JP2007299627A - Fuel cell and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to uniformly add an oxidizer or a fuel to an electrode, to make the oxidizer and the fuel react on the electrode surface, and to rapidly heat the electrode without deteriorating the electrode by forming a separator on a fuel electrode side or an oxygen electrode side in a porous body, and by forming a flow passage to add the oxidizer or the fuel to the interior of the separator. <P>SOLUTION: The separator on the fuel electrode side or the oxygen electrode side is formed in porous body, and an oxidizer adding flow passage to add the oxidizer to the fuel electrode or a fuel adding flow passage to add the fuel to the oxygen electrode is formed inside. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell and a fuel cell system.

  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, trucks, passenger carts, and luggage carts. Vehicle fuel cells are of the alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct type methanol (DMFC), and the like. However, a polymer electrolyte fuel cell (PEMFC) is common.

  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.

  By the way, in recent years, in this polymer electrolyte fuel cell, it is considered to use a high-temperature membrane as an electrolyte membrane that can be driven in a high-temperature region with higher power generation efficiency and excellent temperature durability.

In the fuel cell system using this high-temperature membrane, the temperature must be raised to a temperature (for example, 100 [° C.] or higher) necessary for obtaining good characteristics in a short time after startup. As a method for raising the temperature, a technique has been proposed in which hydrogen gas is mixed with air supplied to an air flow path formed along the oxygen electrode when the fuel cell is started (see, for example, Patent Document 1). In this case, the fuel cell can be heated by heat generated when hydrogen and oxygen react at the oxygen electrode, and the temperature can be rapidly increased to 100 [° C.] or higher.
JP 2004-22283 A

  However, in the conventional fuel cell system, since hydrogen gas is mixed in advance with the air supplied to the air flow path, the distribution of hydrogen gas in the air is uneven when viewed finely, Since the composition of the gas varies greatly in the direction of the flow path, the distribution of air and hydrogen gas is biased on the surface of the oxygen electrode, resulting in a potential difference in the plane of the electrode, leading to deterioration.

  The present invention solves the problems of the conventional fuel cell system, and forms a separator on the fuel electrode side or oxygen electrode side with a porous body, and adds an oxidant or fuel to the inside of the separator. By forming the path, the oxidant or fuel can be added uniformly to the electrode, the oxidant and fuel can be reacted uniformly on the electrode surface, and the electrode can be heated quickly without deterioration of the electrode. It is an object of the present invention to provide a fuel cell and a fuel cell system that can be used.

  Therefore, in the fuel cell of the present invention, a unit cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, a fuel flow path is formed outside the fuel electrode, and an oxidant flow path is formed outside the oxygen electrode. The separator on the fuel electrode side or the oxygen electrode side is formed of a porous body, and an oxidant addition flow path for adding an oxidant to the fuel electrode therein or A fuel addition passage for adding fuel to the oxygen electrode is formed.

  In another fuel cell of the present invention, the fuel electrode or the oxygen electrode further includes a startup temperature raising catalyst layer formed on the separator side surface.

  In the fuel cell system of the present invention, a unit cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, a fuel flow path is formed outside the fuel electrode, and an oxidant flow path is formed outside the oxygen electrode. The separator on the fuel electrode side or the oxygen electrode side is formed of a porous body, and an oxidant addition flow channel for adding an oxidant to the fuel electrode or the oxygen electrode is formed inside the separator. A fuel cell in which a fuel addition flow path for adding fuel is formed; fuel supply means for supplying fuel to the fuel flow path; oxidant supply means for supplying oxidant to the oxidant flow path; An adding means for supplying an oxidant to the oxidant addition flow path or a fuel to the fuel addition flow path, and an oxidant or fuel to be supplied to the oxidant addition flow path or the fuel addition flow path when the fuel cell is started. Control means for controlling.

  In another fuel cell system of the present invention, the control unit further controls to supply the oxidant or fuel to the oxidant addition channel or the fuel addition channel in a fixed amount.

  In still another fuel cell system of the present invention, the control means controls to supply an amount of oxidant or fuel calculated from the amount of fuel necessary for raising the temperature to a desired temperature.

  In still another fuel cell system of the present invention, the control means further detects the temperature of the fuel cell and, based on the temperature, an oxidation supplied to the oxidant addition channel or the fuel addition channel. Control the amount of agent or fuel.

  In still another fuel cell system of the present invention, the control means further includes a control unit configured so that an amount of oxidant or fuel supplied to the oxidant addition channel or the fuel addition channel is optimized. The change in heat capacity due to the amount of moisture remaining in the water is corrected.

  According to the present invention, in a fuel cell, a unit cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, a fuel flow path is formed outside the fuel electrode, and an oxidant flow path is formed outside the oxygen electrode. The separator on the fuel electrode side or the oxygen electrode side is formed of a porous body, and an oxidant addition flow path for adding an oxidant to the fuel electrode therein or A fuel addition passage for adding fuel to the oxygen electrode is formed.

  In this case, when the fuel cell is started, air and hydrogen gas are uniformly distributed on the surface of the fuel electrode or the oxygen electrode, and the oxidant or fuel can be uniformly added to the fuel electrode or the oxygen electrode. Therefore, the oxidant and the fuel can be uniformly reacted on the surface of the fuel electrode or the oxygen electrode, and no potential difference is generated in the surface of the fuel electrode or the oxygen electrode. Heating can be performed quickly, and the temperature of the fuel cell can be raised in a short time.

