Enhanced hydrogen recovery from effluent gas streams

An improved process for the production of a hydrogen-containing product gas consisting essentially of:

• (a) generating an effluent gas stream comprising hydrogen, carbon dioxide, carbon monoxide and water vapor;
• (b) upon cooling said effluent stream to about 350.degree. C. -400.degree. C., subjecting said effluent stream to at least a high temperature catalytic water gas shift conversion, thereby converting most of the carbon monoxide in said effluent stream to additional hydrogen and carbon dioxide;
• (c) scrubbing at least a major portion of the carbon dioxide from said thus-treated effluent stream to produce a carbon dioxide-depleted effluent stream but without essentially complete removal of carbon dioxide therefrom;
• (d) passing the thus carbon dioxide-depleted effluent stream to a pressure swing adsorption system capable of discharging a purified, hydrogen-containing product gas therefrom as a less readily adsorbable component of said effluent stream, the more readily adsorbable component thereof comprising residual carbon dioxide and other impurities present in said effluent stream, said more readily adsorbable component being removed from the pressure swing adsorption system during the countercurrent depressurization and/or purge steps of the processing cycle in each adsorbent bed of said system, said cycle comprising higher pressure adsorption with discharge of said less readily adsorbable component from the product end of the bed, cocurrent depressurization with release of void space gas from the product end of the bed, countercurrent depressurization of the bed to lower desorption pressure and/or purge with release of impurities-containing waste gas from the feed end of the bed, and repressurization to higher adsorption pressure;
• (e) compressing said waste gas removed from the pressure swing adsorption system during said countercurrent depressurization and/or purge steps;
• (f) recycling at least about 40% of said compressed waste gas to said shift conversion and/or effluent gas generation steps for additional hydrogen production, whereby said effluent gas stream is advantageously converted to the desired hydrogen-containing product stream and carbon dioxide waste gas at high hydrogen product recovery levels.