JP2004288491A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of collecting and reclaiming a fuel gas with a simple structure without enlarging a fuel cell, and capable of maintaining high performance for a long period of time at a low fuel consumption rate. <P>SOLUTION: This fuel cell system is provided with an electrolyte membrane, a fuel electrode and an oxygen electrode to hold the electrolyte membrane between them, a fuel chamber in contact with the fuel electrode, and an oxygen chamber in contact with the oxygen electrode. The system also has a fuel cell which maintains its wet condition because water is inversely diffused from the oxygen electrode to the fuel cell in the electrolyte membrane, a fuel supply pipeline connected to the fuel chamber to supply a fuel gas, a fuel exhausting pipeline connected to the fuel chamber to exhaust the fuel gas of the fuel chamber, a gas-liquid separating trap disposed in the fuel exhausting pipeline to separate inversely diffused water taken into the fuel gas exhausted from the fuel chamber, and a fuel exhausting pipeline connected to the gas-liquid separating trap and the fuel supply pipeline to introduce the fuel gas exhausted from the gas-liquid separating trap to the fuel supply pipeline. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system.
[0002]
[Prior art]
Conventionally, fuel cells have high power generation efficiency and do not emit harmful substances, so they have been put to practical use as industrial or household power generators or as power sources for artificial satellites and spacecraft. It is being developed as a power source for vehicles such as buses and trucks. The fuel cell may be of 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.
[0003]
In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes, integrated and joined. When one of the gas diffusion electrodes is used as an anode and hydrogen gas is supplied as fuel to the surface of the gas diffusion electrode, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions pass through the solid polymer electrolyte membrane. When the other of the gas diffusion electrodes is used as a cathode and air is supplied as an oxidizing agent to the surface of the cathode, oxygen in the air is combined with the hydrogen ions and electrons to generate water. An electromotive force is generated by such an electrochemical reaction.
[0004]
In a polymer electrolyte fuel cell, since it is necessary to maintain both sides of the polymer electrolyte membrane in a wet state, water is supplied to each of the anode electrode side as the fuel electrode and the cathode electrode side as the oxygen electrode. A supply technique has been proposed (for example, see Patent Document 1). In this case, the fuel and the oxidant are humidified to supply water to each of the anode electrode side and the cathode electrode side. Further, irregularities are formed on the surfaces of the anode electrode and the cathode electrode, so that the concave portions function as water repellent portions and the convex portions function as water collecting portions. Then, a wick is provided so as to be in contact with a water collecting portion on the surface of the anode and the cathode, and excess water is discharged from the water collecting portion to the outside of the fuel cell through the wick and stored in a trap. Has become.
[0005]
[Patent Document 1]
JP-A-4-12462
[0006]
[Problems to be solved by the invention]
However, in the conventional fuel cell, a wick is provided so as to contact the water collecting portions on the surfaces of the anode and the cathode in order to discharge excess water to the outside of the fuel cell. Therefore, the configuration of the fuel cell becomes complicated, and the size of the fuel cell increases. In a general fuel cell, several tens to several hundreds of solid polymer electrolyte membranes are sandwiched between two gas diffusion electrodes and integrated and joined. Therefore, when wicks are provided on the surfaces of the anode and cathode in each unit, the configuration of the entire fuel cell formed by connecting tens to hundreds of units becomes extremely complicated, and the entire fuel cell becomes It becomes large.
[0007]
Further, in the conventional fuel cell, separation of water from fuel discharged from the fuel cell is not considered. In the case of a normal fuel cell, the amount of fuel supplied to the anode is larger than necessary so as not to cause a shortage of fuel on the surface of the anode. Therefore, it is common to discharge surplus fuel from the fuel cell to the atmosphere. Furthermore, when the water stored in the trap is discharged to the outside, hydrogen of the fuel is also exhausted, so that the fuel consumption increases.
[0008]
The present invention solves the above-mentioned conventional problems, so that the fuel electrode side of the solid polymer electrolyte membrane is wetted with the back diffusion water, and the excess back diffusion water is discharged together with the fuel gas to discharge the fuel electrode. Prevent water clogging of the fuel passage on the side and separate moisture from the discharged fuel gas to collect and reuse dried fuel without increasing the size of the fuel cell with a simple configuration It is an object of the present invention to provide a fuel cell system capable of maintaining a high performance with a low fuel consumption rate over a long period of time.
[0009]
[Means for Solving the Problems]
For this purpose, the fuel cell system of the present invention includes an electrolyte membrane, a fuel electrode and an oxygen electrode sandwiching the electrolyte membrane, a fuel chamber in contact with the fuel electrode, and an oxygen chamber in contact with the oxygen electrode. A fuel cell in which water is back-diffused from the oxygen electrode to the fuel electrode in the electrolyte membrane to maintain the wet state, a fuel supply pipe connected to the fuel chamber and supplying fuel gas to the fuel chamber, A fuel discharge pipe connected to the fuel chamber for discharging fuel gas from the fuel chamber; and a back-diffusion water disposed in the fuel discharge pipe and taken in by the fuel gas discharged from the fuel chamber. A gas-liquid separation trap, and a fuel discharge line connected to the gas-liquid separation trap and the fuel supply line, for introducing the fuel gas discharged from the gas-liquid separation trap into the fuel supply line.
[0010]
In another fuel cell system of the present invention, the fuel cell system further includes a drain pipe connected to the gas-liquid separation trap and having a drain valve, and the drain valve is configured to open and close the drain pipe. And controlling the amount of reverse diffusion water stored in the gas-liquid separation trap.
[0011]
In still another fuel cell system according to the present invention, the gas-liquid separation trap further includes a water level sensor, and the drainage on-off valve opens and closes the drainage pipe based on a water level detected by the water level sensor.
[0012]
In still another fuel cell system according to the present invention, the drainage on-off valve opens and closes the drainage line in accordance with a sequence set based on the properties of the reverse diffusion water.
