JP2006120375A - Fuel cell system and operation method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of detecting occurrence of cross-leak with a simple structure, performing an appropriate operation against the cross-leak, preventing lowering of performance of a fuel cell stack and release of hydrogen gas of high density, by detecting the occurrence of cross-leak depending on the hydrogen density in the air exhausted from the fuel stack. <P>SOLUTION: The fuel cell formed by interposing an electrolyte layer between a fuel electrode and an oxygen electrode comprises a fuel cell stack 20 laminated with separators interposed between them, on which air flow passages are formed along the oxygen electrode; a hydrogen density detecting device 23 detecting the density of the hydrogen in the air exhausted from the fuel cell stack 20; and a control device judging the occurrence of cross-leak at an electrolyte layer when the hydrogen density detected by the hydrogen density detecting device 23 is a prescribed value or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put into practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as buses and trucks. The fuel cell may be an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but a solid polymer type fuel cell is generally used.

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as fuel is supplied to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  In the polymer electrolyte fuel cell, since both sides of the polymer electrolyte membrane need to be kept wet, water is supplied to the fuel electrode side and the oxygen electrode side, respectively. In this case, moisture moves as proton-entrained water from the fuel electrode side toward the oxygen electrode side, and moves as back diffusion water from the oxygen electrode side toward the fuel electrode side.

By the way, if excessive water is retained from the oxygen electrode side to the fuel electrode side, sufficient supply of hydrogen and oxygen is hindered, so it is necessary to discharge excess water. Therefore, purging the water together with hydrogen gas while the vehicle is stopped is performed. Although hydrogen gas is sufficiently diluted in the diluter and then released into the atmosphere, a large amount of hydrogen gas will be sent to the diluter due to a failure of the hydrogen discharge device such as the on-off valve. There is. Therefore, a technique has been proposed in which the concentration of hydrogen gas discharged from the diluter is detected to detect a failure of the hydrogen discharge device (see, for example, Patent Document 1).
JP 2004-127750 A

  However, in the conventional fuel cell system, since the concentration of hydrogen gas discharged from the diluter for purging hydrogen gas is detected, the occurrence of cross leak cannot be detected. It was. In the case of a fuel cell, cross-mixing of hydrogen gas as fuel and air as oxidant (Cross Over) is caused by cracking of the solid polymer electrolyte membrane or deterioration of the differential pressure resistance characteristics of the solid polymer electrolyte membrane. ), That is, a cross leak may occur. When the cross leak occurs, hydrogen and air (oxygen) are mixed on the fuel electrode side, the electrode catalyst is deteriorated, the catalyst particles are eluted, and the performance of the fuel cell is lowered. Moreover, since hydrogen gas permeates | emits and discharges to the oxygen electrode side unused, a fuel consumption rate will deteriorate. Furthermore, safety problems arise when high-concentration hydrogen gas is released into the atmosphere.

  The present invention solves the problems of the conventional fuel cell system and detects the occurrence of cross leak based on the hydrogen concentration in the air exhausted from the fuel cell stack, thereby reducing the cross leak with a simple configuration. Occurrence can be detected early, proper operation against cross-leakage can be performed, performance degradation of the fuel cell stack can be prevented, and high-concentration hydrogen gas can be prevented from being released An object of the present invention is to provide a fuel cell system that can be operated and a method for operating the fuel cell system.

  Therefore, in the fuel cell system of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having an air channel formed along the oxygen electrode. A fuel cell stack; a hydrogen concentration detector for detecting a hydrogen concentration in the air discharged from the fuel cell stack; and if the hydrogen concentration detected by the hydrogen concentration detector exceeds a predetermined value, And a control device that determines that a leak has occurred.

  In another fuel cell system of the present invention, an exhaust manifold having one end connected to the outlet of the air flow path, and an exhaust manifold connected to the other end of the exhaust manifold and discharged from the fuel cell stack. And a condenser for collecting moisture, and the hydrogen concentration detector is disposed on the outlet side of the condenser.

  In still another fuel cell system of the present invention, when the control device determines that a cross leak has occurred in the electrolyte layer, the amount of air required to make the hydrogen concentration in the air less than a predetermined value. Is calculated, and the calculated amount of air is supplied.

  In still another fuel cell system of the present invention, when the controller determines that a cross leak has occurred in the electrolyte layer, the output relay of the fuel cell is turned off to supply hydrogen to the fuel electrode. Is shut off and a warning is output.

