DESIGN STUDIES OF MEMBRANE PERMEATOR PROCESSES FOR GAS SEPARATION

The intrinsic behaviour of several single-stage and multi-stage permea tor systems has been studied using a recently developed algebraic desi gn model. Upper and lower bounds with respect to product purity and re covery in single-stage systems are presented. It is shown that single- stage permeators without recycle can exhibit maxima in permeate purity as a function of the pressure ratio across the membrane. It is illust rated why bypass configurations may be economically profitable in sing le-stage systems. The effect of product recycle in single-stage system s has been studied. It is shown that permeate recycle can reduce the c ompressor load in single-stage permeator systems. Similar benefits of retentate recycle have not been identified. The characteristic behavio ur of multi-stage systems has been studied. Based on general design cr iteria, various module configurations have been classified as suitable for recovery of either the slowest or the fastest permeating componen t. The effect of using different membrane materials at each stage of a multi-stage permeator cascade has been studied. It is shown that impr ovements with respect to product recovery can be achieved.