"Any chemical process, on whatever scale conducted, may be resolved into a coordinate series of what may be termed 'unit operations'. . . the number of these basic unit operations is not large and relatively few of them are involved in any particular process. The complexity of chemical engineering results from the variety of conditions as to temperature, pressure, etc., under which the unit operations must be carried out in different processes, and from the limitations as to material of construction and design of apparatus imposed by the physical and chemical character of the reacting substances."

-Arthur D. Little, 1915

Unit operations are the fundamental building blocks of chemical process design; they are the conceptual tool which defines the field of chemical engineering and separate it from other disciplines. It is the unique job of the chemical engineer to choose which types of units to include, how many of each, how they will be run, and how they are connected together to produce a final flowsheet which performs some purpose. This is the science behind chemical engineering and it is still an active and productive research field.

As there are an infinite number of ways to produce a product from some set of inputs, a chemical engineer must in the course of his or her job answer the question “How good is my flowsheet?” The evolution of computer-aided process design has given this designer a multitude of different tools to answer this question. As our field and our society mature, the definition of “good” also changes and evolves; a flowsheet which may have been “good” in 1960 (or even 2005) may now be “bad” due to changes in the cost of raw materials, rising energy costs, stricter emissions standards, increased safety of operation, etc. What this means is that a process designer must be in tune with this “multi-objective” world and do his job using the latest tools available.

The goal of my research is threefold: first, to enhance these tools using the techniques of optimization so that they perform more efficiently and can solve bigger and more general problems; secondly, to identify bounds on the performance of units and flowsheets to give real process designers benchmarks to compare their work to; thirdly, to advise and educate future process engineers in the most state-of-the-art methods for designing and operating their plants in the most energy efficient, cost-effective, and sustainable way possible. My thesis work has focused on the development of one such process design method, the Infinite DimEnsionAl State-space framework (IDEAS). IDEAS, in short, is a way to represent all possible flowsheets simultaneously to eliminate infeasible flowsheets, identify properties of “good” or optimal flowsheets, and to give lower bounds on the best flowsheet for a given design problem. I have applied this method to networks of batch reactors [Davis et al. “Identification of the Attainable Region for Batch Reactor Networks” Ind. Eng. Chem. Res., in press], networks of PEM fuel cells, power generation cycle flowsheets, and cryogenic liquefaction flowsheets.