JP2010061981A - Starting method for fuel cell system - Google Patents

Abstract

The present invention provides a simple process for preventing deterioration of an electrode catalyst as much as possible and maintaining good power generation performance.
In a fuel cell, an electrolyte membrane / electrode structure is sandwiched between a cathode separator and an anode separator. The anode separator 30 is provided with a plurality of fuel gas flow paths 46a, 46b alternately via peak portions 48a, 48b. The fuel gas channel 46a is provided with a throttle on the inlet side, while the fuel gas channel 46b is provided with a throttle on the outlet side. The fuel cell system is started by supplying hydrogen gas to the fuel gas passages 46a and 46b and preferentially circulating the hydrogen gas through the fuel gas passage 46b having no throttle on the inlet side. A differential pressure is generated between the gas passage 46b and the fuel gas passage 46a, and the air remaining in the gas diffusion layer 26b facing the peaks 48a and 48b is replaced with hydrogen gas.
[Selection] Figure 3

Description

  The present invention has a plurality of oxidant gas passages for supplying an oxidant gas to the cathode side electrode and a plurality of fuel gas passages for supplying a fuel gas to the anode side electrode, and the oxidant gas and the fuel gas The present invention relates to a method for starting a fuel cell system that includes a fuel cell that generates electric power through an electrochemical reaction, and that is shut down in a state where the oxidant gas channel and the fuel gas channel are filled with the oxidant gas.

  A fuel cell supplies a fuel gas (mainly hydrogen-containing gas) and an oxidant gas (mainly oxygen-containing gas) to the anode-side electrode and the cathode-side electrode and causes them to react electrochemically. It is a system that obtains electrical energy.

  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 by separators. Has a cell. This type of power generation cell is normally used as a fuel cell stack by alternately laminating a predetermined number of electrolyte membrane / electrode structures and separators.

  In this type of fuel cell, when power generation (operation) is stopped, supply of fuel gas and oxidant gas to the fuel cell is stopped, but the fuel gas remains on the anode side electrode, while the cathode side The oxidant gas remains on the electrode. For this reason, there is a problem that a reaction is caused while the fuel cell is stopped, the cathode side is held at a high potential, and the electrode catalyst layer is deteriorated.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. The fuel cell system includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas, a fuel gas supply system that supplies fuel gas to a fuel electrode side of the fuel cell, and an oxidation of the fuel cell. An oxidant gas supply system for supplying an oxidant gas to the agent electrode side, a humidifying means for humidifying the oxidant gas, and a communication means for connecting the fuel gas supply system and the oxidant gas supply system in an openable and closable manner And.

  And, when the system operation is stopped, the supply of the fuel gas to the fuel electrode side of the fuel cell is stopped, and the oxidant gas dried than the oxidant gas supplied at the time of normal power generation is supplied to the oxidant electrode side. The operation is stopped after supplying the dried oxidant gas to the fuel electrode side through the communication means.

  As a result, the deterioration of the electrolyte membrane and catalyst layer of the fuel cell during shutdown and storage can be effectively suppressed, and the possibility of voltage generation during storage is eliminated, so that handling during storage is also improved. , And.

JP 2006-86015 A

  By the way, in a fuel cell, as shown in FIG. 7, the electrolyte membrane / electrode structure 1 is usually sandwiched between an anode side separator 2 and a cathode side separator 3. The electrolyte membrane / electrode structure 1 includes a solid polymer electrolyte membrane 4, and an anode side electrode 5 and a cathode side electrode 6 are provided on both surfaces of the solid polymer electrolyte membrane 4. The anode side electrode 5 has an electrode catalyst layer 5a and a gas diffusion layer 5b, while the cathode side electrode 6 has an electrode catalyst layer 6a and a gas diffusion layer 6b.

  The anode-side separator 2 has a plurality of fuel gas passages 2a formed between the peaks 2b, and the cathode-side separator 3 has a plurality of oxidant gas passages 3a formed between the peaks 3b. .

  When the above-described Patent Document 1 is employed when the operation of the fuel cell is stopped, the fuel gas passage 2a and the oxidant gas passage 3a are filled with the dried oxidant gas. Therefore, when starting the fuel cell, the fuel gas is supplied to the fuel gas passage 2a, so that the oxidant gas remaining in the fuel gas passage 2a and the gas diffusion layer 5b is replaced with the fuel gas. Has been.

