Abstract: It is an object to provide a simple fuel cell system and to provide a fuel cell system capable of reducing the amount of consumption of fuel gas at the time of completion of operation. A fuel cell system includes a supply piping from a fuel gas supply source storing fuel gas to a gas inlet of a fuel cell and a circulation piping from a gas outlet of the fuel cell to a junction at which the circulation piping joins the supply piping. A regulating valve and a shut-off valve are disposed on the upstream side of the junction in the supply piping. A portion on the downstream side of the junction in the supply piping and the circulation piping are in constant communicated.

Abstract: A fuel cell system is provided in which the concentration increase of discharged fuel gas is inhibited even when abnormality is detected in a discharge unit. A fuel cell system in which a fuel gas discharged from a discharge unit (SV5) is diluted with an oxidizing gas (14) and discharged comprises an abnormality detection unit (205) for detecting an operation abnormality of the discharge unit (SV5), and a change unit (206, 207) for changing the supplied quantity of the oxidizing gas when an abnormality of the discharge unit (SV5) is detected, and the concentration of the diluted (14) and discharged fuel gas is changed and inhibited by changing the supplied quantity of the oxidizing gas.

Abstract: A failure diagnostic device for accurately determining a failure of a discharge valve. A failure diagnostic device (50) serves to perform failure diagnostic of a discharge valve (62) installed in a discharge flow channel (32) of an anode discharge gas that is discharged from a fuel cell stack (20). The device comprises a detection unit (70) for detecting a status quantity of the anode discharge gas between a discharge port (27) for the anode discharge gas of the fuel cells tack (2) and the discharge valve (62) and a determination unit (51) for determining a failure of the discharge valve (62) based on the status quantity of the anode discharge gas detected by the detection unit (70) and a failure determination quantity corresponding to the operating state of the fuel cell stack (20).

Abstract: A purging apparatus for a fuel cell system according to the present invention comprises a steam supply pass 18 and an air supply pass 19. A purging method for the fuel cell system according to the present invention comprises, at a time of causing a fuel reformer 12, a fuel cell body 1 and a fuel supply line 13 to carry out the purging operation, first carrying out the purging operation by steam, and then carrying out the purging operation by air. According to such a structure, there can be provided the purging apparatus for the fuel cell system and the method therefor, which have an easy structure and an easy operation, and enables combustible gas and condensed water remaining in the system to be removed in a reliable manner.