JP3913465B2 - Fuel cell system - Google Patents

Description

新メタノール技術 Ｐ．１１(サイエンスフォーラム社発行)（昭和６２年）
なお、上記実施の形態１及び実施の形態２の運転停止処理時に、前記バルブ・ポンプ制御装置１００が凍結防止の処理を実行するか否かの判断は、外気温センサの検出温度によって実行したが、操作部に凍結防止処理の選択スイッチを設置し、操作者が前記選択スイッチから処理の指示を入力することでも可能である。このような方法においては、運転停止時に外気温が氷点下になっていない場合であって、その後に外気温が氷点下になることが予測される状況で燃料電池システムを一定時間運転停止する際に、凍結防止の処理を実行できるので有効である。
【００４１】
さらに、上記実施の形態１及び実施の形態２において、燃料電池に供給される燃料ガスは、メタノール水溶液を改質した改質ガスとしたが、水素ボンベから供給の水素ガスなどでも良い。このような燃料電池システムでは、水溶性の有機燃料を供給する手段を別途設置しておくことが必要である。
【００４２】
【発明の効果】
以上のように、本発明の燃料電池システムでは、選択的に水溶性の有機燃料を直接アノードに供給、あるいは、加湿水を介してアノードに供給することにより、燃料電池の内部及び加湿水供給手段の流路内を凝固点が純水に比べて低い水溶性の有機燃料で湿潤することで出来るので、システムの運転停止の後に外気温が氷点下であるような環境下で一定時間システムを放置した場合でも、残留する水分の凍結を防止することが出来る。そして、燃料電池の内部に残留の水溶性の有機燃料は、運転再開時に燃料電池で燃料として消費されるので、前記電池性能は、運転再開後の時間経過とともに回復する。
【００４３】
また、本発明の燃料電池システムは、燃料電池への燃料の供給手段として気体燃料供給手段及び液体燃料供給手段の２つの手段を備え、且つ、前記２つの燃料供給手段を選択的に切り替えが出来るので、改質器のバーナーなどの故障によって通常運転における燃料である気体燃料の供給が停止した場合においても、燃料供給手段を気体燃料供給手段から液体燃料供給手段に切り替えることにより継続して運転を行うことが出来る。
【図面の簡単な説明】
【図１】 実施の形態１にかかる燃料電池システム１の構成の概略を表すブロック図である。
【図２】 燃料電池システム１の運転動作を表すフローチャートである。
【図３】 実施の形態２にかかる燃料電池システム２の構成の概略を表すブロック図である。
【図４】燃料電池システム２の運転動作を表すフローチャートである。
【符号の説明】
１ 燃料電池システム１
２ 燃料電池システム２
１０ 燃料電池
１１ セル
１４ 加湿部
２０ メタノール水溶液タンク
３０ 改質器
４０ 加湿水タンク
５０ メタノール濃度調整装置
１００ バルブ・ポンプ制御装置
１１０ バーナー燃焼温度センサ[0001]
BACKGROUND OF THE INVENTION
The present invention includes a cell in which an anode and a cathode are disposed on an electrolyte membrane, and a function of generating power by supplying an oxidant gas to the cathode and a gaseous fuel to the anode, an oxidant gas to the cathode, and the anode The present invention relates to a fuel cell system having a function of generating power by supplying liquid fuel to the fuel cell system.
[0002]
[Prior art]
A fuel cell has a cell in which an anode and a cathode are arranged on an electrolyte membrane, and generates electricity by supplying fuel and an oxidant gas to the anode and the cathode, respectively, and a rib and a gas channel are formed. In general, a plurality of cell units sandwiched between the separator members formed as a basic structure are stacked. And it is classified into solid polymer type (PEFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid electrolyte type (SOFC), alkaline type (AFC), etc. according to the type of electrolyte used. .
[0003]
Among the above fuel cells, a polymer electrolyte fuel cell (PEFC) using a solid polymer electrolyte membrane, which is a thin film of perfluorocarbon sulfonic acid, as an electrolyte is a low temperature operation type fuel cell, and the electrolyte is dissipated. There is no worry about decomposition or decomposition, and there is no problem of corrosion of surrounding materials. Here, the polymer electrolyte fuel cell is generally operated by supplying a reformed gas containing hydrogen as a main component to the anode, but there is also a battery that generates power by directly supplying a methanol aqueous solution as a fuel. It is said to be a direct methanol fuel cell (DMFC).
