.00. The report can be charged to American Express, Visa. and Master Card.

January 1988

The "high noon" of American dominance in chemical manufacturing after World War II saw the gradual exhaus-tion of research problems in conventional unit operations. This led to the rise of a second paradigm for chemical en-gineering, pioneered by the Engineering Science move-ment. Chemical engineers began to reexamine some unit operations from a more fundamental point of view, using principles of contemporary science to develop quantitative, mechanistic models. Mathematical models of processes and reactors were developed and applied with considerable suc-cess, particularly in the capital-intensive oil refining and commodity petrochemical industries.

Parallel to the development of the Engineering Science movement was the evolution of the core chemical engineer-ing curriculum in its present form . The core curriculum is responsible for the confidence with which chemical engi-neers integrate knowledge from many disciplines for the solution of complex problems. The curriculum provides a background in some of the basic sciences including:

mathematics (calculus, differential equations, and, in-creasingly, linear algebra)

physics (atomic and molecular physics. electricity and magnetism, and mechanics)

chemistry (inorganic, organic, and physical) This background is essential for a rigorous study of topics central to chemical engineering:

multicomponent thermodynamics and kinetics transport phenomena reaction engineering process design and control plant design and systems engineering for process

safety, environmental protection, and economic oper-ation

This training has allowed chemical engineers to expand the boundaries of the discipline into interdisciplinary areas such as catalysis, colloid science, combustion, electrochem-ical engineering, and polymer technology.

A new paradigm Over the next few years, technological challenges and

economic forces should shape a new chemical engineering

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Enduring and emerging challenges In the new paradigm for chemlca~ engineering.

Enduring Challenges

Manufacture of homogeneous materials from small molecules

Manufacture of inexpensive commodity materials

Products with long life cycles Competing in national markets Competition based on price and availability

DeSigning processes

Large-volume processes Continuous processing Building industrial plants dedicated to a single product or process

Capital- intensive facilities

Intradisciplinary research Simple models and approximate solutions

A few simple analytical instruments

Careers built around a single product line or process Research and education at the mesoscale (equipment level)

Emerging Challenges

Manufacture of composite and structured materials from large molecules

Manufacture of expensive, high-performance, specialty materials

Products with short life cycles Competing in global markets Competition based on quality and product performance

Designing products with special performance characteristics

Small-scale processes Batch processing Building flexible manufacturing plants

Facilities for which the cost of research and design is a larger fraction of total cost

MultidiSciplinary research Large computers, better approximations, and more complete solutions

Many sophisticated analytical instruments

Multiple career changes

Research and education at the microscale (molecular level) and macroscale (systems level)

paradigm that will have a profound effect on the future of the profession. A major force behind the evolution of this paradigm is the explosion of new products and materials that should come to market in the next two decades. These products and materials from the biotechnology. electronics. and high-performance materials industry are critically de-pendent on structure and design at the molecular level. They require manufacturing processes that can precisely control chemical composition and molecular structure.

The essence of chemical engineering has always been the synthesis. design, testing. scaleup. operation. control. and optimization of processes that change the physical state or composition of materials. Traditionally. chemical engineers have focused on a level of size and complexity that may be termed the mesoscale. The mesoscale is typified by reac-tors and equipment for single processes (unit operations) and the combination of unit operat ions in manufacturing plants. Research on important mesoscale problems has been increasingly supplemented by in-depth investigations of phenomena on a microsca/e (at molecular dimensions) and of extremely complex systems. the macrosca/e. Chemi-

cal engineers in the future will have to meet the challenge of manufacturing sophisticated products on the scale of grams and kilograms rather than kilotons, and develop processes that demand hitherto unattainable levels of pro-cess control and chemical purity. They will also have to find ways to improve the overall effectiveness of manufac-turing systems to meet worldwide competition as well as, most importantly, to assure that these systems do not en-danger health, safety or the environment.

The new paradigm of chemical engineering will evolve from this change of scale; its key thrw.1: will be the chemi-cal engineering of microscale processing. Chemical engi-neers must have a thorough understanding of molecular science (the microscalel in addition to the traditional areas of mesoscale and macroscale processing.

In fact, future chemical engineers will have to integrate a wider range of scales than any other branch of engineering as they work to relate the macroscale of the environment to the microscale of molecular reactions and transport, or the macroscale performance of a composite aircraft to the microscopic design and processing of its structural compo-nents. Some things. though, will not change. The underly-ing philosophy of how to train chemical engineers. empha-sizing basic principles that are relatively immune to changes in field of application - these must remain con-stant if future chemical engineers are to master the broad spectrum of problems they will encounter .

~ Add: 1. b. altno., as paradigm case, a caSe or in.stan