JP2005317264A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system quickly and sufficiently removing the moisture remained in the system after stopping the operation for a quick start of following operation. <P>SOLUTION: The fuel cell system comprises electric heaters 31a, 31b, 31c corresponding to a purge valve 27 controlling the exhaustion of anode off-gas, a cathode pressure control valve 28 controlling the pressure of cathode gas, and a pressure sensor 30c detecting the pressure of the anode off-gas respectively. When stopping the operation, the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c are heated, and moisture adhered thereto is removed by making the electric heaters 31a, 31b, 31c operate selectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that sufficiently and quickly removes moisture remaining in a system after operation is stopped.

  2. Description of the Related Art Conventionally, in fuel cell systems that are used in a low temperature environment, examples of fuel cell systems that can remove moisture inside the fuel cell after the system is stopped are those described in the following documents, for example. (See Patent Document 1).

In the system described in this document, after the normal operation of the system is stopped, the dry gas is supplied to at least one of the air path and the hydrogen path, and moisture in the fuel cell is contained in the dry gas to form the wet gas. Are discharged from the fuel cell. The air path is provided with a circulation path that connects the downstream side of the fuel cell and the upstream side of the fuel cell, and the wet gas discharged from the fuel cell is circulated through the circulation path to the air path, thereby remaining heat of the fuel cell. Recover. A gas compressor is disposed on the upstream side of the fuel cell in the air path and on the downstream side of the connection with the circulation path. Further, a water separation storage means for separating moisture from the wet gas is provided.
JP 2002-208422

  In such a conventional fuel cell system, when moisture remaining in the dry gas circulating in the system is contained, the moisture must be vaporized by residual heat of the fuel cell and system components. For this reason, it takes a considerable amount of time for the moisture in the system to be contained in the dry gas and discharged to the outside, which in turn causes a problem that it takes a long time to completely stop the system. It was.

  Also, depending on the shape of the system components, sufficient vaporization characteristics could not be obtained due to factors such as stagnant wet gas flow. For this reason, when moisture remains in the system and the system temperature becomes below freezing after the system is stopped, there is a problem that the moisture remaining in the system may freeze and hinder the operation of the system components.

  Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a fuel cell system capable of sufficiently and quickly removing moisture remaining in the system after operation stop. .

  In order to achieve the above object, means for solving the problems of the present invention are supplied from a fuel gas supply means for supplying a fuel gas, an oxidant gas supply means for supplying an oxidant gas, and the fuel gas supply means. A fuel cell stack for generating power by reacting a fuel gas with an oxidant gas supplied from the oxidant gas supply means, and a fuel gas discharge means for discharging the fuel off-gas discharged from the fuel cell stack to the outside of the system And an oxidant gas discharge means for discharging the oxidant off-gas discharged from the fuel cell stack to the outside of the system, wherein the fuel gas supply means, the fuel gas discharge means, and the oxidant gas When installed in at least one of the discharge means and the system is stopped, the fuel gas supply means, the fuel gas discharge means, etc. Characterized in that it has a heating means for heating at least one of the oxidizing gas discharging means each time.

  According to the present invention, moisture adhering to the fuel gas supply means, the fuel gas discharge means, and the oxidant gas discharge means can be quickly and sufficiently removed. This prevents the fuel gas supply means, fuel gas discharge means, and oxidant gas discharge means from freezing even when the system temperature is below freezing at the next system start-up, allowing the system to be started quickly. It becomes.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to Embodiment 1 of the present invention. The system of the first embodiment shown in FIG. 1 supplies hydrogen to the anode electrode 4 from the fuel gas (here, hydrogen) supply device 1 through the anode gas supply pipe 11 and supplies the oxidant gas (here, air) supply device 2. Then, air is supplied to the cathode 5 via the cathode gas supply pipe 14, and hydrogen and air are reacted in the fuel cell stack 3 to generate electric power. At that time, the anode off gas remaining without being consumed is discharged from the anode electrode 4. Further, a part of oxygen is consumed at the cathode electrode 5, and a cathode off gas containing moisture generated by power generation is discharged from the cathode electrode 5.

