JPH1167254A - Fuel cell power plant and start / stop operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent fuel cell power plant capable of preventing deterioration of a catalyst at the time of a start operation or a stop operation and stably maintaining the cell characteristics without deteriorating the cell characteristics, and a start thereof.・ Provide a stop operation method. SOLUTION: An inverter 16 and a dummy resistor 17 are connected between an anode 2 and a cathode 3 via an inverter switch 18 and a dummy resistor switch 19, respectively.
In addition, a voltage detector 20 is connected in parallel. An in-house power system 21 and an external load system 22 line are connected in parallel to the AC output line of the inverter 16, and are connected to be openable and closable via an in-house power system switch 23 and an external load system switch 24, respectively. Is done. Fuel cell body 1
Is provided with a temperature sensor 25 for measuring a temperature at a hot spot in the laminated single cell. The battery cooling water system 4, various valves and switches are controlled by the control device 26.

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 plant having improved temperature control for raising and lowering the temperature of a fuel cell and starting and stopping timings in a starting and stopping operation of a fuel cell, and a method for starting and stopping the fuel cell power plant.

[0002]

2. Description of the Related Art A fuel cell is a power generation apparatus that directly generates power by electrochemically reacting hydrogen obtained by reforming natural gas with oxygen in the air. It is characterized by high efficiency and excellent environmental harmony. Such a fuel cell is constituted by laminating a plurality of unit cells each composed of an electrolyte and an anode and a cathode of an electrode sandwiching the electrolyte, and among them, phosphoric acid is used as the electrolyte. This is a phosphoric acid fuel cell.

[0003] An example of a fuel cell power plant using such a phosphoric acid type fuel cell will be described below with reference to FIG. First, the unit cell of the fuel cell body 1, an anode 2 of contact fuel such as hydrogen H ₂ on the back, and a cathode 3 which oxidizing agents such as oxygen O ₂ is in contact with the back surface was impregnated with phosphoric acid It is configured by being arranged on both sides of a matrix (not shown) as a holding body. The anode 2 and the cathode 3, which are electrodes, are prepared by applying a catalyst such as platinum to one surface of a porous carbon plate.

[0004] In this case, only a pair of anodes 2 and cathodes 3 are schematically shown in the figure, but in practice, a unit cell comprising such anodes 2 and cathodes 3 is a separator which is a gas separation plate. The fuel cell main body 1 is formed by alternately stacking a plurality of fuel cell units 1 through.
Further, between the anode 2 and the separator and between the cathode and the separator, gas flow grooves for flowing the fuel and the oxidant as described above are formed. The temperature of the fuel cell body is controlled to a predetermined value by a battery cooling water system 4 that supplies cooling water.

A fuel reformer 5 is connected to a fuel supply path to the anode 2 in the fuel cell main body 1. The fuel reforming device 5 is provided with a reforming catalyst, and a natural gas containing hydrocarbons is passed through the reforming catalyst to reform the gas into a hydrogen-rich gas by a reforming reaction. 6 and a configuration in which natural gas is supplied via a fuel supply cutoff valve 7. A steam supply path 8 for supplying steam is connected to a natural gas supply path between the fuel supply cutoff valve 7 and the fuel reformer 5, and an anode N ₂ supply system 9 for supplying nitrogen N _2. Is connected. The anode N ₂ supply system 9 is provided with an anode N ₂ supply valve 10.

On the other hand, a blower 12 is connected to an oxidant supply system to the cathode 3 via an air supply cutoff valve 11. Here, a cathode N ₂ supply system 13 for supplying nitrogen N ₂ is connected to an air supply path between the air supply cutoff valve 11 and the cathode 3. The cathode N ₂ supply system 13 is provided with a cathode N ₂ supply valve 14.

The anode 2 in the fuel cell body 1
The gas exhaust path 15 of the cathode 3 is connected to the reformer burner 6. Further, in this fuel cell power plant, an inverter 16 and a dummy resistor 17 are connected in parallel between both electrodes, and are connected to be openable and closable via an inverter switch 18 and a dummy resistor switch 19, respectively. .

The operation of the above-described power plant of the phosphoric acid type fuel cell is as follows. First, the fuel cell body 1
Since there is a part in which a chemical reaction and an electrochemical reaction are performed, it is necessary to raise the temperature of such a reaction part to an allowable temperature range for the reaction before starting. This temperature raising operation is performed by raising the cooling water temperature of the battery cooling water system that controls the temperature of the fuel cell body.

Next, a mixed gas of natural gas and steam is supplied to the fuel reformer 5, and H 2 is produced by a steam reforming reaction.
₂ Rich gas is generated. This H ₂ rich gas is supplied to the anode 2. On the other hand, air compressed by the blower 12 is supplied to the cathode 3. Then, the H ₂ -rich gas supplied to the anode 2 and the compressed air supplied to the cathode 3 react electrochemically to generate air, water, and heat. The gas discharged from the anode 2 and the cathode 3 is supplied to the gas exhaust path 15
And is supplied to the reformer burner 6 via a combustion chamber, and is discharged into the atmosphere after combustion.

In the power generation stop operation, since the H ₂ rich gas of the anode 2 and the air of the cathode 3 supplied during the power generation operation remain, respectively, the nitrogen N ₂ which is an inert gas is supplied. , purge operation to drive out residual H ₂ rich gas and residual air are performed.
That is, in accordance with the power generation stop command, the fuel supply cutoff valve 7 and the air supply cutoff valve 11 are closed to cut off the supply of the H ₂ rich gas to the anode side and the supply of air to the cathode side. At the same time, the anode N ₂ supply valve 10 and the cathode supply valve 14 are opened, and nitrogen N ₂
Supply. Then, the H ₂ rich gas and air remaining on the anode 2 and the cathode 3 are expelled by the nitrogen N ₂ .

In the above-described phosphoric acid type fuel cell, when the battery voltage per unit cell is maintained at 0.8 V or more in a high temperature state, the noble metal catalyst on the electrode surface is eluted or coarsened and the active area is increased. It is known that a sintering phenomenon occurs in which the sintering phenomenon decreases, and such a sintering phenomenon deteriorates battery characteristics. In addition, when a reversal phenomenon occurs in which the battery voltage per unit battery becomes 0 V or less, the battery material is decomposed, and the battery is seriously damaged. For this reason, it is necessary to manage the battery voltage not only during power generation but also during a start / stop operation.

Further, during the start / stop operation, particularly during the stop operation, the above-described purge of the residual H ₂ rich gas and air is performed, and the battery voltage suppression control is performed.
That is, the inverter 16 responds to the A
When the C output is reduced to a very small output at which the operation of the inverter 16 becomes inoperable, the inverter switch 1
8 and the dummy resistor switch 19 are switched, and the dummy resistor 17 is turned on.

The dummy resistor 17 has an arbitrary voltage, for example, 0.
It is controlled so that it is turned on at 8 V / cell or more and opened at 0.5 V / cell or less. The battery voltage is suppressed by the dummy resistor 17 and the nitrogen N ₂ purge operation for the anode 2 and the cathode 3, and the management of the battery voltage during stoppage is completed.

[0014]

However, in the above-described phosphoric acid fuel cell power plant, there is a problem that the catalyst is deteriorated during the stop operation and the start operation, and the battery characteristics are deteriorated. This will be described below.

First, in the shutdown operation of the phosphoric acid fuel cell power generation plant, the anode 2 supplied during the power generation operation is supplied.
When the H ₂ -rich gas and the air of the cathode 3 are gas-replaced by supplying an inert gas, the delay time of the replacement differs between the single cells, and even a single cell differs depending on the position on the main surface. As a result, the single cell voltage decreases rapidly in a single cell or a single cell having a small replacement delay, whereas the residual voltage remains low in a single cell or a single cell having a large replacement delay. Since it takes time for the dummy resistor 17 to absorb the electrochemical energy of the H ₂ -rich gas and the air as the reaction gas, it takes time to lower the single cell voltage. That is, in a single cell or a portion of the single cell having a large replacement delay, a high generated potential, for example, until the electrochemical energy of rich gas and air is absorbed by the dummy resistor 17,
It will be exposed to 0.8V or more.

