JP4248182B2 - Fuel cell power generation system and fuel cell purging method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation system and a fuel cell purge method.
[0002]
[Prior art]
Conventionally, a purge method using a combustion gas has been proposed as a purge method for this type of fuel cell (for example, JP 2000-243423 A). In this purge method, the anode is purged with a reducing atmosphere gas obtained by mixing and burning the cathode off-gas discharged from the cathode of the fuel cell using a gas containing hydrogen, and the anode off-gas discharged from the anode is a gas containing oxygen. By purging the cathode with an oxidizing atmosphere gas obtained by mixing and burning using the gas, the anode is held in a reducing atmosphere and the cathode is held in an oxidizing atmosphere for purging.
[0003]
[Problems to be solved by the invention]
However, in such a fuel cell purging method, since it is necessary to adjust the temperature, moisture, etc. of the combustion gas, it takes time for purging. Further, since it is necessary to include both a cathode offgas combustion section for mixing and burning the cathode offgas and an anode offgas combustion section for mixing and burning the anode offgas, the system becomes complicated.
[0004]
The fuel cell power generation system and the fuel cell purging method of the present invention have an object of purging without using a dedicated purging gas. Another object of the fuel cell power generation system and the fuel cell purge method of the present invention is to quickly purge. Furthermore, the fuel cell power generation system of the present invention has an object to simplify the equipment required for purging.
[0005]
[Means for solving the problems and their functions and effects]
The fuel cell power generation system and the fuel cell purging method of the present invention employ the following means in order to achieve at least a part of the above-described object.
[0006]
The fuel cell power generation system of the present invention comprises:
Reforming means for reforming gaseous hydrocarbon fuel into hydrogen-rich fuel gas;
A fuel cell that generates power using the fuel gas supplied from the reforming means;
A branch pipe for branching from a fuel supply pipe for supplying hydrocarbon fuel to the reforming means and for supplying hydrocarbon fuel to the anode side of the fuel cell;
An openable and closable control valve provided in the branch pipe;
When the predetermined purge instruction is given, the control valve is opened, and after the control valve is opened, the control valve is closed after waiting for a time necessary for purging the fuel cell to elapse. The supply of hydrocarbon fuel to the fuel cell is temporarily stopped, and after the predetermined time has elapsed since the supply of the hydrocarbon fuel is temporarily stopped, the control valve is opened to eliminate the negative pressure of the fuel cell. Control means for supplying the fuel cell with a hydrocarbon-based fuel necessary for
It is a summary to provide.
[0007]
In this fuel cell power generation system of the present invention, when a predetermined purge instruction is given, the control valve is opened, and gaseous hydrocarbon fuel as a reforming raw material used in the reforming means is supplied via the branch pipe. Since the fuel cell is purged by using it, it can be purged without using a dedicated purge gas. As a result, the system can be made simpler than those using a dedicated purging gas or using the off-gas from the fuel cell after burning. Moreover, since it is not necessary to adjust the temperature and moisture of the hydrocarbon fuel, the purge can be completed quickly.
[0008]
In the fuel cell power generation system of the present invention, the hydrocarbon fuel may be city gas. In this case, provided with a desulfurization means attached to the fuel supply pipe to remove the sulfur content of the city gas, the branch pipe is a pipe branched on the downstream side of the desulfurization means of the fuel supply pipe, You can also
[0009]
The fuel cell power generation system of the present invention may include a combustion means for burning the combustible component in the exhaust gas discharged at the time of purging performed in accordance with the predetermined purge instruction. If it carries out like this, the combustible component in the waste gas discharged | emitted in the case of a purge can be burned and exhausted. In this aspect of the fuel cell power generation system of the present invention, the combustion means may be means capable of combusting the hydrocarbon-based fuel used for purging. If it carries out like this, the hydrocarbon fuel used for purge can be burned and exhausted. In the fuel cell power generation system of the present invention having such combustion means, the combustion means is a combustion section provided in the reforming means in order to obtain heat necessary for the reforming reaction in the reforming means. It can also be. In this way, there is no need to provide a dedicated combustion section used for combustion of combustible components in the exhaust gas discharged at the time of purging or combustion of hydrocarbon fuel used for purging. As a result, the system can be simplified.
