JP5086144B2 - Hydrogen production apparatus and method for stopping fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system suitable as a small power source for home use, for example, and to a hydrogen production apparatus used in a fuel cell system or the like.

  A fuel cell has a feature that high efficiency can be obtained because a free energy change caused by a combustion reaction of fuel can be directly taken out as electric energy. In addition to the fact that it does not emit harmful substances, it is being developed for various uses. In particular, solid polymer fuel cells are characterized by high power density, compactness, and operation at low temperatures.

  In recent years, natural gas, city gas, methanol, liquefied petroleum gas (LPG), butane and other hydrocarbon fuels such as desulfurizers that remove sulfur, and hydrocarbon fuels react with steam to reform to hydrogen Reformer, a CO converter for transforming carbon monoxide, a CO remover for removing carbon monoxide, an oxidizer such as hydrogen (reformed gas) and oxygen in the air thus obtained A fuel cell power generation system has been proposed as a compact power source including a fuel cell that generates an electric power by electrochemical reaction (see Patent Documents 1, 2, and 3).

  When fuel gas containing hydrogen is supplied to the fuel electrode and air is supplied to the air electrode, the fuel electrode reacts by decomposing hydrogen molecules into hydrogen ions and electrons. At the air electrode, water is generated from oxygen, hydrogen ions, and electrons. Each electrochemical reaction is performed, and electric power is supplied to the load by electrons moving in the external circuit from the fuel electrode toward the air electrode, and water is generated on the air electrode side.

  FIG. 3 shows a conventional fuel cell power generation system.

  As shown in FIG. 3, the fuel cell power generation system desulfurizes natural gas, city gas, hydrocarbon fuel gas (here, LPG) such as methanol, LPG, and butane through a shut-off valve 302 to a desulfurizer. Thereafter, the water is sent to the fuel reformer 310 through the check valve 340, while the water is sent to the vaporizer through the stop valve 301 to be vaporized, and the steam is sent to the fuel reformer 310 through the check valve 350. The fuel reformer includes a reformer (RF), a CO converter (SH), and a CO remover (PROX). Hydrocarbon fuel and steam are supplied to the reformer, where the fuel gas is reformed into hydrogen, and the resulting reformed gas is sent to a CO converter to transform carbon monoxide in the reformed gas. And then sent to a CO remover to remove carbon monoxide. The hydrogen-containing gas with reduced CO concentration obtained by the fuel reformer 310 is sent to the fuel electrode (AN) of the fuel cell 311 through the shut-off valve 304 and the air is sent to the air electrode (CA) of the fuel cell 311. Thus, power generation is performed by an electrochemical reaction between hydrogen in the reformed gas supplied to the fuel electrode (AN) and oxygen in the air supplied to the air electrode (CA).

  The reaction by steam reforming is an endothermic reaction, and a reformer burner 312 is used as a heating medium for maintaining the reforming reaction.

  The hydrogen-containing gas (fuel electrode off-gas) discharged from the fuel electrode chamber of the fuel cell 311 is supplied to the burner 312 via the closing valve 308, and the fuel gas (LPG) is supplied to the burner 312 via the closing valve 303 as necessary. In addition to this, it is combusted with combustion air to supply the amount of heat necessary for the reforming reaction of the reformer (RF).

  When the fuel cell power generation system is stopped, if the temperature decreases with the outlet open, the pressure in the reactor becomes negative, and external air is introduced into the reactor. A Cu—Zn-based catalyst used for a CO shift catalyst is damaged by air oxidation and progresses in deterioration.

A nitrogen supply path 313 from a nitrogen cylinder provided with an open / close valve is provided in front of the desulfurizer of the fuel gas supply unit, and an open / close valve is provided in the path 314 of the hydrogen-containing gas (fuel electrode off-gas) discharged from the fuel cell 311. When the fuel cell power generation system is stopped, the closing valves 301, 302, and 303 are closed, and nitrogen gas is sent from the nitrogen cylinder to the fuel reformer 310 and the fuel cell 311 through the fuel gas supply unit. In some cases, the inside of the system is replaced with nitrogen gas, for example, by releasing the air from 315 to the atmosphere. However, in the method of using a nitrogen gas cylinder incorporated in the system, it is necessary to check the amount of gas in the nitrogen gas cylinder, replace the nitrogen gas cylinder, etc., and there is a problem that the management of the system becomes complicated and the cost increases.
JP 2003-217620 A JP 2003-217623 A JP 2000-277137 A

