VSA adsorption process with feed/vacuum advance and provide purge

Claim 1

A process for selectively separating a more strongly adsorbable component from a less strongly adsorbable component of a feed gas mixture in a plurality of adsorption beds containing an adsorbent selective for the more strongly adsorbable component, comprising the steps of: (a) introducing a feed gas mixture at elevated pressure containing said more strongly adsorbable component and said less strongly adsorbable component into an inlet of a first adsorption bed containing said adsorbent selective for the more strongly adsorbable component and adsorbing the more strongly adsorbable component on the adsorbent while the less strongly adsorbable component passes through said first bed unadsorbed as a product and continuing until the adsorption front of said more strongly adsorbable component approaches an outlet of said first bed and terminating the introduction of said feed gas mixture; (b) cocurrently depressurizing said first bed to an intermediate pressure to remove a cocurrent depressurization gas from said first bed and passing said cocurrent depressurization gas to an outlet of a bed undergoing purging of step (e); (c) further cocurrently depressurizing said first bed to a lower pressure to remove additional cocurrent depressurization gas from said first bed and passing said additional cocurrent depressurization gas to an outlet of a bed of said plurality of adsorption beds at lower pressure undergoing repressurizing of step (f) to at least partially pressure equalize the two beds, while countercurrently depressurizing said first bed by connection to a source of vacuum; (d) countercurrently evacuating said first bed under vacuum conditions to remove said more strongly adsorbable component; (e) countercurrently purging said first bed with said cocurrent depressurization gas from a bed of said plurality of adsorption beds undergoing step (b) to remove additional more strongly adsorbable component from said first bed; (f) repressurizing said first bed with ambient pressure feed gas mixture, elevated pressure feed gas mixture and said cocurrent depressurization gas from a bed of said plurality of adsorption beds undergoing the cocurrent depressurization of step (c); (g) further repressurizing said first bed with elevated pressure feed gas mixture; and (h) performing steps (a) through (g) in each of said plurality of adsorption beds in a phased sequence.