JP2005209362A - Fuel cell power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately cope with various problems related to DSS operation of a fuel cell, such as accelerated drying of an electrolyte membrane, local combustion, and electrode water repellency deterioration by exposing the inside of a fuel cell to an atmosphere of a humidified raw material gas at an appropriate timing And a fuel cell power generator capable of stabilizing the performance of the fuel cell.
A fuel cell power generation device includes a fuel cell having a fuel gas flow path and a raw material gas supply means for supplying a raw material gas. During the power generation period of the fuel cell, the fuel gas flow The fuel cell 21 is caused to generate electric power by supplying a fuel gas generated from the raw material gas to the road, and the raw material gas is used during the transition period of the fuel cell between the stop period of the fuel cell 21 and the electric power generation period. The source gas sent from the supply means 22 is humidified, and the inside of the fuel cell 21 is exposed to the atmosphere of the humidified source gas.
[Selection] Figure 3

Description

  The present invention relates to a fuel cell power generator, and more particularly to a fuel cell power generator that allows the inside of a fuel cell to be exposed to an atmosphere of a humidified raw material gas during a transition period from a stop period of the fuel cell to a power generation period.

  In a fuel cell power generator for home use, it is desired that power generation and stoppage of the fuel cell be repeated frequently in accordance with the amount of power consumption in daily life from the viewpoint of reducing utility costs.

  Specifically, the so-called DSS (Daily Start-up & Shut-down) operation, which operates the power generator during the daytime when power consumption increases and stops the power generator during the night when power consumption decreases, is a utility cost. It is excellent in terms of effective use. Under such circumstances, technical problems and countermeasures relating to repetitive operations of power generation and stop of the fuel cell have been reported so as to flexibly cope with DSS operation. For example, in order to prevent the electrolyte membrane from being dried during storage of the polymer electrolyte membrane (ion exchange membrane) and to restart the fuel cell quickly from the storage, the fuel gas remaining in the fuel cell immediately after the fuel cell is stopped And a method of sealing the gas flow path of the fuel cell after replacing the oxidant gas with water or a humidified inert gas (see Patent Document 1).

Certainly, it is considered that there is a possibility that it is possible to cope with the drying of the electrolyte membrane of the fuel cell by exposing the inside of the fuel cell to a humidified inert gas atmosphere while the fuel cell is stopped and stored as in Patent Document 1.
JP-A-6-251788

  By the way, according to the above-described conventional method for stopping and storing the fuel cell, although it is disclosed that the inside of the fuel cell is replaced with humidified inert gas for the purpose of preventing the drying of the electrolyte membrane from being accelerated, The method has the following items to be improved.

  First, even if the fuel cell is sealed off from the external atmosphere, when the fuel cell is stored for a certain period (for example, about 15 hours to 3 days), air (oxygen gas) is fueled from the sealed portion. There is a possibility of leaking inside the battery and mixing. In particular, in the case of the humidified inert gas introduction method described in Japanese Patent Application Laid-Open No. 6-251788 (introduction immediately after stoppage), the water vapor contained in the humidified inert gas is condensed due to a decrease in the temperature inside the fuel cell. This promotes the concern about oxygen gas contamination. Under such circumstances, if hydrogen-rich fuel gas is supplied when the fuel cell is restarted, local combustion by oxygen gas and fuel gas occurs at the anode of the fuel cell, causing damage to the fuel cell or deterioration of the performance of the fuel cell. Can lead to.

  Second, in the above-described conventional method for stopping and storing a fuel cell, a method for grasping the dry state of the electrolyte membrane of the fuel cell is not disclosed, and power generation of the fuel cell is started without judging the quality of the electrolyte membrane. Therefore, there is a concern that local fuel in the fuel cell cannot be properly prevented.

  Third, when the power generation and stoppage of the fuel cell are frequently repeated over a long period (for example, about 2 to 3 years), the fuel cell electrode is continuously immersed in water during the stoppage period. Since the water repellency of the electrode is eroded due to a typical water atmosphere, the drainage capacity during operation of the fuel cell is impaired, and the performance of the fuel cell may be deteriorated. Therefore, it is necessary to avoid exposing the inside of the fuel cell to a humidified gas atmosphere for a long time as in the conventional stopped storage method.

  Fourthly, as described in the above publication, when an additional facility for an inert gas supply device is provided separately, the fuel cell power generator is increased in size and cost.

  The present invention has been made in view of the above circumstances, and its purpose is to appropriately cope with various problems related to DSS operation of a fuel cell, such as acceleration of drying of an electrolyte membrane, local combustion, and electrode water repellency deterioration. An object of the present invention is to provide a fuel cell power generator capable of stabilizing the performance of a fuel cell.

  A fuel cell power generation device according to the present invention includes a fuel cell having a fuel gas flow path, and a raw material gas supply means for supplying a raw material gas. During the power generation period of the fuel cell, In the transition period of the fuel cell between the stop period and the power generation period in the fuel cell in which the fuel cell is generated by supplying the fuel gas generated from the source gas and the stop and the power generation are alternately repeated, The source gas sent from the source gas supply means is humidified, and the inside of the fuel cell is exposed to the atmosphere of the humidified source gas. More specifically, the electrolyte membrane inside the fuel cell can be exposed to the atmosphere of the source gas by circulating the source gas through the fuel gas flow path.

  As a result, the inside of the fuel cell can be exposed to the atmosphere of the humidified raw material gas at an appropriate timing, which is suitable for various problems related to the DSS operation of the fuel cell, such as accelerated drying of the electrolyte membrane, local combustion, and electrode water repellency deterioration. Yes. More specifically, the inside of the fuel cell can be exposed to the humidified raw material gas during the transition period from the stop period of the fuel cell to the power generation period, and the electrolyte membrane of the fuel cell dried during the stop storage can be humidified. Even when oxygen gas is mixed into the fuel cell during stop storage, local combustion with the fuel gas caused by the oxygen gas can be prevented in advance. In addition, since the humidified source gas is introduced into the fuel cell during the transition period from the stop period of the fuel cell to the power generation period, the inside of the fuel cell is not exposed to the humidified source gas atmosphere for a long period of time. The water repellency of the fuel cell electrode is not impaired.

  Here, in order to sufficiently retain the electrolyte membrane of the fuel cell, it is desirable to humidify the source gas so that the dew point of the source gas can be maintained at or above the operating temperature of the fuel cell.

  Further, when the raw material gas contains a sulfur component, it is adsorbed on the surface of the platinum catalyst of the fuel cell and adversely affects the reaction surface. Therefore, the raw gas in the raw material gas is provided by the gas cleaning unit provided in the raw material gas supply means. After removing the sulfur component, it is desirable to expose the inside of the fuel cell to the atmosphere of the raw material gas.

  Similarly, it is preferable to select any one of methane gas, propane gas, butane gas, and ethane gas as the raw material gas so as not to inhibit the activity of the platinum catalyst of the fuel cell.

  In addition, the fuel cell power generator according to the present invention includes a fuel generator that generates a fuel gas to be supplied to the fuel cell from the raw material gas supplied from the raw material gas supply unit and water vapor, and the raw material gas supply unit When the raw material gas sent out from is humidified inside the fuel generator, the fuel generator is controlled to maintain a temperature lower than a lower limit temperature at which the raw material gas is carbonized in the fuel generator. Is. More preferably, the temperature of the fuel generator is maintained at 300 ° C. or lower so that carbon monoxide gas having a catalytic poisoning effect of MEA is not generated from the raw material gas and water vapor in the fuel generator (reforming section). To be controlled.

  Here, in one embodiment, an anode and a cathode sandwiching an electrolyte membrane are arranged inside the fuel cell, and after exposing the anode to the source gas atmosphere, the cathode is exposed to the source gas atmosphere. May be processed. According to such a supply method of the humidified raw material gas, if oxygen gas is mixed into the anode while the fuel cell is stopped and stored, the humidified raw material gas introduction route that leads to the cathode after passing through the anode can be adopted, and the oxidation deterioration occurs. It is possible to preferentially exclude the anode oxygen gas that is easily generated.

  In this case, a fuel generator that generates fuel gas to be supplied to the fuel cell from the raw material gas supplied from the raw material gas supply means and water vapor is provided, and the raw material gas is humidified inside the fuel generator. Is possible.

  In another embodiment, an anode and a cathode sandwiching an electrolyte membrane are disposed inside the fuel cell, and after exposing the cathode to the atmosphere of the source gas, the anode is exposed to the atmosphere of the source gas. May be processed.

  In this case, a humidifier for humidifying an oxidant gas for power generation reaction with the fuel gas supplied to the cathode is provided, and the source gas can be humidified by the humidifier.

  Furthermore, in another embodiment, an anode and a cathode sandwiching an electrolyte membrane are disposed inside the fuel cell, the cathode is exposed to the atmosphere of the first source gas that is diverted from the source gas, and the anode is You may process so that it may be exposed to the atmosphere of said 2nd source gas shunted from said source gas. According to such a supply method of the humidified source gas, the first source gas and the second source gas are separately mixed without being mixed with each other, the first source gas is passed through the cathode of the fuel cell, and the fuel is supplied. Since the second source gas is passed through the anode of the battery, both the anode and the cathode can be reliably humidified.

  In this case, a fuel generator for generating fuel gas to be supplied to the fuel cell from the source gas and water vapor supplied from the source gas supply means, and a humidifier for humidifying the oxidant gas to be supplied to the cathode, The first source gas can be humidified inside the humidifier, and the second source gas can be humidified inside the fuel generator.

  In addition, in the transition period of the fuel cell from the stop period to the power generation period, the power generation period may be started based on the conductivity of the electrolyte membrane provided in the fuel cell. By doing so, the water retention state of the electrolyte membrane can be accurately predicted, and the reliability of the determination of the power generation start time of the fuel cell power generator can be improved. More specifically, the power generation period is started based on the conductivity of the electrolyte membrane corresponding to a predetermined relative humidity inside the fuel cell.

  According to the present invention, by exposing the inside of the fuel cell to a humidified raw material gas atmosphere at an appropriate timing, various problems relating to the DSS operation of the fuel cell such as acceleration of drying of the electrolyte membrane, local combustion, and electrode water repellency deterioration are addressed. A fuel cell power generator that can be appropriately handled and can stabilize the performance of the fuel cell can be obtained.

  First, we will outline the basic power generation principle of a solid polymer electrolyte fuel cell and explain the necessity of water retention management of the electrolyte membrane in order to understand the purpose of preventing drying of the electrolyte membrane with humidified feed gas .

  In a fuel cell, a fuel gas such as hydrogen gas is supplied to an anode and an oxidant gas such as air is supplied to a cathode to cause them to react electrochemically to generate electricity and heat simultaneously.

  A polymer electrolyte membrane that selectively transports hydrogen ions is used as the electrolyte membrane, and the porous catalytic reaction layers disposed on both sides of the electrolyte membrane are mainly composed of carbon powder carrying a platinum-based metal catalyst. The reaction of the following formula (1) occurs in the catalytic reaction layer of the anode, the reaction of the following formula (2) occurs in the catalytic reaction layer of the cathode, and the fuel cell as a whole has the following formula (3). A reaction occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + 1 / 2O ₂ → H ₂ O (3)
That is, hydrogen ions generated by the reaction of the formula (1) are transported from the anode to the cathode through the electrolyte membrane, and electrons are moved from the anode to the cathode through the external circuit. At the cathode, oxygen gas and hydrogen ions and Electrons react as shown in formula (3) to generate water, and heat of reaction due to catalytic reaction can be obtained.

