JP5538192B2 - Fuel cell system - Google Patents

Description

  The present invention includes a fuel cell that generates power by an electrochemical reaction of air supplied from an oxidant gas channel to the cathode side and fuel gas supplied from the fuel gas channel to the anode side, and a plurality of the fuel cells are stacked. The present invention relates to a fuel cell system including a fuel cell stack, an oxidant gas supply device that supplies the air to the fuel cell, and a fuel gas supply device that supplies the fuel gas to the fuel cell.

  In a fuel cell, a fuel gas (a gas mainly containing hydrogen, for example, hydrogen gas) and an oxidant gas (a gas mainly containing oxygen, for example, air) are supplied to an anode electrode and a cathode electrode to be electrochemical. It is a system that obtains direct-current electric energy by reacting with. This system is incorporated in a fuel cell vehicle for in-vehicle use as well as stationary use.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched between a pair of separators. Yes. A fuel gas passage for supplying fuel gas to the anode electrode is formed between one separator and the electrolyte membrane / electrode structure, and between the other separator and the electrolyte membrane / electrode structure. Is formed with an oxidant gas flow path for supplying an oxidant gas to the cathode electrode.

  By the way, when the fuel cell is stopped, the supply of the fuel gas and the oxidant gas is stopped, but the fuel gas remains in the fuel gas flow channel, while the oxidant gas remains in the oxidant gas flow channel. ing. Therefore, especially when the stop period of the fuel cell becomes long, the fuel gas and the oxidant gas may permeate the electrolyte membrane, and the fuel gas and the oxidant gas may be mixed.

  Therefore, for example, a fuel cell device disclosed in Patent Document 1 is known. The fuel cell device includes at least a reformer, an anode line including an anode electrode, a cathode line including at least a cathode electrode, and the anode line reformer, the anode electrode, and the cathode electrode of the cathode line. And a nitrogen gas introduction line for purging with nitrogen gas at the time and during stoppage.

  The fuel cell device includes a bypass line through which each of the anode electrode and the cathode electrode flows nitrogen gas, and a cutoff valve that blocks the flow of the nitrogen gas in the bypass line. Yes.

  Further, in the operation method of the fuel cell system disclosed in Patent Document 2, air is supplied to the cathode electrode of the fuel cell, and the gas after consumption of oxygen in the air is circulated again and supplied to the anode electrode. Has been. Thereby, concentrated nitrogen is produced | generated and the purge process by this concentrated nitrogen is performed.

Japanese Patent Publication No. 8-15091 US Pat. No. 6,939,633

  However, in the above Patent Document 1, it is necessary to use a nitrogen cylinder when the fuel cell device is mounted on a fuel cell vehicle. For this reason, there is a problem that the operation of periodically replenishing the nitrogen cylinder with nitrogen must be performed, and this type of operation becomes complicated.

  Moreover, in the above-mentioned Patent Document 2, there is a problem that the system capacity becomes considerably large and the power consumption increases, which is not economical.

  The present invention solves this type of problem, and an object thereof is to provide a fuel cell system capable of suppressing deterioration of the fuel cell as much as possible with a simple and compact configuration.

The present invention includes a fuel cell that generates power by an electrochemical reaction of air supplied from an oxidant gas channel to the cathode side and fuel gas supplied from the fuel gas channel to the anode side, and a plurality of the fuel cells are stacked. A fuel cell stack, an oxidant gas supply device for supplying the air to the fuel cell via an oxidant gas supply channel, and a fuel gas supply device for supplying the fuel gas to the fuel cell The present invention relates to a battery system.

  This fuel cell system operates with a low oxygen stoichiometry lower than the oxygen stoichiometry during normal power generation by the fuel cell stack, and generates an auxiliary gas that produces nitrogen-rich exhaust gas at the cathode outlet side than the cathode side outlet of the fuel cell stack. It has a fuel cell stack.

Inlet of the oxidizing gas channel of the fuel cell stack is in communication with oxidant gas supply channel, an outlet of the oxidant gas flow path of the fuel cell stack, the auxiliary fuel cell stack oxidant gas channel by communicating with the inlet, said a fuel cell stack wherein the oxidant gas flow path and the oxidant gas flow path and the auxiliary fuel cell stack are connected in series with the oxidant gas supply device.

