JP2006120438A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently exhaust produced water from a fuel cell stack and enhance fuel economy. <P>SOLUTION: The fuel cell system 10 is equipped with a fuel cell stack 12, a vapor liquid separator 64 communicating with a fuel gas outlet communicating hole 32b of the fuel cell stack 12 through a fuel gas exhausting passage 62, a first drain passage 66 communicating with the fuel gas outlet communicating hole 32b separately from the fuel gas exhaust passage 62 and communicating with the vapor liquid separator 64 through a valve unit 68, and a second drain passage 82 exhausting mainly liquid drops from the vapor liquid separator 64. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides an internal manifold in which an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the stacking direction. The present invention relates to a fuel cell system including a fuel cell stack.

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

  In this fuel cell, a fuel gas, for example, a gas mainly containing hydrogen (hereinafter also referred to as hydrogen-containing gas) is supplied to the anode side electrode, while an oxidant gas, for example, A gas or air mainly containing oxygen (hereinafter also referred to as oxygen-containing gas) is supplied. In the fuel gas supplied to the anode side electrode, hydrogen is ionized on the electrode catalyst and moves to the cathode side electrode side through the electrolyte membrane. Electrons generated during that time are taken out to an external circuit and used as direct current electric energy.

  By the way, since the operation temperature of the polymer electrolyte fuel cell is relatively low (˜100 ° C.), moisture that has not been absorbed by the electrolyte membrane after being introduced into the fuel cell stack, or moisture generated by the reaction is present. A reaction gas that is a manifold that passes through the fuel cell stack in the stacking direction and communicates with the reaction gas passage in the reaction gas passage (oxidant gas passage and / or fuel gas passage) of the fuel cell stack It is cooled in the communication hole (oxidant gas communication hole and / or fuel gas communication hole) and tends to exist in a liquid state.

  However, as described above, when water is present in the reaction gas flow path and the reaction gas communication hole of the fuel cell stack, it becomes difficult to sufficiently supply the oxidant gas and the fuel gas to each unit cell. Thereby, the problem that the diffusibility to the electrode catalyst layer of the fuel gas and oxidizing gas which are reaction gas falls and the power generation performance deteriorates remarkably is pointed out.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. As shown in FIG. 6, the fuel cell system 1 includes a solid electrolyte fuel cell 2. The fuel cell 2 includes a fuel system 3 that supplies hydrogen gas and an air system that supplies air as an oxidant gas. 4 and a cooling water circulation system 5 for circulating and supplying cooling water are connected.

  The fuel system 3 supplies the hydrogen gas in the hydrogen storage alloy tank 6 to the fuel cell 2 through the hydrogen supply pipe 7. Excess hydrogen gas discharged from the fuel cell 2 is sent to the gas-liquid separator 8 where water mixed in the hydrogen gas is stored as condensed water, while the hydrogen gas in the gas-liquid separator 8 is pumped. 9 circulates to the hydrogen supply pipe 7. For this reason, the moisture contained in the surplus hydrogen gas discharged from the fuel cell 2 is stored in the gas-liquid separator 8 as condensed water, and the hydrogen gas from which the moisture has been removed is again used as the fuel gas as the fuel. It is assumed that the battery 2 is supplied.

JP-A-7-192743 (FIG. 5)

  However, in Patent Document 1 described above, surplus hydrogen gas discharged from the fuel cell 2 is easily introduced into the gas-liquid separator 8 while being mixed in a large amount of product water. For this reason, there is a problem that a considerable amount of hydrogen gas is mixed into the condensed water in the gas-liquid separator 8, and the consumption of hydrogen gas increases, resulting in a reduction in fuel consumption.

  Moreover, if a large amount of hydrogen gas is mixed in the condensed water stored in the gas-liquid separator 8, the diluted gas supply amount by the air system 5 is increased when the condensed water is diluted and discharged to the outside. It is necessary to let As a result, power consumption of an oxidant gas supply pump, a supercharger, or the like increases, which may cause a reduction in fuel consumption.

  The present invention solves this type of problem, and an object of the present invention is to provide a fuel cell system capable of efficiently discharging generated water from a fuel cell stack and improving fuel efficiency.

  The present invention provides a fuel cell in which an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the stacking direction. A gas-liquid separation mechanism that communicates with the stack, a fuel gas outlet that is one of the reaction gas outlets, via an exhaust gas passage that is exposed to the outside of the fuel cell stack; And a first drain for mainly discharging droplets from the fuel gas discharge port to the gas-liquid separation mechanism. A flow path and a second drain flow path that communicates with the gas-liquid separation mechanism and mainly discharges liquid droplets from the gas-liquid separation mechanism.

