JP2005158298A - Operation method of fuel cell power generation system, and fuel cell power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that generated voltage is reduced because oxidation of the oxygen containing gas side electrode or adsorption of impurities occurs if starting and shutdown are carried out in a fuel cell power generation system and oxygen is mixed with the fuel electrode which increases the electrode potential and the alloy catalyst is eluted to reduce generation voltage. <P>SOLUTION: This system is provided with a step (step 2) in which the supply of fuel gas and oxidizer gas is shut down and the outside circuit is intercepted when the operation is stopped, and with steps (steps 4, 5) in which sealing is made by purging the system with an inactive gas after temperature difference of the fuel cell and surroundings becomes at least not more than a prescribed temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for operating a fuel cell power generation system and a fuel cell power generation system. For example, the present invention relates to a method for operating a fuel cell power generation system and a fuel cell power generation system using a polymer electrolyte fuel cell.

  A general configuration of a conventional fuel cell will be described in the form of a polymer electrolyte.

  A polymer electrolyte fuel cell is one that obtains electrical energy and thermal energy mainly from hydrogen and oxygen. Due to the catalytic action of Pt or the like, the reaction represented by (Chemical Formula 1) occurs on the fuel electrode side, and the reaction represented by (Chemical Formula 2) occurs on the oxygen-containing electrode. The total reaction is represented by (Chemical Formula 3).

燃料極側では一酸化炭素などによる劣化を防ぐため、Ｐｔの他にもＲｕとの混合物や合金が使用される。これらの作用により燃料電池は、水素と酸素が反応し、反応生成物としては水のみが生成される。環境への影響物質が排出されないのが大きな特徴である。

In order to prevent deterioration due to carbon monoxide or the like on the fuel electrode side, a mixture or alloy with Ru is used in addition to Pt. By these actions, hydrogen and oxygen react in the fuel cell, and only water is produced as a reaction product. A major feature is that no substances that affect the environment are discharged.

  However, since there is no need to move until electricity or heat energy is not needed, there is a need for a “start / stop type” operation that can be started when needed and stopped when not needed.

  However, when starting and stopping, oxidation of the electrode on the oxygen-containing gas side or adsorption of impurities occurs and the generated voltage decreases, and oxygen mixes into the fuel electrode and the potential rises and the alloy catalyst elutes. Therefore, there is a problem that the generated voltage is lowered. Several methods have been considered as starting and stopping methods for solving these problems.

  As such a method, a method is known in which the supply of oxygen-containing gas and fuel gas is stopped and left at the time of stop.

  In addition, in order to keep the ion exchange membrane, which is an electrolyte, in a water retaining state even during storage, a stop / storage method in which humidified inert gas is sealed is known (see, for example, Patent Document 1).

Further, in order to prevent oxidation of the oxygen electrode or adhesion of impurities, a method is known in which durability is improved by generating electric power in a state where the supply of the oxygen-containing gas is stopped and performing an oxygen consumption operation (for example, , See Patent Document 2).
JP-A-6-251788 JP 2002-93448 A

  However, in the method of stopping the supply of the oxygen-containing gas and the fuel gas at the time of stoppage, voltage is generated in the fuel cell as long as the gas remains even if the operation of the fuel cell and the system is stopped. In particular, the circuit is in an open circuit state because no current is taken during the stop. In an open circuit state exceeding 0.9 V, there is a problem that the reaction area is reduced due to particle expansion, which is referred to as elution and sintering of the Pt catalyst of the oxygen-containing electrode.

  In addition, diffusion of oxygen from the air electrode to the fuel electrode, reduction of gas volume inside the battery due to a decrease in battery temperature, oxygen contamination from the outside due to pressure reduction, etc., increase the potential of the fuel electrode and cause the alloy catalyst to be eluted is there.

  Further, when sealed, there is a danger that pinholes are generated in the polymer electrolyte membrane or the like due to the negative pressure inside the battery. On the other hand, if not sealed, there is a possibility that outside air will enter the fuel cell as the gas decreases, humidity may change and impurities may be mixed in, and alloy elution of the fuel electrode and drying of the polymer electrolyte, etc. Therefore, there is a problem that the performance of the fuel cell is lowered.

  Further, in order to keep the ion exchange membrane, which is an electrolyte, in a water retaining state during storage, the temperature of the fuel cell is lowered during the stop in the stop / storage method shown in Patent Document 1 in which humidified inert gas is enclosed. However, since the water vapor provided for humidification is condensed and becomes a liquid, the volume is reduced. And since the inside of a fuel cell becomes a negative pressure, there exists a subject that a pinhole generate | occur | produces in electrolyte etc. or oxygen mixes into a fuel electrode.

  Further, in order to prevent oxidation of the oxygen electrode or adhesion of impurities, power is stopped in a state where the supply of the oxygen-containing gas is stopped, and an oxygen consumption operation is performed to improve durability. Even in the method, if the temperature at the time of the final sealing with the purge gas present in the oxygen electrode after the oxygen consumption operation is high, a pressure reduction state inside the fuel cell occurs, and there is a problem that pinholes are generated in the electrolyte as well. is there.