[0004]
In the fuel cell system including the above polymer electrolyte fuel cell, the hydrogen-rich reformed gas reformed by the reformer is used as the fuel gas, and the ionic conductivity of the polymer electrolyte membrane which is an electrolyte during the operation In order to ensure this, conventionally, many methods have been employed in which humidified water is supplied to a fuel gas or an oxidant gas while the solid polymer membrane is maintained in a wet state.
[0005]
[Problems to be solved by the invention]
However, the fuel cell system including the above-described conventional polymer electrolyte fuel cell remains in the fuel cell when a certain period of time elapses in an environment where the outside air temperature is below freezing after the operation is stopped. There is a problem that humidified water freezes. Such freezing of the humidified water causes the deterioration of the performance of the fuel cell and the damage of the constituent parts.
[0006]
In order to prevent the above-described problems from freezing when the fuel cell is stopped, a method and system for draining water from the fuel cell (for example, disclosed in JP-A-11-273704), a heater, etc. A method of heating the fuel cell even when the operation of the fuel cell is stopped (for example, disclosed in Japanese Patent Application Laid-Open No. 11-214025) has been proposed.
[0007]
However, even when the method for draining the water in the fuel cell is used, it is difficult to completely drain the water, and the remaining water is frozen in an environment where the outside temperature is below freezing. Can be considered.
In addition, when the above-described method of heating while the operation of the fuel cell is stopped, there is a problem that energy efficiency as a whole system is lowered because energy for heating is required. In addition, in this method, there is a problem that the system becomes large because a device for heating is separately required.
[0008]
As a general anti-freezing method at the time of cold, there is a method using an antifreeze such as ethylene glycol widely used in automobile radiators, but in a fuel cell, the antifreeze remains inside. The above method cannot be used to cause degradation of fuel cell performance.
Further, another problem in the conventional fuel cell system is that when the supply device for supplying fuel gas fails, for example, when the burner of the reformer for supplying fuel gas is turned off, It may stop and power supply will stop. Such stoppage of power supply may have various adverse effects on electrical equipment that is operating with the power supply.
[0009]
The present invention can prevent the freezing of moisture in the fuel cell even when the outside air temperature becomes below freezing point when the operation is stopped, and the supply of gaseous fuel to the fuel cell is stopped. It is an object of the present invention to provide a fuel cell system that can continuously generate power even in the case of failure.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the fuel cell system of the present invention has the following characteristics.
(1) It has a cell in which an anode and a cathode are arranged on an electrolyte membrane, and has a function of generating power by supplying an oxidant gas to the cathode and a gaseous fuel to the anode, an oxidant gas to the cathode, and an anode to the anode. A fuel cell system having a function of supplying liquid fuel and generating electric power, wherein gaseous fuel supply means for supplying gaseous fuel to the anode, and liquid fuel supply means for supplying water-soluble organic fuel to the anode, The fuel supply switching for switching the supply state of the fuel to the anode from the first state mainly composed of the gaseous fuel supply unit to the second state in which the supply ratio of the liquid fuel supply unit is larger than the first state. Means.
[0011]
In this fuel cell system, by providing the gaseous fuel supply means, the liquid fuel supply means and the fuel supply switching means, the fuel cell system normally generates power with high efficiency by operating in the first state. By switching to the second state when an abnormality occurs in the supply of the gaseous fuel, power can be generated continuously by supplying the organic fuel directly to the anode.
[0012]
Further, in this fuel cell system, it is possible to switch to the second state immediately before stopping the operation, and to stop the system after the inside of the fuel cell is moistened with the liquid fuel. By adopting such a stop operation, moisture containing water-soluble organic fuel having a low freezing point remains in the fuel cell, so that freezing hardly occurs even in an environment where the outside air temperature is below freezing point.
[0013]
Further, the liquid fuel remaining in the fuel cell by the operation stop operation as described above is consumed as fuel of the fuel cell by restarting the operation. For this reason, the performance of the fuel cell recovers with the lapse of time of operation.
(2) In the fuel cell system according to (1), in the case where the electrolyte membrane includes humidified water supply means for supplying humidified water for ensuring the ionic conductivity to the anode, the fuel supply switching means includes the liquid The fuel supply means can be switched to the second state by adding a water-soluble organic fuel to the humidified water supplied to the anode by the humidified water supply means.
[0014]
In this fuel cell system, freezing of moisture in the humidified water supply means can be suppressed together with moisture remaining in the fuel cell.