  Furthermore, in this fuel cell system, the exhaust gas discharged from the oxidant gas flow path of the auxiliary fuel cell stack is pressurized and stored, and the exhaust gas can be supplied to at least the oxidant gas flow path of the fuel cell stack. A storage device is preferably provided.

  In the present invention, since the auxiliary fuel cell stack is generated by the low-oxygen stoichiometric oxidant gas, a nitrogen-rich (high nitrogen concentration) exhaust gas is generated at the cathode side outlet of the auxiliary fuel cell stack. Therefore, the nitrogen-rich exhaust gas can be used as a purge gas for purging, for example, an oxidant gas flow path of the fuel cell stack.

  For this reason, the cathode side of the fuel cell stack is filled with nitrogen gas, the oxygen concentration is lowered, and the fuel cell and the gas pipe can be filled with the nitrogen gas. Thereby, it becomes possible to suppress deterioration of the fuel cell as much as possible with a simple and compact configuration.

  In addition, power generation is performed in the auxiliary fuel cell stack in which the oxidant gas is supplied with low oxygen stoichiometry. For this reason, the electric power generated by the power generation of the auxiliary fuel cell stack can be effectively used as a driving power source for the auxiliary devices, and it is economical by suppressing energy loss as much as possible.

It is a schematic block diagram of a fuel cell system that are related to the present invention. FIG. 3 is an explanatory diagram of gas flow paths of an auxiliary fuel cell stack constituting the fuel cell system. It is circuit explanatory drawing which comprises the said fuel cell system. It is operation | movement explanatory drawing of the said fuel cell system. It is a schematic block diagram of a fuel cell system according to the implementation embodiments of the present invention.

As shown in FIG. 1, the fuel cell system 10 that relate to the present invention includes a fuel cell stack 12, an oxidizing gas supply device 14 for supplying the oxidant gas to the fuel cell stack 12, the fuel cell stack 12 A fuel gas supply device 16 for supplying fuel gas to the fuel cell stack 12 and a low oxygen stoichiometry lower than the oxygen stoichiometry during normal power generation by the fuel cell stack 12, and the cathode side outlet of the fuel cell stack 12 on the cathode outlet side And an auxiliary fuel cell stack 18 that generates exhaust gas richer in nitrogen, and a controller 20 that controls the entire fuel cell system 10. Although not shown, the fuel cell system 10 is mounted on a fuel cell vehicle such as a fuel cell vehicle. The auxiliary fuel cell stack 18 is connected in parallel to the oxidant gas supply device 14.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 22. Each fuel cell 22 includes, for example, an electrolyte membrane / electrode structure (MEA) 30 in which a solid polymer electrolyte membrane 24 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode electrode 26 and an anode electrode 28. .

  The cathode electrode 26 and the anode electrode 28 have a gas diffusion layer made of carbon paper or the like, and porous carbon particles carrying platinum (or a platinum alloy or the like) on the surface are uniformly applied to the surface of the gas diffusion layer. And an electrode catalyst layer formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 24.

  The electrolyte membrane / electrode structure 30 is sandwiched between a cathode side separator 32 and an anode side separator 34. The cathode side separator 32 and the anode side separator 34 are constituted by, for example, a carbon separator or a metal separator.

  An oxidant gas flow path 36 is provided between the cathode side separator 32 and the electrolyte membrane / electrode structure 30, and a fuel gas is provided between the anode side separator 34 and the electrolyte membrane / electrode structure 30. A flow path 38 is provided.

  The fuel cell stack 12 communicates with each other in the stacking direction of the fuel cells 22 to supply an oxidant gas, for example, an oxidant gas inlet communication hole 40a for supplying an oxygen-containing gas (hereinafter also referred to as air), a fuel gas, For example, a fuel gas inlet communication hole 42a for supplying a hydrogen-containing gas (hereinafter also referred to as hydrogen gas), a cooling medium inlet communication hole (not shown) for supplying a cooling medium, and an oxidant gas outlet for discharging the oxidant gas A communication hole 40b, a fuel gas outlet communication hole 42b for discharging the fuel gas, and a cooling medium outlet communication hole (not shown) for discharging the cooling medium are provided.