  An object of the present invention is to provide a method of operating a fuel cell power generation system and a fuel cell power generation system that can reduce deterioration due to start / stop or improve durability by taking the above-described conventional problems into consideration.

In order to solve the above-described problem, the first aspect of the present invention provides:
When stopping operation,
Stopping the supply of fuel gas and oxidant gas and shutting off the external circuit;
And a step of purging with an inert gas and sealing after the temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less.

The second aspect of the present invention
When stopping operation,
A step of stopping the supply of the oxidant gas and shutting off the external circuit while the supply of the fuel gas is continued;
And a step of purging with an inert gas and sealing after the temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less.

The third aspect of the present invention provides
When stopping operation,
Shutting off the external circuit when the output voltage falls below a predetermined voltage after stopping the supply of the oxidant gas in a state where the connection of the fuel gas and the external circuit is continued;
And a step of purging with an inert gas and sealing after the temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less.

The fourth invention relates to
The step of purging with the inert gas and sealing is performed by purging with the inert gas after the temperature difference between the fuel cell and the surroundings is 10 ° C. or less and the voltage of the unit cell is 0.3 V or less. A method for operating the fuel cell power generation system according to any one of the first to third aspects of the present invention, which is sealed.

The fifth aspect of the present invention relates to
The fuel cell power generation system operating method according to any one of the first to fourth aspects of the present invention, wherein the fuel gas is used as the inert gas.

The sixth invention relates to
A fuel cell that is supplied with fuel gas and oxidant gas to generate electricity;
Fuel gas supply means for supplying the fuel gas to the fuel cell;
Oxidant gas supply means for supplying the oxidant gas to the fuel cell;
An inert gas supply means for supplying an inert gas to the fuel cell;
A power circuit unit for extracting power generated by the fuel cell;
Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
Ambient temperature detection means for detecting the ambient temperature;
A fuel cell power generation system comprising an operation control means for controlling operation,
The operation control means, when stopping the operation, stops the supply of the fuel gas and the oxidant gas to the fuel cell and shuts off the external circuit from the fuel cell. In the fuel cell power generation system, the fuel cell is controlled to be purged and sealed with the inert gas after the temperature difference becomes equal to or lower than a predetermined temperature.

The seventh invention relates to
The operation control means, when stopping the operation, stops the supply of the oxidant gas in a state in which the supply of the fuel gas to the fuel cell is continued, and shuts off the external circuit from the fuel cell, The fuel cell power generation system according to the sixth aspect of the present invention, wherein the fuel cell is controlled to be purged and sealed with the inert gas after a temperature difference between the fuel cell and the surroundings is equal to or lower than a predetermined temperature. .

The eighth invention relates to
Furthermore, a fuel cell voltage detection means for detecting the voltage of the fuel cell is provided,
When stopping the operation, the operation control means stops the supply of the oxidant gas while continuing to supply the fuel gas to the fuel cell, and the voltage of the fuel cell becomes a predetermined voltage or less. The external circuit is cut off from the fuel cell, and after the temperature difference between the fuel cell and the surroundings has become a predetermined temperature or less, the fuel cell is purged and sealed with the inert gas. Thus, the fuel cell power generation system of the sixth aspect of the present invention is controlled.

The ninth invention relates to
In the control in which the operation control means purges and seals the fuel cell with the inert gas, the temperature difference between the fuel cell and the surroundings is 10 ° C. or less and the voltage of the unit cell is 0.3 V or less. The fuel cell power generation system according to any one of the sixth to eighth aspects of the present invention to be performed later.

The tenth aspect of the present invention is
The inert gas supply means is the fuel gas supply means, and is the fuel cell power generation system according to any of the sixth to ninth aspects of the present invention, which uses the fuel gas as the inert gas.

The eleventh aspect of the present invention is
A program for causing a computer to function as operation control means for controlling operation of any one of the sixth to tenth fuel cell power generation systems of the present invention.

The twelfth aspect of the present invention is
A recording medium carrying the program of the eleventh aspect of the present invention, which is a recording medium usable by a computer.

  According to the present invention, it is possible to provide a method of operating a fuel cell power generation system and a fuel cell power generation system that can reduce deterioration due to start / stop or improve durability.

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

(Embodiment 1)
FIG. 4 shows a block diagram of the fuel cell power generation system according to Embodiment 1 of the present invention.

  An air supply pipe in which the oxidant gas control device 2 and the total heat exchange type humidifier 9 are installed is connected to the air electrode of the laminated battery 1. And the fuel gas supply pipe which installed the fuel gas control apparatus 3, the fuel generator 10, and the gas cleaning part 8 in the fuel electrode is connected. In addition, an electromagnetic valve 7 is installed in each pipe, and the reaction gas valve is controlled by the control unit 5.

  In the fuel cell power generation system according to the first embodiment, a fuel cell temperature detecting means (not shown) for detecting the temperature of the laminated battery 1 and an ambient temperature detecting means (not shown) for detecting the ambient temperature. Is provided.