  However, in the gas diffusion layer 5b, particularly in the portion 7 facing the peak portion 2b of the anode-side separator 2, the fuel gas hardly flows, and the oxidant gas remaining in this portion 7 is replaced with the fuel gas. It takes a considerable amount of time. Thereby, there exists a problem that fuel gas and oxidant gas react, the electrode catalyst layer 5a deteriorates, and the electric power generation performance of a fuel cell falls.

  The present invention solves this type of problem, and provides a starting method of a fuel cell system capable of preventing deterioration of an electrode catalyst as much as possible and maintaining good power generation performance with a simple process. The purpose is to do.

  The present invention has a plurality of oxidant gas passages for supplying an oxidant gas to the cathode side electrode and a plurality of fuel gas passages for supplying a fuel gas to the anode side electrode, and the oxidant gas and the fuel gas The present invention relates to a method for starting a fuel cell system that includes a fuel cell that generates electricity by an electrochemical reaction, and that is shut down in a state where the oxidant gas channel and the fuel gas channel are filled with the oxidant gas.

  In this starting method, the fuel gas is supplied to the fuel gas flow path, and a differential pressure is generated between the adjacent fuel gas flow paths, so that the oxidant gas staying in at least the power generation region of the anode side electrode is The fuel gas is substituted.

  The fuel gas flow paths adjacent to each other are provided with throttle portions alternately on the inlet side of one fuel gas flow channel and the outlet side of the other fuel gas flow channel, and the throttle portions are disposed outside the power generation region. By doing so, it is preferable to replace at least the oxidant gas staying in the power generation region with the fuel gas.

  Further, in this starting method, it is preferable to replace the oxidant gas with the fuel gas by supplying the fuel gas to the fuel gas flow channel after making the fuel gas flow channel have a negative pressure.

  In the present invention, in order to generate a differential pressure between adjacent fuel gas passages, the fuel gas moves from the high-pressure fuel gas passage to the low-pressure fuel gas passage. Therefore, the oxidant gas remaining in the gas diffusion layer facing the mountain portion that partitions adjacent fuel gas flow paths is satisfactorily replaced by the fuel gas that moves across the fuel gas flow paths.

  As a result, at least the oxidant gas remaining in the entire power generation region can be quickly and reliably replaced with the fuel gas, and the deterioration of the electrode catalyst is prevented as much as possible with a simple process, and the power generation performance is improved. It becomes possible to maintain.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 10 to which a starting method according to a first embodiment of the present invention is applied.

  The fuel cell system 10 includes a fuel cell stack 12, an oxidant gas supply device 14 for supplying an oxidant gas to the fuel cell stack 12, a fuel gas supply device 16 for supplying a fuel gas to the fuel cell stack 12, And a controller 18 that controls the entire fuel cell system 10.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20. As shown in FIG. 2, each fuel cell 20 includes, for example, an electrolyte membrane in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode side electrode 24 and an anode side electrode 26. An electrode structure 28 is provided. The electrolyte membrane / electrode structure 28 is sandwiched between the cathode side separator 29 and the anode side separator 30. The cathode side separator 29 and the anode side separator 30 are made of, for example, a carbon separator.

  As shown in FIG. 3, the cathode-side electrode 24 and the anode-side electrode 26 are formed on both surfaces of the solid polymer electrolyte membrane 22, and electrode catalyst layers 24a, 26a made of porous carbon particles having platinum alloys supported on the surface thereof. And gas diffusion layers 24b and 26b made of carbon paper or the like.

  As shown in FIG. 2, one end edge of the fuel cell 20 in the arrow B direction (longitudinal direction) communicates with each other in the arrow A direction, which is the stacking direction, and an oxidant gas, for example, an oxygen-containing gas (hereinafter, An oxidant gas inlet communication hole 32a for supplying a cooling medium, a cooling medium outlet communication hole 34b for discharging a cooling medium, and a fuel gas outlet for discharging a fuel gas, for example, a hydrogen-containing gas (hereinafter also referred to as hydrogen gas). The communication holes 36b are arranged in the direction of arrow C (vertical direction).