  In the operation method of the fuel cell system of the present invention, while supplying normal pressure air to the air flow path of the fuel cell stack mounted on the vehicle, supplying fuel gas to the fuel gas flow path of the fuel cell stack, Back diffusion water was recovered from the fuel gas discharged as an unreacted component and returned to the fuel gas flow path. When the operation of the fuel cell stack was stopped, the fuel gas was introduced into the recovery container and recovered. A method of operating a fuel cell system that discharges the reverse diffusion water, wherein a cross leak occurs in an electrolyte layer of the fuel cell stack when a hydrogen concentration in the air discharged from the fuel cell stack is a predetermined value or more. Judge.

  According to the present invention, in a fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is stacked with a separator having an air channel formed along the oxygen electrode. A fuel cell stack; a hydrogen concentration detector for detecting a hydrogen concentration in the air discharged from the fuel cell stack; and if the hydrogen concentration detected by the hydrogen concentration detector exceeds a predetermined value, And a control device that determines that a leak has occurred.

  In this case, it is possible to reliably detect the occurrence of the cross leak early with a simple configuration. Therefore, an appropriate operation of emergency stop of the fuel cell system can be quickly performed without increasing the cost of the fuel cell system. Accordingly, it is possible to prevent the electrode catalyst from deteriorating, so that the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated. Further, since hydrogen gas is prevented from passing through and discharged to the oxygen electrode side without being used, the fuel consumption rate of the fuel cell system does not deteriorate.

  In another fuel cell system, an exhaust manifold whose one end is connected to the outlet of the air flow path, and moisture in the air discharged from the fuel cell stack, which is connected to the other end of the exhaust manifold, are collected. And a hydrogen concentration detector is disposed on the outlet side of the condenser.

  In this case, since the hydrogen concentration in the air discharged from the fuel cell stack can be reliably detected with a simple configuration, the occurrence of a cross leak can be detected early and reliably.

  In yet another fuel cell system, when the controller determines that a cross leak has occurred in the electrolyte layer, it calculates the amount of air necessary to make the hydrogen concentration in the air less than a predetermined value. Supply a calculated amount of air.

  In this case, the hydrogen concentration discharged into the atmosphere can be sufficiently reduced, so that a safety problem does not occur.

  In yet another fuel cell system, when the control device determines that a cross leak has occurred in the electrolyte layer, the control device shuts off the supply of hydrogen to the fuel electrode by turning off the output relay of the fuel cell. , Output a warning.

  In this case, since the operation of the fuel cell is quickly stopped, the performance of the fuel cell stack is not deteriorated. In addition, the driver can accurately recognize that the operation of the fuel cell has been stopped due to the occurrence of the cross leak.

  According to the present invention, in the operation method of the fuel cell system, normal pressure air is supplied to the air flow path of the fuel cell stack mounted on the vehicle, and the fuel gas is supplied to the fuel gas flow path of the fuel cell stack. When the reverse diffusion water is recovered from the fuel gas discharged as an unreacted component and returned to the fuel gas flow path, and the operation of the fuel cell stack is stopped, the fuel gas is introduced into the recovery container. A method of operating a fuel cell system that discharges the recovered reverse diffusion water, wherein when the hydrogen concentration in the air discharged from the fuel cell stack is equal to or higher than a predetermined value, a cross leak occurs in the electrolyte layer of the fuel cell stack. Is determined to have occurred.

  In this case, it is possible to eliminate the discharge of hydrogen from the collection container into the atmosphere during normal operation of the vehicle, and it is possible to reliably detect the occurrence of a cross leak early. Therefore, an appropriate operation of emergency stop of the fuel cell system can be quickly performed without increasing the cost of the fuel cell system. Accordingly, it is possible to prevent the electrode catalyst from deteriorating, so that the catalyst particles are not eluted and the performance of the fuel cell stack is not deteriorated. Further, since hydrogen gas is prevented from passing through and discharged to the oxygen electrode side without being used, the fuel consumption rate of the fuel cell system does not deteriorate.

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

  FIG. 2 is a diagram showing the configuration of the fuel cell stack in the embodiment of the present invention, FIG. 3 is a diagram showing the configuration of the cell module of the fuel cell in the embodiment of the present invention, and FIG. 4 is in the embodiment of the present invention. It is a schematic cross section which shows the structure of the unit cell of a fuel cell.