  As described above, the electrolyte membrane needs to have a function of selectively transporting hydrogen ions. By holding water in the electrolyte membrane, ions that can transport hydrogen ions from the anode to the cathode using the water contained in the electrolyte membrane as a movement path. It is thought that conductivity develops.

  Therefore, in order to secure hydrogen ion transport capability, it is essential to retain the electrolyte membrane. Proper management of the electrolyte membrane water retention by preventing the electrolyte membrane from drying is important for the basic performance of the electrolyte membrane. Technical matter.

  Next, the configuration of an existing polymer electrolyte fuel cell will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional view of a solid polymer electrolyte fuel cell equipped with an electrolyte assembly (MEA).

  An anode 14a and a cathode 14c are arranged on both sides of a polymer electrolyte membrane 11 made of perfluorocarbon sulfonic acid having hydrogen ion conductivity so as to sandwich the electrolyte membrane 11. Note that the subscript a of the reference number indicates that related to the anode 14a on the side involving the fuel gas such as hydrogen gas, and the subscript c indicates that related to the cathode 14c on the side involving the oxidant gas such as air. ing.

  Both the anode 14a and the cathode 14c have a two-layer film structure, and the first layer film in contact with the electrolyte film 11 is composed of a catalyst in which a noble metal such as platinum is supported on porous carbon and a polymer having hydrogen ion conductivity. A catalyst reaction layer 12a (hereinafter referred to as catalyst reaction layer 12a) of the anode 14a and a catalyst reaction layer 12c (hereinafter referred to as catalyst reaction layer 12c) of the cathode 14c made of a mixture with an electrolyte, and these catalyst reaction layers 12a and 12c. The second layer film laminated in close contact with the outer surface of the gas diffusion layer 13a of the anode 14a (hereinafter referred to as the gas diffusion layer 13a) and the gas diffusion layer 13c (hereinafter referred to as the gas diffusion layer 13c) of the cathode 14c having both air permeability and electrical conductivity. Gas diffusion layer 13c).

  The MEA 17 includes an electrolyte membrane 11, an anode 14a, and a cathode 14c. The MEA 17 is mechanically fixed, and adjacent MEAs 17 are electrically connected in series.

  In addition, a conductive separator plate 16a (hereinafter referred to as a conductive separator plate 16a) for the anode 14a is disposed in contact with the outer surface of the anode 14a. , Conductive separator plate 16c).

  Further, a fuel for the anode 14a comprising a groove (depth: 0.5 mm) for supplying a reaction gas to the anode 14a and the cathode 14c and carrying away a reaction product gas after the reaction and an excess reaction gas that did not contribute to the reaction. A gas flow path 18a (hereinafter referred to as gas flow path 18a) and an oxidant gas flow path 18c (hereinafter referred to as gas flow path 18c) for the cathode 14c are formed on the contact surfaces of the conductive separator plates 16a and 16c with the MEA 17. Yes.

  Thus, a fuel cell (single cell) 20 composed of the MEA 17 and the separator plates 16a and 16c is formed.

  For example, about 60 fuel cells 20 are stacked inside the fuel cell 21, and more specifically, the outer surface of the conductive separator plate 16a of one fuel cell 20 and the other fuel cell. The fuel cells 20 are stacked so that the outer surfaces of the conductive separator plates 16c of the cells 20 face each other and come into contact with each other.

  Further, a groove (depth: 0.5 mm) 19a formed in the conductive separator plate 16a and a conductive separator plate 16c are formed on the contact surface of the conductive separator plate 16a and the conductive separator 16c adjacent thereto. A cooling water passage 19 including a groove (depth: 0.5 mm) 19c is provided.

  Thus, the temperature of the conductive separator plates 16a and 16c is adjusted by the cooling water flowing inside the cooling water passage 19, and the temperature of the MEA 17 can be adjusted via these conductive separators 16a and 16c.

  As the conductive separator plates 16a and 16c, for example, graphite plates having an outer size of 20 cm × 32 cm × 1.3 mm and impregnated with a phenol resin are used.

  On the other hand, the MEA gasket 15a on the side of the annular rubber anode 14a (hereinafter referred to as the MEA gasket 15a) and the MEA gasket 15c on the cathode 14c side are respectively formed on the anode side main surface and the cathode side main surface of the outer periphery of the MEA 17. (Hereinafter referred to as MEA gasket 15c) is provided, and the gap between the conductive separator plates 16a and 16c and the MEA 17 is sealed by the MEA gaskets 15a and 15c. Thus, gas mixing and gas leakage of the gas flowing through the gas flow paths 18a, 18c are prevented by the MEA gaskets 15a, 15c. Further, manifold holes (not shown) for cooling water flow, fuel gas flow and oxidant gas flow are formed outside the MEA gaskets 15a and 15c.

  The configuration and operation of the gas supply system of the fuel cell power generator using the fuel cell as described above will be described with reference to the drawings. FIG. 2 is a block diagram showing a basic configuration of the fuel cell power generator.

  First, the basic configuration of the fuel cell power generator 100 of the present invention will be described with reference to FIGS. 1 and 2.

  The fuel cell power generation apparatus 100 mainly includes a raw material gas supply means 22 for supplying a raw material gas to the fuel generator 23, a second water supply means 75 for supplying water to the fuel generator 23, and a raw material gas supply means 22. An oxidant gas (air) is supplied to the fuel generator 23 and the humidifier 23 that generate a hydrogen-rich fuel gas by a reforming reaction from the raw material gas supplied from the water and the water supplied from the second water supply means 75. The air supplied from the blower 28, the first water supply means 74 for supplying water to the humidifier 24, the air supplied from the blower 28, the heat supplied from the fuel generator 23 and the first The humidifier 34 humidifies with water supplied from the water supply means 74, the fuel gas supplied from the fuel generator 23 to the anode 14a, and the humidifier supplied from the humidifier 24 to the cathode 14c. The fuel cell 21 that generates power using the oxidant gas and generates heat, the raw material gas supply means 22 and the first and second water supply means 74 and 75, the fuel generator 23 and the blower 28, and the fuel cell 21 A control unit 27 that controls the control, a circuit unit 25 that extracts electric power generated by the fuel cell 21, a measurement unit 26 that measures a voltage (generated voltage) of the circuit unit 25, and the like. Further, the fuel cell power generator 100 is provided with a first switching valve 29 and first, second, and third shut-off valves 30, 31, and 32, which will be described in detail later, and are controlled by the control unit 27. In addition, the dotted line in FIG. 2 has shown the control signal.

  Next, the gas supply operation during normal operation (power generation) of the fuel cell power generator will be described.

  In the gas purifier 22p of the source gas supply means 22, the performance deterioration material of the fuel cell contained in the source gas is removed to purify the source gas, and then the purified source gas is supplied to the fuel via the source gas supply pipe 63. It is supplied to the generator 23. In this case, since the city gas 13A containing methane gas, ethane gas, propane gas and butane gas is used as the raw material gas, the odorant tertiary butyl mercaptan (TBM) and dimethyl contained in the city gas 13A in the gas cleaning unit 22p. Impurities such as sulfide (DMS) and tetrahydrothiophine (THT) are adsorbed and removed.

  On the other hand, water is supplied into the fuel generator 23 from the second water supply means 75 (for example, a water supply pump).

  Thus, a hydrogen gas-rich fuel gas (reformed gas) is generated from the raw material gas and water vapor by the reforming reaction in the reforming section 23e of the fuel generator 23. The fuel gas delivered from the fuel generator 23 is communicated between the fuel gas supply pipe 61 and the anode side inlet 21 a by the first switching valve 29 and then the anode side of the fuel cell 21 through the fuel gas supply pipe 61. It is supplied to the inlet 21a and used for the reaction of the formula (1) in the anode 14a. The first switching valve 29 is disposed in the middle of the fuel gas supply pipe 61 between the anode side inlet 21 a and the fuel generator 23.

  Of the fuel gas supplied to the fuel cell 21, the one that is not used for the power generation reaction in the fuel cell 21 is sent from the anode side outlet 21 b and is opened through the anode exhaust pipe 47. 30 is led to the outside of the fuel cell 21.

  The first shut-off valve 30 is disposed in the middle of the anode exhaust pipe 47 between the anode side outlet 21 b and the water removal unit 33. The remaining fuel gas led to the outside passes through the second check valve 48 in the middle of the anode exhaust pipe 47 (the second check valve 48 allows the flow) and the first check valve. 41 prevents backflow in the direction of the first connecting pipe 64. Then, after the water is removed by the water removing unit 33 disposed in the anode exhaust pipe 47, the remaining fuel gas is sent to the combustion unit (not shown) of the fuel generator 23, and inside the combustion unit. Burned. The heat generated by this combustion is used as heat for endothermic reaction such as reforming reaction.

  On the other hand, the oxidant gas (air) supplied from the blower 28 as the oxidant gas supply means to the humidifier 24 via the oxidant gas supply pipe 62 is humidified in the humidifier 24 and then opened. The gas is supplied to the cathode side inlet 21c of the fuel cell 21 through the oxidant gas supply pipe 62 through the second shutoff valve 31, and is used for the reaction of the formula (2) at the cathode 14c. The second shut-off valve 31 is disposed in the middle of the oxidant gas supply pipe 62 between the humidifier 24 and the cathode side inlet 21c.

  The water necessary for humidification is supplied to the inside of the humidifier 24 from the first water supply means 74 (for example, a water supply pump), and the heat necessary for humidification is the fuel indicated by a double line in FIG. It is supplied from the generator 23 to the humidifier 24. Of the humidified oxidant gas supplied to the fuel cell 21, the one not used for the power generation reaction in the fuel cell 21 passes through the third shutoff valve 32 in the open state from the cathode side outlet 21 d to the outside of the fuel cell 21. The remaining oxidant gas is recirculated to the humidifier 24 via the cathode exhaust pipe 60, and water and heat contained in the recirculated oxidant gas are sent from the blower 28 inside the humidifier 24. Give to the oxidant gas. The third shut-off valve 32 is disposed in the middle of the cathode exhaust pipe 60 between the cathode side outlet 21d and the humidifier 24. Further, as the humidifying unit 24, a total heat exchange humidifier 34 using an ion exchange membrane and a hot water humidifier 35 are used in combination.

  Here, the raw material gas supply means 22 and the blower 28, the first and second water supply means 74 and 75, the operation of the fuel generator 23 and the fuel cell 21, the switching operation of the first switching valve 29, and the first, The opening and closing operations of the second and third shut-off valves 30, 31, and 32 are controlled by the control unit 27 based on detection signals (for example, temperature signals) of various devices, and appropriate DSS operation is performed.

  Thus, the circuit unit 25 is connected to the output terminal 72a (hereinafter referred to as the output terminal 72a) of the anode 14a and the output terminal 72c (hereinafter referred to as the output terminal 72c) of the cathode 14c, and the circuit unit 25 is connected to the inside of the fuel cell 21. The generated power is taken out, and the generated voltage of the circuit unit 25 is monitored by the measuring unit 26.

