Integrated membrane/adsorption process for gas separation

Abstract

A novel process that incorporates membrane permeation into the cyclic process of pressure swing adsorption (PSA) was proposed to improve gas separation performance. This integration is not a simple combination of the two process components. Unlike in the traditional membrane processes where pressures are kept constant, the pressure in the integrated permeation/adsorption system is changing as the permeation proceeds with time. Permeation processes with varying pressure were analyzed parametrically to study the feasibility of integrating permeation with cyclic PSA processes. Two configurations of the process integration were investigated: membrane-assisted feed gas pressurization, and membrane-assisted co-current depressurization. A bench scale unit comprising of an asymmetric cellulose acetate hollow fiber module and a pair of 5 A molecular sieve packed bed adsorbers was assembled and tested for hydrogen purification. It was shown that as compared to the simple adsorption process, both product purity and recovery could be improved by using the integrated process, and the improvement was especially remarkable for the cases where the feed gas mixture contained impurities that were difficult to remove by adsorption.