  In FIG. 2, a fuel cell stack 20 as a fuel cell (FC) is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, and luggage carts. Here, the vehicle is equipped with a large number of auxiliary devices that consume electricity, such as lighting devices, radios, and power windows, which are used even when the vehicle is stopped. Since the output range is extremely wide, it is desirable to use the fuel cell stack 20 as a power source and a secondary battery as a power storage means (not shown) in combination.

  The fuel cell stack 20 is of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) using hydrogen gas as fuel gas, that is, anode gas, and oxygen or air as oxidant, that is, cathode gas. ) Type fuel cell. Here, the PEM fuel cell is generally a fuel cell in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane as an electrolyte layer that transmits ions such as protons. Are composed of a plurality of stacks connected in series.

  In the present embodiment, the fuel cell stack 20 includes a plurality of cell modules 10 as shown in FIG. In addition, the arrow in FIG. 2 has shown the flow of the hydrogen gas as fuel gas. As shown in FIG. 3, the cell module 10 electrically connects a unit cell (MEA) 10A as a fuel cell with the unit cells 10A and hydrogen introduced into the unit cell 10A. The separator 10B that separates the gas flow path and the air, and the unit cell 10A and the separator 10B are set as one set, and a plurality of sets are stacked in the thickness direction. In the cell module 10, the unit cells 10 </ b> A and the separators 10 </ b> B are stacked and stacked in multiple stages so that the unit cells 10 </ b> A are arranged with a predetermined gap (gap) therebetween.

  The unit cell 10A includes an air electrode 12 as an oxygen electrode provided on the solid polymer electrolyte membrane 11 side as an electrolyte layer and a fuel electrode 13 provided on the other side. The air electrode 12 includes a diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and a catalyst layer that is formed on the diffusion layer and supported in contact with the solid polymer electrolyte membrane 11. In addition, the air electrode side collector as a net-like current collector in which a large number of openings are formed that are in contact with the electrode diffusion layer on the air electrode 12 side of the unit cell 10A and transmit a mixed flow of air and water. 14 and a fuel electrode side collector 15 serving as a net-like conductor for contacting the electrode diffusion layer on the fuel electrode 13 side of the unit cell 10A and similarly leading out the current to the outside.

  And in unit cell 10A, as FIG. 4 shows, water moves. In FIG. 4, 48 is a fuel chamber as a fuel gas flow path, and 49 is an oxygen chamber as an air flow path. In this case, when a fuel gas, that is, hydrogen gas as an anode gas is supplied into the fuel chamber 48 of the fuel electrode side collector 15, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into proton-entrained water. Along with this, it passes through the solid polymer electrolyte membrane 11. Further, when the air electrode 12 is a cathode electrode and an oxidant, that is, air as a cathode gas is supplied into the oxygen chamber 49, oxygen in the air is combined with the hydrogen ions and electrons to generate water. Is done. Moisture permeates through the solid polymer electrolyte membrane 11 as reverse diffusion water and moves into the fuel chamber 48 of the fuel electrode side collector 15. Here, the reverse diffusion water means that the water generated in the oxygen chamber 49 diffuses into the solid polymer electrolyte membrane 11 and permeates through the solid polymer electrolyte membrane 11 in the direction opposite to the hydrogen ions. It penetrated up to 48.

  Next, the overall configuration of the fuel cell system will be described.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.

  In FIG. 1, a device for supplying hydrogen gas as a fuel gas and air as an oxidant to a fuel cell stack 20 is shown. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Thereby, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load of the vehicle and supply a necessary current. . In this case, the output impedance of the fuel cell stack 20 is extremely low and can be approximated to zero.

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the inlet of the fuel gas flow path of the fuel cell stack 20 through a second fuel supply pipe 33 as a fuel supply pipe connected to the first fuel supply pipe 21. The first fuel supply pipe 21 is provided with a fuel storage means on-off valve 24, a pressure sensor 27, a first fuel pressure adjustment valve 25a, a second fuel pressure adjustment valve 25b, and a fuel supply electromagnetic valve 26. The The second fuel supply pipe 33 is provided with a safety valve 33a and a pressure sensor 78 for detecting the pressure in the fuel gas passage. In this case, the fuel storage means 73 has a sufficiently large capacity and is capable of always supplying sufficiently high pressure hydrogen gas. In the example shown in FIG. 1, a plurality of, for example, three fuel storage means 73 are provided, and the first fuel supply pipe 21 is connected to each fuel storage means 73 at a portion connected thereto. It is branched and is merged on the way to become one. However, the number of the fuel storage means 73 may be singular, plural, or any number in the case of plural.