  Here, in the fuel generator 23, the raw material gas such as methane gas is contained in the fuel gas sent from the reforming unit 23e in addition to the reforming unit 23e that reforms using steam. A CO shifter 23f that removes part of the carbon gas (CO gas) by a shift reaction, and a CO remover 23g that can reduce the CO gas concentration in the fuel gas sent from the CO shifter 23f to 10 ppm or less are provided. ing. By reducing the CO gas concentration to a predetermined concentration level or less, poisoning of platinum contained in the anode 14a by the CO gas in the operating temperature range of the fuel cell 21 can be prevented, and deterioration of its catalytic activity can be avoided. Of course, the anode 14a uses a catalyst having resistance to CO gas such as platinum-ruthenium to take measures against CO gas poisoning in terms of the catalyst material.

  The reaction transition in the fuel generator 23 will be described more specifically by using methane gas as an example of the raw material gas. The following reaction is performed.

  In the reforming unit 23e, hydrogen gas (about 90%) and CO gas (about 10%) are generated by the steam reforming reaction shown in the equation (4).

_{CH 4 + H 2 O → CO} + 3H 2 (4)
Subsequently, the CO gas is oxidized into carbon dioxide in the CO shift section 23f, and the concentration thereof is reduced to about 5000 ppm (see the formula (5)). CO gas can also be removed by oxidation in the CO removal section 23g on the downstream side of the shift section 23f. However, since the CO removal section 23g oxidizes not only CO gas but also useful hydrogen gas, it is possible in the CO shift section 23f. It is desirable to reduce the CO gas concentration as much as possible.

CO + H ₂ O → CO ₂ + H ₂ (5)
Residual CO gas that could not be removed by the metamorphic part 23f is oxidized and removed by the CO removing part 23g, and the concentration thereof is reduced to about 10 ppm or less (see the equation (6)). Thus, it is possible to reach a CO gas concentration level that can be used as a fuel gas used in the fuel cell 21. Incidentally, the total reaction formula of the fuel generator 23 is shown in the formula (7).

CO + 1 / 2O ₂ → CO ₂ (6)
_{CH 4 + 2H 2 O → CO} 2 + 4H 2 (7)
Next, the operation at the start of startup of the fuel cell power generation apparatus 100 will be described.

  If the temperature of the fuel generator 23 (reforming part 23e) is 700 ° C. or lower, the reforming reaction of the formula (4) is not generated in the fuel generator 23 (reforming part 23e). For this reason, at the start of startup, the gas delivered from the fuel gas is not led to the anode side inlet 21a, and the fuel gas supply pipe 61 is connected to the anode exhaust pipe 47 by the switching operation of the first switching valve 29. The connecting pipe 64 is communicated with the first check valve 41 provided in the middle thereof, and the gas sent from the fuel generator 23 is sent to the first check valve 41 (the first check valve is The direction of allowing flow) to the anode exhaust pipe 47. Thereafter, this gas is prevented from flowing back in the direction of the anode side outlet 21 b by the second check valve 48, is removed by the water removal unit 33, and is then supplied to the combustor of the fuel generator 23. It is burned inside the combustor. As a result, the temperature of the fuel generator 23 (the reforming unit 23e) can be quickly increased, and the time from the start to the power generation can be shortened.

  Furthermore, the operation | movement at the time of the start stop of the fuel cell electric power generating apparatus 100 is demonstrated.

  When starting and stopping the fuel cell power generation apparatus 100, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, and the fuel gas supply pipe 61 and the anode side inlet 21a are shut off. Further, the first, second, and third shut-off valves 30, 31, and 32 are closed. Thus, after starting and stopping, the fuel gas can be sealed in the anode 14 a of the fuel cell 21, and the oxidant gas can be sealed in the cathode 14 c of the fuel cell 21.

(Embodiment 1)
Although the operation of the gas supply system of the basic configuration of the fuel cell power generator is outlined during normal operation (power generation), start-up, and operation stop, stop and power generation are frequently alternated with a stop period and a power generation period. In a fuel cell power generation device (for example, a household fuel cell power generation device) that repeats the above, the inside of the fuel cell is exposed to a humidified source gas atmosphere during the transition period from the stop period of the fuel cell to the power generation period. This eliminates the technical problem related to the repeated operation of starting and stopping the fuel cell, such as the local combustion of the fuel cell caused by the drying of the electrolyte membrane when the fuel cell is stopped and the oxygen gas contamination caused by long-term storage. it can.

  Here, the humidification of the raw material gas refers to maintaining the atmosphere of the raw material gas so that the dew point of the raw material gas becomes equal to or higher than the operating temperature of the fuel cell.

  Hereinafter, a configuration example and an operation example of the gas supply system of the fuel cell power generation device, in which the inside of the fuel cell is exposed to the humidified raw material gas during the transition period, will be described.

  FIG. 3 is a block diagram showing the configuration of the fuel cell power generator according to Embodiment 1, and FIGS. 4A and 4B are flowcharts for explaining the gas supply operation of the fuel cell power generator of FIG.

  Fuel cell 21, first water supply means 74, second water supply means 75, source gas supply means 22, fuel generator 23, humidifier 24, impedance measuring instrument 73, circuit unit 25, measurement unit 26, and control unit The configuration 27 is the same as that described in the basic configuration (see FIGS. 1 and 2).

  However, Embodiment 1 is different from the basic configuration in that the input sensor of the control unit 27 such as the piping for introducing the humidified raw material gas into the fuel cell 21, the switching valve, the shutoff valve, and the mass flow meter is as follows. Here, the description will focus on the changes in the input sensors such as the piping, the switching valve, the shutoff valve, and the mass flow meter.

  In FIG. 3, a mass flow meter 70a (hereinafter referred to as a mass flow meter 70a) of the anode 14a for measuring the gas flow rate is disposed in the middle of the fuel gas supply pipe 61 immediately after the outlet of the fuel generator 23. A first switching valve 29 downstream of the mass flow meter 70a and upstream of the anode side inlet 21a of the fuel cell 21 extends from the fuel generator 23 and communicates with the anode side inlet 21a. It is arranged in the middle.

  Further, the first switching valve 29 is communicated with the anode exhaust pipe 47 through the first connection pipe 64 in which the first check valve 41 is arranged as in FIG. In addition, the position of the connection site | part of the 1st connection piping 64 and the anode exhaust piping 47 exists between the water removal part 33 and the 2nd non-return valve 48. FIG.

  A second switching valve 42 is arranged in the middle of the anode exhaust pipe 47 extending from the anode outlet side 21 b to the fuel generator 23. The second switching valve 42 is located downstream of the second switching valve 42 and upstream of the water removal unit 33. The first shut-off valve 30 and the second check valve 48 are arranged in the order of the anode exhaust pipe 47 in this order.

  Further, in the middle of the oxidant gas supply pipe 62 extending from the humidifier 24 to the cathode side inlet 21c, a second shut-off valve 31 and a third switching valve 43 are provided in this order, and the humidifier from the cathode side outlet 21d is provided. A fourth switching valve 44 and a third shut-off valve 32 are provided in this order in the middle of the cathode exhaust pipe 60 extending to 21.

  In addition, the third switching valve 43 is connected to the middle of the anode exhaust pipe 47 via the first circulation pipe 45, and the fourth switching valve 44 is connected to the second circulation pipe 46 via the second circulation pipe 46. A switching valve 42 is connected. In addition, the position of the connection part of the 1st circulation piping 45 and the anode exhaust piping 47 exists between the water removal part 33 and the 2nd non-return valve 48. FIG.

  Further, a temperature detecting means 71 (preferably a thermocouple of a Pt resistor) 71 for detecting the temperature inside the fuel cell 21 is disposed in the vicinity of the center of the fuel cell 21 as shown in FIG. Embedded in the conductive separator plate 16c of the cathode 14c (see FIG. 1).

  Further, in order to obtain the membrane resistance (conductivity) of the electrolyte membrane 11 of the fuel cell 21 described in detail later, an impedance measuring device 73 connected to the output terminals 72a and 72c is provided.

  The circuit unit 25 is connected to the output terminals 72a and 72c, and the electric power generated inside the fuel cell 21 in the circuit unit 25 is taken out, and the voltage (generated voltage) of the circuit unit 25 is monitored by the measuring unit 26. Is done.

  Here, the output signal of the mass flow meter 70 a, the output signal of the temperature detection means 71 (via the measurement unit 26), and the output signals of the output terminals 72 a and 72 c (via the impedance measuring device 73) are input to the control unit 27. Is done. Thus, the flow rate of the raw material gas is monitored by the control unit 27 based on the output signal of the mass flow meter 70a, and the internal temperature of the fuel cell 21 is controlled by the control unit based on the processing signal obtained by processing the output signal of the temperature detecting means 71 by the measuring unit 26. 27, and the membrane resistance of the electrolyte membrane 11 is monitored by the control unit 27 based on the processing signal obtained by processing the output signals of the output terminals 72 a and 72 c by the impedance measuring device 73. In addition, the switching operation of the first, second, third, and fourth switching valves 29, 42, 43, and 44 and the first, second, and third shielding valves 30, 31, which will be described below by the control unit 27. The opening / closing operation of 32 is controlled.

  In the following, the fuel gas and oxidant gas supply operations are divided into a storage operation and a start start operation of the fuel cell power generation device, a confirmation operation of whether or not to start power generation, and a power generation operation. This will be described in detail with reference to the flowchart of 4B.

[Stopping storage operation of fuel cell power generator]
After the fuel cell power generation device 100 is stopped, the fuel cell power generation device 100 is stored for a long period of time by keeping the inside of the fuel cell 21 filled and sealed with the raw material gas. Here, in order to stop and store the fuel cell power generator 100, the switching valve and the shutoff valve are operated as follows (step S401).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the first circulation pipe 45. Furthermore, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46.

  In this way, the fuel gas and the oxidant gas can be reliably sealed inside the fuel cell 21. Note that the inside of the fuel cell 21 is maintained at a fuel cell operating temperature (70 ° C.) or lower, and is usually kept near room temperature (about 20 ° C. to 30 ° C.).

[Starting operation of fuel cell generator]
In order to purge the inside of the fuel cell 21 with the humidified raw material gas, which will be described later, first, the raw material gas is selected and the raw material gas is cleaned so as not to adversely affect the catalyst of the fuel cell 21 (step S402).

  Specifically, in order to prevent the platinum catalyst of the fuel cell 21 from being adsorbed on the surface and preventing the hydrogen overvoltage from increasing, removal of impurities in the raw material gas, especially removal of sulfur components, is an indispensable cleaning process. It is. Further, as the selection of the raw material gas itself, it is necessary to select a gas that does not inhibit the activity of the platinum catalyst of the fuel cell 21. From this viewpoint, methane gas, propane gas, butane gas, and ethane gas (or a mixed gas thereof) are required. It is desirable to use any gas.

  Next, the temperature inside the fuel cell 21 is raised to the operating temperature (70 ° C.) (step S403).

  As a specific temperature raising method, for example, a heater (not shown) or hot water stored in a cogeneration water heater (not shown) of the fuel cell power generation apparatus 100 is used. The internal temperature of the fuel cell 21 is monitored by the control unit 27 based on a detection signal from the temperature detection means 71, and an appropriate temperature raising operation of the fuel cell 21 is controlled.