  In addition, it is preferable to include a dilution mechanism that communicates with the second drain channel and mainly discharges droplets from the gas-liquid separation mechanism, and a dilution fluid supply unit that supplies the dilution fluid to the dilution mechanism. This is because the fuel gas contained in the droplets discharged from the second drain channel can be effectively diluted.

  Furthermore, in the present invention, an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas inlet and a reaction gas discharge port are formed through the stacking direction. A gas-liquid separation mechanism communicating with a fuel cell stack and a fuel gas discharge port, which is one of the reaction gas discharge ports, through an exhaust gas passage exposed to the outside of the fuel cell stack, and mainly from the gas-liquid separation mechanism A dilution mechanism that discharges droplets, a dilution fluid supply unit that supplies a dilution fluid to the dilution mechanism, and one end of a flow path that communicates with the fuel gas discharge port separately from the exhaust gas flow path. The other end communicates with the dilution mechanism, communicates from the fuel gas discharge port to the dilution mechanism with a first drain channel for mainly discharging droplets, the gas-liquid separation mechanism, and the dilution mechanism, and From liquid separation mechanism A serial dilution mechanism, and a second drain channel which mainly discharged liquid droplets.

  Furthermore, it is preferable that a flow rate control mechanism is disposed in the first and second drain channels. By operating the flow rate control mechanism, the first and second drain channels are opened and closed, and drainage control is reliably performed. For this reason, when the generated water is not accumulated up to a predetermined amount, the fuel gas is not passed unnecessarily, which is economical.

  In the present invention, an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are laminated, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the lamination direction. A fuel gas stack, which is one of the reaction gas discharge ports, communicates with a fuel gas discharge port, which is one of the reaction gas discharge ports, via an exhaust gas flow passage exposed to the outside of the fuel cell stack. The fuel gas circulation path that circulates to the mouth and the fuel gas circulation path are individually communicated with the fuel gas discharge port and exposed to the outside of the fuel cell stack, and droplets are mainly discharged from the fuel gas discharge port. A first drain passage and a flow rate control mechanism disposed in the first drain passage;

  Further, it is preferable that the fuel gas circulation path is provided with a gas-liquid separation mechanism, and the second drain flow path is communicated with the gas-liquid separation mechanism via a flow rate control mechanism. This is because the generated water stored in the gas-liquid separation mechanism can be reliably discharged through the second drain channel.

  Furthermore, it is preferable to include a dilution mechanism connected to the gas-liquid separation mechanism via the second drain flow path, and a dilution fluid supply unit that supplies the dilution fluid to the dilution mechanism.

  This is because the fuel gas contained in the water discharged from the second drain channel can be effectively diluted.

  According to the present invention, the generated water (water droplets) at the fuel gas discharge port is discharged to the first drain channel mainly including the waste water and supplied to the gas-liquid separation mechanism. For this reason, the amount of water in the fuel gas discharge port is effectively reduced, and the exhaust gas (excess fuel gas) discharged from the fuel gas discharge port to the exhaust gas flow path is not so much mixed into the generated water. As a result, the amount of fuel gas discarded unnecessarily is favorably reduced, the consumption amount of fuel gas can be reduced, and the fuel consumption can be improved.

  Further, in the present invention, the generated water at the fuel gas discharge port is discharged to the first drain passage mainly including the waste water and supplied to the dilution mechanism. Therefore, the exhaust gas discharged from the fuel gas discharge port to the exhaust gas passage is not mixed so much with the generated water, and the amount of fuel gas discarded unnecessarily is favorably reduced.

  Moreover, since the amount of fuel gas mixed in the droplets discharged to the dilution mechanism is small, the flow rate of the dilution fluid (for example, air) supplied to the dilution mechanism can be set to be smaller. This is because the concentration of the fuel gas is low. Thereby, power consumption of a fan, a supercharger, or the like for supplying the diluted fluid can be suppressed, and fuel consumption can be easily improved.

  Furthermore, in the present invention, the generated water at the fuel gas discharge port is discharged well from the first drain flow path, and it becomes possible to eliminate the gas-liquid separation mechanism and the dilution mechanism. For this reason, the number of components is greatly reduced, and the configuration of the entire fuel cell system can be easily simplified and economical.

