JP2005038787A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of reducing the amount of hydrogen discharged to the outside without restricting activation.
A hydrogen bypass pipe 11 is branched from a hydrogen exhaust space 19 for discharging exhaust hydrogen from a fuel cell 1, and a reduction effect of a catalyst composition is exhibited in the path of the hydrogen bypass pipe 11 by supplying hydrogen. An oxidation catalyst 12 is provided. When the amount of exhaust hydrogen from the fuel cell 1 is large, the exhaust hydrogen is introduced into the hydrogen bypass pipe 11, processed by the oxidation catalyst 12, and discharged outside. The oxidation catalyst 12 is supplied with air from the oxidation air supply pipe 22 to activate the oxidation catalyst 12 as necessary.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system including a fuel cell that generates power by supplying hydrogen and air, and more particularly to a technique for reducing the release of untreated waste hydrogen.

  Fuel cell technology that enables clean exhaust and high energy efficiency is attracting attention as a countermeasure against environmental problems in recent years, particularly air pollution caused by automobile exhaust gas and global warming caused by carbon dioxide.

  A fuel cell system is an energy conversion system that supplies hydrogen and oxygen (air) as fuel to a hydrogen electrode and an air electrode of a fuel cell to cause an electrochemical reaction and convert chemical energy into electric energy. In such a fuel cell system, hydrogen and air supplied to the fuel cell are used for power generation in the process of flowing through the flow path in the fuel cell and then discharged to the outside. Further, even in a system that circulates and reuses hydrogen supplied to the fuel cell, it is discharged to the outside when the system is started or when hydrogen purge is performed at a predetermined timing.

  By the way, since hydrogen is flammable, it is not preferable to exhaust a large amount of exhaust gas containing high-concentration hydrogen to the outside. From this viewpoint, a technique for avoiding the release of untreated hydrogen has been proposed. (See, for example, Patent Document 1).

For example, in the technique described in Patent Document 1, all the exhausted hydrogen discharged from the fuel cell is treated with an oxidation catalyst. However, if warming up of the oxidation catalyst is not completed, hydrogen may be discharged untreated. In particular, when the fuel cell is repeatedly started and stopped, the hydrogen concentration tends to increase. If the start and stop are repeated in a short period of time, the system does not warm up and untreated hydrogen is discharged. Since the easy state continues, there is a high possibility that untreated hydrogen is discharged. Therefore, in the technique described in Patent Document 1, when the start of the fuel cell system is instructed, if the start and stop are repeatedly performed in a relatively short period based on the past start history, the start of the system is performed. By prohibiting it, a large amount of untreated hydrogen is avoided.
JP 2002-198075 A

  However, in the technique described in Patent Document 1, it is determined whether or not the system can be activated based on the past history at the time of activation, and the activation of the system is prohibited if activation and deactivation are repeatedly performed in a relatively short period of time. As a result, the discharge of untreated hydrogen is suppressed, and there is a problem in that the system may not be activated at the timing of activation. In addition, the control as described above is not applied after the system is started, and there is a possibility that a large amount of untreated hydrogen is discharged during operation.

  The present invention was devised to eliminate the drawbacks of the prior art as described above, and can reduce the amount of hydrogen discharged to the outside without restricting the start-up. Even when the amount of exhausted hydrogen discharged from the fuel cell exceeds a specified value, for example, when performing a hydrogen purge, etc., this is quickly treated with an oxidation catalyst to reduce the amount of discharged hydrogen to the outside. An object of the present invention is to provide a fuel cell system capable of performing the above-described operation.

  In order to achieve the above-described object, in the fuel cell system of the present invention, the hydrogen bypass pipe is branched from the hydrogen exhaust pipe that discharges the hydrogen discharged from the fuel cell to the outside, and the drainage from the fuel cell is performed by switching the control valve. The element can be introduced into the hydrogen bypass pipe. An oxidation catalyst that exhibits a reducing action of the catalyst composition by supplying hydrogen is provided in the path of the hydrogen bypass pipe, and an air pipe for supplying air to the oxidation catalyst is provided.

