Patent ID: 6159272
Filing Date: 2000-12-12
Classification: B01D,C01B

Abstract:
A process for treating an off-gas stream, containing at least hydrogen, methane and a C.sub.3+ hydrocarbon, comprising the following steps:(a) cooling the off-gas stream to a temperature no lower than about -40.degree. C., resulting in partial condensation of the off-gas stream, thereby dividing the off-gas stream into a condensed portion enriched in C.sub.3+ hydrocarbon and an uncondensed portion enriched in hydrogen;(b) passing the uncondensed portion as a feed stream to a membrane separation unit, the membrane separation unit containing a rubbery polymeric membrane having a feed side and permeate side, and being selectively permeable to methane over hydrogen, under conditions sufficient that the membrane exhibits a methane/hydrogen selectivity of at least about 2.5;(c) withdrawing from the permeate side a permeate stream enriched in methane and C.sub.3+ hydrocarbon compared with the uncondensed portion;(d) withdrawing from the feed side a hydrogen-enriched product gas;(e) passing the condensed portion to a hydrocarbon separation step for separation of a C.sub.3+ hydrocarbon fraction and a lighter hydrocarbon fraction from the condensed portion.