JP2006156136A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to exhaust a fuel gas into atmosphere after reducing concentration of the fuel gas by a simple constitution without using a device such as a diluter by connecting a fuel exhaust tube passage to exhaust a purged fuel gas in the midway of oxidized gas exit in a fuel cell stack and the exhaust manifold to exhaust the exhausted oxidized gas and generated water after temporarily housing them. <P>SOLUTION: This has the fuel cell stack to generate electric power because the fuel gas and the oxidized gas are supplied, a circulation passage to circulate the fuel gas exhausted from the fuel gas exit of the fuel cell stack by returning it to the fuel gas entrance, the exhaust manifold to exhaust the oxidized gas and formed water exhausted from the oxidized gas exit of the fuel cell stack after temporarily housing, and the fuel exhaust pipe passage to exhaust impurity containing fuel gas exhausted by the purge of the circulation passage into the exhaust manifold. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to 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 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 maintained in a wet state, water is supplied to each of the fuel electrode side and the oxygen electrode side. . 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. In this case, excess water on the oxygen electrode side can be released together with air into the atmosphere, but excess water on the fuel electrode side restricts the release of hydrogen into the atmosphere from the viewpoint of safety. Thus, a technique has been proposed in which the concentration of hydrogen gas is reduced using a diluter and then released into the atmosphere (see, for example, Patent Document 1).
JP 2004-55287 A

  However, in the conventional fuel cell system, since it is necessary to use a diluter, the configuration of the entire fuel cell device becomes complicated and large, and the cost increases. In addition, since water contained in the air or hydrogen gas is discharged without being recovered, the amount of water supplied to the fuel electrode side and the oxygen electrode side is increased.

  The present invention solves the problems of the conventional fuel cell system, and is purged in the middle of the exhaust gas manifold and the exhaust manifold that discharges the oxidized gas and the generated water after temporarily storing them in the fuel cell stack. By connecting a fuel discharge line for discharging fuel gas, a fuel cell system capable of reducing the concentration of the fuel gas with a simple configuration and then releasing it into the atmosphere without using a device such as a diluter The purpose is to provide.

  Therefore, in the fuel cell system of the present invention, a fuel cell stack that is supplied with fuel gas and an oxidizing gas to generate power, and a fuel gas discharged from the fuel gas outlet of the fuel cell stack is returned to the fuel gas inlet and circulated. A circulation path to be discharged, an exhaust manifold for temporarily discharging the oxidizing gas and generated water discharged from the oxidizing gas outlet of the fuel cell stack, and an exhaust manifold for discharging the impurity-containing fuel gas discharged by purging the circulation path And a fuel discharge pipe for discharging into the inside.

  In another fuel cell system of the present invention, the outlet end of the fuel discharge pipe is disposed in the vicinity of the oxidizing gas outlet of the fuel cell stack.

  In still another fuel cell system of the present invention, when impurity-containing fuel gas is discharged from the fuel discharge pipe, the concentration of the fuel gas discharged from the exhaust manifold is set to a concentration that can be released into the atmosphere. Control means for controlling the supply amount of the oxidizing gas to the fuel cell stack so that the fuel cell stack can be diluted.

  According to the present invention, in a fuel cell system, a fuel cell stack that is supplied with fuel gas and an oxidizing gas to generate power, and a fuel gas discharged from the fuel gas outlet of the fuel cell stack is returned to the fuel gas inlet and circulated. A circulation path to be discharged, an exhaust manifold that is discharged after temporarily storing the oxidizing gas and the generated water discharged from the oxidizing gas outlet of the fuel cell stack, and the exhaust manifold that contains the impurity-containing fuel gas discharged by purging the circulation path And a fuel discharge pipe for discharging into the inside.

  In this case, the fuel gas discharged from the fuel discharge pipe smoothly diffuses into the oxidizing gas flow passing through the exhaust manifold and quickly mixes with the oxidizing gas. Further, since a special mechanism for diluting the fuel gas such as a diluter is not provided, the configuration of the fuel cell system can be simplified, the size can be reduced, and the cost can be suppressed.