[0013]
In still another fuel cell system according to the present invention, the drain pipe is connected to a water tank, and the back-diffused water discharged from the gas-liquid separation trap is collected in the water tank.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is a conceptual diagram of a fuel cell system according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a configuration of a unit unit of the fuel cell according to the first embodiment of the present invention.
[0016]
In FIG. 1, reference numeral 11 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, riding carts, luggage carts, and the like. Here, the vehicle is provided 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 very wide, it is desirable to use the fuel cell stack 11 as a power source together with a secondary battery (not shown) as power storage means.
[0017]
The fuel cell stack 11 is of an alkaline aqueous solution type (AFC), a phosphoric acid type (PAFC), a molten carbonate type (MCFC), a solid oxide type (SOFC), a direct type methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is preferable.
[0018]
More preferably, a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell using hydrogen gas as a fuel and oxygen or air as an oxidant, or a PEM (Proton Exchange Membrane) type fuel cell is used. Here, the PEM fuel cell generally has a stack in which a plurality of cells (Fuel Cell) in which a catalyst, an electrode, and a separator are connected on both sides of a solid polymer electrolyte membrane that transmits ions such as protons are connected in series. (Stack).
[0019]
In the present embodiment, as shown in FIG. 2, the cell 40 includes a solid polymer electrolyte membrane 45 formed by a fuel electrode 43 and an oxygen electrode 44 which are electrodes in which a gas diffusion layer and a reaction layer are connected to one. The separator 46 and the separator 47 made of a metal plate, carbon, a carbon plate, or the like are sandwiched and sandwiched. A plurality of fuel chambers 48 are formed in the separator 46 so as to extend in a direction perpendicular to the plane of the drawing, and a plurality of oxygen chambers 49 are formed in the separator 47 in a vertical direction in the figure. It is formed so that. One surface of the fuel chamber 48 and the oxygen chamber 49 is in contact with the fuel electrode 43 and the oxygen electrode 44. When the fuel electrode 43 is used as an anode electrode and hydrogen gas is supplied as fuel gas into the fuel chamber 48, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions pass through the solid polymer electrolyte membrane 45. I do. When the oxygen electrode 44 is used as a cathode and air is supplied as an oxidizing agent into the oxygen chamber 49, oxygen in the air is combined with the hydrogen ions and electrons to generate water. An electromotive force is generated by such an electrochemical reaction.
[0020]
For example, in the present embodiment, the fuel cell stack 11 is, for example, a PEM type fuel cell, and includes a stack in which several hundred cells are connected in series. The output is several to several tens [kW]. The temperature during the steady operation is about 30 to 90 [° C.].
[0021]
In addition, hydrogen gas, which is a fuel obtained by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 11. 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 13 such as a hydrogen storage alloy or a hydrogen gas cylinder. As a result, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 11 can supply a necessary current by following the fluctuation of the load of the vehicle without delay.
[0022]
In this case, the output impedance of the fuel cell stack 11 is extremely low and can be approximated to zero.
[0023]
FIG. 1 shows a device for supplying hydrogen gas as a fuel gas and air as an oxidant to a fuel cell stack 11. Hydrogen gas is supplied from a container storing a hydrogen storage alloy, a container storing a hydrogen storage liquid such as decalin, a fuel storage means 13 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the fuel chamber 48 of the fuel cell stack 11 through a second fuel supply pipe 33 serving as a fuel supply pipe connected to the first fuel supply pipe 21. The first fuel supply pipe 21 is provided with a fuel storage means open / close valve 24, a pressure sensor 27, a first fuel pressure control valve 25a, a second fuel pressure control valve 25b, and a fuel supply solenoid valve 26. You. Further, a safety valve 33 a is provided in the second fuel supply pipe 33. 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 11 is started. A starting fuel supply solenoid valve 23 is provided in the starting bypass pipe 22. Further, the fuel storage means 13 has a sufficiently large capacity and has an ability to always supply hydrogen gas at a sufficiently high pressure.
[0024]
The hydrogen gas discharged from the fuel chamber 48 of the fuel cell stack 11 is discharged to the outside of the fuel cell stack 11 through the fuel discharge pipe 31. A suction circulation pump 36 is provided in the fuel discharge line 31, and an end of the fuel discharge line 31 opposite to the fuel cell stack 11 is connected to a gas-liquid separation trap 60. The gas-liquid separation trap 60 is connected to a fuel discharge pipe 30 for discharging hydrogen gas separated from water. A startup steady operation switching valve 34 is provided in the fuel discharge line 30. Note that, if necessary, a second suction circulation pump 36a may be provided between the gas-liquid separation trap 60 and the startup steady-state operation switching valve 34. An end of the fuel discharge line 30 opposite to the gas-liquid separation trap 60 is connected to a second fuel supply line 33. Thereby, the hydrogen gas led out of the fuel cell stack 11 can be collected, supplied to the fuel chamber 48 of the fuel cell stack 11, and reused.
[0025]
In addition, between the fuel cell stack 11 and the suction circulation pump 36 in the fuel discharge line 31, a fuel discharge line 56 dedicated for starting is connected. A start-only exhaust valve 56a, a start-only check valve 56b, and a muffler 56c are provided in the start-only fuel discharge line 56. Hydrogen gas discharged from the fuel chamber 48 when the fuel cell stack 11 is started is provided. Can be discharged into the atmosphere. The hydrogen gas may not be directly discharged to the atmosphere but may be discharged after being combined with oxygen to form water.
[0026]
Further, a water discharge pipe 61 is connected to the gas-liquid separation trap 60 as a drain pipe for discharging water separated from hydrogen gas and collecting it in a water tank 52 described later. The water discharge pipe 61 is provided with a check valve 63 for drainage and a solenoid valve 62 for drainage as an on-off valve for drainage. The drain check valve 63 can be omitted.
[0027]
Further, an outside air introduction pipe 28 is connected between the second fuel supply pipe 33 and the startup steady operation switching valve 34 in the fuel discharge pipe 30. An electromagnetic valve 28a for introducing outside air and an air filter 28b are arranged in the outside air introducing pipe 28, so that outside air can be introduced into the fuel chamber 48 when the operation of the fuel cell stack 11 ends. .