[0010]
[0011]
[0012]
[0013]
The fuel cell power generation system of the present invention may further include power conversion supply means capable of converting DC power from the fuel cell into desired power and supplying the power supply line from another system power source to the load. . If it carries out like this, electric power can be additionally supplied with other system power supplies.
[0014]
The fuel cell power generation system according to the present invention may include a hot water storage unit that stores at least water that is heated using heat from the fuel cell. In this way, since the heat from the fuel cell can be used, the energy efficiency of the system can be improved. Of course, heat other than the heat from the fuel cell may be used.
[0015]
[0016]
[0017]
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described using examples. FIG. 1 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system 20 which is a reference example of the present invention. As shown in the figure, the fuel cell power generation system 20 of the reference example is supplied with city gas (13A) from a gas pipe 22 and reforms the city gas into hydrogen-rich reformed gas, and a reformer. A CO selective oxidation unit 34 that reduces carbon monoxide in the gas and uses it as a fuel gas, a fuel cell 40 that receives supply of the fuel gas and air, and generates power by an electrochemical reaction, and a cooling water and hot water storage for the fuel cell 40 A heat exchanger 42 that performs heat exchange with the low-temperature water in the tank 44, a DC / DC converter 52 that adjusts the voltage and current of the DC power from the fuel cell 40 to convert it to desired DC power, and the converted DC An inverter 54 that supplies power to the power line 12 that converts power into AC power having the same phase as that of the commercial power supply 10 and supplies power from the commercial power supply 10 to the load 16 via the circuit breaker 14, a voltage or Current A DC / DC converter 56 that functions as an auxiliary power supply by stepping down a part of the adjusted DC power, a load wattmeter 58 that detects load power consumed by the load 16, and an electronic control unit 60 that controls the entire system. With.
[0019]
The reformer 30 adjusts the city gas supplied from the gas pipe 22 through the control valve 24, the booster pump 26, the desulfurizer 27 excluding sulfur and the control valve 28, and the water tank 36 through the evaporator 37. Hydrogen-rich reformed gas is generated by the steam reforming reaction and shift reaction of the following formula (1) and the following formula (2) with the steam whose flow rate is adjusted by the valve 38. The reformer 30 is provided with a combustion section 32 that supplies heat necessary for such a reaction. The combustion section 32 is supplied with city gas from the gas pipe 22 via the control valve 24 and the booster pump 23. It has become so. Further, the exhaust gas on the anode side of the fuel cell 40 is supplied to the combustion unit 32 so that unreacted hydrogen in the anode off-gas can be used as fuel. When the amount of hydrogen in the anode off-gas is larger than a predetermined amount, part or all of the anode off-gas can be guided to the combustor 49 and burned and exhausted by operating the valve 47 and the valve 48.
[0020]
CH4 + H2O → CO + 3H2 (1)
CO + H2O → CO2 + H2 (2)
[0021]
The CO selective oxidation unit 34 is modified by a carbon monoxide selective oxidation catalyst (for example, a catalyst made of an alloy of platinum and ruthenium) that receives supply of air from a pipe (not shown) and selects and oxidizes carbon monoxide in the presence of hydrogen. Carbon monoxide in the gas is selectively oxidized to form a hydrogen-rich fuel gas having a very low carbon monoxide concentration (about several ppm in the reference example ).
[0022]
The fuel cell 40 comprises a single cell comprising an electrolyte membrane, an anode electrode and a cathode electrode sandwiching the electrolyte membrane, a fuel gas and air to the anode electrode and the cathode electrode, and a separator that forms a partition between the cells. It is configured as a solid polymer fuel cell formed by stacking a plurality of layers, and generates power by an electrochemical reaction between hydrogen in the fuel gas from the CO selective oxidation unit 34 and oxygen in the air from the blower 41. The fuel cell 40 is formed with a circulating cooling water flow path, and is maintained at an appropriate temperature (in the reference example , about 80 to 90 ° C.) by circulating the cooling water. A heat exchanger 42 is provided in the cooling water circulation flow path, and the low temperature water supplied from the hot water storage tank 44 by the pump 46 is heated by heat exchange with the cooling water of the fuel cell 40 so that the hot water storage tank. The hot water is stored in 44.