  In another fuel cell, the fuel electrode or the oxygen electrode further includes a startup temperature raising catalyst layer formed on the separator side surface.

  In this case, the catalyst layers provided on both sides of the electrolyte layer can avoid damage due to rapid heat generation due to the combustion reaction between the oxidant added at the start of the fuel cell and the fuel.

  In the fuel cell system, a unit cell having an electrolyte layer sandwiched between a fuel electrode and an oxygen electrode, a separator that forms a fuel flow path outside the fuel electrode and an oxidant flow path outside the oxygen electrode; The fuel electrode side or oxygen electrode side separator is formed of a porous body, and an oxidant addition passage for adding an oxidant to the fuel electrode therein or a fuel for adding fuel to the oxygen electrode A fuel cell in which an addition channel is formed; a fuel supply unit that supplies fuel to the fuel channel; an oxidant supply unit that supplies an oxidant to the oxidant channel; and an oxidant addition channel An addition means for supplying an oxidant or fuel to the fuel addition flow path; and a control means for controlling the oxidant or fuel supplied to the oxidant addition flow path or the fuel addition flow path when the fuel cell is started. Have

  In this case, the oxidant or fuel can be uniformly added to the fuel electrode or the oxygen electrode when the fuel cell is started. Therefore, the oxidant and the fuel can be uniformly reacted on the surface of the fuel electrode or the oxygen electrode, the fuel electrode or the oxygen electrode can be rapidly heated without deterioration of the fuel electrode or the oxygen electrode, The temperature of the fuel cell can be raised in a short time.

  In another fuel cell system, the control unit further controls to supply the oxidant or fuel to the oxidant addition flow path or the fuel addition flow path in a fixed amount.

  In this case, a predetermined amount of oxidant or fuel necessary for raising the temperature of the fuel cell can be appropriately supplied to the fuel electrode or the oxygen electrode.

  In still another fuel cell system, the control means further detects the temperature of the fuel cell, and based on the temperature, the oxidant or fuel supplied to the oxidant addition channel or the fuel addition channel. The amount of control.

  In this case, an appropriate amount of oxidant or fuel can be supplied to the fuel electrode or the oxygen electrode depending on the temperature of the fuel cell.

  In still another fuel cell system, the control means further controls the amount of oxidant or fuel supplied to the oxidant addition channel or the fuel addition channel to be optimum.

  In this case, an oxidant or fuel in an amount optimal for raising the temperature of the fuel cell can be supplied to the fuel electrode or the oxygen electrode.

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

  FIG. 1 is a schematic cross-sectional view showing a configuration of a unit cell of a fuel cell according to an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of a fuel cell system according to an embodiment of the present invention. FIG. 1 (a) shows a state during normal operation, and FIG. 1 (b) shows a state during start-up temperature rise.

  In the figure, reference numeral 20 denotes a fuel cell stack, which 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 a fuel cell stack 20 as a power source in combination with power storage means such as a secondary battery and a capacitor (not shown).

  The fuel cell stack 20 includes a high temperature membrane, a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell using hydrogen gas as a fuel gas, that is, an anode gas, and oxygen or air as an oxidant, that is, a cathode gas, Alternatively, it is called a PEM (Proton Exchange Membrane) type fuel cell. Here, the PEM type fuel cell generally includes a plurality of cells (Fuel Cells) in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane 11 as an electrolyte layer that transmits ions such as protons. It consists of a stack connected in series.

  In the present embodiment, the fuel cell stack 20 has a plurality of cell modules as fuel cells (not shown). The cell module electrically connects the unit cells (MEA) 10 to the unit cells 10 and separates the flow path of hydrogen gas introduced into the unit cells 10 from the flow path of air. The separator is a set, and a plurality of sets are stacked in the thickness direction. In the cell module, the unit cells 10 and the separators are stacked in multiple stages so that the unit cells 10 are arranged with a predetermined gap.

  The high temperature membrane is a solid polymer electrolyte membrane 11 having a high proton conductivity when the atmosphere is high temperature and low humidity. Specifically, materials used as high-temperature membranes are cation exchange membranes such as fluorine-containing membranes, hydrocarbon-based membranes, or synthetic membranes thereof, and have a characteristic structure that exhibits high proton conductivity at low humidity. Consists of. The characteristic of high proton conductivity at low humidity is, for example, a material in which water is sufficiently retained than a general solid polymer electrolyte membrane, or a substance capable of proton conduction without water. It is only necessary to add a material such as a fluorine-containing membrane perfluoro-based membrane having a high sulfonic acid group concentration (low EW value). A hydrocarbon-based sulfonated polyimide membrane has a molecular structure. Any substance that retains water may be used. Specific proton conductivity is such that the temperature is in the range of 50 to 140 [° C.] and the humidity is in the range of 0 to 50 [%]. The proton conductivity is better than 0.1 [S / cm] in an atmosphere of [%] or more), for example, in an atmosphere of a temperature of 120 [° C.] and a humidity of 20 [%]. The proton conductivity is preferably 0.1 [S / cm] or more. In the present embodiment, it is assumed that the solid polymer electrolyte membrane 11 as the electrolyte layer is preferably used when the temperature of the unit cell 10 is in the range of 100 to 200 [° C.].

