Controlling the temperature at which fuel cell exhaust is oxidized

A fuel cell system comprising:

• a fuel cell stack which generates electrical energy during operation by reacting two streams of reactant gases, the fuel cell stack also producing a fuel cell exhaust stream;
• an oxidizer unit positioned to receive the fuel cell exhaust stream, the oxidizer unit oxidizing at least a part of the fuel cell exhaust stream in an oxidizing gas stream during operation;
• a temperature sensor positioned to sense a temperature of the oxidizer unit;
• and
• an input system to provide the oxidizer unit with an amount of the oxidizing gas stream in excess of a stoichiometric amount required to oxidize the part of the fuel cell exhaust stream, the input system responding to the temperature of the oxidizing unit by controlling the amount of oxidizing gas provided to achieve a desired difference between the provided amount of the oxidizing gas stream and the stoichiometric amount,
• a source to provide the oxidizing gas stream;
• and
• a controller to control the amount of the oxidizing gas stream provided by the source in response to the temperature of the oxidizer unit;
• wherein the controller stores a stoichiometric table for determining a stoichiometric amount of the oxidizing gas stream, and the controller uses the stoichiometric table when generating the control signal to direct the source to provide the oxidizer unit with the excess of the stoichiometric amount of the oxidizing gas stream.