JP2014063664A - Method of starting fuel cell system - Google Patents

Abstract

It is possible to easily and reliably suppress discharge of a high-concentration fuel gas from a dilution device even when a valve opening failure occurs in a purge valve.
A starting method of a fuel cell system includes a dilution gas introduction step of driving an oxidant gas supply device to introduce an oxidant gas as a dilution gas into a dilution box, and the dilution gas introduction step is started. Then, the fuel gas supply device 16 is driven to supply the fuel gas to the fuel cell stack 12, and a purge valve failure detection step for detecting a failure of the purge valve 74 is provided. .
[Selection] Figure 1

Description

  The present invention relates to a fuel cell, an oxidant gas supply device, a fuel gas supply device, and a starting method of a fuel cell system including a dilution device.

  For example, a polymer electrolyte fuel cell is a power generation cell in which an electrolyte membrane / electrode structure (MEA) in which an anode electrode and a cathode electrode are arranged on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched by separators. It has. This fuel cell is usually used as, for example, an in-vehicle fuel cell stack by stacking a predetermined number of power generation cells.

  In the fuel cell stack, an oxidant gas supply device that supplies an oxidant gas to the cathode side of each fuel cell and a fuel gas supply device that supplies a fuel gas to the anode side of each fuel cell are connected.

  Here, the fuel gas supplied into the fuel cell stack is often discharged from the fuel cell stack as a fuel off-gas in which unused fuel gas remains. For this reason, the fuel gas supply device is usually provided with a circulation channel for returning the fuel off-gas discharged to the fuel gas outlet communication hole of the fuel cell stack to the fuel gas inlet communication hole of the fuel cell stack.

  Therefore, the unused fuel gas remaining in the fuel off-gas can be supplied again to the fuel cell stack as the fuel gas. As a result, the fuel gas can be used efficiently and economically.

  Incidentally, impurity gases such as nitrogen and moisture generated during power generation are accumulated in the circulation channel over time. For this reason, it is necessary to discharge this type of impurity to the outside of the circulation channel, and a purge valve is disposed in the circulation channel. Then, by opening and closing the purge valve, impurities remaining in the circulation flow path are discharged to the dilution device.

  At that time, an oxidant gas (for example, air) is introduced into the dilution apparatus as a dilution gas. Therefore, the fuel off gas is diluted with the oxidant gas, and the exhaust gas maintained at a predetermined hydrogen concentration or less is discharged to the outside.

  In this case, foreign substances eluted in the circulation channel are easily introduced into the purge valve. For this reason, there is a possibility that a failure such as the purge valve being in an open state and being unable to close (opening failure) may occur.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. In this fuel cell system, a fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a gas state upstream of the supply channel are adjusted and supplied downstream. A variable gas supply device, a first control device for driving and controlling the variable gas supply device, an offgas passage capable of discharging the fuel offgas discharged from the fuel cell to the outside via a discharge valve, and the discharge valve A second control device that controls the driving of the exhaust valve, and an abnormality detection device that detects occurrence of an abnormality of the discharge valve.

  The abnormality detection device is characterized by detecting a valve opening abnormality in which the discharge valve does not return from the valve opening state to the valve closing state using the gas supply command amount for the variable gas supply device. Thereby, since the valve opening abnormality of the discharge valve is detected using the gas supply command amount for the variable gas supply device, the valve opening abnormality can be detected without delay during operation.

JP 2008-112701 A

  In Patent Document 1 described above, a valve opening failure of a purge valve that is a discharge valve is monitored based on an increase in injection flow rate of an injector that is a variable gas supply device. At that time, the failure of the purge valve is detected based on the fluctuation of the outlet pressure of the injector. For this reason, when the outlet pressure of the injector is increased at the time of startup, if there is a valve opening failure in the purge valve, the fuel gas (hydrogen) may not be diluted to the target dilution concentration.

  The present invention solves this type of problem, and even when a purge valve has failed to open, it is possible to easily and reliably prevent high-concentration fuel gas from being discharged from the dilution device. An object of the present invention is to provide a starting method for a fuel cell system.

  The present invention provides a fuel cell having an electrolyte membrane / electrode structure in which a cathode electrode and an anode electrode are provided on both sides of an electrolyte membrane, an oxidant gas supply device for supplying an oxidant gas to the cathode side of the fuel cell, A fuel gas supply device that supplies fuel gas to the anode side of the fuel cell, a fuel off-gas that is the fuel gas discharged from the fuel cell is introduced through a purge valve, and the oxidant gas is used as a dilution gas. The present invention relates to a starting method of a fuel cell system including a dilution device to be introduced.

