Patent ID: 6478852
Filing Date: 2002-11-12
Classification: B01D

Abstract:
In a gas separation membrane method of enriching the concentration of nitrogen of ambient air utilizing a membrane module having an elongated shell defining a longitudinal axis, a plurality of membranes each comprising a microporous hollow fiber defining an outer surface and a lumen surface and having a nonporous layer selectively permeable to oxygen and nitrogen deposited on at least one of the outer surface and the lumen surface, the membranes being positioned within the elongated shell to form an elongated fiber bundle having terminal potted ends to join the fibers in parallel fluid communication defining a tube side volume within the lumen surfaces and defining a shell side volume outside the nonporous layer and within the shell between the potted ends, in which a feed gas of composition of ambient air is continuously introduced into one of either the tube side volume or the shell side volume thereby causing a permeate gas flow through the membranes to a permeate volume and leaving a retentate gas of composition enriched in nitrogen relative to concentration of nitrogen of the feed gas, the improvement comprises introducing into the one of either the tube side volume or shell side volume the feed gas free of any recycled gas and feeding a sweep flow of the feed gas into the permeate volume at a rate effective to produce in a single stage separation, retentate gas having a concentration of nitrogen in the range of 80-90 vol. %.