  From the above problem, a method of closing the entrance / exit when the fuel cell power generation system is stopped is also conceivable. However, when the temperature is lowered with the inlet / outlet closed, the water vapor in the reactor is condensed and the pressure in the reactor becomes negative. In the case of a fuel cell system, it must be assumed that the operation is stopped at night or when it is not operated for a long time. Therefore, in this case, in order to maintain the negative pressure for a long period of time, there is a problem that the expensive automatic open / close valve corresponding to the negative pressure has to be prepared twice, which increases the cost.

  In Patent Document 3, in order to eliminate the need for a gas cylinder for purge gas, a gas mainly composed of nitrogen and carbon dioxide, which is generated by reacting air with a combustible gas and consuming oxygen as the purge gas, is used. Is described. However, in this case, the oxygen in the air cannot be completely reduced to zero, there is a concern about the impact on the catalyst because it always contains NOx, and the decomposition of hydrocarbons when heavy components such as kerosene are used. There is a problem in that there is a concern about the influence on the catalyst that contains a small amount of substances.

  An object of the present invention is to safely and economically and easily perform a hydrogen production apparatus and a fuel cell without incorporating a nitrogen gas cylinder, a purge gas mechanism, or an expensive automatic open / close valve for negative pressure without suppressing catalyst deterioration. It is to provide a way to stop the system.

  As a result of diligent research on these problems, the present inventors have eliminated the negative pressure by introducing air from the downstream side of the shift catalyst after the shift catalyst temperature has decreased to 40 ° C. or lower in order to eliminate the internal negative pressure due to the temperature drop. The present inventors have completed the present invention by finding a hydrogen production apparatus stopping method for performing the above.

According to the present invention, a reformer equipped with a reforming catalyst capable of promoting a reforming reaction, which obtains a gas containing hydrogen from a raw material for hydrogen production using a reforming reaction;
A shift reactor comprising a shift catalyst, which is a catalyst capable of promoting the shift reaction, which reduces the concentration of carbon monoxide in the outlet gas of the reformer by a shift reaction;
A selective oxidation reactor comprising a selective oxidation catalyst capable of promoting a selective oxidation reaction, wherein the concentration of carbon monoxide in the outlet gas of the shift reactor is reduced by a selective oxidation reaction that selectively oxidizes carbon monoxide;
A method for stopping a hydrogen production apparatus comprising:
Purging the flow path containing the reforming catalyst, shift reaction catalyst and selective oxidation catalyst with steam;
Blocking the flow path from the outside; and
In order to eliminate the negative pressure in the flow path, a hydrogen production apparatus having an air introduction process for introducing air from the downstream side of the shift catalyst to the flow path when the temperature of the shift catalyst becomes 40 ° C. or lower A stopping method is provided.

  In the method for stopping the hydrogen production apparatus, air can be introduced into the flow path from between the shift catalyst and the selective oxidation catalyst in the air introduction step.

  In the hydrogen production apparatus stopping method, air can be introduced into the flow path from the downstream side of the selective oxidation catalyst in the air introduction step.

According to the present invention, a reformer equipped with a reforming catalyst capable of promoting a reforming reaction, which obtains a gas containing hydrogen from a raw material for hydrogen production using a reforming reaction, and an outlet gas of the reformer A shift reactor including a shift catalyst that is a catalyst capable of promoting a shift reaction, which reduces the carbon oxide concentration by a shift reaction, and a concentration of carbon monoxide in an outlet gas of the shift reactor is selectively set to carbon monoxide. A selective oxidation reactor including a selective oxidation catalyst capable of promoting a selective oxidation reaction, which is reduced by a selective oxidation reaction to be oxidized; and a fuel that generates electricity using hydrogen obtained from the hydrogen production apparatus A method for stopping a fuel cell system having a battery, comprising:
Purging the flow path containing the reforming catalyst, shift reaction catalyst and selective oxidation catalyst with steam;
Blocking the flow path from the outside; and
A fuel cell system having an air introduction process for introducing air from the downstream side of the shift catalyst to the flow path when the temperature of the shift catalyst becomes 40 ° C. or lower in order to eliminate the negative pressure in the flow path A stopping method is provided.

