Chemical engineering differs from chemistry mainly in the focus on large scales. The definition of "large" is a bit arbitrary, of course, but is set mainly by the scale of useful commercial production. Typically, this scale ranges from barrels to tank cars, whereas the chemist tends to be concerned sizes closer to vials to beakers.
For many years, most chemical engineers took jobs in the oil or petrochemical industry. Job functions typically involved the development or operation of processes to convert oil-based feedstocks into energy or other useful chemical products ranging from fibers for clothing to lubricants to fertilizers. In recent decades, however, job descriptions have become far more diverse. Chemical engineers often develop or operate processes to create products ranging from integrated circuits to disease-fighting drugs to fuel cells. Some recent graduates use a chemical engineering Bachelor's Degree as a launching pad for careers as physicians or patent attorneys.
The unique focus perspective of this discipline can be represented by an extension ladder, shown in the figure. The two uprights of this very useful tool represent the two primary physical foundations upon which all of chemical engineering rests: chemistry and transport. Here, "chemistry" refers to the rates and extents of transformation among substances. "Transport" refers to the movement of mass, energy or momentum.
The rungs of the ladder represent the mathematical balance equations that connect chemistry and transport. The balance equations can be time-dependent or steady state. Whatever their nature, however, these balance equations are rarely written in their own right; they are almost always written to optimize or control some variable within them. The rungs therefore also represent the use of balance equations for the optimization and control of useful commercial processes.
Chemical engineering embraces an enormous range of size scales in a fully integrated way - commonly ranging from atoms to oil tankers. The figure represents this notion by three extension segments, representing length scales corresponding to the microscopic, the bench scale (or "unit operation" in the lingo of the discipline) and the factory. At the molecular level, the balance equations might incorporate variables like temperature or pressure. At the unit operation level, the key variables might be flow rate or controller gain. At the factory level, the variables might be operating cost or overall production rate.
In a similar way, when we want to transform chemical substances, the "ladder" of chemistry/transport, balances, and optimization offers a versatile tool. The skilled chemical engineer moves continually over the span of length scales from atomic to factory-level as circumstances dictate. When designing or optimizing an overall process flow, the chemical engineer may move rapidly up and down the span of length scales. When troubleshooting a particular unit operation, however, the chemical engineer may need to stay at that level for a long time with just a few balance equations. Good chemical engineering requires a constellation of intellectual skills integrated judiciously: knowing what kind of balance equation to write, what control volume to use, what terms to neglect, when to overlap tools from different length scales, what mathematics to use. Although these skills can be described and listed, they cannot be employed algorithmically. Judicious chemical engineering requires judgment and experience, i.e., "chemical engineering wisdom." Thus, chemical engineering has been aptly called the "liberal arts of engineering."
The ability to think quantitatively and integratively about chemistry and transport over many length scales, with wise judgment born of experience, underpins the true value-added contribution of chemical engineering. This ability probably forms part of the reason chemical engineers continue to enjoy high entry-level salaries.
The face of chemical engineering is changing, and we seek to mold that change for the common good. The department is building new efforts in areas of crucial societal need such as energy and sustainability, bioprocessing, and nanotechnology.
One particularly fast-growing and important area is biotechnology. Biomolecular engineering can be considered to be a subset of chemical engineering. Biomolecular engineering narrows the focus primarily to the bottom (molecular) length scale of the ladder, and to applications drawn specifically from biological and health-oriented fields. By contrast, bioengineering (a distinct discipline) currently focuses primarily on the non-molecular aspects of the nexus between biology and engineering. Example applications include human and animal imaging, the development of medical devices, and the mechanical (as opposed to chemical) aspects of human tissue engineering.