In this case, in the conventional shut-down method, the current during operation is cut off at an operating temperature of around 200 ° C., and gas replacement is performed at the same time. High temperature near 200 ℃ (around 200 ℃)
And a high potential (0.8 V / cell or more).

When the electrode catalyst layer is exposed to such a high temperature and a high potential, a so-called sintering phenomenon occurs in which the noble metal catalyst is eluted or coarsened as described above. It gradually decreases with each stop, and the deterioration of the electrode catalyst is accelerated. As a result, a decrease in the voltage-current characteristics, which is an output characteristic during the power generation operation, is promoted, which may adversely affect the life of the fuel cell. Further, since the resistance value of the dummy resistor 17 is determined by looking at the stacked fuel cell macro, the rise of the locally remaining single cell voltage is often not suppressed.

On the other hand, in the start-up operation of the phosphoric acid type fuel cell plant, during storage after the fuel cell is stopped, O _{2 in} the atmosphere diffuses into the anode 2 and the cathode 3 through the gas exhaust passage 15. By being adsorbed on the catalysts of the anode 2 and the cathode 3, the potential is maintained at a high value equal to or higher than a predetermined value, for example, 0.8 V or higher.

In this state, if the temperature rise accompanying the start-up operation is performed, the high potential (> 0.8 V / cell) is maintained in the high temperature state, so that the sintering phenomenon of the catalyst proceeds, and the catalyst active area decreases. This leads to deterioration of battery characteristics. In this case, since approximately the same O ₂ concentration remains in the anode 2 and the cathode 3 during the start-up operation, the anode 2 and the cathode 3 are kept at the same high potential. Since the battery voltage, which is the potential difference between the two, apparently satisfies a predetermined voltage value, the dummy resistor 17 turning-on control, which is a voltage suppression operation, is not performed.

On the other hand, according to the experiments conducted by the inventors, as shown in FIG. 8, when the electrode potential during the start / stop operation is out of the range of 0.3 V to 0.8 V, the battery voltage is increased with the start / stop operation. And the performance of the fuel cell is reduced. Thus, the lower limit potential of the electrode battery is 0.3 V even during the start / stop operation, and the O.D. The upper limit potential is set at 8 V, and the range between the upper limit potential is set as the allowable range of the electrode potential. However, as described above, when viewed microscopically with the time delay of the inert gas replacement, the current gas replacement method and the macroscopic control of sensing / applying the dummy resistor by sensing the voltage of the entire fuel cell body, It is extremely difficult to satisfy not only the upper limit potential but also the lower limit potential in a single cell or locally.

Further, if the temperature changes rapidly during the temperature raising and cooling operations at the time of starting and stopping, the volume of phosphoric acid in the fuel cell main body changes suddenly, so that the fuel cell stack member made of a porous material is not used. There is also a concern that the leakage of phosphoric acid, the movement of phosphoric acid between members, and the like may break the balance of phosphoric acid retention between the fuel cell stacked members determined by the design of the battery body, and adversely affect the battery life.

The present invention has been proposed to solve the above-mentioned problems of the prior art.
By providing an excellent fuel cell power plant and its start / stop operation method, which can prevent deterioration of the catalyst at the time of start operation or stop operation and can stably maintain without deteriorating the cell characteristics. is there.

[0023]

In order to achieve the above object, the invention according to claim 1 is directed to a fuel cell body comprising a plurality of unit cells each comprising a fuel electrode and an oxidant electrode, and a fuel cell body comprising: A fuel reforming device and an oxidizing agent supplying device for supplying fuel and an oxidizing agent to the main body, a battery cooling system for controlling the temperature of the fuel cell main body, an orthogonal transformation device connected to an output end of the fuel cell main body, In a start / stop operation method of a fuel cell power plant including an external load system switch that connects an orthogonal transformation device and an external load system, at the time of either one of a start operation and a stop operation of the fuel cell power plant, The method includes a step of performing an idle mode operation. Here, in the idle mode operation, the output of the fuel cell main body is supplied only to the in-house power system of the fuel cell power plant while the external load system switch is opened, so that the load of only the in-house power system is applied. It operates at the corresponding minimum load.

[0024] According to the eleventh aspect of the present invention, there is provided a fuel cell main body comprising a plurality of unit cells each comprising a fuel electrode and an oxidant electrode, and a fuel reformer for supplying fuel and an oxidant to the fuel cell main body, respectively. A device and an oxidant supply device;
Fuel cell power generation including a battery cooling system for controlling the temperature of the fuel cell main body, an orthogonal transformer connected to the output end of the fuel cell main body, and an external load system switch connecting the orthogonal transformer and the external load system A fuel cell power plant comprising a control means for performing the method according to claim 1.

According to the first and eleventh aspects of the present invention, after the power generation operation is stopped or before the power generation operation is started, the idle mode operation is performed with the minimum load of only the power system in the fuel cell plant shut off from the external load. By independently controlling the cell cooling water system in a state where all cells in the fuel cell main body are suppressed to the upper limit voltage, for example, 0.8 V / cell or less,
The operation can be shifted to a heating operation or a cooling operation. As a result, the electrode catalyst layer is not exposed to a high temperature and a high potential immediately after the stop of the power generation operation or before the start of the power generation operation, so that it is possible to smoothly shut off the external load or shift to the external load without deterioration of the catalyst. Can be implemented.

According to a second aspect of the present invention, there is provided a method for starting and stopping a fuel cell power plant according to the first aspect, the method further comprising the following steps when the fuel cell power plant is stopped. That is, controlling the power generation load based on a stop command to reduce the load to the minimum load, after reaching the minimum load, opening the external load system switch and performing the idle mode operation; In parallel with the step of performing the mode operation, a step of controlling the battery cooling system to perform a temperature lowering operation of the fuel cell body is provided. Further, when the fuel cell main body temperature is lowered to an idle mode operation stop temperature set lower than the operating temperature, the step of stopping the idle mode operation and the step of stopping the idle mode operation are performed in parallel with the gas. A step of performing a main body stop operation including a replacement operation and a residual voltage suppression operation. Here, the gas replacement operation includes shutting off the supply of the reformed fuel and the oxidant from the fuel reforming device and the oxidant supply device to the fuel cell main body, and simultaneously supplying an inert gas to the fuel cell main body. This is an operation to drive out residual gas. The residual voltage suppressing operation is an operation of suppressing a residual voltage by inserting a dummy resistor between a fuel electrode and an oxidant electrode of the fuel cell body.

According to a twelfth aspect of the present invention, in the fuel cell power plant according to the eleventh aspect, an inert gas supply device for supplying an inert gas to the fuel cell body is provided, and a fuel electrode of the fuel cell body is provided. 3. A dummy resistor connectable between the dummy gas and the oxidizer electrode is provided, and the control means is configured to be able to perform the method according to claim 2 using the inert gas supply device and the dummy resistor. A fuel cell power plant characterized by the following.

According to the second and twelfth aspects of the invention, after the power generation operation is stopped, the idle mode operation is performed with the minimum load of only the power system in the fuel cell plant shut off from the external load, so that the fuel cell main body is operated. In a state where all the cells in the cell are suppressed to the upper limit voltage, for example, 0.8 V / cell or less, the battery cooling water system can be independently controlled to perform the temperature lowering operation. When the temperature of the battery body drops to a predetermined temperature lower than the operating temperature, the idle mode operation is stopped, the supply of fuel and oxidant is shut off, and at the same time, a gas replacement operation with an inert gas is started and a dummy resistor is turned on. By doing so, a stop operation for suppressing the residual voltage can be performed. As a result, while the fuel cell body temperature is maintained at a high temperature during the idle mode operation, all the single cell voltages can satisfy the allowable value. Furthermore, even when a voltage higher than the upper limit voltage is generated in a single cell or locally, since the temperature of the battery body is already lower than the operating temperature, the residual due to the insertion of the dummy resistor at the time of the stop operation after the idle mode operation. The deterioration of the catalyst can be suppressed by the voltage suppressing operation.

According to a third aspect of the present invention, in the method for starting / stopping a fuel cell power plant according to the first aspect, the idle mode operation stop temperature is set so that the maximum temperature inside the fuel cell main body is 150 to 180 ° C. It is characterized by a temperature when the temperature reaches the range.

