Asymmetric Permeators—A Conceptual Study

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Abstract
The asymmetric permeator concept of Ohno et. al. utilizing two different membranes for rare gas separation has been explored in general. Various geometrical arrangements and possible applications to gas separations other than rare gas-nitrogen mixtures have been discussed. The utility of an asymmetric permeator for multicomponent gas separations has been investigated. The separation factor of a ternary system in a perfectly mixed asymmetric permeator has been obtained. The amount of separation obtained with a ternary feed in a perfect crossflow stage having no axial mixing has been analytically determined for some limiting cases with an asymmetric permeator. The asymmetric permeator concept has been extended also to a high separation factor liquid solution separation process like reverse osmosis desalination. Preliminary calculations have been carried out to show that an asymmetric desalinator with reverse osmosis (RO) and piezodialysis (PD) membranes has a lower increase in brine concentration along the module length for a given water recovery resulting in a lower operating pressure. With hollow fiber asymmetric desalinators having RO and PD membranes, the concentration polarization, if any, may be significantly reduced. Practical applications of asymmetric permeator's for phenol-water separation etc. have been discussed.