JP2003229156A - Fuel cell generating system and purge method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To purge rapidly without using a gas for exclusive use for purging. <P>SOLUTION: When a reformer 30 and a fuel cell 40 are purged at the stopping of the system, a control valve 38 is closed and supply of steam to the city gas as a reforming material supplied to the reformer 30 is stopped, and a control valve 47 is closed, and by opening a control valve 48, the gas pushed from the fuel cell 40 by the city gas is introduced into the combustor 48 and burned and exhausted. And after waiting the completion of purging of the reformer 30, a CO selective oxidation part 34, and the fuel cell 40, the control valve 28 is closed and the control valve 48 is opened, and the purge process is completed. Since the reformer 30 and the fuel cell 40 are purged using the city gas which is used for reforming material as a purging gas, it is not necessary to prepare a gas for exclusive use for purging. And since it is not necessary to carry out temperature control and moisture control to the city gas when used as a purging gas, rapid purging can be made. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system and a fuel cell purging method.

[0002]

2. Description of the Related Art Conventionally, as a method of purging a fuel cell of this type, a method of purging using a combustion gas has been proposed (for example, Japanese Patent Laid-Open No. 2000-243423). In this purging method, the anode off gas discharged from the cathode of the fuel cell is purged with a reducing atmosphere gas obtained by mixing and burning a gas containing hydrogen with 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 anode is held in a reducing atmosphere and the cathode is held in an oxidizing atmosphere for purging.

[0003]

However, in such a fuel cell purging method, it is necessary to adjust the temperature and the water content of the combustion gas, so that the purging requires a long time. In addition, the system becomes complicated because it is necessary to provide both a cathode off-gas combusting section that mixes and burns the cathode off-gas and an anode off-gas combusting section that mixes and burns the anode off-gas.

The fuel cell power generation system and the method of purging a fuel cell of the present invention have an object of purging without using a dedicated purging gas. Further, the fuel cell power generation system and the method of purging a fuel cell according to the present invention have an object of prompt purging. Another object of the fuel cell power generation system of the present invention is to simplify the equipment required for purging.

[0005]

Means for Solving the Problem and Its Action / Effect 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 objects.

The fuel cell power generation system of the present invention comprises a reforming means for reforming a gaseous hydrocarbon fuel into a hydrogen-rich fuel gas, and a fuel cell for generating electricity using the fuel gas supplied from the reforming means. And when a predetermined purge instruction is given,
And a purging means for purging the fuel cell with the hydrocarbon fuel.

In the fuel cell power generation system of the present invention,
When a predetermined purging instruction is given, the fuel cell is purged by using the gaseous hydrocarbon fuel as the reforming raw material used in the reforming means, so it is possible to perform the purging without using the exclusive purging gas. it can. As a result, the system can be made simpler than those using a dedicated purging gas and those used by burning off gas from the fuel cell. Moreover, since it is not necessary to adjust the temperature and water content of the hydrocarbon fuel, the purging can be completed quickly.

In the fuel cell power generation system of the present invention, the hydrocarbon fuel may be city gas. In this case, the desulfurization means for removing the sulfur content of the city gas may be provided, and the purging means may be means for purging using the city gas after being desulfurized by the desulfurization means.

In the fuel cell power generation system of the present invention,
Combustion means for burning combustible components in the exhaust gas discharged at the time of purging by the purging means may be provided. In this way, the combustible components in the exhaust gas discharged during purging can be burned and discharged. In the fuel cell power generation system of the present invention in this aspect, the combustion means may be means capable of burning the hydrocarbon fuel used for purging. In this way, the hydrocarbon fuel used for purging can be burned and exhausted. In the fuel cell power generation system of the aspect of the invention including such a 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. Can also be
In this case, it is not necessary to provide a dedicated combustion section used for the combustion of combustible components in the exhaust gas discharged during purging and the combustion of the hydrocarbon fuel used for purging. As a result, the system can be simplified.

In the fuel cell power generation system of the present invention,
The purging means may be means for purging the reforming means using the hydrocarbon fuel. In this way, the reforming means can also be purged.

In the fuel cell power generation system of the present invention in which the purging means also purges the reforming means, the purging means is a means for purging by flowing the hydrocarbon fuel in the order of the reforming means and the fuel cell. It can also be one. In this case, the flow path of the gas, which is the hydrocarbon-based fuel converted into the fuel gas by the reforming reaction and supplied to the fuel cell, can be used as it is as the purge flow path, so that it is not necessary to provide piping for purging. . As a result, the system can be simplified.