[0028]
In addition, the gas-liquid separation trap 60 is located at the lowest position of the fuel discharge line 31 to make it easy to store water.
[0029]
Here, the first fuel pressure regulating valve 25a and the second fuel pressure regulating valve 25b may be a butterfly valve, a regulator valve, a diaphragm valve, a mass flow controller, a sequence valve, or the like. Any type may be used as long as it can adjust the pressure of the hydrogen gas flowing out of the outlets of the 25a and the second fuel pressure adjusting valve 25b to a preset pressure. The pressure may be adjusted manually, but is desirably adjusted by an actuator including an electric motor, a pulse motor, an electromagnet, and the like.
[0030]
The start-up fuel supply solenoid valve 23, the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the start-up steady operation switching valve 34, the start-up exclusive exhaust valve 56a, and the drainage solenoid valve 62 are of a so-called on-off type. And is operated by an actuator composed of an electric motor, a pulse motor, an electromagnet or the like. The fuel storage means open / close valve 24 is operated manually or automatically using an electromagnetic valve. The check valve 56b exclusively for starting and the check valve 63 for drainage have a normal structure. Further, the suction circulating pump 36 and the second suction circulating pump 36a may be of any type as long as the pump is capable of forcibly discharging hydrogen gas and bringing the inside of the fuel chamber 48 into a negative pressure state. There may be.
[0031]
The air filter 28b removes dust (dust), impurities, harmful gas and the like contained in the air.
[0032]
On the other hand, air as an oxidant is supplied from an oxidant supply source 15 such as an air supply fan, an air cylinder and an air tank to the oxygen chamber 49 of the fuel cell stack 11 through the oxidant supply line 17 and the intake manifold 14. Supplied. In addition, oxygen can be used instead of air as the oxidizing agent. Then, the air discharged from the oxygen chamber 49 is discharged to the atmosphere through the exhaust manifold 12, the condenser 12a, and the oxidant discharge line 18.
[0033]
Further, a water supply nozzle 16 for spraying water to maintain the oxygen electrode (cathode electrode) 44 of the fuel cell stack 11 in a wet state is provided in the intake manifold 14. Further, the oxygen electrode 44 and the fuel electrode 43 can be cooled by the sprayed water. Further, a condenser 12a provided at an end of the exhaust manifold 12 is for condensing and removing moisture contained in air discharged from the fuel cell stack 11, and is condensed by the condenser 12a. The water thus collected is collected in the water tank 52 through the condensed water discharge pipe 19. The condensed water discharge pipe 19 is provided with a drain pump 51, and the water tank 52 is provided with a level gauge (water level gauge) 52a and a safety valve 52b. A water discharge pipe 61 is connected to the water tank 52, and the water discharged from the gas-liquid separation trap 60 is also collected in the water tank 52.
[0034]
Then, the water in the water tank 52 is supplied to the water supply nozzle 16 through the water supply pipe 53. The water supply pipe 53 is provided with a water supply pump 54 and a water filter 55.
[0035]
Here, the drainage pump 51 and the water supply pump 54 may be of any type 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 and the like contained in water.
[0036]
The secondary battery as the power storage means is a so-called battery (storage battery), and is generally a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, or the like. The power storage means may not necessarily be a battery, and may store and discharge energy electrically, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, a pressure accumulator, and the like. Any form may be used as long as it has a function. Further, any of these may be used alone or a plurality of them may be used in combination.
[0037]
The fuel cell stack 11 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 a drive motor that converts a DC current from the fuel cell stack 11 or the power storage unit into an AC current to rotate wheels of the vehicle. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current during the deceleration operation of the vehicle. In this case, since the drive motor is rotated by the wheels to generate power, the drive motor brakes the wheels, 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.
[0038]
In the present embodiment, the fuel cell system has control means (not shown). The control means includes arithmetic means such as a CPU and an 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 chamber 48 and the oxygen chamber 49 of the fuel cell stack 11. By detecting the flow rate, temperature, output voltage and the like of hydrogen, oxygen, air, etc., the oxidant supply source 15, the first fuel pressure regulating valve 25a, the second fuel pressure regulating valve 25b, the starting fuel supply solenoid valve 23, The operation of the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the startup steady operation switching valve 34, the suction circulation pump 36, the drain pump 51, the water supply pump 54, the startup exhaust valve 56a, the drain solenoid valve 62, and the like is controlled. . Further, the control means integrally controls the operation of all devices for supplying fuel and oxidant to the fuel cell stack 11 in cooperation with other sensors and other control devices.
[0039]
Next, the configuration of the gas-liquid separation trap 60 will be described in detail.
[0040]
FIG. 3 is a diagram showing a positional relationship between the gas-liquid separation trap and the fuel cell stack according to the first embodiment of the present invention, and FIG. 4 is a diagram showing a configuration of the gas-liquid separation trap according to the first embodiment of the present invention. FIG.
[0041]
In the present embodiment, as shown in FIG. 3, the gas-liquid separation trap 60 is located below the connection port of the fuel discharge pipe 31 in the fuel cell stack 11 in the vertical direction, that is, in the vertically downward direction. It is desirable to be located. Thereby, water can be easily discharged from the fuel chamber 48 of the fuel cell stack 11.
[0042]
Incidentally, in the fuel cell system according to the present embodiment, water is not supplied to the anode electrode side unlike the conventional fuel cell disclosed in Patent Document 1. That is, the fuel cell stack 11 does not include a mechanism for supplying water to the fuel chamber 48, and the hydrogen gas supplied as fuel into the fuel chamber 48 is not humidified. In the fuel cell system according to the present embodiment, the fuel electrode 43 is humidified by the back diffusion water. In addition, the back diffusion water means that the water generated in the oxygen chamber 49 diffuses into the solid polymer electrolyte membrane 45, passes through the solid polymer electrolyte membrane 45 in the opposite direction to the hydrogen ions, and enters the fuel chamber 48. It is a thing that has permeated up to. As described above, since each cell 40 is not provided with a mechanism for supplying water to the fuel chamber 48, the configuration of the fuel cell stack 11 is simple and small. Further, since it is not necessary to add moisture to the hydrogen gas and humidify it, there is no need to provide a pipe or a control valve for introducing water into the first fuel supply pipe 21 or the second fuel supply pipe 33, The configuration is simple, and the cost can be reduced.