  In this starting method, the oxidant gas supply device is driven to introduce the oxidant gas into the dilution device. After the dilution gas introduction step is started, the fuel gas supply device is driven, A fuel gas supply step of supplying fuel gas to the fuel cell; and a purge valve failure detection step of detecting a failure of the purge valve.

  Further, in this starting method, it is preferable to supply the oxidant gas which is increased from the supply amount of the oxidant gas supplied during the normal operation until the purge valve failure detection step is completed.

  Furthermore, in this activation method, the oxidant gas supply device has a bypass flow path that bypasses the fuel cell and supplies the oxidant gas to the dilution device. In the dilution gas introduction step, the oxidant gas is The fuel cell is preferably supplied to the diluting device by passing through the flow path.

  Furthermore, in this activation method, the fuel cell system includes a power storage device, and the activation method includes a charge amount detection step of detecting a charge amount of the power storage device, and the detected charge amount is equal to or less than a specified amount. At this time, it is preferable to include a step of reducing the dilution gas target pressure value in the dilution gas introduction step and the fuel gas target pressure value in the fuel gas supply step.

  According to the present invention, when the fuel cell system is started, before the fuel gas pressure is increased by supplying the fuel gas, the introduction of the oxidant gas (diluted gas) to the diluting device is started. For this reason, even if the valve opening failure has occurred in the purge valve, the target dilution concentration of the fuel gas can be maintained well. Moreover, oxidant gas is introduced into the diluting device during the purge valve failure detection step. Therefore, even if the fuel gas is introduced into the diluting device due to the opening failure of the purge valve, the fuel gas can be effectively diluted.

  As a result, even if a valve opening failure occurs in the purge valve, it is possible to easily and reliably suppress the high-concentration fuel gas from being discharged from the dilution device.

1 is an explanatory diagram of a schematic configuration of a fuel cell system to which a startup method according to a first embodiment of the present invention is applied. It is a timing chart explaining the said starting method. It is a timing chart explaining the starting method which concerns on the 2nd Embodiment of this invention. It is a timing chart explaining the starting method which concerns on the 3rd Embodiment of this invention. FIG. 4 is a relationship diagram between an anode target pressure and an air supply flow rate. FIG. 6 is a relationship diagram between an anode pressure and a cathode target pressure. It is schematic structure explanatory drawing of the fuel cell system with which the starting method which concerns on the 4th Embodiment of this invention is applied. It is schematic structure explanatory drawing of the fuel cell system with which the starting method which concerns on the 5th Embodiment of this invention is applied.

  As shown in FIG. 1, the fuel cell system 10 to which the activation method according to the first embodiment of the present invention is applied is mounted on a fuel cell vehicle (not shown) such as a fuel cell electric vehicle, for example. A fuel cell system for a vehicle is configured.

  The fuel cell system 10 includes a fuel cell stack 12, an oxidant gas supply device 14 for supplying an oxidant gas to the fuel cell stack 12, a fuel gas supply device 16 for supplying a fuel gas to the fuel cell stack 12, And a controller 18 that controls the entire fuel cell system 10.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20. Each fuel cell 20 includes an electrolyte membrane / electrode structure (MEA) 28 in which a solid polymer electrolyte membrane 22 made of, for example, a fluorine electrolyte membrane or a hydrocarbon electrolyte membrane is sandwiched between a cathode electrode 24 and an anode electrode 26. Prepare.

  The cathode electrode 24 and the anode electrode 26 have a gas diffusion layer made of carbon paper or the like, and porous carbon particles carrying platinum alloy (or Ru or the like) on the surface are uniformly applied to the surface of the gas diffusion layer. And an electrode catalyst layer formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  In the fuel cell 20, the electrolyte membrane / electrode structure 28 is sandwiched between the cathode separator 30 and the anode separator 32. The cathode side separator 30 and the anode side separator 32 are comprised by a carbon separator or a metal separator, for example.

  An oxidant gas flow path 34 is provided between the cathode side separator 30 and the electrolyte membrane / electrode structure 28, and a fuel gas is provided between the anode side separator 32 and the electrolyte membrane / electrode structure 28. A flow path 36 is provided.

  In the fuel cell stack 12, end plates 37 a and 37 b are arranged at both ends in the stacking direction of the plurality of fuel cells 20. Although not shown, a tightening load is applied between the end plates 37a and 37b in the stacking direction via a tie rod or a casing including the end plates 37a and 37b.

  The end plate 37a communicates with each other in the stacking direction of the fuel cells 20, and supplies an oxidant gas, for example, an oxidant gas inlet manifold 38a for supplying an oxygen-containing gas (hereinafter also referred to as air), and the oxidant gas. Is provided with an oxidant gas outlet manifold 38b.