  In the fuel cell system stopping method, air can be introduced into the flow path from between the shift catalyst and the selective oxidation catalyst in the air introduction step.

  In the fuel cell system stopping method, air can be introduced into the flow path from the downstream side of the selective oxidation catalyst in the air introduction step.

  According to the present invention, without incorporating a nitrogen gas cylinder, a purge gas mechanism, or an expensive automatic opening / closing valve for negative pressure, the catalyst deterioration can be suppressed, and a hydrogen production apparatus and a fuel system can be safely, economically and easily. A method of stopping is provided.

  In the present invention, the flow path including the reforming catalyst, the shift reaction catalyst, and the selective oxidation catalyst (hereinafter sometimes referred to as a purge region) is purged with steam (steam purge step).

  After the steam purge, the purge region is blocked from the outside (blocking step). The purge region can be shut off from the outside by using an appropriate shut-off valve (not necessarily an automatic open / close valve for negative pressure).

  After the shut-off step, air is introduced into the purge region from the downstream side of the shift catalyst when the temperature of the shift catalyst becomes 40 ° C. or lower (air introduction step). This eliminates the negative pressure in the purge region. In consideration of the temperature distribution of the shift catalyst, air may be introduced when the maximum temperature is 40 ° C. or lower. Moreover, in order to shorten the time for the negative pressure state, it is preferable to introduce air as soon as possible when the temperature of the shift catalyst becomes 40 ° C. or lower.

  In the case of a fuel cell system, the air introduction position can be upstream from the fuel cell. Specifically, it can be downstream of the shift catalyst and upstream of the selective oxidation catalyst, or downstream of the selective oxidation catalyst and upstream of the fuel cell (anode chamber).

  In the case of a hydrogen production apparatus, the position where air is introduced can be upstream from the outlet (hydrogen outlet) of the hydrogen production apparatus. Specifically, it can be downstream of the shift catalyst and upstream of the selective oxidation catalyst, or downstream of the selective oxidation catalyst and upstream of the hydrogen outlet.

  By introducing air into the purge region from the downstream side of the shift catalyst, oxygen can be removed by the shift catalyst, and gas with a reduced oxygen concentration can reach the reforming catalyst. This is effective in terms of protecting the reforming catalyst.

  Since the purge area has a negative pressure, the atmosphere (air) can be introduced into the purge area by opening the purge area to the atmosphere (air naturally flows in).

  In the air introduction step, air can be introduced into the purge region from the downstream side of the selective oxidation catalyst. Alternatively, in the air introduction step, air can be introduced into the purge region from between the shift catalyst and the selective oxidation catalyst. From the viewpoint of protecting the selective oxidation catalyst, the latter is preferable to the former.

  Hereinafter, although the suitable form of the present invention is explained in detail using a drawing, the present invention is not limited by this.

  FIG. 1 and FIG. 2 are schematic flow diagrams illustrating examples of solid polymer fuel cell power generation systems to which the present invention can be applied.

  In the fuel cell system shown in FIG. 1, hydrocarbon fuel (here, liquid) in the fuel tank 3 flows into the desulfurizer 5 through the fuel pump 4. At this time, the hydrogen-containing gas from the selective oxidation reactor 11 can be added if necessary. The desulfurizer 5 can be filled with a desulfurizing agent such as a copper-zinc-based or nickel-zinc-based sorbent.

  The hydrocarbon fuel desulfurized by the desulfurizer 5 is mixed with water from the water tank 1 through the water pump 2 and then introduced into the vaporizer 6. The hydrocarbon fuel and water are vaporized by the vaporizer and fed into the reformer 7.

  The reformer 7 is heated by a heating burner 18. The fuel of the heating burner 18 is mainly the anode off-gas (gas discharged from the anode chamber) of the fuel cell 17, but the fuel discharged from the fuel pump 4 can also be used if necessary. As the catalyst charged in the reformer 7, a nickel-based, ruthenium-based or rhodium-based reforming catalyst can be used.

  The reformed gas containing hydrogen and carbon monoxide thus produced is sent to the low temperature shift reactor 10 following the high temperature shift reactor 9 via the vaporizer. In the vaporizer, the sensible heat of the reformed gas is used for vaporization.

