Solid polymer fuel cell systems incorporating water removal at the anode

DETAILED DESCRIPTION The above and other objects are achieved by a solid polymer fuel cell electric power generation system in which water accumulated at the cathode is removed in the outlet fuel stream of the anode.
The system comprises: (A) a hydrogen-containing inlet fuel stream; (B) an oxygen-containing inlet oxidant stream; (C) a fuel cell stack comprising at least one fuel cell comprising: (1) an anode having an inlet for directing the inlet fuel stream to the catalytically active portion of the anode to produce cations from the fuel stream and an outlet fuel stream; (2) a cathode having an inlet for directing the inlet oxidant stream to the catalytically active portion of the cathode to produce anions from the oxidant stream, the anions reacting with the cations to form water at the cathode; (3) an ion exchange membrane interposed between the anode and the cathode, the membrane facilitating the migration of cations from the anode to the cathode and isolating the inlet fuel stream from the inlet oxidant stream; and (4) an electrical path for conducting electric current between the anode to the cathode; and (D) a water separator for removing water from the outlet fuel stream to produce a dehumidified fuel stream and a removed water stream.
A substantial portion of water accumulated at the cathode is absorbed in the outlet fuel stream.
As used herein, "dehumidified" means that the relative humidity (moles of water per moles of gas relative to the same ratio when the gas is saturated with water at a given temperature and pressure) of the fluid stream has been reduced.
It does not mean or imply a complete removal of water from the stream.
In other words, a dehumidified stream can still have water present in the stream, but the relative amount of water present is less than that contained in the stream prior to dehumidification.
In the preferred system, the stoichiometry of the inlet oxidant stream is less than about 2.
0.
In systems where the inlet fuel stream comprises substantially pure hydrogen gas, the dehumidified fuel stream is preferably recirculated to the inlet fuel stream