  The end plate 37b communicates with each other in the stacking direction of the fuel cells 20, and supplies a fuel gas, for example, a fuel gas inlet manifold 40a for supplying a hydrogen-containing gas (hereinafter also referred to as hydrogen gas), and the fuel gas is discharged. A fuel gas outlet manifold 40b is provided.

  The oxidant gas supply device 14 includes an air pump 50 that compresses and supplies air from the atmosphere, and the air pump 50 is disposed in the air supply flow path 52. The air supply channel 52 is provided with a humidifier 54 for exchanging moisture and heat between the supply gas (supply oxidant gas) and the exhaust gas (exhaust oxidant gas), and the air supply channel 52 communicates with the oxidant gas inlet manifold 38 a of the fuel cell stack 12.

  The oxidant gas supply device 14 includes an air off-gas passage 56 that communicates with the oxidant gas outlet manifold 38b. The air off gas passage 56 communicates with a humidification medium passage (not shown) of the humidifier 54, and the air off gas passage 56 is supplied from the air pump 50 to the fuel cell stack 12 through the air supply passage 52. A back pressure control valve 57 capable of adjusting the opening is provided for adjusting the pressure of the air. The air off-gas flow path 56 is connected to a dilution box (dilution device) 58.

  The fuel gas supply device 16 includes a hydrogen tank 60 that stores high-pressure hydrogen. The hydrogen tank 60 communicates with the fuel gas inlet manifold 40 a of the fuel cell stack 12 via a hydrogen supply flow path 62.

  The hydrogen supply channel 62 is provided with a pressure reducing valve 64, a shutoff valve 66, and an ejector 68. The ejector 68 supplies the hydrogen gas supplied from the hydrogen tank 60 to the fuel cell stack 12 through the hydrogen supply flow path 62, and also includes a fuel containing unused hydrogen gas that has not been used in the fuel cell stack 12. Off-gas is sucked from the circulation channel 70 and supplied again as fuel gas to the fuel cell stack 12.

  The fuel gas outlet manifold 40 b communicates with a fuel off gas passage 72 and a circulation passage 70 branches off from the fuel off gas passage 72. A purge valve 74 is connected to the fuel off gas passage 72 downstream of the circulation passage 70, and the fuel off gas passage 72 is connected to the dilution box 58.

  The dilution box 58 is formed with a space in which the fuel off-gas stays, and the air off-gas flow path 56 is disposed through the dilution box 58. An opening communicating with the dilution box 58 is formed in the air off-gas channel 56. As the air off gas flows through the air off gas flow path 56, the fuel off gas staying in the dilution box 58 is sucked, mixed with the air off gas, and diluted.

  The operation of the fuel cell system 10 configured as described above will be described below along with the timing chart shown in FIG. 2 in relation to the activation method according to the first embodiment.

  First, when the fuel cell system 10 is started, an ignition switch (not shown) or a fuel cell start switch is turned on. After the switch-on signal is output, the air supply command is turned on until the shut-off valve 66 opening command (hydrogen supply command) is turned on.

  For this reason, as shown in FIG. 1, in the oxidant gas supply device 14, air is sent to the air supply flow path 52 via the air pump 50. After passing through the humidifier 54, this air is supplied to the oxidant gas inlet manifold 38 a of the fuel cell stack 12.

  The air moves along each oxidant gas flow path 34 in the fuel cell stack 12 and then is discharged from the oxidant gas outlet manifold 38 b to the air off-gas flow path 56. The discharged air (air off gas) passes through the humidifier 54 and is then supplied to the dilution box 58 as a dilution gas. Accordingly, the dilution gas flows through the dilution box 58, and the shutoff valve 66 is opened in this state.

  In the fuel gas supply device 16, the hydrogen gas led out from the hydrogen tank 60 and decompressed by the pressure reducing valve 64 is supplied to the fuel gas inlet manifold 40 a of the fuel cell stack 12 through the ejector 68.

  This hydrogen gas moves along each fuel gas flow path 36 and is discharged from the fuel gas outlet manifold 40 b to the fuel off gas flow path 72 as fuel off gas. The fuel off-gas is sucked into the ejector 68 from the circulation channel 70 and supplied to the fuel cell stack 12 as new hydrogen gas.

  When the fuel cell system 10 is started, failure of the purge valve 74 is detected. Then, when the purge valve failure detection completion flag is turned on, failure detection of the purge valve 74 is completed.

  On the other hand, in the fuel cell stack 12, in each electrolyte membrane / electrode structure 28, the air flowing through the oxidant gas flow path 34 is supplied to the cathode electrode 24, and the hydrogen gas flowing through the fuel gas flow path 36 is anode It is supplied to the electrode 26.

