Patent ID: 8821833

Claim:
A process for increasing the hydrogen content of a synthesis gas derived from the gasification of coal, petroleum coke or biomass, said synthesis gas comprising hydrogen and carbon oxides and having a carbon monoxide content≧45 mole % on a dry-gas basis, comprising the steps of: (i) combining the synthesis gas with steam to form a steam-enriched feed gas mixture (ii) supplying the feed gas mixture at an inlet temperature in the range 220-370° C. to a shift vessel comprising a bed of water-gas shift catalyst and passing the feed gas mixture over the water-gas shift catalyst disposed in the shift vessel to form a hydrogen-enriched shifted gas mixture containing steam at an outlet temperature greater than the inlet temperature by an exothermic water-gas shift reaction, the hydrogen-enriched shifted gas mixture containing steam having a carbon monoxide content≦10 mole % on a dry gas basis, and (iii) recovering the hydrogen-enriched shifted gas mixture containing steam leaving the bed of water-gas shift catalyst from the shift vessel at an exit temperature≦475° C., wherein 20 to 80% by volume, of the hydrogen-enriched shifted gas mixture containing steam leaving the bed of water-gas shift catalyst is recycled to the feed gas mixture to control the temperature rise across the water-gas shift catalyst from the shift vessel, wherein the hydrogen-enriched shifted gas mixture containing steam that is not recycled is subjected, without further shifting, to cooling to remove the steam and then downstream processing.