  The external circuit 6 is connected to the current collector plate of the laminated battery 1, and the voltage of each cell is observed by the voltage detector 4. Based on the voltage of the cell, the temperature of the laminated battery 1 and the ambient temperature, the control unit 5 controls the oxidant gas control device 2, the fuel gas control device 3, and the electromagnetic valve 7.

  The laminated battery 1, the oxidant gas control device 2, the fuel gas control device 3, the voltage detection device 4, the control unit 5, and the external circuit 6 are respectively the fuel cell, the oxidant gas supply means, and the fuel gas supply of the present invention. It is an example of a means, a fuel cell voltage detection means, an operation control means, and a power circuit part. Further, the oxidant gas control device 2, the fuel gas control device 3, and the electromagnetic valve 7 constitute an inert gas supply means of the present invention.

  The laminated battery 1 is an apparatus in which a fuel gas containing at least hydrogen and an oxidant gas containing oxygen such as air are electrochemically reacted by a gas diffusion electrode, and electricity and heat are generated simultaneously. In the laminated battery 1, a plurality of cells C1, C2,... Cn are laminated.

  FIG. 6 shows a portion of one cell C1 of the fuel cell power generation system shown in FIG. The electrolyte 11 uses a polymer electrolyte membrane that selectively transports hydrogen ions. On both surfaces of the electrolyte 11, catalyst reaction layers 12a and 12c mainly composed of carbon powder supporting a platinum-based metal catalyst are disposed in close contact with each other. Reactions shown in (Chemical Formula 1) and (Chemical Formula 2) occur in the catalyst reaction layers 12a and 12c. The fuel gas containing at least hydrogen performs the reaction shown in (Chemical Formula 1), the hydrogen ions move through the electrolyte 11, and the reaction shown in (Chemical Formula 2) is performed in the oxidant gas and the catalytic reaction layer 12c to generate water. To do. At this time, electricity and heat are generated.

  The side in which fuel gas such as hydrogen is involved is referred to as an anode, and in FIG. 6, a is indicated at the end of the symbol, and the side in which oxidant gas such as air is involved is referred to as the cathode. Yes.

  Further, gas diffusion layers 13a and 13c having both gas permeability and conductivity are disposed in close contact with the outer surfaces of the catalyst reaction layers 12a and 12c. The gas diffusion layer 13a and the catalyst reaction layer 12a form an electrode 14a, and the gas diffusion layer 13c and the catalyst reaction layer 12c form an electrode 14c.

  A membrane electrode assembly (hereinafter referred to as MEA) 17 includes electrodes 14 a and 14 c and an electrolyte 11. The MEA 17 is mechanically fixed, and adjacent MEAs 17 are electrically connected to each other in series. Furthermore, a pair of separator plates 16a formed on the surface in contact with the MEA 17 are provided with gas flow paths 18a and 18c for supplying the reaction gas to the electrodes 14a and 14c and carrying away the gas generated by the reaction or excess gas. 16c. The MEA 17 and the pair of separator plates 16a and 16c form a basic fuel cell (cell).

  Separator plates 16a and 16c are adjacent to separator plates 16c and 16a of adjacent cells on the opposite side of MEA 17, respectively. A cooling water channel 19 is provided on the side where the adjacent separator plate 16a or 16c comes into contact, and the cooling water flows there. The temperature of the MEA 17 is adjusted by the cooling water flowing through the cooling water channel 19 via the separator plates 16a and 16c.

  The MEA 17 and the separator plate 16 a or 16 c are sealed with the MEA gasket 15, and the adjacent separator plates 16 a and 16 c are sealed with the separator gasket 20.

  The electrolyte 11 has a fixed charge, and hydrogen ions exist as a counter ion of the fixed charge. The electrolyte 11 is required to have a function of selectively permeating hydrogen ions. For this reason, the electrolyte 11 needs to retain moisture. When the electrolyte 11 contains moisture, the fixed charge fixed in the electrolyte 11 is ionized, hydrogen which is a counter ion of the fixed charge is ionized, and the moisture in the electrolyte 11 moves from the anode to the cathode through the movement path. , Expresses ionic conductivity.

  Next, a method for stopping the operation of the fuel cell power generation system of Embodiment 1 will be described.

  FIG. 1 is a schematic diagram of the time change of each parameter when the operation of stopping the operation of the fuel cell power generation system according to Embodiment 1 is performed.

  First, in Step 1, the battery temperature was 70 ° C., 1 kW was generated with humidified air and humidified reformed gas (SRG), and the average cell voltage was 0.75V.

  Next, in step 2, the supply of humidified air and humidified SRG was stopped and sealed, and the cooling of the battery was started and the external output was stopped. At this time, the battery voltage gradually decreased, and the average cell voltage became about 0.1 to 0.15V. This is a result of the potential of both electrodes approaching due to the natural diffusion of oxygen at the air electrode to the fuel electrode and hydrogen from the fuel electrode to the air electrode.

  In the configuration of a normal fuel cell, since the flow volume of the air electrode and the flow volume of the fuel electrode are almost the same, when hydrogen and oxygen diffuse and react, hydrogen exists in excess, so The potential goes to 0V with respect to the standard hydrogen electrode.