[0043]
Then, in the fuel chamber 48 of the fuel cell stack 11, the surplus back-diffused water mixes with the surplus hydrogen gas to form a gas-liquid mixture. The gas-liquid mixture is sucked by the suction circulation pump 36 and is led out of the fuel cell stack 11 through the fuel discharge line 31. Then, the gas-liquid mixture is introduced into the trap container 64 from above the gas-liquid separation trap 60. Then, the gas-liquid mixture is separated into hydrogen gas and back-diffused water as moisture in the trap container 64, that is, the gas-liquid separated hydrogen gas is discharged from the fuel discharge pipe 30 to the outside of the trap container 64. . The separated back-diffused water is stored as stored water 65 in the lower part of the trap container 64. In addition, a water discharge pipe 61 provided with a drainage electromagnetic valve 62 is connected to a lower portion of the trap container 64. In FIG. 3, the check valve 63 for drainage is omitted. Further, the water discharge pipe 61 and the drain solenoid valve 62 can be arranged at positions 61 'and 62' indicated by dotted lines in FIG.
[0044]
Here, the gas-liquid separation trap 60 has a configuration as shown in FIG. The trap container 64 has a cylindrical shape with a bottom, and an open upper portion is airtightly closed (blocked) by a container cover 66. The container cover 66 is fixed to the trap container 64 by a fixing member 66a such as a bolt, and a seal member 66b such as an O-ring is provided between the lower surface of the container cover 66 and the upper end surface of the trap container 64. Are provided and maintain airtightness. The fuel discharge line 31 and the fuel discharge line 30 are connected to the upper side wall of the trap container 64 at positions separated from each other.
[0045]
Further, a water level sensor 67 for measuring the water level of the stored water 65 is attached to the container cover 66. The water level sensor 67 includes a rod-shaped measuring member 67a that hangs down in the vertical direction, and measures the position of the water surface 65a of the stored water 65 as a water level. In FIG. 4, reference numerals 67b and 67c denote detection points above and below the water level corresponding to the upper and lower limits of the appropriate range of the water level. In the present embodiment, when the water level rises and exceeds the above-water level detection point 67b, the control device of the fuel cell system opens the drainage electromagnetic valve 62 to move the stored water 65 from the water discharge line 61 to the outside of the trap container 64. When the water level falls and falls below the below-water level detection point 67c, the drainage electromagnetic valve 62 is closed to stop the stored water 65 from flowing out of the trap container 64 from the water discharge pipe 61.
[0046]
The positions of the above-water detection point 67b and the below-water detection point 67c can be set arbitrarily, but the below-water detection point 67c is located at a higher position than the position where the water discharge pipe 61 is connected to the trap container 64. It is also desirable that the upper part be located above in the vertical direction. Thereby, it is possible to prevent the outflowing water from being mixed with the hydrogen gas and to improve the recovery rate of the hydrogen gas.
[0047]
Next, the operation of the fuel cell system having the above configuration will be described. Here, an operation of controlling the water level of the stored water 65 in the steady operation will be described.
[0048]
FIG. 5 is a flowchart showing an operation for controlling the level of the stored water in the first embodiment.
[0049]
During a steady operation in the fuel cell system of the present embodiment, the pressure of the hydrogen gas flowing out from the outlets of the first fuel pressure regulating valve 25a and the second fuel pressure regulating valve 25b is adjusted to a predetermined constant pressure, and The first fuel pressure adjusting valve 25a and the second fuel pressure adjusting valve 25b are not adjusted during the operation of the fuel cell system, and are kept as they are. The oxidant supply source 15 operates so as to always supply a constant amount of air to the oxygen chamber 49 of the fuel cell stack 11. In this case, the amount of supplied air is sufficiently larger than the amount of air required to maximize the output of the fuel cell stack 11.
[0050]
When the fuel cell stack 11 starts operating, reverse diffusion water is generated in each cell 40 constituting the fuel cell stack 11, and the reverse diffusion water passes through the solid polymer electrolyte membrane 45 and enters the fuel chamber 48. To humidify the fuel electrode 43 side of the solid polymer electrolyte membrane 45. As a result, the fuel electrode 43 side of the solid polymer electrolyte membrane 45 is in a wet state, and hydrogen ions generated from hydrogen by the electrochemical reaction can smoothly move in the solid polymer electrolyte membrane 45.
[0051]
The surplus hydrogen gas supplied to the fuel chamber 48 permeates into the fuel chamber 48 and mixes with surplus back-diffused water to form a gas-liquid mixture. The hydrogen gas that has become the gas-liquid mixture is sucked by the suction circulation pump 36, and is led out of the fuel cell stack 11 through the fuel discharge pipe 31 connected to the fuel cell stack 11. Then, the gas-liquid mixture passes through the fuel discharge pipe 31 and is introduced into the trap container 64. Then, by staying in the trap container 64 having a relatively large space, the heavy water content falls downward due to gravity, and the reverse diffusion water is separated from the hydrogen gas. The hydrogen gas in a state where the back diffusion water is separated and dried is discharged from the fuel discharge pipe 30 to the outside of the trap container 64. The hydrogen gas discharged from the fuel discharge pipe 30 is introduced into the second fuel supply pipe 33, and is again supplied to the fuel chamber 48 of the fuel cell stack 11 for reuse.
[0052]
Here, since the fuel discharge line 30 is connected to the side wall of the upper portion of the trap container 64, only the dry hydrogen gas in which the back-diffused water is separated and lightened can be discharged from the fuel discharge line 30. It is discharged and no water is discharged. Further, since the fuel discharge line 31 and the fuel discharge line 30 are connected to the upper side wall of the trap container 64 at positions separated from each other, the gas liquid introduced into the trap container 64 from the fuel discharge line 31 The mixture does not flow out of the fuel discharge line 30 as it is. As a result, excess back-diffused water that has penetrated into the fuel chamber 48 can be appropriately trapped, and excess hydrogen gas can be recovered in a dry state and reused.