  Here, it is determined whether or not the internal temperature of the fuel cell 21 has reached or exceeded the operating temperature (70 ° C.) (step S404). If the temperature rise is insufficient (No in S404), the temperature raising operation of S403 is performed. If the temperature reaches 70 ° C. or higher (Yes in S404), the process proceeds to the next step.

  Subsequently, in order to preheat the inside of the fuel generator 23, the switching valve and the shutoff valve are operated as follows (step S405).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the first circulation pipe 45. Furthermore, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46.

  In this way, the gas sent from the fuel generator 23 and flowing through the fuel gas supply pipe 61 passes through the first connecting pipe 64 (the direction in which the first check valve 41 allows the flow) and the anode exhaust pipe 47 to pass through the fuel generator 23. It is made to recirculate | reflux to the combustion part of this, and it burns inside a combustion part.

  As a result, the fuel generator 23 is preheated to a predetermined temperature range (a temperature range in which CO gas is not generated from the raw material gas and water vapor in the fuel generator 23 (reforming section 23e) and carbon of the raw material gas is not precipitated). (Step S406).

  The specific temperature range of the fuel generator 23 is 300 ° C. or lower for the following reason. The range of the temperature rise temperature is preferably 250 ° C. or more from the viewpoint of heating and humidifying the raw material gas most efficiently.

  When the temperature of the fuel generator 23 exceeds 700 ° C., hydrogen gas is generated from the raw material gas and the water vapor by the reforming reaction of the fuel generator 23 (the reforming unit 23e), and the inside of the fuel cell 21 is generated by such hydrogen gas. Is purged, there is a possibility that local combustion may occur inside the fuel cell 21 due to the hydrogen gas as soon as power generation is started.

  When the temperature of the fuel generator 23 (reforming part 23e) is 700 ° C. or lower, hydrogen gas is not generated by the reforming reaction, but within the temperature range of 500 ° C. or higher and 700 ° C. or lower, the fuel generator 23 (reforming part) In 23e), the raw material gas may be carbonized to cause carbon deposition from the raw material gas, and it is not preferable to keep the temperature of the fuel generator 23 (the reforming unit 23e) at a temperature of 500 ° C. or higher. In addition, if the temperature of the fuel generator 23 (reformer 23e) is 300 ° C. or less, the carbon monoxide gas having the catalytic poisoning action of the MEA 17 in the fuel generator 23 (reformer 23e) is the raw material gas and water vapor. Will not occur.

  For the above reasons, it is preferable to keep the temperature of the fuel generator 23 (reformer 23e) at 300 ° C. or lower and use the raw material gas humidified in this temperature range as the purge gas.

  The temperature of the fuel generator 23 (reforming unit 23e) is monitored by the control unit 27 based on the detection signal of the reforming temperature measuring unit (not shown), and the fuel generator 23 (reforming unit 23e). The appropriate temperature rising operation is achieved.

  Here, it is determined whether or not the temperature of the fuel generator 23 (the reforming unit 23e) has been raised to a range of 250 ° C. to 300 ° C. (step S407), and if the temperature rise is insufficient (No in S407). When the preheating operation of the fuel generator 23 in S406 is continued and the temperature is raised to a range of 250 ° C. to 300 ° C. (Yes in S407), the process proceeds to the next step.

  After the preheating of the fuel generator 23, the raw material gas is supplied so that the dew point of the raw material gas supplied from the raw material gas supply means 22 can be maintained above the operating temperature (70 ° C.) of the fuel cell 21. The state is shifted to a state where the humidification process can be performed (step S408). The fuel generator 23 has already been heated to around 300 ° C., and water required for humidification can be supplied from the second water supply means 75 to the fuel generator 23. It is possible to humidify the source gas.

  Subsequently, the switching valve and the shutoff valve are operated as follows for supplying the humidified raw material gas (step S409).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the first switching valve 29 is operated to cut off the fuel gas supply pipe 61 from the anode exhaust pipe 47, while the fuel gas supply pipe 61 is communicated with the anode side inlet 21a. Further, the second switching valve 42 is operated to shut off the anode side outlet 21 b from the first shut-off valve 30, while allowing the anode side outlet 21 b to communicate with the second circulation pipe 46. Further, the third switching valve 43 is operated to shut off the cathode side inlet 21 c from the second shut-off valve 31, while allowing the cathode side inlet 21 c to communicate with the first circulation pipe 45. Furthermore, the fourth switching valve 44 is operated to shut off the cathode side outlet 21d from the third shut-off valve 32, while allowing the cathode side outlet 21d to communicate with the second circulation pipe 46.

  After performing the above valve operation, the humidified raw material gas sent from the fuel generator 23 humidifies the inside of the fuel cell 21 as follows, and is guided to the outside. The purge process of replacing the atmosphere is performed (step S410).

  The raw material gas supplied from the raw material gas supply means 22 is purified by the gas cleaning unit 22p, then sent to the fuel generator 23 via the raw material gas supply pipe 63, and is humidified inside the fuel generator 23. . Thereafter, the humidified raw material gas is sent out from the fuel generator 23 and flows into the fuel cell 21 from the anode side inlet 21a of the fuel cell 21 via the fuel gas supply pipe 61, and the anode 14a has an atmosphere of the humidified raw material gas. Then, the humidified raw material gas is sent out from the anode side outlet 21d and flows out of the fuel cell 21. Subsequently, the humidified raw material gas is switched in the direction of the second circulation pipe 46 by the second switching valve 42 and passes through the second circulation pipe 46, and the fuel cell cathode side by the fourth switching valve 44. The direction is switched in the direction of the outlet 21d, and the fuel cell 21 flows again into the fuel cell 21 again. Thus, the cathode 14c is exposed to the atmosphere of the humidified source gas, and the source gas is sent out from the cathode side inlet 21c and flows out of the fuel cell 21 again.

  Thereafter, the direction of the raw material gas is switched by the third switching valve 43, flows in the direction of the first circulation pipe 45, and reaches the anode exhaust pipe 47. The raw material gas that has reached the anode exhaust pipe 47 is prevented from flowing back by the first and second check valves 41, 48, and is guided in the direction of the water removing unit 33, and is supplied from the humidified raw material gas in the water removing unit 33. After the water is removed, it is sent to the combustion section of the fuel generator 23.

  That is, the humidified raw material gas passes in the order of the anode side inlet 21a, the anode side outlet 21b, the cathode side outlet 21d, and the cathode side inlet 21c of the fuel cell 21 as shown by the thick dotted line in FIG. It flows in an annular shape and reaches the anode exhaust pipe 47. The fuel gas supplied to the combustion section is combusted inside the combustion section, and the heat generated by this combustion is used for heating the fuel generator 23.

  The total supply amount of the humidified raw material gas needs to be at least three times the gas filling capacity of the internal space of the fuel cell 21. For example, if the gas filling capacity is about 1.0 L, the humidifying raw material gas flow rate 1 This may be supplied to the inside of the fuel cell 21 at 5 L / min for about 5 minutes, and the total supply amount is monitored by the control unit 27 based on the output signal of the mass flow meter 70a.

  Thus, the inside of the fuel cell 21 can be exposed to the humidified raw material gas during the transition period from the stop period of the fuel cell 21 to the power generation period, and the electrolyte membrane 11 of the fuel cell 21 dried during the stop storage can be humidified. If oxygen gas is mixed into the fuel cell 21 during stopped storage, local combustion with the fuel gas caused by the oxygen gas can be prevented beforehand.

  Furthermore, since the humidified raw material gas is introduced into the fuel cell 21 during the transition period from the stop period of the fuel cell 21 to the power generation period, the inside of the fuel cell 21 is exposed to the humidified raw material gas atmosphere for a long period of time. And the water repellency of the fuel cell electrode is not impaired.

  In addition, if the oxygen gas mixed in the anode 14a during the storage stop of the fuel cell 21 remains, ruthenium elution is caused and the catalytic function is lost. Therefore, the humidified raw material gas is introduced to the cathode 14c after passing through the anode 14a. The raw material gas supply method that preferentially excludes the oxygen gas of the anode 14a that is easily oxidized and deteriorated by employing the introduction path is reasonable from the viewpoint of preventing catalyst deterioration.

  Further, both the anode 14a and the cathode 14c can be humidified by a single humidified raw material gas supply path indicated by a thick dotted line in FIG. 3, and the gas supply piping can be simplified.

  After sufficiently supplying the humidified raw material gas to the inside of the fuel cell 21, the switching valve and the shutoff valve are operated as follows (step S411) to promote heating of the fuel generator 23 of the fuel cell power generator 100. Then, the internal temperature of the fuel generator 23 (the reforming unit 23e) is rapidly raised to a temperature (about 700 ° C. or higher) at which the reforming reaction of the equation (4) is possible.

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the first circulation pipe 45. Furthermore, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46.

  In this way, the gas sent from the fuel generator 23 to the fuel gas supply pipe 61 passes through the first connection pipe 64 (the direction in which the first check valve 41 allows the flow) and the anode exhaust pipe 47, and the fuel generator 23. It is made to recirculate | reflux to the combustion part of this, and it burns inside a combustion part. Thereby, the fuel generator 23 is heated to a predetermined temperature range (temperature range in which hydrogen gas is generated from the raw material gas and water vapor by the reforming reaction; 700 ° C. or more) (step S412).

  Here, it is determined whether or not the temperature of the fuel generator 23 (the reforming unit 23e) has risen to 700 ° C. or more (step S413). If the temperature rise is insufficient (No in S413), the heating in S412 is performed. When the operation is continued and reaches 700 ° C. or higher (Yes in S413), the process proceeds to the next step.

[Operation to confirm whether fuel cell generator can start power generation]
After the temperature inside the fuel generator 23 is raised to 700 ° C. or higher, the internal temperature of the fuel cell 21 and the conductivity of the electrolyte membrane 11 of the fuel cell 21 are checked, and the fuel cell power generator 100 generates power. Determine if it is okay to start.

  As a first confirmation operation, it is determined whether or not the internal temperature of the fuel cell 21 is equal to or higher than the operating temperature (70 ° C.) (step S414). If the temperature rise is insufficient (No in S414), the increase in S404 is performed. When the temperature operation is re-executed and the temperature is raised to 70 ° C. or higher (Yes in S414), the process proceeds to the next step.

As a second confirmation operation, the conductivity of the electrolyte membrane 11 of the fuel cell 21 is obtained to determine whether or not this conductivity: σ = 1.93 × 10 ⁻² Scm ⁻¹ or more (step S416). = 1.93 × 10 ⁻² Scm ⁻¹ (No in S416), it is determined that the electrolyte membrane 11 is insufficiently humidified, and the operations of S409 and S410 are re-executed (step S417), and σ = 1 .93 × 10 ⁻² Scm ⁻¹ or more (Yes in S416), the process proceeds to the next step.

  Here, the calculation method of the conductivity of the electrolyte membrane and the relationship between the conductivity of the electrolyte membrane and the relative humidity will be described with reference to the drawings.

In FIG. 5, the horizontal axis represents the actual resistance component Z ′, the vertical axis represents the reactance component Z ″, and the frequency of the alternating current applied to the fuel cell 21 (electrode area: 144 cm ² ) is 0.1 Hz to 1 kHz. An AC impedance profile diagram of the fuel cell 21 measured by varying the range is shown (impedance measurement by AC method). According to FIG. 5, since the AC impedance profile intersects the horizontal axis (Z ′) in the alternating current having the frequency of 1 kHz, it is estimated that the impedance in the alternating current having the frequency of 1 kHz indicates the resistance Rs of the electrolyte membrane 11. That is, FIG. 5 is a schematic diagram of a so-called Cole-Cole plot in which AC impedance is measured. In this case, the resistance value of the intersection of the semicircle and the horizontal axis is small (shown in FIG. 5). Rs) means the membrane resistance of the electrolyte membrane 11.