  In step 3, both electrodes are in a sealed state until the battery temperature reaches room temperature (RT) + 10 ° C. At this time, since the battery temperature is lowered, both electrodes are under negative pressure due to shrinkage of gas volume, condensation of water vapor, and cross leak of hydrogen and oxygen. In particular, since the fuel electrode has a large hydrogen permeation coefficient of the polymer electrolyte 11, the fuel electrode has a considerably negative pressure. Note that the room temperature (RT) + 10 ° C. shown here is an example of the predetermined temperature of the present invention.

  Next, in step 4, after purging an amount capable of gas replacement with an inert gas, it was sealed and stopped. As a result, both electrodes, which were negative pressure, became normal temperature and normal pressure, and the voltage was also 0V.

  By stopping the fuel cell power generation system by the above method, purge and seal with an inert gas after the temperature is sufficiently lowered, so that the fuel cell interior is not left under negative pressure during the stop, Damage to the polymer electrolyte membrane can be eliminated. In addition, there is no external oxygen mixing, and the oxidation of the air electrode and the elution of the alloy catalyst of the fuel electrode can be suppressed, and a fuel cell power generation system with little deterioration at the time of starting and stopping can be realized.

(Embodiment 2)
A method for stopping the operation of the fuel cell power generation system according to Embodiment 2 of the present invention will be described. The configuration of the fuel cell power generation system of the second embodiment is the same as that of the first embodiment shown in FIG. 4, and the operation method is different from that of the first embodiment.

  FIG. 2 is a schematic diagram of the time change of each parameter when the operation of stopping the operation of the fuel cell power generation system according to the second embodiment is performed.

  In the first embodiment, the supply of humidified SRG to the fuel electrode is stopped and sealed in steps 2 and 3, whereas in this second embodiment, the SRG is distributed to the fuel electrode in steps 2 and 3. Different.

  By causing SRG to flow through the fuel electrode, the fuel electrode does not become negative pressure, and the fuel electrode does not have negative pressure even at the air electrode, so the amount of hydrogen crossover increases compared to the first embodiment, and the pressure Decrease is reduced. Therefore, compared with Embodiment 1, damage to the electrolyte 11 can be further reduced, and mixing of oxygen from the outside hardly occurs.

  Here, the potential of the electrode is determined by the gas partial pressure of the reaction gas, and approaches 0 V as the hydrogen partial pressure increases at the fuel electrode. Also at the air electrode, the oxygen partial pressure is low, and when the hydrogen partial pressure is high, it gradually approaches 0V. Therefore, by distributing SRG to the fuel electrode, the hydrogen partial pressure is maintained high in the fuel electrode as well as in the first embodiment, and hydrogen from the fuel electrode crosses over to the air electrode as well. The partial pressure increases. As a result, the potentials of both electrodes are surely fixed near 0 V, and the catalytic oxidation of the air electrode and the elution of the alloy catalyst of the fuel electrode can be suppressed. Further, by reducing the potential of the air electrode, the catalyst of the air electrode is cleaned up, and the power generation characteristics are restored.

  Since the fuel cell power generation system is stopped by the method of the second embodiment, the temperature is sufficiently lowered while the SRG is circulated through the fuel electrode, and then purged and sealed with an inert gas. Does not become negative pressure. Therefore, damage to the electrolyte 11 can be eliminated. Further, oxygen in the air electrode can be consumed reliably, and alloy catalyst elution due to oxygen diffusion to the fuel electrode can be suppressed. In addition, since the oxidation of the air electrode and the elution of the alloy catalyst of the fuel electrode can be suppressed without mixing oxygen from the outside, it is possible to realize a fuel cell power generation system with little deterioration at the time of starting and stopping.

(Embodiment 3)
A method for stopping the operation of the fuel cell power generation system according to Embodiment 3 of the present invention will be described. The configuration of the fuel cell power generation system of the third embodiment is the same as that of the first embodiment shown in FIG. 4, and the operation method is different from that of the first and second embodiments.

  FIG. 3 is a schematic view of the time change of each parameter when the operation of stopping the operation of the fuel cell power generation system according to Embodiment 3 is performed.

  In Embodiment 1, the supply of humidified SRG to the fuel electrode was stopped and sealed in Steps 2 and 3, whereas in Embodiment 3, SRG was distributed to the fuel electrode in Steps 2 and 3. The difference is that the external output is not cut off until the battery voltage drops. In the third embodiment, after the supply of humidified air to the air electrode is stopped and sealed in step 2, the output of the laminated battery 1 is about 0.05 V, which is the saturation value of the unit cell voltage. The external output is shut off after detection by the voltage detector 4. This saturation value of the unit cell voltage is an example of the predetermined voltage of the present invention.

  By causing SRG to flow through the fuel electrode, the fuel electrode does not become negative pressure and the potential of the fuel electrode is fixed at 0 V, as in the second embodiment.

