Electrochemical fuel cell system with a regulated vacuum ejector for recirculation of the fluid fuel stream

An electric power generation system comprising:

• (a) a fuel cell stack comprising a fuel stream inlet, an oxidant stream inlet, an oxidant stream outlet, and at least one fuel cell for promoting an electrocatalytic reaction of a fuel stream introduced at said fuel stream inlet with an oxidant stream introduced at said oxidant stream inlet to produce electricity, reaction product, and heat;
• (b) a pressurized oxidant supply having a pressure control valve for regulating the pressure of said oxidant supply;
• (c) a vacuum ejector interposed between said oxidant supply and said oxidant stream inlet, said ejector comprising a motive inlet, a suction inlet, and a discharge outlet, said motive inlet fluidly connected to said oxidant supply, said suction inlet fluidly connected to said oxidant stream outlet, and said discharge outlet fluidly connected to said oxidant stream inlet;
• (d) a pressure transducer interposed in said oxidant stream between said discharge outlet and said suction inlet, said pressure transducer detecting the pressure of said oxidant stream and transmitting a corresponding signal to said pressure control valve;
• and
• (e) a pressurized fuel supply fluidly connected to said fuel stream inlet;
• whereby said pressure transducer transmits a signal to said pressure control valve to increase the pressure of said oxidant supply when the detected pressure of said oxidant stream falls below a predetermined value and said pressure transducer transmits a signal to said pressure control valve to decrease the pressure of said oxidant supply when the detected pressure of said oxidant stream exceeds a predetermined value.

A method for recirculating a first reactant stream in an electric power generation system comprising a fuel cell stack comprising a first reactant stream inlet, a first reactant stream outlet, an second reactant stream inlet, and at least one fuel cell for promoting the electrocatalytic reaction of the first reactant stream introduced at the first reactant stream inlet with a second reactant stream introduced at the second reactant stream inlet to produce electricity, reaction product, and heat, the system further comprising a pressurized first reactant supply having a pressure control valve for regulating the pressure of the first reactant supply, and a pressurized second reactant supply, the method comprising the steps of:

• (a) interposing a vacuum ejector between the first reactant supply and the first reactant stream inlet, said ejector comprising a motive inlet, a suction inlet, and a discharge outlet;
• (b) fluidly connecting said motive inlet to said first reactant supply;
• (c) fluidly connecting said suction inlet to said first reactant stream outlet;
• (d) fluidly connecting said discharge outlet to said first reactant stream inlet;
• (e) interposing a pressure transducer between said discharge outlet and said suction inlet, said pressure transducer capable of detecting the pressure of said first reactant stream and transmitting a corresponding signal to said pressure control valve;
• (f) transmitting a signal to said pressure control valve to increase the pressure of said first reactant supply when the detected pressure of said first reactant stream falls below a predetermined value;
• and
• (g) transmitting a signal to said pressure control valve to decrease the pressure of said first reactant supply when the detected pressure of said first reactant stream exceeds a predetermined value.