Process and system for converting carbonaceous feedstocks into energy without greenhouse gas emissions

• US 6,187,465 B1
• Filed: 11/05/1998
• Issued: 02/13/2001
• Est. Priority Date: 11/07/1997
• Status: Expired due to Term

• Current Assignee: Raven SR, LLC
• Original Assignee: Terry R. Galloway
• Inventors: Galloway, Terry R.
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US09/186,766
• Time in Patent Office: 831 Days
• Field of Search: 429/17, 429/19, 429/20
• US Class Current: 429/410
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 2250/10 Fuel cells in stationary systems, e.g. emergency power source in plant
• CPC Class Codes: H01M 2300/0074 Ion conductive at high temperature
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04164 by condensers, gas-liquid separators or filters
• CPC Class Codes: H01M 8/0612 from carbon-containing material
• CPC Class Codes: H01M 8/0631 Reactor construction specially adapted for combination reactor/fuel cell hydrogen C01B3/00; reactors for physicochemical processes B01J19/00
• CPC Class Codes: H01M 8/0675 Removal of sulfur
• CPC Class Codes: Y02B 90/10 Applications of fuel cells in buildings
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 30/00 Technologies relating to oil refining and petrochemical industry
• CPC Class Codes: Y02P 90/40 Fuel cell technologies in production processes

Abstract

The process and system of the invention converts carbonaceous feedstock from fossil fuels and other combustible materials into electrical energy without the production of unwanted greenhouse emissions. The process and system uses a combination of a gasifier to convert the carbonaceous feedstock and a greenhouse gas stream into a synthesis gas comprising carbon monoxide and hydrogen. One portion of the synthesis gas from the gasifier becomes electrochemically oxidized in an electricity-producing fuel cell into an exit gas comprising carbon dioxide and water. The latter is recycled back to the gasifier after the water is condensed out. The second portion of the synthesis gas from the gasifier is converted into useful hydrocarbon products.

Claims

1. A process for convering carbonaceous feedstock into energy without the production of greenhouse gas emissions comprising:

(a) converting a carbonaceous feedstock selected from the group consisting of coal, hydrocarbon oil, natural gas, petroleum coke, oil shale, carbonaceous-containing waste oil, carbonaceous-containing hazardous waste, carbonaceous-containing medical waste, and mixtures thereof and a greenhouse gas stream in a gasification unit to synthesis gas comprising carbon monoxide and hydrogen;

(b) electrochemically oxidizing at least a portion of said synthesis gas from said gasification unit in a first half-cell of a fuel cell to a first half-cell exit comprising carbon dioxide and water;

(c) recovering the carbon dioxide from said first half-cell exit gas to serve as at least a portion of said greenhouse gas stream in step (a); and

(d) electrochemically reducing an oxygen-containing gas in a second half-cell of said fuel cell completing the circuit and resulting in the production of electrical energy.

2. The process of claim 1 wherein said greenhouse gas stream is carbon dioxide.

3. The process of claim 1 wherein the production of electrical energy takes place in an electric power producing fossil fuel plant.

4. The process of claim 1 wherein the production of electrical energy takes place in a petroleum refinery.

5. The process of claim 1 wherein the production of electrical energy takes place in a petrochemical plant.

6. The process of claim 1 wherein said gasification unit contains a fluidized catalytic bed and operates at temperatures in the range of about 400°

to about 700°

C. (750-1300°

F.).

7. The process of claim 1 wherein a portion of said synthesis gas from said gasification unit is converted in a chemical reactor into useful hydrocarbon products.

8. The process of claim 7 wherein said chemical reactor is a Fischer-Tropsch reactor.

9. The process of claim 8 wherein a major portion of the water is condensed from said first half-cell exit gas using a condenser.

10. The process of claim 9 wherein hydrogen and at least a portion of the condensed water is passed to said gasification unit in an amount to adjust the hydrogen to carbon ratio of the combined carbonaceous feedstock and greenhouse gas stream is sufficient to result in a synthesis gas having an optimum ratio for the Fischer-Tropsch reactor.

11. The process of claim 10 wherein said synthesis gas has a hydrogen to carbon ratio in the range of about 1.75 to about 2.25.

12. The process of claim 8 wherein the amount of greenhouse gas stream is adjusted in step (a) so that the combined carbonaceous feedstock and greenhouse gas stream to said gasification unit has a hydrogen to carbon monoxide ratio in the range of about 1.75 to about 2.25.

