JP2003208912A - Fuel cell power generation system - Google Patents

Abstract

(57) [Problem] To provide a fuel cell system advantageous for securing an appropriate humidification state inside a fuel cell. A humidifying unit has a humidifying member that can absorb moisture. The humidifying member 20n is humidified by the off-gas of the reaction gas discharged from the fuel cell 8 after power generation, and the reaction gas before power generation toward the fuel cell 8 is humidified by the humidifying member 20n. A fuel cell humidification state detecting means for detecting a humidification state inside the fuel cell 8 based on a dimensional change in the stacking direction of the fuel cell 8 or a load change in the stacking direction is provided. According to the humidification state of the fuel cell, the amount of off-gas of the reaction gas after power generation from the fuel cell 8 to the bypass passage 202 without passing through the humidification unit 20 is made variable. Therefore, the amount of off-gas of the reaction gas after power generation toward the humidifying section 20 is made variable. For this reason, the moisture in the humidifying member 20n is made variable, and the humidification state of the reaction gas before power generation supplied to the fuel cell 8 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system having a humidifying section for humidifying a reaction gas such as an oxygen-containing gas.

[0002]

2. Description of the Related Art Conventionally, as a fuel cell system, a fuel cell for generating electric power with a reaction gas, a supply passage for supplying the reaction gas to the fuel cell, and an off gas for passing an off gas of the reaction gas discharged from the fuel cell after power generation There is known one having a passage and a humidifying section having a humidifying member capable of absorbing moisture.
If the inside of the fuel cell is too dry, the power generation performance will not be sufficiently exhibited, so that the reaction gas such as the oxygen-containing gas before power generation supplied to the fuel cell is generally humidified.
Therefore, the reaction gas discharged from the fuel cell to the off-gas passage after power generation often has moisture.

In the above fuel cell power generation system, the offgas of the reaction gas after power generation, which is discharged from the fuel cell and flows through the offgas passage, is directed to the humidification member of the humidification section, and the reaction gas after power generation and the humidification member are brought into contact with each other. The humidifying member is humidified by transferring the moisture content of the reaction gas after power generation to the humidifying member. Then, by bringing the reaction gas before power generation supplied to the fuel cell into contact with the humidification member, the moisture of the humidification member is transferred to the reaction gas before power generation, and the reaction gas before power generation is humidified. According to this, the reaction gas supplied to the fuel cell before power generation can be humidified, so that the inside of the fuel cell can be prevented from being excessively dried, and power generation performance can be secured.

Further, in Japanese Unexamined Patent Publication No. 2001-143733, a humidifying portion is provided in an offgas passage through which the offgas of the fuel system gas discharged from the fuel cell after power generation flows, and a passage portion connecting the fuel cell and the humidifying portion in the offgas passage. There is disclosed a humidifying device for a fuel cell system in which a bypass passage that connects a hydrogen generator with a hydrogen generator is provided, and a compressor is provided in the bypass passage. In this device, the off gas of the fuel system gas after power generation discharged from the fuel cell is made to flow to the humidification part through the off gas passage, and a part of the fuel system gas after power generation is generated by the compressor without passing through the humidification part. I will return to.

Further, Japanese Patent Laid-Open No. 2001-155752 discloses a technique for reducing the amount of humidification to the fuel cell when the pressure of the fuel cell is high and increasing the amount of humidification to the fuel cell when the pressure of the fuel cell is low. There is. In addition, JP 20
In 01-148253, the pressure loss of the fuel or the oxidant gas when passing through the fuel cell, the time difference value or the time differential value of the single cell voltage output is obtained, and this is compared with a preset set value, and the fuel or the oxidant is discharged. A technique for detecting excessive humidification of the agent gas and raising the temperature of the battery is disclosed.

In Japanese Unexamined Patent Publication No. 7-22047, the potential between the anode and the cathode of a unit cell is calculated by a computer, the cause of the output decrease of the unit cell is estimated based on the change in the potential, and the estimation is performed. Based on this, a technique is disclosed in which a humidifier is controlled to adjust the amount of humidification for hydrogen gas or oxygen gas.

Japanese Unexamined Patent Publication (Kokai) No. 9-55218 discloses a technique for humidifying a reaction gas by introducing hot water after cooling a fuel cell into a humidifier. Japanese Patent Laid-Open No. 6-132038
The publication discloses a humidifier having a humidifying chamber facing one surface of a water vapor permeable membrane having a hygroscopic property and a humidified chamber facing the other surface of the water vapor permeable membrane, which is supplied to a fuel cell before power generation. A technique is disclosed in which the reaction gas is passed through the humidification chamber and the off-gas after power generation discharged from the fuel cell is passed through the humidification chamber.

Japanese Unexamined Patent Publication No. 2001-216984 discloses a fuel cell humidifying system for controlling the humidifying amount of a fuel cell by opening and closing a bypass passage according to the required humidifying amount of the fuel cell.

[0009]

According to the above fuel cell system, it is not always sufficient to secure an appropriate humidified state inside the fuel cell.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a fuel cell system which is advantageous for ensuring an appropriate humidification state inside the fuel cell.

[0011]

A fuel cell power generation system according to the present invention includes a fuel cell for generating power with a reaction gas, a supply passage for supplying the reaction gas to the fuel cell, and an off gas of the reaction gas after power generation as a fuel. An off-gas passage discharged from the battery, and a humidifying member that is connected to the supply passage and the off-gas passage and can absorb moisture, the humidifying member absorbs moisture in the off-gas of the reaction gas discharged from the fuel cell after power generation,
In a fuel cell power generation system having a humidifying section that humidifies a reaction gas before power generation toward the fuel cell with a humidifying member,
A fuel cell humidified state detecting means for detecting a dimensional change in the stacking direction or a load change in the stacking direction due to wetting of the fuel cell, and detecting a humidified state inside the fuel cell based on the dimensional change or the load change; Depending on the humidification state of the fuel cell detected by the humidification state detection means, the amount of off-gas of the reaction gas after power generation from the fuel cell to the humidification section can be varied to change the moisture content in the humidification section of the humidification section. And humidifying control means for controlling the humidifying state of the reaction gas supplied to the fuel cell before power generation.