  The other end edge of the fuel cell 20 in the direction of arrow B communicates with each other in the direction of arrow A, a fuel gas inlet communication hole 36a for supplying fuel gas, a cooling medium inlet communication hole 34a for supplying a cooling medium, and an oxidation Oxidant gas outlet communication holes 32b for discharging the agent gas are arranged in the direction of arrow C.

  A plurality of oxidant gas flow paths 38 extending in the direction of arrow B are provided between the peaks 40 on the surface 29 a of the cathode separator 29 facing the electrolyte membrane / electrode structure 28. Both ends of the oxidant gas flow path 38 in the direction of arrow B communicate with the oxidant gas inlet communication hole 32a and the oxidant gas outlet communication hole 32b via the buffer portions 42a and 42b. A cooling medium flow path 44 is formed between a surface 29 b opposite to the surface 29 a of the cathode side separator 29 and the anode side separator 30.

  As shown in FIG. 4, on the surface 30a of the anode-side separator 30 facing the electrolyte membrane / electrode structure 28, a plurality of fuel gas channels 46a, 46b extend in the direction of arrow B, and peak portions 48a, 48b are formed. Are alternately formed. Buffer portions 50a and 50b are provided at both ends of the fuel gas flow paths 46a and 46b.

  A plurality of communication holes 52a and 52b are formed in the anode-side separator 30 so as to be close to the fuel gas inlet communication hole 36a and the fuel gas outlet communication hole 36b, respectively. The communication hole 52a communicates the fuel gas inlet communication hole 36a from the surface 30b side to the surface 30a side, and further communicates with the fuel gas flow paths 46a and 46b via the buffer portion 50a. The communication hole 52b communicates the fuel gas outlet communication hole 36b from the surface 30b side to the surface 30a side, and further communicates with the fuel gas flow paths 46a and 46b via the buffer portion 50b.

  The fuel gas channel 46a is provided with a throttle 54a on the inlet side (buffer 50a side), while the fuel gas channel 46b is provided with a throttle 54b on the outlet side (buffer 50b side). The throttle portions 54 a and 54 b are alternately arranged in the direction of arrow C, and the throttle portions 54 a and 54 b are set outside the power generation region G of the anode side electrode 26. For example, the depths on the inlet side of the fuel gas channel 46a and the outlet side of the fuel gas channel 46b may be set to be shallow instead of the throttle portions 54a and 54b.

  The cathode side separator 29 is provided with a seal member 56 such as a gasket, and the anode side separator 30 is similarly provided with a seal member 58 such as a gasket.

  As shown in FIG. 1, the oxidant gas supply device 14 includes an air compressor 60 that compresses and supplies air from the atmosphere, and the air compressor 60 is disposed in an air supply flow path 62. A humidifier 64 is disposed in the air supply flow path 62, and the air supply flow path 62 communicates with the oxidant gas inlet communication hole 32 a of the fuel cell stack 12.

  The oxidant gas supply device 14 includes an air discharge channel 66 that communicates with the oxidant gas outlet communication hole 32b. The air discharge channel 66 is provided with a back pressure control valve 68 with an adjustable opening for adjusting the pressure of air supplied from the air compressor 60 through the air supply channel 62 to the fuel cell stack 12. .

  The fuel gas supply device 16 includes a hydrogen tank 70 that stores high-pressure hydrogen. The hydrogen tank 70 communicates with the fuel gas inlet communication hole 36 a of the fuel cell stack 12 through a hydrogen supply flow path 72. In this hydrogen supply flow path 72, a hydrogen tank main valve 74a, a pressure reducing valve 74b, a hydrogen supply valve 74c, and an ejector 76 are sequentially provided.

  The ejector 76 supplies the hydrogen gas supplied from the hydrogen tank 70 to the fuel cell stack 12 through the hydrogen supply flow path 72, 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 84 and supplied again as fuel gas to the fuel cell stack 12.

  The hydrogen supply flow path 72 and the air supply flow path 62 can communicate with each other via a connection flow path 78, and a valve 80 is disposed in the connection flow path 78.