  The oxidant gas supply device 14 includes an air pump (compressor) 50 that compresses and supplies air from the atmosphere, and the air pump 50 is disposed in the air supply flow path 52. The air supply channel 52 is provided with an on-off valve 54 a and communicates with the oxidant gas inlet communication hole 40 a of the fuel cell stack 12.

  The oxidant gas supply device 14 includes an air discharge channel 56 that communicates with the oxidant gas outlet communication hole 40b. The air discharge channel 56 has a back pressure control valve (back pressure valve) 58 with an adjustable opening for adjusting the pressure of air supplied from the air pump 50 through the air supply channel 52 to the fuel cell stack 12. Provided.

  The fuel gas supply device 16 includes a hydrogen tank 60 that stores high-pressure hydrogen. The hydrogen tank 60 communicates with the fuel gas inlet communication hole 42 a of the fuel cell stack 12 through the hydrogen supply channel 62, and an open / close valve 54 b is disposed in the hydrogen supply channel 62. The hydrogen supply channel 62 is provided with a shutoff valve 64 and an ejector 66.

  The ejector 66 supplies the hydrogen gas supplied from the hydrogen tank 60 to the fuel cell stack 12 through the hydrogen supply flow path 62 and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell stack 12. Then, the gas is sucked from the hydrogen circulation path 68 and supplied again as fuel gas to the fuel cell stack 12.

  The off gas passage 70 communicates with the fuel gas outlet communication hole 42b. A hydrogen circulation path 68 communicates with the off-gas flow path 70, and a dilution box (not shown) is connected to the off-gas flow path 70 via an on-off valve 54c that is a purge valve. Dilution air is supplied to the dilution box from the air discharge channel 56 as necessary.

  The auxiliary fuel cell stack 18 is replaceably mounted on the fuel cell system 10 and is configured by stacking a plurality of fuel cells 22a. Each fuel cell 22a includes an electrolyte membrane / electrode structure 30a in which a solid polymer electrolyte membrane 24a is sandwiched between a cathode electrode 26a and an anode electrode 28a. The electrolyte membrane / electrode structure 30a is sandwiched between the cathode side separator 32a and the anode side separator 34a.

  An oxidant gas flow path 36a is provided between the cathode side separator 32a and the electrolyte membrane / electrode structure 30a, and a fuel gas is provided between the anode side separator 34a and the electrolyte membrane / electrode structure 30a. A flow path 38a is provided. The oxidant gas flow path 36 a and the oxidant gas flow path 36 of the fuel cell stack 12 are connected in parallel to the oxidant gas supply device 14.

  The auxiliary fuel cell stack 18 communicates with each other in the stacking direction of the fuel cells 22a, and includes an oxidant gas inlet communication hole 72a, a fuel gas inlet communication hole 74a, a cooling medium inlet communication hole (not shown), an oxidant gas. An outlet communication hole 72b, a fuel gas outlet communication hole 74b, and a cooling medium outlet communication hole (not shown) are provided.

  As shown in FIG. 2, the fuel cell 22a has an oxidant gas so as to have a uniform gas distribution capable of generating power with a low oxygen stoichiometry, that is, a structure in which the concentration distribution of the supplied reaction gas is difficult to occur. An inlet communication hole 72a, a fuel gas inlet communication hole 74a, an oxidant gas outlet communication hole 72b, and a fuel gas outlet communication hole 74b are formed longer than the channel width along each side. The oxidant gas flow path 36a and the fuel gas flow path 38a are mutually tolerance, preferably orthogonal to each other.

  Further, each of the oxidant gas flow path 36a and the fuel gas flow path 38a has a plurality of linear grooves, and the electrode area is set small. The auxiliary fuel cell stack 18 is set to a lower output than the fuel cell stack 12, the electrode area is about a fraction of that of the fuel cell stack 12, and the number of stacked layers is also set to be small.

  As shown in FIG. 1, one end of an air supply branch passage 76 is connected to the oxidant gas inlet communication hole 72a, and the other end of the air supply branch passage 76 is located upstream of the on-off valve 54a. Thus, the air supply channel 52 is connected. The air supply branch flow path 76 is provided with an on-off valve 54d.