According to the third aspect of the present invention, after the power generation operation is stopped, the idle mode operation is performed.
The upper limit voltage of all cells in the fuel cell body, for example, 0.8
In a state where the temperature is suppressed to V / cell or less, the temperature lowering operation can be performed by independently controlling the battery cooling water system. Then, when the maximum battery temperature falls to 150 to 180 ° C., the idle mode operation is stopped, the supplied fuel and the oxidant are shut off, and at the same time, the gas replacement operation with an inert gas is started, and the dummy resistor is turned on. Thus, a stop operation for suppressing the residual voltage can be performed. As a result, while the fuel cell body temperature is maintained at a high temperature during the idle mode operation, all the single cell voltages can satisfy the allowable value. Furthermore, even when a voltage higher than the upper limit voltage is generated in a single cell or locally, the maximum temperature of the battery body is already
Temperature range 150 to 1 where catalyst deterioration rate can be sufficiently suppressed
Since the temperature is reduced to 80 ° C., the deterioration of the catalyst due to the stop operation can be sufficiently suppressed by the residual voltage suppression operation by turning on the dummy resistor at the time of the stop operation after the idle mode operation.

According to a fourth aspect of the present invention, in the method for starting and stopping the fuel cell power plant according to the second aspect, the step of performing the temperature lowering operation of the fuel cell main body includes the step of lowering the battery temperature during the idle mode operation. The battery cooling system is controlled such that the speed and the battery cooling rate from the main body stop operation after the idle mode operation to the battery storage temperature are maintained at 50 ° C./h or less.

According to the above-described invention, the temperature reduction rate is set to 50 ° C./h or less in a series of temperature lowering operations of the battery main body during the idle mode operation after the power generation is stopped and until the battery storage temperature. The stopping operation can be completed without causing a sudden change in phosphoric acid volume. As a result, it is possible to avoid leakage of phosphoric acid from the fuel cell laminated member made of a porous body, transfer of phosphoric acid between the members, and the like. The balance can be prevented from being lost, and excellent battery life can be ensured.

According to a fifth aspect of the present invention, there is provided a method for starting / stopping a fuel cell power plant according to the first aspect, wherein the method comprises the following steps when starting the fuel cell power plant. That is, controlling the battery cooling system based on a start command to perform a temperature raising operation of the fuel cell main body, and raising the temperature of the fuel cell main body to an idle mode operation start temperature set lower than the operating temperature. And performing the idle mode operation by supplying the reformed fuel and the oxidant from the reforming device and the oxidant supply device to the fuel cell main body, respectively. Further, the method includes a step of turning on the external load system switch when the temperature of the fuel cell main body reaches the operating temperature, and performing an external start operation for outputting power to the external load system.

According to a thirteenth aspect of the present invention, in the fuel cell power plant according to the eleventh aspect, the control means is configured to execute the method according to the fifth aspect. is there.

According to the fifth and thirteenth aspects of the present invention, the electrode in a high potential state (0.8 V or more) generated by oxygen mixed from the atmosphere into the cell during storage of the fuel cell is
By starting the idle mode operation at a temperature lower than the operating temperature before the catalyst is exposed to a high temperature state in which the catalyst deteriorates, all the cells in the fuel cell main body are suppressed to an upper limit voltage, for example, 0.8 V / cell or less. be able to. Thus, the deterioration of the catalyst can be suppressed as compared with the case where the catalyst is exposed to the high potential state up to the operating temperature.

According to a sixth aspect of the present invention, in the method of starting and stopping the fuel cell power plant according to the fifth aspect, the idle mode operation start temperature is a temperature of 150 ° C. or more.

According to the sixth aspect of the present invention, the electrode in a high potential state (0.8 V or more) generated by oxygen mixed in from the atmosphere into the cell during storage of the fuel cell undergoes catalyst deterioration. Before exposure to a high temperature state, when the catalyst deterioration rate reaches a temperature of 150 ° C. at which the acceleration has not yet accelerated, the idle mode operation is started, so that all the cells in the fuel cell main body have an upper limit voltage, for example, 0.8 V / It can be suppressed below the cell. As a result, catalyst deterioration accompanying the start-up operation can be sufficiently suppressed.

According to a seventh aspect of the present invention, in the method for starting and stopping the fuel cell power plant according to the fifth aspect, the step of performing the temperature raising operation of the fuel cell main body includes the steps of: The battery cooling system is controlled such that the battery heating rate immediately before the operation and the battery heating rate during the idle mode operation are maintained at 50 ° C./h or less.

According to the above-described invention, the battery temperature can be raised from the battery storage temperature after startup to immediately before the idle mode operation, and in a series of battery body temperature raising operations during the idle mode operation. Temperature operation at 50 ° C / h
Since the temperature is limited to the following, the temperature raising operation can be completed without a sudden change in phosphoric acid volume. As a result, it is possible to avoid leakage of phosphoric acid from the fuel cell laminated member made of a porous body, transfer of phosphoric acid between the members, and the like. The balance can be prevented from being lost, and excellent battery life can be ensured.

According to an eighth aspect of the present invention, in the method for starting / stopping a fuel cell power plant according to the fifth aspect, the temperature of the fuel cell body is set to 100 ° C. during the step of performing the temperature raising operation of the fuel cell body. Before reaching the temperature, an inert gas containing a trace amount of hydrogen of 4% or less is supplied to the fuel electrode of the fuel cell main body, and the cell voltage of the fuel cell main body has reached a preset voltage suppression start voltage or more. At this point, a residual resistance is suppressed by inserting a dummy resistor between the fuel electrode and the oxidant electrode of the fuel cell body.

According to a fourteenth aspect of the present invention, in the fuel cell power plant according to the thirteenth aspect, an inert gas supply device for supplying an inert gas to the fuel cell main body is provided, and a fuel electrode of the fuel cell main body is provided. 9. A dummy resistor connectable between the dummy gas and the oxidizer electrode is provided, and the control means is configured to be able to perform the method according to claim 8 using the inert gas supply device and the dummy resistor. A fuel cell power plant characterized by the following.

According to the eighth and fourteenth aspects of the present invention, the electrode in a high potential state (0.8 V or more) generated by oxygen mixed from the atmosphere in the fuel cell during storage of the fuel cell,
By supplying a small amount of H ₂ to the fuel electrode before reaching a high temperature state in which catalyst deterioration proceeds, the potential of the fuel electrode can be reduced and the potential of the oxidant electrode can be observed as a voltage value. When the observed voltage value reaches or exceeds a preset voltage suppression start voltage, the potential of the oxidant electrode is suppressed by turning on the dummy resistor and consuming O ₂ in the oxidant electrode. be able to. Thus, it is possible to prevent the catalyst from deteriorating at high temperatures and high potentials due to the temperature rise.

According to a ninth aspect of the present invention, there is provided a fuel cell body comprising a plurality of unit cells each comprising a fuel electrode and an oxidant electrode, a fuel reformer for supplying fuel and an oxidant to the fuel cell body, and An oxidant supply device, a battery cooling system for controlling the temperature of the fuel cell body, an orthogonal transformer connected to the output end of the fuel cell body, and an external load system switch connecting the orthogonal transformer and an external load system The present invention relates to a fuel cell power plant stop operation method for performing a fuel cell power plant stop operation including:
In particular, a gas that shuts off the supply of the reformed fuel and the oxidant from the fuel reforming device and the oxidant supply device to the fuel cell body and simultaneously supplies an inert gas to the fuel cell body to drive out the residual gas Fuel cell power generation comprising a replacement operation and a main body stop operation including a residual voltage suppressing operation for suppressing a residual voltage by inserting a dummy resistor between a fuel electrode and an oxidant electrode of the fuel cell main body. In the plant shutdown operation method, the inert gas supplied to at least one of the fuel electrode and the oxidizer electrode of the fuel cell main body contains a small amount of oxygen of 0.1% or less.