In these shift reactors, a shift reaction (CO + H ₂ O → H ₂ + CO ₂ ) is performed. The high temperature shift reactor 9 is filled with an iron-chromium catalyst, and the low temperature shift reactor 10 is filled with a catalyst such as a copper-zinc catalyst.

  The gas obtained by the high temperature shift reactor 9 and the low temperature shift reactor 10 is then led to the selective oxidation reactor 11. The selective oxidation reactor 11 is filled with a Ru-based or Pt-based selective oxidation catalyst. The shift reactor outlet gas (especially the low temperature shift reactor outlet gas) is mixed with the air supplied from the air blower 8, and the selective oxidation of carbon monoxide is performed in the selective oxidation reactor 11 in the presence of the catalyst. Is called. By this method, the carbon monoxide concentration is reduced to such an extent that it does not affect the characteristics of the fuel cell.

  The polymer electrolyte fuel cell 17 has an anode 12, a cathode 13, and a solid polymer electrolyte 14. On the anode (fuel electrode) side, a gas (selective oxidation reactor outlet gas) containing high-purity hydrogen with a reduced carbon monoxide concentration obtained by the above method is shown, and on the cathode (air electrode) side, air is contained. If necessary, the air sent from the blower 8 is introduced after a suitable humidification process (a humidifier is not shown). At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds at the anode, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds at the cathode. In order to promote these reactions, platinum black and Pt catalyst or Pt-Ru alloy catalyst supported on activated carbon are used for the anode, and platinum black and Pt catalyst supported on activated carbon are used for the cathode. In general, both the anode and cathode catalysts are formed into a porous catalyst layer together with polytetrafluoroethylene, a low molecular weight polymer electrolyte membrane material, activated carbon and the like as necessary.

  In the assembly of the polymer electrolyte fuel cell, a polymer electrolyte membrane known by a trade name such as Nafion (manufactured by DuPont), Gore (manufactured by Gore), Flemion (manufactured by Asahi Glass), Aciplex (manufactured by Asahi Kasei), etc. The aforementioned porous catalyst layer is laminated on both sides of the substrate to form MEA (Membrane Electrode Assembly). Further, the fuel cell is assembled by sandwiching the MEA with a separator having a gas supply function, a current collecting function, particularly an important drainage function in the cathode, and the like made of a metal material, graphite, carbon composite and the like.

  The electric load 15 is electrically connected to the anode and the cathode. The anode off gas is consumed in the heating burner 18. The cathode off gas is discharged from the exhaust port 16.

  In the fuel cell system shown in FIG. 1, steam purge is performed when the fuel cell system is stopped or when the hydrogen production apparatus is stopped. The region where steam purge is to be performed is a flow path including at least a reforming catalyst, a shift reaction catalyst, and a selective oxidation catalyst. In order to perform the steam purge, specifically, the fuel pump 4 is stopped and the stop valve 20 is closed from the state where hydrogen is produced. Now, the steam purge state is established.

  After the steam purge, the shut-off valves 19 to 22 are closed to create a sealed state inside the hydrogen production apparatus. That is, the above-described purge region (the flow path including at least the reforming catalyst, the shift reaction catalyst, and the selective oxidation catalyst) is blocked from the outside to form a closed space. At this time, the stop valve 23 is also closed.

  After that, due to the temperature drop, the inside of the purged area, which is a closed space, is in a negative pressure state. The shut-off valve 23 is opened, and air is gradually introduced by the air introduction flow restriction restrictor 24 to eliminate the negative pressure.

  When air is introduced, the shift catalyst may react with oxygen and generate heat. It is preferable to suppress this heat generation from the viewpoint of protecting the shift catalyst. For this purpose, it is effective to limit the air introduction flow rate. An air introduction flow restriction restrictor can be used for this purpose. Specifically, a needle valve or a capillary tube can be used. With the restriction for restricting the air introduction flow rate, the flow rate can be reduced to 1/10 or less with respect to the natural introduction flow rate caused by the decompression.

Also in the fuel cell system in the form shown in FIG. 2, at the time when or hydrogen production apparatus stops the fuel cell system is stopped, after the steam purging as in the embodiment shown in FIG. 1, the hydrogen by closing the shutoff valve 19-22 Create a sealed condition inside the manufacturing equipment. At this time, the stop valve 23 is also closed.

