REMOVAL OF CARBON DIOXIDE FROM AIR

• US 20090120288A1
• Filed: 11/05/2008
• Published: 05/14/2009
• Est. Priority Date: 11/05/2007
• Status: Active Grant

• Current Assignee: Carbon Sink, Inc.
• Original Assignee: Kilimanjaro Energy, Inc.
• Inventors: Lackner, Klaus S., Wright, Allen B.
• Granted Patent: US 8,133,305 B2
• Time in Patent Office: Days
• US Class Current: 95/68
• CPC Class Codes: B01D 2253/10 Inorganic adsorbents
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/206 Ion exchange resins
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/406 Ammonia
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/0462 Temperature swing adsorption
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

The present invention provides a method and apparatus for removing a contaminant, such as carbon dioxide, from a gas stream, such as ambient air. The contaminant is removed from the gas stream by a sorbent which may be regenerated using a humidity swing, a thermal swing, or a combination thereof. The sorbent may comprise a substrate having embedded positive ions and individually mobile negative ions wherein the positive ions are sufficiently spaced to prevent interactions between the negative ions. Where a thermal swing is used, heat may be conserved by employing a heat exchanger to transfer heat from the regenerated sorbent to an amount of sorbent that is loaded with the contaminant prior to regeneration.

Claims

1. A method for removing carbon dioxide from a gas stream, comprising

placing said gas stream in contact with a substrate having a surface in which cations are embedded, wherein anions which are individually mobile are included on said surface, and wherein carbon dioxide from said gas stream becomes attached to said substrate by reacting with said anions;

and

releasing the carbon dioxide from said substrate by use of a humidity swing.

2. The method as recited in claim 1, wherein the cations are embedded have a minimum spacing to prevent said anions from interacting with each other.

3. The method as recited in claim 1, wherein said anions are hydroxide ions.

4. The method as recited in claim 1, wherein said substrate is a strong base quaternary amine resin.

5. The method as recited in claim 1, wherein said substrate is formed by sputtering a cation material onto a neutral substrate material.

6. The method as recited in claim 1, wherein said substrate includes a zeolite material.

7. The method as recited in claim 1, wherein said substrate is formed of a non-electroactive material to which positive ions are added.

8. The method as recited in claim 1, wherein said substrate includes activated alumina as a material.

9. The method as recited in claim 1, wherein said substrate includes activated magnesia as a material.

10. The method as recited in claim 1, wherein said substrate includes activated iron oxide as a material.

11. A method for removing carbon dioxide from a gas stream, comprising

placing said gas stream in contact with a substrate having a surface in which cations are embedded, wherein anions which are individually mobile are included on said surface, and wherein carbon dioxide from said gas stream becomes attached to said substrate by reacting with said anions to form bicarbonate.

12. The method as recited in claim 11, wherein the bicarbonate is released from said substrate by washing the substrate with sodium carbonate.

13. The method as recited in claim 11, wherein the bicarbonate is released from said substrate by use of a humidity swing.

14. A method for removing carbon dioxide from humid air, comprising

placing the humid air in contact with a material having a surface on which hydroxide ions form, wherein carbon dioxide from the humid air becomes attached to the surface of the material by reacting with the hydroxide ions;

and

applying a bias voltage to the material which releases the hydroxide ions and the carbon dioxide.

15. The method as recited in claim 14, wherein the hydroxide ions and the carbon dioxide react to form carbonate.

16. The method as recited in claim 14, wherein the hydroxide ions and the carbon dioxide react to form bicarbonate.

17. The method as recited in claim 14, wherein the material is comprised of positive ions embedded in a semi-noble metal.

18. The method as recited in claim 14, wherein the material is comprised of phosphor doped silicon.

19. A method for extracting a contaminant from a gas stream, comprising the steps of:

a) bringing the gas stream in contact with a sorbent which captures the contaminant from the gas stream, so as to at least partially saturate the sorbent with contaminant;

b) placing the contaminant carrying sorbent in a regeneration unit for releasing the contaminant from the sorbent and regenerate the sorbent, wherein the regeneration unit is maintained at a temperature that is higher than the temperature of the gas stream;

c) removing the regenerated sorbent from the regeneration unit; and

d) capturing heat from the regenerated sorbent as the sorbent is removed from the regeneration unit.

20. The method of claim 19, wherein the heat captured from the sorbent regeneration is used to raise the temperature of the contaminant carrying sorbent prior to the step (b) of placing the sorbent in the regeneration unit.

21. The method of claim 19, wherein the contaminant is carbon dioxide.

22. The method of claim 19, wherein the gas stream is an exhaust stream.

23. The method of claim 19, wherein the gas stream is ambient air.

24. The method of claim 19, wherein the sorbent is a liquid.

25. The method of claim 19, wherein the sorbent is a solid.

26. The method of claim 19, wherein heat is captured from the regenerated sorbent using a heat exchanger in a refrigeration cycle.

27. The method of claim 26, wherein water is employed as refrigerant in the refrigeration cycle.

28. The method of claim 27, wherein the refrigerant water is evaporated using heat exchanged from the regenerated sorbent.

29. The method of claim 28, wherein the evaporated water is condensed on the contaminant carrying sorbent.

30. The method of claim 26, wherein the heat exchanger uses carbon dioxide as a refrigerant.

31. The method of claim 26, wherein the heat exchanger utilizes a refrigerant that is isolated from having contact with the sorbent.

32. The method of claim 19, wherein the regeneration unit is maintained at an elevated temperature using heat from a source that is one from a group consisting of:

solar energy, geothermal energy, and waste heat from an industrial process.

33. An apparatus for extracting a contaminant from a gas stream using a sorbent employing a thermal swing, comprising:

a sorbent for capturing the contaminant;

a capture unit, wherein the sorbent is exposed to the gas stream and becomes at least partially saturated with the contaminant;

a regeneration unit, wherein the sorbent is exposed to elevated temperatures thereby causing the sorbent to release the contaminant according to a thermal swing; and

a heat exchanger for extracting heat retained from the sorbent in the regeneration unit.

34. The apparatus of claim 33, wherein heat extracted by the heat exchanger is used to raise the temperature of the at least partially saturated sorbent prior to placing the at least partially saturated sorbent in the regeneration unit.

35. The apparatus of claim 33, wherein the contaminant is carbon dioxide.

36. The apparatus of claim 33, wherein the gas stream is ambient air.

37. The apparatus of claim 33, wherein the sorbent is a liquid.

38. The apparatus of claim 33, wherein the sorbent is a solid.

39. The apparatus of claim 33, wherein the heat exchanger uses water as a refrigerant.

40. The apparatus of claim 33, wherein the heat exchanger uses carbon dioxide as a refrigerant.

41. The apparatus of claim 33, wherein the heat exchanger utilizes a refrigerant that is isolated from having contact with the sorbent.