  In another fuel cell system, the outlet end of the fuel discharge pipe is disposed in the vicinity of the oxidizing gas outlet of the fuel cell stack.

  In this case, since the mixing distance of the fuel gas and the oxidizing gas in the exhaust manifold can be increased, the mixing of the fuel gas and the oxidizing gas is promoted, and the fuel gas is sufficiently diffused and mixed in the oxidizing gas. However, there is no local high concentration.

  In still another fuel cell system, when impurity-containing fuel gas is discharged from the fuel discharge pipe, the concentration of the fuel gas discharged from the exhaust manifold is diluted to a concentration that can be released into the atmosphere. And a control means for controlling the supply amount of the oxidizing gas to the fuel cell stack.

  In this case, the fuel gas discharged from the fuel discharge pipe is smoothly diffused into a sufficiently large amount of oxidizing gas flow passing through the exhaust manifold, and quickly mixed with the oxidizing gas. Since the fuel gas is mixed in a large amount of the oxidizing gas, the concentration of the fuel gas released into the atmosphere is sufficiently lowered, and no safety problem occurs.

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

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

  In the figure, reference numeral 20 denotes a fuel cell stack as a fuel cell (FC), 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 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, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) type fuel cell using hydrogen gas as fuel and oxygen or air as oxidant. 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 this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. Then, when one of the gas diffusion electrodes is used as a fuel electrode, and fuel gas, that is, hydrogen gas as anode gas, is supplied to the fuel electrode through a fuel flow path in contact with the fuel electrode surface, hydrogen is converted into hydrogen ions (protons). And electrons, and hydrogen ions permeate the solid polymer electrolyte membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode and an oxidizing gas, that is, air as a cathode gas, is supplied to the oxygen electrode through an air flow channel in contact with the surface of the oxygen electrode, oxygen in the air, the hydrogen ions And the electrons are combined to produce water, and produced water is generated. An electromotive force is generated by such an electrochemical reaction.

  In the figure, an apparatus for supplying hydrogen gas as a fuel gas and air as an oxidant to the 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. Accordingly, 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 on 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 gas is supplied to the fuel gas inlet of the fuel cell stack 20, that is, the inlet of the fuel gas flow path, through the second fuel supply pipe 33 as the 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. The first fuel supply line 21 is connected to a start-up bypass line 22 for supplying hydrogen gas by bypassing the second fuel pressure regulating valve 25b when the fuel cell stack 20 is started. An activation fuel supply electromagnetic valve 23 is disposed in the activation bypass line 22. The fuel storage means 73 has a sufficiently large capacity and always has a capability of supplying hydrogen gas at a sufficiently high pressure. In the example shown in the figure, there are a plurality of, for example, three fuel storage means 73, and the first fuel supply pipe 21 is connected to each fuel storage means 73 in a plurality. It is branched and merges 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.

  Then, hydrogen gas discharged as an unreacted component from the fuel gas outlet of the fuel cell stack 20, that is, the outlet of the fuel gas flow path, 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. As a result, a circulation path for circulating the fuel gas discharged from the fuel gas outlet of the fuel cell stack 20 back to the fuel gas inlet is formed, the hydrogen gas discharged outside the fuel cell stack 20 is recovered, and the fuel cell is recovered. The fuel gas flow path of the stack 20 can be supplied and reused.

  The water recovery drain tank 60 is connected to a fuel discharge pipe 56 as an anode gas discharge pipe. A hydrogen start exhaust electromagnetic valve 62 is provided in the fuel discharge pipe 56, so that the fuel cell stack 20 The hydrogen gas discharged from the fuel gas flow path at startup can be discharged into the atmosphere. The outlet end side of the fuel discharge pipe 56 is connected to the exhaust manifold 71. Further, the fuel discharge pipe 56 branches from the middle, and the branch portion is connected to the fuel discharge pipe 30 between the suction circulation pump 36 and the hydrogen circulation electromagnetic valve 34. Further, a hydrogen start / stop electromagnetic valve 56a is disposed at the branch portion.

