Catalytic incineration of hydrogen sulfide from gas streams

Claim 2

A process for oxidizing H 2 S to SO 2 in a feed gas comprising non-condensable gases derived from condensing geothermal steam, said non-condensable gases containing H 2 and a minor proportion of H 2 S, which process comprises: (1) contacting said feed gas, in admixture with oxygen supplied in excess of the amount necessary to convert all of said H 2 S to SO 2 , with an oxidation catalyst at a temperature between about 300° and 900° F so as to convert at least some of said H 2 S to SO 2 , said oxidation catalyst comprising a vanadium oxide and/or sulfide as the essential active component supported on a non-alkaline porous refractory oxide selected from the class consisting of silica, acid metal phosphates, acid metal arsenates, crystalline or amorphous aluminosilicate hydrogen zeolites having a silica-to-alumina ratio between about 4:1 and 100:1, and combinations thereof, said contacting converting essentially none of said H 2 S or SO 2 to SO 3 , and (2) recovering a gaseous effluent of reduced H 2 S content, but still containing essentially all of said H 2 .

Claim 3

A process as defined in claim 1 wherein at least 80% of said minor proportion of H 2 S is converted to SO 2 , and said feed gas-oxygen admixture is contacted with said catalyst at a temperature between about 500° and 900° F.

Claim 4

A process as defined in claim 2 wherein said oxygen in step (1) is supplied in the form of air.

Claim 5

A process as defined in claim 2 wherein said refractory oxide comprises hydrogen mordenite having a silica-to-alumina ratio between about 10:1 and 40:1.

Claim 6

A process as defined in claim 2 wherein said oxidation catalyst comprises between about 1 and 30 weight-percent V 2 O 5 .

Claim 7

A process as defined in claim 5 wherein said non-alkaline porous refractory oxide is selected from the class consisting of hydrogen mordenite, hydrogen erionite, hydrogen "Y" zeolite and combinations thereof.

Claim 8

A process as defined in claim 2 wherein said contacting in step (1) is carried out substantially adiabatically, and sufficient of a gaseous diluent is admixed with said feed gas to maintain said gaseous effluent of step (2) at a predetermined maximum temperature.

Claim 9

A process as defined in claim 7 wherein said maximum predetermined temperature is between about 500° and 900° F.

Claim 10

A process as defined in claim 2 wherein said feed gas is the uncondensed off-gas derived from the condensation of geothermal steam at a temperature below about 150° F.

Claim 11

A process as defined in claim 9 wherein said condensation of geothermal steam is carried out in the condenser of a geothermal power plant and the condensate from said condenser is cooled in a cooling tower to provide cooling water for said condenser, and wherein the gaseous effluent from step (2) is scrubbed with a portion of said cooling water to absorb SO 2 therefrom, and at least a portion of the resulting SO 2 -enriched scrubbing water is admixed with the cooling water in said cooling tower to maintain the pH of said cooling water at between about 5.5 and 7.5.

Claim 12

A process as defined in claim 2 wherein said non-condensable gases contain a substantial proportion of a secondary oxidizable component or components selected from the class consisting of CO and light hydrocarbons, said secondary oxidizable component remaining essentially unoxidized in step (1).

Claim 13

A process for oxidizing H 2 S to SO 2 in a feed gas comprising non-condensable gases derived from condensing geothermal steam, said non-condensable gases containing H 2 and a minor proportion of H 2 S, which process comprises: (1) converting a substantial amount of said H 2 S to elemental sulfur and then separating sulfur and a gaseous effluent substantially purified of H 2 S; (2) contacting said gaseous effluent of step (1), in admixture with oxygen supplied in excess of the amount necessary to convert all of the H 2 S remaining in said gaseous effluent to SO 2 , with an oxidation catalyst at a temperature between about 300° and 900° F so as to convert at least some of said remaining H 2 S to SO 2 , said oxidation catalyst comprising a vanadium oxide and/or sulfide as the essential active component supported on a non-alkaline porous refractory oxide selected from the class consisting of silica, acid metal phosphates, acid metal arsenates, crystalline or amorphous aluminosilicates having a silica-to-alumina ratio between about 4:1 and 100:1, and combination thereof, said contacting converting essentially none of said remaining H 2 S or SO 2 to SO 3 ; and (3) recovering a gaseous effluent of reduced H 2 S content, but still containing essentially all of said H 2 .

