Desulfurization using a molten carbonate fuel cell
AssigneeExxonMobil Technology and Engineering Company
InventorsFan He, Lu Han, Jonathan Rosen, Timothy A. Barckholtz
Life of this patent
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Abstract
Systems and methods are provided for maintaining and/or improving operating lifetime for molten carbonate fuel cells that contain reforming catalyst in the anode when processing cathode input flows that contain sulfur oxides. The systems and methods can include a serial arrangement of molten carbonate fuel cells, where a first fuel cell includes a reduced or minimized amount of reforming catalyst in the anode. A second molten carbonate fuel cell can include reforming catalyst in the anode.
Claims18
A method for operating a plurality of fuel cells, comprising:
- passing a first cathode input flow comprising O2, 4.0 vol % or more of CO2, and 20 ppbv or more of SO2 into a first cathode of a first molten carbonate fuel cell;
- passing a first anode input flow comprising H2 into a first anode of the first molten carbonate fuel cell, the first anode comprising a) substantially no reforming catalyst, or b) less than 0.04 g/cm3 of a reforming catalyst;
- operating the first molten carbonate fuel cell to produce a first cathode output flow and a first anode output flow, a ratio of SO2 in the first cathode output flow to SO2 in the first cathode input flow being 0.05 or less;
- passing a second cathode input flow into a second cathode of a second molten carbonate fuel cell, the second cathode input flow comprising at least a portion of the first cathode output flow, the second cathode input flow comprising O2, a CO2 content of 3.0 vol % or more, and a SO2 content that is lower than the SO2 content of the first cathode input flow;
- passing a second anode input flow comprising a reformable hydrocarbon into a second anode of the second molten carbonate fuel cell;
- and
- operating the second molten carbonate fuel cell at an average current density of 60 mA/cm2 or more to produce electricity, a second cathode output flow, and a second anode output flow,
- wherein a ratio of the volume of SO2 in the second cathode input flow to the volume of SO2 in the first cathode output flow is 0.5 to 5.0.
A fuel cell system, comprising:
- a first molten carbonate fuel cell, comprising a first cathode, a first electrolyte, and a first anode, the first anode comprising a) substantially no reforming catalyst, or b) a reforming catalyst density of less than 0.04 g/cm3, the first cathode comprising a first cathode outlet;
- a second molten carbonate fuel cell, comprising a second cathode, a second electrolyte, and a second anode, the second anode comprising a reforming catalyst density of 0.06 g/cm3 or more, the second cathode comprising a second cathode inlet in fluid communication with the first cathode outlet;
- and
- one or more separation stages in fluid communication with at least one of a second anode outlet of the second anode and a first anode outlet of the first anode,
- wherein the one or more separation stages comprise an H2S adsorbent stage, the desulfurization stage comprising a desulfurized stream outlet.
Dependencies are inferred from the claim text.