JPS63254677A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To decrease the thermal stress of the constituting equipment materials due to the temperature difference between the reaction gas and the inactive gas and prevent the life reduction and performance deterioration by adjusting the temperature of the inactive gas purging the reaction gas in response to the system condition. CONSTITUTION:The temperature of the inactive gas purging the reaction gas is adjusted by the high-temperature exhaust gas of an air feeding device 19 in a heat exchanger 29. Under the power generation stand-by condition, an oxidizer gas purge valve 27 is opened, and the inactive gas is fed to the oxidizer electrode 11B of a fuel cell 11. Under the stop operation condition, a raw fuel purge valve 25, a fuel gas purge valve 26, and the valve 27 are opened, and the inactive gas is fed to a fuel reforming device 5, the fuel electrode 11A of the cell 11, and the oxidizer electrode 11B. Since the temperature of the inactive gas is adjusted, its temperature difference with the oxidizer gas which is the reaction gas is decreased. The thermal stress applied to the constituting equipment materials is thereby decreased, and the life reduction and performance deterioration is prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel cell power generation system comprising a fuel cell, a fuel reformer, and an air supply device, and particularly relates to a fuel cell power generation system comprising a fuel cell, a fuel reformer, and an air supply device. A fuel cell power generation system capable of preventing performance deterioration of fuel cell constituent materials and system constituent equipment materials due to thermal stress due to temperature difference between zero reaction gas and inert gas when purging with inert gas. .

(Prior Art) Fuel cells are conventionally known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell usually has a pair of electrodes, a fuel electrode and an oxidizer electrode, with an electrolyte layer in between, and a fuel gas such as hydrogen gas is supplied to the fuel electrode, and an oxidant gas such as air is supplied to the oxidizer electrode. The system uses the electrochemical reaction that occurs at this time to extract electrical energy from between the two electrodes, and as long as the fuel gas and oxidant gas are supplied, electrical energy can be extracted with high conversion efficiency. It is something that can be taken out.

Currently, fuel cells that are being considered include fuel cells that use hydrazine as fuel, alkaline aqueous electrolytes, and phosphoric acid aqueous electrolytes as electrolytes. Among these, fuel cells that use phosphoric acid aqueous electrolytes as electrolytes Since it can use reformed gas, it can be used in general, and it is being used for industrial purposes and power generation projects. This type of fuel cell is equipped with a fuel reformer to obtain reformed gas containing a large amount of hydrogen gas, which is the fuel gas, and an air supply device to obtain compressed air, which is the oxidant gas. It often constitutes a battery power generation system.

FIG. 3 shows an example of this type of conventional fuel cell power generation system. In FIG. 3, a raw fuel 1 made of fossil fuel such as natural gas or coal gas and steam from a steam supply device 2 are supplied to a raw fuel flow rate control valve 3, respectively.
The steam is introduced into the reforming reaction tube 6 in the fuel reformer 5 after being controlled by the steam flow control valve 4 so that the molar ratio of steam to carbon is about 3 to 5. Here, the raw fuel 1 and steam are heated to about 500 to 600° C. to perform a reforming reaction, and then pass through a shift converter 7 to become a reformed gas with a high hydrogen content, that is, a fuel gas. This fuel gas with a high hydrogen content is sent to the fuel gas steam/water separator 8 to remove surplus steam from reforming, and then sent to the auxiliary burner 9 via the auxiliary burner fuel gas flow control valve 10. ,
Further, the fuel gas flow m is sent to the fuel electrode 11A of the fuel cell 11 with its flow rate controlled by the control valve 12.

Hydrogen in the fuel gas that has flowed into the fuel electrode 11A of the fuel cell 11 undergoes a catalytic reaction with oxygen in the oxidant gas that has flowed into the oxidizer electrode 11B of the fuel cell 11, and as a result, a portion of the fuel gas is Electrical energy and reaction water are obtained by being consumed. The fuel exhaust gas that exits the fuel electrode 11A and contains a part of the reaction water generated in the fuel cell 11 is sent as fuel gas to the main burner 13 of the fuel reformer 5, but on the way, the gas The fuel exhaust gas is passed through a steam/water separator 16 to recover moisture therein. The fuel exhaust gas sent to the main burner 13 is combusted in the fuel reformer 5, heats the reforming reaction tube 6, and is then discharged as high-temperature exhaust gas 17. Furthermore, this high temperature exhaust gas 17 is transferred to the fuel cell 1
After combining with the oxidant exhaust gas sent from the oxidizer electrode 11B, it is introduced into the mixer 18, and is used as part of the energy for driving the air supply device 19 consisting of the turbine 19A and the compressor 19B. On the other hand, the fuel gas sent to the auxiliary burner 9 is combusted within the auxiliary burner 9, and the combustion gas passes through the mixer 18 to drive the turbine 19A of the air supply bag @19.