[0053]
On the other hand, the reverse diffusion water separated and dropped from the gas-liquid mixture is stored as stored water 65 in the lower portion of the trap container 64. Here, the water level of the stored water 65 is measured by the water level sensor 67, that is, the water level is detected by the water level sensor 67 (step S1). Then, as the fuel cell stack 11 continues to operate, the amount of water separated from the gas-liquid mixture led out of the fuel cell stack 11 increases, and the water level of the stored water 65 gradually rises. When the control device of the fuel cell system determines that the water level of the stored water 65 has exceeded the water level detection point 67b (step S2), the electromagnetic valve 62 for drainage is opened to open the water discharge pipe 61, and the stored water is opened. 65 is discharged from the water discharge pipe 61 to the outside of the trap container 64 (step S3). Thereby, the water level of the storage water 65 gradually decreases. When the control device of the fuel cell system determines that the water level of the stored water 65 has fallen below the water level detection point 67c (step S4), it closes the drainage electromagnetic valve 62, closes the water discharge line 61, and stores the stored water. The flow of water 65 out of the trap container 64 from the water discharge pipe 61 is stopped (step S5). Thereafter, by repeating such an operation, the water level of the stored water 65 can be maintained between the above-water level detection point 67b and the below-water level detection point 67c.
[0054]
Note that the reverse diffusion water flowing out of the trap container 64 from the water discharge pipe 61 is collected in the water tank 52. This makes it possible to effectively reuse the surplus back-diffused water.
[0055]
As described above, in the present embodiment, the gas-liquid mixture of the back-diffused water and the hydrogen gas that has become excessive in the fuel chamber 48 is sucked by the suction circulation pump 36 and discharged to the outside of the fuel cell stack 11. It has become. Therefore, the flow of hydrogen gas in the fuel chamber 48 can be prevented from being clogged by excess back-diffusion water, and the hydrogen gas as fuel can be stably supplied to the surface of the fuel electrode 43. it can.
[0056]
Further, surplus back-diffused water is separated from hydrogen gas by the gas-liquid separation trap 60 and collected in the water tank 52, so that it can be effectively reused. This makes it possible to compensate for the shortage of water to be sprayed for humidifying the oxygen electrode 44 of the fuel cell stack 11, and to reduce the size and weight of the water tank 52.
[0057]
Further, since the reverse diffusion water mixed with the surplus hydrogen gas is separated by the gas-liquid separation trap 60, the surplus hydrogen gas can be collected and reused. Thereby, the fuel consumption of the fuel cell stack 11 can be suppressed.
[0058]
Further, since the water level is detected by the water level sensor 67 and the water level of the stored water 65 in the trap container 64 can be appropriately controlled, the amount of the stored water 65 is reduced, and the size of the gas-liquid separation trap 60 is reduced. be able to.
[0059]
Further, since the fuel electrode 43 is humidified by the back diffusion water and each cell 40 does not have a mechanism for supplying water to the fuel chamber 48, the configuration of the fuel cell stack 11 can be simplified and downsized. . Further, since it is not necessary to add moisture to the hydrogen gas and humidify it, there is no need to provide a pipe or a control valve for introducing water into the first fuel supply pipe 21 or the second fuel supply pipe 33, The configuration of the fuel cell system can be simplified, and the cost can be reduced.
[0060]
Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. The description of the same operation and effect as those of the first embodiment is omitted.
[0061]
FIG. 6 is a diagram illustrating a configuration of a gas-liquid separation trap according to a second embodiment of the present invention. FIG. 7 is a diagram illustrating a change in water recovery amount of the gas-liquid separation trap according to the second embodiment of the present invention. FIG. 8 is a diagram showing the time when the solid polymer electrolyte membrane according to the second embodiment of the present invention is wet, and FIG. 9 is a diagram showing the time when the solid polymer electrolyte membrane according to the second embodiment of the present invention is wet. FIG. 10 shows a change in the amount of water collected by the liquid separation trap, FIG. 10 shows a change in the amount of water flowing out from the gas-liquid separation trap in the second embodiment of the present invention, and FIG. It is a flowchart which shows the operation | movement which controls the water level of the stored water in the form of FIG.
[0062]
As shown in FIG. 6, the gas-liquid separation trap 60 according to the present embodiment does not include the water level sensor 67, and the fuel discharge line 31 is not provided on the side wall of the trap container 64 but on the container cover 66. It differs from the first embodiment in that it is connected. Therefore, the control device of the fuel cell system controls the operation of the drainage electromagnetic valve 62 according to a preset sequence in order to appropriately control the level of the stored water 65 in the trap container 64.
[0063]
First, an experiment was performed to measure a temporal change in the amount of the back-diffused water recovered from the fuel cell stack 11, and the result shown in FIG. 7 could be obtained. In FIG. 7, the vertical axis represents the amount of recovered reverse diffusion water [ml], and the horizontal axis represents time [minutes]. Here, the horizontal axis represents the time from the start of the operation of the fuel cell system, and the time 0 [minute] is the start of the operation of the fuel cell system.
[0064]
Here, the recovery amount of the back-diffused water depends on the total electrode area of the fuel cell stack 11, the current density of the fuel cell stack 11, the thickness of the solid polymer electrolyte membrane 45, and the gas diffusion constituting Ease of water permeability of electrodes, humidity in fuel chamber 48, humidity in oxygen chamber 49, pressure in fuel chamber 48, pressure in oxygen chamber 49, temperature in fuel chamber 48, temperature in oxygen chamber 49 And so on.
