Hydrogen generator and fuel cell system including the same

1. A hydrogen generator comprising:

a heater which combusts a mixture gas of combustion fuel and combustion air to generate a combustion gas;

an annular preheat evaporator which heats a raw material and water by the combustion gas generated by said heater to generate a mixture gas of the raw material and steam;

an annular reformer, the entirety of which is disposed under said preheat evaporator and which generates a hydrogen-containing gas by causing the mixture gas generated by said preheat evaporator to pass through a reforming catalyst heated by the combustion gas; and

a water trapping portion which is located between said preheat evaporator and said reformer and traps liquid water discharged from said preheat evaporator.

2. The hydrogen generator according to claim 1 , further comprising an annular shift converter which is disposed around an outer periphery of said preheat evaporator and contains a shift catalyst which reduces, by a shift reaction, carbon monoxide contained in the hydrogen-containing gas generated by said reformer, wherein

said water trapping portion is disposed adjacent to a gas passage of the hydrogen-containing gas from said reformer to said shift converter so that heat is exchanged between the hydrogen-containing gas supplied from said reformer to said shift converter and the liquid water in said water trapping portion.

3. The hydrogen generator according to claim 2 , wherein:

each of said preheat evaporator, said water trapping portion, said reformer, and said shift converter is disposed outside said heater so as to have a tubular shape,

said shift converter is disposed to surround said preheat evaporator,

said preheat evaporator, said water trapping portion, and said reformer are connected to one another such that the mixture gas is supplied from said preheat evaporator through said water trapping portion to said reformer, and

heat is exchanged between the hydrogen-containing gas supplied from said reformer to said shift converter and the liquid water in said water trapping portion via a wall between said gas passage and said water trapping portion.

4. The hydrogen generator according to claim 3 , wherein a supply port of the raw material and a supply port of the water are disposed at one end of said preheat evaporator which is opposite to another end to which said water trapping portion is connected.

5. The hydrogen generator according to claim 2 , further comprising:

a combustion air supplying unit which supplies the combustion air to said heater;

a water supplying unit which supplies the water to said preheat evaporator;

a temperature detector which detects a temperature of the shift catalyst incorporated in said shift converter; and

a control unit, wherein

said control unit controls, based on the temperature of the shift catalyst detected by said temperature detector, at least one of a supply amount of the water supplied from said water supplying unit to said preheat evaporator and a supply amount of the combustion air supplied from said combustion air supplying unit to said heater.

6. The hydrogen generator according to claim 5 , further comprising a storage unit which contains information regarding an upper limit temperature and a lower limit temperature associated with temperature control of the shift catalyst, wherein

said control unit causes said water supplying unit to increase the supply amount of the water supplied to said preheat evaporator when the temperature detected by said temperature detector becomes the upper limit temperature or more, and causes said water supplying unit to decrease the supply amount of the water supplied to said preheat evaporator when the temperature detected by said temperature detector becomes the lower limit temperature or less.

7. The hydrogen generator according to claim 6 , wherein:

said storage unit further contains information regarding an upper limit supply amount and a lower limit supply amount associated with control of the supply amount of the water; and

said control unit determines that an abnormality has occurred when the supply amount of the water supplied from said water supplying unit to said preheat evaporator becomes the upper limit supply amount or more or when the supply amount of the water supplied from said water supplying unit to said preheat evaporator becomes the lower limit supply amount or less.

8. The hydrogen generator according to claim 5 , further comprising a storage unit which contains information regarding an upper limit temperature and a lower limit temperature associated with temperature control of the shift catalyst, wherein

said control unit causes said combustion air supplying unit to decrease the supply amount of the combustion air supplied to said heater when the temperature detected by said temperature detector is not less than the upper limit temperature, and causes said combustion air supplying unit to increase the supply amount of the combustion air supplied to said heater when the temperature detected by said temperature detector is not more than the lower limit temperature.

9. The hydrogen generator according to claim 8 , wherein:

said storage unit further contains information regarding an upper limit supply amount and a lower limit supply amount associated with control of the supply amount of the combustion air; and

said control unit determines that an abnormality has occurred when the supply amount of the combustion air supplied from said combustion air supplying unit to said heater becomes the upper limit supply amount or more or when the supply amount of the combustion air supplied from said combustion air supplying unit to said heater becomes the lower limit supply amount or less.

10. The hydrogen generator according to claim 5 , further comprising a storage unit which contains information regarding an upper limit temperature and a lower limit temperature associated with temperature control of the shift catalyst and information regarding an upper limit supply amount and a lower limit supply amount associated with control of the supply amount of the water, wherein

said control unit causes said combustion air supplying unit to decrease the supply amount of the combustion air supplied to said heater when the temperature of the shift catalyst is not less than the upper limit temperature and the supply amount of the water supplied from said water supplying unit to said preheat evaporator is not less than the upper limit supply amount, and causes said combustion air supplying unit to increase the supply amount of the combustion air supplied to said heater when the temperature of the shift catalyst is not more than the lower limit temperature and the supply amount of the water supplied from said water supplying unit to said preheat evaporator is not more than the lower limit supply amount.

11. The hydrogen generator according to claim 5 , further comprising a storage unit which contains information regarding an upper limit temperature and a lower limit temperature associated with temperature control of the shift catalyst and information regarding an upper limit supply amount and a lower limit supply amount associated with control of the supply amount of the combustion air, wherein

said control unit causes said water supplying unit to increase the supply amount of the water supplied to said preheat evaporator when the temperature of the shift catalyst is not less than the upper limit temperature and the supply amount of the combustion air supplied from said combustion air supplying unit to said heater is not more than the lower limit supply amount, and causes said water supplying unit to decrease the supply amount of the water supplied to said preheat evaporator when the temperature of the shift catalyst is not more than the lower limit temperature and the supply amount of the combustion air supplied from said combustion air supplying unit to said heater is not less than the upper limit supply amount.

12. A fuel cell system comprising at least:

a hydrogen generator; and

a fuel cell which generates electric power using the hydrogen-containing gas supplied from the hydrogen generator and an oxygen-containing gas,

wherein said hydrogen generator comprises:

a heater which combusts a mixture gas of combustion fuel and combustion air to generate a combustion gas;

an annular preheat evaporator which heats a raw material and water by the combustion gas generated by said heater to generate a mixture gas of the raw material and steam;

an annular reformer, the entirety of which is disposed under said preheat evaporator and which generates a hydrogen-containing gas by causing the mixture gas generated by said preheat evaporator to pass through a reforming catalyst heated by the combustion gas; and

a water trapping portion which is located between said preheat evaporator and said reformer and traps liquid water discharged from said preheat evaporator.