Pressure-Vacuum Swing Permeation: A Novel Process for Gas Separations

A novel process mode for gas separation by means of membranes was presented. It involved cyclic pressure-vacuum swings for feed pressurization and permeate evacuation, thereby increasing the transmembrane pressure difference and the feed to permeate pressure ratio. The feed pressurization and permeate evacuation were preferably accomplished using a single pump capable of pressurization and suction. Unlike transient permeation processes reported in the literature which were based on the differences in sorption uptake rates or desorption falloff rates, this process was based on the selective permeability of the membrane for separations. The dynamic gas permeation process associated with the pressure-vacuum swing permeation was analyzed to elucidate the working principle of the process, and a parametric study was carried out to evaluate the effects of design and operating parameters on the separation performance. To exemplify the feasibility and effectiveness of the process, air separation for oxygen enrichment and CO2 separation from lanfill gas were investigated as representative applications. It was shown that the separation efficiency was enhanced by means of the pressure-vacuum swing, and both product purity and product throughput higher than those from conventional steady-state permeation could be obtained.