  During normal operation of the system, the anode off-gas is supplied to the anode off-gas circulation pipe 12 via the anode off-gas circulation pipe 12 by an anode off-gas circulation apparatus (ReC) 6 constituted by an ejector installed as a part of the fuel gas supply apparatus 1. The whole is circulated and mixed with the supplied hydrogen to form an anode gas, which is supplied again to the anode electrode 4. On the other hand, the cathode off gas has a cathode gas pressure adjusted by adjusting the opening degree of the cathode off gas supply pipe 15, a humidifier (Hu) 10 composed of a membrane humidifier for humidifying the air supplied to the fuel cell stack 3. After being supplied to a mixer (Mixer) 7 via a cathode pressure control valve 28 constituted by a pressure regulating valve to be controlled, it is exhausted to the outside through an exhaust pipe 19.

  Such a fuel cell system is controlled by a system controller. The system controller 33 functions as a control center for controlling the operation of the system and is necessary for a computer that controls various operation processes based on a program. This is realized by, for example, a microcomputer provided with resources such as a CPU, a storage device, and an input / output device. The system controller 33 reads a signal from each sensor in the system and sends a command to each component of the system including the electric heaters 31a, 31b, and 31c based on a control logic (program) stored in advance. All operations necessary for operation / stop of the system described below are managed and controlled in an integrated manner.

  The system controller 33 is supplied with power from a battery 25 mounted on the vehicle when the system is for example a vehicle, and performs various processing operations on the power supplied from the battery 25 when power generation is not performed in the system. Use as power. The system controller 33 selects whether or not to operate the electric heaters 31a, 31b, and 31c based on the selection signal given from the operation selection means 24.

  When the system is stopped, the operation selection means 24 operates the electric heaters 31a, 31b, 31c, and selects whether to heat the valves and sensors corresponding to the electric heaters 31a, 31b, 31c. It functions as a selection means for giving a selection signal to the system controller 33, and is composed of, for example, a changeover switch. The operation selection means 24 is operated at the discretion of the system operator. Alternatively, based on data (operating conditions) that allows the system controller 33 to determine that the system may be operated in an environment below freezing point, such as a calendar, a temperature trend during a predetermined period, or an outside air temperature when a system stop command is transmitted. The system controller 33 is selectively operated.

  Such a system controller 33 includes voltage detection means 32 that detects the output voltage of the fuel cell stack 3. When the voltage detection means 32 detects a voltage lower than a preset threshold value, the voltage detection means 32 is configured by a shutoff valve installed in the anode offgas circulation device 6 based on a purge command transmitted from the system controller 33. The anode off gas is discharged to the mixer 7 through the purge valve 27 and the anode off gas supply pipe 13. At the same time, the hydrogen supply pressure to the fuel cell stack 3 is kept constant by the fuel gas supply device 1 so that the hydrogen supply flow rate from the fuel gas supply device 1 is increased by the same amount as the anode off gas flow rate. At this time, the supply air flow rate is also increased according to the operating conditions so that the hydrogen concentration in the air-fuel mixture becomes less than the combustible concentration.

  When the anode off gas is supplied via the purge valve 27, the mixer 7 mixes the anode off gas and the cathode off gas to form an air-fuel mixture having a hydrogen concentration lower than the combustible concentration. Here, the purge valve 27, the cathode pressure control valve, which is disposed at a position where the humidified gas flows and the water adhering to the inside may freeze and not function normally when the system is left below freezing point. 28. The pressure sensor 30c that is installed in the outlet hydrogen pipe of the fuel cell stack 3 and detects the pressure of the anode off gas includes a corresponding valve and electric heaters 31a, 31b, 31c as heating means for heating the sensor, and corresponding Temperature sensors 29d, 29h, and 29c are installed as temperature detecting means for detecting the temperature of the valve and the sensor.

  The purge valve 27 functions as a constituent member that constitutes a fuel gas discharge unit that discharges the fuel off-gas discharged from the fuel cell stack 3 to the outside of the system, and the cathode pressure control valve 28 is discharged from the fuel cell stack 3. The pressure sensor 30c functions as a constituent member that constitutes a fuel gas supply means for supplying the fuel gas to the fuel cell stack 3 and functions as a constituent member that constitutes an oxidant gas discharge means for discharging the oxidant off-gas to the outside of the system. To do.