[0023]
An output terminal (not shown) of the fuel cell 40 is connected to the power line 12 from the commercial power supply 10 to the load 16 via the DC / DC converter 52, the inverter 54, and the circuit breaker 55. The AC power is converted into AC power having the same phase as that of the commercial power supply 10, added to the AC power from the commercial power supply 10, and supplied to the load 16. Since the DC / DC converter 52 and the inverter 54 are configured as a general DC / DC converter circuit and an inverter circuit, detailed description thereof is omitted. The load 16 is connected to the power line 12 via the circuit breaker 18.
[0024]
The power line branched from the output side of the DC / DC converter 52 has a DC / DC functioning as a direct current power source for supplying direct current power to the actuators of the control valve 24 and auxiliary devices such as the boost pumps 26 and 28, the blower 41 and the pump 46. A DC converter 56 is connected.
[0025]
The electronic control unit 60 is configured as a microprocessor centered on the CPU 62. In addition to the CPU 62, a ROM 64 for storing processing programs, a RAM 66 for temporarily storing data, an input / output port and a communication port (not shown) Is provided. The electronic control unit 60 includes an output current i and voltage V from a current sensor and voltage sensor in an inverter 54 (not shown), a load power Po from a load wattmeter 58, a reformer 30, a CO selective oxidation unit 34, a fuel cell. Each temperature from a temperature sensor (not shown) attached to 40 is input via an input port. Further, from the electronic control unit 60, the drive signals to the actuators of the control valves 24, 28, the boost pumps 23, 26, the blower 41, the circulation pump 43, the pump 46, etc., the ignition signals to the combustion section 32, the valves 47, 48. Drive signal, a control signal to the DC / DC converter 52 and the DC / DC converter 56, a switching control signal to the inverter 54, a drive signal to the circuit breaker 55, and the like are output via the output port.
[0026]
Next, the operation of the fuel cell power generation system 20 configured as described above, particularly the purge operation when the system is stopped will be described. FIG. 2 is a flowchart showing an example of a purge process routine executed by the electronic control unit 60. This routine is executed when the circuit breaker 55 is disconnected from the commercial power supply 10 and the purge instruction is issued after the inverter 54 is turned off.
[0027]
When this purge processing routine is executed, the CPU 62 of the electronic control unit 60 first closes the control valve 38 and stops the evaporator 37 to stop the supply of water vapor used for the reforming reaction (step). S100), the control valve 47 is closed and the control valve 48 is opened to switch the combustion path of the anode off gas to purge (step S102), the combustor 49 is operated (step S104), and the reformer 30 The combustion unit 32 is stopped (step S106). The city gas supplied from the gas pipe 22 and desulfurized by the desulfurizer 27 is reformed by the reformer 30 by stopping the supply of water vapor to the reformer 30 and the combustion unit 32 of the reformer 30. Without reacting, the reformer 30, the CO selective oxidation unit 34, and the fuel cell 40 flow in the order of pushing out city gas and fuel gas in the middle of the reaction. At this time, the gas discharged from the anode side of the fuel cell 40 is introduced into the combustor 49 and burned and exhausted.
[0028]
After the time required for purging has elapsed after performing such processing (step S108), the control valve 28 and the control valve 48 are closed to seal the fuel gas system from the reformer 30 to the fuel cell 40. (Step S110). Here, the time required for purging is the time required to replace the gas in the reformer 30, the CO selective oxidation unit 34, and the fuel cell 40 with the city gas, and the supply flow rate of the city gas and the reformer 30. , The CO selective oxidation unit 34, the capacity of the fuel cell 40, the capacity of the fuel gas piping, and the like.
[0029]
When the fuel gas system is sealed, after waiting for a predetermined time since the fuel gas system is sealed (step S112), a predetermined amount of city gas is supplied to the reformer 30 (step S114). finish. Here, the predetermined time is set as a time required for the temperature of the reformer 30 to be lowered to some extent. As described above, the predetermined amount of city gas is supplied to the reformer 30 after the temperature of the reformer 30 is lowered in order to alleviate the negative pressure of the reformer 30 that is generated as the temperature decreases. is there.