In the present invention, the reaction gas before power generation means the reaction gas before being supplied to the power generation reaction in the fuel cell, and at least one of hydrogen-containing gas and oxygen-containing gas is exemplified. The off-gas after power generation means the off-gas used for power generation reaction in the fuel cell and discharged from the fuel cell, and may have unreacted components.

According to the present invention, the off-gas of the reaction gas after power generation has a moisture content and humidifies the humidifying member of the humidifying section. The humidifying member of the humidifying section comes into contact with the reaction gas before power generation, which is directed to the fuel cell. Therefore, the humidified humidifying member humidifies the reaction gas before power generation toward the fuel cell. The fuel cell humidified state detecting means detects a dimensional change in the stacking direction of the fuel cell or a load change in the stacking direction due to humidification, and also detects a humidified state inside the fuel cell based on the dimensional change or the load change. In accordance with the humidification state of the fuel cell detected by the fuel cell humidification state detection means, the humidification control means varies the amount of off-gas of the reaction gas from the fuel cell toward the humidification part after power generation. As a result, the moisture content in the humidifying member of the humidifying section is variable. As a result, the humidification state of the reaction gas supplied to the fuel cell before power generation is variably controlled.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION
It detects a dimensional change in the stacking direction of the fuel cell or a load change in the stacking direction due to humidification, and detects a humidified state inside the fuel cell based on the dimensional change or the load change. In this case, the fuel cell may be contacted for detection, or may be contactlessly detected. As the fuel cell humidified state detecting means, it is possible to adopt a form of a load meter arranged so as to be able to detect a load change in the stacking direction of the fuel cells between the base portion holding the fuel cells and the fuel cells. The load meter may be provided between the facing portion of the base portion facing the end portion of the fuel cell in the stacking direction and the end portion of the fuel cell in the stacking direction. As the fuel cell humidified state detecting means,
It is possible to employ one that detects a stress state in at least a part of a base portion that holds the fuel cell, and detects a humidification state inside the fuel cell based on the stress state.

Therefore, as the fuel cell humidified state detecting means,
Load detecting means having a detecting portion for detecting a load change in the stacking direction of the fuel cell, length detecting means having a detecting portion for detecting a length that changes with a dimensional change in the stacking direction of the fuel cell, and holding the fuel cell It is possible to employ a stress state detection means having a detection unit for detecting a stress state (compression stress generation state or tensile stress generation state) in the frame or the fuel cell. As the length detection means having a detection unit for detecting the length that changes with the dimensional change in the stacking direction of the fuel cell,
Capacitance detection means having a detection unit that detects capacitance that changes with dimensional changes in the stacking direction of the fuel cell, and magnetic detection that has a detection unit that detects magnetism that changes with dimensional changes in the stacking direction of the fuel cell. Some form of at least one of the means can be adopted.

It is possible to provide an off-gas amount varying means for varying the amount of off-gas after power generation, which is directed to the humidifying section.
The off-gas amount varying means has a bypass passage bypassing the humidifying portion so as not to flow through the humidifying portion, and a gas passage amount changing means for varying the gas amount of the reaction gas toward the bypass passage. The gas passage amount changing means can be gas conveying means such as a valve or a pump that can change the gas amount of the reaction gas passing through the bypass passage.

The humidifying section has a humidifying member. The moisturizing member may have any moisture retention property. When the humidifying member separates the flow path of the offgas of the reaction gas after power generation from the flow path of the reaction gas before power generation, the humidification member mixes the gas before power generation and the gas after power generation. In order not to do so, it is preferable that the gas barrier property is high. An example of such a humidifying member is an ion exchange membrane having both moisture retention and gas barrier properties.

The humidifying control means controls the dimension value or load value in the stacking direction of the fuel cell to reach the target value, and when the cumulative operating time of the fuel cell becomes long, the target value of the dimension value or load value Can be adopted. It is possible to deal with fatigue of materials inside the fuel cell.

The reaction gas supplied to the humidifying section may be an oxidant gas, or a fuel gas in some cases. As the oxidant gas, generally, an oxygen-containing gas such as air or an oxygen-rich gas can be used. As a typical fuel system gas, hydrogen gas or a gas containing hydrogen as a main component can be used. Examples of the gas containing hydrogen as a main component include hydrogen-rich reformed gas obtained by reforming hydrocarbon fuel such as methane, propane, butane, natural gas and gasoline, and alcohol fuel such as methanol. The fuel cell can be exemplified by a system in which battery cells are stacked. The fuel cell may be a commercial type, a domestic type, a stationary type, an on-vehicle type, a fixed type, a movable type, or a portable type.

[0020]

EXAMPLES (First Example) Examples of the present invention will be described below. FIG. 1 shows a conceptual diagram of a stationary fuel cell system.

First, the overall configuration will be described. As shown in FIG. 1, the fuel cell system according to the present embodiment includes a reforming unit 1 that generates a hydrogen-containing gas suitable for power generation by causing a reforming reaction between a fuel system gas (fuel) and steam to generate hydrogen. An evaporator 2 for evaporating raw material water to generate water vapor for generating a contained gas; a fuel system gas supply passage 4 (supply passage) for supplying a fuel system gas to the reforming section 1 via a heat exchange section 3; Reformer 1
The CO removal unit 5 that removes carbon monoxide contained in the hydrogen-containing gas generated in 1., the water source 6 (for example, a water tank) connected to a water pipe as a water supply source, the water source 6 and the evaporation unit 2
And a raw material water supply passage 7 for connecting the raw material water of the water source 6 to the evaporation section 2 by connecting the above. The CO removal unit 5 has a CO shift unit that reduces carbon monoxide by a shift reaction and a CO selective oxidation unit that reduces carbon monoxide by using air, but the CO removal unit 5 is not limited to these.