  As shown in FIG. 1, the unit cell 10 includes an air electrode 12 as an oxygen electrode that is an electrode provided on the solid polymer electrolyte membrane 11 side and a fuel electrode 13 that is an electrode provided on the other side. It consists of and. 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 separator 14 in which the air flow path 16 as a large number of openings through which the air as the oxidizer flows and in contact with the electrode diffusion layer on the air electrode 12 side of the unit cell 10 is formed; A fuel electrode side separator 15 in which a hydrogen flow path 17 as a large number of openings through which hydrogen gas as a fuel gas flows is formed in contact with the electrode diffusion layer on the fuel electrode 13 side of the unit cell. Have.

  In the unit cell 10, water moves. In this case, the fuel gas, that is, the hydrogen gas as the anode gas is supplied from the fuel storage means 73 as a hydrogen gas storage body such as a hydrogen gas cylinder and a hydrogen storage alloy storage device as shown in FIG. When supplied into the flow path 17, hydrogen is decomposed into hydrogen ions (protons) and electrons, and as shown in FIG. 1 (a), the hydrogen ions are accompanied by proton-entrained water, and the solid polymer electrolyte membrane 11 is To Penetrate. Further, the air electrode 12 is used as a cathode electrode, and an oxidant, that is, air as cathode gas is supplied into the air flow path 16 of the air electrode side separator 14 from an oxidant supply source such as an air supply fan or an oxygen cylinder (not shown). Then, oxygen in the air is combined with the hydrogen ions and electrons to generate water. Moisture permeates through the solid polymer electrolyte membrane 11 as reverse diffusion water and moves into the hydrogen flow path 17 of the fuel electrode side separator 15. Here, the reverse diffusion water means that water generated in the air flow path 16 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 has penetrated to the flow path 17.

  FIG. 1 shows an apparatus for supplying hydrogen gas as a fuel gas to the fuel cell stack 20, that is, a fuel supply means for supplying fuel to the fuel electrode 13, and an apparatus for supplying air as an oxidant, that is, an air electrode. 12 shows an oxidant supply means for supplying an oxidant to 12. 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. .

  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 hydrogen flow path 17 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 pressure sensor 27, a fuel pressure adjustment valve 25, and a hydrogen supply valve 26 as a fuel supply electromagnetic valve. In addition, a hydrogen high-pressure supply valve 29 as a bypass valve is disposed in a bypass line that bypasses the fuel pressure adjustment valve 25. Further, a safety valve 33 a is disposed in the second fuel supply pipe 33. The number of the pressure sensors 27, the fuel pressure adjusting valves 25, and the hydrogen supply valves 26 can be set arbitrarily. The fuel storage means 73 has a sufficiently large capacity and always has a capability of supplying hydrogen gas at a sufficiently high pressure.

  The hydrogen gas discharged as an unreacted component from the outlet of the hydrogen flow path 17 of the fuel cell stack 20 is discharged out of the fuel cell stack 20 through the first fuel discharge pipe 31. The first fuel discharge pipe 31 is provided with a water recovery drain tank 60 as a recovery container. The water recovery drain tank 60 is connected to a second fuel discharge pipe 30 for discharging hydrogen gas separated from water, and a suction circulation pump 36 as a pump is arranged in the second fuel discharge pipe 30. It is installed. Further, a hydrogen circulation electromagnetic valve 34 is disposed in the second fuel discharge pipe 30. The end of the second 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 out of the fuel cell stack 20 can be recovered, supplied to the hydrogen flow path 17 of the fuel cell stack 20, and reused.

  Further, a third fuel discharge pipe 56 is connected to the water recovery drain tank 60, and a hydrogen exhaust electromagnetic valve 62 is disposed in the third fuel discharge pipe 56, so that hydrogen is discharged when the fuel cell stack 20 is started. The hydrogen electrode chamber gas discharged from the flow path 17 can be completely replaced with hydrogen. The outlet end of the third fuel discharge pipe 56 is connected to the exhaust manifold 71 to dilute the discharged hydrogen with air.

  Further, a fourth fuel discharge line 56 a having the other end connected to the third fuel discharge line 56 is provided between the suction circulation pump 36 and the hydrogen circulation electromagnetic valve 34 in the second fuel discharge line 30. It is connected. The fourth fuel discharge pipe 56a is provided with a reduced-pressure hydrogen discharge valve 62a that is opened when the pressure in the fuel cell stack 20 is reduced. The second fuel discharge conduit 30 is connected to an outside air introduction electromagnetic valve 35 and an air filter 37 so that outside air can be introduced when the fuel cell stack 20 is stopped.

  Here, the fuel pressure adjusting valve 25 is a butterfly valve, a regulator valve, a diaphragm valve, a mass flow controller, a sequence valve, or the like. The pressure of the hydrogen gas flowing out from the outlet of the fuel pressure adjusting valve 25 is set in advance. Any type can be used as long as it can be adjusted to the set 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 hydrogen supply valve 26, the hydrogen high pressure supply valve 29, the hydrogen circulation solenoid valve 34, the hydrogen exhaust solenoid valve 62, the decompression hydrogen discharge valve 62a, and the outside air introduction solenoid valve 35 are so-called ON-OFF types. It is actuated by an actuator comprising an electric motor, a pulse motor, an electromagnet or the like. The suction circulation pump 36 may be of any type as long as it can forcibly discharge the back-diffusion water together with the hydrogen gas to bring the inside of the hydrogen passage 17 into a negative pressure state. Good.