[0030]
According to the fuel cell power generation system 20 of the reference example described above, since the reformer 30 and the fuel cell 40 are purged using the city gas as the reforming raw material as the purge gas, a gas dedicated for purging is prepared. There is no need to do. Moreover, since the fuel gas supply flow path from the reformer 30 to the fuel cell 40 can be used as it is, it is not necessary to provide a purge pipe. As a result, the system can be simplified. Further, since it is not necessary to adjust the temperature and moisture of the city gas used as the purge gas, it can be quickly purged.
[0031]
According to the fuel cell power generation system 20 of the reference example , after the reformer 30 and the fuel cell 40 are purged using city gas, the reformer 30 waits for the temperature of the reformer 30 to be lowered to some extent, and the city gas is reformed. Since it supplies to 30, the negative pressure of the reformer 30 can be relieved. As a result, outside air can be prevented from entering the reformer 30.
[0032]
In the fuel cell power generation system 20 of the reference example , a predetermined amount of city gas is supplied to the reformer 30 when a predetermined time elapses after the purge is completed, but the temperature of the reformer 30 is equal to or lower than a predetermined temperature. A predetermined amount of city gas may be supplied to the reformer 30 when it is detected. Further, the number of times the city gas is supplied to the reformer 30 after the purge is completed is not limited to one, and the city gas may be supplied to the reformer 30 a plurality of times after the purge is completed.
[0033]
In the fuel cell power generation system 20 of the reference example , a predetermined amount of city gas is supplied to the reformer 30 when a predetermined time elapses after the purge is completed. However, the hermeticity of the reformer 30 is very high. In this case, the city gas may not be supplied to the reformer 30 after the purge is completed.
[0034]
In the fuel cell power generation system 20 of the reference example, the gas pushed out by the city gas during the purge process and discharged from the fuel cell 40 is guided to the combustor 49 and burned and exhausted. It is good also as what guide | induces to the combustion part 32 of the quality device 30, and burns and exhausts. In this way, it is not necessary to provide the combustor 49.
[0035]
In the fuel cell power generation system 20 of the reference example, the reformer 30 and the fuel cell 40 are purged by the city gas, but only the fuel cell 40 may be purged by the city gas. An outline of the configuration of the fuel cell power generation system 20B of the embodiment is shown in FIG. In the fuel cell power generation system 20B of this embodiment , as shown in the figure, the purge pipe 70 is branched on the downstream side of the desulfurizer 27 of the supply pipe from the gas pipe 22 to the reformer 30, and then to the anode of the fuel cell 40. The control valve 72 is attached to the purge pipe 70 and the control valve 76 is attached to the supply pipe to the anode of the fuel cell 40. When a purge instruction is issued, the purge process of FIG. 4 is executed instead of the purge process routine of FIG. In the fuel cell power generation system 20B of this embodiment , first, the supply of water vapor used for the reforming reaction is stopped (step S200), and the combustion unit 32 of the reformer 30 is stopped (step S202). Then, the control valve 28 and the control valve 76 are closed to seal the reformer 30 and the CO selective oxidation unit 34 (step S204), the control valve 72 and the control valve 48 are opened, and the control valve 47 is closed. Then, purge piping is formed (step S206), and the combustor 49 is operated (step S208). The city gas supplied from the gas pipe 22 and desulfurized by the desulfurizer 27 is supplied to the fuel cell 40 via the purge pipe 70, and the gas discharged from the anode side of the fuel cell 40 is supplied from the combustor 49. It is burned and exhausted. When the purge is started in this manner, the control valve 24 is closed after the time necessary for the purge has elapsed (step S210), and the supply of the city gas from the gas pipe 22 is temporarily stopped (step S212). Then, after waiting for a predetermined time until the temperature of the fuel cell 40 is lowered to some extent (step S214), an amount of city gas necessary for eliminating the negative pressure of the fuel cell 40 is supplied (step S216). ), This routine is terminated. Also in the fuel cell power generation system 20B of such an embodiment, the fuel cell 40 can be purged using city gas as a reforming raw material. In this embodiment , the reformer 30 is not purged. This is because the reformer 30 does not necessarily need to be purged.
[0036]
In the fuel cell power generation system 20 of the reference example and the fuel cell power generation system 20B of the example , the city gas (13A) is used as the reforming raw material and the purge gas, but the city gas (12A) or the gas cylinder is filled. The propane gas may be used as a reforming raw material and as a purge gas. The reforming raw material used as the purge gas is not limited to city gas or propane gas, and any hydrogen-sensitive fuel may be used as long as it is a gas at room temperature.