The fuel cell system according to this embodiment is shown in FIG.
As shown in FIG. 3, the fuel cell 8 that generates electricity with the air as the oxygen-containing gas (oxidizer) and the hydrogen-containing gas, and the hydrogen-containing gas generated in the reforming section 1 are supplied to the fuel cell 8 through the valve 9a. The hydrogen supply passage (supply passage) 9 is connected to the fuel off-gas passage 12 and the fuel off-gas passage 12 for flowing the off-gas of the fuel electrode discharged from the fuel cell 8 after power generation through the valve 10a, the condenser 10 and the valve 10c. The combustor 13 for combusting the off-gas of the fuel electrode of the fuel cell 8 is connected to the fuel system gas supply passage 4 and the combustor 13 via the branch 4m, and the fuel system gas is supplied to the combustor 13 for combustion. In the combustion section communication passage 14 and the fuel off-gas passage 12
3 and the fuel cell 8, a condenser 10 provided between the fuel cell 8 and an air supply passage (supply passage) for supplying power generation air (reaction gas) as an oxygen-containing gas to the air electrode of the fuel cell 8. ) 16, an air off-gas passage (off-gas passage) 18 through which the off-gas of the air after power generation discharged from the air electrode of the fuel cell 8 is discharged, and a heat exchanger 19 and a humidifying section provided in the air off-gas passage 18. 20 and.

In the combustion section communication passage 14, a pump 14p (fuel conveying means) for conveying the fuel system gas toward the combustion section 13
Is provided.

The fuel system gas supplied from the fuel system gas supply passage 4 is supplied to the combustion unit 13 through the combustion unit communication passage 14 and burned in the combustion unit 13, so that the temperature of the combustion unit 13 becomes high. Therefore, the temperature of the reforming section 1 can be maintained in the temperature range suitable for the fuel reforming reaction, and the hydrogen-containing gas is effectively generated in the reforming section 1.

The fuel system gas supply passage 4 is connected to a city gas gas pipe or gas cylinder and supplies a fuel system gas containing at least one of methane, propane, butane and the like as a main component. The fuel system gas supply passage 4 is provided with a double valve 29 including two valves 27 and 28 arranged in parallel, a pump 4p for transporting the fuel system gas, a desulfurization section 4a, a valve 4b, and a confluence section 4c. . The merging portion 4c is provided in the fuel system gas supply passage 4
The fuel system gas from the above is mixed with the water vapor evaporated in the evaporation unit 2, and the mixture is supplied to the reforming unit 1 via the heat exchange unit 3. The air supply passage 16 is provided with a filter 16a for cleaning the air, a fan 16b (air carrying means) for carrying air, and a humidifying section 20 for humidifying air. The humidifying unit 20 includes the fuel cell 8
The air (reaction gas), which is the oxygen-containing gas supplied to, is humidified. This is because if the electrolyte membrane of the fuel cell 8 is excessively dried, the power generation efficiency of the fuel cell 8 will decrease. In the raw material water supply passage 7, there are provided a filter 7a for purifying raw material water, a valve 7b, a valve 7c, a water purifier 7d for enhancing the degree of purification of raw material water, a water source 6, a pump 7f for conveying raw material water, and an opening / closing control valve 7h. It is provided.

As shown in FIG. 1, a cell cooling passage 2 which functions as a cooling means through which cooling water that removes heat from the fuel cell 8 flows.
2, a pump 22p and a heat exchange section 23 are provided. A hot water storage unit 26 is provided that takes away heat generated in the entire fuel cell system and stores it as hot water. In the heat exchange passage 31 extending from the discharge port 26i of the hot water storage unit 26, a cooling water transfer pump 31p (cooling water transfer means) and a condenser unit 1 are provided.
0 is provided, and a plurality of heat exchange parts (not shown) are provided at appropriate portions. Therefore, the cooling water flowing from the hot water storage portion 26 through the heat exchange passage 31 flows through the condenser portion 10 and further through a plurality of heat exchange portions (not shown) provided at appropriate portions, is heated by heat exchange, and is heated by the heat exchange portion 23. After that, it returns to the suction port 26o of the hot water storage unit 26. Therefore, the cooling water stored in the hot water storage unit 26 becomes hot and becomes hot water. The hot water that is the cooling water for the hot water storage unit 26 can be used as a hot water supply source for other purposes. Water is supplied to the hot water storage unit 26 from a water supply source through a supply passage 26k.

As can be understood from FIG. 1, the high-temperature off-gas of the fuel electrode after power generation, which is discharged from the fuel outlet 8e of the fuel cell 8, passes through the valve 10a and the condenser 10 and further to the valve 10.
c, flowing into the combustion section 13 through the fuel off-gas passage 12.
The off-gas of the fuel electrode after power generation has an unburned component that has not been consumed as a power generation reaction of the fuel cell 8, and thus is burned in the combustion unit 13.

As shown in FIG. 2, the fuel cell 8 is provided adjacent to the humidifying section 20. The air inlet 20a of the humidifying section 20 is connected to the air supply passage 16 and supplies air (reactant gas, oxygen-containing gas) that is an oxidant gas into the inside of the air electrode of the stack 81 of the fuel cell 8. The air outlet 20c of the humidifying part 20 is connected to the air off-gas passage 18 and discharges air (reactant gas, oxygen-containing gas) that is an oxidant gas to the outside of the stack 81 of the fuel cell 8.

The off-gas amount varying means 200 according to this embodiment.
Includes a bypass passage 202 that bypasses the humidifying section 20 so as not to pass through the humidifying section 20, and a relief valve 210. One end 202a of the bypass passage 202 communicates with the upstream portion of the humidifying portion 20 of the air off-gas passage 18, and the other end 202c of the bypass passage 202 communicates with the downstream portion of the humidifying portion 20 of the air off-gas passage 18. The other end 202c of the bypass passage 202 communicates with the upstream side of the heat exchanger 19 in the air off-gas passage 18.