  As a result, when the fuel cell stack 12 is connected to a load (not shown), such as a travel motor, the air supplied to the cathode electrode 24 and the hydrogen gas supplied to the anode electrode 26 are converted into the electrode catalyst layer. In this way, it is consumed by an electrochemical reaction to generate electricity.

  In this case, in the first embodiment, when the fuel cell system 10 is started, the oxidant gas supply device 14 is first driven, and the oxidant gas is introduced into the dilution box 58 as the dilution gas. Next, fuel gas is supplied to the fuel cell stack 12 from the fuel gas supply device 16.

  For this reason, even if a valve opening failure has occurred in the purge valve 74, the fuel off-gas introduced into the dilution box 58 is sufficiently diluted with the oxidant gas and is maintained at the target dilution concentration well. Moreover, oxidant gas is introduced into the dilution box 58 during the purge valve failure detection process. Therefore, even if the fuel offgas is introduced into the dilution box 58 due to the opening failure of the purge valve 74, the fuel offgas can be diluted well.

  As a result, even if a valve opening failure has occurred in the purge valve 74, it is possible to easily and reliably suppress the high-concentration fuel off-gas from being discharged from the dilution box 58.

  In the first embodiment, the supply command for the air that is the dilution gas is turned on before the opening command for the shutoff valve 66 is turned on. Instead, when a plurality of shut-off valves are provided, the air supply command is turned on after all the shut-off valves are opened after the ignition switch or the fuel cell start switch is turned on.

  FIG. 3 is a timing chart for explaining an activation method according to the second embodiment of the present invention.

  In the second embodiment, the air supply command is issued after the ignition switch or the fuel cell start switch is turned on until the opening command for the shutoff valve 66 is turned on. At that time, a failure detection map is set as the air supply control map, and the air supply amount is adjusted based on the failure detection map.

  Next, when the purge valve failure detection completion flag is turned on, the air supply control map is switched from the failure detection map to the normal power generation map, and adjusted to the air supply amount based on this normal power generation map. Here, the air supply amount set by the failure detection map is larger than the air supply amount set by the normal power generation map.

  More specifically, the air supply amount in the failure detection map is such that even if the fuel offgas is introduced into the dilution box 58 due to the opening failure of the purge valve 74 during the failure detection of the purge valve 74, the fuel offgas is reduced to the target dilution. The air supply amount that can be diluted to the concentration is set.

  Therefore, in the second embodiment, the same effect as in the first embodiment can be obtained, and it is possible to suppress the exhaust of the high concentration fuel off-gas from the dilution box 58 as much as possible. Become.

  FIG. 4 is a timing chart for explaining an activation method according to the third embodiment of the present invention.

  In the third embodiment, after the ignition switch or the fuel cell start switch is turned on, the air supply command is turned on, and supply of air as a dilution gas to the dilution box 58 is started. The air supply amount is maintained at a predetermined constant supply amount.

  Accordingly, when it is determined that the pressure increase rate of the anode internal pressure is slower than the predetermined value, a process for increasing the air supply amount is performed. This is because it is determined that a relatively large amount of fuel off-gas is introduced into the dilution box 58 due to the opening failure of the purge valve 74. For this reason, the hydrogen concentration can be lowered by increasing the amount of air supplied to the dilution box 58.

  Further, if the anode target pressure is large when the fuel cell system 10 is started up, the amount of fuel off-gas leakage due to the opening failure of the purge valve 74 increases. Therefore, as shown in FIG. 5, the higher the anode target pressure, the greater the air supply flow rate required at startup. The increase in the air supply flow rate is performed, for example, by increasing the operation amount of the air pump 50 or controlling the opening degree of the back pressure control valve 57.

  Furthermore, when the pressure on the cathode side is controlled, if the pressure difference between the cathode side and the anode side is large, the electrolyte membrane / electrode structure 28 of the fuel cell stack 12 may be damaged due to the pressure difference.

  Therefore, as shown in FIG. 6, it is possible to prevent damage to the electrolyte membrane / electrode structure 28 by setting the cathode target pressure in accordance with the anode pressure. The cathode target pressure has a predetermined pressure width S with respect to the anode pressure.

  FIG. 7 is an explanatory diagram of a schematic configuration of a fuel cell system 80 to which the activation method according to the fourth embodiment of the present invention is applied.

  The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the fuel cell system 80, the air supply passage 52 and the air off-gas passage 56 are provided with shutoff valves 82a and 82b, respectively, located between the humidifier 54 and the fuel cell stack 12.