  The electric heaters 31a, 31b, and 31c are configured to be able to heat the corresponding valves and sensors and to determine whether the heating has ended based on an energization command from the system controller 33. The electric heaters 31a, 31b, and 31c are composed of electric heaters having a self-temperature adjusting function such as PTC heaters, and are set so that the temperature is saturated below the heat resistance temperature of the peripheral components installed, and are always energized. Even so, the heater temperature is automatically adjusted so that the performance of the peripheral parts is not deteriorated. Here, for example, the saturation temperature is set to about 110 ° C. as a temperature higher than the boiling point of water.

  The anode gas supply pipe 11 is provided with a hydrogen heater (Hex) 8 composed of a heat exchanger that heats the hydrogen supplied to the fuel cell stack 3 by a refrigerant to a desired temperature. The refrigerant sent from the fuel cell stack 3 through the hydrogen heater 8 is driven by the refrigerant pump 21 and flows into the three-way valve 22. The three-way valve 22 supplies the refrigerant supplied to the fuel cell stack 3 to the refrigerant bypass pipe 23 that bypasses the refrigerant cooling device (Rad) 9 when the fuel cell stack 3 is not sufficiently warmed at the time of system startup. It is a flow-path switching valve for doing. The opening of the three-way valve 22 is adjusted by the system controller 33 based on the refrigerant temperature detected by the temperature sensor 29j installed in the refrigerant passage 20 through which the refrigerant circulates through the fuel cell stack. Control is performed to adjust the temperature of the refrigerant on the side to an appropriate temperature.

  On the hydrogen outlet side of the fuel gas supply device 1, a pressure sensor 30 a that detects the hydrogen pressure on the outlet side of the fuel gas supply device 1 and a temperature sensor 29 a that detects the temperature of hydrogen are provided, and the oxidant gas supply device 2. On the air outlet side, a pressure sensor 30b for detecting the pressure of the air on the outlet side of the oxidant gas supply device 2 and a temperature sensor 29b for detecting the temperature of the air are provided. Further, the anode gas supply pipe 11 between the hydrogen heater 8 and the fuel cell stack 3 is provided with a temperature sensor 29e for detecting the temperature of hydrogen at this portion, and between the humidifier 10 and the fuel cell stack 3 is provided. The cathode gas supply pipe 14 is provided with a temperature sensor 29f for detecting the temperature of the air in this part. Further, a temperature sensor 29 h that detects the temperature of the cathode off-gas flowing into the mixer 7 is provided between the cathode pressure control valve 28 and the mixer 7, and from the mixer 7 on the outlet side of the mixer 7. A temperature sensor 29g for detecting the temperature of the discharged exhaust gas is provided.

  Next, the operation of the first embodiment will be described with reference to the flowchart of FIG. 2 showing the procedure of removing moisture and FIG. FIG. 3 shows the system purge timing, the amount of power generated by the fuel cell stack 3, the energization (on) / non-energization (off) timing of the electric heaters 31a, 31b, 31c, and the temperature of the purge valve 27 and the cathode pressure control valve 28. It is a figure showing a change.

  2, after a system stop command is transmitted from the system controller 33 (step S201), it is determined whether or not the operation of the electric heaters 31a, 31b, 31c is selected by the operation selection means 24 (step S201). S202) If the operation is not selected, the electric heaters 31a, 31b, 31c are not energized, and the system is stopped by a normal stop procedure (step S203).

  On the other hand, if the system operator has selected to operate the electric heaters 31a, 31b, 31c by the operation selection means 24, first, the purge valve 27 that needs to be heated by the electric heaters 31a, 31b, 31c, The temperatures of the cathode pressure control valve 28 and the pressure sensor 30c are detected by the corresponding temperature sensors 29d, 29h, 29c (step S204), and according to the lowest energization start temperature detected by the temperature sensors 29d, 29h, 29c. After setting the energizing time of each of the electric heaters 31a, 31b, 31c to the preset energizing time (step S205), the electric heater is used using the electric power obtained by the power generation continued in this system. Energization of 31a, 31b, 31c is started (step S206). Furthermore, the load of the fuel cell stack 3 is adjusted and set to the total power of the power required for stopping the system and the power required for the electric heaters 31a, 31b, 31c, and the power generation is continued (step S207).

