Process for producing hydrogen from synthesis gas containing COS

Claim 1

In the process of desulfurizing, shifting and decarbonizing a contaminated synthesis gas stream, obtained by gasification of coal or heavy hydrocarbon oil, to obtain a purified hydrogen rich stream, said synthesis gas stream containing among contaminants therein H 2 S, COS, CO and CO 2 ; the improvement which comprises: effecting such desulfurizing with organic solvent in two physical absorption stages, wherein said synthesis gas stream in the first absorption stage is contacted with organic liquid solvent under conditions effecting physical absorption therein of the major portion of the H 2 S in said stream but not more than up to about 65% of the COS; introducing the gaseous effluent from the first absorption stage containing unremoved COS to shift reaction with water over sulfide-resistant shift catalyst to convert CO therein to CO 2 and hydrogen, while hydrolyzing the COS therein to form H 2 S; subjecting the products of said shift reaction to the second absorption stage for removal of essentially all of the contained residual sulfide gases therefrom by physical absorption in an organic solvent; and utilizing the rich sulfide-containing solvent from said second absorption stage for said contacting of the synthesis gas stream in the first absorption stage.

Claim 10

The method of removing from a hydrogen gas feed stream CO 2 and gaseous sulfides including H 2 S and COS therein contained which comprises the steps of (a) subjecting such stream to physical absorption by an organic liquid solvent for gaseous sulfides under conditions effective to remove at least the bulk of the H 2 S and only part of the COS therein; (b) subjecting the thus partially desulfurized gas to a gas shift reaction with water over sulfur-resistant shift catalyst to convert CO therein to CO 2 while hydrolyzing the COS to form CO 2 and H 2 S; (c) cooling the gaseous products obtained from step (b) and subjecting the same to a second physical absorption by organic liquid solvent for gaseous sulfides to remove essentially all of the residual gaseous sulfides therefrom; and returning the rich solvent liquid containing said removed residual sulfides for use in step (a); (d) withdrawing the desulfurized gas effluent from step (c) and subjecting the same to contact with liquid organic solvent at sub-ambient temperatures to remove CO 2 therefrom and recovering a purified hydrogen-rich stream essentially free of gaseous sulfides; (e) withdrawing the rich solvent containing dissolved CO 2 from step (d) and utilizing a minor portion thereof as the solvent for removal of gaseous sulfides in step (c); (f) flashing and/or stripping CO 2 from the major portion of the rich solvent from step (e) and utilizing the stripped solvent as part of the liquid solvent for absorption of CO 2 in step (d); (g) stripping H 2 S from the rich solvent liquor recovered in step (a) to obtain a gaseous effluent of sufficiently high sulfide content enabling recovery of sulfur values therefrom in conventional Claus operation; and (h) utilizing at least part of the stripped lean solvent from step (g) for another part of liquid organic solvent for absorption of CO 2 in step (d).

Claim 11

The method of removing from a hydrogen gas feed stream CO 2 and gaseous sulfides including H 2 S and COS therein contained which comprises the steps of (a) subjecting such stream to physical absorption by an organic liquid solvent for gaseous sulfides under conditions effective to remove at least the bulk of the H 2 S and only part of the COS therein; (b) subjecting the thus partially desulfurized gas to a gas shift reaction with water over sulfur-resistant shift catalyst to convert CO therein to CO 2 while hydrolyzing the COS to form CO 2 and H 2 S; (c) cooling the gaseous products obtained from step (b) and subjecting the same to a second physical absorption by organic liquid solvent for gaseous sulfides to remove essentially all of the residual gaseous sulfides therefrom; and returning the rich solvent liquid containing said removed residual sulfides for use in step (a); (d) withdrawing the desulfurized gas effluent from step (c) and subjecting the same to contact with liquid organic solvent at sub-ambient temperatures to remove CO 2 therefrom and recovering a purified hydrogen-rich stream essentially free of gaseous sulfides; (e) withdrawing the rich solvent containing dissolved CO 2 from step (d) and utilizing a minor portion thereof as the solvent for removal of gaseous sulfides in step (c); (f) flashing and/or stripping CO 2 from the major portion of the rich solvent from step (e) and utilizing the stripped solvent as part of the liquid solvent for absorption of CO 2 in step (d); (g) stripping H 2 S from the rich solvent liquor recovered in step (a) to obtain a gaseous effluent of sufficiently high sulfide content enabling recovery of sulfur values therefrom in conventional Claus operation; and (h) utilizing at least part of the stripped lean solvent from step (g) for another part of liquid organic solvent for absorption of CO 2 in step (d).