  An AC voltage for measurement (1 kHz) is applied from the impedance measuring device 73 to the output terminals 72a and 72c of the fuel cell 21 connected to the impedance measuring device 73 (see FIG. 3) controlled by the control unit 27. The conductivity of the electrolyte membrane 11 can be estimated based on the alternating current impedance of the electrolyte membrane 11 of the fuel cell 21 obtained in this way. Specifically, for example, an alternating current voltage (1 kHz) is applied to every 10 cells of the fuel cell 20 to measure an alternating current impedance, and the conductivity of the electrolytic film 11 is determined from the measured value and the film thickness and area of the electrolytic film 11. The rate is calculated.

If the conductivity obtained by such a calculation method is σ = 1.93 × 10 ⁻² Scm ⁻¹ or more, the fuel cell 21 is in a state in which power generation can be started for the following reason based on FIG. Can be determined.

  6, when the temperature of the electrolyte membrane 11 is kept at 80 ° C., the horizontal axis represents the relative humidity of the polymer electrolyte membrane (Nafion 112 electrolyte membrane of DuPont, USA, film thickness is 50 μm), and the vertical axis represents The correlation between the electrolyte membranes is shown by taking the conductivity of the electrolyte membrane, and it is for explaining how the conductivity of the electrolyte membrane depends on the relative humidity of the electrolyte membrane.

According to FIG. 6, as the electrolyte membrane is dried, the conductivity of the electrolyte membrane gradually approaches zero (relative humidity: near 20%), but as the electrolyte membrane increases in humidity, the conductivity also increases monotonously. A trend is observed. Here, in view of the performance of the electrolyte membrane, assuming that the sufficiently maintained relative humidity is 50% or more, the conductivity corresponding to this relative humidity is σ = 1.93 × 10 ⁻² Scm ⁻¹ .

Therefore, the conductivity of the electrolyte membrane (for example, σ = 1.93 × 10 ⁻² Scm ^{−1 in the} case of the Nafion 112 electrolyte membrane) can be used as a simple index for obtaining the water retention state of the electrolyte membrane. In other words, it can be said that whether or not the fuel cell 21 can start power generation can be predicted based on the conductivity.

  In this way, in addition to the determination based on the temperature of the fuel cell, the generation start timing of the fuel cell having the stop period and the power generation period is determined based on the conductivity of the electrolyte membrane of the fuel cell, so that the water retention state of the electrolyte membrane is accurately determined. Thus, the reliability of the determination of the power generation start time of the fuel cell power generator can be improved.

[Power generation operation of fuel cell power generator]
After the numerical value of the confirmation operation reaches a predetermined value (specifically, the temperature of the fuel cell 21 is 70 ° C. or higher, the conductivity of the electrolyte membrane σ = 1.93 × 10 ⁻² Scm ⁻¹ or higher), the switching valve And the shut-off valve is operated as follows to generate power in the fuel cell 21 (steps S418 and S419).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are all opened. Plug.

  In this state, the first switching valve 29 is operated to shut off the fuel gas supply pipe 61 from the anode exhaust pipe 47, while allowing the fuel gas supply pipe 61 to communicate with the anode side inlet 21a. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Then, the third switching valve 43 is operated to connect the cathode side inlet 21 c to the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the first circulation pipe 45. Further, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46.

  By operating the switching valve and the shutoff valve, the hydrogen gas-rich fuel gas sent from the fuel generator 23 through the fuel gas supply pipe 61 is introduced into the anode side inlet 21a of the fuel cell 21, and the anode side outlet 21b. The remaining fuel gas that has been discharged from the fuel and not consumed by the anode 14 a is recirculated to the fuel generator 23 of the fuel cell 21 via the anode exhaust pipe 47.

  On the other hand, the humidified air (humidified oxidant gas) sent from the humidifier 23 through the oxidant gas supply pipe 62 is introduced into the cathode side inlet 21c of the fuel cell 21, and sent out from the cathode side outlet 21d to be supplied to the cathode 14c. The remaining oxidant gas that has not been consumed in step 1 is recirculated to the humidifier 24 of the fuel cell 21 via the cathode exhaust pipe 60.

  Thus, the fuel gas is supplied to the anode 14a, the oxidant gas is supplied to the cathode 14c, hydrogen ions and electrons are generated inside the fuel cell 21, and the current is supplied to the circuit unit 25 through the output terminals 72a and 72c. And the generated voltage is monitored by the measuring unit 26.

(Embodiment 2)
Hereinafter, another configuration example of the gas supply system of the fuel cell power generation apparatus 100 in which the inside of the fuel cell 21 is exposed to the humidified raw material gas during the transition period from the stop period to the power generation period will be described.

  FIG. 7 is a block diagram showing the configuration of the fuel cell power generator according to Embodiment 2. In FIG.

  Fuel cell 21, first water supply means 74, second water supply means 75, source gas supply means 22, fuel generator 23, humidifier 24, impedance measuring instrument 73, circuit unit 25, measurement unit 26, and control unit The configuration 27 is the same as that described in the first embodiment.

  However, the second embodiment is different from the first embodiment (FIG. 3) in that the arrangement of the piping for introducing the humidified raw material gas into the fuel cell 21, the switching valve, the shutoff valve, and the mass flow meter is changed as follows. Here, the description will focus on the changes in the piping, the switching valve, the shutoff valve, and the mass flow meter.

  The first circulation pipe 45 connecting the third switching valve 43 and the anode exhaust pipe 47 shown in FIG. 3 is removed. In addition, a sixth switching valve 54 is arranged immediately after the outlet of the gas cleaning unit 22p, thereby sending the purified source gas to the humidifier 24 (source gas branch pipe 51) and to the fuel generator 23. Perform the switching operation. In addition, a raw material gas branch pipe 51 that communicates the third switching valve 43 and the sixth switching valve 54 through the inside of the humidifying unit 24 is provided. Further, a fifth switching valve 52 is added in the middle of the fuel gas supply pipe 61 connecting the downstream side of the first switching valve 29 and the upstream side of the anode side inlet 21 a of the fuel cell 21. The second connecting pipe 53 is provided to connect the switching valve 52 and the anode exhaust pipe 47. In addition, the position of the connection part of the 2nd connection piping 53 and the anode exhaust piping 47 exists between the 2nd non-return valve 48 and the water removal part 33. FIG. Further, the mass flow meter 70a (see FIG. 3) is removed, and the mass flow meter 70c (hereinafter referred to as the mass flow meter 70c) of the cathode 14c for measuring the gas flow rate is interposed between the humidifier 24 and the third switching valve 43. And disposed in the middle of the source gas branch pipe 51.

  Hereinafter, the supply operation of the fuel gas and the oxidant gas will be divided into a stop storage operation, a start start operation, a power generation start availability confirmation operation and a power generation operation, with reference to the block diagram of FIG. 7 and the flowcharts of FIGS. 8A and 8B. However, it explains in detail.

[Stopping storage operation of fuel cell power generator]
After the fuel cell power generator is stopped, the inside of the fuel cell 21 is kept in a state of being filled and sealed with the raw material gas and stored for a long time. Here, in order to stop and store the fuel cell power generator 100, the switching valve and the shutoff valve are operated as follows (step S801).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the fifth switching valve 52, while the fuel gas supply pipe 61 is disconnected from the anode exhaust pipe 47. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. Further, the fourth switching valve 44 is operated to connect the cathode-side outlet 21d and the third shut-off valve 32, while the cathode-side outlet 21d and the second circulation pipe 46 are shut off. In addition, the fifth switching valve 52 is operated to connect the anode side inlet 21a to the first switching valve 29, while the anode side inlet 21a is disconnected from the anode exhaust pipe 27.

  In this way, the fuel gas and the oxidant gas can be reliably sealed inside the fuel cell 21. The temperature inside the fuel cell 21 is usually near room temperature (about 20 ° C. to 30 ° C.), which is kept lower than the fuel cell operating temperature (70 ° C.).

[Starting operation of fuel cell generator]
First, the raw material gas is selected and the raw material gas is cleaned so as not to adversely affect the catalyst of the fuel cell 21 (step S802). The method of cleaning the source gas and the content of the source gas selection are the same as in the first embodiment.

  Next, the temperature inside the fuel cell 21 is raised to the operating temperature (70 ° C.) (step S803). The temperature raising method inside the fuel cell 21 is the same as that described in the first embodiment.

  Here, it is determined whether or not the internal temperature of the fuel cell 21 has reached the operating temperature (70 ° C.) or higher (step S804), and if the temperature rise is insufficient (No in S804), the temperature rise in S803. If the operation is continued and the temperature reaches 70 ° C. or higher (Yes in S804), the process proceeds to the next step.

  Subsequently, the raw material gas can be humidified inside the humidifier 24 using the water supplied from the first water supply means 74 to the humidifier 24 and the heat supplied from the fuel generator 23 to the humidifier 24. The state is shifted (step S805).

  Specifically, hot water is required for humidifying the raw material gas, but since the humidifier 24 does not have a combustor as a heat source, it is necessary to appropriately receive heat from the outside of the humidifier 24. In the second embodiment, the heat generated in the combustor of the fuel generator 23 is supplied to the humidifier 24 as shown in FIG. By giving, the temperature of the humidifier 24 is increased.

  Subsequently, in order to supply the humidified raw material gas into the fuel cell 21, various shutoff valves and switching valves are operated as follows (step S806).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

  In this state, the second switching valve 42 is operated to shut off the anode-side outlet 21b from the first shut-off valve 30, while the anode-side outlet 21b and the second circulation pipe 46 are communicated. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c to the source gas branch pipe 51, while the cathode side inlet 21 c is shut off from the shutoff valve 31. Further, the fourth switching valve 44 is operated to shut off the cathode side outlet 21d from the second shut-off valve 31, while allowing the cathode side outlet 21d to communicate with the second circulation pipe 46. In addition, the fifth switching valve 52 is operated to shut off the anode side inlet 21a from the first switching valve 29, while the anode side inlet 21a is connected to the anode exhaust pipe 47. Further, the sixth switching valve 54 is operated to connect the gas cleaning unit 22p and the raw material gas branch pipe 51, while the gas cleaning unit 22p is disconnected from the fuel generator 23.

  In this way, the cleaning raw material gas is supplied into the fuel cell 21 through the following path (step S807), and a purge process is performed in which the inside of the fuel cell 21 is replaced with the humidified raw material gas atmosphere.

  The source gas supplied from the source gas supply means 22 and purified by the gas cleaning unit 22p is directed to the source gas branch pipe 51 by the sixth switching valve 54 through the source gas supply pipe 63, and is supplied to the source gas. It flows into the humidifier 24 via the branch pipe 51 and is humidified inside the humidifier 24 (more precisely, a hot water humidifier). Subsequently, the humidified source gas is switched in the direction of the cathode side inlet 21 c of the fuel cell 21 by the third switching valve 43 and flows into the fuel cell 21. Thus, the cathode 14c is exposed to the atmosphere of the humidified source gas, and the humidified source gas flows out from the cathode side outlet 21d.