In the fuel cell power generation system of the present invention in which the purging unit also purges the reforming unit, the purging unit is configured to perform the purging after a predetermined time has elapsed after the purging of the reforming unit and the fuel cell is completed. It may be a means for supplementing the reforming means with a hydrocarbon fuel.
In this way, it is possible to prevent the reforming means from having a negative pressure when the temperature changes from a relatively high temperature state immediately after the completion of purging to a low temperature state. As a result, it is possible to prevent air from entering the reforming means.

In the fuel cell power generation system of the present invention,
It is also possible to provide a power conversion and supply means capable of converting DC power from the fuel cell into desired power and supplying the power to a power supply line from another system power source to the load. In this way, it is possible to additionally supply electric power together with the other system power supply.

In the fuel cell power generation system of the present invention,
It is also possible to provide a hot water storage means for storing at least water heated by using heat from the fuel cell.
In this way, the heat from the fuel cell can be used, and the energy efficiency of the system can be improved. Needless to say, heat other than heat from the fuel cell may be used.

In the method of purging a fuel cell of the present invention, a fuel cell that generates electricity using a hydrogen-rich fuel gas obtained by using a gaseous hydrocarbon fuel as a reforming raw material is purged using the hydrocarbon fuel. Is the gist.

According to the fuel cell purging method of the present invention, since the hydrocarbon fuel as the reforming raw material is used as the purging gas, it is possible to perform the purging without using a dedicated purging gas. Therefore, the equipment required for purging can be simplified as compared with the case where a dedicated purging gas is used and the case where the off gas from the fuel cell is burned and used. Moreover, since it is not necessary to adjust the temperature and water content of the hydrocarbon fuel, the purging can be completed quickly.

In such a fuel cell purging method of the present invention, the hydrocarbon fuel may be city gas. In the fuel cell purging method of this aspect of the invention, the fuel cell may be purged using the city gas after desulfurization.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to examples. FIG. 1 is a configuration diagram showing an outline of the configuration of a fuel cell power generation system 20 which is an embodiment of the present invention. As illustrated, the fuel cell power generation system 20 of the embodiment includes a reformer 30 that receives city gas (13A) from a gas pipe 22 and reforms the city gas into a hydrogen-rich reformed gas, and a reformer 30. A CO selective oxidizer 34 that reduces carbon monoxide in the gas to form a fuel gas; a fuel cell 40 that receives the supply of the fuel gas and air to generate electricity by an electrochemical reaction;
A heat exchanger 42 for exchanging heat between the cooling water of the fuel cell 40 and the low temperature water of the hot water storage tank 44, and DC / DC for adjusting the voltage and current of the DC power from the fuel cell 40 to convert it into a desired DC power. The converter 52 and the converted direct-current power are converted into alternating-current power having the same phase as the commercial power supply 10, and the commercial power supply 10
An inverter 5 that supplies power to the load 16 from the power supply to the load 16 through the circuit breaker 14 through the circuit breaker 55.
4 and a DC / DC converter 5 that functions as an auxiliary machine power source by stepping down a part of DC power whose voltage or current is adjusted
6, a load power meter 58 that detects the load power consumed by the load 16, and an electronic control unit 60 that controls the entire system.

The reformer 30 is connected to the control valve 2 from the gas pipe 22.
4, a booster pump 26, city gas supplied through a desulfurizer 27 for removing sulfur, and a control valve 28, and water vapor whose flow rate is adjusted by a control valve 38 from a water tank 36 through an evaporator 37. A hydrogen-rich reformed gas is generated by the steam reforming reaction and the shift reaction of the following equations (1) and (2). The reformer 30 is provided with a combustion section 32 that supplies heat necessary for such a reaction.
The city gas is supplied from the gas pipe 22 through the control valve 24 and the booster pump 23. Also,
The exhaust gas on the anode side of the fuel cell 40 is supplied to the combustion section 32, and 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 the predetermined amount,
By operating the valves 47 and 48, a part or all of the anode off-gas can be guided to the combustor 49 and burned and exhausted.

[0020]

[Equation 1] CH ₄ + H ₂ O → CO + 3H ₂ (1) CO + H ₂ O → CO ₂ + H ₂ (2)

The CO selective oxidation section 34 receives a supply of air from a pipe (not shown) and selectively oxidizes carbon monoxide in the presence of hydrogen to selectively oxidize carbon monoxide (for example, a catalyst of an alloy of platinum and ruthenium). Thus, the carbon monoxide in the reformed gas is selectively oxidized to form a hydrogen-rich fuel gas having an extremely low carbon monoxide concentration (about several ppm in the embodiment).