  FIG. 1 is a schematic explanatory diagram of a fuel cell system 10 according to a first embodiment of the present invention.

  The fuel cell system 10 includes a fuel cell stack 12. In the fuel cell stack 12, a plurality of unit cells 14 are stacked in the horizontal direction (arrow A direction), and at one end in the stacking direction, a terminal plate 16a, an insulating plate 18a, and a first end plate 20a face outward. Are arranged sequentially. At the other end in the stacking direction of the unit cells 14, a terminal plate 16b, an insulating plate 18b, and a second end plate 20b are sequentially arranged outward.

  As shown in FIGS. 1 and 2, each unit cell 14 includes an electrolyte membrane / electrode structure (electrolyte / electrode structure) 22, and a thin plate-shaped first and second sandwiching the electrolyte membrane / electrode structure 22. Second metal separators 24 and 26 are provided. Instead of the first and second metal separators 24 and 26, for example, a carbon separator may be employed.

  One end edge of the unit cell 14 in the long side direction (in the direction of arrow B in FIG. 2) communicates with each other in the direction of arrow A to supply an oxidant gas (introduction port). 28a, a cooling medium inlet communication hole 30a for supplying the cooling medium, and a fuel gas outlet communication hole (discharge port) 32b for discharging the fuel gas are provided.

  The other end edge of the unit cell 14 in the long side direction communicates with each other in the direction of the arrow A, a fuel gas inlet communication hole (inlet port) 32a for supplying fuel gas, and cooling for discharging the cooling medium A medium outlet communication hole 30b and an oxidant gas outlet communication hole (discharge port) 28b for discharging the oxidant gas are provided.

  The electrolyte membrane / electrode structure 22 includes, for example, a solid polymer electrolyte membrane 34 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 36 and a cathode side electrode 38 that sandwich the solid polymer electrolyte membrane 34. With.

  The anode side electrode 36 and the cathode side electrode 38 are uniformly coated on the surface of the gas diffusion layer with a gas diffusion layer (not shown) made of carbon paper or the like and porous carbon particles carrying a platinum alloy on the surface. And an electrode catalyst layer (not shown) formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 34.

  A fuel gas flow path 40 that connects the fuel gas inlet communication hole 32a and the fuel gas outlet communication hole 32b is formed on the surface 24a of the first metal separator 24 facing the electrolyte membrane / electrode structure 22. A cooling medium flow path 42 that connects the cooling medium inlet communication hole 30 a and the cooling medium outlet communication hole 30 b is formed on the surface 24 b of the first metal separator 24.

  The surface 26a of the second metal separator 26 facing the electrolyte membrane / electrode structure 22 is provided with an oxidant gas flow path 44. The oxidant gas flow path 44 is connected to the oxidant gas inlet communication hole 28a and the oxidant. It communicates with the gas outlet communication hole 28b. A cooling medium flow path 42 is integrally formed on the surface 26 b of the second metal separator 26 so as to overlap the surface 24 b of the first metal separator 24.

  On the surfaces 24a and 24b of the first metal separator 24, a first seal member 46 is integrally formed around the outer peripheral edge of the first metal separator 24, and the surfaces 26a and 26b of the second metal separator 26 are integrally formed. The second seal member 48 is integrally molded around the outer peripheral edge of the second metal separator 26.

  As shown in FIG. 1, the fuel cell stack 12 includes a fuel gas supply system 50, an oxidant gas supply system 52, and a cooling medium supply system (not shown). The fuel gas supply system 50 includes a hydrogen tank 54, and the hydrogen tank 54 is connected to a fuel gas circulation path 60 through a valve 56 and an ejector 58. The fuel gas circulation path 60 is connected to the fuel gas inlet communication hole 32a of the first end plate 20a.

  The fuel gas outlet communication hole 32 b of the first end plate 20 a communicates with a gas-liquid separator (gas-liquid separation mechanism) 64 via a fuel gas discharge channel (exhaust gas channel) 62. This gas-liquid separator 64 communicates with the ejector 58.

  A first drain passage 66 communicating with the gas-liquid separator 64 separately from the fuel gas discharge passage 62 is connected to the fuel gas outlet communication hole 32b of the second end plate 20b. That is, the first drain channel 66 is provided on the fuel cell stack 12 on the side opposite to the fuel gas discharge channel 62. Thereby, even when the fuel cell stack 12 is inclined, effective drainage is performed.