On the other hand, the air discharged from the compressor 19B connected to and driven by the turbine 19A is sent to the auxiliary burner 9, the main burner 1
3 to each auxiliary burner oxidant gas flow rate control valve 20. Air and fuel are adjusted and sent by the main burner oxidant gas flow rate control valve 21, and are also sent to the oxidant electrode 11B of the fuel cell 11 by the oxidant gas flow rate control valve 22, and the surplus is used to drive one air supply device. It is sent to the mixer 18 as part of the energy.

A part of the oxidant gas that has flowed into the oxidizer electrode 11B of the fuel cell 11 is consumed by reacting with hydrogen in the fuel gas that has flowed into the fuel electrode 11A of the fuel cell 11.
It is discharged containing the water produced in B. This discharged oxidizer exhaust gas is converted into high-temperature exhaust gas from the fuel reformer @5 after partially condensing the steam content in the oxidizer exhaust gas in the oxidizer exhaust gas steam water separator 23 in the same manner as the above-mentioned fuel exhaust gas. Join up with 17.

In this way, fuel type) I! ! At No. 11, electrical energy is generated by a catalytic reaction between hydrogen in the fuel electrode 11A and oxygen in the oxidizer electrode 11B so that the oxidizer electrode 11B becomes a positive electrode and the fuel electrode 11A becomes a negative electrode, and this electrical energy is used as an electrical load. 24.

On the other hand, the raw fuel supply line, the fuel 1i1 of the fuel cell 11
The fuel gas supply line to the oxidizer electrode 1A and the oxidizer gas supply line to the oxidizer electrode 11B are connected to a raw fuel purge valve 25. Fuel gas purge valve 26. An inert gas such as nitrogen gas is supplied through the oxidizing gas purge valve 27 to prevent mixing of the fuel gas and the oxidizing gas when the fuel cell power generation system is stopped or in a stopped operation state or in a power generation standby state. is replaced with inert gas.

By the way, in such a fuel cell power generation system,
In order for the fuel cell 11 to operate stably for a good period,
It is desirable that the temperature change of the gas or cooling water supplied to the fuel cell 11 be as small as possible to reduce thermal stress on the constituent materials of the fuel cell 11, and the temperature of the fuel cell 11 in standby state for power generation should be increased within one hour. The temperature of the cooling water of the fuel cell 11 is adjusted so that the temperature is 40 to 50°C. On the other hand, when transitioning from the power generation state to the power generation standby state (state in which fuel gas is supplied to the fuel electrode 11A and inert gas is supplied to the oxidizer electrode 11B), or from each of the above states to the stop operation state When moving to the next stage, the residual gas is purged using the following procedure.

(a) Transition from power generation state to power generation standby state The oxidizing gas flow rate control valve 22 is fully closed, and immediately after that, the oxidizing gas purge valve 27 is opened to supply inert gas from the inert gas supply device 28.

(b) Transition from power generation standby state to stop operation state The fuel gas flow rate control valve 12 is fully closed, and immediately after that, the fuel gas purge 2
6 is opened and inert gas is supplied from the inert gas supply device 28 (the oxidizer electrode 118 continues to be in that state since it has been switched to inert gas).

(C) Transition from power generation state to stop operation state (a>
In addition to the operations in (b), the raw fuel flow control valve 3 and the steam flow rate control valve 4 are fully closed, and immediately after that, the raw fuel purge valve 25 is opened to supply inert gas from the inert gas supply bag @28. supply.

Through this procedure, residual gas is purged using an inert gas.

However, compared to the operating humidity of the fuel cell 11, the supply gas temperature of the oxidant gas and fuel gas is
．． The heat of compression in 9B and the heat of burner combustion in the fuel reformer 5 are adjusted to be almost the same during the process, but the inert gas supplied from the inert gas supply device 28 is For example, in the case of nitrogen gas, since liquid nitrogen is used after being vaporized in an evaporator, the gas concentration is at room temperature, and there is a large difference in gas temperature before and after purging. In particular, when transitioning from a load operating state to a power generation standby state, fuel gas at about 200'C flows through the fuel electrode 1A, and the oxidizer electrode 11
A phenomenon occurs in which inert gas at room temperature flows through B.