The relief valve 210 functions as a gas passage amount changing means, and also serves to change the gas amount of the air directed to the humidifying section 20 of the air off-gas passage 18, and the relief valve 210 can be opened in plural amounts. It can be adjusted in steps or in steps. As shown in FIG. 2, the humidifying section 20 includes a case 20m, a humidifying member 20n formed of an ion exchange membrane having both moisture retention and gas barrier properties, which is held in the case 20m, and air directed toward the fuel cell 8. The first passage 20f communicating with the passing air supply passage 16
And the second passage 20s communicating with the air off-gas passage 18 through which the off-gas after power generation discharged from the fuel cell 8 passes.
With and.

As can be understood from FIG. 2, the off-gas of the air after power generation discharged from the air electrode of the fuel cell 8 passes through the humidifying section 20 and the heat exchanger 19. The off-gas of the air after power generation, which is discharged from the air electrode of the fuel cell 8, has heat and moisture, and the second passage 20 s of the humidifying section 20.
Since the humidifying member 20n comes into contact with the humidifying member 20n as it passes through, the humidifying member 20n is provided with heat and moisture.
n is heated and humidified.

On the other hand, the air before power generation, which is directed to the air electrode of the fuel cell 8 through the air supply passage 16, is the first air of the humidifying section 20.
When passing through the passage 20f, the humidifying member 20n is contacted to receive heat and moisture from the humidifying member 20n. As a result, the air before power generation supplied to the fuel cell 8 is heated and humidified, which is advantageous for maintaining the internal temperature and humidified state of the fuel cell 8.

Now, the description of the vicinity of the fuel cell 8 will be added. The fuel cell 8 is a polymer electrolyte type (PEFC),
As shown in FIG. 3, it has a stack 81 in which a plurality of battery cells 80 are stacked in the thickness direction, and a base portion 83 that holds the stack 81. The base portion 83 functions as a flow passage forming portion 84 having an air flow passage and a fuel system gas flow passage that communicate with the flow passage of the stack 81, and a facing portion that faces the flow passage forming portion 84 via the stack accommodation space 84x. A pressure plate 85, a plurality of rods 86 arranged in parallel so as to function as a connecting portion that connects the base portion 83 and the pressure plate 85, and a nut 87 that functions as a fastening member that fastens the rod 86 and the pressure plate 85. Have. The base portion 83 has a structure in which the fuel cell 8 is held and the base portion 83 is allowed to flex and deform. Therefore, even when the excessive load acts on the fuel cell 8 in the stacking direction, the excessive load does not act on the fuel cell 8.
This is suppressed by the bending deformation of No. 3. A spring for reducing excessive load may be interposed between the nut 87 and the pressure plate 85. The pressure plate 85 itself may be allowed to bend in order to reduce an excessive load.

As shown in FIG. 4, the battery cell 80 is a ME
Groove-shaped channel 80 while sandwiching A80x and MEA80x
separator 80y with z. MEA80x
Has an electrolyte membrane 80a formed of a proton conductive polymer membrane and functioning as an electrolyte phase, and a positive electrode 80b and a negative electrode 80h sandwiching the electrolyte membrane 80a. The positive electrode 80b is also called an oxidizer electrode, an oxygen electrode, or an air electrode, and includes a gas permeable layer 80c formed of a material having air permeability and current collecting property such as a fiber aggregate, and a catalyst substance for obtaining a positive electrode active material. It is formed with the carried catalyst layer 80d. The negative electrode 80h is also called a fuel electrode, and is composed of a gas permeable layer 80i formed of a material having air permeability and current collecting property such as a fiber assembly, and a catalyst layer 80k supporting a catalyst substance for obtaining a negative electrode active material. Has been formed. Hydrogen functions as an active material at the fuel electrode (negative electrode 80h) of the fuel cell 8. Oxygen is the oxygen electrode of the fuel cell 8 (positive electrode 8
It functions as an active material in 0b).

As shown in FIG. 3, the base portion 83 has a fuel inlet 83m to which a hydrogen-containing gas as a fuel system gas is supplied and a fuel outlet 8e for discharging the fuel system gas to the outside of the stack 81.
A cooling water inlet 83p which is in communication with the battery cooling passage 22 as a cooling means and is supplied with cooling water supplied to the inside of the stack 81 to cool the stack 81;
1 has a cooling water outlet 83r for discharging the cooling water that has passed through the inside of the stack 1 and cooled the stack 81 to the outside of the stack 81, and a bypass passage 202 for discharging the off gas of the air after power generation.

As shown in FIG. 3, there is provided a load cell 100 which functions as a fuel cell humidified state detecting means for detecting the moisture content of the electrolyte membrane 80a of the fuel cell 8. Load cell 10
The detection principle of 0 is not particularly limited, and may be a load cell type, a strain gauge type, a piezoelectric type, a magnetostrictive type, or the like as long as the load change in the stacking direction of the fuel cell 8 can be detected. When the fuel cell 8 gets wet, the dimension increases in the stacking direction and the load increases,
The dimension in the stacking direction does not increase so much, but the load may increase. If it is a load cell, both can be dealt with.

The detecting portion 100m of the load cell 100 functions as a facing portion facing the fuel cell 8 so as to receive the load in the stacking direction of the fuel cell 8.
And the end portion 81s of the fuel cell 8 in the stacking direction. Especially, the detection part 100m is used for the pressure plate 8
5 and the center area of the end portion 81s of the fuel cell 8 in the stacking direction. The load meter 100 detects a load change in the stacking direction of the fuel cells 8 and has a detection unit 100m for detecting the detection signal via the signal line 39m to the control unit 39.

When the moisture content in the flow path of the stack 81 of the fuel cell 8 becomes excessive, the electrolyte membrane 80a swells in the stacking direction as it wets, so that the load detected by the load meter 100 increases. On the other hand, when the moisture content in the flow path of the stack 81 of the fuel cell 8 is insufficient, the stack 8 of the fuel cell 8
Since No. 1 contracts in the stacking direction, the load cell 10
The load detected at 0 decreases. In this way, the load cell 100
The electrolyte membrane 80 of the fuel cell 8 is determined by the load value measured at
The moisture state of a can be detected. Generally, the load value is kgf, tonf, although it depends on the size of the fuel cell 8.
Is a unit of.