According to a fifteenth aspect of the present invention, there is provided a fuel cell body comprising a plurality of unit cells each comprising a fuel electrode and an oxidant electrode, a fuel reformer for supplying fuel and an oxidant to the fuel cell body, and An oxidant supply device, an inert gas supply device for supplying an inert gas to the fuel cell body,
A battery cooling system for controlling the temperature of the fuel cell body, an orthogonal transformation device connected to the output end of the fuel cell body, an external load system switch connecting the orthogonal transformation device and an external load system, In a fuel cell power plant having a dummy resistor connectable between a fuel electrode and an oxidizer electrode, the inert gas supply device supplies the fuel cell body to at least one of the fuel electrode and the oxidizer electrode. The inert gas contains a small amount of oxygen of 0.1% or less.

[0045] In the above-described inventions according to the ninth and fifteenth aspects, since a small amount of oxygen of 0.1% or less is contained in the inert gas in a state where the gas replacement with the inert gas is performed. The electrode potential is in a state of equilibrium with the trace amount of oxygen,
That is, the range is 0.3 to 0.8V. Than this,
Since the electrode potential after the stop operation can be controlled within an appropriate range, catalyst deterioration can be suppressed.

According to a tenth aspect of the present invention, in the method of shutting down a fuel cell power plant according to the ninth aspect, the oxygen concentration in the inert gas is 0.005 to 0.05%. I have.

According to the tenth aspect of the present invention,
Since the oxygen concentration in the inert gas is 0.001 to 0.1% while the gas replacement operation with the inert gas is performed, the electrode potential is set in the range of 0.3 to 0.8 V. Can be surely balanced. Thus, the electrode potential after the stop operation can be maintained within an appropriate range, so that catalyst deterioration can be suppressed.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a fuel cell power plant and a method of starting and stopping the same according to the present invention will be specifically described with reference to the drawings. The same members as those in the conventional technique shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

(1) First Embodiment One embodiment to which the inventions of claims 3 and 12 are applied will be described below as a first embodiment with reference to FIG.

(Configuration) First, the configuration of the fuel cell power plant according to the present embodiment will be described. That is, as shown in FIG. 1, between the anode 2 and the cathode 3, an inverter (orthogonal transformer) 16 and a dummy resistor 17 connected via an inverter switch 18 and a dummy resistor switch 19, respectively, are added. Thus, the voltage detectors 20 are connected in parallel. The AC output line of the inverter 16 is connected in parallel with an in-house power system 21 that supplies a part of the fuel cell output to the in-house power and an external load system 22 line that supplies the fuel cell output to the outside. Each is connected to be openable and closable via an in-house power system switch 23 and an external load system switch 24.

The fuel cell body 1 has a hot spot in the unit cell, for example, a temperature at which the temperature is measured at the inlet of the cathode 3 of the unit cell at the stacking position farthest from the cooling plate in the unit cell. A sensor 25 is provided. In this case, the anode 2 inlet and a cathode 3 inlet, as in the prior art shown in FIG. 7, the anode N ₂ supply system 9 and the cathode N ₂ through the anode N ₂ supply valve 10 and the cathode N ₂ supply valve 14 The supply system 13 is connected.

Further, in addition to the above configuration, a control device (control means) 26 having various kinds of control functions is provided. That is, the control device 26 controls the battery temperature by giving an output to the battery cooling water system 4 based on the detection value of the temperature sensor 25, the inverter opening and closing control function of controlling the opening and closing of the inverter switch 18, reaction gas supply control function for controlling the opening and closing of the fuel supply shut-off valve 7 and the air supply shut off valve 11, the inert gas supply control function for controlling the opening and closing of the anode N ₂ supply valve 10 and the cathode N ₂ supply valve 14, a voltage detector A dummy resistance switching control function for controlling the switching of the dummy resistance switch 19 based on the detected value of 20;
It has a system opening / closing control function for controlling an external load system switch 24 and an in-house power system switch 23 for turning on / off the external load system 22 and the in-house power system 21.

(Operation) The operation of the present embodiment having the above configuration is as follows. That is, when the stop command is input, the control device 26 instructs a load reduction operation to a minimum load corresponding to the in-plant power with the transition from the power generation operation state to the stop state. After the minimum load level is reached, the control device 26 gives an open signal to the external load system switch 24 to disconnect the external load system, while the on-site power system switch 2
For No. 3, the closed signal is held, and the idle mode operation at the minimum load level of only the in-house power system 21 is performed.

In this case, all the stacked single cells of the fuel cell main body 1 have a load level satisfying 0.8 V / cell or less, so that catalyst deterioration accompanying sintering does not progress. In general, if the plant is operated at normal pressure, even if the load is sufficiently small (current density is about 10 mA / sq.cm), 0.8 V
Since the battery voltage of / V or less can be satisfied, the suppression of the voltage of 0.8 V / cell or less by the in-house power system load value can be easily achieved.

Further, the control device 26 gives a temperature lowering signal to the battery cooling water system 4 based on the stop command, and performs the temperature lowering operation of the fuel cell main body 1 in parallel with the idle mode operation. In this case, the temperature sensor 25 continuously detects the hot spot temperature of the fuel cell main body 1 during the idle mode operation, and continuously transmits the detected value to the control device 26.

Then, the detection value from the temperature sensor 25 is
The idle mode shutdown temperature set at a temperature lower than the operating temperature in the range of 150 to 180 ° C., preferably 150 ° C.
At the stage of reaching, the control device 26 gives an open signal to the in-house power system switch 23 and the inverter switch 18 to execute the fuel cell load cutoff, and at the same time, the fuel supply cutoff valve 7
Then, a fully closed signal is given to the air supply shutoff valve 11 to shut off the supply of fuel and air. In parallel with the reaction gas supply cutoff control, the control device 26 further provides an opening signal to the N ₂ supply valves 10 and 14 at the anode inlet and the cathode inlet by an inert gas supply control function, so that the anode 2 and the cathode 3 are supplied. On the other hand, a gas replacement operation with N ₂ is performed.

At this time, a residual voltage is generated by the residual H ₂ -rich gas on the anode 2 and residual air on the cathode 3, and the residual voltage is detected by the voltage detector 20 and transmitted to the control device 26 to suppress the battery voltage. Control is performed. That is, when the detection value from the voltage detector 20 exceeds a predetermined value, for example, when the voltage exceeds 0.8 V / cell, the control device 26 supplies a turn-on signal to the dummy resistance switch 19 to To suppress the battery voltage by consuming the battery output.

With the above operation, the power generation stop operation of the fuel cell body 1 itself is completed (the power generation operation to the external load system 22 has already been stopped, but the power generation operation of the fuel cell body 1 itself is completed at this timing. Do). The control device 26
Continues the temperature lowering operation of the fuel cell main body 1 to the battery storage temperature.

(Effects) The effects of the present embodiment as described above are as follows. That is, even after the shutoff operation of the external load system 22 according to the stop command, the fuel cell main body 1 performs the idle mode operation, so that all the stacked single cells are
It can be controlled to a predetermined value of 0.8 V / cell or less. for that reason,
The operation of lowering the temperature of the fuel cell main body 1 can be favorably performed without deterioration of the catalyst due to sintering.
In addition, the hot spot temperature of the fuel cell main body 1 is 150 to
At the stage when the temperature is lowered to 180 ° C., the idle mode operation is stopped, and the battery operation is actually stopped. In this case, in the gas replacement by N ₂ and the macro voltage suppression operation by the dummy resistor 17, the stacked single cell 0.8V in part of
Even if a phenomenon that deviates from a predetermined value equal to or higher than / cell occurs, since the temperature of the fuel cell body has already dropped to the predetermined temperature,
The degree of progress of catalyst deterioration due to sintering is slow and acceptable.

FIG. 2 is a graph showing the relationship between the battery temperature (catalyst temperature) obtained by the present inventors through experiments and the catalyst surface area phenomenon ratio indicating the degree of sintering. : 0.9 V, potential holding time: 1 h.
As shown in FIG. 2, the catalyst surface area reduction ratio accompanying sintering is greatly reduced as the temperature becomes lower. The catalyst surface area reduction ratio at 150 ° C., that is, the sintering progress speed is determined in consideration of the stop operation time. Almost in acceptable range.