[0037]
In the fuel cell power generation system 20 of the reference example and the fuel cell power generation system 20B of the embodiment , the direct current power from the fuel cell 40 is converted by the DC / DC converter 52 and the inverter 54 and the power line 12 from the commercial power supply 10 to the load 16 is converted. However, the method of using the DC power from the fuel cell 40 is not limited to this, and any method may be used.
[0038]
In the fuel cell power generation system 20 of the reference example and the fuel cell power generation system 20B of the embodiment, the water heated using the heat of the fuel cell 40 is stored in the hot water tank 44, but the hot water tank 44 is not provided. It does not matter.
[0039]
The fuel cell power generation system 20 of the reference example and the fuel cell power generation system 20B of the embodiment include the desulfurizer 27 that removes the sulfur content of the city gas. However, when the city gas does not include the sulfur content, the desulfurizer is used. 27 need not be provided.
[0040]
As described above, the embodiments of the present invention have been described using the reference examples and examples . However, the present invention is not limited to these examples, and various modifications can be made without departing from the scope of the present invention. Of course, it can be implemented in the form.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system 20 which is a reference example of the present invention.
FIG. 2 is a flowchart showing an example of a purge process routine executed by the electronic control unit 60.
3 is a block diagram showing a schematic configuration of a fuel cell power generation system 20B examples.
4 is a flowchart showing an example of the purge processing routine executed in the fuel cell power generation system 20B examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Commercial power supply, 12 Electric power line, 14 Circuit breaker, 16 Load, 18 Circuit breaker, 20, 20B Fuel cell power generation system, 22 Gas piping, 24, 28 Control valve, 23, 26 Booster pump, 27 Desulfurizer, 30 Reformation , 32 Combustion unit, 34 CO selective oxidation unit, 36 Water tank, 37 Evaporator, 38 Control valve, 40 Fuel cell, 41 Blower, 42 Heat exchanger, 43 Circulation pump, 44 Hot water storage tank, 46 pump, 52 DC / DC converter, 54 inverter, 55 circuit breaker, 56 DC / DC converter, 58 load power meter, 60 electronic control unit, 62 CPU, 64 ROM, 66 RAM, 68 timer, 70 purge piping 70, 72, 76 control valve.

Claims (7)

Reforming means for reforming gaseous hydrocarbon fuel into hydrogen-rich fuel gas;
A fuel cell that generates power using the fuel gas supplied from the reforming means;
A branch pipe for branching from a fuel supply pipe for supplying hydrocarbon fuel to the reforming means and for supplying hydrocarbon fuel to the anode side of the fuel cell;
An openable and closable control valve provided in the branch pipe;
When the predetermined purge instruction is given , the control valve is opened, and after the control valve is opened, the control valve is closed after waiting for a time necessary for purging the fuel cell to elapse. The supply of hydrocarbon fuel to the fuel cell is temporarily stopped, and after the predetermined time has elapsed since the supply of the hydrocarbon fuel is temporarily stopped, the control valve is opened to eliminate the negative pressure of the fuel cell. Control means for supplying the fuel cell with a hydrocarbon-based fuel necessary for
A fuel cell power generation system comprising:   The fuel cell power generation system according to claim 1, wherein the hydrocarbon fuel is city gas. A fuel cell power generation system according to claim 2,
A desulfurization means attached to the fuel supply pipe to remove the sulfur content of the city gas;
The branch pipe is a pipe branched on the downstream side of the desulfurization means of the fuel supply pipe.
Fuel cell power generation system.   The fuel cell power generation system according to any one of claims 1 to 3, further comprising combustion means for combusting combustible components in exhaust gas discharged at the time of purging performed in accordance with the predetermined purge instruction.   The fuel cell power generation system according to claim 4, wherein the combustion means is means capable of combusting a hydrocarbon-based fuel used for purging. The fuel cell power generation system according to any one of claims 1 to 5, further comprising power conversion supply means capable of converting DC power from the fuel cell into desired power and supplying the power supply line from another system power supply to a load. The fuel cell power generation system according to any one of claims 1 to 6, further comprising hot water storage means for storing hot water that is heated using at least heat from the fuel cell.

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