According to the present embodiment, the humidification control means humidifies the fuel cell 8 when the measured load value, which is detected by the load cell 100 and is related to the dimensional change of the fuel cell 8 in the stacking direction, is within the predetermined value. Determine that it is necessary to do. At this time, the humidification control means closes the escape valve 210. As a result, the off gas (including moisture) of the air after power generation, which is discharged from the air electrode of the fuel cell 8, flows into the second passage 20s of the humidifying section 20, but does not flow into the bypass passage 202. In this case, off-gas (including moisture) of the air after power generation
Since the amount of flowing into the second passage 20s of the humidifying section 20 is secured, the humidifying member 20n is humidified. Therefore, the fuel cell 8
The air before power generation toward is satisfactorily humidified by the humidifying member 20n, and excessive drying of the inside of the fuel cell 8 is suppressed.

On the other hand, when the measured value of the load value detected by the load meter 100 is increasing, the humidification control means determines that the inside of the fuel cell 8 is slightly humidified. At this time, the humidification control means increases the opening amount of the relief valve 210. As a result, part of the off gas (including moisture) of the air after power generation, which is discharged from the fuel cell 8, is caused to flow into the bypass passage 202. In this case, the off-gas (including moisture) of the air after power generation, which is discharged from the air electrode of the fuel cell 8, also flows into the second passage 20s of the humidifying unit 20, although it flows into the second passage 20s of the humidifying unit 20. Therefore, the amount of moisture in the humidifying member 20n is slightly reduced.
Therefore, the amount of humidification of the air before power generation in the first passage 20f toward the fuel cell 8 is reduced, and excessive humidification inside the fuel cell 8 is suppressed.

Further, when the measured value of the load value detected by the load meter 100 is further increasing, the humidification control means determines that the inside of the fuel cell 8 is considerably humidified. At this time, the humidification control means further increases the opening amount of the relief valve 210. As a result, a considerable amount of off-gas (including moisture) of the air after power generation, which is discharged from the air electrode of the fuel cell 8, is caused to flow into the bypass passage 202. In this case, the off gas (including moisture) of the air after power generation, which is discharged from the air electrode of the fuel cell 8, receives the second passage 2 of the humidifying section 20.
Although flowing for 0 s, the amount flowing through the second passage 20 s of the humidifying section 20 is further reduced, and the amount of moisture of the humidifying member 20 n is further reduced. Therefore, the humidification amount of the air before power generation in the first passage 20f toward the air electrode of the fuel cell 8 is further reduced, and excessive humidification inside the fuel cell 8 is suppressed.

Furthermore, when the measured value of the load value detected by the load meter 100 is further increasing, the humidification control means determines that the inside of the fuel cell 8 is in the excessive humidification state. At this time, the humidification control means sets the opening degree of the relief valve 210 to 100%. As a result, a considerable amount of off-gas (including moisture) of the air after power generation discharged from the fuel cell is caused to flow into the bypass passage 202. In this case, the amount of off-gas (including moisture) of the air after power generation flowing through the second passage 20s of the humidifying section 20 is reduced, so that the amount of moisture of the humidifying member 20n is further reduced. Therefore, the humidification amount of the air in the first passage 20f before power generation toward the air electrode of the fuel cell 8 is further reduced, and excessive humidification inside the fuel cell 8 is suppressed. The humidification control means is configured as software in the control unit 39.

(Control) As shown in FIG.
Is an input processing circuit 39a to which the detection signals (S1, S2) from the load cell 100 are input, and a control circuit 3 including a CPU.
9b, an output processing circuit 39c for outputting a control signal to the relief valve 210, and a memory 39e. The target value of the load value of the load meter 100 regarding the opening amount of the relief valve 210 is stored in the memory 39e (storage means). The control of the present embodiment is performed so that the moisture content inside the stack 81 of the fuel cell 8 is within the proper range and the moisture content of the electrolyte membrane 80a is within the proper range.

FIG. 6 shows an example of a flow chart regarding the bypass process in the operation of the fuel cell 8. First, the target values α1 and α2 of the load values of the load meter 100 are read from the memory 39e (step S102, load value target value reading means, physical quantity target value reading means). Further, the measured value α of the load value measured by the load meter 10 is read (step S104, load value measured value reading means, physical quantity measured value reading means). Then, the measured value α of the load value measured by the load value is compared with the target value α1 of the load value stored in advance in the memory 39e (step S106, comparison means). When the humidified state inside the fuel cell 8 is too dry, that is, when it is determined that "humidification is necessary", the relief valve 210 is closed (step S108). As a result, all of the off-gas after power generation discharged from the air electrode of the fuel cell 8 flows into the second passage 20s of the humidifying section 20. In this case, the off gas after power generation does not flow into the bypass passage 202.

Furthermore, when it is not determined in step S106 that the fuel cell 8 is too dry, the measured load value α is compared with the target load value α2 stored in the memory 39e in advance (step S120, comparison). means).
Although the inside of the fuel cell 8 needs to be humidified, the amount of opening of the relief valve 210 is increased (step S12) when it is judged to be slightly humidified.
2) While flowing the off gas after power generation discharged from the air electrode of the fuel cell 8 into the second passage 20s of the humidifying section 20, a part of the off gas is caused to flow into the bypass passage 202.

Further, when it is determined that the inside of the fuel cell 8 is excessively humidified, the opening amount of the relief valve 210 is further increased (step S132), and the off gas after power generation discharged from the air electrode of the fuel cell 8 is humidified. Second passage 2 of section 20
Stop flowing for 0 s, and remove all of the off-gas from the humidifying section 2.
0 is bypassed and the heat exchange part 19 is passed through the bypass passage 202.
Shed on. In this way, since the off-gas having the moisture content after power generation bypasses the humidifying section 20, the humidifying member 20n of the humidifying section 20
The moisture content of the fuel cell 8 is further reduced, and excessive humidification inside the fuel cell 8 is prevented. Note that steps S102 to S13
Reference numeral 2 constitutes a humidification control means.

