15D-22 |
Modeling concentration polarization of pervaporation processes in aroma and flavor recovery |
P. K. MAMIDIPALLY1, L. M. Vane2, and S. X. Liu1. (1) Dept. of Food Science, Rutgers, The State Univ. of New Jersey, Cook Campus, 65 Dudley Rd., New Brunswick, NJ 08901, (2) National Risk Management Research Lab., U.S. Environmental Protection Agency, 26 W. Martin L. King Dr., Cincinnati, OH 45268 Membrane pervaporation has been widely used in many industrial and environmental applications and is gradually gaining acceptance in food and beverage industry for flavor and aroma recovery. A common technical challenge encountered in the application of this technology is the existence of a phenomenon called concentration polarization, a steep concentration discrepancy between concentration in the bulk and that on the membrane surface, and its adverse effect upon the process performance. In order to better understand the physical picture of mass transfer occurring in the pervaporation process to facilitate process design and optimization without committing costly large-scale experiments, a system mass transfer model is usually developed and the results from the simulation of the model are used for initial process development. Our objective was to develop a pervaporation mass transfer model that will provide complete descriptions of mass transfer in the liquid boundary layer, descriptions that use exact physical pictures of specific fluid-solid-molecule interfaces in a plate-and-frame membrane module. The classical boundary-layer theory was adopted as a basis of modeling effort.Power series of fourth degree has been assumed for velocity and concentration boundary layer profiles in developing this model.The resulting modeling equation for the membrane module was solved analytically. Simulations were carried out for a plate and frame pervaporation module with the following operating parameters: v=0.7 m/s, C=1.0kg/m3, T=300C, Pvac=1 torr. The simulated results indicated that our model is generally comparable to the experimentally observed results for the module type that the model describes. The developed model allows us to analyze the effect of degree of concentration polarization on permeate flux and also on local variations of mass transfer rate in the liquid boundary layer. This modeling effort will help in improving the design of the process and thus its operation efficiency.
Session 15D, Food Engineering: Processing Technologies
|