  One end of an air discharge branch flow path 78 is connected to the oxidant gas outlet communication hole 72b, and the other end of the air discharge branch flow path 78 is located downstream of the on-off valve 54a. Connected to. A pump 80 with a check valve, a nitrogen gas tank (exhaust gas storage device) 84, and an on-off valve 54e are disposed in the air discharge branch flow path 78. A pressure reducing valve (not shown) may be provided downstream of the nitrogen gas tank 84.

  One end of a hydrogen supply branch flow path 86 is connected to the fuel gas inlet communication hole 74a, and the other end of the hydrogen supply branch flow path 86 is located upstream of the on-off valve 54b and is connected to the hydrogen supply flow path 62. Connected. An open / close valve 54 f is disposed in the hydrogen supply branch flow path 86. One end of the hydrogen discharge branch flow path 88 is connected to the fuel gas outlet communication hole 74 b, and the other end of the hydrogen discharge branch flow path 88 is connected to the off gas flow path 70. The hydrogen discharge branch flow path 88 is provided with an on-off valve 54g.

  As shown in FIG. 3, one end of a bus line 90 is connected to the fuel cell stack 12, and the other end of the bus line 90 is connected to an inverter 92. A drive motor 94 for three-phase vehicle travel is connected to the inverter 92. In addition, although the bus line 90 substantially uses two wires, a plus and a minus, for the sake of simplifying the description, it is described as a single bus line 90.

  An FC contactor 96 is disposed on the bus line 90 and one end of a power line 98 is connected to the power line 98, and a secondary battery 104 is connected to the power line 98 via a DC / DC converter 100 and a battery contactor 102. Is done. The auxiliary fuel cell stack 18 is connected to the bus line 90 via the FC contactor 106 and the DC / DC converter 108.

  The auxiliary fuel cell stack 18 can supply surplus power to the auxiliary devices 110, and power is supplied from the secondary battery 104 to the auxiliary devices 110 when power is insufficient. The auxiliary devices 110 include an air pump 50, a pump 80 with a check valve, open / close valves 54a to 54g, a back pressure control valve 58, a shutoff valve 64, and the like.

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

  First, at the start of operation of the fuel cell system 10, power is supplied from the secondary battery 104 to the auxiliary devices 110 and power generation of the fuel cell stack 12 is started. In the fuel cell stack 12, air is sent to the air supply flow path 52 via the air pump 50 constituting the oxidant gas supply device 14. This air is supplied to the oxidant gas inlet communication hole 40a of the fuel cell stack 12, and is supplied to the cathode electrode 26 by moving along the oxidant gas flow path 36 provided in each fuel cell 22. .

  The used air is discharged from the oxidant gas outlet communication hole 40 b to the air discharge passage 56 and then discharged through the back pressure control valve 58.

  On the other hand, in the fuel gas supply device 16, the shutoff valve 64 is opened so that the pressure is reduced from the hydrogen tank 60 by a pressure reducing valve (not shown), and then the hydrogen gas is supplied to the hydrogen supply flow path 62. This hydrogen gas is supplied to the fuel gas inlet communication hole 42 a of the fuel cell stack 12 through the hydrogen supply channel 62. The hydrogen gas supplied into the fuel cell stack 12 is supplied to the anode electrode 28 by moving along the fuel gas flow path 38 of each fuel cell 22.

  The used hydrogen gas is sucked into the ejector 66 from the fuel gas outlet communication hole 42b through the hydrogen circulation path 68, and is supplied again to the fuel cell stack 12 as fuel gas. Accordingly, the air supplied to the cathode electrode 26 and the hydrogen gas supplied to the anode electrode 28 react electrochemically to generate power. For this reason, electric power is supplied from the fuel cell stack 12 to the drive motor 94, and the fuel cell vehicle can run.

  Next, power generation of the auxiliary fuel cell stack 18 is started. In the auxiliary fuel cell stack 18, when the on-off valve 54d is opened, the oxidant gas supply device 14 communicates with the oxidant gas flow path 36a, and air is supplied to the oxidant gas flow path 36a. At that time, the supplied air is set to a lower oxygen stoichiometric state than in normal operation. The stoichiometry is lower than that of the fuel cell stack 12. Further, in the auxiliary fuel cell stack 18, the fuel gas supply device 16 communicates with the fuel gas flow path 38 by opening the on-off valves 54 f and 54 g.

