Zero emissions sulphur recovery process with concurrent hydrogen production
Disclosed is a process for the concurrent production of hydrogen and sulphur from a H 2 S-containing gas stream, with reduced, and preferably zero, emissions. The method comprises the catalytic oxidative cracking of H 2 S so as to form H 2 and S 2 . Preferably, the oxidation is conducted using oxygen-enriched air, preferably pure oxygen. The process is conducted in a reaction chamber comprising a bifunctional catalyst material, so as to favor both the partial oxidation of H 2 S and the dissociation thereof.
1. A method for the production of hydrogen from a feedstock comprising an H 2 S-containing gas stream and an oxygen-containing gas stream, said method comprising subjecting the feedstock to catalytic oxidative cracking in the presence of a catalyst so as to form H 2 and S 2 ;
wherein said catalytic oxidative cracking forms H 2 and S 2 according to the reactions:
H 2 S H 2 +0.5 S 2 (dissociation or cracking reaction) (4)
4H 2 S+O 2 2H 2 +2H 2 O+2S 2 (H 2 formation reaction) (5).
2. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted with a molar ratio H 2 S/O 2 in the feedstock higher than 2:1.
3. A method according to claim 2 , wherein the ratio is 3:1-5:1.
4. A method according to claim 1 , wherein the oxygen-containing gas-stream comprises at least 40% oxygen.
5. A method according to claim 4 , wherein the oxygen-containing gas-stream contains oxygen having a purity of from 90%-100%.
6. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted under the influence of a single catalyst selected from the group consisting of Pt, Rh, Ru, Ir, Pd, Co, Mo, Ni, Fe, W, Cu, Cd, the corresponding sulphides, the corresponding oxides, and combinations of the foregoing.
7. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted under the influence of an oxidation catalyst and a separate cracking catalyst.
8. A method according to claim 7 , wherein the oxidation catalyst is selected from the group consisting of one or more active components selected from Group VIII metals and the cracking catalyst is selected from the group consisting of metal sulphides.
9. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted substantially autothermally at a temperature of from 900° C. to 1500° C.
10. A method according to claim 1 , comprising a further step of subjecting any formed SO 2 to hydrogenation.
11. A method according to claim 1 , wherein gas produced from the catalytic oxidative cracking is, substantially without delay, quenched to a temperature below 950° C.
12. A method according to claim 1 , wherein the H 2 S-containing gas stream and the oxygen-containing gas stream are mixed in a static mixer before entering a first catalytic bed in a catalytic oxidative cracking reaction zone or zones.
13. A method according to claim 1 , wherein catalytic oxidative cracking is followed by a Claus catalytic reaction, which is conducted employing a gas reheater, Claus catalytic reactor and sulphur condenser.
14. The method of claim 3 wherein the ratio is 4:1 to 5:1.
15. The method of claim 4 wherein the oxygen-containing gas-stream comprises at least 60% oxygen.
16. The method of claim 9 wherein the catalytic oxidative cracking is conducted substantially autothermally at a temperature from 900° C.-1200° C.
17. The method of claim 16 wherein the catalytic oxidative cracking is conducted substantially autothermally at a temperature of 1000° C.