Hydrogen recycle for solid oxide fuel cell
The present disclosure relates to solid oxide fuel cells (SOFCs) exploiting gas separation devices in which a first gas mixture including components A (for example hydrogen) and B (for example carbon dioxide) is to be separated so that a first product of the separation is enriched in component A, while component B is mixed with a third gas component C (for example air, oxygen-enriched air or oxygen-depleted air) contained in a displacement purge stream to form a second gas mixture including components B and C, and with provision to prevent cross contamination of component C into the first product containing component A, or of component A into the second gas mixture containing component C. The invention may be applied to hydrogen (component A) enrichment from fuel cell anode exhaust, where dilute carbon dioxide (component B) is to be rejected such as to the atmosphere by purging with cathode exhaust oxygen-depleted air (as component C).
1. An electrical current generation system comprising:
a fuel cell configured to operate at a temperature of at least about 250° C. and having an anode inlet and an anode exhaust outlet; and
a rotary adsorption module fluidly connected to the anode exhaust outlet and the anode inlet, and operable to receive exhaust gas from the anode exhaust outlet, to separate and enrich usable fuel gas from the exhaust gas by adsorptive means, and to deliver such enriched usable fuel gas to the anode inlet, wherein the rotary adsorption module comprises:
a rotor and a stator mutually defining a rotary distributor valve, wherein the rotor comprises:
plural adsorbers having first and second ends, each adsorber comprising an adsorbent material and defining a flow path in contact with the adsorbent material between the first and second ends;
a first rotor valve surface fluidly coupled to the first ends of the adsorbers; and a second rotor valve surface fluidly coupled to the second ends of the adsorbers;
and wherein the stator comprises:
a first stator valve surface in relatively rotatable communication with the first rotor valve a second stator valve surface in relatively rotatable communication with the second rotor valve surface;
a feed gas function compartment opening into at least one of the first stator valve surface or the second stator valve surface and configured to provide the exhaust gas from the anode exhaust outlet to adsorbers through the first stator valve surface or the second stator valve surface and the first rotor valve surface or the second rotor valve surface;
a displacement purge gas function compartment opening into at least one of the first stator valve surface or the second stator valve surface and configured to provide a displacement purge gas to the adsorbers through the first stator valve surface or the second stator valve surface and the first rotor valve surface or the second rotor valve surface; and
a buffer gas function compartment configured to provide a buffer gas to the adsorbers through the first stator valve surface or the second stator valve surface and the first rotor valve surface or the second rotor valve surface.
2. The system of claim 1 , wherein the fuel cell comprises a cathode inlet and a cathode exhaust gas outlet, and the displacement purge gas function compartment is fluidly coupled to the cathode exhaust gas outlet to provide cathode exhaust gas as the displacement purge gas.
3. The system of claim 1 , wherein the fuel cell comprises a cathode inlet, the rotary adsorption module is a first rotary adsorption module, and the system further comprises a second rotary adsorption module fluidly coupled to the cathode inlet to introduce oxygen-enriched air into the cathode inlet.
4. The system of claim 1 , wherein the adsorbent material comprises layers and at least one spacer between the layers.
5. The system of claim 1 , wherein the adsorbent material comprises an adsorbent laminate structure having a void fraction of about 10% to 50% of the laminate structure volume.
6. The system of claim 1 , wherein the adsorbent material comprises an adsorbent laminate structure having a void fraction of about 20% to 30% of the laminate structure volume.
7. The system of claim 1 , wherein the fuel cell comprises a solid oxide fuel cell.
8. The system of claim 1 , wherein the fuel gas and the displacement purge gas are incompatible.
9. The system of claim 1 , wherein the displacement purge gas function compartment is fluidly coupled to an air or nitrogen-enriched air source for providing air or nitrogen-enriched air as the displacement purge gas to the adsorbers.
10. The system of claim 3 , wherein the second rotary adsorption module is also fluidly coupled to the displacement purge gas function compartment to provide nitrogen-enriched air as the displacement purge gas to the adsorbers.
11. The system of claim 9 , wherein the fuel cell comprises a solid oxide fuel cell.
12. The system of claim 5 , wherein at least one adsorber includes at least one spacer between layers of adsorbent material.
13. The system of claim 11 , wherein the anode inlet is fluidly coupled to a hydrogen fuel source.
14. The system of claim 2 , wherein the anode inlet is fluidly coupled to a hydrogen fuel source, and the cathode inlet is fluidly coupled to an air or nitrogen-enriched air source.