The operation of stopping the fuel cell main body 1 at a hot spot lower than 150 ° C. is sufficiently effective in suppressing sintering. Gas diffusion failure due to the securing of the pressure of the steam supplied to the fuel device 5 and the condensation of the generated water containing phosphoric acid at the cold spot of the fuel cell main body 1 (phosphoric acid condensed in the low temperature region causes the reaction of the electrode This obstructs the gas flow passage and hinders the electrochemical reaction of the battery), which causes problems in plant operation and deterioration of battery characteristics.

Therefore, in the present embodiment, the actual load rejection operation of the fuel cell main body at the hot spot temperature of 150 to 180 ° C., particularly at 150 ° C., does not cause deterioration of the characteristics due to poor gas diffusion, and the catalyst deterioration proceeds. It is possible to provide the most reliable stop operation of the fuel cell power plant that can prevent the occurrence of the fuel cell power plant, and is highly practical.

(2) Second Embodiment One embodiment to which the inventions of claims 6 and 13 are applied will be described below as a second embodiment with reference to FIG.

(Configuration) First, the configuration of the fuel cell power plant according to the present embodiment will be described. That is, as shown in FIG. 3, in addition to the inverter 16 and the dummy resistor 17 connected between the anode 2 and the cathode 3 via the inverter switch 18 and the dummy resistor switch 19, respectively, a voltage detector 20 is provided. Are connected in parallel as in the first embodiment. And the inverter 16
The AC output line is connected in parallel with an in-house power system 21 that supplies a part of the fuel cell output to the in-house power and an external load system 22 line that supplies the fuel cell output to the outside. It is also the same as the first embodiment in that it is openably and closably connected via a switch 23 and an external load system switch 24.

On the other hand, the temperature sensor provided in the fuel cell main body 1 is not limited to the hot spot in the laminated single cell. In this embodiment, in order to measure the temperature of the fuel cell main body 1 more macroscopically, the temperature sensor 2 is provided at an arbitrary position in the fuel cell main body 1.
7 are arranged.

Further, the control device 26 of the present embodiment
It has various types of control functions similar to those of the first embodiment. The control functions actually required in the present embodiment include a battery temperature control function of controlling the battery temperature by giving an output to the battery cooling water system 4 based on the detection value of the temperature sensor 27, and opening and closing the inverter switch 18. Inverter opening / closing control function for controlling, reaction gas supply control function for controlling opening / closing of fuel supply cutoff valve 7 and air supply cutoff valve 11, external load system 2
2 and a system opening / closing control function for controlling the external load system switch 24 and the in-house power system switch 23 for turning on / off the in-house power system 21.

(Operation) The operation of the present embodiment having the above configuration is as follows. That is, when the start command is input, the control device 26 gives a temperature rise signal to the battery cooling water system 4 to carry out a temperature rise operation of the fuel cell main body 1 with the transition from the fuel cell storage state to the start state. I do. In this case, the temperature sensor 27 continuously detects the temperature of the fuel cell main body 1 and continuously transmits the detected value to the control device 26.

When the value detected by the temperature sensor 27, that is, the temperature of the fuel cell main body 1 reaches 150 ° C., the control device 26 shifts to the idle mode operation. That is, H ₂ rich gas is introduced from the fuel reformer 5 to the anode 2 by opening the fuel supply cutoff valve 7, and then air is supplied to the cathode 3 by opening the air supply cutoff valve 11. Further, the fuel cell body 1
Is detected by the voltage detector 20, and when the detected value reaches a predetermined value, for example, when the voltage reaches 0.8 V / cell, the inverter switch 18 is turned on, and the local power system switch 23 is turned on. Power supply, the on-site power system 21
A line is formed, and the load transfer to the idle mode operation is completed.

The control device 26 continues the idle mode operation and the operation of increasing the temperature of the fuel cell body 1 in parallel. Then, the temperature of the fuel cell body 1 becomes a predetermined operating temperature, for example, 1
When the temperature reaches 90 ° C., the control device 26 turns on the external load system switch 24, forms an external load system 22 line, and performs load increase control from idle mode operation. When a predetermined external load value is reached, the mode shifts to the power generation operation mode, and a series of startup operations is completed.

(Effects) The effects of the present embodiment as described above are as follows. That is, at the start of the start-up operation, the electrode in a high potential state (0.8 V or more) generated by oxygen mixed into the cell from the atmosphere during storage of the fuel cell is:
It shifts to a high temperature state as the temperature rises.
By starting idle mode operation when the catalyst deterioration progress rate due to sintering reaches an acceptable temperature, ie, 150 ° C., all cells in the fuel cell body are suppressed to an upper limit voltage of 0.8 V / cell or less. can do.

In this regard, as described in the first embodiment, according to the experimental results of the present inventors, in the high potential state at a relatively low temperature of 150 ° C., the operating temperature, for example, 200 ° C. The sintering speed is greatly reduced compared to the degree, and considering the startup operation time,
It is almost acceptable range.

Also, as described in the first embodiment, the idle mode operation at a temperature lower than 150 ° C. is sufficiently effective in suppressing the sintering. Due to the securing of the steam pressure supplied from the cooling water system 4 to the fuel reformer 5 and the poor diffusion of the reaction gas due to the condensation of the generated water containing phosphoric acid at the cold spot of the fuel cell main body 1, the plant operation becomes difficult. And the problem of deteriorating the battery characteristics.

Therefore, the substantial load shift operation of the fuel cell body at a fuel cell temperature of 150 ° C. or more as shown in the present embodiment prevents the deterioration of the catalyst due to poor gas diffusion and prevents the progress of catalyst deterioration. It is possible to provide the most reliable start-up operation of a fuel cell power plant that can be performed, and is highly practical.

(3) Third Embodiment One embodiment to which the invention described in claim 4 is applied will be described below as a third embodiment.

(Structure) First, in the fuel cell power plant according to the present embodiment, in the first embodiment shown in FIG. 1, the control device 26 further controls the battery cooling water temperature to decrease by 50%. It is also characterized in that it has a function of controlling the battery cooling water system 4 so as to be lower than or equal to ° C / h. The other parts are configured in exactly the same manner as in the first embodiment.

(Operation) The operation of the present embodiment having the above configuration will be described below. That is, when the stop command is input, the control device 26 instructs a load reduction operation to a minimum load corresponding to the in-plant power with the transition from the power generation operation state to the stop state. After the minimum load level is reached, the control device 26 gives an open signal to the external load system switch 24 to disconnect the external load system, while the on-site power system switch 23
, The idle signal operation is performed at the minimum load level of only the in-house power system 21.

Further, the control device 26 gives a temperature lowering signal to the battery cooling water system 4 based on the stop command, so that the cooling water cooling speed is maintained at 50 ° C./h or less in parallel with the idle mode operation. Then, the temperature lowering operation of the fuel cell main body 1 is performed. In this case, the temperature sensor 25 continuously detects the temperature of the fuel cell main body 1 and continuously transmits the detected value to the control device 26.

Then, the detection value from the temperature sensor 25 is
When the temperature reaches a range of 150 to 180 ° C., desirably 150 ° C., the control device 26 gives an open signal to the in-house power system switch 23 and the inverter switch 18 to execute the fuel cell load cut-off and simultaneously supply the fuel. The shutoff valve 7 and the air supply shutoff valve 11 are supplied with a fully closed signal to shut off the supply of fuel and air. The control device 26 further controls the N ₂ supply valves 1 at the anode inlet and the cathode inlet by an inert gas supply control function in parallel with the reaction gas supply cutoff control.
An open signal is given to 0 and 14 to perform a gas replacement operation with N ₂ on the anode 2 and the cathode 3.

At this time, a residual voltage is generated by the residual H ₂ -rich gas on the anode 2 and the residual air on the cathode 3. The residual voltage is detected by the voltage detector 20 and transmitted to the control device 26 to suppress the battery voltage. Control is performed. That is, when the detection value from the voltage detector 20 exceeds a predetermined value, for example, when the voltage exceeds 0.8 V / cell, the control device 26 supplies a turn-on signal to the dummy resistance switch 19 to , And the battery output is consumed, thereby suppressing the battery voltage. By the above operation, the power generation stop operation of the fuel cell body 1 itself is completed. However, the control device 26 controls not only the temperature reduction rate during the idle mode operation but also the temperature reduction rate from the power generation stop operation after the idle mode to the battery storage temperature. Is maintained at 50 ° C./h or lower, and the temperature lowering operation of the battery cooling water system 4 is continued.