  Further, an outside air introduction line 28 is connected between the second fuel supply line 33 and the hydrogen circulation solenoid valve 34 in the fuel discharge line 30. The outside air introduction conduit 28 is provided with an outside air introduction electromagnetic valve 28a and an air filter 28b, and can introduce outside air into the fuel gas passage when the operation of the fuel cell stack 20 is completed. Yes.

  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 start fuel supply solenoid valve 23, the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the hydrogen circulation solenoid valve 34, the hydrogen start / stop solenoid valve 56a, and the hydrogen start exhaust solenoid valve 62 are so-called on-off. It is of the type and is actuated by an actuator comprising an electric motor, a pulse motor, an electromagnet or 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. The air filter 28b removes dust, impurities, harmful gases and the like contained in the air.

  On the other hand, the oxidant, that is, the air as the oxidant gas is supplied from the oxidant supply source 75 such as an air supply fan, an air cylinder, and an air tank through the oxidant supply line 77 and the intake manifold 74 to the fuel cell stack 20. To the air flow path. Note that oxygen can be used as the oxidizing agent instead of air. The air discharged from the air flow path is discharged to the atmosphere through the exhaust manifold 71 and the condenser 72. In this case, the exhaust manifold 71 has a function of temporarily storing the air as the oxidizing gas discharged from the oxidizing gas outlet of the fuel cell stack 20 and the generated water generated at the oxygen electrode and then discharging it.

  The oxidant supply pipe 77 is provided with a water supply nozzle 76 for spraying water and maintaining the air electrode (cathode electrode) of the fuel cell stack 20 in a wet state. Further, the air electrode and the fuel electrode 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 type as long as it removes dust, impurities, etc. contained in the water.

  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 control means (not shown). 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 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 oxidant supply source 75, the first fuel pressure adjustment valve 25a, the second fuel pressure adjustment valve 25b, and the starting fuel supply electromagnetic valve 23 are detected. The operation of the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the hydrogen circulation solenoid valve 34, the suction circulation pump 36, the drain pump 51, the feed water pump 54, the hydrogen start / stop solenoid valve 56a, the hydrogen start exhaust solenoid valve 62, etc. Control. Furthermore, the control means controls the operation of all the devices that supply fuel and oxidant to the fuel cell stack 20 in cooperation with other sensors and other control devices. Then, as will be described later, when the impurity-containing fuel gas is discharged from the fuel discharge line 56, the control means releases the concentration of hydrogen gas as the fuel gas discharged from the exhaust manifold 71 into the atmosphere. The supply amount of air as an oxidizing gas to the fuel cell stack 20 is controlled so that the fuel cell stack 20 can be diluted to a possible concentration.

  Next, the configuration of the portion where the outlet end of the fuel discharge pipe 56 is connected to the exhaust manifold 71 will be described in detail.

  FIG. 2 is a diagram showing the configuration of the intake manifold and the exhaust manifold attached to the fuel cell stack in the embodiment of the present invention. 2A is a plan view, and FIG. 2B is a side view.

  FIG. 2 shows an example of the intake manifold 74 and the exhaust manifold 71 attached to the fuel cell stack 20 disposed under the floor of the vehicle. In this case, an air supply fan composed of a sirocco fan or the like is used as the oxidant supply source 75 and is connected to the tip of the intake manifold 74 (the right end in FIGS. 1 and 2). The rear end of the intake manifold 74 is attached so as to cover the upper surface of the fuel cell stack 20, and air as cathode gas supplied through the intake manifold 74 moves upward in the fuel cell stack 20. It circulates downward from. That is, in the example shown in FIG. 2, the air flow path in the fuel cell stack 20 is formed so as to extend in the vertical direction in FIG. The air discharged from the air flow path of the fuel cell stack 20 flows into the exhaust manifold 71 attached so as to cover the lower surface of the fuel cell stack 20. In this case, as shown in FIG. 2B, the exhaust manifold 71 extends obliquely upward and rearward, and the rear end (left end in the drawing) is connected to a condenser 72 not shown.

