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1. (WO2014025533) GÉNÉRATION IN SITU D'IONS POLYSULFURE À L'AIDE DE SOUFRE ÉLÉMENTAIRE POUR UNE LUTTE AMÉLIORÉE CONTRE LA CORROSION, UNE GESTION DE CYANURE AMÉLIORÉE, UNE GESTION DU MERCURE AMÉLIORÉE, UNE GESTION D'ARSINE AMÉLIORÉE ET UNE PERFORMANCE ET UNE FIABILITÉ AMÉLIORÉES D'UN ÉQUIPEMENT DE RETRAIT DE GAZ ACIDE
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

WHAT IS CLAIMED IS:

1. A method for operating an acid gas treatment unit with reduced corrosion comprising:

(a) contacting an acid gas stream containing H2S with an aqueous alkaline absorbent solution to absorb the H2S into the solution to form a stream including HS- and/or S2- ions;

(b) contacting the stream containing the HS- and/or S2- ions with elemental sulfur to react the sulfur with the HS- and/or S2- ions to generate polysulfide ions, and

(c) regenerating the aqueous alkaline absorbent solution to release acid gas components from the solution.

2. The method of claim 1 wherein the aqueous alkaline absorbent solution includes at least one of alkanolamine, a metal hydroxide, a metal carbonate, a metal hydrated oxide, a metal bicarbonate, ammonium or amine cations, or a mixture thereof.

3. A method for treating a gas stream containing acidic components including H2S in an acid gas treatment unit with reduced corrosion, which comprises:

(i) contacting the acid gas stream with a lean stream of an aqueous amine absorbent solution to absorb the H2S into the solution to form a rich absorbent solution stream including HS- and/or S2- ions;

(ii) contacting the rich absorbent solution stream containing containing the HS- and/or S2- ions with elemental sulfur to react the sulfur with the HS- and/or S2- ions to generate polysulfide ions, and

(iii) regenerating the aqueous alkaline absorbent solution to release acid gas components from the solution and form a regenerated stream of lean aqueous amine absorbent.

4. The method according to anyone of the preceding claims, wherein the aqueous amine absorbent solution comprises an alkanolamine or an amine, or a mixture thereof.

5. The method according to claim 4, wherein the aqueous alkaline absorbent solution includes an alkanolamine.

6. The method according to claim 5, wherein the alkanolamine is selected from monoemanolamine (MEA), diemanolamine (DEA), triethanolamine (TEA), dipropanolamine

(DPA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), and diethylmonoethanolamine (DEAE).

7. The method according to claim 4, wherein the aqueous alkaline absorbent solution includes an amine, wherein the amine having an amine strength of at least 5%.

8. The method according to anyone of the preceding claims, wherein the acid gas stream further comprises at least one of CO2, SO2, SO3, CS2, HCN, COS and a C1-C4 thiol.

9. The method according to anyone of the preceding claims, wherein the aqueous alkaline absorbent solution is contained in an acid gas treatment unit having a metal surface, the method further comprising:

allowing the polysulfide ions to contact the metal surface of the acid gas treatment unit to form metal-polysulfide on the metal surface, thereby ameliorating corrosion of the unit.

10. The method according to anyone of the preceding claims, wherein the acid gas stream includes mercury, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the mercury to form mercury sulfide; and

filtering the mercury sulfide from the aqueous alkaline absorbent solution stream.

11. The method according to anyone of claims 1-10, wherein the acid gas stream includes cyanide ions, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the cyanide ions to form thiocyanate ions, thereby reducing the concentration of the cyanide ions in the acid gas stream and creating thiocyanate.

12. The method according to anyone of claims 1-10, wherein the acid gas stream includes arsine, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the arsine to form arsenic trisulfide; and

filtering the arsenic trisulfide from the aqueous alkaline absorbent solution.

13. The method according to anyone of the preceding claims, wherein the stream containing the HS- and/or S2- ions which is contacted with the elemental sulfur to the process to generate polysulfide ions is the stream resulting from the step of contacting the acid gas stream with the aqueous alkaline absorbent solution.

14. An acid gas treatment system in which polysulfide ions are generated in a stream of an aqueous alkaline absorbent solution, comprising:

(i) an absorber tower in communication with a source of a lean stream of the aqueous alkaline absorbent solution and with a stream of acid gas containing H2S to contact the acid gas stream with the lean stream of the aqueous alkaline absorbent solution to form a rich stream of the aqueous alkaline absorbent solution containing HS- and/or S2- ions;

(ii) a source of elemental sulfur to be introduced the rich stream of the aqueous alkaline absorbent solution to react with HS- and/or S2- ions to generate polysulfide ions.

15. The system of claim 14, wherein the aqueous alkaline absorbent solution includes at least one alkanolamine, or an amine, or a mixture thereof.

16. The system of claim 15, wherein the aqueous alkaline absorbent solution includes an alkanolamine.

17. The system of claim 16, wherein the alkanolamines is selected from monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), dipropanolamine (DPA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), and diemylmonoethanolamine (DEAE).

