Adsorption process to recover hydrogen from low pressure feeds

A process for selectively separating at least one more strongly adsorbable component(s) selected from the group consisting of nitrogen, methane, carbon monoxide, carbon dioxide and mixtures thereof from hydrogen in a hydrogen-containing feed gas mixture in a plurality of adsorption beds containing an adsorbent selective for the more strongly adsorbable component(s), comprising the steps of:

• (a) introducing a hydrogen-containing feed gas mixture at elevated pressure containing said at least one more strongly adsorbable component(s) and said hydrogen into an inlet of a first adsorption bed containing said adsorbent selective for said at least one more strongly adsorbable component(s) and adsorbing a more strongly adsorbable component(s) on the adsorbent while the hydrogen passes through said first bed unadsorbed until the adsorption front of the more strongly adsorbable component(s) approaches an outlet of said first bed and terminating the introduction of said hydrogen-containing feed gas mixture;
• (b) cocurrently depressurizing said first bed to a lower pressure to remove gas from said first bed and passing said gas to an outlet of another bed of said plurality of adsorption beds at lower pressure to countercurrently purge said more strongly adsorbable component(s) from the other bed under the influence of a vacuum, while simultaneously countercurrently venting said first bed;
• (c) countercurrently evacuating said first bed under vacuum conditions to further remove said more strongly adsorbable component(s) at a lowest pressure;
• (d) countercurrently purging said first bed with cocurrently depressurizing gas from another bed of said plurality of adsorption beds undergoing step (b) to remove additional more strongly adsorbable component from said first bed under the influence of a vacuum;
• (e) repressurizing said first bed;
• and
• (f) performing steps (a) through (e) in each of said plurality of adsorption beds in a phased sequence.

A process for selectively separating at least one more strongly adsorbable component(s) selected from the group consisting of nitrogen, methane, carbon monoxide, carbon dioxide and mixtures thereof from hydrogen in a hydrogen-containing feed gas mixture in six parallel connected adsorption beds containing an adsorbent(s) selective for the more strongly adsorbable component(s), comprising the steps of:

• (a) introducing a hydrogen-containing feed gas mixture at elevated pressure in the range of 5 to 125 psig containing said at least one more strongly adsorbable component(s) and said hydrogen into an inlet of a first adsorption bed containing said adsorbent(s) selective for said at least one more strongly adsorbable component(s) and adsorbing a more strongly adsorbable component(s) on the adsorbent while the hydrogen passes through said first bed unadsorbed as a product of at least 95% purity until the adsorption front of the more strongly adsorbable component(s) approaches an outlet of said first bed and terminating the introduction of said hydrogen-containing feed gas mixture;
• (b) initially cocurrently depressurizing said first bed to a lower pressure to remove gas from said first bed and passing said gas to an outlet of another bed of said six adsorption beds at lower pressure to equalize the pressure in the two adsorption beds;
• (c) further cocurrently depressurizing said first bed to a lower pressure to remove gas from said first bed and passing said gas directly to an outlet of a third bed of said six adsorption beds at a lowest pressure to countercurrently purge said more strongly adsorbable component(s) from said third bed under the influence of a vacuum, while simultaneously countercurrently venting said first bed;
• (d) countercurrently evacuating said first bed under vacuum conditions to further remove said more strongly adsorbable component(s) to a lowest pressure in the range of 500 to 80 Torr absolute;
• (e) countercurrently purging said first bed with cocurrently depressurizing gas from another bed of said plurality of adsorption beds undergoing step (c) to remove additional more strongly adsorbable component(s) from said first bed under the influence of a vacuum;
• (f) initially repressurizing said first bed by passing gas from a bed undergoing step (b) initial cocurrent depressurization to pressure equalize the two beds;
• (g) repressurizing said first bed with hydrogen-containing feed gas mixture;
• and
• (h) performing steps (a) through (g) in each of said six adsorption beds in a phased sequence.