Fuel cell system

1. A fuel cell system comprising:

a hydrogen generator including a reformer which has a reforming catalyst and carries out a reforming reaction using the reforming catalyst to generate a hydrogen-containing gas from a raw material, a shift converter which has a shift catalyst and carries out a shift reaction using the shift catalyst to decrease carbon monoxide in the hydrogen-containing gas, and a first temperature detector which detects a temperature of the shift converter;

a fuel cell which uses the hydrogen-containing gas delivered from the hydrogen generator, to generate electric power;

a timer; and

a control unit including a processor and a memory storing a program, the program, when executed by the processor, causing the processor:

not to start delivering the hydrogen-containing gas from the hydrogen generator to the fuel cell when at least the temperature of the shift converter detected by the first temperature detector is not a stable determination temperature or higher; and

to acquire an operation stop period of the fuel cell from the timer and change the stable determination temperature by utilizing the acquired operation stop period, wherein:

the stable determination temperature being lower than a control temperature of the shift converter at the time of a normal operation, and

the operation stop period is an elapsed time period from a stop of a previous operation of the fuel cell system.

2. The fuel cell system according to claim 1 , further comprising a storage unit which is adapted to store the stable determination temperature corresponding to the operation stop period, wherein

the program of the control unit further causes the processor to, after determining the operation stop period, change the stable determination temperature to a stable determination temperature, which corresponds to the determined operation stop period, based on a correspondence between the operation stop period stored in the storage unit and the stable determination temperature.

3. The fuel cell system according to claim 1 , wherein the shift catalyst is configured to contain copper or zinc.

4. The fuel cell system according to claim 1 , further comprising a second temperature detector which detects a temperature of the reformer, wherein

the program of the control unit further causes the processor not to start delivering the hydrogen-containing gas from the hydrogen generator to the fuel cell when the temperature of the reformer detected by the second temperature detector is not a reforming operating temperature or higher.

5. The fuel cell system according to claim 1 , wherein the stable determination temperature is such a temperature of the shift converter that a concentration of the carbon monoxide in the hydrogen-containing gas is able to be decreased by the shift converter to an upper limit concentration or lower of the hydrogen-containing gas which is able to be supplied to the fuel cell.

6. The fuel cell system according to claim 1 , wherein:

the control temperature is a temperature in a ⅓ higher temperature range of such an entire temperature range that a concentration of the carbon monoxide in the hydrogen-containing gas is able to be decreased by the shift converter to an upper limit concentration or lower of the hydrogen-containing gas which is able to be supplied to the fuel cell; and

the stable determination temperature is a temperature in a lower temperature range that is the entire temperature range except for the ⅓ higher temperature range.

7. The fuel cell system according to claim 1 , wherein:

the control temperature is higher than a temperature at which a concentration of the carbon monoxide in the hydrogen-containing gas becomes minimum, in such an entire temperature range that the concentration of the carbon monoxide in the hydrogen-containing gas is able to be decreased by the shift converter to an upper limit concentration or lower of the hydrogen-containing gas which is able to be supplied to the fuel cell; and

the stable determination temperature is lower than the temperature at which the concentration of the carbon monoxide in the hydrogen-containing gas becomes minimum.