As a result, as the system repeatedly generates and stops power generation, a sudden temperature difference in the supply gas occurs in the fuel cell 11, which increases the deterioration of the constituent materials of the fuel cell 11 due to thermal stress, which may shorten the battery life. There is a problem that there is. Also, similar to the problem of the fuel cell described above, the fuel reformer 5 through which the inert gas passes. Transformer 7. Similarly, sudden temperature differences occur in the materials of system components such as the steam/water separators 16 and 23, resulting in performance deterioration due to thermal stress.

(Problems to be solved by the invention) Conventional fuel cell power generation systems have the above-mentioned problems, and it is desirable to solve them in some way.
For example, to heat by installing a heating device such as an electric heater,
A large-capacity heater and a temperature control device are required, resulting in a decrease in system efficiency and a complicated system configuration.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to reduce the temperature difference between fuel cell constituent materials and An object of the present invention is to provide a fuel cell power generation system that can reduce thermal stress in system component materials and prevent shortened lifespan and performance deterioration.

[Configuration of the Invention (Means for Solving Problems)] In order to achieve the above object, the present invention includes a fuel reformer, an air supply device, a fuel cell, a fuel reformer, and a fuel cell. In the above-mentioned fuel cell power generation system configured with an inert gas supply device that supplies inert gas to the fuel electrode and the oxidizer electrode, each of the inert gas supply devices supplies inert gas to each supply line from the inert gas supply device. A temperature control means for adjusting the temperature of the inert gas flowing through the line is provided on the common line of the line, and further on the line that supplies the inert gas to the raw fuel supply line to the fuel reformer,
The raw fuel purge valve, which opens when the system is in a stopped state,
On the line that supplies inert gas to the fuel gas supply line to the fuel electrode, install a fuel gas purge valve that opens when the system is in a stopped state, and supply inert gas to the oxidant gas supply line to the oxidizer electrode. The present invention is characterized in that oxidant gas purge valves are provided on the lines that open when the system is in a stopped operation state and when the system is in standby state for power generation.

(Function) In the above-described fuel cell power generation system, the temperature of the inert gas, which is a temperature regulating medium, is controlled by the temperature regulating means.

When the system is in standby mode for power generation, the oxidant gas barge valve is opened to supply temperature-controlled inert gas to the oxidizer electrode of the fuel cell through the oxidant gas supply line, and when the system is in the standby state, the oxidant gas is supplied to the oxidizer electrode of the fuel cell. Fuel purge valve.

By opening the fuel gas purge valve and the oxidant gas purge valve, the humidity-controlled inert gas is passed through the raw fuel supply line to the fuel reformer, and through the fuel gas supply line to the fuel electrode of the fuel cell. The oxidizer electrodes of the fuel cell are each supplied through supply lines. Therefore, the inert gas for purging the remaining gas from the power generation state to the power generation standby state or stop state is supplied to the fuel cell and fuel reformer after the temperature is adjusted in advance using the high temperature gas in the system. This means that the temperature difference between the reaction gas and the inert gas when purging the reaction gas with the inert gas can be reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows in block form an example of the configuration of a fuel cell power generation system according to the present invention. The same parts as in FIG. I will only talk about.

That is, in the fuel cell power generation system shown in FIG. 3 described above, FIG. 1 shows a common line for supplying inert gas from the inert gas supply device 28 to each supply line. For example, two heat exchangers are provided as temperature regulating means for regulating the temperature of the inert gas. Here, the heat exchanger 29 is configured to introduce, for example, combustion exhaust gas from the turbine 19A of the air supply bag fiW19 into its primary side as high-temperature gas in the system, and to introduce inert gas into its secondary side. There is. In addition, the raw fuel purge valve 25, which is installed on the line that supplies inert gas to the raw fuel supply line to the fuel reformer vl@5, is opened when the system is in a stopped operation state, and is used to supply fuel to the fuel electrode. The fuel gas purge valve 26, which is provided on the line that supplies inert gas to the fuel gas supply line of the oxidant electrode, opens when the system is in a stopped operation state, and is further provided on the line that supplies the oxidant gas to the oxidizer electrode. Oxidizing gas purge valve 27 provided on the line that supplies inert gas
are opened when the system is in a stop operation state and in a power generation standby state.

Next, the temperature increasing effect of the fuel reformer in the fuel cell power generation system configured as described above will be described.