  The hydrogen gas discharged as an unreacted component from the outlet of the fuel gas flow path of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected with a fuel discharge line 30 for discharging water and the separated hydrogen gas. The fuel discharge line 30 is provided with a suction circulation pump 36 as a pump. Yes. A hydrogen circulation electromagnetic valve 34 is disposed in the fuel discharge line 30. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas discharged to the outside of the fuel cell stack 20 can be recovered, supplied to the fuel gas flow path of the fuel cell stack 20, and reused.

  Further, a startup fuel discharge conduit 56 is connected to the water recovery drain tank 60, and a hydrogen startup exhaust solenoid valve 62 is disposed in the startup fuel discharge pipeline 56, so that the fuel cell stack 20 is started up. The hydrogen gas discharged from the fuel gas channel can be discharged into the atmosphere. The outlet end of the starting fuel discharge line 56 is connected to the exhaust manifold 71. In addition, a hydrogen combustor may be provided in the startup fuel discharge line 56 as necessary. The hydrogen gas discharged by the hydrogen combustor can be combusted to form water, and then discharged into the atmosphere.

  Here, the first fuel pressure regulating valve 25a and the second fuel pressure regulating valve 25b are those of a butterfly valve, a regulator valve, a diaphragm type valve, a mass flow controller, a sequence valve, etc., but the first fuel pressure regulating valve Any type of hydrogen gas may be used as long as the pressure of the hydrogen gas flowing out from the outlets of 25a and the second fuel pressure regulating valve 25b can be adjusted to a preset pressure. The pressure adjustment may be performed manually, but is preferably performed by an actuator including an electric motor, a pulse motor, an electromagnet, or the like.

  The fuel supply solenoid valve 26, the hydrogen circulation solenoid valve 34, and the hydrogen activation exhaust solenoid valve 62 are so-called on-off types, and are operated by an actuator including an electric motor, a pulse motor, an electromagnet, and the like. The fuel storage means original opening / closing valve 24 is operated manually or automatically using an electromagnetic valve. Further, the suction circulation pump 36 may be of any type as long as it can forcibly discharge the reverse diffusion water together with the hydrogen gas and can bring the inside of the fuel gas passage into a negative pressure state. Good.

  On the other hand, air as an oxidant is supplied from an oxidant supply source 75 such as an air supply fan, an air cylinder, or an air tank to an air flow path of the fuel cell stack 20 through an oxidant supply line 77 and an intake manifold 74. Supplied. In this case, the pressure of the supplied air is a normal pressure of about atmospheric pressure. Note that oxygen can be used as the oxidizing agent instead of air. And the air discharged | emitted from an air flow path is discharged | emitted in air | atmosphere through the exhaust manifold 71 as a manifold, the condenser 72, the exit side exhaust manifold 22, and the exhaust port 22a.

  The oxidant supply pipe 77 is provided with a water supply nozzle 76 for spraying water and maintaining the air electrode (cathode electrode) 12 of the fuel cell stack 20 in a wet state. Further, the air electrode 12 and the fuel electrode 13 can be cooled by the sprayed water. Further, the condenser 72 disposed at the end of the exhaust manifold 71 is for condensing and removing moisture contained in the air discharged from the fuel cell stack 20, and is condensed by the condenser 72. The water thus collected is collected in the water tank 52 through the condensed water discharge pipe 79. A drainage pump 51 is disposed in the condensed water discharge conduit 79, and a level gauge (water level gauge) 52a is disposed in the water tank 52.

  The water in the water tank 52 is supplied to the water supply nozzle 76 through the water supply pipe 53. A water supply pump 54 and a water filter 55 are disposed in the water supply line 53. Here, the drainage pump 51 and the water supply pump 54 may be of any kind as long as they can suck and discharge water. The water filter 55 may be of any kind as long as it removes dust, impurities, etc. contained in water.

