Method and apparatus for extracting and sequestering carbon dioxide

• US 20010022952A1
• Filed: 01/16/2001
• Published: 09/20/2001
• Est. Priority Date: 08/18/1998
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: United States Department of Energy
• Inventors: Caldeira, Kenneth G., Rau, Gregory H.
• Granted Patent: US 6,890,497 B2
• Time in Patent Office: Days
• US Class Current: 422/169
• CPC Class Codes: B01D 2251/402 of magnesium
• CPC Class Codes: B01D 2251/404 of calcium
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A method and apparatus to extract and sequester carbon dioxide (CO₂) from a stream or volume of gas wherein said method and apparatus hydrates CO₂, and reacts the resulting carbonic acid with carbonate. Suitable carbonates include, but are not limited to, carbonates of alkali metals and alkaline earth metals, preferably carbonates of calcium and magnesium. Waste products are metal cations and bicarbonate in solution or dehydrated metal salts, which when disposed of in a large body of water provide an effective way of sequestering CO₂ from a gaseous environment.

Claims

1. An apparatus for extracting and sequestering CO₂ from a gas stream,

comprising:

a reactor vessel;

an aqueous solution;

means for introducing said gas stream into said reactor vessel;

carbonate disposed in said reactor vessel, wherein said carbonate is of the form X(CO₃)_m wherein X is any element or combination of elements that can chemically bond with a carbonate group or its multiple, wherein at least one said element is a group IA, IIA, IIIA, IVA, IB, IIB, IIIB, IVB, VB, VIB, VIIB, or VIIIB element of the periodic table, and wherein m is a stoichiometrically determined positive integer;

means for hydrating said CO₂ with said aqueous solution to form carbonic acid, thereby resulting in a CO₂-depleted gas stream;

means for removing said CO₂-depleted gas stream from said reactor vessel;

means for reacting said carbonate with said carbonic acid to form a waste stream solution of metal ions and bicarbonate;

means for removing said waste stream solution from said reactor vessel;

a disposal site;

means for pre-treating said waste stream solution to reduce the amount of CO₂ outgassing and carbonate precipitation that may occur after said waste stream solution is released into said disposal site; and

means for releasing said pretreated waste stream solution into said disposal site.

2. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises CO₂ degassing means selected from the group consisting of means for allowing said waste stream solution to degas CO₂ to an overlying headspace whose pCO₂ is less than that of said waste stream solution;

means for purging said waste stream with a gas stream whose pCO₂ is less than that of the waste stream; and

means for applying a partial vacuum to the headspace above the waste stream.

3. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises means for diluting said waste stream solution with a second solution that is undersaturated with respect to CO₂, carbonate ions or both CO₂ and carbonate ions.

4. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises means for adding chemical additives which impede carbonate precipitation, said chemical additives being selected from the group consisting of phosphate, metals, and organic compounds, said organic compounds being selected from the group consisting of EDTA, humic substances, aromatic acids, citrate, malate, pyruvate, glycelglycerine, glycogen, arginine, glutamate, glycine, glycoprotein succinate, taurine, chondroitin sulfate, galactose, dextrose and acetate.

5. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises ion exchange means for exchanging at least a portion of the Ca²⁺ cations present in said waste solution with exchange cations which when balanced by the CO₃²⁻

anions present in the waste solution exhibit greater solubility and less propensity for precipitation than does CaCO₃.

6. The apparatus as recited in

claim 5

wherein:

said ion exchange means comprises passing said waste stream solution through an ion exchange column, with said column containing Na⁺ exchange ions.

7. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises ion exchange means for exchanging at least a portion of the CO₃²⁻

anions present in said waste solution with other anions.

8. The apparatus as recited in

claim 7

wherein:

said ion exchange means comprises passing said waste solution through an ion exchange column containing Cl⁻

anions.

9. The apparatus as recited in

claim 1

wherein:

said pre-treating means comprises means for increasing the density of said waste stream solution.

10. The apparatus as recited in

claim 1

wherein:

said disposal site comprises a large body of water that is either freshwater or seawater.

11. The apparatus as recited in

claim 10

wherein:

the pCO2 of said body of water at the point of release of waste stream solution is less than that of said waste stream solution.

12. The apparatus as recited in

claim 10

wherein:

said releasing means comprises means for releasing said waste stream solution at a depth sufficient for mixing and dilution of said waste stream solution with said body of water to occur.

13. The apparatus as recited in

claim 10

wherein:

said releasing means comprises means for releasing said waste stream solution at a depth wherein the pressure and temperature existent at said depth is sufficient to impede CO₂ outgassing to the atmosphere and carbonate precipitation.

14. The apparatus as recited in

claim 10

wherein:

said large body of water is either a sea or ocean; and

said releasing means causes said waste stream solution to be released below the pycnocline.

15. The apparatus as recited in

claim 10

wherein:

said large body of water is either a sea or ocean; and

said releasing means causes said waste stream solution to be released in the vicinity of a reef, above the pycnocline.