[0065]
Therefore, FIG. 7 shows a result of measuring a temporal change in the amount of the back diffusion water for each current density of the fuel cell stack 11. Note that the current density is a value obtained by dividing the current value output from the fuel cell stack 11 by the total electrode area of the fuel cell stack 11, and is [A / cm ² ] Is represented. In FIG. 7, a curve 71 indicates a current density of 0.1 A / cm. ² ], The change over time in the amount of reverse diffusion water recovered, curve 72 shows a current density of 0.2 [A / cm ² ], The curve 73 shows the current density of 0.3 [A / cm ² Curve 74 shows the current density of 0.4 [A / cm]. ² ], The curve 75 shows the current density of 0.5 [A / cm] ² ] Shows the change over time of the recovery amount of the back-diffused water. Note that the straight line 76 indicates the maximum amount of the stored water 65 in the trap container 64. From this, it is understood that the amount of the reverse diffusion water increases as the current density increases.
[0066]
Also, it can be seen that in the range shown by the dotted line A, the amount of the reverse diffusion water hardly increases. This can be considered to be because in the time zone immediately after the operation of the fuel cell system is started, since the solid polymer electrolyte membrane 45 is dry, the back diffusion water does not permeate into the fuel chamber 48. . Then, after a certain period of time has elapsed since the operation of the fuel cell system was started, the solid polymer electrolyte membrane 45 is in a state of being wetted by the back diffusion water. Then, the back-diffused water permeates into the fuel chamber 48, and the surplus back-diffused water is supplied to the fuel chamber 48 and mixed with the surplus hydrogen gas to form a gas-liquid mixture to form a gas-liquid mixture. And collected as stored water 65 in the trap container 64. Therefore, the recovery amount of the reverse diffusion water is measured by measuring the amount of the stored water 65 in the trap container 64.
[0067]
Then, based on the results shown in FIG. 7, it is possible to obtain the relationship between the time required until the solid polymer electrolyte membrane 45 becomes wet and the current density. Here, the result shown in FIG. 8 was obtained. In FIG. 8, the vertical axis represents time [seconds], and the horizontal axis represents current density [A / cm. ² ] Has been taken. Here, the vertical axis indicates the time from the start of the operation of the fuel cell system, and the time 0 [second] is the start of the operation of the fuel cell system.
[0068]
8, a curve 76 is a curve connecting points indicating the relationship between the time required for the solid polymer electrolyte membrane 45 to become wet and the current density obtained based on the results shown in FIG. 7, and the curve 77 is It is an approximate curve of the curve. The curve 77 can be represented by the following equation (1).
t2 = aI ² + BI + c Equation (1)
Here, t2 is the time required until the solid polymer electrolyte membrane 45 of the fuel cell stack 11 is wet, that is, the electrolyte membrane wet time [sec], and I is the average value of the current density [A / cm]. ² ]. A, b, and c are constants for drawing the curve 77. For example, the curve 77 is drawn by setting a = 3428.6, b = -4337.1, and c = 1455. I was able to.
[0069]
Further, based on the results shown in FIG. 7, it is possible to obtain the relationship between the recovery amount of the reverse diffusion water after the solid polymer electrolyte membrane 45 is wet and the current density. Here, the result shown in FIG. 9 was obtained. In FIG. 9, the vertical axis represents the recovery amount [ml] of the reverse diffusion water, and the horizontal axis represents the current density [A / cm]. ² ] Has been taken.
[0070]
In FIG. 9, a fold line 78 is a line connecting the points indicating the relationship between the amount of reverse diffusion water recovered after the solid polymer electrolyte membrane 45 is wetted and the current density obtained based on the results shown in FIG. 7. , A curve 79 is an approximate curve of the broken line 78. The curve 79 can be represented by the following equation (2).
Q1 = dI ² + EI Equation (2)
Here, Q1 is a recovery amount per unit time [ml] as a recovery amount of reverse diffusion water per unit time, and I is an average value of current density [A / cm]. ² ]. Further, d and e are constants for drawing the curve 79. For example, the curve 79 could be drawn by setting d = −0.019669 and e = 0.197775.
[0071]
Further, according to an experiment, the drainage electromagnetic valve 62 is opened to open the water discharge pipe 61, and when the stored water 65 flows out of the trap vessel 64 from the water discharge pipe 61, the stored water 65 flows out of the gas-liquid separation trap 60. When the change in the amount of water was measured, a result as shown in FIG. 10 could be obtained. In FIG. 10, the amount of water flowing out [ml] is plotted on the vertical axis, and the time [sec] during which the drain solenoid valve 62 is open is plotted on the horizontal axis.
[0072]
In this case, it can be seen that the relationship between the amount of water flowing out from the gas-liquid separation trap 60 and the time during which the drain solenoid valve 62 is open is a proportional relationship as shown by a straight line 81. From the point B on the straight line 81, it can be seen that 16 [ml] of water flows out of the gas-liquid separation trap 60 when the drain electromagnetic valve 62 is opened for 1 [second]. Therefore, for example, when the gas-liquid separation trap water storage amount Q2 [ml] as the amount of the stored water 65 in the trap container 64 exceeds a predetermined value, a sequence is set in which the drainage solenoid valve 62 is opened by 1 [second]. In this case, when the following equation (3) is satisfied, the drain solenoid valve 62 is opened for 1 second.
Q2> 16 Expression (3)
In the present embodiment, the equations (1) to (3) are stored in advance in the storage unit of the control device. The control device acquires the time, current density, and the like, and controls the operation of the drainage electromagnetic valve 62 by performing calculations based on the equations (1) to (3).
[0073]
First, the control device starts measuring an elapsed time t from the time when the operation of the fuel cell system is started, based on the time obtained from a clock (not shown) (step S11). Subsequently, the control device measures an elapsed time t1 from the end of the previous operation to the start of the current operation (step S12), and determines whether or not the t1 exceeds a predetermined value (step S12). Step S13). This is because it can be considered that the solid polymer electrolyte membrane 45 is not dry but wet in the time zone immediately after the operation of the fuel cell system is completed.