  Due to the temperature drop, the inside of the purged area, which is a closed space, is in a negative pressure state. The air is gradually introduced by the air introduction flow restriction restrictor 24 to eliminate the negative pressure.

The difference between the configuration shown in FIG. 1 and the configuration shown in FIG. 2 is the position where the air introduction shut-off valve 23 and the air introduction flow restriction restrictor 24 are connected.

  Normally, hydrocarbon fuels (raw fuels) that are starting materials for fuel gas for fuel cells include natural gas, LPG, naphtha, kerosene, gasoline or various equivalents thereof, methane, ethane, propane, Hydrocarbons such as butane, various alcohols such as methanol and ethanol, and ethers such as dimethyl ether are used.

  The method for reforming the raw fuel is not particularly limited, and various methods such as a steam reforming method, a partial oxidation reforming method, and autothermal reforming can be used. Any of these methods can be employed in the present invention.

If the raw fuel containing sulfur is supplied to the reforming process as it is, the reforming catalyst will be poisoned, the activity of the reforming catalyst will not be expressed, and the life will be shortened. Prior to this, it is preferable to desulfurize the raw fuel. The conditions for the desulfurization reaction vary depending on the state of the raw fuel and the sulfur content, and thus cannot be generally stated, but the reaction temperature is usually preferably from room temperature to 450 ° C, particularly preferably from room temperature to 300 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. If the space velocity (SV) of the raw material is liquid is preferably in the range of 0.01～15H ^-1 at a liquid hourly space velocity (LHSV), more preferably in the range of 0.05~5h ^-1, 0.1~3h ^- A range of ¹ is particularly preferred. When using a gas precursor is preferably in the range of 100～10,000H ^-1 gas hourly space velocity (GHSV), more preferably in the range of 200～5,000H ^-1, in particular in the range of 300～2,000H ^-1 preferable. SV is a value based on 0 ° C. and atmospheric pressure (0.10 MPa).

Further, although the reforming reaction conditions are not necessarily limited, usually the reaction temperature is preferably 200 to 1000 ° C, particularly preferably 500 to 850 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. GHSV is preferably from 100～100,000H ^-1, more preferably 300~50,000h ^-1, 500~30,000h ^-1 is particularly preferred.

  The gas (reformed gas) obtained by the reforming reaction contains hydrogen as a main component, but other components include carbon monoxide, carbon dioxide, water vapor, and the like.

Reduction of carbon monoxide concentration is made more effective by a method in which carbon monoxide in the reformed gas is reacted with water vapor and converted into hydrogen and carbon dioxide, so-called water gas shift reaction. The reaction conditions for the water gas shift reaction are not necessarily limited depending on the composition of the reformed gas and the like, but the reaction temperature is usually preferably 120 to 500 ° C, and particularly preferably 150 to 450 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. GHSV is preferably 100~50,000h ^-1, especially 300～10,000H ^-1 are preferred.

  In the selective oxidation reaction of carbon monoxide, the concentration of carbon monoxide in the introduced gas is usually 0.1 to 2% by volume, and the hydrogen concentration is usually 40 to 85% by volume. Here, an oxygen-containing gas is introduced to carry out the reaction. Although it does not specifically limit as oxygen-containing gas, Air and oxygen are mentioned. The oxygen-containing gas to be introduced is supplied so that the molar ratio of oxygen in the oxygen-containing gas and carbon monoxide in the raw material gas is not particularly limited, but is in the range of 0.5 to 3.0. preferable. For example, when the carbon monoxide concentration in the raw material gas is 0.5% by volume, the molar ratio is more preferably in the range of 0.5 to 2.5. If the molar ratio is 0.5 or more, the oxidation reaction with carbon monoxide proceeds well. Moreover, if the molar ratio is 3.0 or less, a decrease in hydrogen concentration due to hydrogen oxidation reaction, side reactions such as an increase in reaction temperature due to the heat of oxidation of hydrogen and generation of methane can be suppressed.

When performing the selective oxidation reaction of carbon monoxide in the raw material gas containing hydrogen and carbon monoxide, the reaction pressure is preferably in the range of normal pressure to 1 MPa in consideration of the economics and safety of the fuel cell system, In particular, normal pressure to 0.2 MPa is preferable. The reaction temperature is not particularly limited as long as it lowers the carbon monoxide concentration. However, the reaction rate is slow at low temperatures and the selectivity decreases at high temperatures. 100-300 degreeC is preferable. And advanced ease of oxidation of carbon monoxide, in view of the size of the device, preferably in the range of 1,000～50,000H ^-1, in particular in the range of 3,000～30,000H ^-1 are preferred.