  One end of a bypass channel 84 is connected to the air supply channel 52 on the upstream side of the humidifier 54, and the bypass channel is located on the downstream side of the humidifier 54 to the air off-gas channel 56. The other end of 84 is connected. A shutoff valve 86 is provided in the bypass channel 84.

  In the fourth embodiment, for example, the shutoff valves 86a and 82b are closed, and the shutoff valve 86 is opened by an air supply command in a state where the cathode system of the fuel cell stack 12 is sealed. As a result, the air supplied from the air pump 50 passes through the bypass flow path 84, that is, bypasses the fuel cell stack 12 and the humidifier 54 and is supplied to the dilution box 58.

  Thus, in the fourth embodiment, the dilution gas (air) is supplied to the dilution box 58 by bypassing the fuel cell stack 12. For this reason, pressure loss can be reduced, and air can be reliably sent with a small amount of air supply operation.

  Moreover, the dilution gas (air) bypasses the fuel cell stack 12 and the humidifier 54. Therefore, the pressure loss of the dilution gas is further reduced, and the effect that the dilution gas can be supplied efficiently and economically is obtained.

  In addition, although the humidifier 54 is used in 4th Embodiment, it can respond also to the structure which deleted this humidifier 54. FIG.

  FIG. 8 is an explanatory diagram of a schematic configuration of a fuel cell system 90 to which the startup method according to the fifth embodiment of the present invention is applied.

  The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell system 90 includes a power storage device 92 such as a high voltage battery, for example. The controller 18 detects the remaining amount (charge amount) of the power storage device 92. When the detected remaining amount is equal to or less than the specified amount, the anode target pressure is reduced to reduce the cathode target pressure in the dilution gas introduction step. The value is reduced.

  For this reason, in the fifth embodiment, it is possible to reduce the load on each device and to prevent the remaining amount of the power storage device 92 from being lost.

  In the present invention, various techniques other than the technique based on the increasing rate of the anode pressure can be adopted as a technique for detecting the valve opening failure of the purge valve 74.

DESCRIPTION OF SYMBOLS 10, 80, 90 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 18 ... Controller 20 ... Fuel cell 22 ... Solid polymer electrolyte membrane 24 ... Cathode electrode 26 ... Anode electrode 28 ... Electrolyte membrane / electrode structure 30 ... Cathode side separator 32 ... Anode side separator 34 ... Oxidant gas flow path 36 ... Fuel gas flow path 50 ... Air pump 52 ... Air supply flow path 54 ... Humidifier 56 ... Air off gas flow path 57 ... back pressure control valve 58 ... dilution box 60 ... hydrogen tank 62 ... hydrogen supply flow path 68 ... ejector 70 ... circulation flow path 72 ... fuel off-gas flow path 74 ... purge valves 82a, 82b, 86 ... shut-off valve 84 ... bypass flow path 92 ... Power storage device

Claims (4)

A fuel cell having an electrolyte membrane / electrode structure in which a cathode electrode and an anode electrode are provided on both sides of the electrolyte membrane;
An oxidant gas supply device for supplying an oxidant gas to the cathode side of the fuel cell;
A fuel gas supply device for supplying fuel gas to the anode side of the fuel cell;
A diluting device in which a fuel off gas, which is the fuel gas discharged from the fuel cell, is introduced through a purge valve, and the oxidant gas is introduced as a diluting gas;
A method for starting a fuel cell system comprising:
A dilution gas introduction step of driving the oxidant gas supply device to introduce the oxidant gas into the dilution device;
A fuel gas supply step of driving the fuel gas supply device and supplying the fuel gas to the fuel cell after the dilution gas introduction step is started;
A purge valve failure detection step of detecting a failure of the purge valve;
A starting method for a fuel cell system, comprising:   2. The start-up method according to claim 1, wherein the oxidant gas increased from the supply amount of the oxidant gas supplied during normal operation is supplied until the purge valve failure detection step is completed. A method for starting the fuel cell system. 3. The startup method according to claim 1, wherein the oxidant gas supply device includes a bypass flow path that bypasses the fuel cell and supplies the oxidant gas to the dilution device.
In the dilution gas introducing step, the oxidant gas bypasses the fuel cell by passing through the bypass flow path and is supplied to the dilution device. The start-up method according to any one of claims 1 to 3, wherein the fuel cell system includes a power storage device,
The activation method includes a charge amount detection step of detecting a charge amount of the power storage device;
A step of reducing the target gas pressure value in the dilution gas introduction step and the fuel gas target pressure value in the fuel gas supply step when the detected charge amount is not more than a specified amount;
A starting method for a fuel cell system, comprising:

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