CO2 separation from low-temperature flue gases

• US 7,842,126 B1
• Filed: 09/30/2008
• Issued: 11/30/2010
• Est. Priority Date: 09/30/2008
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Allen, Douglas, Hedges, Sheila, Soong, Yee, Dilmore, Robert
• Primary Examiner(s): Lawrence; Frank M
• Application Number:
  US12/241,430
• Time in Patent Office: 791 Days
• Field of Search: 951/89, 95195-197, 952/05, 952/36, 423/220, 423/225, 423/226, 423/228, 423/229, 423/232
• US Class Current: 95/195
• CPC Class Codes: B01D 2251/302 of lithium
• CPC Class Codes: B01D 2251/304 of sodium
• CPC Class Codes: B01D 2251/306 of potassium
• CPC Class Codes: B01D 2251/402 of magnesium
• CPC Class Codes: B01D 2251/404 of calcium
• CPC Class Codes: B01D 2251/80 Organic bases or salts
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01D 53/78 with gas-liquid contact
• CPC Class Codes: B01D 53/80 Semi-solid phase processes, i.e. by using slurries
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Two methods are provide for the separation of carbon dioxide from the flue gases. The first method utilizes a phase-separating moiety dissolved in an aqueous solution of a basic moiety to capture carbon dioxide. The second method utilizes a phase-separating moiety as a suspended solid in an aqueous solution of a basic moiety to capture carbon dioxide. The first method takes advantage of the surface-independent nature of the CO₂ absorption reactions in a homogeneous aqueous system. The second method also provides permanent sequestration of the carbon dioxide. Both methods incorporate the kinetic rate enhancements of amine-based scrubbing while eliminating the need to heat the entire amine solution (80% water) in order to regenerate and release CO₂. Both methods also take advantage of the low-regeneration temperatures of CO₂-bearing mineral systems such as Na₂CO₃/NaHCO₃ and K₂CO₃/KHCO₃.

Claims

1. A method for removing carbon dioxide from a fluid, the method comprising:

a) forming an aqueous mixture of a phase-separating reactive reagent and a basic moiety;

b) contacting the fluid to the mixture for a time and at a temperature sufficient to form bicarbonate product;

c) allow the mixture to become supersaturated with the product; and

d) separating the product from the mixture as a nonamorphous precipitate.

2. The method as recited in claim 1, wherein the phase-separating reactive reagent is a metal carbonate.

3. The method as recited in claim 2, wherein the metal in the metal carbonate is an alkali selected from group consisting of potassium, sodium, lithium, and combinations thereof.

4. The method recited in claim 1, further comprising:

e) using the basic moiety to catalyze the regeneration of the phase-separating reactive reagent.

5. The method as recited in claim 4, wherein the mixture is heated.

6. The method as described in claim 5, wherein the product is an alkali bicarbonate in crystalline form.

7. The method as recited in claim 5, wherein the product is an alkali bicarbonate in semi-crystalline form.

8. The method as recited in claim 5, wherein a portion of said product remains suspended in the aqueous mixture.

9. The method as recited in claim 5, further comprising heating the precipitate for a time and at a temperature sufficient to convert the solid to a regenerated phase separating reagent and carbon dioxide gas.

10. The method as recited in claim 9, wherein the regenerated phase separating reagent and said phase separating reagent are the same chemical compound.

11. A method for the removal of carbon dioxide from fluid, the method comprising:

suspending a phase-separating solid agent within an aqueous solution of a basic moiety to create a mixture and;

contacting said mixture with the fluid for a time and at a temperature sufficient to form solid carbonates of the agent.

12. The method as described in claim 11, where the phase-separating solid reactive agent comprises an alkaline earth metal oxide.

13. The method as recited in claim 12, wherein the alkaline earth metal oxide is calcium oxide or magnesium oxide, or combinations thereof.

14. The method as described in claim 11, wherein the phase-separating solid agent comprises an alkaline earth metal hydroxide.

15. The method as recited in claim 11, wherein the phase-separating solid reactive agent has a particle size range from about 1 micron to 2000 microns.

16. The method recited in claim 11, where the basic moiety is an amine or a hindered amine.

17. The method as recited in claim 11, wherein the carbonates include bicarbonates.

18. The method as recited in claim 17, where some portion of the carbonates are insoluble, and where some portion of the bicarbonates comprise solids, and further comprising removing the some portion of the carbonates and the some portion of the bicarbonates from the aqueous solution.

19. The method as recited in claim 11 further comprising chemically regenerating the basic moiety and maintaining the phase-separating solid agent in solid form.