  Here, the outlet end side of the fuel discharge pipe 56 is connected to the exhaust manifold 71, and the outlet end member 56 b of the fuel discharge pipe 56 is arranged so as to be located substantially at the center of the air flow path in the exhaust manifold 71. It is installed. The outlet end member 56b faces the downstream side of the air flow path passing through the exhaust manifold 71, and the hydrogen gas discharged from the outlet end member 56b is in the same direction as the air passing through the exhaust manifold 71. It comes to flow. Therefore, the hydrogen gas discharged from the outlet end member 56b is smoothly diffused into the air flow passing through the exhaust manifold 71 and mixed with air. Further, the outlet end member 56b is desirably disposed at a position as close as possible to the outlet of the air flow path in the fuel cell stack 20. That is, it is desirable that the outlet end of the fuel discharge pipe 56 is disposed in the vicinity of the oxidizing gas outlet of the fuel cell stack 20. Thereby, the mixing distance of hydrogen gas and air in the exhaust manifold 71 can be increased.

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

  FIG. 3 is a diagram for explaining the operation of the fuel cell system according to the embodiment of the present invention. FIG. 3 schematically shows only the configuration of the portion related to the description of the operation in the fuel cell system.

  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 always operates so as to supply a constant amount of air to the air flow path of the fuel cell stack 20. 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. Further, in the present embodiment, the pressure of the air supplied to the air flow path 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 and the like do not need to have pressure resistance, so that the configuration can be simplified.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane and enters the fuel gas flow path. And the fuel electrode side of the solid polymer electrolyte membrane is humidified. As a result, the fuel electrode side of the solid polymer electrolyte membrane becomes wet, and hydrogen ions generated from hydrogen by the electrochemical reaction can move smoothly in the solid polymer electrolyte membrane.

  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 led out 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. Since the hydrogen start / stop solenoid valve 56a is in a closed state, the hydrogen gas discharged from the suction circulation pump 36 is not discharged into the atmosphere through the fuel discharge pipe 56, but the second fuel. It is introduced into the supply line 33. Further, since the outside air introduction electromagnetic valve 28 a is also closed, the outside air is not introduced into the second fuel supply pipe 33.

  Here, since the fuel discharge line 30 is connected to the side wall of the upper part of the water recovery drain tank 60, only the hydrogen gas in the dry state in which the reverse diffusion water is separated and becomes lightweight becomes the fuel discharge line. 30 is discharged, and moisture is not discharged. Further, since the fuel discharge pipe 31 and the fuel discharge pipe 30 are connected to the side wall of the upper part of the water recovery drain tank 60 at a position apart from each other, they are introduced from the fuel discharge pipe 31 into the water recovery drain tank 60. The gas-liquid mixture thus made does not flow out of the fuel discharge line 30 as it is. As a result, surplus reverse diffusion water that has permeated into the fuel gas flow path can be trapped appropriately, and surplus hydrogen gas can be recovered in a dry state and reused.

  On the other hand, the reverse diffusion water that has been separated from the gas-liquid mixture and dropped is stored as stored water in the lower portion of the water recovery drain tank 60. Here, when the capacity of the water recovery drain tank 60 is sufficiently large, the vehicle on which the fuel cell stack 20 is mounted once travels after filling the fuel storage means 73 with hydrogen gas as fuel. It is not necessary to discharge water from the water recovery drain tank 60 until the next time hydrogen gas is filled into the fuel storage means 73. However, if the capacity of the water recovery drain tank 60 is not sufficiently large, it is necessary to perform a purge as an operation for discharging water from the water recovery drain tank 60 even during steady operation in the fuel cell system.