18. The system according to anyone of claims 14-17, wherein the source of elemental sulfur is provided as solid elemental sulfur applied upon a screen in contact with the process stream.

19. The system according to anyone of claims 14-18, wherein the acid gas stream further comprises mercury, the system further including a separation device located down stream from the source of elemental sulfur to remove mercury sulfide formed by a reaction between the mercury with the polysulfide ions.

20. The system according to anyone of claims 14-18, wherein the acid gas stream further comprises arsine, the system further including a separation device located downstream from the source of elemental sulfur to remove arsenic trisulfide formed by a reaction between arsine with the polysulfide ions.

AMENDED CLAIMS

received by the International Bureau on 18 December 2013 (18.12.13)

Claims:

1. A method for operating an acid gas treatment unit with reduced corrosion comprising:

(a) contacting an acid gas stream containing H2S with an aqueous alkaline absorbent solution to absorb the H2S into the solution to form a stream including HS- and/or S2- ions;

(b) contacting the stream containing the HS- and/or S2- ions with elemental sulfur to react the sulfur with the HS- and/or S2- ions to generate polysulfide ions, and

(c) regenerating the aqueous alkaline absorbent solution to release acid gas components from the solution while operating with an accumulation of heat stable satis exceeding 3 wt. percent.

2. The method of claim 1 wherein the aqueous alkaline absorbent solution includes at least one of alkanolamine, a metal hydroxide, a metal carbonate, a metal hydrated oxide, a metal bicarbonate, ammonium or amine cations, or a mixture thereof.

3. The method according to anyone of the preceding claims, wherein the aqueous amine absorbent solution comprises an alkanolamine or an amine, or a mixture thereof.

4. The method according to claim 3, wherein the aqueous alkaline absorbent solution includes an alkanolamine.

5. The method according to claim 4, wherein the alkanolamine is selected from monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), dipropanolamine (DPA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), and diethylmonoethanolamine (DEAE).

6. The method according .to anyone of the preceding claims, wherein the acid gas stream comprises H2S and at least one of C02, S02, S03, CS2, HCN, COS and a C1-C4 thiol.

7. The method according to anyone of the preceding claims, wherein the aqueous alkaline absorbent solution is contained in an acid gas treatment unit having a carbon steel surface, me method further comprising:

allowing the polysulfide ions to contact the metal surface of the acid gas treatment unit to form iron -polysulfide on the steel surface, thereby ameliorating corrosion of the unit.

8 The method according to anyone of the preceding claims, wherein the acide gas stream includes mercury, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the mercury to form mercury sulfide; and

filtering the mercury sulfide from the aqueous alkaline absorbent solution stream.

9. The method according to anyone of claims 1-8, wherein the acid gas stream includes cyanide ions, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the cyanide ions to form thiocyanate ions, thereby reducing the concentration of the cyanide ions in the acid gas stream and creating thiocyanate.

10. The method according to anyone of claims 1-9, wherein the acid gas stream includes arsine, the method further comprising:

allowing the polysulfide ions to remain in the aqueous alkaline absorbent solution to react with the arsine to form arsenic trisulfide; and

filtering the arsenic trisulfide from the aqueous alkaline absorbent solution.

11. The method according to anyone of the preceding claims, wherein the stream containing the HS- and/or S2- ions which is contacted with the elemental sulfur to the process to generate polysulfide ions is the stream resulting from the step of contacting the acid gas stream with the aqueous alkaline absorbent solution.

12. The method of anyone of the preceding claims in which the aqueous alkaline absorbent solution includes monoethanolamine (MEA) at a concentration exceeding 25 wt. percent of the solution.

13. The method of anyone of the claims 1 to 11 in which the aqueous alkaline absorbent solution includes diethanolamine (DEA) at a concentration exceeding 25 wt. percent of the solution.

14. The method of anyone of the preceding claims in which the aqueous alkaline absorbent solution includes an alkanolamine selected from monoethanolamine (MEA) or diethanolamine (DEA) and the process stream including HS- and/or S2- ions contains 0.5-0.7 moles acid gas / mole alkanolamine.

Statement under 19(1)

D1, EP 102,712 (Foroulis), discloses the use of ammonium or alkali metal sulfides or mixtures in combination with elemental sulfur forms polysulfides which act as corrosion inhibitors in amine solutions in acid gas treatment systems. There is no suggestion that the polysulfides may be generated by the addition of elemental sulfur without the sulfide. There is no suggestion that this method would be applicable when operating with high levels of heat stable salts exceeding 3 percent.

D2, US 4,959,177 (Schutt), discloses a method for reducing the incidence of stress corrosion cracking of welds in gas treatment units using alkanolamines treating solutions. The described method comprises adding an effective amount of elemental sulfur or a compound yielding sulfide ions to the aqueous alkanolamine solution (col. 3, II. 15-44; col; 4, II. 45-50). There is no suggestion that this method would be applicable when operating with high levels of heat stable salts exceeding 3 percent.

The subject matter of revised claim 1 is therefore seen to be patentable over D1 and 02.