US 5,397,556 A · Process for recovery of sulfur from acid gases

Abstract

Elemental sulfur is recovered from the H.sub.2 S present in gases derived from fossil fuels by heating the H.sub.2 S with CO.sub.2 in a high-temperature reactor in the presence of a catalyst selected as one which enhances the thermal dissociation of H.sub.2 S to H.sub.2 and S.sub.2. The equilibrium of the thermal decomposition of H.sub.2 S is shifted by the equilibration of the water-gas-shift reaction so as to favor elemental sulfur formation. The primary products of the overall reaction are S.sub.2, CO, H.sub.2 and H.sub.2 O. Small amounts of COS, SO.sub.2 and CS.sub.2 may also form. Rapid quenching of the reaction mixture results in a substantial increase in the efficiency of the conversion of H.sub.2 S to elemental sulfur. Plant economy is further advanced by treating the product gases to remove byproduct carbonyl sulfide by hydrolysis, which converts the COS back to CO.sub.2 and H.sub.2 S. Unreacted CO.sub.2 and H.sub.2 S are removed from the product gas and recycled to the reactor, leaving a gas consisting chiefly of H.sub.2 and CO, which has value either as a fuel or as a chemical feedstock and recovers the hydrogen value from the H.sub.2 S.

Claims19

Dependent claims

A method for treating a gas mixture containing H.sub.2 S and CO.sub.2 to recover the H.sub.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.sub.2 S to hydrogen gas and elemental sulfur, at a temperature of at least about 700.degree. C. to thereby accelerate said decomposition and to cause a reverse water-gas shift reaction between said CO.sub.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.degree. C. or less at a quench rate of at least about 100.degree. C./second;
and
(c) condensing and recovering said elemental sulfur from said product mixture.

1 more element

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

8 more elements

Dependencies are inferred from the claim text.

Process for recovery of sulfur from acid gases

Life of this patent

Process for recovery of sulfur from acid gases

Life of this patent

Abstract

Claims19