  On the other hand, air as an oxidant is supplied from an oxidant supply source such as an air supply fan and an oxygen cylinder (not shown) through the air supply line 77 and the intake manifold 74, that is, the oxygen chamber of the fuel cell stack 20, that is, the air flow. Is supplied to the path 16. 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 the air flow path 16 is discharged | emitted in air | atmosphere through the exhaust manifold 71 as a manifold. The exhaust manifold 71 is provided with a stack exhaust temperature detector 23 for detecting the temperature of air immediately after being discharged from the fuel cell stack 20. Further, the fuel cell stack 20 is provided with a voltmeter 59 for measuring the fuel cell voltage. The air supply pipe 77 is supplied with water sprayed into the air supplied to the air flow path 16 as necessary, and the air electrode as the oxygen electrode of the fuel cell stack 20 is in a wet state. A water supply nozzle can be provided to maintain the water supply.

  The fuel cell system has a fuel cell temperature control system for adjusting the temperature of the fuel cell stack 20. The fuel cell temperature control system is a system that adjusts the temperature of the fuel cell stack 20 with a circulating temperature adjusting medium, that is, a temperature adjusting medium, in the same manner as a cooling system for a general vehicle internal combustion engine or the like. Here, reference numeral 54 denotes a radiator as a radiator disposed in a temperature adjustment medium pipe 51 as a pipe through which the temperature adjustment medium flows, and heat exchange is performed between the temperature adjustment medium and the outside air. The heat of the conditioning medium is radiated to the outside air to cool the temperature adjustment medium. The radiator 54 may include a cooling fan driven by a motor (not shown). In this case, when the temperature of the temperature control medium becomes high, the ability to cool the temperature control medium can be enhanced by operating the cooling fan as necessary. In addition, although the said temperature control medium is liquids, such as water and oil, what kind of medium may be sufficient.

  The temperature control medium pipe 51 is provided with a circulation pump 53 for circulating the temperature control medium and a reservoir tank 52 for storing the temperature control medium. The circulation pump 53 is driven by a motor (not shown).

  In the unit cell 10, as shown in FIG. 1, a temperature control medium flow path 19 is formed in the fuel electrode side separator 15, and the temperature control medium supplied to the fuel cell stack 20 is the temperature control medium. The temperature of each unit cell 10 of the fuel cell stack 20 is adjusted by flowing through the medium adjustment channel 19.

  In the present embodiment, in order to quickly raise the temperature of the fuel cell to a predetermined temperature, for example, 100 [° C.] at the time of startup, hydrogen gas is added to the air electrode 12 to react with oxygen in the air. , Is supposed to generate heat. Therefore, a plurality of hydrogen addition passages 18 as fuel addition passages are formed in the air electrode side separator 14, and the air electrode side separator 14 is formed of a porous body. Then, when hydrogen gas is supplied to the hydrogen addition flow path 18 at the time of starting the fuel cell, the hydrogen gas passes through minute holes (holes) continuous with each other provided in the air electrode side separator 14 made of a porous material, and the air electrode. 12 reaches the separator side surface (the right side surface in FIG. 1B) and reacts with oxygen in the air at the electrode catalyst layer or the start-up temperature raising catalyst layer to generate heat of reaction.

  Here, the porous body is made of a material such as ceramic or a foam metal having a continuous pore structure (Metal Foam), for example, as long as it has pores through which hydrogen gas can pass. It may be made of various types of materials. Although not shown, the fuel electrode side separator 15 for the adjacent unit cell 10 is applied to the surface of the air electrode side separator 14 opposite to the air electrode 12 (on the right side in FIG. 1B). Touching. The fuel electrode side separator 15 is formed of a normal material that does not have a hole and cannot pass gas. Therefore, even if the air electrode side separator 14 is formed of a porous body, the air supplied to the air electrode 12 or the added hydrogen gas does not flow into the adjacent unit cells 10.

  And since the air electrode side separator 14 is formed from a porous body, the hydrogen gas is passed from the hydrogen addition channel 18 to the air electrode side separator 14 itself only by flowing hydrogen gas through the hydrogen addition channel 18. It diffuses through the micro holes which are provided with each other and is automatically supplied to the air electrode 12. In this case, since hydrogen gas is diffused by passing through the inside of the air electrode side separator 14 formed of a porous body, the hydrogen gas is uniformly supplied to the surface of the air electrode 12, and on the surface of the air electrode 12. There is no bias in the distribution of air and hydrogen gas.

  Further, it is desirable to provide a startup temperature raising catalyst layer on the separator 12 side of the air electrode 12. The start-up temperature raising catalyst layer may be of any kind as long as it contains a catalyst having a function of promoting the reaction between hydrogen and oxygen, that is, the combustion of hydrogen, such as platinum. Good. Thereby, it can prevent that the catalyst provided in the both sides of the solid polymer electrolyte membrane 11 deteriorates by combustion of the hydrogen gas added at the time of starting of a fuel cell. The air electrode side separator 14 may be provided with a startup temperature raising catalyst. For example, by forming the air electrode side separator 14 with a porous body made of carbon coated with platinum or the like, the air electrode side separator 14 having a startup temperature raising catalyst can be obtained.