  When the electric heaters 31a, 31b, 31c are energized, as shown in FIG. 3, the temperature of the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c is decreased with respect to the surrounding temperature. It rises (indicated by the solid line). Thus, by forcibly heating with the electric heaters 31a, 31b, and 31c, the sealing portion and the sliding portion of the purge valve 27, the cathode pressure control valve 28, and the pressure receiving portion and the pressure introducing portion of the pressure sensor 30c are used. Vaporize adhering moisture.

  At this time, in order to vaporize water adhering to the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c, sensible heat for heating to the boiling point of water and vaporization heat for vaporizing water are required. It becomes. However, when the system temperature is raised to a preset system operating temperature, the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c are heated to reduce the sensible heat to reduce the water. The time and energy required for vaporization of can be reduced as much as possible.

  Here, since the electric heaters 31a, 31b, and 31c are energized while the power generation of the fuel cell stack 3 is continued, even if the heating time is relatively long and the necessary power is increased, the amount of power stored in the battery 25 depends. The electric heaters 31a, 31b, 31c can be energized. In addition, water is generated in the fuel cell stack 3 along with power generation, but since it is heated above the boiling point of water by the electric heaters 31a, 31b, 31c, the purge valve 27, the cathode pressure control valve 28, and the pressure sensor. The water produced | generated by 30c does not condense.

  Next, as shown in FIG. 3, the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c reach a predetermined saturation temperature due to heating, and the energization time of the electric heaters 31a, 31b, 31c is the same as that of the previous step S205. It is determined whether or not the set energization time set in (i) has elapsed (step S208). If elapses, the energization of each electric heater 31a, 31b, 31c is stopped (step S209), and the fuel cell stack 3 Stop power generation. The energization of each of the electric heaters 31a, 31b, 31c may be stopped when the detected temperature reaches a predetermined temperature based on the temperature detected by the corresponding temperature sensor 29d, 29h, 29c. .

  Subsequently, immediately after the power generation is stopped, or when it is determined whether or not a predetermined time has elapsed since the stop of energization (step S210), the fuel gas supply device 1 and the oxidant gas supply are performed using the power of the battery 25. The apparatus 2 is driven to supply hydrogen and air to the fuel cell stack 3, respectively, thereby purging the system (step S211). At that time, the supply amount of hydrogen and air is adjusted so that the air-fuel mixture discharged via the mixer 7 has a hydrogen concentration of less than the flammable concentration, for example, a hydrogen concentration of less than 4%. It is determined whether or not a predetermined time has elapsed after the start of the purge (step S212). If the predetermined time has elapsed, the purge process is terminated and the entire system stop is completed (step S213).

  In the first embodiment, there is a possibility that water vapor in the gas remaining in the system may condense in the process of cooling the system after the energization of the electric heaters 31a, 31b, 31c is stopped, but the purge valve 27 and the cathode pressure control valve 28 are condensed. In addition, since the pressure sensor 30c is stopped at a relatively high temperature in the system, the degree of water condensation can be reduced compared to peripheral parts that are not heated, and the amount of water attached can be reduced. That is, since the temperature of the peripheral components is lower than that of the heated purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c, the condensation of water is more likely to occur in the peripheral components. The amount of water condensation in the cathode pressure control valve 28 and the pressure sensor 30c can be suppressed to be relatively low.

  As a result, water adhering to the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c can be vaporized and eliminated as much as possible. The purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c are prevented from freezing and failing to function, and the system can be quickly started up without requiring special work such as thawing work. Alternatively, even when the thawing work of the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c is necessary, the thawing time spent for the thawing work can be shortened, and the system can be started quickly. Can do.

  Moreover, it becomes easy to ensure a heat source by setting it as the structure which the electric heaters 31a, 31b, 31c generate heat electrically. In addition, when heating means by combustion is used, water is generated with combustion, and measures are required to prevent the generated water from freezing. Can be prevented.

