(222a) Product Design Vs. Process Design - It Does Not Have to Be One or the Other

There has been much recent discussion about whether process design or product design should be taught in the undergraduate curriculum. It need not be one or the other. Programs that teach elements of both appear to segregate the subjects. It is possible to design a product in which the elements of the product are produced by a chemical process.

For example, consider a hydrogen fuel cell, using proton-exchange membranes, that could be used to power a wheelchair or be used by the military in the field to recharge batteries. A novel idea for such a hydrogen fuel cell is to immobilize hydrogenase on single-walled, carbon nanotubes. The carbon nanotubes stabilize the hydrogenase enzyme, permitting operation at higher temperatures, and hydrogenase catalyzes the water formation reaction. Traditional hydrogen fuel cells use platinum catalyst. The advantage of hydrogenase is that it is not poisoned by CO, so lower grade hydrogen can be used. The disadvantages include the lower voltage produced requiring a larger fuel-cell stack. The carbon nanotubes are made by plasma-enhanced chemical vapor deposition, and hydrogenase, which can be produced by a variety of bacteria, is isolated using freeze-thaw lysis, centrifugation, and chromatography.

The elements of product design can be taught by identifying the need for mobile power, and the product selected after many ideas are generated and evaluated. It is the manufacturing step that requires chemical processing, as long as it is assumed that these items are to be manufactured in house rather than purchased, an easy constraint to add to any design project. In this example, the steps required for production of the elements of the fuel cell involve non-traditional unit operations; however, this need not be the case. Since these production steps involve batch-type operations, scheduling must be considered.

Some product designs might also involve designing efficient manufacturing and packaging operations. For example, manufacture of a transdermal drug patch could involve production of the drug, production of the patch (which is done in large sheets), cutting the sheets to obtain the desired product, and both single-unit packaging and packaging single units into larger boxes.

As chemical engineers move into product design, batch operations, batch scheduling, efficient manufacturing operations, and packaging operations can all be included in the design experience. However, manufacture of the chemical elements of the product can also retain elements of process design.

Finally, these types of projects could also be made interdisciplinary by, for example, involving industrial engineers in the manufacturing design. An alternative would be to divide up a class into teams, in which each team was responsible for a portion of the product or process design, and require that they communicate and combine their designs into one complete design.