  One end of a temperature raising pipe 78 is connected between the fuel pressure regulating valve 25 and the hydrogen supply valve 26 in the first fuel supply pipe 21. The other end of the temperature raising pipe line 78 is connected to the fuel cell stack 20 and communicated with the hydrogenation flow path 18. In addition, a temperature rising bypass valve 57 and a check valve 58 are disposed in the temperature rising pipeline 78. Then, when the fuel cell stack 20 is started, the temperature increase bypass valve 57 is opened, whereby the hydrogen gas from the fuel storage means 73 can be circulated through the hydrogen addition flow path 18. That is, the fuel storage means 73, the temperature raising pipe line 78, the temperature raising bypass valve 57, etc. function as an adding means for supplying fuel to the hydrogen addition flow path 18.

  In the present embodiment, the fuel cell system has an FC controller (not shown) as control means. The FC controller 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 is supplied from various sensors to the fuel gas flow path and the air flow path of the fuel cell stack 20. The flow rate of hydrogen, oxygen, air, etc., temperature, output voltage, etc. are detected, and the fuel pressure regulating valve 25, hydrogen supply valve 26, hydrogen high pressure supply valve 29, hydrogen circulation solenoid valve 34, hydrogen exhaust solenoid valve 62, The operation of various valves such as the decompression hydrogen discharge valve 62a, the outside air introduction electromagnetic valve 35, the temperature raising bypass valve 57, and the various motors for driving the suction circulation pump 36, the circulation pump 53, and the like is controlled.

  In order to quickly raise the temperature of the fuel cell to a predetermined temperature at the time of startup, air can be added to the fuel electrode 13 to react oxygen in the air with hydrogen gas to generate heat. In this case, a plurality of air addition passages as oxidant addition passages are formed in the fuel electrode side separator 15, and the fuel electrode side separator 15 is formed of a porous body. Then, when air is supplied to the air addition passage at the time of starting the fuel cell, the air passes through the minute holes that are continuous in the fuel electrode side separator 15 itself made of a porous body, and the separator side surface of the fuel electrode 13 ( 1 (b), and reacts with hydrogen gas at the electrode catalyst layer or the start-up temperature raising catalyst layer to generate heat of reaction. Further, the hydrogen addition flow path 18 is omitted, and the air electrode side separator 14 is formed of a normal material that does not have a hole and cannot pass gas. Therefore, even if the fuel electrode side separator 15 is formed of a porous body, the hydrogen gas supplied to the fuel electrode 13 or the added air does not flow into the adjacent unit cell 10.

  Then, as in the case of adding hydrogen gas to the air electrode 12, the air is passed through the air addition flow path, and the air is minutely connected to the fuel electrode side separator 15 itself from the air addition flow path. It diffuses through the hole and is automatically supplied to the fuel electrode 13. In this case, since air is diffused by passing through the inside of the fuel electrode side separator 15 formed of a porous body, the air is uniformly supplied to the surface of the fuel electrode 13, and on the surface of the fuel electrode 13, There is no bias in the distribution of air and hydrogen gas.

  Similarly to the case where hydrogen gas is added to the air electrode 12, it is desirable to provide a startup temperature raising catalyst layer on the separator side surface of the fuel electrode 13. Furthermore, a startup temperature raising catalyst may be provided in the fuel electrode side separator 15.

  Further, the temperature raising pipe 78 is omitted, and a temperature raising air pipe for circulating the air supplied from the oxidant supply source to the air addition flow path is provided. The temperature raising air pipe is provided with a temperature raising air adjusting valve, a check valve and the like to control the air supplied to the air addition flow path.

  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 this embodiment, after adjusting the pressure of the hydrogen gas flowing out from the outlet of the fuel pressure adjustment valve 25 to a predetermined constant pressure, the fuel pressure adjustment valve 25 is used in the fuel cell system. No adjustment is made during operation, and the state is maintained as it is. In addition, an oxidant supply source such as an air supply fan 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.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell 10 constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane 11 to pass through the hydrogen flow path. 17 and 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 surplus unreacted hydrogen gas supplied to the hydrogen channel 17 is mixed with the back-diffused water that has permeated into the hydrogen channel 17 and surplus, 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 first fuel discharge pipe 31 connected to the fuel cell stack 20. The gas-liquid mixture passes through the first 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 due to gravity, and reverse diffusion water is separated from hydrogen gas. The hydrogen gas in a state where the reverse diffusion water is separated and dried is discharged from the second fuel discharge pipe 30 to the outside of the water recovery drain tank 60.

  In steady operation, the hydrogen gas discharged from the second fuel discharge line 30 passes through the open hydrogen circulation electromagnetic valve 34 and is introduced into the second fuel supply line 33. Again, it is supplied to the hydrogen flow path 17 of the fuel cell stack 20 and reused.

  Next, the operation of the fuel cell system in the start-up operation that starts from the stop state will be described. In the present embodiment, for convenience of explanation, only the case where hydrogen gas is added to the air electrode 12 will be described.

  FIG. 3 is a first flowchart showing the start-up operation of the fuel cell system according to the embodiment of the present invention.

  First, when a vehicle driver rotates a key inserted in a key insertion slot of an ignition switch (not shown) and turns the rotation position to ON, a start signal is input (step S1), and a system start command is transmitted to the FC controller. Then, the operation for starting the fuel cell system is started. In this case, the FC controller functions as control means for controlling the oxidant or fuel supplied to the oxidant addition channel or the fuel addition channel when the fuel cell is started. In addition, in the state before starting, the suction circulation pump 36 is stopped, and the hydrogen supply valve 26, the hydrogen high pressure supply valve 29, the hydrogen circulation solenoid valve 34, the hydrogen exhaust solenoid valve 62, and the decompression hydrogen discharge valve 62a are closed. Further, the air channel 16 of the fuel cell stack 20 is filled with air, and the hydrogen channel 17 is filled with air as a hydrogen gas replacement gas.