  The first drain passage 66 is preferably disposed below the fuel gas discharge passage 62 with respect to the fuel gas outlet communication hole 32 b and is set to have a smaller diameter than the fuel gas discharge passage 62. As a result, the amount of fuel gas mixed into the first drain channel 66 can be minimized. The first drain channel 66 is provided with a valve unit 68 in the vicinity of the fuel gas outlet communication hole 32b.

  As shown in FIG. 3, the valve unit 68 is disposed in the first drain channel 66, and a sensor for detecting that a predetermined amount of liquid has accumulated in the first drain channel 66, for example, a static unit. A capacitance sensor 70, a valve 72 that is disposed in the vicinity of the capacitance sensor 70 and opens and closes the first drain channel 66, and controls the valve 72 based on a signal from the capacitance sensor 70. And a control unit 74. As the sensor, various sensors capable of detecting the presence or absence of liquid droplets in the tube, such as an ultrasonic sensor, can be used instead of the capacitance sensor 70.

  As shown in FIG. 1, a purge flow path 76 branches from between the gas-liquid separator 64 and the ejector 58, and this purge flow path 76 is connected to a dilution box (dilution mechanism) 80 via a valve 78. . The gas / liquid separator 64 is connected to a second drain channel 82 for mainly discharging water from the gas / liquid separator 64 as necessary, and the second drain channel 82 is connected to the valve unit 84. To the dilution box 80. The valve unit 84 is configured similarly to the valve unit 68.

  The oxidant gas supply system 52 includes an oxidant gas supply path 86 that communicates with the oxidant gas inlet communication hole 28a of the first end plate 20a. The oxidant gas supply path 86 is supplied with pressurized air, for example, via a compressor (not shown). A dilution gas flow path 88 is connected to the oxidant gas outlet communication hole 28b of the first end plate 20a, and the dilution gas flow path 88 communicates with the dilution box 80.

  The operation of the fuel cell system 10 configured as described above will be described below.

  First, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas, for example, an oxygen-containing gas is introduced into the oxidant gas inlet communication hole 28a of the first end plate 20a constituting the fuel cell stack 12 via the oxidant gas supply system 52. Air is supplied. On the other hand, the hydrogen tank 54 constituting the fuel gas supply system 50 supplies a fuel gas such as a hydrogen-containing gas to the fuel gas circulation path 60 via the valve 56. This fuel gas is supplied to the fuel gas inlet communication hole 32a of the first end plate 20a.

  Furthermore, a cooling medium such as pure water, ethylene glycol, or oil is circulated and supplied to the cooling medium inlet communication hole 30a of the first end plate 20a through a cooling medium supply system (not shown).

  As shown in FIG. 2, in the fuel cell stack 12, oxidant gas is introduced from the oxidant gas inlet communication hole 28 a into the oxidant gas flow path 44 of the second metal separator 26, and the electrolyte membrane / electrode structure 22. It moves along the cathode side electrode 38. On the other hand, the fuel gas is introduced into the fuel gas flow path 40 of the first metal separator 24 from the fuel gas inlet communication hole 32 a and moves along the anode side electrode 36 of the electrolyte membrane / electrode structure 22.

  Therefore, in each electrolyte membrane / electrode structure 22, the oxidant gas supplied to the cathode side electrode 38 and the fuel gas supplied to the anode side electrode 36 are consumed by an electrochemical reaction in the electrode catalyst layer, Power generation is performed.

  The cooling medium flows in the direction of arrow B after being introduced into the cooling medium flow path 42 between the first and second metal separators 24, 26. The cooling medium cools the electrolyte membrane / electrode structure 22, then moves through the cooling medium outlet communication hole 30 b and is discharged to a circulation channel (not shown) connected to the first end plate 20 a for circulation.

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 38 flows along the oxidant gas outlet communication hole 28b, and is then discharged to the dilution gas flow path 88 connected to the first end plate 20a. (See FIG. 1). Similarly, the fuel gas consumed by being supplied to the anode side electrode 36 is discharged to the fuel gas outlet communication hole 32b, flows, and discharged to the fuel gas discharge path 62 connected to the first end plate 20a.

  In this case, in the first embodiment, the first drain passage 66 is connected to the end of the fuel gas outlet communication hole 32b on the second end plate 20b side, and the height of the first drain passage 66 is increased. The position is set lower than the height position of the fuel gas discharge path 62. Therefore, the generated water in the fuel gas outlet communication hole 32 b is smoothly discharged to the first drain channel 66 and supplied to the gas-liquid separator 64 under the action of the valve unit 68.

