Method and apparatus for carbon dioxide capture and release

1. A method for capturing, storing, and releasing carbon dioxide, the method including the steps of:

a) contacting a heated gaseous fuel stream with a transition metal oxide;

b) reducing the transition metal oxide to form a transition metal and carbon dioxide;

c) carburizing or partially carburizing the transition metal to form an amount of metal carbide;

d) contacting the carbon dioxide with an alkaline metal oxide or alkaline earth metal oxide to form an alkaline metal carbonate or alkaline earth metal carbonate

e) contacting the metal carbide or mixture of transition metal and metal carbide formed in step c) with air to produce a transition metal oxide and carbon dioxide; and

f) calcining the alkaline metal carbonate or alkaline earth metal carbonate of step d) to form carbon dioxide and an alkaline metal oxide or alkaline earth metal oxide.

2. The method of claim 1 , wherein the method includes a preliminary step of creating the heated gaseous fuel stream by mixing the fuel stream with air.

3. The method of claim 1 , wherein the gaseous fuel stream is heated to 500-900° C.

4. The method of claim 1 , wherein the method as described in steps a)-e) is conducted within a temperature range of 600-800° C.

5. The method of claim 1 , wherein a rate of release of carbon dioxide at steps e) and f) is controlled by a rate of contact between the transition metal carbide and air.

6. The method of claim 1 , wherein the fuel stream is contacted with a transition metal oxide and alkaline metal oxide or alkaline metal earth metal oxide substantially simultaneously.

7. The method of claim 6 , wherein the transition metal oxide and alkaline metal oxide or alkaline earth metal oxide are combined in a composite sorbent material.

8. The method of claim 7 , wherein the sorbent material includes calcium oxide (CaO) and iron ore (Fe 2 O 3 ).

9. The method of claim 1 , wherein the step of carburizing or partially carburizing the transition metal to form an amount of metal carbide comprises forming the amount of metal carbide in parallel with deposition of carbon on surfaces of at least the transition metal, and wherein the carburizing is completed or partially completed such that a maximum level of carbon deposition is below a metal/carbon ratio of 0.9.

10. The method of claim 1 , wherein the carburization step c) is only partially completed and the transition metal oxide is reduced to a mixture of metal carbide and metal or a lower oxidation level metal oxide.

11. The method of claim 1 , wherein the steps are performed by an apparatus for capturing, storing, and releasing carbon dioxide, the apparatus comprising:

a) a gas inlet for delivering a heated gaseous fuel stream;

b) a reactor for receiving a heated gaseous fuel stream, contacting the heated gaseous fuel stream with a transition metal oxide to form a transition metal, metal carbide or mixture of metal carbide and metal or a lower oxidation level metal oxide, and carbon dioxide, and contacting the carbon dioxide with an alkaline metal oxide or alkaline earth metal oxide to form an alkaline metal carbonate or alkaline earth metal carbonate;

c) an air inlet for contacting the transition metal carbide with air to facilitate production of a transition metal oxide and carbon dioxide, and calcination of the metal carbonate or alkaline earth metal carbonate to form carbon dioxide and an alkaline metal oxide or alkaline earth metal oxide; and

d) a gas outlet for discharging carbon dioxide to an external environment.