Process for recovery of sulfur from acid gases

Claim 1

A method for treating a gas mixture containing H 2 S and CO 2 to recover the H 2 S therein as elemental sulfur, said method comprising: (a) contacting said gas mixture with a transition metal sulfide catalyst which enhances the decomposition rate of H 2 S to hydrogen gas and elemental sulfur, at a temperature of at least about 700° C. to thereby accelerate said decomposition and to cause a reverse water-gas shift reaction between said CO 2 and the hydrogen gas thus produced, thereby producing a product mixture containing elemental sulfur; (b) quenching said product mixture by cooling said product mixture to a temperature of about 650° C. or less at a quench rate of at least about 100° C./second; and (c) condensing and recovering said elemental sulfur from said product mixture.

Claim 2

A method for treating a gas mixture containing H 2 S and CO 2 to recover the H 2 S therein as elemental sulfur, said method comprising: (a) contacting said gas mixture with a transition metal sulfide catalyst which enhances the decomposition rate of H 2 S to hydrogen gas and elemental sulfur, at a temperature of at least about 700° C. to thereby accelerate said decomposition and to cause a reverse water-gas shift reaction between said CO 2 and the hydrogen gas thus produced, thereby producing a product mixture containing elemental sulfur; (b) quenching said product mixture by cooling said product mixture to a temperature of about 650° C. or less at a quench rate of at least about 100° C./second; and (c) condensing and recovering said elemental sulfur from said product mixture.

Claim 20

A method for treating a gas mixture containing H 2 S and CO 2 to recover the H 2 S therein as elemental sulfur, said method comprising: (a) contacting said gas mixture with an aqueous solution of a member selected from the group consisting of (C 1 -C 4 alkanol)-amines, di-(C 1 -C 4 alkanol)-amines, and potassium carbonate to dissolve substantially all of said H 2 S and at least a portion of said CO 2 ; (b) separating said aqueous solution from said gas mixture and stripping H 2 S and CO 2 from said aqueous solution to form a H 2 S-enriched gas mixture; (c) cooling said H 2 S-enriched gas mixture to remove by condensation at least a majority of any water vapor contained therein, thereby forming a further H 2 S-enriched gas mixture; (d) adding to said further H 2 S-enriched gas mixture sufficient CO 2 to achieve a H 2 S:CO 2 mole ratio therein of from about 0.25:1 to about 4:1; (e) contacting said further H 2 S-enriched gas mixture with a catalyst selected from the group consisting of MoS 2 , Cr 2 O 3 and WS 2 at a temperature of from about 800° C. to about 1,000° C. to thereby accelerate said decomposition and to cause a reverse water-gas shift reaction between said CO 2 and the hydrogen gas thus produced, thereby producing a product mixture containing elemental sulfur; (f) quenching said product mixture by cooling said product mixture to a temperature of about 600° C. or less at a quench rate of at least about 100° C./second; (g) condensing and recovering said elemental sulfur from said product mixture, leaving a residual gas mixture containing CO and H 2 and, as by-products, at least one member selected from the group consisting of COS and SO 2 ; (h) contacting said residual gas mixture with an aqueous potassium carbonate solution at a temperature of from about 50° C. to about 90° C. to hydrolyze any COS present in said gas mixture to CO 2 and H 2 S, and to absorb any SO 2 present in said gas mixture into said aqueous solution, leaving said CO 2 and said H 2 S in said residual gas mixture; (i) separating said residual gas mixture from said aqueous solution and recovering said CO 2 and H 2 S from said residual gas mixture; and (j) recycling said recovered CO 2 and H 2 S to step (a).

Claim 21

A method for treating a gas mixture containing H 2 S and CO 2 to recover the H 2 S therein as elemental sulfur, said method comprising: (a) contacting said gas mixture with an aqueous solution of a member selected from the group consisting of (C 1 -C 4 alkanol)-amines, di-(C 1 -C 4 alkanol)-amines, and potassium carbonate to dissolve substantially all of said H 2 S and at least a portion of said CO 2 ; (b) separating said aqueous solution from said gas mixture and stripping H 2 S and CO 2 from said aqueous solution to form a H 2 S-enriched gas mixture; (c) cooling said H 2 S-enriched gas mixture to remove by condensation at least a majority of any water vapor contained therein, thereby forming a further H 2 S-enriched gas mixture; (d) adding to said further H 2 S-enriched gas mixture sufficient CO 2 to achieve a H 2 S:CO 2 mole ratio therein of from about 0.25:1 to about 4:1; (e) contacting said further H 2 S-enriched gas mixture with a catalyst selected from the group consisting of MoS 2 , Cr 2 O 3 and WS 2 at a temperature of from about 800° C. to about 1,000° C. to thereby accelerate said decomposition and to cause a reverse water-gas shift reaction between said CO 2 and the hydrogen gas thus produced, thereby producing a product mixture containing elemental sulfur; (f) quenching said product mixture by cooling said product mixture to a temperature of about 600° C. or less at a quench rate of at least about 100° C./second; (g) condensing and recovering said elemental sulfur from said product mixture, leaving a residual gas mixture containing CO and H 2 and, as by-products, at least one member selected from the group consisting of COS and SO 2 ; (h) contacting said residual gas mixture with an aqueous potassium carbonate solution at a temperature of from about 50° C. to about 90° C. to hydrolyze any COS present in said gas mixture to CO 2 and H 2 S, and to absorb any SO 2 present in said gas mixture into said aqueous solution, leaving said CO 2 and said H 2 S in said residual gas mixture; (i) separating said residual gas mixture from said aqueous solution and recovering said CO 2 and H 2 S from said residual gas mixture; and (j) recycling said recovered CO 2 and H 2 S to step (a).