Onboard fuel cell system and method of discharging hydrogen-off gas

Abstract

Consumed hydrogen-off gas is discharged from a fuel cell via a hydrogen-off gas exhaust flow passage. Consumed oxygen-off gas is discharged from the fuel cell via an oxygen-off gas exhaust flow passage. The oxygen-off gas flowing through the oxygen-off gas exhaust flow passage and the hydrogen-off gas flowing through the hydrogen-off gas exhaust flow passage are mixed and diluted in a mixing portion. The gases mixed in the mixing portion flow into a combustor via a gas-liquid separator. The combustor, which includes a platinum catalyst, causes hydrogen contained in the mixed gases to react with oxygen by combustion and further reduces the concentration of hydrogen contained in the mixed gases. The mixed gases whose concentration of hydrogen has been reduced by the combustor is discharged to the atmosphere.

1 . An onboard fuel cell system comprising:
 a fuel cell which may be supplied with hydrogen gas and oxidative gas, which can generate electric power using the hydrogen gas and the oxidative gas, and which can discharge hydrogen-off gas and oxygen-off gas that have been consumed;   a first flow passage which leads to a hydrogen-off gas exhaust port of the fuel cell and through which the discharged hydrogen-off gas can flow;   a second flow passage which leads to an oxygen-off gas exhaust port of the fuel cell and through which the discharged oxygen-off gas can flow;   a mixing portion which is connected to receive the discharged hydrogen-off gas and the discharged oxygen-off gas from the first and second flow passages respectively and in which the oxygen-off gas may be mixed with the hydrogen-off gas;   a third flow passage which leads from the mixing portion and through which the mixed gases can flow so that the hydrogen-off gas may be discharged to the atmosphere;   a fourth flow passage which leads to an oxidative gas-supplying port of the fuel cell and through which the supplied oxidative gas can flow;   a gas-liquid separator which is disposed in the second flow passage and in which liquid contents may be separated from the discharged oxygen-off gas; and   a fifth flow passage which leads to the gas-liquid separator and through which the liquid separated by the gas-liquid separator may be supplied to the fourth flow passage.