Hydrogen recovery by pressure swing adsorption integrated with adsorbent membranes

Claim 1

In a pressure swing adsorption process which separates a pressure swing adsorption feed gas mixture comprising one or more primary components and one or more secondary components into a product stream enriched in the primary components and one or more reject streams enriched in the secondary components, wherein the secondary components are more strongly adsorbed on an adsorbent material and the primary components are less strongly adsorbed on the adsorbent material, and wherein the pressure swing adsorption process includes at least the steps of (A) passing the pressure swing adsorption feed gas mixture through an adsorption zone at a first pressure wherein the secondary components are selectively adsorbed on the adsorbent material therein and a product stream enriched in primary components is withdrawn therefrom; (B) isolating the adsorption zone and depressurizing the zone by withdrawing therefrom desorbed and void space gas as a stream of depressurization gas; and (C) purging the resulting depressurized adsorption zone of step (b) with a purge gas stream and withdrawing therefrom a purge gas effluent; a method for improving the recovery of the primary components in the product stream which comprises: (1) selectively segregating either the depressurization gas or the purge effluent gas by (1a) dividing the depressurization gas into at least a first portion obtained during a first period of the depressurization step and a second portion obtained during a second period of the depressurization step; or (1b) dividing the purge effluent gas into at least a first portion obtained during a first period of the purge step and a second portion obtained during a second period of the purge step; (2) passing either the first portion of depressurization gas or the second portion of the purge effluent gas as a membrane feed gas through a membrane separation zone having a permeable adsorbent membrane which divides the zone into a feed side and a permeate side, wherein the membrane feed gas passes through the feed side of the membrane separation zone and portions of the secondary components selectively adsorb and permeate through the membrane to the permeate side; (3) withdrawing from the permeate side of the membrane separation zone a permeate stream which is further enriched in the secondary components and withdrawing from the feed side of the membrane separation zone a nonpermeate stream which is depleted in the secondary components and enriched in the primary components; and (4) combining the nonpermeate stream with the pressure swing adsorption feed gas mixture and passing the resulting combined gas stream through the adsorption zone.