Fuel cell system with recycle of anode exhaust gas
A fuel cell system having a fuel cell with an anode compartment and a cathode compartment. The fuel cell system is also provided with a partial-pressure pressure swing adsorption assembly operating at low pressure which uses supply gas for the cathode compartment of the fuel cell to separate carbon dioxide from the anode exhaust gas exiting from the anode compartment of the fuel cell. The partial-pressure pressure swing adsorption assembly is adapted to carry out this separation based on the difference in partial pressures of the carbon dioxide in the anode exhaust gas and the oxidant gas in the supply gas. The fuel cell system utilizes a further unit to recycle the exhaust gas, after separation of the carbon dioxide, to the anode compartment and to feed the supply gas with the carbon dioxide to the cathode compartment.
1. A fuel cell system comprising:
a fuel cell including an anode compartment and a cathode compartment;
a partial-pressure pressure swing adsorption assembly operating at low pressure of about 20 psia or less using oxidant supply gas for said cathode compartment to separate carbon dioxide from said anode exhaust gas, said partial-pressure pressure swing adsorption assembly providing said separation based on the difference in partial pressures of the carbon dioxide in said anode exhaust gas and the oxidant gas in said oxidant supply gas;
a unit recycling said anode exhaust gas, after separation of said carbon dioxide, to said anode compartment of said fuel cell and feeding said oxidant supply gas with said carbon dioxide to said cathode compartment of said fuel cell.
2. A fuel cell system according to claim 1 , further comprising:
a water transfer assembly separating water from anode exhaust gas exiting from said anode compartment.
3. A fuel cell system according to claim 2 , wherein:
said water transfer assembly is upstream of said partial-pressure pressure swing adsorption assembly.
4. A fuel cell system according to claim 3 , wherein:
said water transfer assembly comprises a partial-pressure pressure swing water transfer wheel; and
said partial-pressure pressure swing adsorption assembly comprises a carbon dioxide transfer wheel.
5. A fuel cell system according to claim 2 , wherein said water transfer assembly comprises a water absorbing media.
6. A fuel cell system according to claim 5 , wherein said water absorbing media operates at or above the dew point of the anode exhaust gas.
7. A fuel cell system according to claim 2 , wherein said water transfer assembly comprises a condenser.
8. A fuel cell system according to claim 7 , wherein said water transfer assembly further comprises a scrubbing unit and a blowdown unit for removal of water contaminated with electrolyte.
9. A fuel cell system comprising:
a fuel cell including an anode compartment and a cathode compartment;
a partial-pressure pressure swing adsorption assembly which operates at low pressures of about 20 psia or less and has an adsorption medium, said partial-pressure pressure swing adsorption assembly, in an adsorbing step, adsorbing in said adsorption medium carbon dioxide from the anode exhaust gas of said fuel cell and, in a medium regeneration step, using the oxidant supply gas for said cathode compartment to remove said carbon dioxide from said adsorption medium by flowing said oxidant supply gas across said adsorption medium and thereby creating low partial pressures of the carbon dioxide in said adsorption medium; and
a unit recycling said anode exhaust gas, after separation of said carbon dioxide, to said anode compartment of said fuel cell and feeding said oxidant supply gas with said carbon dioxide to said cathode compartment of said fuel cell.