  When purging, the control means closes the hydrogen circulation electromagnetic valve 34 to stop the circulation of hydrogen gas. Then, the hydrogen activation exhaust electromagnetic valve 62 is opened, and the stored water stored in the water recovery drain tank 60 is discharged from the fuel discharge line 56. Further, the hydrogen start / stop electromagnetic valve 56 a is opened, and the hydrogen gas in the fuel gas passage is discharged from the fuel discharge conduit 56. As a result, the hydrogen gas is discharged into the fuel as indicated by an arrow 81 in FIG. 3 together with the stored water in the water recovery drain tank 60, moisture in the fuel flow path of the fuel cell stack 20, and other impurities. It flows through the pipe 56 and flows into the exhaust manifold 71 from the outlet end member 56b. That is, the impurity-containing fuel gas discharged by the purge of the circulation path is discharged into the exhaust manifold 71 through the fuel discharge pipe 56.

  As described above, the outlet end member 56 b of the fuel discharge pipe 56 is disposed so as to be positioned substantially at the center of the air flow path in the exhaust manifold 71, and is downstream of the air flow path passing through the exhaust manifold 71. The hydrogen gas discharged from the outlet end member 56b flows in the same direction as the air passing through the exhaust manifold 71. Then, a large amount of air supplied from the oxidant supply source 75 passes through the intake manifold 74, the air flow path in the fuel cell stack 20, the exhaust manifold 71, and the condenser 72 as shown by an arrow 82 in FIG. It is in circulation.

  The control means supplies a sufficiently large amount of air from the oxidant supply source 75. In this case, the control means sets the amount of air supplied from the oxidant supply source 75 based on the hydrogen gas amount-air amount map. The hydrogen gas amount-air amount map shows the amount of hydrogen gas discharged from the fuel discharge line 56 and the hydrogen concentration to such an extent that the discharged hydrogen gas can be diluted and safely released into the atmosphere. It is a map which shows the relationship with the air quantity required in order to carry out, and is stored in the memory | storage means. Accordingly, a sufficiently large amount of air can be supplied from the oxidant supply source 75 with respect to the set discharge amount of hydrogen gas.

  Further, the control means starts the discharge of hydrogen gas from the fuel discharge line 56 after a predetermined time has elapsed after the oxidant supply source 75 starts supplying the set amount of air. The predetermined time is a time from when the oxidant supply source 75 starts supplying the set amount of air until the set amount of air circulates in the exhaust manifold 71. It is set in advance.

  Therefore, the hydrogen gas discharged from the outlet end member 56b is smoothly diffused into a sufficiently large amount of air flowing through the exhaust manifold 71 and quickly mixed with air. Further, the outlet end member 56b is desirably disposed at a position as close as possible to the outlet of the air flow path in the fuel cell stack 20. Thereby, the mixing distance of hydrogen gas and air in the exhaust manifold 71 can be increased.

  Note that a hydrogen concentration detector may be disposed on the downstream side of the outlet end member 56b in the exhaust manifold 71. In this case, the control means sets the amount of air supplied from the oxidant supply source 75 based on the hydrogen concentration detected by the hydrogen concentration detector and the hydrogen concentration-air amount map. The hydrogen concentration-air amount map shows the hydrogen concentration in the air in the exhaust manifold 71 and the hydrogen gas in the air in the exhaust manifold 71 when the hydrogen concentration in the air in the exhaust manifold 71 is a predetermined value or more. Is a map showing the relationship with the amount of air necessary to reduce the hydrogen concentration to the extent that it can be safely released into the atmosphere, and is stored in the storage means. As a result, it is possible to supply the oxidant supply source 75 with an amount of air necessary for reducing the concentration of hydrogen gas to such an extent that it can be released into the atmosphere.

  And the air which hydrogen gas diffused and mixed passes through the condenser 72, and is discharged | emitted in air | atmosphere. In this case, mixing with hydrogen gas and air is further promoted by passing through the condenser 72. Since hydrogen gas is mixed in a large amount of air, the concentration of hydrogen gas in the air released through the condenser 72 is sufficiently reduced, which may cause a safety problem. Absent. Further, since the hydrogen gas is sufficiently diffused and mixed in the air discharged through the condenser 72, it is safe without locally increasing the concentration.