By the way, FIG. 7 schematically shows the relationship between the output of the fuel cell 8 and the humidified state. The horizontal axis of FIG. 7 represents the humidification amount inside the fuel cell 8, and the vertical axis represents the output state of the fuel cell 8. As indicated by the characteristic line A in FIG. 7, as the humidification state inside the fuel cell 8 progresses, the output voltage of the fuel cell 8 gradually increases, and there exists an optimum humidification area AM in which the fuel cell 8 exhibits an output peak. . However, the present inventor has found that the output of the fuel cell 8 tends to drastically decrease beyond the optimum humidification area AM of the fuel cell 8 even if the humidification amount slightly increases. Therefore, the present inventor sets the target values α1 and α2 so that the fuel cell 8 is operated in a state where the inside of the fuel cell 8 is slightly ΔA dry rather than the optimum humidification area AM where the fuel cell 8 shows an output peak. It is set. Therefore, it is possible to suppress a sharp decrease in the output of the fuel cell 8 during the operation of the fuel cell 8, which is advantageous for stable operation.

Further, as the cumulative operating time of the fuel cell 8 becomes longer, the material inside the fuel cell 8 becomes sagged. Therefore, if the cumulative operating time of the fuel cell 8 becomes excessively long, the size and load of the fuel cell 8 are unlikely to increase even if the fuel cell 8 swells. Therefore, according to the present embodiment, as shown in FIG. 8, the cumulative operating time of the fuel cell 8 is measured (step S
202, means for measuring cumulative operating time). When the cumulative operating time of the fuel cell 8 exceeds the predetermined update time, the target value α
1 and α2 are multiplied by the deterioration correction coefficient to obtain the target value α
1 and α2 are reduced and updated as new target values (steps S204, 206, target value updating means).

(Second Embodiment) FIG. 9 shows a second embodiment.
The second embodiment has basically the same configuration as the above-mentioned first embodiment, and basically has the same operational effect. The difference will be mainly described below. The second embodiment is shown in FIG.
3 to 5 can be applied correspondingly. The parts having the same function are designated by the same reference numerals. According to the second embodiment shown in FIG. 9, in addition to the bypass passage 202 and the relief valve 210 being provided, the air supply passage 16 for supplying air before power generation to the air electrode of the fuel cell 8 includes: The second bypass passage 2 that bypasses the humidifying section 20 so as not to pass through the humidifying section 20.
25 are provided.

One end 225a of the second bypass passage 225 communicates with the downstream of the humidifying section 20 of the air supply passage 16, and the other end 225c of the second bypass passage 225 of the humidifying section 20 of the air supply passage 16. It communicates with the upstream. The second bypass valve 225 includes a second relief valve 23.
0 is provided. The second relief valve 230 has a second
The gas amount of the air before power generation flowing in the bypass passage 225 is made variable, and it functions as a gas passage amount changing means. The opening amount of the second relief valve 230 can be adjusted in multiple steps or infinitely.

When the measured load value in the stacking direction of the fuel cell 8 detected by the load meter 100 is within a predetermined value, the humidification control means determines that the fuel cell 8 needs to be humidified. At this time, the humidification control means releases the relief valve 21.
Both 0 and the second relief valve 230 are closed. As a result, the off-gas (including moisture) of the air after power generation discharged from the air electrode of the fuel cell 8 is supplied to the second passage 2 of the humidifying section 20.
Although it flows for 0 s, it does not flow for the bypass passage 202.
Further, the air before power generation, which goes toward the fuel cell 8 along the air supply passage 16, is not allowed to flow into the second bypass passage 225.

On the other hand, when the measured value of the load value detected by the load meter 100 is increasing, the humidification control means determines that the inside of the fuel cell 8 is slightly humidified. At this time, the humidification control means increases the opening amount of the relief valve 210. As a result, part of the off gas (including moisture) of the air after power generation, which is discharged from the fuel cell 8, is caused to flow into the bypass passage 202. In this case, the second relief valve 230 may be closed or may be slightly opened.

Further, when the measured value of the load value detected by the load meter 100 is further increasing, the humidification control means determines that the inside of the fuel cell 8 is in the excessive humidification state. At this time, the humidification control unit increases the opening degree of the relief valve 210 and increases the opening amount of the second relief valve 230. As a result, a considerable amount of the off-gas (including moisture) of the air after power generation, which is discharged from the air electrode of the fuel cell 8, is caused to flow into the bypass passage 202, and the humidifying member 20.
The moisture content of n is further reduced. Further, the air supply passage 16
In the air before power generation toward the fuel cell 8 in the
0 bypassing the first passage 20f to bypass the second bypass passage 225
Also flows. In this way, the amount of air supplied to the air electrode of the fuel cell 8 by bypassing the first passage 20f of the humidifying section 20 increases, so that excessive humidification inside the fuel cell 8 is effectively suppressed. Therefore, the responsiveness in preventing excessive humidification of the fuel cell 8 is improved.

(Third Embodiment) FIG. 10 shows a third embodiment. The third embodiment has basically the same configuration as the above-mentioned embodiments, and the different points will be mainly described below. In the third embodiment, as shown in FIG. 10, one end 202a of the bypass passage 202 communicates with the bottom of the manifold 8m on the air electrode side of the fuel cell 8. Bypass passage 202
The other end 202c of the air passage is connected to the downstream side of the humidifier 20 in the air off-gas passage 18 so as to bypass the humidifier 20. Therefore, when the relief valve 210 is opened, the bypass passage 202 can also serve as a drain function for discharging the water accumulated at the bottom of the manifold 8m of the fuel cell 8 to the outside of the manifold 8m. Relief valve 210
When the fuel cell 8 is closed, the off-gas discharged from the fuel cell 8 after power generation does not flow through the bypass passage 202 but is discharged through the air off-gas passage 18, the second passage 20s of the humidifying section 20, and the heat exchanger 19. .