13. The process of claim 1 wherein the oxygen-containing gas in step (d) is air and the nitrogen that remains after the electrical reduction is exited into the atmosphere.

14. The process of claim 1 wherein said first half-cell of said fuel cell contains an electrolyte surrounding a porous catalytic anode electrode.

15. The process of claim 14 wherein said second half-cell of said fuel cell contains an air electrolyte surrounding a catalytic cathode electrode.

16. The process of claim 15 wherein said first and second half-cells of said fuel cell are separated by an ionically conducting membrane that will not allow passage of components from the respective half-cells.

17. A system for converting carbonaceous feedstocks into energy without the production of greenhouse gas emissions which comprises:

(a) a gasification unit having an inlet for a carbonaceous feedstock selected from the group consisting of coal, hydrocarbon oil, natural gas, petroleum coke, oil shale, carbonaceous-containing waste oil, carbonaceous-containing hazardous waste, carbonaceous-containing medical waste, and mixtures thereof and a greenhouse gas stream, a catalyst for converting the combined feedstock into synthesis gas comprising carbon monoxide and hydrogen, and an outlet for the synthesis gas;

(b) a fuel cell for the production of electrical energy comprising a first half-cell having an inlet in fluid communication with the synthesis gas and an anode for electrochemically oxidizing synthesis gas into a first half-cell exit gas of carbon dioxide and water, a second half-cell having a cathode for electrochemically reducing an oxygen-containing gas, and a membrane separating said first and second half cells that will not allow passage of components from the respective half-cells; and

(c) a passage means for passing the carbon dioxide from said first half-cell to serve as at least a portion of the greenhouse gas stream for said gasification unit.

18. The system of claim 17 wherein the greenhouse gas stream is carbon dioxide.

19. The system of claim 17 wherein said gasification unit contains a fluidized catalytic bed and operates at temperatures in the range of about 400°

to about 700°

C.

20. The system of claim 17 wherein a chemical reactor is in fluid communication with said gasification unit to convert a portion of said synthesis gas from said gasification unit into useful hydrocarbon products.

21. The system of claim 20 wherein said chemical reactor is a Fischer-Tropsch reactor.

22. The system of claim 21 wherein a condenser is used to condense a major portion of the water from said first half-cell exit gas.

23. The system of claim 22 wherein the hydrogen and at least a portion of the condensed water is passed to said gasification unit in an amount to adjust the hydrogen to carbon ratio of the combined carbonaceous feedstock and greenhouse gas stream is sufficient to result in a synthesis gas having an optimum ratio for the Fischer-Tropsch reactor.

24. The system of claim 23 wherein said synthesis gas has a hydrogen to carbon ratio in the range of about 1.75 to about 2.25.

25. The system of claim 21 wherein the amount of greenhouse gas stream is adjusted in step (a) so that the combined carbonaceous feedstock and greenhouse gas stream to said gasification unit has a hydrogen to carbon monoxide ratio in the range of about 1.75 to about 2.25.

26. The system of claim 17 wherein the oxygen-containing gas is air and the nitrogen that remains after the ionic reduction is exited into the atmosphere.

27. The system of claim 17 wherein said first half-cell of said fuel cell contains an electrolyte surrounding a porous catytic anode electrode.

28. The system of claim 27 wherein said second half-cell of said fuel cell contains an air electrolyte surrounding a catalytic cathode electrode.

29. A process for converting carbonaceous feedstocks into energy without the production of greenhouse gas emissions comprising:

(a) converting a carbonaceous-containing organic waste feedstock and a carbon dioxide gas stream in said reactor to synthesis gas comprising carbon monoxide and hydrogen in a high temperature steam reforming reactor operating at temperatures in the range of about 400° and

about 700°

C.;

(b) converting at least a portion of said synthesis gas from said reactor to methanol;

(c) electrochemically oxidizing said methanol directly in a first half-cell of a fuel cell to a fist half-cell exit gas comprising carbon dioxide and water;

(d) recovering the carbon dioxide from said first half-cell exit gas to serve as at least a portion of said carbon dioxide gas stream in step (a); and

(e) electrochemically reducing an oxygen-containing gas in a second half-cell of said fuel cell resulting in the production of electrical energy.

30. The process of claim 29 wherein said fuel cell utilizes a pre-conversion means to convert methanol to hydrogen and carbon dioxide to permit hydrogen to feed said first half-cell of said fuel cell.