  In addition, the water flowing into the exhaust manifold 71 from the outlet end member 56b of the fuel discharge pipe 56 together with the hydrogen gas is also mixed into the air, but is condensed and removed from the air when passing through the condenser 72. The Then, the water condensed by the condenser 72 is collected in the water tank 52 through the condensed water discharge line 79, and then sprayed from the water supply nozzle 76 through the water supply line 53. It is reused to keep the air electrode moist and cool.

  Next, the operation when stopping the operation of the fuel cell system will be described. In this case, the control means first closes the fuel supply electromagnetic valve 26 and the hydrogen circulation electromagnetic valve 34 to shut off the supply of hydrogen gas to the fuel gas flow path. Then, the hydrogen start / stop electromagnetic valve 56 a is opened, and the hydrogen gas in the fuel gas passage is discharged from the outlet end member 56 b of the fuel discharge pipe 56 into the exhaust manifold 71. Thereby, the stored water stored in the water recovery drain tank 60 is also discharged.

  In this case, since the suction circulation pump 36 is operating, the hydrogen remaining in the fuel cell stack 20, the water recovery drain tank 60, the second fuel supply line 33, the fuel discharge line 30 and the fuel discharge line 31. The gas is sucked by the suction circulation pump 36 and discharged from the outlet end member 56 b of the fuel discharge pipe 56 into the exhaust manifold 71. And since the inside of a fuel gas flow path becomes a negative pressure, hydrogen gas is reliably removed from the fuel gas flow path quickly and discharged.

  Then, as in the case of purging in the above-described steady operation, the control means supplies a sufficiently large amount of air from the oxidant supply source 75. Therefore, the hydrogen gas discharged from the outlet end member 56b is smoothly diffused into a sufficiently large amount of air flowing through the exhaust manifold 71 and quickly mixed with air.

  Further, the air in which hydrogen gas is diffused and mixed passes through the condenser 72 and is released into the atmosphere. In this case, mixing with hydrogen gas and air is further promoted by passing through the condenser 72. Since hydrogen gas is mixed in a large amount of air, the concentration of hydrogen gas in the air released through the condenser 72 is sufficiently reduced, which may cause a safety problem. Absent. Further, since the hydrogen gas is sufficiently diffused and mixed in the air discharged through the condenser 72, it is safe without locally increasing the concentration.

  Also, the water flowing into the exhaust manifold 71 from the outlet end member 56b of the fuel discharge pipe 56 together with the hydrogen gas is mixed into the air, but when it passes through the condenser 72, it is condensed and removed from the air. The Then, the water condensed by the condenser 72 is collected in the water tank 52 through the condensed water discharge pipe 79.

  The pressure of the hydrogen gas in the fuel gas flow path is detected by a pressure sensor 78. In this case, since the pressure of the hydrogen gas can be considered to be the same in the range from the fuel supply solenoid valve 26 to the suction circulation pump 36 in the path through which the hydrogen gas flows, the pressure sensor 78 is disposed within the range. Then, the pressure detected by the pressure sensor 78 is equal to the pressure of the fuel gas flow path of the fuel cell stack 20.

  Subsequently, when the hydrogen gas pressure in the fuel gas flow path becomes a predetermined pressure or lower in this state, or when a predetermined time, which is a time until the pressure reaches the predetermined pressure, elapses, the control means The electromagnetic valve 28a is opened and air is introduced into the fuel gas flow path. In this case, since the fuel supply electromagnetic valve 26 is in a closed state, the introduced air does not flow toward the fuel storage means 73. Thereby, the fuel gas flow path of the fuel cell stack 20 is filled with air. Since the air passes through the air filter 28b and is filtered, it does not contain dust, impurities, harmful gases, etc. that exist in the atmosphere. Therefore, a member such as a catalyst in the fuel gas passage is not contaminated or altered by the dust, impurities, harmful gas, or the like.

  Subsequently, the process waits until the output of the fuel cell stack 20 becomes a predetermined voltage or less in this state, or until a predetermined time elapses until the output becomes the predetermined voltage. Here, the predetermined voltage corresponds to a state in which no hydrogen gas remains in the fuel gas flow path, the air is filled, and a potential difference is not substantially generated between the fuel electrode and the air electrode. Output voltage.

