Hydrogen recovery from gas mixts. - by controlled adsorption of impurities on carbon and desorption by evacuation

摘要

Removal of H2 from gases also contg 5 vol.% N2 and/or CO, well as CH4 (and opt. other hydrocarbons), CO2 and minor impurities, is effected by passing the mixt. through a column packed with a carbon adsorbent, so that the CO2, hydrocarbons and minor impurities are adsorbed in the part of the column near the inlet (zone 1) and the N2 and/or CO are adsorbed in the part near the outlet (zone 2), while purified H2 is withdrawn from the outlet. The adsorption phase is terminated when zone 1 extends over =30% of the height of the column but before N2 and/or CO appear at the outlet. Then, a vacuum is applied to the inlet to desorb the gases adsorbed in zone 1, which is simultaneously purged with N2 and/or CO (and residual H2) desorbed from zone 2. Process can be used to recover 99.9% pure H2 from partially purified coke-oven gas or gases from steam-reforming, catalytic reforming or cracking plants, etc. A separate purge gas system is not required.