The fuel cell 40 comprises an electrolyte membrane, an anode electrode and a cathode electrode sandwiching the electrolyte membrane, a fuel gas and air supplied to the anode electrode and the cathode electrode, and a separator forming a partition between the cells. The fuel cell is configured as a solid polymer fuel cell in which a plurality of single cells are laminated, and power is generated 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 has a flow path of circulating cooling water, and is kept at an appropriate temperature (about 80 to 90 ° C. in the embodiment) by circulating the cooling water. A heat exchanger 42 is provided in the cooling water circulation passage, 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 to heat the hot water storage tank. Hot water is stored in 44.

The output terminal (not shown) of the fuel cell 40 is D
C / DC converter 52, inverter 54, circuit breaker 55
Power line 12 from commercial power supply 10 to load 16 via
The DC power from the fuel cell 40 is converted into AC power having the same phase as that of the commercial power supply 10 and the commercial power supply 10 is connected.
It can be supplied to the load 16 by being added to the AC power from. 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 will be omitted. The load 16 is connected to the power line 12 via a circuit breaker 18.

The power line branched from the output side of the DC / DC converter 52 functions as a DC power source for supplying DC power to the actuator of the control valve 24 and auxiliary equipment such as the booster pumps 26, 28, the blower 41, and the pump 46. DC to
The / DC converter 56 is connected.

The electronic control unit 60 is configured as a microprocessor centered on a CPU 62, and has a C
ROM 64 for storing processing programs in addition to PU 62
And a RAM 66 for temporarily storing data, and an input / output port and a communication port (not shown). The electronic control unit 60 includes an output current i and a voltage V from a current sensor and a voltage sensor (not shown) in the inverter 54, a load power Po from a load power meter 58, a reformer 30, a CO selective oxidation unit 34, a fuel cell. Each temperature and the like from a temperature sensor (not shown) attached to 40 is input through the input port. Further, from the electronic control unit 60, the actuators of the control valves 24 and 28 and the boost pumps 23 and 26,
Drive signals to the blower 41, the circulation pump 43, the pump 46, etc., an ignition signal to the combustion section 32, a drive signal to the valves 47 and 48, a control signal to the DC / DC converter 52 and the DC / DC converter 56, and an inverter 54. A switching control signal to the circuit breaker, a drive signal to the circuit breaker 55, etc. are output via the output port.

Next, the operation of the fuel cell power generation system 20 thus constructed, particularly the purging operation when the system is stopped will be described. FIG. 2 shows an electronic control unit 60
5 is a flowchart showing an example of a purge processing routine executed by This routine is executed when the circuit breaker 55 cuts off the commercial power source 10 side and the purge instruction is issued after turning off the inverter 54.

When this purging routine is executed,
The CPU 62 of the electronic control unit 60 first sets the control valve 3
8 is closed and the evaporator 37 is stopped to stop the supply of steam used in the reforming reaction (step S1).
00), the control valve 47 is closed and the control valve 48 is opened to switch the anode off-gas combustion path for purging (step S102), and the combustor 49 is operated (step S104). 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 steam to the reformer 30 and the combustion part 32 of the reformer 30. Reformer 3 without reaction
0, the CO selective oxidizer 34, and the fuel cell 40 flow in this order while pushing out the 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, burned, and exhausted.

After the above processing is performed and the time required for purging elapses (step S108), the control valve 28 and the control valve 48 are closed and the fuel gas from the reformer 30 to the fuel cell 40 is closed. Close the system (step S11)
0). Here, the time required for purging depends on the reformer 30 and C
This is the time required to replace the gas in the O selective oxidation unit 34 and the fuel cell 40 with city gas, and the supply flow rate of the city gas, the reformer 30, the CO selective oxidation unit 34, the capacity of the fuel cell 40, and the fuel gas. It can be set according to the capacity of system piping.

When the fuel gas system is sealed, wait for a predetermined time after the fuel gas system is sealed (step S1).
12) Then, a predetermined amount of city gas is supplied to the reformer 30 (step S114), and this routine ends. Here, the predetermined time is set as the time required for the temperature of the reformer 30 to decrease to some extent. As described above, the reason why the city gas is supplied to the reformer 30 by a predetermined amount after the temperature of the reformer 30 becomes low is to alleviate the negative pressure of the reformer 30 caused by the decrease in temperature. is there.