Now, the inert gas supplied from the inert gas supply device 28 is introduced into the secondary side inlet of the heat exchanger 29 at approximately room temperature. On the other hand, the combustion gas of the auxiliary burner 9 and the mixer 18
The gas flowing into the air supply device 19A
Even if you drive it, it is still in a high temperature state of 400 to 500 degrees Celsius,
This high temperature combustion exhaust gas is introduced into the primary side of the heat exchanger 29.

As a result, in the two heat exchangers, the low-temperature inert gas and the high-temperature combustion exhaust gas exchange heat, and the temperature of the inert gas increases, and the temperature of the combustion exhaust gas decreases, and the heat exchanger 29 is discharged from each outlet.

The inert gas discharged from the heat exchanger 29 is transferred to the oxidizing gas purge valve 27 when the system is in standby mode for power generation.
When the oxidant gas is opened, the oxidant gas is supplied into the oxidant electrode 11B of the fuel cell 11 through the oxidant gas supply line. Also,
When the system is in a shutdown state, the air treatment device @19 is stopped, but the inert gas exchanges heat with the residual heat of the combustion exhaust gas in the same manner as described above. At this time, the raw fuel purge valve 25. Fuel gas purge valve 26. Oxidizing gas purge valve 2
7 open, the inert gas passes through the raw fuel supply line to the fuel reformer 5.

The fuel electrode 11A and the oxidizer electrode 11 of the fuel cell 11 are passed through the fuel gas supply line and the oxidant gas supply line.
B is supplied respectively. Furthermore, the combustion exhaust gas discharged from the heat exchanger 29 is released into the atmosphere.

As mentioned above, the fuel cell power generation system of this example has the following features:
A heat exchanger 29 as a temperature adjustment means for adjusting the temperature of the inert gas flowing through the common line is installed on the common line of each line that supplies inert gas from the inert gas supply device 28 to each supply line. Furthermore, a fuel reformer 5 is provided.
On the line that supplies inert gas to the raw fuel 1 supply line.

Raw fuel purge valve 25 that opens when the system is in a stop operation state
A fuel gas purge valve 26, which is opened when the system is in a stopped operation state, is installed on the line that supplies inert gas to the fuel gas supply line to the fuel electrode 11A of the fuel cell 11, and also connects the oxidizer to the oxidizer electrode 11B. An oxidizing gas purge valve 2 is provided on the line that supplies inert gas to the gas supply line, which opens when the system is in a stopped operation state and in a standby state for power generation.
7 are provided respectively.

Therefore, when the fuel cell power generation system is in standby state (yo,
Since the inert gas can be heated to about 200'C with the high temperature combustion exhaust gas from the turbine 19A of the air supply device 19,
When the system transitions from a power generation standby state to a power generation state or from a power generation state to a power generation standby state, the temperature difference between the temperature of the oxidizing gas, which is a reactive gas, and the temperature of the inert gas becomes small. This reduces the thermal stress applied to the constituent materials of the fuel cell 11 and the materials of the system constituent devices such as the fuel reformer 5, making it possible to prevent the aforementioned reduction in life and performance deterioration. Furthermore, when the fuel cell power generation system is in a stopped operation state, the temperature of the inert gas gradually decreases as the temperature of the high-temperature combustion exhaust gas from the turbine 19A of the air supply device 19 decreases, so that the temperature can be gradually decreased.

This makes it possible to obtain the same effect as in (e) above. Furthermore, the inert gas, which is the temperature regulating medium of the fuel reformer 5 and the fuel cell 11, is preheated with the high-temperature combustion exhaust gas from the turbine 19A, which conventionally was wasted in large quantities into the atmosphere. Therefore, it is possible to improve the thermal efficiency of the entire system.

Next, other embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows in block form another example of the configuration of the fuel cell power generation system according to the present invention, and the same parts as in FIG. Only the different parts will be described.

That is, FIG. 2 shows the heat exchanger 2 in FIG.
As the high temperature gas on the primary side of 9, instead of the combustion exhaust gas from the turbine 19A of the air supply device 19, the fuel reformer 5
The combustion exhaust gas (at a high temperature of 300 to 400°C) is introduced into the mixer 18, and the combustion exhaust gas after heat exchange is introduced into the mixer 18. Also in this embodiment, the inert gas is heated by the combustion exhaust gas from the fuel reformer 5 in the same manner as described above, and the same effects as in the above-mentioned embodiments can be obtained.

It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without changing the gist thereof.

