Fuel cell system

1. A fuel cell system comprising:

a reformer operative to generate a reformed gas using a raw material;

a fuel cell operative to generate electric power using the reformed gas;

a raw material supply passage through which the raw material supplied to the reformer flows;

a hydro-desulfurizer operative to remove a sulfur component in the raw material supplied to the reformer;

a recycle passage through which a part of the reformed gas is supplied as a recycled gas to the raw material supply passage provided upstream of the hydro-desulfurizer;

a temperature detector operative to detect a temperature of the hydro-desulfurizer; and

a controller configured such that:

when the temperature of the hydro-desulfurizer detected by the temperature detector reaches a predetermined temperature, the controller increases a flow rate of the raw material from a predetermined flow rate by a flow rate corresponding to a flow rate of the recycled gas, and then, the controller starts supplying the recycled gas to the recycle passage; and

after the recycled gas reaches an upstream end of the recycle passage through the raw material supply passage, the controller returns the flow rate of the raw material to the predetermined flow rate.

2. The fuel cell system according to claim 1 , comprising:

a vaporizer operative to vaporize water supplied to the reformer; and

a water supplier operative to supply the water to the vaporizer, wherein:

the reformer generates the reformed gas using steam and the raw material;

when the temperature of the hydro-desulfurizer reaches the predetermined temperature, the controller increases a flow rate of the water from a predetermined flow rate by a flow rate corresponding to the flow rate of the recycled gas, and then, the controller starts supplying the recycled gas to the recycle passage; and

after the recycled gas reaches the upstream end of the recycle passage through the raw material supply passage, the controller returns the flow rate of the water to the predetermined flow rate.

3. The fuel cell system according to claim 1 , wherein while the fuel cell is generating the electric power, the predetermined flow rate is a flow rate corresponding to a predetermined electric power generation amount of the fuel cell.

4. A fuel cell system comprising:

a reformer operative to generate a reformed gas using a raw material;

a fuel cell operative to generate electric power using the reformed gas;

a raw material supply passage through which the raw material supplied to the reformer flows;

a hydro-desulfurizer operative to remove a sulfur component in the raw material supplied to the reformer;

a recycle passage through which a part of the reformed gas is supplied as a recycled gas to the raw material supply passage provided upstream of the hydro-desulfurizer;

a temperature detector operative to detect a temperature of the hydro-desulfurizer; and

a controller configured such that:

while the fuel cell is generating the electric power and before the temperature of the hydro-desulfurizer detected by the temperature detector reaches a predetermined temperature, the controller keeps an electric power generation amount of the fuel cell to be equal to or less than power consumption necessary for driving the fuel cell system such that the electric power is not supplied to an external load; and

after the recycled gas reaches an upstream end of the recycle passage through the raw material supply passage, the controller returns the electric power generation amount of the fuel cell to such an amount that supply of the electric power to the external load is realized.

5. A fuel cell system comprising:

a reformer operative to generate a reformed gas using a raw material;

a fuel cell operative to generate electric power using the reformed gas;

a raw material supply passage through which the raw material supplied to the reformer flows;

a hydro-desulfurizer operative to remove a sulfur component in the raw material supplied to the reformer;

a recycle passage through which a part of the reformed gas is supplied as a recycled gas to the raw material supply passage provided upstream of the hydro-desulfurizer;

a temperature detector operative to detect a temperature of the hydro-desulfurizer; and

a controller configured such that:

while the fuel cell is generating the electric power and before the temperature of the hydro-desulfurizer detected by the temperature detector reaches a predetermined temperature, the controller keeps an electric power generation amount of the fuel cell to be less than an output of a rated operation of the fuel cell system; and

after the recycled gas reaches an upstream end of the recycle passage through the raw material supply passage, the controller returns the electric power generation amount of the fuel cell to such an amount that the output of the rated operation of the fuel cell system is realized.