  In addition, since the normal output of the fuel cell occurs until the oxygen in the air electrode is no longer consumed because the external output is not shut down until the voltage drops, oxygen in the air electrode is quickly consumed by the power generation reaction, and the air electrode is promptly consumed. Approaches 0V. Therefore, as compared with Embodiments 1 and 2, the time for which the air electrode catalytic oxidation occurs at a high potential is shortened. Further, since oxygen is consumed quickly, elution of the alloy catalyst due to oxygen diffusion to the fuel electrode can be suppressed. Further, by reducing the potential of the air electrode, the catalyst of the air electrode is cleaned up, and the power generation characteristics are restored.

  In addition, since the external output is not cut off until the voltage drops, the reaction shown in (Chemical Formula 1) occurs on the fuel electrode side after oxygen consumption, and the reaction expressed by (Chemical Formula 4) occurs on the air electrode. In Embodiments 1 and 2, the potential of the air electrode approaches 0 V due to hydrogen crossover due to natural diffusion, whereas in Embodiment 3, the reactions of (Chemical Formula 1) and (Chemical Formula 4) occur. As a result, hydrogen actively crosses over and the potential of the air electrode approaches 0V promptly. Therefore, also in this respect, compared with Embodiments 1 and 2, the time during which the air electrode catalytic oxidation occurs at a high potential is shortened.

本実施の形態３の方法で燃料電池発電システムを停止させることにより、燃料極にＳＲＧを流通させながら温度が十分に低下した後に不活性ガスでパージ・封止されるので、停止中に燃料電池内部が負圧になることがない。また、電解質１１へのダメージをなくすことができる。また、外部からの酸素混入もなく空気極の酸化および燃料極の合金触媒の溶出も抑制できるので、起動停止時の劣化が少ない燃料電池発電システムを実現できる。

By stopping the fuel cell power generation system by the method of the third embodiment, the temperature is sufficiently lowered while circulating the SRG to the fuel electrode, and then purged and sealed with an inert gas. There is no negative pressure inside. Further, damage to the electrolyte 11 can be eliminated. In addition, since the oxidation of the air electrode and the elution of the alloy catalyst of the fuel electrode can be suppressed without mixing oxygen from the outside, it is possible to realize a fuel cell power generation system with little deterioration at the time of starting and stopping.

  In the third embodiment, the saturation value of the unit cell voltage is used as an example of the predetermined voltage that is a condition for cutting off the external output in Step 2, but it is not always necessary to use this voltage value. Even a voltage that does not reach the saturation value of the unit cell voltage may be controlled so that the external output is cut off by setting the voltage value at which the effect of the present invention is obtained as a predetermined voltage.

  In each embodiment, the raw material gas cleaned by the gas cleaning unit 8 may be used as an inert gas for purging. In this case, there is no need for special preparation such as a nitrogen cylinder, the stop operation shown in each embodiment can be realized without complicating the system, and a fuel cell power generation system with less deterioration at the start and stop can be realized at lower cost. it can.

  The present invention also provides an electrolyte, a pair of electrodes sandwiching the electrolyte, a fuel cell including a pair of separator plates having a gas flow path for supplying and discharging fuel gas to one of the electrodes and supplying and discharging oxygen-containing gas to the other, A fuel generator for generating fuel gas to be supplied from the source gas to the fuel cell, a gas cleaning unit for removing components that adversely affect the fuel cell from the source gas, a power circuit unit for extracting power from the fuel cell, and a gas or power circuit unit Any fuel cell power generation system having a control unit for controlling the above may be used, and the present invention is not limited to the configuration shown in each embodiment.

  Next, the operation method of the fuel cell power generation system of the present invention will be described more specifically using examples. In addition, this invention is not limited only to these Examples.

  First, a method for producing a polymer fuel cell used in this example will be described.

  Carbon powder acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 35 nm) was mixed with an aqueous dispersion of polytetrafluoroethylene (PTFE) (D1 manufactured by Daikin Industries, Ltd.) and dried. A water repellent ink containing 20% by weight of PTFE was prepared. This ink is applied and impregnated on carbon paper (TGPH060H manufactured by Toray Industries, Inc.) serving as a base material for the gas diffusion layer, heat treated at 300 ° C. using a hot air dryer, and the gas diffusion layer (about 200 μm). ) Was formed.

  On the other hand, 66 parts by weight of a catalyst body (50 wt% Pt) obtained by supporting a Pt catalyst on Ketjen Black (Ketjen Black EC, Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder. Is mixed with 33 parts by weight (polymer dry weight) of perfluorocarbon sulfonic acid ionomer (5% by weight Nafion dispersion manufactured by Aldrich, USA) which is a hydrogen ion conductive material and a binder, and the resulting mixture is molded. Thus, a catalyst layer (10 to 20 μm) was formed.

  Then, the catalyst layer prepared above is bonded to both surfaces of the polymer electrolyte membrane (Nafion 112 film manufactured by DuPont, USA), and the gas diffusion layer prepared above is bonded to both surfaces of the polymer electrolyte membrane (MEA). Was made.

  Next, a method for manufacturing the fuel cell used in this example will be described with reference to FIGS. FIG. 6 shows a part of one cell of the fuel cell.

  A rubber gasket plate 15 was joined to the outer periphery of the polymer electrolyte membrane 11 of the MEA 17 produced as described above, and manifold holes for circulating cooling water, fuel gas, and oxidant gas were formed.