[0074]
Therefore, if the predetermined time has not elapsed since the last operation, the solid polymer electrolyte membrane 45 is wet, and the back-diffused water permeates into the fuel chamber 48 immediately after starting the current operation. However, it can be considered that surplus back-diffusion water is supplied to the fuel chamber 48. Then, the surplus back-diffused water is supplied to the fuel chamber 48 and mixed with the surplus hydrogen gas to form a gas-liquid mixture, which is led out of the fuel cell stack 11 and stored in the trap container 64. Collected as water 65. Therefore, when the predetermined time has not elapsed since the previous operation was completed, the control device performs the operation in the electrolyte membrane wet mode, which is the operation mode when the solid polymer electrolyte membrane 45 is wet. .
[0075]
On the other hand, if the predetermined time has elapsed since the previous operation was completed, since the solid polymer electrolyte membrane 45 has been dried, the back-diffused water reaches the fuel chamber 48 immediately after starting the current operation. It can be thought that it does not penetrate. In this case, the control device performs an operation in an electrolyte membrane drying mode, which is an operation mode when the solid polymer electrolyte membrane 45 is dry. The predetermined time can be appropriately set based on experiments.
[0076]
Then, in the operation in the electrolyte membrane drying mode, the control device firstly sets the current density i [A / cm ² ] Is measured (step S14). In this case, since the areas of the fuel electrode 43 and the oxygen electrode 44 in each cell 40 of the fuel cell stack 11 are known, the current density i can be obtained by measuring the current value output from the fuel cell stack 11. . The measurement of the current density i is repeatedly performed at a predetermined time period, for example, once every second.
[0077]
Subsequently, the control device calculates the average value I [A / cm of the measured current density i. ² ] Is calculated (step S15). Subsequently, the control device calculates the electrolyte membrane wetting time t2 of the fuel cell stack 11 based on the equation (1) (step S16), and determines whether the elapsed time t is less than the electrolyte membrane wetting time t2. Is determined (step S17). If the elapsed time t is shorter than the electrolyte membrane wetting time t2, it is considered that the solid polymer electrolyte membrane 45 is not yet wet, so the control device starts the operation in the electrolyte membrane drying mode first. Repeat from.
[0078]
When the elapsed time t is equal to or longer than the electrolyte membrane wetting time t2, it is considered that the solid polymer electrolyte membrane 45 is wet, and the control device starts the operation in the electrolyte membrane wet mode. . In this case, the control device firstly sets the current density i [A / cm ² ] Is measured (step S18). The measurement of the current density i is repeatedly performed at a predetermined time period, for example, once every second. Subsequently, the control device calculates the average value I [A / cm of the measured current density i. ² ], And the per-unit-time equivalent collection amount Q1 [ml] is calculated based on the above equation (2) (step S19).
[0079]
Subsequently, the control device updates the gas-liquid separation trap water storage amount Q2 by adding the unit time equivalent recovery amount Q1 to the previously calculated gas-liquid separation trap water storage amount Q2 (step S20). The first-stage gas-liquid separation trap water storage amount Q2 is a reset value and is 0.
[0080]
Subsequently, the control device determines whether or not the updated gas-liquid separation trap water storage amount Q2 exceeds a predetermined value (step S21). The predetermined value is 16 [ml] in accordance with the above equation (3). If the water storage amount Q2 of the gas-liquid separation trap does not exceed the predetermined value, there is no need to open the drain solenoid valve 62, and the control device repeats the operation in the electrolyte membrane wet mode from the beginning. If the water storage amount Q2 of the gas-liquid separation trap exceeds a predetermined value, the control device opens the drain solenoid valve 62 for a predetermined time (step S22). Note that the predetermined time is 1 [second] in accordance with the equation (3). Next, the control device resets the gas-liquid separation trap water storage amount Q2 to 0 (step S23). Thereafter, the controller repeats the operation in the electrolyte membrane wet mode from the beginning.
[0081]
As described above, in the present embodiment, the operation of the drainage electromagnetic valve 62 is controlled in accordance with a sequence set based on the properties of the back-diffusion water. Therefore, even if the gas-liquid separation trap 60 does not include the water level sensor 67 as in the first embodiment, the water level of the stored water 65 in the trap container 64 can be appropriately controlled, and the stored water By reducing the amount of 65, the size of the gas-liquid separation trap 60 can be reduced.
[0082]
Further, since the water level sensor 67 as in the first embodiment is provided, the configuration of the gas-liquid separation trap 60 can be simplified, and the cost can be reduced. Further, the position at which the fuel discharge line 31 or the fuel discharge line 30 is connected to the trap container 64 can be freely determined without considering the position of the water level sensor 67 as in the first embodiment. Therefore, the gas-liquid separation performance can be improved.
[0083]
Next, a third embodiment of the present invention will be described. In addition, about what has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol. The description of the same operations and effects as those of the first and second embodiments will be omitted.
[0084]
FIG. 12 is a conceptual diagram of a fuel cell system according to the third embodiment of the present invention.
[0085]
In the present embodiment, the reverse diffusion water separated from the gas-liquid mixture by the gas-liquid separation trap 60 is discharged to the outside without being collected in the water tank 52. Therefore, as shown in FIG. 12, a water discharge line 61 is connected to a portion between the muffler 56c and the start-only exhaust valve 56a in the start-up fuel discharge line 56. In this embodiment, the check valve 56b dedicated for activation is omitted. In FIG. 12, the fuel storage means 13, the exhaust manifold 12, the condenser 12a, the water tank 52, and the like are omitted. However, in the fuel cell system according to the present embodiment, the water discharge pipe 61 has It has the same configuration as that of the first and second embodiments except that it is not connected to the water tank 52 but is connected to the fuel discharge line 56 dedicated for starting.
[0086]
Thus, in the present embodiment, since the water discharge pipe 61 is not connected to the water tank 52, the piping of the water discharge pipe 61 can be simplified. Therefore, the configuration of the fuel cell system can be simplified, and the cost can be reduced.
[0087]
It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.