6. A fuel cell system comprising:

a reformer operative to generate a reformed gas using a raw material;

a fuel cell operative to generate electric power using the reformed gas;

a raw material supply passage through which the raw material supplied to the reformer flows;

a hydro-desulfurizer operative to remove a sulfur component in the raw material supplied to the reformer;

a recycle passage through which a part of the reformed gas is supplied as a recycled gas to the raw material supply passage provided upstream of the hydro-desulfurizer;

a temperature detector operative to detect a temperature of the hydro-desulfurizer; and

a controller configured such that:

while the fuel cell is generating the electric power and before the temperature of the hydro-desulfurizer detected by the temperature detector reaches a predetermined temperature, the controller makes an increasing speed of an electric power generation amount of the fuel cell lower than a predetermined increasing speed; and

after the recycled gas reaches an upstream end of the recycle passage through the raw material supply passage, the controller returns the increasing speed of the electric power generation amount of the fuel cell to the predetermined increasing speed.

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

a normal temperature desulfurizer operative to remove the sulfur component in the raw material at normal temperature;

a branch passage that branches from the raw material supply passage provided upstream of the normal temperature desulfurizer and joins the raw material supply passage extending between the normal temperature desulfurizer and the hydro-desulfurizer;

a first breaker disposed on the branch passage; and

a second breaker disposed on the raw material supply passage provided downstream of a branch portion where the branch passage branches from the raw material supply passage and upstream of a joining portion where the branch passage joins the raw material supply passage, wherein:

before the temperature of the hydro-desulfurizer reaches the predetermined temperature, the controller controls the first breaker and the second breaker such that the raw material flows through the normal temperature desulfurizer; and

when a predetermined time has elapsed since the first breaker is opened after the recycled gas reaches the upstream end of the recycle passage through the raw material supply passage, the controller closes the second breaker.

8. A fuel cell system comprising:

a reformer operative to generate a reformed gas using a raw material;

a fuel cell operative to generate electric power using the reformed gas;

a raw material supply passage through which the raw material supplied to the reformer flows;

a hydro-desulfurizer operative to remove a sulfur component in the raw material supplied to the reformer;

a recycle passage through which a part of the reformed gas is supplied as a recycled gas to the raw material supply passage provided upstream of the hydro-desulfurizer;

a temperature detector operative to detect a temperature of the hydro-desulfurizer; and

a controller configured such that:

while the fuel cell is generating the electric power and when the temperature of the hydro-desulfurizer detected by the temperature detector reaches a predetermined temperature, the controller makes a current taken out from the fuel cell lower than a current corresponding to a predetermined electric power generation amount of the fuel cell, and then, the controller starts supplying the recycled gas to the recycle passage; and

after the recycled gas reaches an upstream end of the recycle passage through the raw material supply passage, the controller returns the current taken out from the fuel cell to the current corresponding to the predetermined electric power generation amount.

9. The fuel cell system according to claim 8 , comprising:

a normal temperature desulfurizer operative to remove a sulfur component in the raw material at normal temperature;

a branch passage that branches from the raw material supply passage provided upstream of the normal temperature desulfurizer and joins the raw material supply passage extending between the normal temperature desulfurizer and the hydro-desulfurizer;

a first breaker disposed on the branch passage; and

a second breaker disposed on the raw material supply passage provided downstream of a branch portion where the branch passage branches from the raw material supply passage and upstream of a joining portion where the branch passage joins the raw material supply passage, wherein:

before the temperature of the hydro-desulfurizer reaches the predetermined temperature, the controller controls the first breaker and the second breaker such that the raw material flows through the normal temperature desulfurizer; and

when a predetermined time has elapsed since the first breaker is opened after the recycled gas reaches the upstream end of the recycle passage through the raw material supply passage, the controller closes the second breaker.

10. The fuel cell system according to claim 1 , wherein the controller includes a calculation processing portion and a storage portion, the storage portion storing a control program to be executed by the calculation processing portion.

11. The fuel cell system according to claim 4 , wherein the controller includes a calculation processing portion and a storage portion, the storage portion storing a control program to be executed by the calculation processing portion.

12. The fuel cell system according to claim 5 , wherein the controller includes a calculation processing portion and a storage portion, the storage portion storing a control program to be executed by the calculation processing portion.

13. The fuel cell system according to claim 6 , wherein the controller includes a calculation processing portion and a storage portion, the storage portion storing a control program to be executed by the calculation processing portion.

14. The fuel cell system according to claim 8 , wherein the controller includes a calculation processing portion and a storage portion, the storage portion storing a control program to be executed by the calculation processing portion.