Pressure swing adsorption process with improved recovery of high-purity product

A pressure swing adsorption process for the separation of a feed gas containing at least one more strongly adsorbable component and at least one less strongly adsorbable component, which process comprises the steps of:

• (1) introducing the feed gas into a feed end of a first adsorbent bed containing adsorbent material which preferentially adsorbs the more strongly adsorbable component and withdrawing from a product end of the first adsorbent bed a product gas enriched in the less strongly adsorbable component;
• (2) continuing to introduce the feed gas into the first adsorbent bed and to withdraw the product gas from the first adsorbent bed, and introducing a portion of the product gas into the product end of a second bed undergoing a repressurization step;
• (3) terminating the introduction of the feed gas into the first adsorbent bed and the withdrawal of the product gas from the first adsorbent bed, withdrawing depressurization gas from the product end thereof, and introducing the depressurization gas withdrawn from the product end thereof into the product end of a third adsorbent bed undergoing a repressurization step;
• (4) withdrawing additional depressurization gas from the product end of the first adsorbent bed and introducing the depressurization gas withdrawn therefrom into the product end of a fourth adsorbent bed undergoing a purge step;
• (5) evacuating gas from the feed end of the first adsorbent bed;
• (6) introducing a purge gas into the product end of the first adsorbent bed while continuing to evacuate gas from the feed end thereof, and introducing at least a portion of the gas evacuated from the feed end thereof into the feed end of the fourth adsorbent bed undergoing a repressurization step;
• (7) introducing a repressurization gas into the product end of the first adsorbent bed, wherein the repressurization gas is provided by depressurization gas withdrawn from the third adsorbent bed undergoing a depressurization step;
• (8) introducing additional repressurization gas into the product end of the first adsorbent bed, wherein the additional repressurization gas is provided by a portion of the product gas withdrawn from the fourth adsorbent bed undergoing a feed/product step, and introducing a purge effluent gas into the feed end of the first adsorbent bed, wherein the purge effluent gas is provided by at least a portion of the gas evacuated from the feed end of the second adsorbent bed undergoing a purge step;
• and
• (9) repeating steps (1) through (8) in a cyclic manner.

A pressure swing adsorption system for the separation of a feed gas containing at least one more strongly adsorbable component and at least one less strongly adsorbable component comprising

• (a) a plurality of adsorber vessels, each adsorber vessel having a feed end, a product end, and a bed of adsorbent material containing at least one adsorbent adapted to selectively adsorb the more strongly adsorbable component;
• (b) piping and valves adapted to introduce a feed gas into the feed end of each adsorber vessel and to withdraw a product gas enriched in the less strongly adsorbable component from the product end of each adsorber vessel;
• and
• (c) piping and valves adapted to transfer a depressurization gas enriched in the less strongly adsorbable component from the product end of a first adsorber vessel to the product end of a second adsorber vessel and to transfer a purge effluent gas from the feed end of the second adsorber vessel into the feed end of a third adsorber vessel to repressurize the third adsorber vessel.

A pressure swing adsorption system for the separation of a feed gas containing at least one more strongly adsorbable component and at least one less strongly adsorbable component comprising

• (a) four adsorber vessels, each adsorber vessel having a feed end, a product end, and a bed of adsorbent material containing at least one adsorbent adapted to selectively adsorb the more strongly adsorbable component;
• and
• (b) piping and valves adapted to
• (1) introduce a feed gas into the feed end of a first adsorber vessel and to withdraw a product gas enriched in the less strongly adsorbable component from the product end of the first adsorber vessel;
• (2) transfer a portion of the product gas enriched in the less strongly adsorbable component into the product end of a second adsorber vessel;
• (3) withdraw depressurization gas from the product end of the first adsorber vessel and introduce the withdrawn depressurization gas into the product end of a third adsorber vessel;
• (4) withdraw depressurization gas from the product end of the first adsorber vessel and introduce the withdrawn gas into the product end of a fourth adsorber vessel;
• (5) withdraw gas from the feed end of the first adsorber vessel by use of a vacuum pump or blower and discharge the withdrawn gas as waste gas;
• (6) introduce purge gas into the product end of the first adsorber vessel wherein the purge gas is provided from the second adsorber vessel while evacuating the first adsorber vessel from the feed end and introducing at least a portion of the evacuated purge effluent gas into the feed end of the fourth adsorber vessel
• (7) pressurize the first adsorber vessel adsorber vessel by introducing repressurization gas into the product end of the first adsorber vessel wherein the repressurization gas is provided by the third adsorber vessel;
• and
• (8) pressurize the first adsorber vessel by introducing product gas obtained from the fourth adsorber vessel into the product end of the first adsorber vessel and introducing purge effluent gas into the feed end of the first adsorber vessel wherein the purge effluent gas is obtained from the second adsorber vessel.