(Other Embodiments) Other embodiments described below are as follows.
The configuration is the same as that of the above-described embodiment, and the same operational effect is obtained. The difference will be mainly described below. The parts having the same function are designated by the same reference numerals. According to the embodiment shown in FIG. 11, the load cell 10 is used as the fuel cell humidified state detecting means for detecting the moisture content of the electrolyte membrane 80a of the fuel cell 8.
0 is provided. The load cell 100 is interposed between the pressure plate 85 and the stack 81 together with the spring member 100w. The spring member 100w can function as an excessive load reducing means for reducing an excessive load in the stacking direction of the fuel cells 8. The spring member 100w can be formed of at least one of an elastically deformable member, for example, a spring such as a disc spring, a leaf spring, and a coil spring, a rubber body, a foam body, or the like. When the size increase of the fuel cell 8 in the stacking direction is excessive, the spring member 100w reduces the excessive load acting on the inside of the fuel cell 8.

According to the embodiment shown in FIG. 12, as the fuel cell humidified state detecting means, a detecting portion 102 for detecting a dimensional change or a load change in the stacking direction of the fuel cell 8 by stress strain.
The stress state detecting means 102 having m is used. A spacer member 85a is interposed between the pressure plate 85 and the fuel cell 8. The detection unit 102m is a strain gauge and is provided on the surface of the rod 86. When the fuel cell 8 gets wet and swells in the stacking direction as the moisture content increases, the tensile force acting on the rod 86 increases. The detection unit 102m, which is a strain gauge, detects this. This signal is input to the control unit 39 via the signal line 39m. This makes it possible to detect the humidified state or the dry state inside the fuel cell 8. Stress state detecting means 1 having a detecting portion 102m on at least one of the plurality of rods 86
02 can be used.

In the embodiment shown in FIG. 13, the length detecting means 103 having a detecting portion 103m for detecting a dimensional change in the stacking direction of the stack 81 of the fuel cell 8 is used as the fuel cell humidified state detecting means. The detection unit 103m is formed by a distance change sensor such as a linear potentiometer. The detection signal of the detection unit 103m is input to the control unit 39 via the signal line 39m. This makes it possible to detect the humidified state or the dry state inside the fuel cell 8. If necessary, a change magnifying mechanism for magnifying the dimensional change of the stack 81 in the stacking direction can be provided.

In the embodiment shown in FIG. 14, length detecting means 104 which functions as fuel cell humidified state detecting means is provided. Detection unit 104m of the length detection means 104
Is a light emitting portion 104a for emitting inspection light (laser beam or the like) toward the end portion 81s of the stack 81 along a direction intersecting the stacking direction of the fuel cell 8, and a light receiving portion for receiving light from the light emitting portion 104a. 104c. The dimensional change in the stacking direction of the fuel cell 8 is detected as the amount of light received by the light receiving unit 104c. As a result, the humidified state or the dry state inside the fuel cell 8 can be detected without contacting the fuel cell 8.

In the embodiment shown in FIG. 15, the capacitance detecting means 105 having the electrode plates 105a and 105b as the detecting portions for detecting the capacitance change is used as the fuel cell humidification state detecting means. When the length of the fuel cell 8 in the stacking direction changes due to the increase in moisture, the electrode plate 105
Since the electrostatic capacitance between a and 105b changes, the signal is input to the control unit 39 via the signal line 39m. As a result, it is possible to detect a dimensional change in the stacking direction of the fuel cell 8 due to an increase in moisture content, and thus to detect a humidified state or a dry state inside the fuel cell 8.

In the embodiment shown in FIG. 16, the fuel cell humidifying state detecting means is a magnet section 106a as a detecting section for detecting a magnetic change, and a detecting section 106b for detecting magnetism.
The magnetic detection means 106 having When the length of the fuel cell 8 in the stacking direction changes due to the increase in humidity, the magnetism detected by the detection unit 106b changes, and the signal is input to the control unit 39 via the signal line 39m. As a result, it is possible to detect a dimensional change in the stacking direction of the fuel cell 8 due to an increase in moisture content, and thus to detect a humidified state or a dry state inside the fuel cell 8.

(Others) In the above embodiment, the escape valve 210 is provided in the bypass passage 202 so that the off gas from the fuel cell 8 bypasses the humidifying section 20, but the off gas from the fuel cell 8 is humidified by the humidifying section. The relief valve 210 may be provided anywhere as long as the bypass 20 is bypassed, for example, may be provided at a connection portion between the bypass passage 202 and the air off-gas passage 18. In the embodiment described above, the relief valve 2 is provided in the bypass passage 202.
Although 10 is provided, instead of this, a pump for air transportation may be provided, and the amount of air flowing into the bypass passage 202 may be variable depending on the rotation speed of the pump. In the above-described embodiment, the humidifying unit 20 that humidifies the air, which is the reaction gas supplied to the air electrode of the fuel cell 8, is applied, but depending on the case, although not shown, it is supplied to the fuel electrode of the fuel cell 8. It may be applied to a humidifying section for humidifying the fuel gas, which is the reaction gas. Although the above-described embodiment is applied to the stationary fuel cell system, the present invention is not limited to this, and may be applied to a fuel cell system mounted on a vehicle. The above embodiment is applied to a fuel cell system having a polymer electrolyte membrane, but the invention is not limited to this. Fuel-based gas (such as city gas) is used as the fuel, but the fuel is not limited to this. Although air is used as the oxidant gas, an oxygen-enriched gas may be used. Besides, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within the scope not departing from the gist.

