Integration of molten carbonate fuel cells in fischer-tropsch synthesis

Patent metadata

Field	Value
Publication number	US-9735440-B2
Application number	US-201414207711-A
Country	US
Kind code	B2
Filing date	Mar 13, 2014
Priority date	Mar 15, 2013
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

In various aspects, systems and methods are provided for integration of molten carbonate fuel cells with a Fischer-Tropsch synthesis process. The molten carbonate fuel cells can be integrated with a Fischer-Tropsch synthesis process in various manners, including providing synthesis gas for use in producing hydrocarbonaceous carbons. Additionally, integration of molten carbonate fuel cells with a Fischer-Tropsch synthesis process can facilitate further processing of vent streams or secondary product streams generated during the synthesis process.

First claim

What is claimed is:

1. A method for synthesizing hydrocarbonaceous compounds, the method comprising:
introducing a fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element associated with the anode, or a combination thereof;
introducing a cathode inlet stream comprising CO 2 and O 2 into a cathode of the molten carbonate fuel cell;
generating electricity within the molten carbonate fuel cell;
generating an anode exhaust: comprising H 2 , CO, and CO 2 , having a ratio of H 2 to CO of at least about 2.5:1, and having a CO 2 content of at least about 20 vol %, wherein an amount of the reformable fuel introduced into the anode, the internal reforming element associated with the anode, or the combination thereof, provides a reformable fuel surplus ratio of at least about 1.5;
removing water and CO 2 from at least a portion of the anode exhaust to produce an anode effluent gas stream, the anode effluent gas stream having a concentration of water that is less than half of a concentration of water in the anode exhaust, having a concentration of CO 2 that is less than half of a concentration of CO 2 in the anode exhaust, or a combination thereof, the anode effluent gas stream also having a ratio of H 2 to CO of about 2.3:1 or less; and
reacting at least a portion of the anode effluent gas stream over a non-shifting Fischer-Tropsch catalyst to produce at least one gaseous product and at least one non-gaseous product.

2. The method of claim 1 , further comprising recycling at least a portion of the gaseous product to an anode inlet, to a cathode inlet, or to a combination thereof.

3. The method of claim 2 , wherein the recycling step comprises:
removing CO 2 from the gaseous product to produce a CO 2 -concentrated stream and a separated syngas product comprising CO 2 , CO, and H 2 ; and
recycling at least a portion of the separated syngas product to the anode inlet, the cathode inlet, or a combination thereof.

4. The method of claim 3 , wherein the at least a portion of the separated syngas product is oxidized prior to the recycling step.

5. The method of claim 2 , wherein the gaseous product comprises a tail gas stream comprising one or more of (i) unreacted H 2 , (ii) unreacted CO, and (iii) C4-hydrocarbonaceous or C4-oxygenate compounds.

6. The method of claim 1 , wherein the non-shifting Fischer-Tropsch catalyst comprises Co, Rh, Ru, Ni, Zr, or a combination thereof.

7. The method of claim 1 , further comprising exposing at least a portion of the anode exhaust to a water gas shift catalyst to form a shifted anode exhaust, and then removing water and CO 2 from at least a portion of the shifted anode exhaust to form a purified H 2 stream.

8. The method of claim 7 , wherein the shifted anode exhaust has a molar ratio of H 2 to CO that is less than a molar ratio of H 2 to CO in the anode exhaust.

9. The method of claim 1 , further comprising exposing at least a portion of the anode effluent gas stream to a water gas shift catalyst to form a shifted anode effluent.

10. The method of claim 9 , wherein the shifted anode effluent has a molar ratio of H 2 to CO that is less than a molar ratio of H 2 to CO in the anode effluent gas stream.

11. The method of claim 1 , wherein the cathode inlet stream comprises exhaust from a combustion turbine.

12. The method of claim 1 , wherein the anode exhaust has a ratio of H 2 :CO of at least about 3.0:1.

13. The method of claim 1 , wherein an amount of the reformable fuel introduced into the anode, the internal reforming element associated with the anode, or the combination thereof, is at least about 75% greater than an amount of hydrogen reacted in the molten carbonate fuel cell to generate electricity.

14. The method of claim 1 , wherein a ratio of net moles of syngas in the anode exhaust to moles of CO 2 in a cathode exhaust is at least about 2.0:1.

15. The method of claim 1 , wherein a fuel utilization in the anode is about 50% or less and a CO 2 utilization in the cathode is at least about 60%.

16. The method of claim 1 , wherein the molten carbonate fuel cell is operated to generate electrical power at a current density of at least about 150 mA/cm 2 and at least about 40 mW/cm 2 of waste heat, the method further comprising performing an effective amount of an endothermic reaction to maintain a temperature differential between an anode inlet and an anode outlet of about 100° C. or less.

17. The method of claim 16 , wherein performing the endothermic reaction consumes at least about 40% of the waste heat.

18. The method of claim 1 , wherein an electrical efficiency for the molten carbonate fuel cell is between about 10% and about 40% and a total fuel cell efficiency for the fuel cell is at least about 55%.

19. The method of claim 1 , wherein the molten carbonate fuel cell is operated at a thermal ratio of about 0.25 to about 1.0.

Assignees

• Exxonmobil Res & Eng Co

Inventors

• Berlowitz Paul J
• Barckholtz Timothy Andrew
• Hershkowitz Frank
• Taylor Kevin

Classifications

• Y02E20/14

  Combined heat and power generation [CHP] · CPC title

• H01M8/14

  Fuel cells with fused electrolytes · CPC title

• H01M8/0662

  Treatment of gaseous reactants or gaseous residues, e.g. cleaning · CPC title

• H01M8/141

  the anode and the cathode being gas-permeable electrodes or electrode layers · CPC title

• Y02P20/129

  Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines · CPC title