Solid-oxide fuel cell system having means for controlling tail gas combustion temperature

In a fuel cell system having a combustor for burning anode tail gas, spent cathode air, and fresh air together to produce a hot exhaust, a method for controlling combustion temperature in the combustor within a predetermined operating range, comprising the steps of:

• a) providing means for measuring temperature within said combustor;
• b) providing first conduit means for conveying said spent cathode air to said combustor, said first conduit means including a three-way valve for controllably diverting a portion of said spent cathode air from entering said combustor;
• c) providing second conduit means for providing fresh air to said combustor, said second conduit means including a control valve for controllably varying the amount of air flowing to said combustor;
• d) adjusting said three-way valve to provide less spent cathode air to said combustor when said operating temperature is below a lower limit of said range;
• and
• e) adjusting said control valve to provide more fresh air to said combustor when said operating temperature is above an upper limit of said range.

An automotive vehicle, comprising a fuel cell system for generating auxiliary power for said vehicle, said system including

• a combustor for burning a mixture of anode tail gas and air,
• temperature measuring means within said combustor,
• first conduit means for providing spent cathode air to said combustor, said first conduit means including a three-way valve for controllably diverting a portion of said spent cathode air from entering said combustor,
• second conduit means for providing fresh air to said combustor, said second conduit means including a control valve for controllably varying the amount of air flowing to said combustor, and
• control means for monitoring said combustion temperature via said temperature measuring means and for responding when said combustor temperature is out of a predetermined operating range, said control means being operationally connected to said three-way valve to provide less spent cathode air to said combustor when said operating temperature is below a lower limit of said range, and being further operationally connected to said control valve to provide more fresh air to said combustor when said operating temperature is above an upper limit of said range.