  On the other hand, two types of separator plates were prepared: a separator plate 16a having a fuel gas passage 18a having a depth of 0.5 mm and a separator plate 16b having an oxidant gas passage 18b having a depth of 0.5 mm. Each of the separator plates 16a and 16b is formed of a graphite plate impregnated with a phenol resin having an outer dimension of 20 cm × 32 cm × 1.3 mm and having a cooling water channel 19 having a depth of 0.5 mm. .

  The separator plates 16a and 16b were used one by one, the separator plate 16b formed with the oxidant gas flow path 18b was superimposed on the cathode side surface of the MEA 17, and the fuel gas flow path 18a was formed on the anode side surface. Separator plates 16a were stacked to obtain a single cell. The unit cells were stacked, the cooling water flow path 19 was formed between the unit cells, and a 70-cell stacked battery (stack) was produced.

A stainless steel current collector plate, an insulating plate made of an electrically insulating material, and an end plate were arranged at both ends of the stack, and the whole was fixed with a fastening rod. The fastening pressure at this time was 15 kgf / cm ² per separator area. In this way, a fuel cell used in this example was produced.

  The fuel cell thus produced was connected to the fuel cell power generation system shown in FIG. 4 as the laminated battery 1, and an evaluation test was performed.

  In the evaluation test, the fuel cell power generation system shown in FIG. 4 is supplied with 13A gas as the source gas and air as the oxidant gas, the cell temperature is 70 ° C., the fuel gas utilization rate (Uf) is 70%, and the air. The discharge test was conducted under the condition of a utilization factor (Uo) of 40%. The fuel gas and air were humidified so as to have dew points of 65 ° C. and 70 ° C., respectively. As the purge gas, 13A gas that passed through the gas cleaning unit 8 was used.

(Example 1)
Step 1: 80 minutes, Step 2 + 3: 40 minutes, Step 4: 10 minutes, Step 5: 40 minutes, Room temperature (RT): 25 ° C. The sequence shown in FIG. In step 2, the average single cell voltage saturated to 0.13 V in about 20 minutes. At the end of Step 3, the laminated battery temperature was 35 ° C. (RT + 10 ° C.).

(Example 2)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of step 3 was set to 30 ° C. (RT + 5 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1.

(Example 3)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of step 3 was set to 40 ° C. (RT + 15 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1.

Example 4
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of Step 3 was set to 40 ° C. (RT + 5 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1 to room temperature (RT): 35 ° C.

(Example 5)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of Step 3 was set to 45 ° C. (RT + 10 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1 to room temperature (RT): 35 ° C.

(Example 6)
Step 2 + 3: 5000 cycles were performed in the same sequence as in Example 1 except that the time was 17 minutes. However, the temperature of the laminated battery at the end of step 3 was set to 35 ° C. (RT + 10 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1. The average single cell voltage at the end of Step 3 was 0.3V.

(Example 7)
Step 1: 80 minutes, Step 2 + 3: 40 minutes, Step 4: 10 minutes, Step 5: 40 minutes, Room temperature (RT): 25 ° C. The sequence shown in FIG. In step 2, the average single cell voltage saturated to 0.13 V in about 25 minutes. At the end of Step 3, the laminated battery temperature was 35 ° C. (RT + 10 ° C.).

(Example 8)
Step 1: 80 minutes, Step 2 + 3: 40 minutes, Step 4: 10 minutes, Step 5: 40 minutes, Room temperature (RT): 25 ° C. The sequence shown in FIG. In step 2, the average single cell voltage was saturated to 0.05 V about 5 minutes after the air supply was stopped. After the external output was cut off, the voltage gradually increased and saturated to 0.13V. At the end of Step 3, the laminated battery temperature was 35 ° C. (RT + 10 ° C.).

(Comparative Example 1)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of Step 3 was set to 50 ° C. (RT + 25 ° C.) by adjusting the flow rate of the cooling water of the laminated battery.

(Comparative Example 2)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of Step 3 was set to 50 ° C. (RT + 15 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1 to room temperature (RT): 35 ° C.

(Comparative Example 3)
5000 cycles were carried out in the same sequence as in Example 1. However, the temperature of the laminated battery at the end of Step 3 was set to 55 ° C. (RT + 20 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1 to room temperature (RT): 35 ° C.

(Comparative Example 4)
Step 2 + 3: 5000 cycles were performed in the same sequence as in Example 1 except that the time was 12 minutes. However, the temperature of the laminated battery at the end of step 3 was set to 35 ° C. (RT + 10 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1. The average single cell voltage at the end of Step 3 was 0.35V.

(Comparative Example 5)
Step 2 + 3: 5000 cycles were performed in the same sequence as in Example 1 except that the time was 10 minutes. However, the temperature of the laminated battery at the end of step 3 was set to 35 ° C. (RT + 10 ° C.) by adjusting the flow rate of the cooling water of the laminated battery 1. The average single cell voltage at the end of Step 3 was 0.5V.

  The results of the cycle tests of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Tables 1 to 4.