(3) In the fuel cell systems of (1) and (2), if the fuel supply switching means performs switching in response to an instruction to stop the operation of the system, the anti-freezing process can be reliably performed when the operation is stopped. preferable.
(4) In the fuel cell system according to (3), the fuel supply switching means has an instruction to stop the operation of the system, and an environment in which the outside air temperature is below or below freezing. In the case below, it is possible to selectively perform switching.
(5) In the fuel cell system of (1), the fuel supply switching means performs switching of the fuel supply means when an abnormality occurs in the supply of gaseous fuel to the fuel cell by the gaseous fuel supply means. You can also
[0015]
This fuel cell system is supplied to the anode by the liquid fuel supply means when an abnormality occurs in the supply of the gaseous fuel, for example, when the supply of the gaseous fuel is stopped due to, for example, the burner of the reformer disappearing. Can be operated continuously using liquid fuel.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 is a block diagram showing an outline of a fuel cell system 1 according to the first embodiment.
(System configuration)
In FIG. 1, the fuel cell system 1 includes a fuel cell 10, a reformer 30, a methanol aqueous solution tank 20, a humidified water tank 40, and a valve / pump control device 100 as main elements.
[0017]
The fuel cell 10 has a cell 11 in which a cathode and an anode are arranged on the main surface of a solid polymer membrane, a cathode side substrate 12 having an air flow path facing the cathode, and the anode. Thus, the anode side board | substrate 13 provided with the flow path of the fuel and the humidification part 14 which supplies humidification water to the said anode side board | substrate 13 are provided. The humidifying section 14 in the present embodiment is a flow path through which water flows along the fuel flow path of the anode side substrate 13, and is partitioned by the fuel flow path of the anode side substrate 13 and a water permeable plate. It is a thing.
[0018]
Next, the reformer 30 includes a catalyst layer 31 and a burner 32. The catalyst layer 31 is connected to the methanol aqueous solution tank 20 and the fuel supply side of the anode side substrate 13, and the burner 32 is connected to the exhaust side of the anode side substrate 13. In the reformer 30, in the state where the catalyst layer 31 is heated by the combustion of the burner 32, a reforming reaction occurs when an aqueous methanol solution is supplied to the catalyst layer 31, and hydrogen-rich fuel gas is generated. The
[0019]
The humidified water tank 40 is a tank of humidified water supplied to the humidifying unit 14, and a pipe is connected to the humidifying unit 14.
The methanol aqueous solution tank 20 is connected to a pipe having the catalyst layer 31 and a valve 62, and a pipe having a valve 61 is connected to a pipe for supplying humidified water to the humidifying section 14.
[0020]
The valve / pump control apparatus 100 includes an interactive operation unit (not shown), an outside air temperature sensor, and an elapsed time count timer, and controls the opening / closing of the valves 61 and 62 and the operation of the pumps 71 and 72.
(System operation)
The operation of the fuel cell system 1 having the above configuration will be described with reference to FIG.
[0021]
FIG. 2A is a flowchart showing a control operation performed by the valve / pump control apparatus 100, and FIG. 2B is an operation stop processing routine.
First, during the normal operation in step S200 of FIG. 2A, the fuel cell system 1 generates power with high efficiency by using fuel gas. That is, the valve / pump control device 100 closes the valve 61, opens the valve 62, and operates the pumps 71 and 72 together. In the fuel cell system 1 in such a normal operation state, the methanol aqueous solution from the methanol aqueous solution tank 20 is supplied only to the reformer 30, and the supplied methanol aqueous solution is reformed to hydrogen-rich fuel gas. And supplied to the anode side substrate 13. In the fuel cell system 1, the cathode-side substrate 12 is supplied with air as an oxidant gas, and the humidifying unit 14 is supplied with humidified water, which is pure water, from the humidified water tank 40. An electrochemical reaction is generated within 10 to generate power.
[0022]
Next, the control operation performed by the valve / pump control device 100 when the operation of the fuel cell system 1 is stopped will be described.
In step S201 of FIG. 2A, the valve / pump control device 100 executes an operation stop processing routine S202 when the operation stop button in the operation unit is turned on. The control operation of the valve / pump control device 100 in the operation stop processing routine will be described with reference to FIG.