  By operating the electric heaters 31a, 31b, 31c before stopping the power generation of the fuel cell stack 3, the electric power required for the operation of the electric heaters 31a, 31b, 31c is generated, and the purge valve 27, the cathode pressure Water adhering to the control valve 28 and the pressure sensor 30c can be sufficiently removed. Thereby, the capacity | capacitance of auxiliary power supplies, such as the battery 25, can be made small and a system can be comprised compactly.

  When the heating of the purge valve 27, the cathode pressure control valve 28 and the pressure sensor 30c is unnecessary by controlling the operation of the operation selection means based on the system operator or the operating conditions of the system, the energy is not heated. Can avoid unnecessary consumption.

  The electric heaters 31a, 31b, and 31c are set based on a set energization time obtained experimentally in advance, or based on temperatures detected by the temperature sensors 29d, 29h, and 29c provided in the electric heaters 31a, 31b, and 31c. By adopting a configuration in which heating is stopped, consumption of electric power and fuel more than necessary for heating can be suppressed.

  When the system is shut down, the interior of the system is purged with gas, whereby the water vapor after the water adhering to the system components including the purge valve 27, the cathode pressure control valve 28, and the pressure sensor 30c is evaporated is discharged out of the system. Condensation and freezing of water when the system temperature decreases can be reduced as much as possible.

  FIG. 4 is a diagram showing a configuration of a fuel cell system according to Embodiment 2 of the present invention. The feature of the second embodiment shown in FIG. 4 is that the system configuration is the same as that shown in FIG. 1, but a power source other than the fuel cell stack 3, for example, an external power source 26 such as a household power source is provided. The electric heaters 31a, 31b, 31c are energized using the electric power supplied from the external power supply 26 after the power generation of the fuel cell stack 3 is stopped after being connected to the system. It is the same.

  FIG. 5 is a flowchart showing the procedure of removing moisture in the second embodiment. FIG. 6 shows the system purge timing, the amount of power generated by the fuel cell stack 3, the energization of the electric heaters 31a, 31b, and 31c in the second embodiment. FIG. 6 is a diagram illustrating time variation of on / non-energization (off) timing and temperatures of the purge valve 27 and the cathode pressure control valve 28;

  A feature of the procedure shown in FIG. 5 is that, compared with the procedure shown in FIG. 2, a new process shown in steps S501 and S502 is inserted between the processes in steps S202 and S204 in FIG. The processing in step S207 shown in FIG. 2 is deleted.

  That is, in FIG. 5, after energization of the electric heaters 31 a, 31 b, and 31 c is selected by the operation selection unit 24 after the system stop command is transmitted (step S <b> 201), the system other than the system controller 33 is stopped. Then, power generation in the fuel cell stack 3 is stopped (step S501). Thereafter, it is determined whether or not the external power supply 26 is connected to the system (step S502). When the external power supply 26 is connected to the system, the processes of steps S204 and S205 are performed as in the first embodiment. After the execution, the system controller 33 starts energization of the electric heaters 31a, 31b, and 31c with the electric power supplied from the external power source 26.

  Thereafter, after heating for a predetermined heating time, the power of the external power source 26 is directly used, or the power of the external power source 26 is indirectly used via the battery 25 mounted on the vehicle to supply the fuel gas supply device 1 and the oxidant gas. By driving the apparatus 2 and supplying hydrogen and air to the fuel cell stack 3 in the same manner as in the first embodiment, the inside of the system is purged and the vaporized water is discharged out of the system.

  As described above, since the electric heaters 31a, 31b, and 31c are energized after the power generation of the fuel cell stack 3 is stopped, the electric heaters 31a, 31b, and 31c are humidified from the fuel cell stack 3 during energization. The anode off-gas and cathode off-gas that are present are not exhausted, and the system temperature decreases relatively quickly. For this reason, the temperature difference between the heated purge valve 27, the cathode pressure control valve 28 and the pressure sensor 30c and the peripheral components of the purge valve 27, the cathode pressure control valve 28 and the pressure sensor 30c is increased, and the purge valve 27, The adhesion of condensed water at the cathode pressure control valve 28 and the pressure sensor 30c can be further reduced.