  The humidified source gas is then switched in the direction of the second circulation pipe 46 by the fourth switching valve 44, and the source gas passes through the second circulation pipe 46 along one side of the fuel cell 21, The switching valve 42 switches the direction in the direction of the anode-side outlet 21b of the fuel cell 21 and flows again into the fuel cell 21. Thus, the anode 14a is exposed to the atmosphere of the humidified raw material gas, and this humidified raw material gas flows out again from the anode side inlet 21a.

  The humidified raw material gas after reflowing is switched in the direction of the second connection pipe 53 by the fifth switching valve 52 and reaches the anode exhaust pipe 47 through the second connection pipe 53. The raw material gas that has reached the anode exhaust pipe 47 is prevented from flowing back by the first and second check valves 41, 48, and is guided in the direction of the water removing unit 33, and is supplied from the humidified raw material gas in the water removing unit 33. After the water is removed, it is sent to the combustion section of the fuel generator 23 and burned inside the combustor.

  That is, the humidified source gas passes through the periphery of the fuel cell 21 in the order of the cathode side inlet 21c, the cathode side outlet 21d, the anode side outlet 21b, and the anode side inlet 21a of the fuel cell 21 as shown by the thick dotted line in FIG. It flows in a conical shape and reaches the anode exhaust pipe 47. The total supply amount of the humidified raw material gas needs to be at least three times the gas filling capacity of the internal space of the fuel cell 21. For example, if the gas filling capacity is about 1.0 L, the humidifying raw material gas flow rate 1 This may be supplied to the inside of the fuel cell 21 at about 5 L / min for about 5 minutes, and this total supply amount is monitored by the control unit 27 based on the output signal of the mass flow meter 70c.

  Thus, the inside of the fuel cell 21 can be exposed to the humidified raw material gas during the transition period from the stop period of the fuel cell 21 to the power generation period, and the electrolyte membrane 11 of the fuel cell 21 dried during the stop storage can be humidified. If oxygen gas is mixed into the fuel cell 21 during stopped storage, local combustion with the fuel gas caused by the oxygen gas can be prevented.

  Further, since the humidified raw material gas is introduced into the fuel cell 21 during the transition period from the stop period of the fuel cell 21 to the power generation period, the inside of the fuel cell 21 is exposed to the humidified raw material gas atmosphere for a long period of time. And the water repellency of the electrode of the fuel cell 21 is not impaired.

  In addition, as shown by the thick dotted line in FIG. 7, both the anode 14a and the cathode 14c can be humidified by a single path, and the gas supply piping can be simplified.

  After sufficiently supplying the humidified raw material gas into the fuel cell 21, the switching valve and the shutoff valve are operated as follows for heating the fuel generator 23 (step S808).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are closed. .

In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is shut off from the fifth switching valve 52. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. In addition, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46. Further, the fifth switching valve 52 is operated to connect the anode side inlet 21 a with the first switching valve 29, while the anode side inlet 21 a is shut off from the anode exhaust pipe 47.
Further, the sixth switching valve 54 is operated to connect the gas cleaning unit 22p to the fuel generator 23, while the gas cleaning unit 22p is disconnected from the source gas branch pipe 51.

  After performing the above valve operation, the gas sent from the fuel generator 23 is switched by the first switching valve 29 and passes through the first connection pipe 64 and the anode exhaust pipe 47 (first reverse). Since the stop valve 41 is allowed to flow), after the water is removed by the water removal unit 33, the fuel generator 23 can be recirculated and combusted in the combustion unit of the fuel generator 23. If possible (step S809), the internal temperature of the fuel generator 23 (the reforming unit 23e) can be raised to a temperature (about 700 ° C. or higher) at which the reforming reaction of the equation (4) is possible.

  Here, it is determined whether or not the temperature of the fuel generator 23 has risen to 700 ° C. or more (step S810). If the temperature rise is insufficient (No in S810), the heating operation in S809 is continued, and 700 When the temperature reaches or exceeds ° C. (Yes in S810), the process proceeds to the next step.

[Operation to confirm whether fuel cell generator can start power generation]
After raising the temperature of the fuel generator 23 to 700 ° C. or higher, the internal temperature of the fuel cell 21 and the conductivity of the electrolyte membrane 11 of the fuel cell 21 are confirmed, and power generation of the fuel cell power generator 100 is started. Determine whether or not

  As a first confirmation operation, it is determined whether or not the internal temperature of the fuel cell 21 is equal to or higher than the operating temperature (70 ° C.) (step S811). If the temperature rise is insufficient (No in S811), the increase in S803 is performed. When the temperature operation is re-executed (step S812) and the temperature is raised to 70 ° C. or higher (Yes in S811), the process proceeds to the next step.

As a second confirmation operation, the conductivity of the electrolyte membrane 11 of the fuel cell 21 is obtained to determine whether or not this conductivity: σ = 1.93 × 10 ⁻² Scm ⁻¹ or more (step S813). = 1.93 × 10 ⁻² Scm ⁻¹ (No in S813), it is determined that the electrolyte membrane 11 is insufficiently humidified, and the operations of S806 and S807 are re-executed (step S814), and σ = 1 .93 × 10 ⁻² Scm ⁻¹ or more (Yes in S813), the process proceeds to the next step. The method for measuring the conductivity of the electrolyte membrane and the relationship between the conductivity of the electrolyte membrane and the relative humidity are the same as those described in the first embodiment.

  In this way, in addition to the determination based on the temperature of the fuel cell, the generation start timing of the fuel cell having the stop period and the power generation period is determined based on the conductivity of the electrolyte membrane of the fuel cell, so that the water retention state of the electrolyte membrane is accurately determined. Thus, the reliability of the determination of the power generation start time of the fuel cell power generator can be improved.

[Power generation operation of fuel cell power generator]
After the numerical value of the confirmation operation reaches a predetermined value (specifically, the temperature of the fuel cell 21 is 70 ° C. or higher, the conductivity of the electrolyte membrane σ = 1.93 × 10 ⁻² Scm ⁻¹ or higher), the switching valve And the shut-off valve is operated as follows to generate power in the fuel cell 21 (steps S815 and S816).

  The first cutoff valve 30 connected to the second switching valve 42, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the fourth switching valve 44 are all opened. Plug.

  In this state, the first switching valve 29 is operated to cut off the fuel gas supply pipe 61 from the anode exhaust pipe 47, while the fuel gas supply pipe 61 is communicated with the fifth switching valve 52. Further, the second switching valve 42 is operated to connect the anode side outlet 21 b with the first shutoff valve 30, while the anode side outlet 21 b is shut off from the second circulation pipe 46. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. Further, the fourth switching valve 44 is operated to connect the cathode side outlet 21d with the third shutoff valve 32, while the cathode side outlet 21d is shut off from the second circulation pipe 46. In addition, the fifth switching valve 52 is operated to connect the anode side inlet 21a with the first switching valve 29, while the anode side inlet 21a is disconnected from the anode exhaust pipe 47. Further, the sixth switching valve 54 is operated to connect the gas cleaning unit 22p to the fuel generator 23, while the gas cleaning unit 22p is disconnected from the source gas branch pipe 51.

  Thus, the operation of the switching valve and the shutoff valve introduces the hydrogen gas-rich fuel gas from the fuel generator 23 to the anode side inlet 21a of the fuel cell 21 via the fuel gas supply pipe 61, and sends it out from the anode side outlet 21b. The remaining fuel gas that has not been consumed in 14 a is recirculated to the fuel generator 23 of the fuel cell 21 via the anode exhaust pipe 47.

  On the other hand, humidified air (oxidant gas) sent from the humidifier 23 through the oxidant gas supply pipe 62 is introduced into the cathode side inlet 21c of the fuel cell 21, and sent out from the cathode side outlet 21d, and is sent from the cathode 14c. The remaining oxidant gas that has not been consumed is recirculated to the humidifier 24 of the fuel cell 21 via the cathode exhaust pipe 60.

  As a result, the fuel gas is supplied to the anode 14a, the oxidant gas is supplied to the cathode 14c, and hydrogen ions and electrons are generated inside the fuel cell 21, and are supplied to the circuit unit 25 via the output terminals 72a and 72c. The current can be taken out, and the generated voltage is monitored in the measuring unit 26.

(Embodiment 3)
Hereinafter, another configuration example of the gas supply system of the fuel cell power generation apparatus, in which the inside of the fuel cell 21 is exposed to the humidified raw material gas during the transition period from the stop period to the power generation period, will be described.

  FIG. 9 is a block diagram showing the configuration of the fuel cell power generator according to Embodiment 3. In FIG. Fuel cell 21, first water supply means 74, second water supply means 75, source gas supply means 22, fuel generator 23, humidifier 24, impedance measuring instrument 73, circuit unit 25, measurement unit 26, and control unit The configuration 27 is the same as that described in the first embodiment.

  The third embodiment is different from the first embodiment in that the arrangement of the piping for introducing the humidified raw material gas into the fuel cell 21, the switching valve, the shutoff valve, and the mass flow meter is changed. Here, the first embodiment is different from the first embodiment. On the other hand, the description will focus on the changes in the introduction piping, the switching valve, the shutoff valve, and the mass flow meter.

  The second and fourth switching valves 42 and 44 and the first and second circulation pipes 45 and 46 used in the first embodiment (FIG. 3) are removed. In addition, a flow dividing valve 55 is disposed immediately after the outlet of the gas cleaning unit 22p. The flow dividing valve 55 determines the ratio of the flow rate of the raw material gas flowing in the direction of the humidifier 23 and the flow rate of the raw material gas flowing in the direction of the fuel generator 23. be able to. In addition, a raw material gas branch pipe 51 that connects the third switching valve 43 and the diversion valve 55 through the inside of the humidifying unit 24 is provided. Further, in addition to the mass flow meter 70 a, a mass flow meter 70 c is provided between the humidifier 24 and the third switching valve 43 and in the middle of the source gas branch pipe 51.

  Hereinafter, the supply operation of the fuel gas and the oxidant gas is divided into a stop storage operation, a start start operation, a power generation start availability confirmation operation and a power generation operation, with reference to the block diagram of FIG. 9 and the flowcharts of FIGS. 10A and 10B. I will explain in detail.

[Stopping storage operation of fuel cell power generator]
After the fuel cell power generation device 100 is stopped, the inside of the fuel cell 21 is kept in a state of being filled and sealed with the raw material gas and stored for a long time. Here, in order to stop and store the fuel cell power generator 100, the switching valve and the shutoff valve are operated as follows (step S1001).

  The first cutoff valve 30 connected to the anode side outlet 21b, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the cathode side outlet 21d are closed.

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51.

  In this way, the fuel gas and the oxidant gas can be reliably sealed inside the fuel cell 21. The inside of the fuel cell 21 is maintained at a fuel cell operating temperature (70 ° C.) or lower, and is kept near room temperature (about 20 ° C. to 30 ° C.).

[Starting operation of fuel cell generator]
A raw material gas is selected and a raw material gas is cleaned so as not to adversely affect the catalyst of the fuel cell 21 (step S1002). The method of cleaning the source gas and the content of the source gas selection are the same as in the first embodiment.

  Subsequently, the temperature inside the fuel cell 21 is raised to the operating temperature (70 ° C.) (step S1003). The temperature raising method inside the fuel cell 21 is the same as that described in the first embodiment.