(Effects) According to the present embodiment as described above, the following effects can be obtained in addition to the effects of the first embodiment. In other words, during the idle mode operation after the power generation is stopped and during a series of temperature lowering operations of the battery main body to the battery storage temperature, the temperature lowering rate is set to 50.
By limiting the temperature to ° C / h or less, the stopping operation can be completed without causing a sudden change in phosphoric acid volume.

Accordingly, it is possible to avoid leakage of phosphoric acid from the porous fuel cell laminated member, transfer of phosphoric acid between the members, and the like. Disruption of the acid retention balance can be prevented, and excellent battery life can be ensured.

(4) Fourth Embodiment One embodiment to which the invention described in claim 7 is applied will be described below as a fourth embodiment.

(Structure) First, in the fuel cell power plant according to the present embodiment, in the second embodiment shown in FIG. 3, the control device 26 further controls the temperature increase rate of the battery cooling water temperature. It is also characterized by having a function of controlling the battery cooling water system 4 so as to be 50 ° C./h or less. The other parts are configured exactly the same as in the second embodiment.

(Operation) The operation of the present embodiment having the above configuration will be described below. That is, when the start command is input, the control device 26 gives a temperature rise signal to the battery cooling water system 4 to carry out a temperature rise operation of the fuel cell main body 1 with the transition from the fuel cell storage state to the start state. I do. In this case, the control device 26 sets the cooling water heating rate to 50 ° C./h.
The temperature raising operation of the fuel cell main body 1 is performed while maintaining the following. In this case, the temperature sensor 27 continuously detects the temperature of the fuel cell main body 1 and continuously transmits the detected value to the control device 26.

When the value detected by the temperature sensor 27, that is, the temperature of the fuel cell main body 1 reaches 150 ° C., the control device 26 shifts to the idle mode operation. Note that the control device 26 continues the idle mode operation and the temperature raising operation of the battery body 1 in parallel, and, like the battery temperature increase rate from the battery storage temperature to immediately before the idle mode operation, the battery during the idle mode operation. Heating rate is 50 ℃
The operation of raising the temperature of the battery cooling water system 4 is performed so as to satisfy / h or less.

Next, when the temperature of the fuel cell body 1 reaches a predetermined operating temperature, for example, 190 ° C., the controller 26
Turns on the external load system switch 24 and outputs the external load system 2
Two lines are formed to perform load increase control from idle mode operation. When a predetermined external load value is reached, the mode shifts to the power generation operation mode, and a series of startup operations is completed.

(Effects) According to the present embodiment as described above, the following effects can be obtained in addition to the effects of the second embodiment. That is, in the battery temperature raising operation from the battery storage temperature after startup to immediately before the idle mode operation and a series of battery body temperature raising operations during the idle mode operation, the temperature raising operation is limited to 50 ° C./h or less. The temperature raising operation can be completed without causing a sudden change in phosphoric acid volume.

Accordingly, it is possible to avoid leakage of phosphoric acid from the porous fuel cell laminated member made of a porous body, transfer of phosphoric acid between the members, and the like. Disruption of the acid retention balance can be prevented, and excellent battery life can be ensured.

(5) Fifth Embodiment One embodiment to which the inventions of claims 8 and 14 are applied will be described below as a fifth embodiment with reference to FIG.

(Configuration) First, the configuration of the fuel cell power plant according to the present embodiment is different from the second embodiment shown in FIG. 3 in that a configuration for supplying a trace amount of hydrogen-containing nitrogen is further added. It was done. That is, the inlet of the anode 2 is supplied via the trace H ₂ -containing N ₂ supply valve 28,
A trace H ₂ -containing N ₂ supply system (trace hydrogen-containing gas supply device) 29 containing a trace amount of H ₂ of 4% or less is connected.
The other parts are configured exactly the same as in the second embodiment.

(Operation) The operation of the present embodiment having the above configuration is as follows. That is, when the start command is input, the control device 26 gives a temperature increase signal to the battery cooling water system 4 and performs a temperature increase operation of the fuel cell main body 1 with the transition from the fuel cell storage state to the start state. . In this case, the temperature sensor 27 continuously detects the temperature of the fuel cell main body 1 and continuously transmits the detected value to the control device 26.

Then, the temperature of the fuel cell main body 1 is 100 ° C.
Prior to reaching the anode trace H ₂
An open signal is given to the containing N ₂ supply valve 28, and a trace amount of H ₂ containing N ₂
An N ₂ gas containing a small amount of H ₂ of 4% or less is supplied from the supply system 29 to the anode 2. At this point, since there is a possibility that air may enter into the anode 2 during storage of the battery, there is a danger of explosion if a high concentration of H ₂ is supplied. N supplied to 2
_Since the H ₂ concentration in the _two gases is below the explosion limit of 4% or less, the operation can be performed safely.

The N containing a trace amount of H ₂ of 4% or less
The supply of the _two gases reduces the potential of the anode 2 and makes the potential of the cathode 3 observable as a voltage value. That is, even when the anode 2 is in a high potential state (0.8 V or more) due to oxygen mixed into the cell from the atmosphere during storage of the fuel cell, the supplied H ₂ is adsorbed on the catalyst of the anode 2. since the anode 2 is is H ₂ potential 0V
Reduce to near. On the other hand, similarly, since the cathode 3 is in a high potential state, a voltage is generated between the anode 2 and the cathode 3 due to a decrease in the potential of the anode 2. The voltage detector 20 detects the generated voltage and outputs the detected value to the control device 2.
Continue sending to 6.

When the generated voltage reaches a predetermined voltage suppression start voltage value, for example, 0.7 V / cell or more, the control device 26 supplies a closing signal to the dummy resistance switch 19 to 17 is supplied and the mixed O ₂ in the cathode 3 is consumed, thereby reducing the voltage and suppressing the potential of the cathode 3 electrode.

(Effects) According to the present embodiment as described above, the following effects can be further obtained in addition to the effects of the second embodiment. That is, in the temperature raising operation, the electrode in a high potential state (0.8 V or more) generated by oxygen mixed from the atmosphere into the battery cell during storage of the fuel cell is brought to a high temperature state of 100 ° C. or more at which catalyst deterioration proceeds. before reaching, by supplying of H ₂ less than 4% of the small amount of the anode 2, by reducing the anode potential, and consumes O ₂ in the cathode 3 by introducing the dummy resistor 17, the cathode The potential can be suppressed. Therefore, it is possible to completely prevent the catalyst from deteriorating at a high temperature and a high potential due to the temperature rise.

(6) Sixth Embodiment One embodiment to which the inventions of claims 10 and 15 are applied will be described below as a sixth embodiment with reference to FIG.

(Structure) First, the structure of the fuel cell power plant used in this embodiment is different from that of the first embodiment shown in FIG. 1 in that a small amount of air is mixed into the cathode 3 side. The configuration is added. That is, the cathode air supply system 31 is connected to the upstream of the cathode N ₂ supply valve 14 disposed at the inlet of the cathode 3 via the cathode air mixing adjustment valve 30. Here, when the cathode N ₂ supply valve 14 is opened and N ₂ is supplied to the cathode 3, the cathode aeration control valve 30 is operated simultaneously with the cathode N ₂ supply valve 14. It is configured to perform an opening operation. Further, the cathode air mixing adjustment valve 30 in this opening operation
Is the O ₂ in the N ₂ gas supplied to the cathode 3.
The concentration is adjusted so as to satisfy 0.005 to 0.05%, and the control is performed by the control device 26. The other parts are configured in exactly the same manner as in the first embodiment.

(Operation) The operation of the present embodiment having the above configuration is as follows. That is, when the stop command is input, the control device 26 instructs a load reduction operation to a minimum load corresponding to the in-plant power with the transition from the power generation operation state to the stop state. After reaching the minimum load level, the control device 26 gives an open signal to the external load system switch 24 to disconnect the external load system 22, and holds a close signal in the in-house power system switch 23, and only the in-house power system 21 Continue the idle mode operation at the minimum load level.

