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CN-122029650-A - Improving reforming flux of molten carbonate fuel cells

CN122029650ACN 122029650 ACN122029650 ACN 122029650ACN-122029650-A

Abstract

A system and method for operating a molten carbonate fuel cell is provided to produce an increased amount of H 2 in the anode effluent while maintaining the cell operating within a conventional operating range, such as a temperature difference between the cathode input stream and the cathode effluent of 35 ℃ or greater, and a temperature of the cathode effluent higher than the cathode input stream. The temperature difference between the cathode input stream and the cathode output stream is achieved while still producing excess hydrogen, in part due to the steps of a) feeding an input stream containing hydrocarbons and/or reformable fuel to an external reformer, b) reforming 20 vol.% or more of the hydrocarbons and/or reformable fuel in the external reformer, and then c) feeding the partially reformed input stream to a fuel cell or fuel cell stack for further reforming in reforming elements in the anode and/or fuel cell stack.

Inventors

  • A. I. Skolidas
  • JOHNSON GARRICK ROSS
  • SUTTON CLAY R.
  • L.Han

Assignees

  • 埃克森美孚技术与工程公司

Dates

Publication Date
20260512
Application Date
20241017
Priority Date
20231018

Claims (15)

  1. 1. A method of operating a molten carbonate fuel cell includes heating an input stream comprising 20% or more by volume of hydrocarbons, reformable fuel, or a combination thereof by heat exchange with at least a portion of an anode effluent, reforming 15% or more of the input stream, reformable fuel, or a combination thereof to form a partially reformed input stream comprising 15% or more by volume of hydrocarbons, reformable fuel, or a combination thereof, 15% or more by volume of H 2 content, and 5.0% or more by volume of carbon oxides, heating the partially reformed input stream to form an anode input stream comprising 550 ℃ or more by volume of the anode input stream, feeding the anode input stream to an anode of one or more molten carbonate fuel cells, an internal reforming element associated with the anode, or a combination thereof, feeding a cathode input stream comprising 4.0% or more by volume of CO 2 and a cathode input temperature of 550 ℃ or more to one or more molten carbonate fuel cells, operating at an average current density of 100mA/cm or more, an anode input temperature of 53.65% or more by volume of the anode input stream, and a cathode input temperature of 53% or more of the anode input fuel cells, and a cathode input stream comprising 53% or more by volume of the anode input fuel cell, and a cathode input fuel of 53% or more by volume of the anode input to the anode input stream at a cathode temperature of 550% or more by volume of the anode input fuel cell.
  2. 2. The method of claim 1, wherein the hydrocarbon, reformable fuel, or combination thereof comprises at least one of methane and natural gas.
  3. 3. The method of any of the above claims, wherein the anode input stream comprises 0.5% or more CO by volume, or wherein the anode input stream comprises 5.0% or more CO 2 , or a combination thereof.
  4. 4. The method of any of the above claims, wherein the temperature of the cathode effluent is 50 ℃ or greater than the cathode input temperature.
  5. 5. The method of any of the above claims, wherein at least a portion of reforming is performed during heating of the input stream by heat exchange with the anode effluent, or wherein heating of the partially reformed input stream is performed at least partially during reforming of the input stream, or a combination thereof.
  6. 6. The method of any of the above claims, wherein the anode effluent temperature is 35 ℃ or greater than the anode input temperature.
  7. 7. The method of any of the above claims, wherein the partially reformed input stream comprises 20% by volume or more hydrocarbons, reformable fuel, or a combination thereof.
  8. 8. The method of any of the above claims, wherein the partially reformed input stream comprises 20% or greater H 2 by volume, or the anode effluent comprises 25% or greater H 2 by volume, or a combination thereof.
  9. 9. The method of any of the above claims, further comprising heating a CO 2 -containing stream in a heater to form the cathode input stream, wherein heating the partially reformed input stream is performed in the heater, and optionally further comprising preheating the CO 2 -containing stream by heat exchange with at least a portion of the cathode effluent.
  10. 10. The method of any one of the above claims, wherein the one or more molten carbonate fuel cells comprise a fuel cell stack.
  11. 11. The method of any one of the above claims, wherein the one or more molten carbonate fuel cells are operated at a CO 2 utilization of 80% or greater.
  12. 12. The method of any of the above claims, wherein the cathode input stream comprises 6.0 vol% or less CO 2 , or wherein the cathode effluent comprises 1.0 vol% or less CO 2 , or a combination thereof.
  13. 13. The method of any one of claims 1 to 11, wherein the cathode input stream comprises 4.0 to 10% CO 2 by volume.
  14. 14. The method of any of the above claims, wherein the volume percent of hydrocarbons, reformable fuels, or combinations thereof in the input stream is 30 volume percent or greater than the volume percent of hydrocarbons, reformable fuels, or combinations thereof in the anode effluent.
  15. 15. A method of operating a molten carbonate fuel cell includes heating an input stream comprising 20% by volume or more hydrocarbons, reformable fuel, or a combination thereof by heat exchange with at least a portion of an anode effluent, reforming 15% or more of the input stream, reformable fuel, or a combination thereof to form a partially reformed input stream comprising 15% by volume or more hydrocarbons, reformable fuel, or a combination thereof, 15% by volume or more H 2 content, and 5.0% by volume or more carbon oxides, heating the partially reformed input stream to form an anode input stream comprising 550 ℃ or more anode input temperature, feeding the anode input stream to an anode of one or more molten carbonate fuel cells, internal reforming elements associated with the anode, or a combination thereof, feeding a cathode input stream comprising 4.0% by volume or more CO 2 and a cathode input temperature of 550 ℃ or more to one or more molten carbonate fuel cells, operating at an average current density of 100 mA/V2 or more, an anode input temperature of 53.65% or more of the anode and a cathode effluent of 5.0% by volume or more of the fuel cells, and a cathode input temperature of 53% or more fuel cell, and a cathode input rate of 53% or less fuel of the anode and cathode effluent of the fuel cell is greater than 30% by volume or less than 5.65% by volume or less.