  Thereby, in each fuel cell 22a, the air supplied to the cathode electrode 26a and the hydrogen gas supplied to the anode electrode 28a react electrochemically to generate power. Then, electric power is supplied from the auxiliary fuel cell stack 18 to the auxiliary devices 110, while the secondary battery 104 shifts from the discharge mode to the charge mode.

The air supplied to the auxiliary fuel cell stack 18 is set to a low oxygen stoichiometry in which the oxygen stoichiometry in the air is lower than the oxygen stoichiometry during normal power generation. Specifically, the low oxygen stoichiometry is set to about 1 to 1.2. Therefore, in the auxiliary fuel cell stack 18, power generation is performed in an O ₂ lean state, and on the cathode side, the oxygen concentration decreases and the nitrogen concentration increases, and nitrogen gas having a high concentration (for example, 90% or more) as exhaust gas. Will occur.

  The exhaust gas, which is a nitrogen-rich gas, is discharged to the air discharge branch passage 78 and is press-fitted into the nitrogen gas tank 84 under the driving action of the pump 80 with a check valve. When the pressure of the exhaust gas filled in the nitrogen gas tank 84 reaches the set pressure, the supply of hydrogen and air to the auxiliary fuel cell stack 18 is stopped.

  Next, when the operation of the fuel cell system 10 is stopped, as shown in FIG. 4, the on-off valves 54a and 54b and the shutoff valve 64 are closed, and the fuel cell stack 12, the oxidant gas supply device 14 and The fuel gas supply device 16 is shut off. When the on-off valve 54e is opened in this state, the exhaust gas (nitrogen rich gas) press-fitted into the nitrogen gas tank 84 is supplied from the air supply channel 52 to the oxidant gas channel 36 in the fuel cell stack 12. The

  For this reason, in the fuel cell stack 12, power is generated (discharged) by the remaining oxygen and hydrogen gas in the air, and the hydrogen concentration on the anode side is reduced, while nitrogen-rich gas is supplied to the cathode side. . Therefore, on the anode side, a negative pressure state is caused by a decrease in the hydrogen concentration, and nitrogen gas is transmitted from the cathode side to the anode side. After the nitrogen rich gas is sufficiently supplied into the fuel cell stack 12, the on-off valve 54e is closed and the supply of the nitrogen rich gas is stopped.

In this case, in the fuel cell system 10 , the auxiliary fuel cell stack 18 is provided separately from the fuel cell stack 12 and is replaceable. Since the auxiliary fuel cell stack 18 generates power with a low-oxygen stoichiometric oxidant gas (air), exhaust gas rich in nitrogen (high in nitrogen concentration) is generated at the cathode side outlet of the auxiliary fuel cell stack 18. Yes.

  The exhaust gas is press-fitted into the nitrogen gas tank 84 and can be used as a purge gas for discharging the remaining hydrogen and oxygen when the fuel cell stack 12 is stopped, for example. For this reason, the cathode side is filled with nitrogen gas, the oxygen concentration is lowered, and the fuel cell 22 and the gas pipe can be filled with the nitrogen gas which is an inert gas. Thereby, the effect that it becomes possible to suppress deterioration of the fuel cell 22 as much as possible with a simple and compact configuration is obtained.

  In addition, power generation is performed in the auxiliary fuel cell stack 18 to which the oxidant gas is supplied with low oxygen stoichiometry. For this reason, the electric power generated by the power generation of the auxiliary fuel cell stack 18 can be effectively used as a driving power source for the auxiliary devices 110, and the energy loss is suppressed as much as possible, which is economical. Moreover, since the nitrogen-rich gas is stored under pressure in the nitrogen gas tank 84, a large amount of the nitrogen-rich gas can be efficiently stored.

  Further, in the fuel cell 22a constituting the auxiliary fuel cell stack 18, as shown in FIG. 2, the oxidant gas inlet communication hole 72a, the fuel gas inlet communication hole 74a, the oxidant gas outlet communication hole 72b, and the fuel gas outlet communication hole. 74b is formed long along each side, and the oxidant gas flow path 36a and the fuel gas flow path 38a each have a plurality of linear grooves. Accordingly, the fuel cell 22a has a uniform gas distribution capable of generating power with low oxygen stoichiometry, and even with stoichiometry about 1, it is possible to efficiently produce concentrated nitrogen without damaging the electrode catalyst layer.