実施例１、７、８のサイクル試験の結果を表１に示した。これらは、それぞれ、実施の形態１〜３に示した本発明の運転方法による結果である。

The results of the cycle tests of Examples 1, 7, and 8 are shown in Table 1. These are the results according to the operation method of the present invention shown in the first to third embodiments.

  These differ in the gas state of the fuel electrode in step 2 and the connection with the external circuit. Although the cycle deterioration rate was almost the same under any condition, the conditions of Examples 7 and 8 were slightly better. This is presumably because, in Examples 7 and 8, since Step 3 has passed with sufficient hydrogen present in the fuel electrode, the fuel electrode side is not under negative pressure at Step 3. As a result, damage to the electrolyte 11 and the like can be reduced, and the potential on the air electrode side can be quickly and surely lowered. Therefore, it is considered that cleanup of the air electrode catalyst is performed more effectively.

実施例１、６、比較例４、５のサイクル試験の結果を表２に示した。

Table 2 shows the results of the cycle tests of Examples 1 and 6 and Comparative Examples 4 and 5.

  These have the same inert gas purge start temperature and purge conditions, but the battery voltage drop time in step 2 + 3 is different, and the average single cell voltage just before each purge is 0.13, 0.3, 0.35. 0.5V.

The cycle deterioration rate under these conditions was low in Examples 1 and 6 in which the final average voltage was up to 0.3V, but in Comparative Examples 4 and 5 in which the final average voltage exceeded 0.3V, the cycle deterioration was The rate suddenly increased. This is because in the case of Comparative Examples 4 and 5, the battery voltage drop time is short, that is, the consumption of oxygen in the electrode is not sufficient, so that the air electrode is not cleaned up.

  From this result, it can be seen that the presence of the hydrogen-containing gas on the fuel electrode side until the average single cell voltage becomes 0.3 V or less is effective in preventing deterioration of the fuel cell.

実施例１、２、３、比較例１のサイクル試験の結果を表３に、実施例４、５、比較例２、３のサイクル試験の結果を表４に、それぞれ示した。

The results of the cycle tests of Examples 1, 2, 3 and Comparative Example 1 are shown in Table 3, and the results of the cycle tests of Examples 4, 5 and Comparative Examples 2, 3 are shown in Table 4, respectively.

  These are summarized in one table when the battery cooling rate up to Step 3 is changed and only the start temperature of the inert gas purge is different. Table 3 shows the case where the room temperature (RT) is 25 ° C. Indicates the case where the room temperature (RT) is 35 ° C., respectively.

  From Table 3, when the room temperature (RT) is 25 ° C., the cycle deterioration rates when the purge start temperature is 35, 30, 45, and 50 ° C. are 15, 15, 20, and 30 μV / time, respectively, and the inert gas purge The cycle deterioration rate increases as the starting temperature increases, that is, as the temperature drop (ΔT) from the sealing to room temperature increases. Table 4 shows the same behavior when the room temperature (RT) is 35 ° C., and the cycle deterioration rates when the purge start temperature is 40, 45, 50, and 55 ° C. are 15, 15, 25, and 40 μV, respectively. / Times.

  Also, Tables 3 and 4 show the results of measuring the final battery pressure in Step 5. Naturally, it can be seen that the amount of decrease in the battery pressure is proportional to ΔT. Furthermore, the cycle deterioration rate increases in proportion to the amount of decrease in the battery pressure. That is, it is considered that the deterioration of the cycle is caused by damage to the electrolyte 11 due to pressure fluctuation due to start / stop, or catalyst poisoning due to mixing of oxygen or contamination from the outside.

  In addition, when considering that the power generated by the fuel cell has a merit as a running cost with respect to the power of a general large-scale power plant, the allowable range of cycle deterioration of start and stop is about 80 cycles at a decrease of 80 mV, that is, 20 μV / time or less. From Tables 3 and 4, it can be said that it is preferable that the amount of decompression at the stop is within 0.1 atg in order to make the cycle deterioration rate 20 μV / time or less.

  The graph of FIG. 5 shows the amount of pressure reduction that occurs when RT + ΔT fully humidified gas is sealed in a fuel cell and cooled to room temperature (RT). It agrees well with the result of the reduced pressure.

  That is, it can be said that ΔT in which the amount of reduced pressure falls within 0.1 atg is preferable in the normal room temperature range of 0 to 50 ° C. From the calculation result shown in the graph of FIG. 5, it is understood that ΔT is preferably 10 ° C. or less. .

  The program of the present invention is a program for causing a computer to execute the function of the operation control means of the fuel cell power generation system of the present invention described above, and is a program that operates in cooperation with the computer.

  The recording medium of the present invention is a recording medium carrying a program for causing a computer to execute the function of the operation control means of the above-described fuel cell power generation system of the present invention. The recording medium is used in cooperation with the computer.

  Further, one usage form of the program of the present invention may be an aspect in which the program is recorded on a computer-readable recording medium and operates in cooperation with the computer.

  The recording medium includes a ROM and the like, and the transmission medium includes a transmission medium such as the Internet, light, radio waves, sound waves, and the like.