[0023]
In FIG. 2B, when it is determined in step S205 that the outside air temperature is 0 ° C. or lower, the valve / pump control apparatus 100 opens the valve 61 in step S206 and starts the elapsed time count timer in step S207. Then, reading of the elapsed time t is started. In the fuel cell system 1, when the valve 61 is opened, the methanol aqueous solution is added to the humidified water from the methanol aqueous solution tank 20, and the humidified water to which the methanol aqueous solution is added passes through the humidifying unit 14 and the anode side substrate 13. To be supplied. Accordingly, the anode of the cell 11 and the anode side substrate 13 are wetted with the methanol aqueous solution. Thereafter, in step S208, when the elapsed time t of the elapsed time count timer becomes equal to or longer than a preset set time t1, the valve / pump control device 100 ends the operation stop processing routine, and FIG. In step S203, the operation of the system is stopped. After the operation is stopped, the valve / pump control device 100 executes initialization of the valve open / close state in step S204 in preparation for the resumption of operation.
[0024]
When the system operation is stopped as described above, the anode of the cell 11, the anode-side substrate 13, the humidified water flow path, the pump 72, and the like are wet with the methanol aqueous solution, so the system operation is stopped. Even when it is left for a certain period of time in an environment where the outside air temperature is below freezing point, freezing is less likely to occur than when it is wet with pure water.
[0025]
The methanol aqueous solution remaining inside the fuel cell 10 due to the above-described operation stop operation is consumed as fuel of the fuel cell 10 by restarting the operation of the fuel cell system 1.
When it is determined in step S205 that the outside air temperature is not below freezing point, the valve / pump control device 100 ends the operation stop processing routine without executing steps S206 to S208, and in step S203, the fuel cell system 1 Stop operation.
[0026]
In the first embodiment, the anti-freezing process S206 in the operation stop routine is performed by opening the valve 61 while continuing the power generation in the fuel cell 10 by supplying the fuel gas. However, the supply of the fuel gas is stopped. After the power generation is stopped, the valve 61 may be opened and an aqueous methanol solution may be supplied to the fuel cell 10. In short, the fuel cell system of the present invention is considered to be effective when switching is performed so that the supply ratio of the methanol aqueous solution to the anode is larger during the freeze prevention treatment S206 than during the normal operation S200. .
(Embodiment 2)
Next, FIG. 3 is a block diagram showing an outline of the fuel cell system 2 according to the second embodiment.
[0027]
(System configuration)
With respect to the configuration of the fuel cell system 2 according to the second embodiment, differences from the configuration of the fuel cell system 1 will be mainly described with reference to FIG.
In the fuel cell system 2, in addition to the configuration of the fuel cell system 1, a burner combustion temperature sensor 110 for detecting the combustion temperature of the burner 32 of the reformer 30 and the methanol concentration of the aqueous methanol solution are automatically adjusted to an appropriate range. A methanol concentration adjusting device 50 is provided.
[0028]
The methanol aqueous solution tank 20 is connected to a pipe provided with a valve 63 on the anode side substrate 13 so that the methanol aqueous solution can be directly supplied to the anode of the cell 11, and unreacted methanol discharged from the anode side substrate 13. The methanol concentration adjusting device 50 and a pipe are connected so that the aqueous solution can be recovered by the methanol concentration adjusting device 50 and reused. In addition, valves 64 and 65 are provided on the fuel discharge side of the anode side substrate 13. The valves 63, 64, 65 are controlled to be opened and closed by the valve / pump control device 100.
[0029]
In the fuel cell system 2, the pipe having the valve 61 provided for adding the methanol aqueous solution to the humidified water in the fuel cell system 1 is not installed.
(System operation)
Next, the operation of the fuel cell system 2 configured as described above will be described with reference to FIG.
[0030]
FIG. 4A is a flowchart showing the control operation performed by the valve / pump control device 100 in the normal operation of the fuel cell system 2. FIGS. 4B and 4C are a liquid fuel operation routine and an operation stop, respectively. A process (2) routine is shown.
During the normal operation of step S210 in FIG. 4A, the fuel cell system 2 generates power with high efficiency by using fuel gas. In other words, the valve / pump control device 100 opens the valves 62 and 64, closes the valves 63 and 65, and puts the pumps 71 and 72 into operation.
[0031]
When the combustion of the burner 32 is stopped due to a failure or the like in step S211, the burner combustion temperature sensor 110 sends an abnormal signal related to the combustion temperature of the burner 32 to the valve / pump control device 100. Upon receiving the abnormal signal, the valve / pump control device 100 executes the liquid fuel operation routine of step S212.