  Furthermore, in the auxiliary fuel cell stack 18, the power generation output is lower than that of the fuel cell stack 12 and is about 5% to 50% of the power generation output, and the rated current density is 20% lower than that of the auxiliary fuel cell stack 12. It is about 30%, and the use potential region is set to 0.8 V or less of the catalyst carrier corrosion potential.

  If the power generation output is less than 5%, the amount of gas that can be consumed by oxygen is insufficient, and it takes time to generate gas necessary for oxygen discharge in the fuel cell stack 12. On the other hand, if the power generation output exceeds 50%, the auxiliary fuel cell stack 18 is likely to deteriorate, and the replacement frequency of the auxiliary fuel cell stack 18 increases, which is not economical.

  On the other hand, if the rated current density of the auxiliary fuel cell stack 18 is too small, corrosion of the catalyst carrier is caused. On the other hand, if the rated current density is too large, the amount of generated water increases and clogging of the channel groove occurs, resulting in uniform power generation on the electrode surface. There is a problem that it is not done.

Figure 5 is a schematic block diagram of a fuel cell system 120 according to the implementation embodiments of the present invention. Note that the fuel cell system 10 same components and are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The fuel cell system 120 includes a fuel cell stack 122, an oxidant gas supply device 124 that supplies oxidant gas to the fuel cell stack 122, a fuel gas supply device 126 that supplies fuel gas to the fuel cell stack 12, An auxiliary fuel cell stack that operates with a low oxygen stoichiometry lower than that during normal power generation by the fuel cell stack 122 and generates exhaust gas richer in nitrogen than the cathode side outlet of the fuel cell stack 122 on the cathode outlet side 128, and a controller 20 that controls the entire fuel cell system 120.

  The fuel cell stack 122 has a nitrogen gas inlet communication hole 130 a and a nitrogen gas outlet communication hole 130 b communicating with the oxidant gas flow path 36, and a nitrogen gas inlet communication hole 132 a and a nitrogen gas outlet communication communicating with the fuel gas flow path 38. A hole 132b is provided.

  An auxiliary fuel cell stack 128, a pump 80 with a check valve, a nitrogen gas tank 84, and a back pressure control valve 58 are provided in the air discharge flow path 56 that constitutes the oxidant gas supply device 124.

  The air discharge channel 56 communicates with the oxidant gas inlet communication hole 72 a and the oxidant gas outlet communication hole 72 b of the auxiliary fuel cell stack 128. A hydrogen supply branch flow path 86 and a hydrogen discharge branch flow path 88 are connected to the fuel gas inlet communication hole 74 a and the fuel gas outlet communication hole 74 b of the auxiliary fuel cell stack 128.

  One end of nitrogen gas discharge paths 134 and 136 is connected to the nitrogen gas tank 84. The other ends of the nitrogen gas discharge paths 134 and 136 are connected to the nitrogen gas inlet communication holes 130 a and 132 a of the fuel cell stack 122. On-off valves 54h and 54i are disposed in the nitrogen gas outlet communication holes 130b and 132b. The nitrogen gas discharge paths 134 and 136 preferably supply gas decompressed by a pressure reducing valve (not shown) to the nitrogen gas inlet communication holes 130a and 132a.

In the fuel cell system 10 , the auxiliary fuel cell stack 18 is connected in parallel to the oxidant gas supply device 14, whereas in this embodiment, the auxiliary fuel cell stack 128 is connected to the oxidant gas supply device 124. Connected in series.

In the present embodiment configured as described above, the air supplied to the oxidant gas flow path 36 of the fuel cell stack 122 during the normal power generation by the fuel cell stack 122 is supplemented from the oxidant gas outlet communication hole 40b as exhaust gas. It is sent to the oxidant gas flow path 36 a of the fuel cell stack 128. The exhaust gas is introduced into the nitrogen gas tank 84 through the auxiliary fuel cell stack 128 and is discharged through the back pressure control valve 58.