  Subsequently, the FC controller performs stack temperature measurement by the stack temperature detector 23 (step S2). Then, it is determined whether or not the temperature of the fuel cell stack 20 is equal to or higher than 100 [° C.] as a predetermined temperature (step S3). Here, when the temperature of the fuel cell stack 20 is 100 [° C.] or higher, it is considered that the temperature of the unit cell 10 of the fuel cell stack 20 is in a suitable temperature range of the solid polymer electrolyte membrane 11. Therefore, the FC controller opens the hydrogen main valve (step S4), opens the hydrogen supply valve 26 or the hydrogen high pressure supply valve 29, and supplies the hydrogen gas from the fuel storage means 73 to the hydrogen flow path 17 of the fuel cell stack 20. Supply. Further, the hydrogen exhaust electromagnetic valve 62 and the reduced pressure hydrogen discharge valve 62 a are opened, and the suction circulation pump 36 is operated to discharge air from the hydrogen flow path 17 of the fuel cell stack 20. Thereby, hydrogen electrode chamber gas replacement is performed (step S5), and the air filled in the hydrogen flow path 17 is purged and replaced with hydrogen gas.

  The FC controller measures the fuel cell voltage based on the output of the voltmeter 59. When the fuel cell voltage exceeds a predetermined value, the FC controller shifts to FC power generation as a steady operation (step S6), and the process of the start operation Exit.

  On the other hand, when the temperature of the fuel cell stack 20 is not 100 ° C. or higher, the FC controller performs a temperature raising operation (step S7). Then, the FC controller performs the temperature raising bypass valve OPEN (step S8), opens the temperature raising bypass valve 57, and allows the hydrogen gas from the fuel storage means 73 to flow through the temperature raising pipeline 78. The air is circulated through the passage 18 and further air is circulated to the stack main passage (step S9). From the oxidant supply source such as an air supply fan, the air passage 16 is passed through the air supply conduit 77 and the intake manifold 74. To supply air. Then, the hydrogen gas diffuses from the hydrogen addition flow path 18 through the continuous minute holes provided in the air electrode side separator 14 itself, and is uniformly supplied to the surface of the air electrode 12. The hydrogen gas reacts with oxygen in the air supplied to the air flow path 16 at the site of the electrode catalyst layer or the startup temperature raising catalyst layer to generate heat of reaction.

  Subsequently, the FC controller performs stack temperature measurement (step S10), and determines whether or not the temperature of the fuel cell stack 20 is equal to or higher than 100 [° C.] as a predetermined temperature (step S11). If the temperature of the fuel cell stack 20 is not 100 ° C. or higher, the temperature raising bypass valve OPEN is performed again (step S8), and the above-described operation is repeated.

  Further, when the temperature of the fuel cell stack 20 is 100 [° C.] or higher, it is considered that the temperature of the unit cell 10 of the fuel cell stack 20 has been raised to a suitable temperature range of the solid polymer electrolyte membrane 11. Therefore, the FC controller performs the temperature raising bypass valve CLOSE (step S12), closes the temperature raising bypass valve 57, and stops the flow of hydrogen gas to the hydrogen addition flow path 18. Thereby, the supply of hydrogen gas to the surface of the air electrode 12 is stopped, and the reaction with oxygen in the air supplied to the air flow path 16 is stopped. Subsequently, the FC controller opens the hydrogen main valve (step S4). Thereby, hydrogen electrode chamber gas substitution is performed (step S5), it transfers to FC electric power generation (step S6), and the process of starting operation is complete | finished.

  Next, a modified example of the operation of the fuel cell system in the start-up operation that starts from the stop state will be described.

  FIG. 4 is a second flowchart showing the start-up operation of the fuel cell system according to the embodiment of the present invention.

  First, when a vehicle driver rotates a key inserted in a key insertion slot of an ignition switch (not shown) and turns the rotational position to ON, a start signal is input (step S21), and a system start command is transmitted to the FC controller. Then, the operation for starting the fuel cell system is started.

  Subsequently, the FC controller performs stack temperature measurement by the stack temperature detector 23 (step S22). Then, it is determined whether or not the temperature of the fuel cell stack 20 is equal to or higher than 100 [° C.] as a predetermined temperature (step S23). Here, when the temperature of the fuel cell stack 20 is 100 [° C.] or higher, the FC controller opens the hydrogen main valve (step S24) and opens the hydrogen supply valve 26 or the hydrogen high-pressure supply valve 29. Hydrogen gas from the fuel storage means 73 is supplied to the hydrogen flow path 17 of the fuel cell stack 20. Further, the hydrogen exhaust electromagnetic valve 62 and the reduced pressure hydrogen discharge valve 62 a are opened, and the suction circulation pump 36 is operated to discharge air from the hydrogen flow path 17 of the fuel cell stack 20. Thereby, hydrogen electrode chamber gas replacement is performed (step S25), and the air filled in the hydrogen flow path 17 is purged and replaced with hydrogen gas.