  When the output of the fuel cell stack 20 becomes equal to or lower than the predetermined voltage or the predetermined time has elapsed, the control means stops the suction circulation pump 36, closes the outside air introduction electromagnetic valve 28a, and finally oxidizes. The agent supply source 75 is stopped. As a result, the output of the fuel cell stack 20 is stopped.

  When the operation of the fuel cell system is started, first, the hydrogen start exhaust solenoid valve 62 and the hydrogen start stop electromagnetic valve 56a are opened, and the air in the fuel gas flow path of the fuel cell stack 20 becomes the fuel discharge pipe. It is discharged through the path 56. Subsequently, the fuel supply electromagnetic valve 26 is turned on, and hydrogen gas from the fuel storage means 73 is supplied to the fuel gas flow path of the fuel cell stack 20 through the first fuel supply pipe 21 and the second fuel supply pipe 33. To be. At this time, since the hydrogen starting exhaust electromagnetic valve 62 and the hydrogen starting / stopping electromagnetic valve 56a are open, purging is performed by hydrogen gas supplied with air and moisture remaining in the fuel gas flow path.

  As described above, in the present embodiment, the fuel cell system includes the outlet end member 56b of the fuel discharge pipe 56 disposed in the exhaust manifold 71 connected to the outlet of the fuel cell stack 20, and purged hydrogen. The gas is discharged into the exhaust manifold 71. Therefore, the hydrogen gas discharged from the outlet end member 56b is smoothly diffused into the air flow passing through the exhaust manifold 71 and quickly mixed with air.

  In addition, an amount of air necessary for diluting the discharged hydrogen gas and reducing the hydrogen concentration to such an extent that it can be safely released into the atmosphere is supplied from the oxidant supply source 75 into the exhaust manifold 71. Therefore, the hydrogen gas concentration in the air released into the atmosphere is sufficiently reduced, and no safety problem occurs.

  Further, a condenser 72 is connected to the rear end of the exhaust manifold 71, and the air in which hydrogen gas is diffused and mixed passes through the condenser 72 and is released into the atmosphere. Therefore, since the mixing of the hydrogen gas and the air is further promoted by passing through the condenser 72, the hydrogen gas is sufficiently diffused and mixed in the air, and the concentration is not locally increased. .

  Further, the water flowing into the exhaust manifold 71 together with the hydrogen gas is mixed in the air, but when passing through the condenser 72, it is condensed and removed from the air, collected in the water tank 52, and reused. The Therefore, the shortage of water sprayed to humidify the air electrode of the fuel cell stack 20 can be compensated, and the water tank 52 can be reduced in size and weight.

  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 intake manifold and exhaust manifold attached to the fuel cell stack in embodiment of this invention. It is a figure explaining operation | movement of the fuel cell system in embodiment of this invention.

Explanation of symbols

20 Fuel cell stack 30, 31, 56 Fuel discharge pipe 71 Exhaust manifold

Claims (3)

A fuel cell stack that is supplied with fuel gas and oxidizing gas to generate electricity;
A circulation path for circulating the fuel gas discharged from the fuel gas outlet of the fuel cell stack back to the fuel gas inlet;
An exhaust manifold that discharges after temporarily storing the oxidizing gas and generated water discharged from the oxidizing gas outlet of the fuel cell stack;
A fuel cell system comprising: a fuel discharge pipe for discharging the impurity-containing fuel gas discharged by purging the circulation path into the exhaust manifold.   2. The fuel cell system according to claim 1, wherein an outlet end of the fuel discharge pipe is disposed in the vicinity of an oxidizing gas outlet of the fuel cell stack.   When impurity-containing fuel gas is discharged from the fuel discharge line, the concentration of the fuel gas discharged from the exhaust manifold can be reduced to a concentration that can be released into the atmosphere. The fuel cell system according to claim 1, further comprising a control unit that controls a supply amount of the oxidizing gas.

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