  Further, the outlet side exhaust manifold 22 connected to the outlet side of the condenser 72 is provided with a hydrogen concentration detector 23 for detecting the hydrogen concentration in the air at the outlet of the condenser 72. . If the hydrogen concentration detected by the hydrogen concentration detector 23 is equal to or greater than a predetermined value, it is determined that a cross leak has occurred in the fuel cell stack 20. The hydrogen concentration detector 23 may detect not only the hydrogen concentration in the air on the outlet side of the condenser 72 but also the hydrogen concentration in the air on the inlet side of the condenser 72. That is, the hydrogen concentration detector 23 can be disposed in the exhaust manifold 71.

  The secondary battery as the power storage means is a so-called battery (storage battery), and a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, and the like are common. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has an FC control ECU (Electronic Control Unit) (not shown) as control means. The control means includes arithmetic means such as a CPU and MPU, storage means such as a magnetic disk and a semiconductor memory, an input / output interface, and the like, and a fuel gas flow path of the fuel cell stack 20 from various sensors including a hydrogen concentration detector 23. And detecting the flow rate, temperature, output voltage, etc. of hydrogen, oxygen, air, etc. supplied to the air flow path, the oxidant supply source 75, the first fuel pressure adjustment valve 25a, the second fuel pressure adjustment valve 25b, The operation of the fuel supply solenoid valve 26, the hydrogen circulation solenoid valve 34, the suction circulation pump 36, the drainage pump 51, the feed water pump 54, the hydrogen start exhaust solenoid valve 62, and the like is controlled. Further, the FC control ECU cooperates with other sensors provided in the vehicle and an EV (Electric Vehicle) control ECU (not shown) as a vehicle control means to supply fuel and oxidant to the fuel cell stack 20. Centrally control the operation of all equipment supplied. When the FC control ECU determines that a cross leak has occurred in the fuel cell stack 20 based on the output of the hydrogen concentration detector 23, the FC control ECU stops the operation of the fuel cell stack 20 and reports that an abnormality has occurred. This is transmitted to the EV control ECU to output a warning to the driver of the vehicle.

  Next, the operation of the fuel cell system having the above configuration will be described. First, the operation in steady operation will be described.

  During steady operation in the fuel cell system of the present embodiment, after adjusting the pressure of hydrogen gas flowing out from the outlets of the first fuel pressure adjustment valve 25a and the second fuel pressure adjustment valve 25b to a predetermined constant pressure, The first fuel pressure adjustment valve 25a and the second fuel pressure adjustment valve 25b are not adjusted during operation of the fuel cell system, and are maintained as they are. Further, the oxidant supply source 75 operates so that air set in advance according to the output current of the fuel cell is supplied. In this case, the amount of air supplied is an amount sufficiently larger than the amount of air necessary for the output of the fuel cell stack 20 to be maximized. In the present embodiment, the pressure of the air supplied to the unit cell 10A of the fuel cell stack 20 is a normal pressure of about atmospheric pressure and does not need to be particularly pressurized. Therefore, the oxidant supply source 75, the oxidant supply pipe 77, the intake manifold 74, the exhaust manifold 71, the condenser 72, the outlet side exhaust manifold 22 and the like do not need to have pressure resistance, so that the configuration is simplified. Can do.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell 10A constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane 11 to flow the fuel gas. Then, the fuel electrode 13 side of the solid polymer electrolyte membrane 11 is humidified. Thereby, the fuel electrode 13 side of the solid polymer electrolyte membrane 11 is in a wet state, and hydrogen ions generated from hydrogen by an electrochemical reaction can move smoothly in the solid polymer electrolyte membrane 11.

  Further, the hydrogen gas as an unreacted component that is supplied to the fuel gas flow path and surplus is mixed with the back-diffused water that has permeated into the fuel gas flow path and becomes surplus, and a gas-liquid mixture Become. The hydrogen gas that has become the gas-liquid mixture is sucked by the suction circulation pump 36 and discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31 connected to the fuel cell stack 20. The gas-liquid mixture passes through the fuel discharge pipe 31 and is introduced into the water recovery drain tank 60. Then, by staying in the water recovery drain tank 60 having a relatively wide space, heavy moisture falls downward due to gravity, and the reverse diffusion water is separated from the hydrogen gas. The hydrogen gas in a state where the reverse diffusion water is separated and dried is discharged out of the water recovery drain tank 60 from the fuel discharge pipe 30.

  In steady operation, the hydrogen gas discharged from the fuel discharge line 30 passes through the open hydrogen circulation electromagnetic valve 34, is introduced into the second fuel supply line 33, and again. Then, it is supplied to the fuel gas flow path of the fuel cell stack 20 and reused.