  Then, the FC controller measures the fuel cell voltage based on the output of the voltmeter 59. When the fuel cell voltage exceeds a predetermined value, the FC controller shifts to FC power generation as a steady operation (step S26), and the start operation process is performed. Exit.

  On the other hand, when the temperature of the fuel cell stack 20 is not 100 ° C. or higher, the FC controller performs a temperature raising operation (step S27). Then, the FC controller performs the temperature raising bypass valve OPEN (step S28), opens the temperature raising bypass valve 57, and causes the hydrogen gas from the fuel storage means 73 to flow through the temperature raising pipeline 78. The air is circulated through the passage 18 and further air is circulated to the stack main passage (step S29). From the oxidant supply source such as an air supply fan, the air passage 16 is passed through the air supply conduit 77 and the intake manifold 74. To supply air.

  Subsequently, the FC controller counts time (step S30), and determines whether or not a predetermined time has elapsed since the start of the temperature raising operation (step S31). If the predetermined time has not elapsed, the temperature raising bypass valve OPEN is performed again (step S28), and the above-described operation is repeated.

  Here, the predetermined time is a time required from the start of the temperature raising operation until the temperature of the fuel cell stack 20 reaches 100 [° C.] or higher, and the stack temperature performed before the temperature raising operation is started. It can be determined based on the temperature of the fuel cell stack 20 measured in the measurement. In the temperature raising operation, the temperature raising bypass valve 57 is opened to flow through the hydrogen addition flow path 18, and the hydrogen gas supplied to the air electrode 12 reacts with oxygen in the air supplied to the air flow path 16. Thus, reaction heat is generated, that is, the unit cell 10 is heated by burning. In this case, since the amount of combustion heat generated by burning hydrogen gas per unit mass is known, if the flow rate of the hydrogen gas supplied to the air electrode 12 is known, the amount of combustion heat per unit time can be calculated. . It is assumed that a sufficient amount of air is supplied to the air flow path 16 and all the hydrogen gas supplied to the air electrode 12 is combusted. Then, if the heat capacity of the unit cell 10 and the temperature of the unit cell 10 at the start of the temperature raising operation are known, the unit cell 10 is heated to 100 [° C.] based on the amount of combustion heat per unit time. The required time can be calculated.

  Therefore, if the heat of combustion generated by the hydrogen gas per unit mass, the flow rate of the hydrogen gas supplied to the air electrode 12, and the heat capacity of the unit cell 10 are stored in advance in the storage means of the FC controller, the measurement is performed in the stack temperature measurement. The FC controller can calculate the predetermined time based on the temperature of the obtained fuel cell stack 20.

  In addition, when moisture exists in the air flow path 16, the heat capacity of the unit cell 10 changes, so that correction is necessary.

  In addition, the water present in the air flow path 16 is usually the water generated during the previous operation of the fuel cell system, and changes depending on the previous operation status. The change in the heat capacity in the fuel cell can be calculated by grasping the deviation of the temperature rise time rate derived from the stack heat capacity with respect to the amount of heat of hydrogen combustion given on the basis thereof.

  When the predetermined time has elapsed, it is considered that the temperature of the unit cell 10 of the fuel cell stack 20 has been raised to a suitable temperature range of the solid polymer electrolyte membrane 11, so that the FC controller increases the temperature. A temperature bypass valve CLOSE is performed (step S32), the temperature increase bypass valve 57 is closed, and the flow of hydrogen gas to the hydrogen addition passage 18 is stopped. Thereby, the supply of hydrogen gas to the surface of the air electrode 12 is stopped, and the reaction with oxygen in the air supplied to the air flow path 16 is stopped. Subsequently, the FC controller opens the hydrogen main valve (step S24). Thereby, hydrogen electrode chamber gas substitution is performed (step S25), it transfers to FC electric power generation (step S26), and the process of starting operation is complete | finished.

  In the present embodiment, the FC controller can also perform controls other than those described based on the flowcharts shown in FIGS.

  For example, the FC controller can be controlled to supply a fixed amount of hydrogen gas supplied to the air electrode 12. As described above, since the amount of combustion heat generated by burning hydrogen gas per unit mass is known, if the heat capacity of the unit cell 10 or the part to be heated is known, the temperature from a certain point to a predetermined temperature is obtained. The amount of hydrogen gas required to raise the temperature can be determined. Therefore, if a temperature map showing the relationship between the temperature of the unit cell 10 or the part to be heated and the amount of the necessary hydrogen gas is created and stored in the storage means, the hydrogen gas is stored based on the temperature map. It is possible to perform control to supply a constant amount, that is, to perform a quantitative control of hydrogen gas. In the case where moisture is present in the air flow path 16, the heat capacity of the unit cell 10 or the part to be heated may change and the temperature rising rate may change. It is desirable to carry out auxiliary control that converges to. The moisture present in the air flow path 16 is normally the moisture generated during the previous operation of the fuel cell system, and varies depending on the previous operation state. The temperature rise rate changes as the heat capacity of the part to be heated changes. Therefore, in the first step, a predetermined amount of hydrogen gas is supplied to measure the temperature rising rate, and in the second step, the temperature of the unit cell 10 or the part to be heated is raised to 100 [° C.]. It is desirable to control so as to supply the necessary amount of hydrogen gas.

