Patent ID: 7591880

Claim:
A method of operating a fuel cell system, comprising: (1) providing a fuel inlet stream into a fuel cell stack; (2) operating the fuel cell stack to generate electricity and a hydrogen containing fuel exhaust stream; (3) separating at least a portion of hydrogen contained in the fuel exhaust stream, the step of separating comprising: (a) a first feed/purge step comprising: providing a feed gas inlet stream comprising at least a portion of the fuel exhaust stream into a first adsorbent bed; collecting a feed gas outlet stream comprising at least one separated component of the feed gas at a first output; providing a purge gas inlet stream into a second adsorbent bed; and collecting a purge gas outlet stream at a second output; (b) a first flush step, conducted after the first feed/purge step, the first flush step comprising: providing the purge gas inlet stream into the first adsorbent bed; collecting the purge gas outlet stream, which comprises at least one component of the feed gas that was trapped in a void volume of the first adsorbent bed, at the first output, wherein the first output is the same output as the first output in the first feed/purge step; providing the feed gas inlet stream into the second adsorbent bed; and collecting the feed gas outlet stream, which comprises a portion of the purge gas that was trapped in a void volume of the second bed, at the second output; (c) a second feed/purge step, conducted after the first flush step, the second feed/purge step comprising: providing the feed gas inlet stream into the second adsorbent bed; collecting the feed gas outlet stream comprising at least one separated component of the feed gas at the first output; providing the purge gas inlet stream into the first adsorbent bed; and collecting the purge gas outlet stream at the second output; and (d) a second flush step, conducted after the second feed/purge step, the second flush step comprising: providing the purge gas inlet stream into the second adsorbent bed; collecting the purge gas outlet stream, which comprises at least one component of the feed gas that was trapped in a void volume of the second adsorbent bed, at the first output; providing the feed gas inlet stream into the first adsorbent bed; and collecting a feed gas outlet stream, which comprises a portion of the purge gas that was trapped in a void volume of the first bed, at the second output; and (4) providing the hydrogen separated from the fuel exhaust stream into the fuel inlet stream.