  An off gas passage 82 communicates with the fuel gas outlet communication hole 36b. A hydrogen circulation path 84 communicates with the off-gas flow path 82, and the hydrogen circulation path 84 communicates with an ejector 76. A hydrogen pump 88 is connected to the hydrogen circulation path 84 via a pump valve 86, while a fuel discharge valve (purge valve) 90 is disposed in the offgas flow path 82.

  For example, a load 92 such as a travel motor is provided in the fuel cell stack 12 through a switch 94 so as to be electrically disconnected and connectable.

  The operation of the fuel cell system 10 configured as described above will be described below in relation to the starting method according to the first embodiment of the present invention.

  When the operation of the fuel cell system 10 is stopped, as will be described later, the oxidant gas passage 38 and the fuel gas passages 46a and 46b are filled with air which is an oxidant gas.

  Therefore, when the start signal of the fuel cell system 10 is input to the controller 18, for example, the hydrogen supply valve 74c is closed and the pump valve 86 is opened. Therefore, the fuel gas flow paths 46 a and 46 b in the fuel cell stack 12 are sucked under the action of the hydrogen pump 88.

  When the fuel gas passages 46a and 46b reach a predetermined negative pressure state (for example, 40 to 85 kPa in absolute pressure), the pump valve 86 is closed and the hydrogen supply valve 74c is opened. Accordingly, hydrogen gas as fuel gas is supplied from the hydrogen tank 70 to the hydrogen supply flow path 72.

  This hydrogen gas is supplied to the fuel gas inlet communication hole 36 a of the fuel cell stack 12 through the hydrogen supply flow path 72. Thereby, in the fuel cell stack 12, hydrogen gas is supplied to the fuel gas flow paths 46a and 46b of each fuel cell 20. Specifically, as shown in FIGS. 2 and 4, the hydrogen gas supplied to each anode-side separator 30 moves from the surface 30b side to the surface 30a side through the plurality of communication holes 52a, and the buffer portion 50a. To the fuel gas flow paths 46a and 46b.

  In this case, in the first embodiment, as shown in FIG. 4, the throttle portion 54a is provided on the inlet side of the fuel gas passage 46a, while the throttle portion 54b is provided on the outlet side of the fuel gas passage 46b. Yes. For this reason, the hydrogen gas introduced into the buffer 50a has a low resistance, that is, it preferentially circulates in the fuel gas flow path 46b having no throttle on the inlet side, while providing the throttle 54a on the inlet side. A relatively small amount of hydrogen gas flows through the flow path 46a.

  The fuel gas passage 46b through which a large amount of hydrogen gas circulates is provided with a throttle portion 54b on the outlet side. The hydrogen gas pressure in the fuel gas passage 46b is higher than the hydrogen gas pressure in the fuel gas passage 46a. Even high pressure. Accordingly, a differential pressure of the hydrogen gas pressure is generated between the fuel gas flow paths 46b and 46a, and the hydrogen gas in the fuel gas flow path 46b on the high pressure side is in the gas diffusion layer 26b facing the peaks 48a and 48b. And moves to the fuel gas passage 46a on the low pressure side (see FIGS. 3 and 4).

  At that time, air remains in the gas diffusion layer 26b over almost the entire area, and the air in the vicinity of the portion facing the fuel gas flow path 46b easily and quickly passes with the hydrogen gas flowing through the fuel gas flow path 46b. On the other hand, air tends to remain in the vicinity of the portion facing the peak portions 48a and 48b.

  However, in the first embodiment, due to the differential pressure of the hydrogen gas pressure between the fuel gas passages 46b and 46a, the hydrogen gas flowing through the fuel gas passage 46b has a portion facing the peak portions 48a and 48b. It moves to the fuel gas flow path 46a. As a result, the air remaining in the vicinity of the portion facing the ridges 48a and 48b is satisfactorily and quickly replaced by the hydrogen gas moving across the fuel gas flow paths 46b and 46a.

  For this reason, the oxidant gas remaining in at least the entire power generation region of the fuel gas passages 46a and 46b and the gas diffusion layer 26b can be quickly and reliably replaced with hydrogen gas, and the electrode catalyst layer 26a can be easily processed. As a result, it is possible to prevent the deterioration of the fuel cell as much as possible and to maintain the power generation performance of each fuel cell 20 satisfactorily.