The following technical idea can be understood from the above description. (Additional Item 1) In each claim, the fuel cell power generation system is provided with an excessive load reducing means for reducing an excessive load in the stacking direction of the fuel cells. (Supplementary Note 2) In each claim, the humidification control means operates the fuel cell in a region where the inside of the fuel cell is dry rather than the optimum humidification region where the fuel cell shows the highest output. system. In this case, the target value of the load value or the dimensional target value in the stacking direction of the fuel cell is set so that the inside of the fuel cell becomes a dry region rather than the optimum humidification region where the fuel cell shows the highest output. (Additional Item 3) In the additional item 2, there is provided a passage for supplying the reaction gas before power generation to the fuel cell through the humidifying portion, and a bypass passage for supplying the reaction gas before power generation to the fuel cell without passing through the humidifying portion. A fuel cell power generation system characterized by:
The reaction gas before power generation can be supplied to the fuel cell without passing through the humidifying section. For this reason, it is advantageous to keep the temperature slightly dry compared to the optimum humidification region where the output peak of the fuel cell is shown.

[0063]

According to the fuel cell power generation system of the present invention, the fuel cell humidified state detecting means detects the humidified state inside the fuel cell based on the dimensional change or load change of the fuel cells in the stacking direction. Depending on the humidification state of the fuel cell detected by the fuel cell humidification state detection means, the humidification control means,
The amount of off-gas of the reaction gas after power generation from the fuel cell to the humidifying part is variable. As a result, the moisture content in the humidifying member of the humidifying section is variable. As a result, the humidification state of the reaction gas supplied to the fuel cell before power generation is variably controlled,
Overdrying and excessive humidification inside the fuel cell are avoided or suppressed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a fuel cell system.

FIG. 2 is a piping diagram showing piping near a humidifying section.

FIG. 3 is a plan view showing the vicinity of a fuel cell.

FIG. 4 is an exploded perspective view of a battery cell.

FIG. 5 is a block diagram related to a control unit.

FIG. 6 is a flow chart relating to humidification control using a humidification unit of a fuel cell.

FIG. 7 is a graph showing the relationship between the humidified state of the fuel cell and the output of the fuel cell.

FIG. 8 is a flowchart for updating a target value.

FIG. 9 is a piping diagram showing piping in the vicinity of a humidifying unit according to another embodiment.

FIG. 10 is a piping diagram showing piping in the vicinity of a humidifying unit according to another embodiment.

FIG. 11 is a plan view showing the vicinity of a fuel cell provided with a fuel cell humidified state detecting means according to another embodiment.

FIG. 12 is a plan view showing the vicinity of a fuel cell provided with a fuel cell humidified state detecting means according to another embodiment.

FIG. 13 is a plan view showing the vicinity of a fuel cell provided with a fuel cell humidification state detecting means according to another embodiment.

FIG. 14 is a plan view showing the vicinity of a fuel cell equipped with a fuel cell humidified state detecting means according to another embodiment.

FIG. 15 is a plan view showing the vicinity of a fuel cell including a fuel cell humidification state detecting means according to another embodiment.

FIG. 16 is a plan view showing the vicinity of a fuel cell equipped with a fuel cell humidification state detecting means according to another embodiment.

[Explanation of symbols]

In the figure, 8 is a fuel cell, 39 is a control unit, 100 is a load meter (fuel cell humidification state detecting means), 200 is an off gas amount varying means, 202 is a bypass passage, 210 is a relief valve (gas passage amount changing means). Show.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Kunieda             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Shogo Goto             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F-term (reference) 5H026 AA06 HH05 HH09 HH10                 5H027 AA06 BA01 BA09 DD06 KK31                       MM08

Claims (5)

[Claims] 1. A fuel cell for generating power with a reaction gas, a supply passage for supplying the reaction gas to the fuel cell, an offgas passage for discharging offgas of the reaction gas after power generation from the fuel cell, the supply passage and the The humidifying member is connected to the off-gas passage and has a hygroscopic property, and the humidifying member absorbs moisture in the off-gas of the reaction gas discharged from the fuel cell after power generation, and the reaction before power generation toward the fuel cell. In a fuel cell power generation system having a humidifying section for humidifying gas with the humidifying member, while detecting a dimensional change in the stacking direction or a load change in the stacking direction due to wetting of the fuel cell, the dimensional change or the load change A fuel cell humidified state detecting means for detecting a humidified state inside the fuel cell based on the fuel cell; and the fuel detected by the fuel cell humidified state detecting means. By varying the amount of off-gas of the reaction gas after power generation from the fuel cell toward the humidifying section according to the humidification state of the cell, the humidity in the humidifying member of the humidifying section is made variable, and the fuel cell And a humidification control means for controlling the humidification state of the reaction gas before power generation supplied to the fuel cell power generation system. 2. The fuel cell humidified state detecting means according to claim 1, wherein the fuel cell humidified state detecting means is arranged so as to detect a load change in the stacking direction of the fuel cell between the base portion holding the fuel cell and the fuel cell. A fuel cell power generation system, which is a load cell. 3. The humidified state detecting means for fuel cell according to claim 1, wherein the humidified state detecting means detects a stress state in at least a part of a base portion holding the fuel cell, and the humidified state inside the fuel cell is detected based on the stress state. Is a fuel cell power generation system. 4. The humidification control means according to claim 1, wherein the humidification control means detects that the humidification state inside the fuel cell is excessive by the fuel cell humidification state detection means. Reducing the amount of off-gas of the reaction gas after power generation from the fuel cell toward the humidifying section to reduce the moisture content of the humidifying member of the humidifying section, and by the fuel cell humidifying state detecting means, When it is detected that the humidification inside the fuel cell is insufficient or necessary, by increasing the amount of off-gas of the reaction gas after power generation from the fuel cell toward the humidification unit, the humidification member of the humidification unit is increased. A fuel cell power generation system characterized by increasing moisture content. 5. The humidification control means according to claim 1, wherein the humidification control means controls a dimension value or a load value of the fuel cell in a stacking direction to be a target value.
A fuel cell power generation system, wherein a target value of a dimension value or a load value is reduced when the cumulative operating time of the fuel cell becomes long.