  For example, the FC controller can detect the temperature and control the amount of hydrogen gas supplied to the air electrode 12. If the pressure of the hydrogen gas supplied from the fuel storage means 73 and the opening degree of the temperature raising bypass valve 57 are determined, the temperature of the unit cell 10 or the part to be heated is measured when the fuel cell system is started. When controlling the supply amount of hydrogen gas, as described based on the flowchart shown in FIG. 4, by setting the time for opening the temperature-rising bypass valve 57, the unit cell 10 or the portion to be temperature-rised is set. The temperature can be raised to 100 [° C.]. As described above, when moisture is present in the air flow path 16, the heat capacity of the unit cell 10 or the portion to be heated may change and the temperature rising rate may change. It is desirable to perform auxiliary control that converges to the set temperature by the dividing step.

Further, for example, the FC controller can optimally control the supply amount of hydrogen gas to the air electrode 12. In this case, the necessary supply amount of hydrogen gas is determined by the following parameters (1) to (3).
(1) Initial temperature and target reached temperature of a part to be heated (2) Temperature rise map of a part to be heated by burning a certain amount of hydrogen gas (however, moisture in the air channel 16 (Dry when there is no)
(3) Correction coefficient when water is present in the air flow path 16 with respect to the temperature rise map (correction is performed by grasping the change in the heat capacity of the part to be heated due to the deviation from (2)).
Here, since the heat capacity changes depending on the structural factors such as the size of the unit cell 10 and the size of the fuel cell stack 20, the moisture content in the air flow path 16 and the air electrode 12, etc., a control map and a correction coefficient are set beforehand. It will be necessary.

  In the present embodiment, the operation of the fuel cell system in the start-up operation has been described only in the case where hydrogen gas is added to the air electrode 12, but oxygen in the air is added by adding air to the fuel electrode 13. The same operation is also performed when reacting with hydrogen gas.

  Thus, in the present embodiment, the air electrode side separator 14 or the fuel electrode side separator 15 is formed of a porous body, and the hydrogen addition flow path 18 is formed inside the air electrode side separator 14 or the fuel electrode side separator 15. An air addition passage is formed inside, and hydrogen gas is supplied to the hydrogen addition passage 18 or air is supplied to the air addition passage when the fuel cell system is started. Thereby, hydrogen gas or air can be uniformly added to the surface of the air electrode 12 or the fuel electrode 13, and hydrogen and oxygen in the air can be uniformly reacted on the surface of the air electrode 12 or the fuel electrode 13. it can. Therefore, the air electrode 12 or the fuel electrode 13 can be rapidly heated without deteriorating the air electrode 12 or the fuel electrode 13, and the unit cell 10 can be heated in a short time.

  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 schematic cross section which shows the structure of the unit cell of the fuel cell in embodiment of this invention. It is a figure which shows the structure of the fuel cell system in embodiment of this invention. It is a 1st flowchart which shows the operation | movement of the starting driving | operation of the fuel cell system in embodiment of this invention. It is a 2nd flowchart which shows the operation | movement of the starting operation of the fuel cell system in embodiment of this invention.

Explanation of symbols

10 Unit Cell 11 Solid Polymer Electrolyte Membrane 12 Air Electrode 13 Fuel Electrode 14 Air Electrode Side Separator 15 Fuel Electrode Side Separator 18 Hydrogenation Flow Channel 57 Heating Bypass Valve 73 Fuel Storage Means 78 Heating Pipeline

Claims (7)

A fuel cell having a unit cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and a separator that forms a fuel flow path outside the fuel electrode and forms an oxidant flow path outside the oxygen electrode. And
The fuel electrode side or oxygen electrode side separator is formed of a porous body, and has an oxidant addition channel for adding an oxidant to the fuel electrode inside or a fuel addition channel for adding fuel to the oxygen electrode. A fuel cell which is formed.   2. The fuel cell according to claim 1, wherein the fuel electrode or the oxygen electrode includes a startup temperature raising catalyst layer formed on a separator side surface. A unit cell having an electrolyte layer sandwiched between a fuel electrode and an oxygen electrode; and a separator that forms a fuel flow path outside the fuel electrode and forms an oxidant flow path outside the oxygen electrode. The separator on the electrode side or the oxygen electrode side is formed of a porous body, and an oxidant addition channel for adding an oxidant to the fuel electrode or a fuel addition channel for adding fuel to the oxygen electrode is formed inside. A fuel cell,
Fuel supply means for supplying fuel to the fuel flow path;
An oxidant supply means for supplying an oxidant to the oxidant flow path;
An addition means for supplying an oxidant to the oxidant addition channel or a fuel to the fuel addition channel;
And a control means for controlling an oxidant or fuel supplied to the oxidant addition passage or the fuel addition passage when the fuel cell is started.   4. The fuel cell system according to claim 3, wherein the control unit controls the oxidant or the fuel to be quantitatively supplied to the oxidant addition channel or the fuel addition channel. 5.   5. The fuel cell system according to claim 4, wherein the control unit performs control so as to supply an amount of oxidant or fuel calculated from a fuel amount necessary to raise the temperature to a desired temperature.   The said control means detects the temperature of the said fuel cell, and controls the quantity of the oxidizing agent or fuel supplied to the said oxidizing agent addition flow path or a fuel addition flow path based on this temperature. Fuel cell system.   The said control means correct | amends the change of the heat capacity by the moisture content which remains in the said fuel cell so that the quantity of the oxidizing agent or fuel supplied to the said oxidizing agent addition flow path or a fuel addition flow path may become the optimal. The fuel cell system according to any one of 3 to 6.

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