  On the other hand, when the fuel cell system 120 is stopped, air having a low oxygen concentration discharged from the oxidant gas flow path 36 of the fuel cell stack 122 is supplied to the oxidant gas flow path 36a of the auxiliary fuel cell stack 128, and the fuel. Hydrogen is supplied from the fuel gas supply device 126 to the gas flow path 38a. Therefore, power generation is started in the auxiliary fuel cell stack 128, oxygen is almost consumed, and nitrogen-rich exhaust gas is discharged from the oxidant gas outlet communication hole 72b.

  The exhaust gas is pressurized and stored in the nitrogen gas tank 84 and supplied to the nitrogen gas inlet communication holes 130 a and 132 a of the fuel cell stack 122 from the nitrogen gas discharge paths 134 and 136. The exhaust gas is introduced into the oxidant gas passage 36 and the fuel gas passage 38 in the fuel cell stack 122, and oxygen and hydrogen are discharged from the fuel cell stack 122.

Thus, in the present embodiment, the same effects as those of the fuel cell system 10 described above can be obtained, such as the deterioration of the fuel cell 22 can be suppressed as much as possible with a simple and compact configuration.

  During normal power generation, the oxidant gas outlet communication hole 72b and the back pressure control valve 58 may be directly connected, bypassing the pump 80 with check valve and the nitrogen gas tank 84.

DESCRIPTION OF SYMBOLS 10, 120 ... Fuel cell system 12, 122 ... Fuel cell stack 14, 124 ... Oxidant gas supply device 16, 126 ... Fuel gas supply device 18, 128 ... Auxiliary fuel cell stack 20 ... Controller 22, 22a ... Fuel cell 24, 24a ... solid polymer electrolyte membrane 26, 26a ... cathode electrode 28, 28a ... anode electrode 30, 30a ... electrolyte membrane / electrode structure 32, 32a, 34, 34a ... separator 36, 36a ... oxidant gas channel 38, 38a ... fuel gas flow paths 40a, 72a ... oxidant gas inlet communication holes 40b, 72b ... oxidant gas outlet communication holes 42a, 74a ... fuel gas inlet communication holes 42b, 74b ... fuel gas outlet communication holes 50 ... air pump 52 ... air supply Flow path 54a-54i ... Open / close valve 56 ... Air discharge flow path 58 ... Back pressure control valve 60 ... Hydrogen tank 62 ... Water Element supply passage 64 ... Shut-off valve 66 ... Ejector 68 ... Hydrogen circulation passage 76 ... Air supply branch passage 78 ... Air discharge branch passage 80 ... Pump with check valve 84 ... Nitrogen gas tank 86 ... Hydrogen supply branch passage 88 ... Hydrogen discharge branch flow path 94 ... Drive motor 110 ... Auxiliary devices 130a, 132a ... Nitrogen gas inlet communication holes 130b, 132b ... Nitrogen gas outlet communication holes 134, 136 ... Nitrogen gas discharge path

Claims (2)

A fuel cell comprising a fuel cell that generates electricity by an electrochemical reaction of air supplied from an oxidant gas channel to the cathode side and fuel gas supplied from the fuel gas channel to the anode side, wherein a plurality of the fuel cells are stacked Stack,
An oxidant gas supply device for supplying the air to the fuel cell via an oxidant gas supply channel ;
A fuel gas supply device for supplying the fuel gas to the fuel cell;
A fuel cell system comprising:
An auxiliary fuel cell stack that operates with a low oxygen stoichiometry lower than the oxygen stoichiometry during normal power generation by the fuel cell stack and generates exhaust gas richer in nitrogen than the cathode side outlet of the fuel cell stack on the cathode outlet side ,
The inlet of the oxidant gas channel of the fuel cell stack communicates with the oxidant gas supply channel, and the outlet of the oxidant gas channel of the fuel cell stack is the oxidant of the auxiliary fuel cell stack By communicating with the inlet of the gas flow path, the oxidant gas flow path of the fuel cell stack and the oxidant gas flow path of the auxiliary fuel cell stack are connected in series to the oxidant gas supply device. the fuel cell system according to claim Rukoto is. In claim 1 Symbol placement of the fuel cell system, the addition to the pressurized stored the exhaust gas discharged from the oxidant gas flow path of the auxiliary fuel cell stack, the oxidant gas flow path of at least the fuel cell stack the gas A fuel cell system comprising an exhaust gas storage device that can be freely supplied to a fuel cell.

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