  Here, it is determined whether or not the internal temperature of the fuel cell 21 has reached or exceeded the operating temperature (70 ° C.) (step S1004). If the temperature rise is insufficient (No in S1004), the temperature rise in S1003. If the operation is continued and the temperature reaches 70 ° C. or higher (Yes in S1004), the process proceeds to the next step.

  Next, in order to preheat the inside of the fuel generator 23, the switching valve and the shutoff valve are operated as follows (step S1005).

  The first cutoff valve 30 connected to the anode side outlet 21b, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the cathode side outlet 21d are closed.

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. Further, the raw material gas flowing through the fuel gas supply pipe 61 with respect to the flow rate of the raw material gas flowing through the raw material gas supply pipe 63 so as to guide the entire amount of the raw material gas flowing through the raw material gas supply pipe 63 to the fuel generator 23 by operating the diversion valve 55. Set the flow diversion ratio to 1.

  Thus, the gas sent from the fuel generator 23 passes through the first connecting pipe 64 by the switching operation of the first switching valve 29 (the direction in which the first check valve 41 allows the flow), and the anode exhaust pipe 47. Then, the backflow is prevented by the second check valve 48 so as to recirculate to the combustion part of the fuel generator 23 and burnt in the combustion part to preheat the fuel generator 23 (step S1006).

  The temperature increase range of the preheating of the fuel generator 23 is the same as that described in the first embodiment (the temperature of the fuel generator 23 (reforming portion 23e) is increased to a range of 250 ° C to 300 ° C). It is.

  Here, it is determined whether or not the temperature of the fuel generator 23 (the reforming unit 23e) has been raised to a range of 250 ° C. to 300 ° C. (step S1007), and if the temperature rise is insufficient (No in S1007). When the preheating operation of the fuel generator 23 in S1006 is continued and the temperature is raised to a range of 250 ° C. to 300 ° C. (Yes in S1007), the process proceeds to the next step.

  After the fuel generator 23 is preheated, the source gas is supplied so that the dew point of the source gas supplied from the source gas supply means 22 in the fuel generator 23 and the humidifier 24 can be maintained at the operating temperature (70 ° C.) or higher of the fuel cell 21. Is moved to a state where the humidification process can be performed (step S1008). The temperature of the fuel generator 23 is raised to about 300 ° C., and water necessary for humidification is supplied from the second water supply means 75 to the fuel generator 23, whereby the source gas is humidified inside the fuel generator 23. it can. At the same time, the raw material gas can be humidified inside the humidifier 24 by the water supplied from the first water supply means 74 to the inside of the humidifier 24 and the heat supplied from the fuel generator 23 to the humidifier 24.

  Subsequently, the switching valve and the shutoff valve are operated as follows for supplying the humidified raw material gas (step S1009).

  The first cutoff valve 30 connected to the second switching valve 42 and the third cutoff valve 32 connected to the fourth switching valve 44 are each opened.

  In this state, the first switching valve 29 is operated to connect the anode side inlet 21a to the fuel gas supply pipe 61, while the anode side inlet 21a is disconnected from the anode exhaust pipe 47. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c to the source gas branch pipe 51, while the cathode side inlet 21 c is shut off from the shutoff valve 31. Furthermore, the flow dividing valve 55 is operated, and the flow dividing ratio is set to 0.5 so that the purified raw material gas sent from the gas cleaning unit 22p can be led almost uniformly to both the humidifier 23 and the fuel generator 23. .

  In this way, the humidified raw material gas sent from the gas cleaning unit 22p is humidified inside the fuel cell 21 and guided to the outside as described below, and the purge is performed to replace the inside of the fuel cell 21 with the humidified raw material gas atmosphere. Processing is performed (step S1010).

  The source gas purified by the gas cleaning unit 22p and sent through the source gas supply pipe 63 is almost the first source gas flowing through the source gas branch pipe 51 and the second source gas flowing through the fuel gas supply pipe 61. The flow is divided evenly (diversion ratio: 0.5).

  In the first source gas, the purified source gas sent from the gas cleaning unit 22p via the source gas supply pipe 63 is diverted by the diverter valve 55, and led to the humidifier 24 through the source gas branch pipe 51. And is humidified in the humidifier 24. Thereafter, the humidified source gas is switched to the cathode side inlet 21 c of the fuel cell 21 by the third switching valve 43 and supplied to the cathode 14 c via the source gas branch pipe 51. Thus, after the cathode 14c of the fuel cell 21 is exposed to the humidified raw material gas atmosphere, the humidified raw material gas flows out from the cathode side outlet 21d. The humidified raw material gas after flowing out returns to the humidifying unit 24 through the cathode exhaust pipe 60, is processed in the humidifying unit 24, and is appropriately diluted and discharged to the atmosphere.

  In the second raw material gas, the purified raw material gas sent from the gas cleaning unit 22p through the raw material gas supply pipe 63 is diverted by the diversion valve 55 and led to the fuel generator 23. Humidified inside. Thereafter, the humidified raw material gas sent from the fuel generator 23 is switched to the anode side inlet 21a of the fuel cell by the first switching valve 29 and supplied to the anode 14a of the fuel cell 21 through the fuel gas supply pipe 61. Is done. Thus, after the anode 14a is exposed to the atmosphere of the humidified raw material gas, the humidified raw material gas flows out of the fuel cell 21 from the anode outlet 21b. After the outflow, the humidified raw material gas is removed by the water removal unit 33 through the anode exhaust pipe 47 and then returned to the combustion unit of the fuel generator 23 and burned in the combustion unit to heat the fuel generator 23. Used.

  Here, the total supply amount of the humidified raw material gas needs to be at least three times the gas filling capacity of the internal space of the fuel cell 21. For example, if the gas filling capacity is about 1.0 L, the humidified raw material gas The flow rate of 1.5 L / min for about 5 minutes may be supplied to the inside of the fuel cell 21, and this total supply amount is monitored by the control unit 27 based on the output signals of the mass flow meter 70a and the mass flow meter 70c. The

  Thus, the inside of the fuel cell 21 can be exposed to the humidified raw material gas during the transition period from the stop period of the fuel cell 21 to the power generation period, and the electrolyte membrane 11 of the fuel cell 21 dried during the stop storage can be humidified. If oxygen gas is mixed inside the fuel cell during stopped storage, local combustion with the fuel gas caused by the oxygen gas can be prevented beforehand. Further, since the humidified raw material gas is introduced into the fuel cell 21 during the transition period from the stop period of the fuel cell 21 to the power generation period, the inside of the fuel cell 21 is exposed to the humidified raw material gas atmosphere for a long period of time. And the water repellency of the fuel cell electrode is not impaired. In addition, the first source gas and the second source gas are separately mixed without being mixed with each other, and the first source gas is passed through the cathode 14c of the fuel cell 21 and the second source gas is passed through the anode 14a of the fuel cell 21. Therefore, both the anode 14a and the cathode 14c can be reliably humidified.

  After sufficiently supplying the humidified raw material gas into the fuel cell 21, the switching valve and the shutoff valve are operated as follows in order to heat the fuel generator 23 (step S1011).

  The first cutoff valve 30 connected to the anode side outlet 21b, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the cathode side outlet 21d are closed.

  In this state, the first switching valve 29 is operated to connect the fuel gas supply pipe 61 to the anode exhaust pipe 47, while the fuel gas supply pipe 61 is blocked from the anode side inlet 21a. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. The flow rate of the raw material gas flowing through the fuel gas supply pipe 61 with respect to the flow rate of the raw material gas flowing through the raw material gas supply pipe 63 is controlled so as to guide the entire amount of the raw material gas flowing through the raw material gas supply pipe 63 to the fuel generator 23 by operating the diversion valve 55 Set the diversion ratio to 1.

  Thus, the gas sent from the fuel generator 23 passes through the first connecting pipe 64 by the switching operation of the first switching valve 29 (the direction in which the first check valve 41 allows the flow), and the anode exhaust pipe 47. Then, the second check valve 48 prevents the backflow in the direction of the anode outlet 21b, recirculates it to the combustion part of the fuel generator 23 and burns it in the combustion part to heat the fuel generator 23 ( Step S1012).

  Here, it is determined whether or not the temperature of the fuel generator 23 has risen to 700 ° C. or more (step S1013). If the temperature rise is insufficient (No in S1013), the heating operation in S1012 is continued, and 700 If the temperature reaches or exceeds ° C. (Yes in S1013), the process proceeds to the next step.

[Operation to confirm whether fuel cell generator can start power generation]
After the completion of the temperature increase of the fuel generator 23, whether or not the internal temperature of the fuel cell 21 and the conductivity of the electrolyte membrane 11 of the fuel cell 21 are confirmed to start the power generation of the fuel cell power generation apparatus 100. Determine whether.

  As a first confirmation operation, it is determined whether or not the internal temperature of the fuel cell 21 is equal to or higher than the operating temperature (70 ° C.) (step S1014). If the temperature rise is insufficient (No in S1014), the process proceeds to step S1003. When the temperature raising operation is performed again (step S1015) and the temperature is raised to 70 ° C. or higher (Yes in S1014), the process proceeds to the next step.

As a second confirmation operation, the conductivity of the electrolyte membrane 11 of the fuel cell 21 is measured to determine whether or not this conductivity: σ = 1.93 × 10 ⁻² Scm ⁻¹ or more (step S1016). If σ = 1.93 × 10 ⁻² Scm ⁻¹ (No in S1016), it is determined that the electrolyte membrane 11 is insufficiently humidified, and the operations of S1009 and S1010 are re-executed (step S1017). If it is 1.93 × 10 ⁻² Scm ⁻¹ or more (Yes in S1017), the process proceeds to the next step.

  The method for measuring the conductivity of the electrolyte membrane and the relationship between the conductivity of the electrolyte membrane and the relative humidity are the same as those described in the first embodiment.

  In this way, in addition to the determination based on the temperature of the fuel cell, the generation start timing of the fuel cell having the stop period and the power generation period is determined based on the conductivity of the electrolyte membrane of the fuel cell, so that the water retention state of the electrolyte membrane is accurately determined. Thus, the reliability of the determination of the power generation start time of the fuel cell power generator can be improved.

[Power generation operation of fuel cell power generator]
After the above confirmation operation reaches a predetermined value (specifically, the internal temperature of the fuel cell 21 is 70 ° C. or higher and the electrolyte membrane conductivity σ = 1.93 × 10 ⁻² Scm ⁻¹ or higher), the switching valve and The shut-off valve is operated as follows to generate power in the fuel cell 21 (steps S1018 and S1019).

  The first cutoff valve 30 connected to the anode side outlet 21b, the second cutoff valve 31 connected to the third switching valve 43, and the third cutoff valve 32 connected to the cathode side outlet 21d are all opened.

  In this state, the first switching valve 29 is operated to cut off the fuel gas supply pipe 61 from the anode exhaust pipe 47, while the fuel gas supply pipe 61 is communicated with the anode side inlet 21a. Further, the third switching valve 43 is operated to connect the cathode side inlet 21 c with the second shutoff valve 31, while the cathode side inlet 21 c is shut off from the source gas branch pipe 51. In addition, the raw material flowing through the fuel gas supply pipe 61 with respect to the flow rate of the raw material gas flowing through the raw material gas supply pipe 63 so as to guide the entire amount of the raw material gas flowing through the raw material gas supply pipe 63 to the fuel generator 23 by operating the flow dividing valve 55. Set the gas flow diversion ratio to 1.