  In the valve unit 68, as shown in FIG. 3, the first drain channel 66 is previously closed via the valve 72, and the capacitance sensor 70 determines the amount of water discharged into the first drain channel 66. To detect. When the detected amount of water reaches a predetermined amount, the valve 72 is opened via the control unit 74. For this reason, the generated water in the first drain channel 66 is reliably introduced into the gas-liquid separator 64 by the pressure of the compressed hydrogen gas supplied into the fuel cell stack 12.

  Thereby, the surplus fuel gas discharged from the fuel gas outlet communication hole 32b to the fuel gas discharge passage 62 is not mixed so much into the generated water because the amount of generated water is reduced. Accordingly, the amount of fuel gas mixed into the produced water and stored in the gas-liquid separator 64 is reduced well, and surplus fuel gas is effectively supplied from the gas-liquid separator 64 to the fuel gas circulation path 60 via the ejector 58. Supplied. For this reason, in 1st Embodiment, the consumption of fuel gas can be reduced and the effect that it becomes possible to aim at the improvement of a fuel consumption is acquired.

  Furthermore, in the first embodiment, the gas-liquid separator 64 is connected to the dilution box 80 via the second drain channel 82, and the valve unit 84 is disposed in the second drain channel 82. Has been. Thereby, produced water can be reliably discharged from the gas-liquid separator 64 to the dilution box 80. In addition, even when fuel gas is mixed in the generated water discharged from the gas-liquid separator 64, it is possible to dilute well with the used air introduced into the dilution box 80 via the dilution gas flow path 88. Become.

  Further, since the amount of fuel gas mixed in the water discharged from the gas-liquid separator 64 to the dilution box 80 is small, the flow rate of the dilution gas (air) supplied to the dilution box 80 is reduced. Therefore, power consumption of a compressor, a fan, and the like for sending the air discharged from the oxidant gas outlet communication hole 28b as dilution gas to the dilution box 80 can be suppressed, and fuel consumption can be easily improved.

  FIG. 4 is a schematic explanatory diagram of a fuel cell system 90 according to the second embodiment of the present invention.

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

  The fuel cell system 90 includes a first drain channel 92 that communicates with the fuel gas outlet communication hole 32 b of the second end plate 20 b and the dilution box 80. A valve unit 68 is disposed in the first drain channel 92 in the vicinity of the fuel gas outlet communication hole 32b. The first drain channel 92 is configured in the same manner as the first drain channel 66.

  In the second embodiment configured as described above, the generated water in the fuel gas outlet communication hole 32 b is discharged from the first drain channel 92 to the dilution box 80. For this reason, the amount of water discharged from the fuel gas outlet communication hole 32 b to the gas-liquid separator 64 via the fuel gas discharge path 62 is reduced, and the fuel gas mixed in this water and staying in the gas-liquid separator 64 is retained. The amount is reduced well. Therefore, the same effects as those of the first embodiment can be obtained, for example, the fuel gas consumption can be reduced and the fuel consumption can be improved.

  FIG. 5 is a schematic explanatory diagram of a fuel cell system 100 according to the third embodiment of the present invention.

  The fuel cell system 100 includes a first drain channel 102 that is connected to the fuel gas outlet communication hole 32b of the second end plate 20b and can be opened to the outside. A valve unit 68 is provided in the first drain channel 102. The gas-liquid separator 64 and / or the dilution box 80 may be used as necessary, and may be unnecessary.

  In this fuel cell system 100, the generated water in the fuel gas outlet communication hole 32 b is discharged well from the first drain channel 102 to the outside. For this reason, the amount of water contained in the surplus fuel gas discharged to the fuel gas discharge path 62 can be favorably reduced, and the same effect as in the first and second embodiments can be obtained.

  Moreover, since the generated water is discharged from the first drain channel 102 to the outside, the gas-liquid separator 64 and the dilution box 80 can be eliminated. As a result, the fuel cell system 100 has the advantage that the number of components is greatly reduced, and the overall configuration of the fuel cell system 100 is well simplified and economical.