  Moreover, in the fuel gas passages 46a and 46b, hydrogen gas is supplied after being brought into a negative pressure state before starting. Therefore, the air remaining in the fuel gas passages 46a and 46b and the gas diffusion layer 26b can be replaced with hydrogen gas more quickly, and the fuel cell stack 12 can be started up reliably in a short time. There is.

  The hydrogen gas flowing through the fuel gas passages 46a and 46b is discharged from the buffer portion 50b through the plurality of communication holes 52b to the fuel gas outlet communication hole 36b.

  On the other hand, in the oxidant gas supply device 14, as shown in FIG. 1, air is sent to the air supply flow path 62 via the air compressor 60. The air is supplied to the oxidant gas inlet communication hole 32 a and is supplied to the cathode separator 29 provided in each fuel cell 20 in the fuel cell stack 12.

  As shown in FIG. 2, in the cathode side separator 29, the air supplied to the oxidant gas inlet communication hole 32 a is supplied to the cathode side electrode 24 while moving in the arrow B direction along the oxidant gas flow path 38. Is done.

  In this manner, hydrogen gas is supplied to the fuel gas flow paths 46 a and 46 b, while air is supplied to the oxidant gas flow path 38. In this state, as shown in FIG. 1, the switch 94 is closed to electrically connect the fuel cell stack 12 to the load 92. For this reason, starting of the fuel cell stack 12 is started.

  At the start-up, oxidant gas is supplied along each cathode side electrode 24, while fuel gas is supplied along each anode side electrode 26. As a result, the air supplied to the cathode side electrode 24 and the fuel gas supplied to the anode side electrode 26 react electrochemically to generate power.

  Although not shown, a coolant such as pure water, ethylene glycol, or oil is supplied to the coolant supply passage 34a. The cooling medium flows through each cooling medium flow path 44 to cool the fuel cell 20 and then is discharged to the cooling medium outlet communication hole 34b.

  Further, when power generation by the fuel cell stack 12 is stopped, the valve 80 is opened and the hydrogen supply valve 74c is closed. Therefore, the air supplied to the air supply flow path 62 via the air compressor 60 is supplied to the oxidant gas flow path 38 in the fuel cell stack 12, while a part thereof supplies hydrogen through the connection flow path 78. The fuel gas is supplied from the flow path 72 to the fuel gas flow paths 46 a and 46 b in the fuel cell stack 12. As a result, the oxidant gas flow path 38 and the fuel gas flow paths 46a and 46b are purged with air, and the operation of the fuel cell system 10 is stopped.

  FIG. 5 is an exploded perspective view of a main part of the fuel cell 100 constituting the fuel cell system to which the starting method according to the second embodiment of the present invention is applied. In addition, the same referential mark is attached | subjected to the component same as the fuel cell 20 used for 1st Embodiment, and the detailed description is abbreviate | omitted.

  The fuel cell 100 is configured by sandwiching an electrolyte membrane / electrode structure 102 between a cathode side separator 104 and an anode side separator 106. The surface 29a of the cathode separator 104 facing the electrolyte membrane / electrode structure 102 is provided with, for example, an oxidant gas flow path 108 that is a meandering flow path that folds back and forth by one reciprocal half in the direction of arrow B.

  The inlet side and outlet side of the oxidant gas flow path 108 communicate with the oxidant gas inlet communication hole 32a and the oxidant gas outlet communication hole 32b via the bridge portions 110a and 110b, respectively.

  On the surface 30a of the anode-side separator 106 facing the electrolyte membrane / electrode structure 102, as shown in FIG. 6, for example, fuel gas channels 112a and 112b, which are meandering channels that fold back and forth halfway in the direction of arrow B, are provided. It is provided alternately.

  A throttle portion 54a is provided on the inlet side (fuel gas inlet communication hole 36a side) of the fuel gas channel 112a, while a throttle portion is provided on the outlet side (fuel gas outlet communication hole 36b side) of the fuel gas channel 112b. 54b is provided.

  In the second embodiment configured as described above, as shown in FIG. 6, the fuel gas flow paths 112a and the fuel gas flow paths 112b are alternately provided, and are throttled to the inlet side of the fuel gas flow path 112a. A portion 54a is provided, and a throttle portion 54b is provided on the outlet side of the fuel gas passage 112b.

