Patent ID: 6887609

Claim:
A method for operating a fuel cell system having a fuel cell unit with an anode and a cathode, a media flow path leading to the anode, a media flow path leading to the cathode, an anode exhaust-gas flow path, a cathode exhaust-gas flow path, a fan inserted in the media flow path leading to the cathode for supplying air to the cathode, and a catalytic burner arranged in the cathode exhaust-gas flow path, said method comprising: introducing an anode exhaust gas into, and mixing the anode exhaust gas with a cathode exhaust gas in, at least one of the catalytic burner and the cathode exhaust-gas flow path upstream of the catalytic burner; converting the anode exhaust gas and the cathode exhaust gas into a combined catalytically converted fuel cell exhaust flow in the catalytic burner, passing the combined catalytically converted fuel cell exhaust flow from the catalytic burner into an expansion machine; and feeding the fuel cell unit with a lower excess of hydrogen in part-load operation than in full-load operation.