For example, in each of the embodiments described above, a heat exchanger is used as a temperature control means for raising the temperature of the inert gas, but it goes without saying that other temperature control means may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the temperature of the inert gas for purging residual gas becomes approximately the same temperature as the reactant gas when the system is on standby for power generation, and gradually increases when the system is in the stopped operation state. 1 Fuel cell constituent materials and system configuration due to the temperature difference between the reactant gas and the inert gas when purging the reactant gas with an inert gas, so that the temperature is appropriately adjusted according to the system state. It is possible to provide a fuel cell power generation system that can reduce thermal stress in equipment materials and prevent shortened lifespan and performance deterioration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the fuel cell power generation system according to the present invention, FIG. 2 is a block diagram showing another embodiment of the fuel cell power generation system according to the present invention, and FIG. 3 is a block diagram showing a conventional fuel cell power generation system. FIG. 1 is a block diagram showing an example of a system. DESCRIPTION OF SYMBOLS 1... Raw fuel, 2... Steam supply device, 3... Raw fuel flow rate control valve, 4... Steam flow rate control valve, 5...
・Fuel reformer, 6... Reforming reaction tube, 7... Shift converter, 8... Fuel gas steam separator, 9... Auxiliary burner,
10... Auxiliary burner fuel gas flow layer control valve, 11...
Fuel cell, 11A...Fuel electrode, 11B...Oxidizer electrode, 12...Fuel gas flow rate control valve, 13...Main burner, 16...Fuel exhaust gas air/water separator, 17... High temperature exhaust gas, 18... Mixer, 19... Air supply device, 1
9A...Turbine, 19B...Compressor, 20
... Auxiliary burner oxidizing gas flow rate control valve, 21... Main burner oxidizing gas flow rate control valve, 22... Oxidizing gas flow rate control valve, 23... Oxidizing exhaust gas steam/water separator, 24.
... Electrical load, 25 ... Raw fuel purge valve, 26 ...
Fuel gas purge valve, 27... Oxidizer gas purge valve, 2
8...Inert gas supply device, 2...Heat exchanger.

Claims (4)

[Claims] (1) A mixed gas of raw fuel and steam is introduced into the reforming reaction tube in which a reforming reaction catalyst layer is provided, and combustion fuel and combustion air are introduced into the combustion chamber outside the reforming tube. a fuel reformer that generates reformed gas by circulating high-temperature combustion gas obtained by combustion; an air supply device that is composed of a turbine and a compressor and obtains compressed air by compressing air in the atmosphere; The reformed gas from the fuel reformer is introduced into the fuel electrode as a fuel gas, and the compressed air from the air supply device is introduced into the oxidizer electrode as an oxidant gas, and the electrochemical reaction that occurs at this time causes a gap between the two electrodes. A fuel cell that extracts electrical energy from the fuel cell, a raw fuel supply line to the fuel reformer, a fuel gas supply line to the fuel electrode, and an oxidant gas supply line to the oxidizer electrode are connected through different lines, respectively. and an inert gas supply device that supplies inert gas to the fuel cell, and introduces exhaust gas discharged from the fuel electrode of the fuel cell as combustion air to the fuel reformer, and also introduces exhaust gas from the oxidizer electrode In a fuel cell power generation system in which exhaust gas is introduced as part of energy for driving the air supply device, a common fuel cell for each line that supplies inert gas from the inert gas supply device to each supply line. installed on the line,
A temperature control means for regulating the temperature of the inert gas flowing through the line, and a temperature control means provided on the line for supplying the inert gas to the raw fuel supply line to the fuel reformer, and a temperature control means for controlling the temperature of the inert gas flowing through the line, and a temperature control means for controlling the temperature of the inert gas flowing through the line. a fuel gas purge valve that is installed on a line that supplies inert gas to the fuel gas supply line to the fuel electrode and that opens when the system is in a stopped operation state; Installed on the line that supplies inert gas to the agent gas supply line,
A fuel cell power generation system comprising: an oxidizing gas purge valve that opens when the system is in a stopped operation state and in a power generation standby state. (2) The fuel cell power generation system according to claim (1), characterized in that a heat exchanger is used as the temperature control means. (3) The heat exchanger is characterized in that the combustion exhaust gas from the turbine of the air supply device is introduced into the primary side, and the inert gas is introduced into the secondary side. fuel cell power generation system. (4) The heat exchanger is characterized in that the combustion exhaust gas from the fuel reformer is introduced into the primary side and the inert gas is introduced into the secondary side. Fuel cell power generation system.