Dual stream system and method for producing carbon dioxide

1. A system for producing carbon dioxide from a process gas, said process gas comprising a hydrocarbon, said system comprising:

a combustion subsystem configured to combust said hydrocarbon and output a combustion effluent, wherein said combustion effluent comprises carbon dioxide and water;

a first separation subsystem employing physisorption to separate a first quantity of said carbon dioxide from said combustion effluent; and

a second separation subsystem in series with said first separation subsystem and downstream of said first separation subsystem, said second separation subsystem employing chemisorption to separate a second quantity of said carbon dioxide from said combustion effluent.

2. The system of claim 1 wherein said hydrocarbon comprises at least one of methane, ethane, propane, and butane.

3. The system of claim 1 wherein said process gas is natural gas.

4. The system of claim 1 wherein said process gas further comprises carbon dioxide.

5. The system of claim 1 wherein said combustion subsystem comprises at least one of an internal combustion engine, a diesel engine modified to run on said hydrocarbon, and a turbine.

6. The system of claim 1 wherein said combustion effluent further comprises at least one of nitrogen and oxygen.

7. The system of claim 1 wherein said combustion effluent comprises at least about 5 percent by weight of said carbon dioxide.

8. The system of claim 1 wherein said combustion effluent is substantially free of said hydrocarbon.

9. The system of claim 1 wherein said combustion subsystem generates electrical energy.

10. The system of claim 1 further comprising a cooling subsystem interposed between said combustion subsystem and said first separation subsystem.

11. The system of claim 10 wherein said cooling subsystem comprises a heat exchanger thermally coupled with at least one of said first separation subsystem and said second separation subsystem.

12. The system of claim 10 wherein said cooling subsystem comprises a desiccant.

13. The system of claim 1 wherein said first separation subsystem comprises a zeolite.

14. The system of claim 1 further comprising an air moving unit configured to introduce ambient air to said combustion effluent.

15. The system of claim 14 wherein said ambient air is introduced between said first separation subsystem and said second separation subsystem.

16. The system of claim 1 wherein said combustion subsystem, said first separation subsystem and said second separation subsystem are on a mobile platform.

17. A system for producing carbon dioxide from a process gas, said process gas comprising a hydrocarbon, said system comprising:

a combustion subsystem configured to combust said hydrocarbon and output a combustion effluent, wherein said combustion effluent comprises carbon dioxide and water;

a first separation subsystem configured to separate a first quantity of said carbon dioxide from said combustion effluent; and

a second separation subsystem configured to separate a second quantity of said carbon dioxide from said combustion effluent,

wherein ambient air is introduced between said first separation subsystem and said second separation subsystem.

18. The system of claim 17 wherein said second separation subsystem is in series with said first separation subsystem and downstream of said first separation subsystem.

19. The system of claim 18 wherein said first separation subsystem comprises an adsorbent material.

20. The system of claim 19 wherein said second separation subsystem comprises a chemical sorbent.