  By the operation of the switching valve and the shutoff valve, the hydrogen gas-rich fuel gas sent from the fuel generator 23 through the fuel gas supply pipe 61 is introduced into the anode side inlet 21a of the fuel cell 21 and sent out from the anode side outlet 21b. The remaining fuel gas that has not been consumed by the anode 14 a is recirculated to the fuel generator 23 of the fuel cell 21 through the anode exhaust pipe 47. Further, humidified air (oxidant gas) is introduced from the humidifier 23 to the cathode side inlet 21c of the fuel cell 21 via the oxidant gas supply pipe 62, and is sent from the cathode side outlet 21d and is not consumed by the cathode 14c. The remaining oxidant gas is refluxed to the humidifier 24 of the fuel cell 21 via the cathode exhaust pipe 60.

  As a result, the fuel gas is supplied to the anode 14a, the oxidant gas is supplied to the cathode 14c, and hydrogen ions and electrons are generated inside the fuel cell 21, and are supplied to the circuit unit 25 via the output terminals 72a and 72c. The current can be taken out, and the generated voltage is monitored in the measuring unit 26.

  The effect of fuel cell performance stabilization brought about by the humidified raw material gas purging process described in the first to third embodiments was verified by the following characteristic evaluation of the fuel cell 21 (voltage evaluation of the MEA 17). In the characteristic evaluation of the fuel cell 21, the following materials are used as the catalyst material of the fuel cell power generator 100.

Zeolite is used as an example of the material of the desulfurization catalyst body, Ru / Al ₂ O ₃ is used as an example of the reforming catalyst body of the reforming part 23e, and Pt / CeZrOx (Pt = 2wt) as an example of the transformation catalyst body of the transformation part 23f. %, Ce: Zr = 1: 1, x = 3 or 4), and as an example of a CO removal catalyst body of the CO removal portion 23g, Pt / Al ₂ O ₃ and Ru / zeolite are used as a honeycomb and Pt / Al ₂ O ₃ (upstream side) and Ru / zeolite are used 1: 1.

  Further, the MEA 17 of the fuel cell 21 is made by the following manufacturing method.

  66 parts by weight of a catalyst body (50% by weight of Pt) obtained by supporting a Pt catalyst on Ketjen Black (Ketjen Black EC manufactured by Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder, Catalytic reaction by molding a mixture obtained by mixing 33 parts by weight (polymer dry weight) of perfluorocarbon sulfonate ionomer (5% by weight Nafion dispersion manufactured by Aldrich, USA) as a conductive material and binder Layers 12a and 12c (10 to 20 μm) are formed.

  Carbon powder acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 35 nm) is mixed with an aqueous dispersion of polytetrafluoroethylene (PTFE) (D1 manufactured by Daikin Kogyo Co., Ltd.) as a dry weight. A water repellent ink containing 20% by weight of PTFE is 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 layers 13a and 13c, and is heat-treated at 300 ° C. using a hot air dryer to form the gas diffusion layer 13a. , 13c (about 200 μm).

  The gas diffusion layers 13a and 13c and the catalytic reaction layers 12a and 12c thus manufactured are bonded to both surfaces of the polymer electrolyte membrane 11 (Nafion 112 electrolyte membrane manufactured by DuPont, USA) to complete the MEA 17.

  In the catalyst material system of the fuel cell power generation apparatus 100 described in the first to third embodiments together with a comparative example in which the fuel cell 21 is started (power generation) stopped up to 4000 times and the humidified raw material gas purge process is not performed. The changes in the MEA voltage in the example of the purging process of the humidified raw material gas are summarized in the following table. In FIG. 11, the horizontal axis indicates the number of times the fuel cell is started and stopped, and the vertical axis indicates the voltage of the MEA 17, and the state of the voltage change of the MEA 17 in the humidified raw material purge process example (third embodiment) and the comparative example is shown. It is shown.

  According to the purging process using the humidified raw material gas according to the first to third embodiments, local combustion or the like based on the repeated operation of power generation and stop can be prevented, so that the deterioration of the MEA 17 is suppressed and long-term without depending on the number of start / stops The voltage of the fuel cell 21 is stably maintained.

  On the other hand, in the comparative example, the catalyst deterioration of the MEA 17 progresses due to local combustion or the like, and a slight decrease in the voltage of the MEA 17 is observed after the number of start / stops is 1000 times or more. As a result of destruction (perforation), the voltage of the MEA 17 sharply decreases.

  The fuel cell power generator according to the present invention can stabilize the performance of the fuel cell even when the fuel cell is stopped and generated repeatedly, and is useful as, for example, a household fuel cell power generator.

1 is a cross-sectional view of a solid polymer electrolyte fuel cell equipped with an electrolyte assembly (MEA). It is the block diagram which showed the basic composition of the fuel cell power generation device. 1 is a block diagram showing a configuration of a fuel cell power generator according to Embodiment 1 of the present invention. It is a figure of the first half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 1 of this invention. It is a figure of the second half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 1 of this invention. It is the alternating current impedance profile figure of the fuel cell measured by varying the applied frequency with respect to the fuel cell in the range of 0.1 Hz to 1 kHz. It is a figure which shows the relationship between the relative humidity of an electrolyte membrane, and electrical conductivity. It is the block diagram which showed the structure of the fuel cell electric power generating apparatus which concerns on Embodiment 2 of this invention. It is a figure of the first half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 2 of this invention. It is a figure of the second half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 2 of this invention. It is the block diagram which showed the structure of the fuel cell electric power generating apparatus which concerns on Embodiment 3 of this invention. It is a figure of the first half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 3 of this invention. It is a figure of the second half part of the flowchart explaining the gas supply operation | movement which concerns on Embodiment 3 of this invention. It is a figure of the characteristic evaluation result of MEA voltage based on the number of times of starting and stopping.

Explanation of symbols

11 Electrolyte Membrane 12a Anode Catalytic Reaction Layer 12c Cathode Catalytic Reaction Layer 13a Anode Gas Diffusion Layer 13c Cathode Gas Diffusion Layer 14a Anode 14c Cathode 15a MEA Gasket 15c on Anode Side MEA Gasket 16a on Cathode Side Conductivity for Anode Separator plate 16c Conductive separator plate 17 for the cathode MEA
18a Fuel gas channel 18c Oxidant gas channel 19a Groove 19c formed in the conductive separator plate 16a Groove 20 formed in the conductive separator plate 16c Fuel cell 21 Fuel cell 22 Raw material gas supply means 22p Gas purifier 23 Fuel generator 23e Reformer 23f Transformer 23g CO removal unit 24 Humidification unit 25 Circuit unit 26 Measurement unit 27 Control unit 28 Blower 29 First switching valve 30 First shut-off valve 31 Second shut-off valve 32 Third Shut-off valve 33 Water removal part 34 Total heat exchange humidifier 35 Hot water humidifier 41 First check valve 42 Second switching valve 43 Third switching valve 44 Fourth switching valve 45 First circulation piping 46 Second Circulation pipe 47 anode exhaust pipe 48 second check valve 51 source gas branch pipe 52 fifth switching valve 53 second connection pipe 54 sixth switching valve 55 branching valve 60 Cathode exhaust pipe 61 Fuel gas supply pipe 62 Oxidant gas supply pipe 63 Raw material gas supply pipe 64 First connection pipe 70a Anode mass flow meter 70c Cathode mass flow meter 71 Temperature detection means 72a Anode output terminal 72c Cathode output terminal 73 Impedance measuring instrument 74 First water supply means 75 Second water supply means

Claims (15)

A fuel cell having a fuel gas flow path, and a raw material gas supply means for supplying a raw material gas,
In the power generation period of the fuel cell, the fuel cell is caused to generate power by supplying fuel gas generated from the source gas to the fuel gas flow path, and from the stop period in the fuel cell in which stop and power generation are alternately repeated During the transition period of the fuel cell until the power generation period, the fuel cell power generation that humidifies the source gas sent from the source gas supply means and exposes the inside of the fuel cell to the atmosphere of the humidified source gas apparatus.   2. The fuel cell power generator according to claim 1, wherein an electrolyte membrane inside the fuel cell is exposed to an atmosphere of the source gas by causing the source gas to flow through the fuel gas flow path.   The fuel cell power generator according to claim 2, wherein the raw material gas is humidified so that a dew point of the raw material gas can be maintained at a temperature equal to or higher than an operating temperature of the fuel cell.   4. The fuel cell supply unit according to claim 1, wherein the raw material gas supply unit includes a gas cleaning unit, and after the sulfur component in the raw material gas is removed by the gas cleaning unit, the interior of the fuel cell is exposed to the atmosphere of the raw material gas. The fuel cell power generator described in 1.   The fuel cell power generator according to claim 4, wherein the source gas is any one of methane gas, propane gas, butane gas, and ethane gas.   A fuel generator that generates fuel gas to be supplied to the fuel cell from the source gas and water vapor supplied from the source gas supply means, and the source gas sent from the source gas supply means during the transition period, 2. The fuel cell power generator according to claim 1, wherein when humidifying the inside of the fuel generator, the temperature of the fuel generator is maintained lower than a lower limit temperature at which the raw material gas is carbonized in the fuel generator.   The fuel cell power generator according to claim 6, wherein the temperature of the fuel generator is maintained at 300 ° C. or lower.   2. The fuel cell power generator according to claim 1, wherein an anode and a cathode sandwiching an electrolyte membrane are disposed inside the fuel cell, and the cathode is exposed to the source gas atmosphere after the anode is exposed to the source gas atmosphere.   The fuel generator which produces | generates the fuel gas supplied to the said fuel cell from the said raw material gas and water vapor | steam supplied from the said raw material gas supply means is provided, The said raw material gas is humidified inside the said fuel generator. Fuel cell power generator.   2. The fuel cell power generator according to claim 1, wherein an anode and a cathode sandwiching an electrolyte membrane are disposed inside the fuel cell, and the anode is exposed to the source gas atmosphere after the cathode is exposed to the source gas atmosphere.   11. The fuel cell power generator according to claim 10, further comprising a humidifier that humidifies an oxidant gas for power generation reaction with the fuel gas supplied to the cathode, and the source gas is humidified by the humidifier.   An anode and a cathode sandwiching an electrolyte membrane are disposed inside the fuel cell, the cathode is exposed to an atmosphere of the first source gas that diverts from the source gas, and the second that diverts the anode from the source gas The fuel cell power generator according to claim 1, wherein the fuel cell power generator is exposed to an atmosphere of a raw material gas.   A fuel generator for generating fuel gas to be supplied to the fuel cell from the source gas and water vapor supplied from the source gas supply means, and a humidifier for humidifying oxidant gas to be supplied to the cathode, The fuel cell power generator according to claim 12, wherein the source gas is humidified inside the humidifier, and the second source gas is humidified inside the fuel generator.   The fuel cell power generator according to claim 1, further comprising an electrolyte membrane inside the fuel cell, wherein the power generation period is started based on a conductivity of the electrolyte membrane.   The fuel cell power generator according to claim 14, wherein the power generation period is started based on conductivity of the electrolyte membrane corresponding to a predetermined relative humidity inside the fuel cell.

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