Further, the control device 26 gives a temperature lowering signal to the battery cooling water system 4 simultaneously with the stop command, and performs the temperature lowering operation of the fuel cell main body 1 in parallel with the idle mode operation. In this case, the temperature sensor 25 continuously detects a hot spot of the fuel cell main body 1 during the idle mode operation, and continuously transmits the detected value to the control device 26.

Then, the detection value from the temperature sensor 25 is
When the temperature reaches a range of 150 to 180 ° C., desirably 150 ° C., the control device 26 gives an open signal to the in-house power system switch 23 and the inverter switch 18 to execute the fuel cell load cut-off and simultaneously supply the fuel. The shutoff valve 7 and the air supply shutoff valve 11 are supplied with a fully closed signal to shut off the supply of fuel and air. The control device 26 further controls the N ₂ supply valves 1 at the anode inlet and the cathode inlet by an inert gas supply control function in parallel with the reaction gas supply cutoff control.
An open signal is given to 0 and 14 to perform a gas replacement operation with N ₂ on the anode 2 and the cathode 3.

At this time, a residual voltage is generated by the residual H ₂ -rich gas on the anode 2 and the residual air on the cathode 3, and the residual voltage is detected by the voltage detector 20 and transmitted to the control device 26 to suppress the battery voltage. Control is performed. That is, when the detection value from the voltage detector 20 exceeds a predetermined value, for example, when the voltage exceeds 0.8 V / cell, the control device 26 supplies a turn-on signal to the dummy resistance switch 19 to To suppress the battery voltage by consuming the battery output.

[0102] Further, in this embodiment, when supplying the N ₂ the cathode N ₂ supply valve 14 opening operation to the cathode 3 as described above, the control unit 26, cathode N ₂ supply valve 14 at the same time cathode aerated regulating valve 30 is also opened, the therefore to control the valve opening, N ₂ to the cathode 3 containing 0.005 to 0.05 percent of the O ₂ from the cathode air supply system 31 is supplied. Thus, 0.005-0.
By supplying O _{2 at} a concentration of 05%, the electrode potential of the cathode 3 is reliably maintained in the range of 0.3 to 0.8 V.

With the above operation, the power generation stop operation of the fuel cell main body 1 itself is completed, but the control device 26 continues the temperature lowering operation of the fuel cell main body 1 to the battery storage temperature.

(Effects) According to the present embodiment as described above, the following effects can be obtained in addition to the effects of the first embodiment. That is, in a state where the gas replacement operation with the inert gas accompanying the stop operation is performed, a small amount of oxygen is contained in the inert gas, so that the electrode potential is maintained at a potential state equilibrium with the small amount of oxygen. You.

FIG. 6 is a graph showing the O values obtained by experiments by the present inventors.
₂ shows the relationship between the concentration and the electrode potential. As shown in FIG. 6, the relationship between the O ₂ concentration and the electrode potential changes depending on the catalyst composition (this is determined by the mixed potential of the noble metal and carbon, which is the catalyst composition). On the other hand, as described above, FIG. 8 shows the relationship between the electrode potential after the stop operation and the amount of voltage drop accompanying the stop operation.

From the graphs of FIG. 6 and FIG. 8, the electrode potential at an oxygen concentration of 0.001 to 0.1% is approximately 0.3 to 0.8 V even with various catalyst compositions. It is clear that can suppress the voltage drop due to the stop operation. That is, the electrode potential is 0.8 V
When the electrode potential exceeds 0.3 V, the sintering of the catalyst is accelerated, causing a voltage drop due to the stopping operation. On the other hand, when the electrode potential is 0.3 V or less, the catalyst noble metal dissolved by the sintering is reprecipitated. It is considered that the active area of the catalyst is reduced to cover the active site of the catalyst, thereby causing a voltage drop due to the stopping operation.

Therefore, even after the power generation is stopped, the electrode potential can be maintained at 0.3 to 0.8 V because the oxygen concentration in the inert gas is 0.001 to 0.1%. Such a catalyst deterioration phenomenon can be avoided. In particular, as in the present embodiment, the oxygen concentration is 0.00
When it is limited to 5 to 0.05%, as is apparent from FIG.
It can be maintained at 0.8V.

In this embodiment, a small amount of O ₂ is mixed in the purge N ₂ of the cathode 3. Similarly, a small amount of O ₂ is mixed in the purge N ₂ of the anode 2. Thereby, a similar effect can be obtained for the anode catalyst. When a small amount of O ₂ is mixed into one of the purge N ₂ of the anode 2 and the cathode 3, the electrolyte layer between the anode 2 and the cathode 3 is replaced with O _2.
Is slightly dissolved (10 mi)
n), but both electrodes can maintain an electrode potential that balances a small amount of O ₂ .

(7) Other Embodiments The present invention is not limited to the above embodiments. For example, as described above, each embodiment has a clear effect, but a synergistic effect can be obtained by appropriately combining the above-described embodiments. Further, the specific configuration of each part such as the control device, the supply valve, and the supply system can be appropriately selected.

[0110]

As described above, according to the present invention,
Implement idle mode operation only for the on-site power system,
By including a trace amount of hydrogen or trace amount of oxygen in the inert gas for gas replacement, the voltage of the fuel cell body can be sufficiently suppressed. It is possible to provide an excellent fuel cell power generation plant and a method for starting and stopping the fuel cell power generation plant, which can stably maintain the cell characteristics without deteriorating the operation.

[Brief description of the drawings]

FIG. 1 is a connection configuration diagram showing a fuel cell power plant according to first and third embodiments of the present invention.

FIG. 2 is a graph showing a relationship between a catalyst surface reduction ratio and catalyst temperature accompanying sintering of a fuel cell catalyst.

FIG. 3 is a connection configuration diagram showing a fuel cell power plant according to second and fourth embodiments of the present invention.

FIG. 4 is a connection configuration diagram showing a fuel cell power plant according to a fifth embodiment of the present invention.

FIG. 5 is a connection configuration diagram showing a fuel cell power plant according to a sixth embodiment of the present invention.

FIG. 6 is a graph showing the relationship between O ₂ concentration and electrode potential.

FIG. 7 is a connection configuration diagram showing an example of a conventional phosphoric acid fuel cell power plant.

FIG. 8 is a graph showing a relationship between an electrode potential during a start / stop operation and a voltage drop amount due to the start / stop operation.

[Explanation of symbols]

1 ... fuel cell body 2: anode 3 ... cathode 4 ... battery coolant system 5 ... fuel reformer 6 ... reformer burner 7 ... fuel supply cutoff valve 8 ... steam supply path 9 ... anode N ₂ supply system 10 ... anode N ₂ supply valve 11 ... Air supply cutoff valve 12 ... Blower 13 ... Cathode N ₂ supply system 14 ... Cathode N ₂ supply valve 15 ... Gas exhaust path 16 ... Inverter 17 ... Dummy resistor 18 ... Inverter switch 19 ... Dummy resistor switch 20 ... voltage detector 21 ... auxiliary power system 22 ... external load system 23 ... auxiliary power grid switch 24 ... external load system switches 25, 27 ... temperature sensor 26 ... controller 28 ... trace containing H ₂ N ₂ supply valve 29 … N ₂ supply system containing trace amounts of H ₂ 30… cathode air mixing control valve 31… cathode air supply system

Claims (15)