  Next, an operation when a cross leak occurs in the fuel cell stack 20 will be described.

  FIG. 5 is a flowchart showing an operation when a cross leak occurs in the fuel cell system according to the embodiment of the present invention.

  First, the FC control ECU determines the hydrogen concentration in the air as the cathode gas discharged from the condenser 72 based on the output signal of the hydrogen concentration detector 23 that detects the hydrogen concentration in the air at the outlet of the condenser 72. Is measured (step S1). Subsequently, it is determined whether or not the measured hydrogen concentration is n [ppm], that is, a predetermined value or more (step S2). If the measured hydrogen concentration is not greater than or equal to the predetermined value, the process is terminated.

  If the measured hydrogen concentration is greater than or equal to a predetermined value, the FC control ECU determines that a cross leak has occurred in the fuel cell stack 20 and performs an emergency stop of the fuel cell system. Cross leak is a phenomenon in which hydrogen gas and air cross-mix when the solid polymer electrolyte membrane 11 in the unit cell 10A breaks or the differential pressure resistance characteristics of the solid polymer electrolyte membrane 11 decrease. When the cross leak occurs, hydrogen and oxygen in the air are mixed on the fuel electrode 13 side, the electrode catalyst is deteriorated, the catalyst particles are eluted, and the performance of the fuel cell stack 20 is deteriorated. Moreover, since hydrogen gas is permeate | transmitted and discharged | emitted by the air electrode 12 side in unused, the fuel consumption rate of a fuel cell system will deteriorate. In addition, high-concentration hydrogen gas may be released into the atmosphere.

  Therefore, when the FC control ECU determines that a cross leak has occurred in the fuel cell stack 20, the FC control ECU turns off the FC output relay in order to stop the fuel cell system in an emergency (step S3). That is, the relay switch disposed in the output electric circuit connected to the output terminal of the fuel cell stack 20 is turned off to shut off the output electric circuit. Therefore, power supply from the fuel cell stack 20 to the motor for driving the vehicle is interrupted. Subsequently, the FC control ECU turns off the hydrogen supply electromagnetic valve, that is, the fuel supply electromagnetic valve 26 (step S4). As a result, the supply of hydrogen gas to the fuel gas channel is interrupted. Further, the FC control ECU transmits an FC abnormality signal, that is, a signal indicating that an abnormality has occurred in the fuel cell stack 20 to the EV control ECU (step S5).

  Subsequently, the FC control ECU calculates the air amount based on the hydrogen concentration-air amount map (step S6). The hydrogen concentration-air amount map is a map prepared in advance and stored in the storage means. When the hydrogen concentration in the air discharged from the condenser 72 is equal to or higher than a predetermined value, the condenser 72 The hydrogen concentration in the air discharged from the air and the amount of air necessary to reduce the hydrogen concentration to such an extent that the hydrogen gas in the air discharged from the condenser 72 can be diluted and safely released into the atmosphere. It is a map which shows the relationship. Then, the FC control ECU activates the oxidant supply source 75 and supplies the air of the air amount calculated based on the hydrogen concentration-air amount map to the intake manifold 74, the fuel cell stack 20, the exhaust manifold 71, and the condenser. 72 to supply to the outlet side exhaust manifold 22. Thereby, the hydrogen concentration in the air discharged from the exhaust port 22a to the atmosphere becomes a sufficiently low value, and no safety problem occurs.

  Subsequently, the FC control ECU detects the concentration of hydrogen in the air at the outlet of the condenser 72, based on the output signal of the hydrogen concentration detector 23, and in the air as the cathode gas discharged from the condenser 72. The hydrogen concentration is measured (step S7). Then, it is determined whether or not the measured hydrogen concentration is n [ppm], that is, a predetermined value or more (step S8). In this case, the measurement of the hydrogen concentration is repeated until the measured hydrogen concentration becomes less than a predetermined value. When the measured hydrogen concentration becomes less than the predetermined value, the FC control ECU stops the FC all auxiliary equipment (step S9), stops the operation of all the auxiliary equipment of the fuel cell system, and ends the processing. To do. Thereby, the emergency stop of the fuel cell system is completed.

