A Simple Model for Pervaporation Design

Membrane separation processes, from reverse osmosis to ultrafiltration to microfiltration, are gradually receiving more and more emphasis in undergraduate chemical engineering curricula. Of these processes, ultrafiltration tends to be the most amenable to the standard chemical engineering approach of theory development, mass and/or energy balancing, and subsequent problem solving, whether it be process design, process analysis, or process optimization. Pervaporation is a less well-known membrane separation technique that is used mainly for the removal of small quantities of water from organic solvents. While a large body of academic research exists into the precise mechanism of vapor transport through pervaporation membranes, less emphasis has been put on chemical engineering analyses to predict the performance of existing pervaporation modules, or to aid in the design of new ones. The purpose of this paper is to outline a simple design methodology for calculating the area of a single-stage, single-pass pervaporation system, a methodology that will be accessible to undergraduates. The approach presented in this article requires no new knowledge of the precise mechanism of vapor transport in the membrane and employs standard mass and energy balances that will be very familiar to chemical engineering students in their junior and/or senior years.