Acidic Gas Capture by Diamines

• US 20090211446A1
• Filed: 01/07/2009
• Published: 08/27/2009
• Est. Priority Date: 01/08/2008
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Rochelle, Gary, Hilliard, Marcus
• Granted Patent: US 7,938,887 B2
• Time in Patent Office: Days
• US Class Current: 95/169
• CPC Class Codes: B01D 19/0015 in contact columns containing plates, grids or other filling elements
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Compositions and methods related to the removal of acidic gas. In particular, the present disclosure relates to a composition and method for the removal of acidic gas from a gas mixture using a solvent comprising a diamine (e.g., piperazine) and carbon dioxide. One example of a method may involve a method for removing acidic gas comprising contacting a gas mixture having an acidic gas with a solvent, wherein the solvent comprises piperazine in an amount of from about 4 to about 20 moles/kg of water, and carbon dioxide in an amount of from about 0.3 to about 0.9 moles per mole of piperazine

Claims

1. A low-volatility aqueous composition comprising a diamine from about 4 to 20 moles/kg of water loaded with carbon dioxide in an amount of from about 0.3 to about 0.9 moles carbon dioxide per mole of the diamine.

2. The composition of claim 1 wherein the diamine is piperazine.

3. The composition of claim 1 wherein the diamine is a substituted piperazine chosen from methylpiperazine, dimethylpiperazine, ethylpiperazine, and diethylpiperazine.

4. The composition of claim 1 wherein the diamine is ethylenediamine.

5. The composition of claim 1 wherein the diamine is a substituted ethylenediamine chosen from methylpiperazine, dimethylpiperazine, ethylpiperazine, and diethylpiperazine.

6. A method for reducing the volatility of a diamine comprising providing a solvent that comprises a diamine in an amount of from about 4 to about 20 moles/kg of water;

and adding carbon dioxide to the solvent in an amount of from about 0.3 to about 0.9 moles per mole of diamine.

7. The method of claim 6 wherein the diamine is chosen from piperazine, a substituted piperazine, ethylenediamine, and a substituted ethylenediamine.

8. The method of claim 6 wherein carbamate ions form and reduce the volatility.

9. The method of claim 6 wherein the solvent is subjected to temperatures less than 175°

C.

10. A method for increasing the solubility of a solid diamine comprising providing a diamine to a solution of about 0.3 to 0.9 moles carbon dioxide per mole of the diamine.

11. The method of claim 10 wherein carbamate ions form.

12. The method of claim 10 wherein the diamine is chosen from piperazine, a substituted piperazine, ethylenediamine, and a substituted ethylenediamine.

13. A method comprising contacting a gas mixture having an acidic gas with a solvent, wherein the solvent comprises a diamine in an amount of from about 4 to about 20 moles/kg of water.

14. The method of claim 13 wherein the diamine is chosen from piperazine, a substituted piperazine, ethylenediamine, and a substituted ethylenediamine.

15. The method of claim 13, wherein the gaseous stream is chosen from one or more of a flue gas, a natural gas, a hydrogen gas, and a synthesis gas.

16. The method of claim 13, wherein the acidic gas is chosen from one or more of CO₂, H₂S, COS, CS₂, and mercaptans.

17. A method comprising contacting a gaseous stream with a solvent, wherein the solvent comprises a diamine in an amount of from about 4 to about 20 moles/kg of water and wherein the gaseous stream comprises an acidic gas;

and allowing the acid gas to transfer from the gaseous stream to the solvent.

18. The method of claim 17, further comprising forming a purified gaseous stream and a rich solvent stream.

19. The method of claim 17 wherein the diamine is chosen from piperazine, a substituted piperazine, ethylenediamine, and a substituted ethylenediamine.

20. The method of claim 17, further comprising routing the rich solvent stream through a stripper.

21. The method of claim 17, wherein the stripper is chosen from one or more of a simple stripper, matrix stripper, a multistage flash stripper, an exchange stripper, a multipressure stripper, and a flashing feed stripper.

22. The method of claim 17, wherein the gaseous stream is chosen from one or more of a flue gas, a natural gas, a hydrogen gas, and a synthesis gas.

23. The method of claim 17, wherein the acidic gas is chosen from one or more of CO₂, H₂S, COS, CS₂, and mercaptans.

24. The method of claim 17, further comprising recycling a solvent stream exiting the stripper.

25. The method of claim 17, wherein the stripper is operated at a temperature less than about 175°

C.

26. The method of claim 17, wherein the stripper is operated at a temperature between about 120°

C. and 160°

C.

27. A method comprising contacting a gaseous stream with a solvent in an absorber, wherein the solvent comprises piperazine or a substituted piperazine in an amount of from about 4 to about 20 moles/kg of water and wherein the gaseous stream comprises an acidic gas;

allowing the acid gas to transfer from the gaseous stream to the solvent;

forming a purified gaseous stream and a rich solvent stream;

routing the rich solvent stream through a multistage flash stripper, wherein the multistage flash stripper is operated at temperatures less than 175°

C.