  On the other hand, when the EV control ECU receives a signal from the FC control ECU (step S10), the EV control ECU determines whether or not the received signal is an FC abnormality signal (step S11). If it is not an FC abnormality signal, the process is terminated as it is. If it is an FC abnormality signal, the EV control ECU outputs a warning to the vehicle driver (step S12). The warning may be, for example, blinking or displaying a warning light such as a red lamp arranged on a meter panel of the vehicle, or generating a warning sound from a sound output means such as a speaker. Also good. Thereby, the driver of the vehicle can recognize that the fuel cell system is urgently stopped due to an abnormality in the fuel cell stack 20, and can take appropriate measures.

  As described above, in the present embodiment, the fuel cell system has the hydrogen concentration detector 23 disposed in the outlet side exhaust manifold 22 connected to the outlet side of the condenser 72, and at the outlet of the condenser 72. It is designed to detect the hydrogen concentration in the air. When the detected hydrogen concentration is equal to or higher than a predetermined value, it is determined that a cross leak has occurred in the fuel cell stack 20, and the fuel cell system is urgently stopped. Therefore, deterioration of the electrode catalyst does not occur, and the catalyst particles are not eluted and the performance of the fuel cell stack 20 is not deteriorated. Further, since hydrogen gas is prevented from being permeated and discharged to the air electrode 12 side without being used, the fuel consumption rate of the fuel cell system does not deteriorate.

  Further, when it is determined that a cross leak has occurred in the fuel cell stack 20, the air amount calculated based on the hydrogen concentration-air amount map is supplied to the outlet side exhaust manifold 22, and the hydrogen mixed in the air is supplied. The gas is diluted. Therefore, the hydrogen concentration in the air discharged from the exhaust port 22a to the atmosphere is a sufficiently low value, and no safety problem occurs. In addition, since the concentration of the diluted hydrogen gas is confirmed by the hydrogen concentration detector 23, the hydrogen gas can be reliably diluted.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a figure which shows the structure of the fuel cell system in embodiment of this invention. It is a figure which shows the structure of the fuel cell stack in embodiment of this invention. It is a figure which shows the structure of the cell module of the fuel cell in embodiment of this invention. It is a schematic cross section which shows the structure of the unit cell of the fuel cell in embodiment of this invention. It is a flowchart which shows operation | movement when the cross leak of the fuel cell system in embodiment of this invention generate | occur | produced.

Explanation of symbols

10A Unit cell 10B Separator 11 Solid polymer electrolyte membrane 12 Air electrode 13 Fuel electrode 20 Fuel cell stack 23 Hydrogen concentration detector 48 Fuel chamber 49 Oxygen chamber 60 Water recovery drain tank 71 Exhaust manifold 72 Condenser

Claims (5)

A fuel cell stack in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and is stacked with a separator having an air flow path formed along the oxygen electrode;
A hydrogen concentration detector for detecting the hydrogen concentration in the air discharged from the fuel cell stack;
A fuel cell system comprising: a control device that determines that a cross leak has occurred in the electrolyte layer when the hydrogen concentration detected by the hydrogen concentration detector is equal to or greater than a predetermined value. An exhaust manifold having one end connected to an outlet of the air flow path;
A condenser connected to the other end of the exhaust manifold and recovering moisture in the air discharged from the fuel cell stack;
The fuel cell system according to claim 1, wherein the hydrogen concentration detector is disposed on an outlet side of the condenser.   When the controller determines that a cross leak has occurred in the electrolyte layer, the controller calculates an amount of air necessary to make the hydrogen concentration in the air less than a predetermined value, and supplies the calculated amount of air. Item 3. The fuel cell system according to Item 1 or 2.   4. The control device according to claim 1, wherein when the controller determines that a cross leak has occurred in the electrolyte layer, the output relay of the fuel cell is turned off to shut off the supply of hydrogen to the fuel electrode and output a warning. The fuel cell system according to any one of claims. Supply normal pressure air to the air flow path of the fuel cell stack mounted on the vehicle, supply fuel gas to the fuel gas flow path of the fuel cell stack, and back diffuse from the fuel gas discharged as unreacted components Operation of a fuel cell system that recovers water and returns it to the fuel gas flow path, and when the operation of the fuel cell stack is stopped, introduces fuel gas into a recovery container and discharges the back-diffused water recovered A method,
A method for operating a fuel cell system, comprising: determining that a cross leak has occurred in an electrolyte layer of the fuel cell stack when a hydrogen concentration in air discharged from the fuel cell stack is a predetermined value or more.

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