According to the fuel cell power generation system 20 of the embodiment described above, the reformer 30 and the fuel cell 40 are purged by using the city gas as the reforming raw material as the gas for purging, and therefore, the purge gas is exclusively used for purging. No need to prepare gas.
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 piping for purging. As a result, the system can be simplified. Further, since it is not necessary to adjust the temperature and the water content of the city gas used as the purging gas, the purging can be performed quickly.

According to the fuel cell power generation system 20 of the embodiment, after the reformer 30 and the fuel cell 40 are purged with city gas, the temperature of the reformer 30 is waited until it becomes low to some extent and the city gas is removed. Since it is supplied to the reformer 30, the reformer 3
The negative pressure of 0 can be relieved. As a result, the reformer 3
It is possible to prevent the outside air from being mixed into 0.

In the fuel cell power generation system 20 of the embodiment,
A predetermined amount of city gas is supplied to the reformer 30 when a predetermined time has passed after the completion of purging, but the predetermined amount is detected when the temperature of the reformer 30 becomes lower than a predetermined temperature. The city gas may be supplied to the reformer 30. Further, the number of times the city gas is supplied to the reformer 30 after the purging is completed is not limited to once, and the city gas may be supplied to the reformer 30 a plurality of times after the completion of the purging.

Further, the fuel cell power generation system 20 of the embodiment
Then, it is assumed that a predetermined amount of city gas is supplied to the reformer 30 when a predetermined time has elapsed after completion of the purging.
When the airtightness of 0 is very high, the city gas may not be supplied to the reformer 30 after the completion of purging.

In the fuel cell power generation system 20 of the embodiment,
In the purging process, the gas extruded by the city gas and discharged from the fuel cell 40 was guided to the combustor 49 and burned and exhausted. Instead of the combustor 49, the combustor 3 of the reformer 30 is used.
It may be configured such that it is led to 2, burned and exhausted. In this way, it is not necessary to provide the combustor 49.

In the fuel cell power generation system 20 of the embodiment,
Although the reformer 30 and the fuel cell 40 are purged with city gas, only the fuel cell 40 may be purged with city gas. An outline of the configuration of the fuel cell power generation system 20B of this modification is shown in FIG. In the fuel cell power generation system 20B of this modified example, as shown in the drawing, the purging pipe 70 is branched to the anode of the fuel cell 40 at the post-stage side of the desulfurizer 27 of the supply pipe from the gas pipe 22 to the reformer 30. Control valve 7 connected to the purging pipe 70.
2 is attached and a control valve 76 is attached to the supply pipe to the anode of the fuel cell 40. When the purge instruction is given, 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 modification, first, the supply of steam used for the reforming reaction is stopped (step S200), and the combustion section 32 of the reformer 30 is stopped (step S202).
Then, the control valve 28 and the control valve 76 are closed to close 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, a pipe for purging 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 purging pipe 70, and the gas discharged from the anode side of the fuel cell 40 is discharged to the combustor 49. Burned and exhausted. After starting the purge in this way, wait until the time required for the purge has elapsed (step S210), and then the control valve 2
4 is closed to temporarily stop the supply of city gas from the gas pipe 22 (step S212). And the fuel cell 40
After waiting a predetermined time for the temperature of the fuel cell to drop to a certain extent (step S214), the amount of city gas required to eliminate the negative pressure of the fuel cell 40 is supplied (step S214).
216), and this routine ends. Even in the fuel cell power generation system 20B of such a modified example, the fuel cell 40 can be purged using city gas as a reforming raw material. In this modification, the reformer 30 is not purged. This is because the reformer 30 does not necessarily have to be purged.

In the fuel cell power generation system 20 of the embodiment and the fuel cell power generation system 20B of the modified example, the city gas (13
Although A) was used as the reforming raw material and as the purging gas, city gas (12A) or propane gas filled in the gas cylinder may be used as the reforming raw material and as the purging gas. The reforming raw material used as the purging gas is not limited to city gas or propane gas, and any hydrogen-sensitized fuel may be used as long as it is a gas at room temperature.

In the fuel cell power generation system 20 of the embodiment and the fuel cell power generation system 20B of the modified example, the DC power from the fuel cell 40 is converted by the DC / DC converter 52 and the inverter 54 to be transferred from the commercial power supply 10 to the load 16. It is assumed that the fuel cell 40 is supplied to the power line 12.
The method of using the DC power from the above is not limited to this, and any method may be used.