31. The process of claim 30 wherein said conversion means comprises a low temperature stream reformer operating at temperatures less than about 400°

C. and a selective oxidizer and wherein the carbon dioxide from said selective oxidizer serves as a portion of said carbon dioxide gas stream in step (a) and the hydrogen from said selective oxidizer is electrochemically oxidized in said first half-cell.

32. The process of claim 29 wherein said electrical energy is used to service buildings equipped with solar panels during the night and cloudy daytime conditions.

33. The process of claim 32 wherein hydrogen is produced in an electrolyzer to produce a balanced gas for the production of methanol, said electrolyzer energized by said electrical energy.

34. The process of claim 33 wherein oxygen produced in said electrolyzer is recycled to said second half-cell to serve as at least a portion of said oxygen-containing gas.

35. The process of claim 32 wherein said organic waste feedstock is a carbonaceous-containing municipal garbage.

36. A process for converting carbonaceous feedstocks into energy without the production of greenhouse gas emissions comprising:

(a) converting a carbonaceous-containing organic waste feedstock and a carbon dioxide gas stream in said reactor to synthesis gas comprising carbon monoxide and hydrogen in a high temperature steam reforming reactor operating at temperatures in the range of about 400° and

about 700°

C.;

(b) converting at least a portion of said synthesis gas from said reactor to methanol;

(c) electrochemically oxidizing said methanol directly in a first half-cell of a fuel cell to a first half-cell exit gas comprising carbon dioxide and water;

(d) recovering the carbon dioxide from said first half-cell exit gas to serve as at least a portion of said carbon dioxide gas stream in step (a); and

(e) electrochemically reducing an oxygen-containing gas in a second half-cell of said fuel cell resulting in the production of electrical energy.

37. The process of claim 36 wherein said fuel cell utilizes a pre-conversion means to convert methanol to hydrogen and carbon dioxide to permit hydrogen to feed said first half-cell of said fuel cell.

38. The process of claim 37 wherein said conversion means comprises a low temperature steam reformer operating at temperatures less that about 400°

C. and a selective oxidizer and wherein the carbon dioxide from said selective oxidizer serves as a portion of said carbon dioxide gas stream in step (a) and the hydrogen from said selective oxidizer is electrochemically oxidized in said first half-cell.

39. The process of claim 36 wherein said electrical energy is used to service buildings equipped with solar panels during the night and cloudy daytime conditions.

40. The process of claim 39 wherein hydrogen is produced in an electrolyzer to produce a balanced gas for the production of methanol, said electrolyzer energized by said electrical energy.

41. The process of claim 40 wherein oxygen produced in said electrolyzer is recycled to said second half-cell to serve as at least a portion of said oxygen-containing gas.

42. The process of claim 39 wherein said organic waste feedstock is a carbonaceous-containing municipal garbage.

43. A process for converting carbonaceous feedstocks into energy without the production of greenhouse gas emissions comprising:

(a) converting a carbonaceous feedstock and a carbon dioxide gas stream in a gasification unit to synthesis gas comprising carbon monoxide and hydrogen;

(b) electrochemically oxidizing at least a portion of said synthesis gas from said gasification unit in a first half-cell of a solid oxide fuel cell to a first half-cell exit gas comprising carbon dioxide and water;

(c) condensing water from said half-cell exit gas in a condenser and separating out the major portion of water from the carbon dioxide;

(d) passing the carbon dioxide from said condenser to serve as at least a portion of said greenhouse gas stream in step (b);

(e) recovering the carbon dioxide from said first half-cell exit gas to serve as at least a portion of said carbon dioxide gas steam in step (a); and

(f) electrochemically reducing an oxygen-containing gas in a second half-cell of said fuel cell resulting in the production of electrical energy.

44. The process of claim 43 wherein said feedstock is selected from the group consisting of coal, oil shale, carbonaceous-containing solid waste and mixtures thereof combined with water or carbonaceous-containing liquid waste.

45. The process of claim 43 wherein heat given off in said fuel cell is recovered in a heat recuperator.

46. The process of claim 45 wherein boiler feed water is converted to high pressure steam in said gasification unit operating at temperatures in the range of about 400°

and about 900°

C. and used to drive the third of a three stage steam turbine.

47. The process of claim 44 wherein the oxygen-containing gas is heated in said heat recuperator, expanded to drive the second stage of said three stage steam turbine, and used in step (f).

48. The process of claim 43 wherein sulfur is removed from said synthesis gas from said gasification unit in a sulfur removal unit before being electrochemically oxidized in said fuel cell.