[0088]
【The invention's effect】
As described in detail above, according to the present invention, in a fuel cell system, an electrolyte membrane, a fuel electrode and an oxygen electrode sandwiching the electrolyte membrane, a fuel chamber in contact with the fuel electrode, and the oxygen electrode A fuel cell having an oxygen chamber in contact therewith, wherein water is back-diffused from the oxygen electrode to the fuel electrode in the electrolyte membrane to maintain the wet state, and a fuel gas is connected to the fuel chamber and supplies fuel gas to the fuel chamber A fuel supply pipe connected to the fuel chamber, a fuel discharge pipe connected to the fuel chamber for discharging fuel gas from the fuel chamber, and a fuel discharge pipe arranged in the fuel discharge pipe and discharged from the fuel chamber. A gas-liquid separation trap for separating the trapped back-diffused water, and a fuel gas connected to the gas-liquid separation trap and the fuel supply pipe, and introducing the fuel gas discharged from the gas-liquid separation trap into the fuel supply pipe. Having a fuel discharge line
[0089]
In this case, when the fuel gas mixed with the excess back-diffused water in the fuel chamber is discharged to the outside of the fuel cell, the water and the fuel gas are separated by the gas-liquid separation trap. Can be recovered and reused, and only water can be selectively discharged. Thereby, the fuel consumption of the fuel cell can be suppressed.
[0090]
Furthermore, since there is no mechanism for humidifying the fuel electrode with the back diffusion water and supplying water to the fuel chamber, the configuration of the fuel cell can be simplified and downsized. Also, since it is not necessary to add moisture to the fuel and humidify it, there is no need to arrange piping or control valves for introducing water into the fuel supply line, simplifying the structure of the fuel cell system and reducing costs. can do.
[0091]
In another fuel cell system, the fuel cell system further includes a drainage pipe connected to the gas-liquid separation trap and having a drainage on-off valve. Control the amount of back-diffusion water stored in the liquid separation trap.
[0092]
In this case, the amount of the reverse diffusion water stored in the gas-liquid separation trap can be appropriately controlled, so that the amount of the stored reverse diffusion water can be reduced, and the size of the gas-liquid separation trap can be reduced. it can.
[0093]
In still another fuel cell system, the gas-liquid separation trap further includes a water level sensor, and the drainage on-off valve opens and closes the drainage pipe based on the water level detected by the water level sensor.
[0094]
In this case, since the level of the reverse diffusion water stored in the gas-liquid separation trap is measured, the amount of the reverse diffusion water can be appropriately controlled.
[0095]
In still another fuel cell system, the drainage on-off valve opens and closes the drainage line in accordance with a sequence set based on the properties of the back diffusion water.
[0096]
In this case, since the water level sensor is provided, the configuration of the gas-liquid separation trap can be simplified, and the cost can be reduced. Further, the position at which the fuel discharge pipe and the drain pipe are connected to the gas-liquid separation trap can be freely determined, so that the gas-liquid separation performance can be improved.
[0097]
In still another fuel cell system, the drain pipe is further connected to a water tank, and the reverse diffusion water discharged from the gas-liquid separation trap is collected in the water tank.
[0098]
In this case, the surplus back-diffused water can be effectively reused.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a fuel cell system according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a configuration of a unit unit of the fuel cell according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a positional relationship between a gas-liquid separation trap and a fuel cell stack according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a configuration of a gas-liquid separation trap according to the first embodiment of the present invention.
FIG. 5 is a flowchart showing an operation of controlling the level of the stored water according to the first embodiment.
FIG. 6 is a diagram illustrating a configuration of a gas-liquid separation trap according to a second embodiment of the present invention.
FIG. 7 is a diagram showing a change in a water recovery amount of a gas-liquid separation trap according to a second embodiment of the present invention.
FIG. 8 is a diagram illustrating a time when a solid polymer electrolyte membrane according to a second embodiment of the present invention is wet.
FIG. 9 is a diagram showing a change in the amount of water recovered by a gas-liquid separation trap when the solid polymer electrolyte membrane in the second embodiment of the present invention is wet.
FIG. 10 is a diagram showing a change in the amount of water flowing out of a gas-liquid separation trap according to a second embodiment of the present invention.
FIG. 11 is a flowchart showing an operation for controlling the level of stored water in the second embodiment of the present invention.
FIG. 12 is a conceptual diagram of a fuel cell system according to a third embodiment of the present invention.
[Explanation of symbols]
11 Fuel cell stack
21 First fuel supply line
30, 31 fuel discharge line
33 Second fuel supply line
43 Fuel electrode
44 Oxygen electrode
48 Fuel Chamber
49 oxygen chamber
52 water tank
60 gas-liquid separation trap
61 Water discharge pipeline
62 Solenoid valve for drainage
67 Water level sensor

Claims (5)

(A) an electrolyte membrane, a fuel electrode and an oxygen electrode sandwiching the electrolyte membrane, a fuel chamber in contact with the fuel electrode, and an oxygen chamber in contact with the oxygen electrode; On the other hand, a fuel cell in which water is back-diffused to maintain its wet state,
(B) a fuel supply pipe connected to the fuel chamber and supplying fuel gas to the fuel chamber; and (c) a fuel discharge pipe connected to the fuel chamber and discharging fuel gas from the fuel chamber. (D) a gas-liquid separation trap that is disposed in the fuel discharge pipe and separates back-diffused water incorporated in the fuel gas discharged from the fuel chamber;
(E) a fuel discharge line connected to the gas-liquid separation trap and the fuel supply line, and introducing a fuel gas discharged from the gas-liquid separation trap into the fuel supply line. Fuel cell system. (A) having a drain pipe connected to the gas-liquid separation trap and having a drain on-off valve,
(B) The fuel cell system according to claim 1, wherein the drainage on-off valve opens and closes the drainage pipe to control the amount of the back-diffused water stored in the gas-liquid separation trap. (A) the gas-liquid separation trap includes a water level sensor;
(B) The fuel cell system according to claim 2, wherein the drainage on-off valve opens and closes the drainage pipe based on a water level detected by the water level sensor. The fuel cell system according to claim 2, wherein the drainage on-off valve opens and closes the drainage line in accordance with a sequence set based on a property of the back-diffusion water. (A) the drainage line is connected to a water tank;
(B) The fuel cell system according to any one of claims 1 to 4, wherein the reverse diffusion water discharged from the gas-liquid separation trap is collected in the water tank.

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