  Further, when the system of the second embodiment is mounted on a fuel cell vehicle, the amount of fuel gas hydrogen consumption can be reduced, so that the cruising distance of the vehicle can be suppressed, and a battery, etc. The system can be made compact by reducing the capacity of the auxiliary power source.

  By adopting an external power source 26 other than the fuel cell stack 3 as a power source for the electric heaters 31a, 31b, 31c, even when the heating time is prolonged, the heating operation can be sufficiently performed regardless of the battery power. .

It is a figure which shows the structure of the fuel cell system which concerns on Example 1 of this invention. 3 is a flowchart illustrating an operation procedure of the fuel cell system according to the first embodiment. FIG. 3 is a diagram illustrating an operation state of the fuel cell system according to the first embodiment. It is a figure which shows the structure of the fuel cell system which concerns on Example 2 of this invention. 6 is a flowchart showing an operation procedure of the fuel cell system according to Example 2. FIG. 6 is a diagram showing an operation state of the fuel cell system according to Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel gas supply apparatus 2 ... Oxidant gas supply apparatus 3 ... Fuel cell stack 4 ... Anode pole 5 ... Cathode pole 6 ... Anode off-gas circulation apparatus 7 ... Mixer 8 ... Hydrogen heater 9 ... Refrigerant cooling apparatus 10 ... Humidifier 11 Anode gas supply pipe 12 Anode off gas circulation pipe 13 Anode off gas supply pipe 14 Cathode gas supply pipe 15 Cathode off gas supply pipe 19 Exhaust pipe 20 Refrigerant passage 21 Refrigerant pump 22 Three-way valve 23 Refrigerant bypass pipe 24 ... Operation selection means 25 ... Battery 26 ... External power supply 27 ... Purge valve 28 ... Cathode pressure control valve 29a, 29b, 29c, 29d, 29e, 29f, 29g, 29h, 29j ... Temperature sensor 30a, 30b, 30c ... Pressure sensor 31a, 31b, 31c ... Electric heater 32 ... Voltage detection means 33 ... System controller

Claims (8)

Fuel gas supply means for supplying fuel gas;
An oxidant gas supply means for supplying an oxidant gas;
A fuel cell stack for generating power by reacting the fuel gas supplied from the fuel gas supply means and the oxidant gas supplied from the oxidant gas supply means;
Fuel gas discharge means for discharging the fuel off-gas discharged from the fuel cell stack out of the system;
In the fuel cell system having an oxidant gas discharge means for discharging the oxidant off-gas discharged from the fuel cell stack to the outside of the system,
The fuel gas supply means, the fuel gas discharge means, and the oxidant gas discharge means are installed in at least one of the fuel gas supply means, the fuel gas discharge means, and the oxidant gas discharge means. A fuel cell system comprising heating means for heating at least one of the gas discharge means. 2. The fuel cell system according to claim 1, wherein the heating means is an electric heater that generates heat electrically. 3. The fuel cell system according to claim 1, wherein the heating unit is activated before power generation of the fuel cell stack is stopped when an operation stop command for the system is transmitted. 4. 3. The heating means is operated by a power source other than the fuel cell stack after power generation is stopped by the fuel cell stack when an operation stop command for the system is transmitted. The fuel cell system described. In the fuel cell system, when the operation of the system is stopped, whether to operate the heating unit is selected based on the operation condition of the system or the judgment of the operator of the system. The fuel cell system according to any one of claims 1, 2, 3, and 4. A temperature detection means for detecting at least one temperature of the fuel gas supply means heated by the heating means, the fuel gas discharge means and the oxidant gas discharge means, which is attached to the heating means;
The operation of the heating unit is stopped based on at least one of a temperature detected by the temperature detection unit or a predetermined time set in advance. The fuel cell system according to any one of the above. 7. The fuel cell system according to claim 1, wherein when the operation of the system is stopped, the inside of the system is purged with a gas. 8. Fuel cell system. The fuel cell system according to any one of claims 1, 2, 3, 5, 6, and 7, wherein the heating means is operated by being supplied with power from an external power source other than the fuel cell stack.

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