1 is a schematic explanatory diagram of a fuel cell system according to a first embodiment of the present invention. It is a disassembled perspective explanatory drawing of the unit cell which comprises the said fuel cell system. It is explanatory drawing of the valve unit which comprises the said fuel cell system. It is a schematic explanatory drawing of the fuel cell system which concerns on the 2nd Embodiment of this invention. It is a schematic explanatory drawing of the fuel cell system which concerns on the 3rd Embodiment of this invention. 2 is an explanatory diagram of a fuel cell system of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 90, 100 ... Fuel cell system 12 ... Fuel cell stack 14 ... Unit cell 20a, 20b ... End plate 22 ... Electrolyte membrane and electrode structure 24, 26 ... Metal separator 28a ... Oxidant gas inlet communication hole 28b ... Oxidant Gas outlet communication hole 30a ... cooling medium inlet communication hole 30b ... cooling medium outlet communication hole 32a ... fuel gas inlet communication hole 32b ... fuel gas outlet communication hole 34 ... solid polymer electrolyte membrane 36 ... anode side electrode 38 ... cathode side electrode 40 ... Fuel gas flow path 42 ... Cooling medium flow path 44 ... Oxidant gas flow path 50 ... Fuel gas supply system 52 ... Oxidant gas supply system 54 ... Hydrogen tank 58 ... Ejector 60 ... Fuel gas circulation path 62 ... Fuel gas discharge path 64 ... Gas-liquid separators 66, 82, 92, 102 ... Drain flow paths 68, 84 ... Valve unit 70 ... Capacitance sensor 76 ... Purge Road 80 ... dilution box 86 ... oxidant gas supply channel 88 ... dilution gas flow channel

Claims (7)

A fuel cell stack in which an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the stacking direction;
A gas-liquid separation mechanism that communicates with a fuel gas outlet that is one of the reaction gas outlets via an exhaust gas passage that is exposed to the outside of the fuel cell stack;
One end of the flow path communicates with the fuel gas discharge port separately from the exhaust gas flow path, the other end of the flow path communicates with the gas-liquid separation mechanism, and from the fuel gas discharge port to the gas-liquid separation mechanism, A first drain channel for mainly discharging droplets;
A second drain channel communicating with the gas-liquid separation mechanism and mainly discharging droplets from the gas-liquid separation mechanism;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein a dilution mechanism that mainly communicates with the second drain flow path and discharges droplets from the gas-liquid separation mechanism;
A dilution fluid supply unit for supplying a dilution fluid to the dilution mechanism;
A fuel cell system comprising: A fuel cell stack in which an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the stacking direction;
A gas-liquid separation mechanism that communicates with a fuel gas outlet that is one of the reaction gas outlets via an exhaust gas passage that is exposed to the outside of the fuel cell stack;
A dilution mechanism in which droplets are mainly discharged from the gas-liquid separation mechanism;
A dilution fluid supply unit for supplying a dilution fluid to the dilution mechanism;
One end of the flow channel communicates with the fuel gas discharge port separately from the exhaust gas flow channel, the other end of the flow channel communicates with the dilution mechanism, and droplets mainly pass from the fuel gas discharge port to the dilution mechanism. A first drain channel for discharging;
A second drain channel that communicates with the gas-liquid separation mechanism and the dilution mechanism, and mainly discharges droplets from the gas-liquid separation mechanism to the dilution mechanism;
A fuel cell system comprising:   4. The fuel cell system according to claim 1, wherein a flow rate control mechanism is disposed in the first and second drain passages. 5. A fuel cell stack in which an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator are stacked, and at least a reaction gas introduction port and a reaction gas discharge port are formed through the stacking direction;
A fuel that communicates with a fuel gas discharge port that is one of the reaction gas discharge ports via an exhaust gas passage that is exposed to the outside of the fuel cell stack, and circulates to a fuel gas introduction port that is one of the reaction gas introduction ports. A gas circuit,
A first drain passage that communicates with the fuel gas outlet separately from the fuel gas outlet and is exposed to the outside of the fuel cell stack, and mainly discharges droplets from the fuel gas outlet;
A flow control mechanism disposed in the first drain channel;
A fuel cell system comprising: 6. The fuel cell system according to claim 5, wherein the fuel gas circulation path is provided with a gas-liquid separation mechanism,
A fuel cell system, wherein a second drain flow path communicates with the gas-liquid separation mechanism via a flow rate control mechanism. The fuel cell system according to claim 6, wherein a dilution mechanism is connected to the gas-liquid separation mechanism via the second drain channel.
A dilution fluid supply unit for supplying a dilution fluid to the dilution mechanism;
A fuel cell system comprising:

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