Claim 14

A process for oxidizing H 2 S to SO 2 in a feed gas comprising non-condensable gases derived from condensing geothermal steam, said non-condensable gases containing H 2 and a minor proportion of H 2 S, which process comprises: (1) converting a substantial amount of said H 2 S to elemental sulfur and then separating sulfur and a gaseous effluent substantially purified of H 2 S; (2) contacting said gaseous effluent of step (1), in admixture with oxygen supplied in excess of the amount necessary to convert all of the H 2 S remaining in said gaseous effluent to SO 2 , with an oxidation catalyst at a temperature between about 300° and 900° F so as to convert at least some of said remaining H 2 S to SO 2 , said oxidation catalyst comprising a vanadium oxide and/or sulfide as the essential active component supported on a non-alkaline porous refractory oxide selected from the class consisting of silica, acid metal phosphates, acid metal arsenates, crystalline or amorphous aluminosilicates having a silica-to-alumina ratio between about 4:1 and 100:1, and combination thereof, said contacting converting essentially none of said remaining H 2 S or SO 2 to SO 3 ; and (3) recovering a gaseous effluent of reduced H 2 S content, but still containing essentially all of said H 2 .

Claim 15

A process as defined in claim 12 wherein step (1) is effected by: (a) contacting said feed gas, in admixture with sufficient oxygen to convert at least about 50% of said H 2 S to elemental sulfur, with an oxidation catalyst at a temperature between about 250° and 450° F so as to convert at least about 50% of said H 2 S to elemental sulfur, said oxidation catalyst comprising a vanadium oxide and/or sulfide supported on a non-alkaline porous refractory oxide; and (b) separating free sulfur, water and said gaseous effluent substantially purified of H 2 S.

Claim 16

A process as defined in claim 13 wherein at least 80% of said remaining H 2 S is converted to SO 2 , and said contacting in step (2) is accomplished at a temperature between 500° and 900° F.

Claim 17

A process as defined in claim 14 wherein said non-alkaline, porous refractory oxide of steps (1) (a) and (2) comprises hydrogen mordenite having a silica-to-alumina ratio between about 10:1 and 40:1.

Claim 18

A process as defined in claim 14 wherein said oxidation catalyst of steps (1) (a) and (2) comprise between about 1 and 30 weight percent V 2 O 5 .

Claim 19

A process as defined in claim 16 wherein said non-alkaline porous refractory oxide of step 1(a) is selected from the class consisting of alumina, silica, silica-alumina, silica-magnesia, zirconia, silica-zirconia, titania, silicatitania, silica-zirconia-titania, hydrogen "Y" zeolite, hydrogen erionite, hydrogen mordenite and combinations thereof, and said non-alkaline porous refractory oxide of step (2) is selected from the class consisting of hydrogen "Y" zeolite, silica, hydrogen mordenite, hydrogen erionite and combinations thereof.

Claim 20

A process as defined in claim 14 wherein said contacting in step (2) is carried out substantially adiabatically, and sufficient of a gaseous diluent is admixed with said feed gas to maintain said gaseous effluent of step (3) at a predetermined maximum temperature.

Claim 21

A process as defined in claim 14 wherein said feed gas is the uncondensed off-gas derived from the condensation of geothermal steam at a temperature below about 150° F.

Claim 22

A process as defined in claim 19 wherein said condensation of geothermal steam is carried out in the condenser of a geothermal power plant and the condensate from said condenser is cooled in a cooling tower to provide cooling water for said condenser, and wherein the gaseous effluent from step (2) is scrubbed with a portion of said cooling water to absorb SO 2 therefrom, and at least a portion of the resulting SO 2 -enriched scrubbing water is admixed with the cooling water in said cooling tower to maintain the pH of said cooling water at between about 5.5 and 7.5.

Claim 23

A process as defined in claim 14 wherein said non-condensable gases contain a substantial proportion of a secondary oxidizable component or components selected from the class consisting of CO and light hydrocarbons, said secondary oxidizable component remaining essentially unoxidized in steps (1) and (2).