Carbon dioxide recovery

1. A method for recovering carbon dioxide (CO 2 ), comprising:

receiving, in a CO 2 separation system, a gas mixture from a power plant, wherein the gas mixture comprises CO 2 , and the CO 2 separation system comprises:

a rotating freezer/melter having a freezing zone, a melting zone, and a rotor;

a CO 2 separation device downstream of the freezing zone of the rotating freezer/melter; and

a compressor downstream of the CO 2 separation device;

flowing the gas mixture through the rotor while the rotor is in the freezing zone;

capturing solid CO 2 from the gas mixture on the rotor while the rotor is in the freezing zone;

melting the solid CO 2 captured on the rotor while the rotor is in the melting zone, thereby forming liquid CO 2 ;

flowing the liquid CO 2 through the rotor while the rotor is in the melting zone;

maintaining the melting zone at a higher pressure than the freezing zone to preserve the melted CO 2 in a liquid state as it exits the melting zone;

routing the remaining gas mixture out of the freezing zone and into the CO 2 separation device;

recovering residual CO 2 from the remaining gas mixture using the CO 2 separation device;

pressurizing the residual CO 2 using the compressor to produce a pressurized CO 2 vapor stream; and

using the pressurized CO 2 vapor stream to melt the solid CO 2 within the melting zone of the rotating freezer/melter.

2. The method of claim 1 , further comprising pumping at least a portion of the melted CO 2 using a pump disposed downstream of the rotating freezer/melter, thereby generating pressurized liquid CO 2 .

3. The method of claim 2 , further comprising converting the pressurized liquid CO 2 to a vapor CO 2 stream using a refrigeration load.

4. The method of claim 3 , further comprising using the refrigeration load to chill cooling water for the power plant.

5. The method of claim 3 , further comprising using the vapor CO 2 stream in enhanced oil recovery (EOR) operations.

6. The method of claim 1 , further using a dehydration system to remove H 2 O from the gas mixture prior to receiving the gas mixture in the CO 2 separation system.

7. The method of claim 1 , wherein the CO 2 separation system further comprises a heat exchanger and a first expander.

8. The method of claim 7 , further comprising, prior to flowing the gas mixture through the rotor:

cooling the gas mixture using the heat exchanger; and

flowing the gas mixture through the first expander, thereby forming solid CO 2 from at least a portion of the CO 2 in the gas mixture.

9. The method of claim 8 , wherein the gas mixture is cooled via indirect heat exchange.

10. The method of claim 8 , further comprising flowing the remaining gas mixture to the heat exchanger prior to routing the remaining gas mixture to the CO 2 separation device, wherein the heat exchanger cools the gas mixture via indirect exchange with the remaining gas mixture.

11. The method of claim 8 , wherein the first expander lowers the pressure and temperature of the gas mixture thereby freezing at least a portion of CO 2 within the gas mixture to pure solid CO 2 .

12. The method of claim 1 , wherein the CO 2 separation device recovers the residual CO 2 from the remaining gas mixture via a potassium carbonate separation process.

13. The method of claim 1 , further comprising:

recycling a portion of the liquid CO 2 to the melting zone of the rotating freezer/melter; and

using the portion of the liquid CO 2 to melt the solid CO 2 within the melting zone.

14. The method of claim 1 , wherein an exhaust gas from the power plant provides the gas mixture.

15. The method of claim 1 , comprising producing power via the power plant.

16. The method of claim 15 , wherein producing power via the power plant comprises:

providing mechanical energy via an expander turbine using energy extracted from the gas mixture after combustion of the gas mixture in a combustor; and

generating electricity via a generator using the mechanical energy provided by the expander turbine.

17. The method of claim 15 , wherein producing the power via the power plant comprises:

providing mechanical energy via an expander turbine using energy extracted from the gas mixture after combustion of the gas mixture in a combustor;

generating steam via a heat recovery steam generator (HRSG) by heating a boiler with an exhaust stream from the expander turbine;

providing mechanical energy via a steam turbine using energy extracted from the steam generated by the HRSG; and

generating electricity via a generator using the mechanical energy provided by the expander turbine and the steam turbine.

18. The method of claim 1 , further comprising recycling a portion of the gas mixture to the power plant.