Patent ID: 7550030

Claim:
A vacuum pressure swing adsorption (VPSA) process for the recovery of carbon dioxide from a multi-component gas mixture containing at least carbon dioxide and hydrogen in a VPSA unit containing at least one adsorption bed containing at least one CO 2 -selective adsorbent, the process comprising: feeding the multi-component gas mixture containing the at least carbon dioxide and the hydrogen to the at least one adsorption bed at a first pressure within a first pressure range for a predetermined time to produce a hydrogen-enriched stream; depressurizing the at least one adsorption bed in a first depressurization step from the first pressure range to a second pressure within a second pressure range in a same direction as or in a direction opposite to the feed flow; depressurizing the at least one adsorption bed in a second depressurization step from the second pressure range to a third pressure within a third pressure range lower than the second pressure range and in a same direction as or in a direction opposite to the feed flow; depressurizing the at least one adsorption bed in a third depressurization step from the third pressure range to a predetermined pressure range (P*) in a same direction as the feed flow or in a direction opposite the feed flow to produce a hydrogen-depleted stream; depressurizing the at least one adsorption bed in a blowdown (BD) step from the P* pressure range to a pressure close to ambient pressure in a direction in a same direction or in a direction opposite as the feed flow to produce at least a first portion of CO 2 product; evacuating the at least one adsorption bed from the pressure close to ambient to a pressure below ambient in a direction opposite or in a same direction as the feed flow to produce at least a second portion of CO 2 product; pressure equalizing the at least one adsorption bed in a first pressure equalization step in a direction opposite or in a same direction as the feed flow; further pressure equalizing the at least one adsorption bed in a second pressure equalization step in a direction opposite or in a same direction as the feed flow; and repressurizing the at least one adsorption bed in a repressurization (RP) step to the first pressure range; wherein the process is repeated cyclically.