  As described above, by subjecting the reformed gas to a shift reaction and a selective oxidation reaction, the carbon monoxide concentration in the raw material gas is preferably reduced to 100 volppm or less, more preferably 50 volppm or less, and most preferably 10 volppm or less. Can do. By using fuel gas with reduced carbon monoxide concentration, poisoning and deterioration of the noble metal catalyst used in the electrodes of the fuel cell are suppressed, and it is possible to maintain a long life while maintaining high power generation efficiency. It becomes possible.

It is a flowchart for demonstrating one form of the fuel cell system which can implement this invention. It is a flowchart for demonstrating another form of the fuel cell system which can implement this invention. It is a schematic diagram for demonstrating the conventional fuel cell power generation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water tank 2 Water pump 3 Fuel tank 4 Fuel pump 5 Desulfurizer 6 Vaporizer 7 Reformer 8 Air blower 9 High temperature shift reactor 10 Low temperature shift reactor 11 Selective oxidation reactor 12 Anode 13 Cathode 14 Solid polymer electrolyte 15 Electric load 16 Exhaust port 17 Polymer polymer fuel cell 18 Heating burner 19-22 Shut-off valve 23 Air introduction shut-off valve 24 Air introduction flow rate restricting throttle 301, 302, 303, 304, 308 Shut-off valve 310 Fuel reforming Device 311 Fuel cell 312 Burner 340, 350 Check valve

Claims (6)

A reformer comprising a reforming catalyst capable of promoting a reforming reaction, obtaining a gas containing hydrogen from a raw material for hydrogen production using a reforming reaction;
A shift reactor comprising a shift catalyst, which is a catalyst capable of promoting the shift reaction, which reduces the concentration of carbon monoxide in the outlet gas of the reformer by a shift reaction;
A selective oxidation reactor comprising a selective oxidation catalyst capable of promoting a selective oxidation reaction, wherein the concentration of carbon monoxide in the outlet gas of the shift reactor is reduced by a selective oxidation reaction that selectively oxidizes carbon monoxide;
A method for stopping a hydrogen production apparatus comprising:
Purging the flow path containing the reforming catalyst, shift reaction catalyst and selective oxidation catalyst with steam;
Blocking the flow path from the outside; and
In order to eliminate the negative pressure in the flow path, a hydrogen production apparatus having an air introduction process for introducing air from the downstream side of the shift catalyst to the flow path when the temperature of the shift catalyst becomes 40 ° C. or lower How to stop.   The method according to claim 1, wherein in the air introduction step, air is introduced into the flow path from between the shift catalyst and the selective oxidation catalyst.   The method according to claim 1, wherein air is introduced into the flow path from the downstream side of the selective oxidation catalyst in the air introduction step. A reformer equipped with a reforming catalyst capable of promoting a reforming reaction to obtain a gas containing hydrogen from a raw material for hydrogen production using a reforming reaction, and a carbon monoxide concentration in an outlet gas of the reformer A shift reactor including a shift catalyst that is a catalyst that can promote the shift reaction, which is reduced by the shift reaction, and a selective oxidation that selectively oxidizes carbon monoxide in the outlet gas of the shift reactor. A selective oxidation reactor comprising a selective oxidation catalyst capable of promoting a selective oxidation reaction that is reduced by the reaction; and a fuel having a fuel cell that generates power using hydrogen obtained from the hydrogen production apparatus A method for stopping a battery system,
Purging the flow path containing the reforming catalyst, shift reaction catalyst and selective oxidation catalyst with steam;
Blocking the flow path from the outside; and
A fuel cell system having an air introduction process for introducing air from the downstream side of the shift catalyst to the flow path when the temperature of the shift catalyst becomes 40 ° C. or lower in order to eliminate the negative pressure in the flow path How to stop.   The method according to claim 4, wherein in the air introduction step, air is introduced into the flow path from between the shift catalyst and the selective oxidation catalyst.   The method according to claim 4, wherein in the air introduction step, air is introduced into the flow path from the downstream side of the selective oxidation catalyst.

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