  The computer of the present invention described above is not limited to pure hardware such as a CPU, and may include firmware, an OS, and peripheral devices.

  As described above, the configuration of the present invention may be realized by software or hardware.

  An operation method of a fuel cell power generation system and a fuel cell power generation system according to the present invention have an effect of reducing deterioration due to start / stop or improving durability, and a fuel cell power generation system using a polymer electrolyte fuel cell. It is useful as an operation method and a fuel cell power generation system.

FIG. 3 is a sequence diagram showing a control method when the fuel cell power generation system according to Embodiment 1 of the present invention is stopped. FIG. 9 is a sequence diagram showing a control method when the fuel cell power generation system according to Embodiment 2 of the present invention is stopped. FIG. 9 is a sequence diagram showing a control method when the fuel cell power generation system according to Embodiment 3 of the present invention is stopped. Configuration diagram of fuel cell power generation system of each embodiment of the present invention Graph showing the amount of pressure reduction inside the fuel cell after purging and sealing, obtained by calculation The figure which shows the structure of the cell of the fuel cell power generation system of each embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stacked battery 2 Oxidant gas control apparatus 3 Fuel gas control apparatus 4 Voltage detection apparatus 5 Control part 6 External circuit 7 Solenoid valve 8 Gas purification part 9 Total heat exchange type humidifier 10 Fuel generator 11 Electrolyte 12a, 12c Catalytic reaction layer 13a, 13c Gas diffusion layer 14a, 14c Electrode 15 MEA gasket 16a, 16c Separator plate 17 MEA
18a, 18c Gas flow path 19 Cooling water flow path 20 Separator gasket

Claims (12)

When stopping operation,
Stopping the supply of fuel gas and oxidant gas and shutting off the external circuit;
A method for operating a fuel cell power generation system, comprising: purging with an inert gas and sealing after a temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less. When stopping operation,
A step of stopping the supply of the oxidant gas and shutting off the external circuit while the supply of the fuel gas is continued;
A method for operating a fuel cell power generation system, comprising: purging with an inert gas and sealing after a temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less. When stopping operation,
Shutting off the external circuit when the output voltage falls below a predetermined voltage after stopping the supply of the oxidant gas in a state where the connection of the fuel gas and the external circuit is continued;
A method for operating a fuel cell power generation system, comprising: purging with an inert gas and sealing after a temperature difference between the fuel cell and the surroundings is at least a predetermined temperature or less.   The step of purging with the inert gas and sealing is performed by purging with the inert gas after the temperature difference between the fuel cell and the surroundings is 10 ° C. or less and the voltage of the unit cell is 0.3 V or less. The operation method of the fuel cell power generation system according to claim 1, wherein the sealing is performed.   The operation method of the fuel cell power generation system according to any one of claims 1 to 4, wherein the fuel gas is used as the inert gas. A fuel cell that is supplied with fuel gas and oxidant gas to generate electricity;
Fuel gas supply means for supplying the fuel gas to the fuel cell;
Oxidant gas supply means for supplying the oxidant gas to the fuel cell;
An inert gas supply means for supplying an inert gas to the fuel cell;
A power circuit unit for extracting power generated by the fuel cell;
Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
Ambient temperature detection means for detecting the ambient temperature;
A fuel cell power generation system comprising an operation control means for controlling operation,
The operation control means, when stopping the operation, stops the supply of the fuel gas and the oxidant gas to the fuel cell and shuts off the external circuit from the fuel cell. A fuel cell power generation system that controls the fuel cell to be purged and sealed with the inert gas after the temperature difference becomes equal to or lower than a predetermined temperature.   The operation control means, when stopping the operation, stops the supply of the oxidant gas in a state in which the supply of the fuel gas to the fuel cell is continued, and shuts off the external circuit from the fuel cell, The fuel cell power generation system according to claim 6, wherein the fuel cell is controlled to be purged and sealed with the inert gas after a temperature difference between the fuel cell and the surroundings becomes a predetermined temperature or less. Furthermore, a fuel cell voltage detection means for detecting the voltage of the fuel cell is provided,
When stopping the operation, the operation control means stops the supply of the oxidant gas while continuing to supply the fuel gas to the fuel cell, and the voltage of the fuel cell becomes a predetermined voltage or less. The external circuit is cut off from the fuel cell, and after the temperature difference between the fuel cell and the surroundings has become a predetermined temperature or less, the fuel cell is purged and sealed with the inert gas. The fuel cell power generation system according to claim 6, which is controlled as follows.   In the control in which the operation control means purges and seals the fuel cell with the inert gas, the temperature difference between the fuel cell and the surroundings is 10 ° C. or less and the voltage of the unit cell is 0.3 V or less. The fuel cell power generation system according to any one of claims 6 to 8, which is performed later.   The fuel cell power generation system according to any one of claims 6 to 9, wherein the inert gas supply means is the fuel gas supply means, and the fuel gas is used as the inert gas.   A program for causing a computer to function as operation control means for controlling operation of the fuel cell power generation system according to any one of claims 6 to 10. A recording medium carrying the program according to claim 11, which is usable by a computer.

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