16. The apparatus as recited in

claim 10

wherein:

said disposal site is a body of surface seawater having sufficient constituents that serve to impede carbonate precipitation, said constituents being phosphate, Mg²⁺ ions, or phosphate and Mg²⁺ ions.

17. The apparatus as recited in

claim 10

wherein:

said disposal site is a large body of surface seawater having sufficient organic compounds that serve to at least partially impede carbonate precipitation, said organic compounds selected from the group consisting of humic substances, aromatic acids, citrate, malate, pyruvate, glycelglycerine, glycogen, arginine, glutamate, glycine, glycoprotein succinate, taurine, chondroitin sulfate, galactose, dextrose and acetate.

18. A method of extracting and sequestering CO₂ from a gas stream, said method comprising the steps of:

hydrating said CO₂ in said gas stream with an aqueous solution to form carbonic acid, thereby resulting in a CO₂-depleted gas stream;

reacting said carbonic acid with carbonate to form a waste stream solution of metal ions and bicarbonate, wherein said carbonate is of the form X(CO₃)_m wherein X is any element or combination of elements that can chemically bond with a carbonate group or its multiple, wherein at least one said element is a group IA, IIA, IIIA, IVA, IB, IIB, IIIB, IVB, VB, VIB, VIIB, or VIIIB element of the periodic table, and wherein m is a stoichiometrically determined positive integer;

pre-treating said waste stream solution to reduce the amount of CO₂ outgassing and carbonate precipitation that may occur after said waste stream solution is released into a disposal site; and

releasing said pre-treated waste stream solution into said disposal site.

19. The method as recited in

claim 18

wherein:

said pre-treating step comprises a CO₂ degassing step selected from the group consisting of allowing said waste stream solution to degas CO₂ to an overlying headsp ace whose pCO₂ is less than that of said waste stream solution;

purging said waste stream with a gas stream whose pCO₂ is less than that of the waste stream; and

applying a partial vacuum to the headspace above the waste stream.

20. The apparatus as recited in

claim 18

wherein:

said pre-treating step comprises diluting said waste stream solution with a second solution that is undersaturated with respect to CO₂, carbonate ions, or both CO₂ and carbonate ions.

21. The apparatus as recited in

claim 18

wherein:

said pre-treating step comprises adding chemical additives which impede carbonate precipitation, said chemical additives being selected from the group consisting of phosphate, metals, and organic compounds, said organic compounds being selected from the group consisting of EDTA, humic substances, aromatic acids, citrate, malate, pyruvate, glycelglycerine, glycogen, arginine, glutamate, glycine, glycoprotein succinate, taurine, chondroitin sulfate, galactose, dextrose and acetate.

22. The method as recited in

claim 18

wherein:

said pre-treating step comprises exchanging at least a portion of the Ca²⁺ cations present in said waste solution with exchange cations which when balanced by the CO₃²⁻

anions exhibit greater solubility and less propensity for precipitation than does CaCO₃.

23. The method as recited in

claim 22

wherein:

said cation exchanging step comprises passing said waste stream solution through an ion exchange column, with said column containing Na⁺ exchange ions.

24. The apparatus as recited in

claim 18

wherein:

said pre-treating step comprises exchanging at least a portion of the CO₃²⁻

anions present in said waste solution with other anions.

25. The apparatus as recited in

claim 24

wherein:

said anion exchanging step comprises passing said waste solution through an ion exchange column containing Cl⁻

anions.

26. The method as recited in

claim 18

wherein:

said pre-treating step comprises increasing the density of said waste stream solution.

27. The method as recited in

claim 18

wherein:

said disposal site comprises a body of water that is either freshwater or seawater.

28. The method as recited in

claim 27

wherein:

the pCO₂ of said body of water at the point of release of waste stream solution is less than that of said waste stream solution.

29. The method as recited in

claim 27

wherein:

said releasing step comprises releasing said waste stream solution at a depth sufficient for mixing of said waste stream solution with said body of water to occur.

30. The method as recited in

claim 27

wherein:

said releasing step comprises releasing said waste stream solution at a depth wherein the pressure and temperature existent at said depth is sufficient to impede CO₂ outgassing to the atmosphere and carbonate precipitation.

31. The method as recited in

claim 27

wherein:

said large body of water is either a sea or ocean; and

said releasing step comprises releasing said waste stream solution below the pycnocline.

32. The method as recited in

claim 27

wherein:

said large body of water is either a sea or ocean; and

said releasing step comprises releasing said waste stream solution in the vicinity of a reef, above the pycnocline.

33. The method as recited in

claim 27

wherein:

said disposal site is a body of surface seawater having sufficient constituents that serve to impede carbonate precipitation, said constituents being phosphate, Mg²⁺ ions, or phosphate and Mg²⁺ ions.

34. The method as recited in

claim 27

wherein:

said disposal site is a body of surface seawater having sufficient organic compounds that serve to impede carbonate precipitation, said organic compounds selected from the group consisting of humic substances, aromatic acids, citrate, malate, pyruvate, glycelglycerine, glycogen, arginine, glutamate, glycine, glycoprotein succinate, taurine, chondroitin sulfate, galactose, dextrose and acetate.