Description

Improving reforming flux of molten carbonate fuel cells Technical Field Systems and methods for operating molten carbonate fuel cells are provided to generate increased hydrogen content in the anode effluent while maintaining the fuel cell operating at a target temperature and maintaining a target power generation. Background Molten carbonate fuel cells utilize hydrogen and/or other fuels to generate electricity. The hydrogen may be provided by reforming methane or other reformable fuel in a steam reformer, such as a steam reformer located upstream of or integrated within the fuel cell. The fuel may also be reformed in the anode chamber of a molten carbonate fuel cell that is operable to create conditions suitable for anode fuel reforming. Another option is to perform reforming both externally and internally to the fuel cell. Reformable fuels include hydrocarbon materials that can be reacted with steam and/or oxygen at elevated temperature and/or pressure to produce hydrogen-containing gaseous products. The basic structure of a molten carbonate fuel cell includes a cathode, an anode, and a matrix between the cathode and the anode that contains one or more molten carbonates that serve as electrolytes. During normal operation of a molten carbonate fuel cell, molten carbonate partially diffuses into the pores of the cathode. The diffusion of molten carbonate into the cathode pores forms an interface region where CO 2 can be converted to CO 3²- for transport through the electrolyte to the anode. Conventionally, molten carbonate fuel cells are operated at fuel utilization rates up to 65% to 75% to produce electricity. This selection is made based on a number of factors. First, the conventional fuel cell operates by burning the remaining fuel in the anode effluent to produce carbon dioxide, and then inputting the anode effluent as a cathode to provide carbon dioxide for operation of the fuel cell. Operating at a fuel utilization of 65% to 75% ensures that sufficient fuel remains in the anode effluent to produce sufficient carbon dioxide. The heat generated by the combustion reaction also helps to maintain the temperature of the fuel cell. Further, another advantage of selecting such a fuel utilization is that it can stably generate electricity and maintain a stable operating voltage and current density. While conventional molten carbonate fuel cells are primarily used for power generation, the operating environment characteristics of molten carbonate fuel cells also provide for the possibility of other types of operation. For example, molten carbonate fuel cells may be used as carbon capture devices by providing a cathode input stream that is substantially independent of the anode effluent composition. In addition, since reforming reactions can occur within the anode of a molten carbonate fuel cell, it is possible for the molten carbonate fuel cell to operate under conditions that produce a large excess of hydrogen at the anode output. A Journal article published by Manzolini et al in Journal of Fuel cell science and Technology (Journal of Fuel CELL SCIENCE AND Technology, month 2 2012, volume 9, pages 011018-1 to 011018-8) describes the operation of tandem cathode Fuel cells for separating carbon dioxide from power plant flue gas while generating electricity. U.S. patent application publication 2020/0176783 describes a cathode current collector structure that provides a greater open area for the cathode surface in the vicinity of the cathode current collector. U.S. patent application publication 2011/011315 describes a fuel cell operating system and process. The fuel cell operates at low fuel utilization and the hydrogen at the anode output is largely recycled back into the feed stream that ultimately forms the anode input. This low fuel utilization condition, in combination with reducing or minimizing the presence of non-hydrogen components in the fuel cell anode, is said to increase the cell voltage. U.S. patent 6,974,644 describes a fuel cell operating system and method in which the amount of direct internal reforming and indirect internal reforming can be controlled to better control the temperature profile of the fuel cell. By definition, both direct internal reforming and indirect internal reforming correspond to a reforming process that is sufficiently thermally integrated with the fuel cell so as to affect the temperature profile of the fuel cell. U.S. patent application publication 2005/0123810 describes operation of a fuel cell at lower fuel utilization so that excess hydrogen produced by internal reforming can be recovered as a hydrogen stream. SUMMARY In one aspect, a method of operating a molten carbonate fuel cell is provided. The method includes heating an input stream containing 20% by volume or more of hydrocarbons, reformable fuels, or a combination thereof by heat exchange with at least a portion of the anode effluent. The method further includes reforming 15% by volume or more of the hydrocar