[0032]
Next, the liquid fuel operation routine will be described with reference to FIG.
In the liquid fuel operation routine of FIG. 4B, the valve / pump control apparatus 100 executes control operations for closing the valve 62, opening the valve 63, closing the valve 64, opening the valve 65, and stopping the pump 72 in step S217. . By executing Step 217, the methanol aqueous solution is directly supplied from the methanol aqueous solution tank 20 to the anode side substrate 13 instead of the fuel gas reformed by the reformer 30 during normal operation. The supplied aqueous methanol solution is used for an electrochemical reaction at the anode of the cell 11 while flowing along the flow path of the anode side substrate 13, and then the unreacted aqueous methanol solution is discharged from the battery. The discharged methanol aqueous solution is recovered in the methanol aqueous solution tank 20 after the methanol concentration is adjusted to an appropriate range in the methanol concentration adjusting device 50. Here, the supply of the humidified water from the humidified water tank 40 is stopped by stopping the operation of the pump 72.
[0033]
In the operation state as described above, the valve / pump control device 100 terminates the operation in the liquid fuel operation routine when the operation stop button in the operation unit is turned ON in step S218, and the system in step S213. Execute the operation stop. When the system is stopped in this manner, the inside of the fuel cell 10 is wetted by the aqueous methanol solution supplied as the fuel. Therefore, after the operation is stopped, the fuel cell 10 is left for a certain period of time in an environment where the outside air temperature is below freezing. However, it is less likely to freeze than when it is wet with pure water.
[0034]
Next, when the abnormality of the burner 32 is not detected in step S211 of FIG. 4A and the fuel cell system 2 is performing the normal operation of step S210, the operation stop button is turned ON in step S215. In this case, the valve / pump control apparatus 100 executes the operation of the operation stop process (2) routine in step S216.
The operation of the operation stop process (2) routine will be described with reference to FIG.
[0035]
In the operation stop process (2) routine of FIG. 4 (c), when the valve / pump control device 100 determines in step S219 that the outside air temperature is 0 ° C. or lower, in step S220 the above-described liquid fuel operation routine is executed. The valve and pump are operated in the same manner as in step S217, and reading of the elapsed time t is started in step S221. Thereafter, in step S222, when the elapsed time t of the elapsed time count timer becomes equal to or longer than the preset time t1, the valve / pump control device 100 ends the operation stop process (2) routine.
[0036]
Then, after the operation stop process (2) routine ends, the valve / pump control device 100 stops the operation of the system in step S213 of FIG. Thereafter, the valve / pump control apparatus 100 executes initialization of the valve open / closed state in step S214 in preparation for resuming operation.
Since the inside of the fuel cell 10 whose operation has been stopped as described above is wetted with the methanol aqueous solution, even if the fuel cell 10 is left for a certain period of time in an environment where the outside air temperature is below freezing after the operation is stopped, Freezing is unlikely to occur compared to when wet.
[0037]
As described above, the fuel cell systems 1 and 2 can be obtained by adding a methanol aqueous solution as fuel to the humidified water or supplying the fuel cell 10 directly as fuel to the fuel cell 10 as necessary before the system is stopped. 11 and the anode-side substrate 13 can be wetted with a methanol aqueous solution having a freezing point lower than that of pure water, and even after being stopped for a certain period of time in an environment where the outside air temperature is below freezing point, Freezing is unlikely to occur compared to wet cases. In addition, in the fuel cell system 1, not only the inside of the fuel cell 10 but also the humidified water supply flow path and the pump 72 are in a state of being wetted with the methanol aqueous solution, so that it is difficult to cause freezing.
[0038]
Further, in the fuel cell system 2, even when the supply of gaseous fuel is stopped due to the failure of the burner 32 or the like, power generation is continuously performed by supplying the methanol aqueous solution directly to the fuel cell 10 by switching the fuel supply. Can be done.
In the second embodiment, the determination of whether or not the supply of gaseous fuel is stopped is performed by detecting the combustion temperature of the burner 32. However, the present invention is not limited to this. The determination may be made by detecting the flow rate of the fuel gas from the reformer 30 to the fuel cell 10 or detecting the output of the fuel cell 10.
[0039]
Here, the methanol concentration of the aqueous methanol solution supplied to the fuel cell 10 is preferably as high as possible within the range that can be used as the fuel of the fuel cell 10 in terms of freezing point depression.