In the fuel cell power generation system 20 of the embodiment and the fuel cell power generation system 20B of the modified example, the water heated by using the heat of the fuel cell 40 is stored in the hot water storage tank 44. It does not matter if you do not have it.

The fuel cell power generation system 20 of the embodiment and the fuel cell power generation system 20B of the modified example are provided with the desulfurizer 27 for removing the sulfur content of the city gas, but when the city gas does not contain the sulfur content, Need not be equipped with a desulfurizer 27.

Although the embodiments of the present invention have been described with reference to the embodiments, the present invention is not limited to the embodiments and various embodiments are possible without departing from the gist of the present invention. Of course, it can be implemented in.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system 20 which is an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of a purge processing routine executed by an electronic control unit 60.

FIG. 3 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system 20B of a modified example.

FIG. 4 is a flowchart showing an example of a purge processing routine executed in a fuel cell power generation system 20B of a modified example.

[Explanation of symbols]

10 commercial power supplies, 12 power lines, 14 circuit breakers, 1
6 load, 18 circuit breaker, 20, 20B fuel cell power generation system, 22 gas pipe, 24, 28 control valve, 2
3,26 booster pump, 27 desulfurizer, 30 reformer,
32 combustion part, 34 CO selective oxidation part, 36 water tank, 37 evaporator, 38 control valve, 40 fuel cell, 4
1 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 / D
C converter, 58 load wattmeter, 60 electronic control unit, 62 CPU, 64 ROM, 66 RAM, 6
8 Timer, 70 Purge pipe 70, 72, 76 Control valve.

Continued front page    (72) Inventor Takeshi Masui             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Koichiro Hara             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Shinki Hattori             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Shogo Goto             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Takashi Ishikawa             Aichi, 2-chome, Asahi-cho, Kariya city, Aichi prefecture             Within Seiki Co., Ltd. (72) Inventor Shigenori Onuma             Aichi, 2-chome, Asahi-cho, Kariya city, Aichi prefecture             Within Seiki Co., Ltd. F-term (reference) 5H026 AA06                 5H027 AA06 BA01 BA08 BA16 DD01                       DD06 MM08 MM27

Claims (14)

[Claims] 1. A reforming means for reforming a gaseous hydrocarbon fuel into a hydrogen-rich fuel gas, a fuel cell for generating electricity using the fuel gas supplied from the reforming means, and a predetermined purge instruction. And a purge means for purging the fuel cell with the hydrocarbon-based fuel. 2. The fuel cell power generation system according to claim 1, wherein the hydrocarbon fuel is city gas. 3. The fuel cell power generation system according to claim 2, further comprising desulfurization means for removing a sulfur content of city gas, wherein the purging means uses the city gas after being desulfurized by the desulfurization means. A fuel cell power generation system that is a means of purging. 4. The fuel cell power generation system according to claim 1, further comprising a combustion unit that burns a combustible component in the exhaust gas discharged during the purging by the purging unit. 5. The fuel cell power generation system according to claim 4, wherein the combustion unit is a unit capable of burning the hydrocarbon fuel used for purging. 6. The fuel cell power generation system according to claim 4, wherein the combustion unit is a combustion unit provided in the reforming unit in order to obtain heat necessary for the reforming reaction in the reforming unit. 7. The purging means is means for purging the reforming means using the hydrocarbon fuel.
7. The fuel cell power generation system according to any one of 6 to 6. 8. The fuel cell power generation system according to claim 7, wherein the purging unit is a unit for flowing the hydrocarbon fuel in the order of the reforming unit and the fuel cell to purge the hydrocarbon fuel. 9. The purging means is means for replenishing the reforming means with the hydrocarbon fuel after a lapse of a predetermined time from completion of purging of the reforming means and the fuel cell. The fuel cell power generation system described. 10. The fuel according to claim 1, further comprising a power conversion / supply unit capable of converting DC power from the fuel cell into desired power and supplying the power to a power supply line from another system power supply to a load. Battery power generation system. 11. A hot water storage means for storing hot water which is heated using at least heat from the fuel cell.
11. The fuel cell power generation system according to any one of 1 to 10. 12. A method of purging a fuel cell, wherein a fuel cell for generating electric power using a hydrogen-rich fuel gas obtained by using a gaseous hydrocarbon fuel as a reforming raw material is purged using the hydrocarbon fuel. 13. The method of purging a fuel cell according to claim 12, wherein the hydrocarbon fuel is city gas. 14. The method of purging a fuel cell according to claim 13, wherein the fuel cell is purged using city gas after desulfurization.