[Claims] 1. A fuel cell main body comprising a plurality of unit cells each comprising a fuel electrode and an oxidant electrode, a fuel reformer and an oxidant supply device for supplying fuel and oxidant to the fuel cell main body, respectively. Fuel cell power generation including a battery cooling system for controlling the temperature of the fuel cell main body, an orthogonal transformer connected to the output end of the fuel cell main body, and an external load system switch connecting the orthogonal transformer and the external load system In the plant start / stop operation method, when the fuel cell power plant is started or stopped, the external load system switch is opened while the internal power system of the fuel cell power plant is opened. Supplying the output of the fuel cell main body only to perform an idle mode operation of operating at a minimum load corresponding to a load of only the in-house power system. Start and stop operating method of the fuel cell power plant characterized and. 2. A step of controlling a power generation load based on a stop command to reduce the load to the minimum load at the time of a stop operation of the fuel cell power plant, and opening the external load system switch after reaching the minimum load. Performing the idle mode operation; controlling the battery cooling system to perform a temperature lowering operation of the fuel cell main body in parallel with the step of performing the idle mode operation; At the time when the temperature is lowered to the idle mode operation stop temperature set lower than the operating temperature, the step of stopping the idle mode operation and the step of stopping the idle mode operation are performed in parallel with the gas replacement operation and the residual voltage suppression operation. Performing a main body stop operation including: The operation of shutting off the supply of the reforming fuel and the oxidizing agent from the supply device to the fuel cell main body and simultaneously supplying the inert gas to the fuel cell main body to drive out the residual gas. 2. The method according to claim 1, wherein the residual voltage is suppressed by inserting a dummy resistor between the fuel electrode and the oxidant electrode of the main body. 3. The idle mode operation stop temperature is a temperature when a maximum temperature inside the fuel cell main body reaches a range of 150 to 180 ° C.
The start / stop operation method of the fuel cell power plant described in the above. 4. A step of performing a temperature lowering operation of the fuel cell main body, wherein the battery temperature lowering rate during the idle mode operation and a battery temperature lowering rate from the main body stopping operation after the idle mode operation to a battery storage temperature. At 50 ° C / h
The method according to claim 2, wherein the battery cooling system is controlled so as to maintain the following. 5. A step of controlling the battery cooling system based on a start command to perform a temperature raising operation of the fuel cell main body at a start operation of the fuel cell power plant; At the time when the temperature is raised to the idle mode operation start temperature set low, the reforming device and the oxidizing agent supplying device supply reformed fuel and an oxidizing agent to the fuel cell body, respectively, to perform the idle mode operation. Performing, and when the fuel cell main body temperature reaches the operating temperature, turning on the external load system switch and performing an external start operation for outputting power to the external load system. The method for starting / stopping a fuel cell power plant according to claim 1. 6. The idling mode operation start temperature is 1
The method for starting a fuel cell power plant according to claim 5, wherein the temperature is 50C or higher. 7. In the step of performing the operation of raising the temperature of the fuel cell main body, the battery heating rate from the battery storage temperature to immediately before the idle mode operation and the battery heating rate during the idle mode operation are set to 50 ° C. / h
The battery cooling system is controlled.
The start / stop operation method of the fuel cell power plant described in the above. 8. In the step of performing the temperature raising operation of the fuel cell main body, before the temperature of the fuel cell main body reaches 100 ° C., an inert gas containing a trace amount of hydrogen of 4% or less is supplied to the fuel cell main body. When the battery voltage of the fuel cell body reaches or exceeds a preset voltage suppression start voltage, a dummy resistor is inserted between the fuel electrode and the oxidant electrode of the fuel cell body. 6. The method according to claim 5, wherein the residual voltage is suppressed. 9. A fuel cell main body in which a plurality of unit cells each including a fuel electrode and an oxidant electrode are stacked, a fuel reforming device and an oxidant supply device for supplying fuel and oxidant to the fuel cell main body, respectively. Fuel cell power generation including a battery cooling system for controlling the temperature of the fuel cell main body, an orthogonal transformer connected to the output end of the fuel cell main body, and an external load system switch connecting the orthogonal transformer and the external load system In order to perform a shutdown operation of the plant, the supply of the reformed fuel and the oxidant from the fuel reformer and the oxidant supply device to the fuel cell main body is cut off, and at the same time, an inert gas is supplied to the fuel cell main body. A gas replacement operation to drive out residual gas by using a dummy resistor between a fuel electrode and an oxidant electrode of the fuel cell body, and a residual voltage suppression operation to suppress a residual voltage. A method for stopping a fuel cell power plant, comprising the step of performing a shut-down operation, wherein the inert gas supplied to at least one of a fuel electrode and an oxidant electrode of the fuel cell main body is 0.1% or less. A method for shutting down a fuel cell power plant, comprising a small amount of oxygen. 10. The method according to claim 1, wherein the concentration of oxygen in the inert gas is 0.1.
The method according to claim 9, wherein the amount is 005 to 0.05%. 11. A fuel cell main body in which a plurality of unit cells each including a fuel electrode and an oxidant electrode are stacked, a fuel reformer and an oxidant supply device for supplying fuel and oxidant to the fuel cell main body, respectively. Fuel cell power generation including a battery cooling system for controlling the temperature of the fuel cell main body, an orthogonal transformer connected to the output end of the fuel cell main body, and an external load system switch connecting the orthogonal transformer and the external load system The plant, further comprising: control means for controlling the external load system switch. By supplying an output, it is possible to perform an idle mode operation in which the operation is performed at a minimum load corresponding to a load of only the power system in the plant. Power plant. 12. An inert gas supply device for supplying an inert gas to the fuel cell body, and a dummy resistor connectable between a fuel electrode and an oxidant electrode of the fuel cell body is provided. The control means controls a power generation load based on a stop command to reduce the load to the minimum load during a stop operation of the fuel cell power plant, and after reaching the minimum load, opens the external load switch and opens the idle load switch. At the same time as performing the mode operation, the battery cooling system is controlled to perform a temperature lowering operation of the fuel cell main body. The idle mode operation is stopped, and a main body stop operation including a gas replacement operation and a residual voltage suppression operation is performed. The supply of the reformed fuel and the oxidant from the fuel reforming device and the oxidant supply device to the fuel cell body is interrupted, and at the same time, the inert gas is supplied from the inert gas supply device to the fuel cell body and the residual gas is supplied. The residual voltage suppressing operation is an operation of suppressing the residual voltage by inserting the dummy resistor between a fuel electrode and an oxidant electrode of the fuel cell body. Item 12
A fuel cell power plant as described. 13. The fuel cell power plant according to claim 1, wherein the control unit controls the battery cooling system based on a start command to perform a temperature raising operation of the fuel cell main body at a start operation of the fuel cell power plant. At the time when the temperature rises to the idle mode operation start temperature set lower than the operating temperature, the reforming device and the oxidizing agent supply device supply the reforming fuel and the oxidizing agent to the fuel cell body, respectively, and The idle mode operation is performed, and at the time when the fuel cell body temperature reaches the operating temperature, the external load system switch is turned on, and an external start operation for outputting power to the external load system is performed. The fuel cell power plant according to claim 11, wherein: 14. A trace hydrogen-containing gas supply device for supplying an inert gas containing a trace amount of hydrogen of 4% or less to a fuel electrode of the fuel cell body, and a fuel electrode and an oxidizer electrode of the fuel cell body. A dummy resistor connectable between the fuel cell power plant and the fuel cell power plant, the fuel cell body temperature reaches 100 ° C. during the temperature raising operation of the fuel cell body during the start operation. At an earlier timing, the inert gas containing the trace amount of hydrogen is supplied to the fuel electrode of the fuel cell body from the trace amount hydrogen-containing gas supply device, and the battery voltage of the fuel cell body is set to a preset voltage suppression start voltage. 14. The fuel cell according to claim 13, wherein the dummy resistor is inserted between the fuel electrode and the oxidant electrode of the fuel cell main body at the time when the above described condition is reached to suppress the residual voltage. Cell power plant. 15. A fuel cell main body in which a plurality of unit cells each including a fuel electrode and an oxidant electrode are stacked, a fuel reformer and an oxidant supply device for supplying fuel and oxidant to the fuel cell main body, respectively. An inert gas supply device that supplies an inert gas to the fuel cell body, a battery cooling system that controls the temperature of the fuel cell body, an orthogonal transformation device connected to an output end of the fuel cell body, and the orthogonal transformation device. An external load system switch for connecting an external load system, and a dummy resistor connectable between a fuel electrode and an oxidant electrode of the fuel cell body,
At the time of the stop operation, the supply of the reformed fuel and the oxidant from the fuel reforming device and the oxidant supply device to the fuel cell main body is cut off, and at the same time, the inert gas is supplied from the inert gas supply device to the fuel cell main body. A fuel configured to perform a gas replacement operation to drive out residual gas and a body stop operation including a residual voltage suppression operation to suppress a residual voltage by inserting the dummy resistor into an output terminal of the fuel cell body. In the battery power plant, the inert gas supplied from the inert gas supply device to at least one of the fuel electrode and the oxidant electrode of the fuel cell body may include a small amount of oxygen of 0.1% or less. Characteristic fuel cell power plant.