  For this reason, when hydrogen gas is introduced from the fuel gas inlet communication hole 36a into the fuel gas flow paths 112a and 112b through the plurality of communication holes 52a at the time of start-up, the fuel gas flow path 112b without the throttle portion on the inlet side. The hydrogen gas is preferentially circulated, and a differential pressure of the hydrogen gas pressure is induced between the fuel gas passage 112a with a small hydrogen gas circulation amount. Therefore, in the fuel gas passage 112b through which a large amount of hydrogen gas flows, the fuel gas passage 112b moves toward the throttle portion 54b while meandering along the fuel gas passage 112b, and part of the hydrogen gas flows due to the differential pressure. It moves from the path 112b across the fuel gas flow path 112a.

  As a result, in the second embodiment, as in the first embodiment, the hydrogen gas smoothly flows in the gas diffusion layer facing the peak portions 114a and 114b, and the air remaining in this portion is converted into hydrogen gas. It becomes possible to replace quickly.

  For this reason, the air remaining in at least the entire power generation region of the anode-side electrode 26 can be quickly and surely replaced with hydrogen gas, and the deterioration of the electrode catalyst is prevented as much as possible with a simple process. The same effects as those of the first embodiment can be obtained, such as being able to maintain the power generation performance of the first embodiment.

1 is a schematic configuration diagram of a fuel cell system to which a starting method according to a first embodiment of the present invention is applied. It is a principal part disassembled perspective explanatory drawing of the fuel cell which comprises the said fuel cell system. It is an expanded sectional view of the fuel cell. It is front explanatory drawing of the anode side separator which comprises the said fuel cell. It is a principal part disassembled perspective explanatory drawing of the fuel cell which comprises the fuel cell system with which the starting method which concerns on the 2nd Embodiment of this invention is applied. It is front explanatory drawing of the anode side separator which comprises the said fuel cell. It is sectional explanatory drawing of a common fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 18 ... Controller 20, 100 ... Fuel cell 22 ... Solid polymer electrolyte membrane 24 ... Cathode side electrodes 24a, 26a ... Electrode catalyst Layer 24b, 26b ... Gas diffusion layer 26 ... Anode side electrode 28, 102 ... Electrolyte membrane / electrode structure 29, 30, 104, 106 ... Separator 32a ... Oxidant gas inlet communication hole 32b ... Oxidant gas outlet communication hole 34a ... Cooling medium inlet communication hole 34b ... Cooling medium outlet communication hole 36a ... Fuel gas inlet communication hole 36b ... Fuel gas outlet communication hole 38, 108 ... Oxidant gas flow path 40, 48a, 48b, 114a, 114b ... Mount 42a, 42b , 50a, 50b ... buffer section 44 ... cooling medium flow path 46a, 46b, 112a, 112b ... fuel gas flow path 4a, 54b ... aperture portion 60 ... Air compressor 70 ... hydrogen tank 76 ... ejector 88 ... hydrogen pump

Claims (3)

A plurality of oxidant gas passages for supplying an oxidant gas to the cathode side electrode and a plurality of fuel gas passages for supplying a fuel gas to the anode side electrode; A fuel cell system start-up method comprising a fuel cell for generating electric power, wherein the oxidant gas passage and the fuel gas passage are filled with the oxidant gas, and the operation is stopped.
While supplying the fuel gas to the fuel gas flow path and generating a differential pressure between the adjacent fuel gas flow paths, the oxidant gas that stays in at least the power generation region of the anode side electrode, A starting method for a fuel cell system, characterized by substituting with fuel gas. 2. The starting method according to claim 1, wherein the fuel gas flow paths adjacent to each other are provided with throttle portions alternately on the inlet side of one fuel gas flow path and the outlet side of the other fuel gas flow path,
A method for starting a fuel cell system, wherein the throttle unit is disposed outside the power generation region to replace at least the oxidant gas staying in the power generation region with the fuel gas.   3. The start-up method according to claim 1 or 2, wherein after the fuel gas passage is set to a negative pressure, the oxidant gas is replaced with the fuel gas by supplying the fuel gas to the fuel gas passage. A method for starting a fuel cell system.

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