The relationship between the methanol concentration in the methanol aqueous solution and the freezing point is shown in the following table.
[0040]
[Table 1]
Relationship between methanol concentration and freezing point

New methanol technology 11 (published by Science Forum) (1987)
It should be noted that the determination as to whether or not the valve / pump control device 100 executes the anti-freezing process is performed based on the temperature detected by the outside air temperature sensor during the operation stop process of the first and second embodiments. It is also possible to install a selection switch for anti-freezing processing in the operation unit, and the operator inputs a processing instruction from the selection switch. In such a method, when the outside temperature is not below freezing when the operation is stopped, and when the outside temperature is predicted to drop below freezing after that, when the fuel cell system is shut down for a certain period of time, This is effective because anti-freezing processing can be executed.
[0041]
Furthermore, in Embodiment 1 and Embodiment 2 described above, the fuel gas supplied to the fuel cell is a reformed gas obtained by reforming a methanol aqueous solution, but it may be a hydrogen gas supplied from a hydrogen cylinder. In such a fuel cell system, it is necessary to separately install means for supplying water-soluble organic fuel.
[0042]
【The invention's effect】
As described above, in the fuel cell system of the present invention, the water-soluble organic fuel is selectively supplied directly to the anode or supplied to the anode via the humidified water, so that the inside of the fuel cell and the humidified water supply means are provided. When the system is left for a certain period of time in an environment where the outside air temperature is below freezing after the system is shut down, it can be wetted with water-soluble organic fuel whose freezing point is lower than that of pure water. However, it is possible to prevent the remaining water from freezing. The water-soluble organic fuel remaining in the fuel cell is consumed as fuel in the fuel cell when the operation is resumed, so that the cell performance is recovered as time passes after the operation is resumed.
[0043]
The fuel cell system of the present invention includes two means, a gaseous fuel supply means and a liquid fuel supply means, as fuel supply means to the fuel cell, and can selectively switch between the two fuel supply means. Therefore, even when the supply of gaseous fuel, which is fuel in normal operation, is stopped due to a failure such as a reformer burner, the operation is continued by switching the fuel supply means from the gaseous fuel supply means to the liquid fuel supply means. Can be done.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of a configuration of a fuel cell system 1 according to a first embodiment.
FIG. 2 is a flowchart showing the operation of the fuel cell system 1;
FIG. 3 is a block diagram showing an outline of a configuration of a fuel cell system 2 according to a second embodiment.
FIG. 4 is a flowchart showing an operation operation of the fuel cell system 2;
[Explanation of symbols]
1 Fuel cell system 1
2 Fuel cell system 2
DESCRIPTION OF SYMBOLS 10 Fuel cell 11 Cell 14 Humidification part 20 Methanol aqueous solution tank 30 Reformer 40 Humidification water tank 50 Methanol concentration adjustment apparatus 100 Valve pump control apparatus 110 Burner combustion temperature sensor

Claims (5)

It has a cell in which an anode and a cathode are arranged on an electrolyte membrane, and has a function of generating power by supplying an oxidant gas to the cathode, a gaseous fuel to the anode, an oxidant gas to the cathode, and a liquid fuel to the anode. A fuel cell system having a function of supplying and generating power,
Gaseous fuel supply means for supplying gaseous fuel to the anode;
Liquid fuel supply means for supplying water-soluble organic fuel to the anode;
Fuel supply switching means for switching the fuel supply state to the anode from a first state mainly composed of the gaseous fuel supply means to a second state in which the supply ratio of the liquid fuel supply means is larger than the first state. A fuel cell system comprising: A humidifying water supply means for supplying the anode with humidified water for ensuring the ionic conductivity of the electrolyte membrane;
The fuel supply switching means switches to the second state by adding a water-soluble organic fuel to the humidified water supplied to the anode by the humidified water supply means by the liquid fuel supply means. The fuel cell system according to claim 1. 3. The fuel cell system according to claim 1, wherein the fuel supply switching unit performs switching according to an instruction to stop the operation of the system. The fuel supply switching means selectively performs switching when there is an instruction to stop the operation of the system and the outside air temperature is below freezing or in an environment where it is predicted to be below freezing. The fuel cell system according to claim 3, wherein: 2. The fuel cell system according to claim 1, wherein the fuel supply switching means performs switching of the fuel supply means when an abnormality occurs in the supply of gaseous fuel to the fuel cell by the gaseous fuel supply means.

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