  In the fuel cell system of the present invention as described above, for example, when exhausted hydrogen exceeding a predetermined value is discharged from the fuel cell at the time of system startup or the like, this is led to a hydrogen bypass pipe and treated with an oxidation catalyst. Therefore, high-concentration exhaust hydrogen is not discharged outside as it is. In particular, by combining the treatment with the combustor and the treatment with the oxidation catalyst, the discharge of untreated hydrogen is greatly reduced. Moreover, the oxidation catalyst which processed the predetermined amount of exhaust hydrogen is always activated by the air (oxygen) supplied by air piping. Therefore, unlike the technique described in Patent Document 1, it is not necessary to wait until the temperature of the oxidation catalyst is increased and activated, the system can be started immediately, and there is no restriction on the startup. Furthermore, in the fuel cell system according to the present invention, when the amount of exhausted hydrogen suddenly increases due to, for example, hydrogen purging during operation after system startup, the same processing is performed, and the wastewater discharged to the outside. The amount of element is reduced.

  According to the fuel cell system of the present invention, the exhausted hydrogen is treated as needed by the oxidation catalyst that is appropriately activated by the air supply, so that the untreated hydrogen discharged to the outside without any restriction on the start-up The amount of can be reduced. Also, during operation after system startup, for example, when purging hydrogen, etc., even if the amount of exhausted hydrogen exceeds a specified value, it is promptly treated with an oxidation catalyst to reduce the amount of discharged hydrogen to the outside. It is possible.

  Hereinafter, specific embodiments of a fuel cell system to which the present invention is applied will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows the configuration of the main part of the fuel cell system of this embodiment. As shown in FIG. 1, the fuel cell system of this embodiment includes a fuel cell 1 that generates power by supplying hydrogen as a fuel and oxygen (air) as an oxidant. It is configured as a so-called direct hydrogen fuel cell system that directly supplies hydrogen.

  The fuel cell 1 has a structure in which power generation cells in which a fuel electrode to which hydrogen is supplied and an air electrode to which oxygen (air) is supplied are stacked with an electrolyte / electrode catalyst composite interposed therebetween are stacked in multiple stages. It converts chemical energy into electrical energy by a chemical reaction. At the fuel electrode of each power generation cell, hydrogen ions and electrons are dissociated when hydrogen is supplied, hydrogen ions pass through the electrolyte, electrons generate power through an external circuit, and move to the air electrode side. To do. In the air electrode, oxygen in the supplied air reacts with the hydrogen ions and electrons to generate water, which is discharged to the outside.

  As the electrolyte of the fuel cell 1, for example, a solid polymer electrolyte is used in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  A temperature sensor 2 is installed in the fuel cell 1 so that the controller of the fuel cell system grasps the operating state of the fuel cell 1 based on information from the temperature sensor 2 and performs various controls. It has become.

  In order to generate power in the fuel cell 1 as described above, it is necessary to supply hydrogen as a fuel and air as an oxidant to the hydrogen electrode and air electrode of each power generation cell constituting the fuel cell 1, respectively. The system is provided with a hydrogen supply system and an air supply system as mechanisms for this purpose.

  The hydrogen supply system includes a hydrogen tank 3 for storing hydrogen, a pressure control valve 4 for reducing the pressure of the hydrogen supplied from the hydrogen tank 3 to a desired pressure, and a hydrogen supply pipe 5 for introducing the pressure-adjusted hydrogen to the fuel cell 1. , An ejector 6 that circulates hydrogen using the fluid energy of hydrogen flowing in the hydrogen supply pipe 5, a hydrogen exhaust pipe 7 that discharges exhaust hydrogen discharged from the hydrogen electrode of the fuel cell 1 to the outside, and reuses the exhaust hydrogen It is provided with a hydrogen circulation pipe 8 for the purpose.

  The hydrogen supplied from the hydrogen tank 3 as a hydrogen supply source is depressurized to a predetermined pressure by the pressure control valve 4, passes through the hydrogen supply pipe 5, and is mixed with the exhausted hydrogen after passing through the fuel cell 1 by the ejector 6. To the hydrogen electrode of the fuel cell 1. In the fuel cell 1, not all of the supplied hydrogen is consumed, and surplus hydrogen that has not contributed to power generation (exhaust hydrogen discharged from the hydrogen electrode of the fuel cell 1) passes through the hydrogen circulation pipe 8 and is ejected. 6 is mixed with hydrogen newly supplied from the hydrogen tank 3 and supplied again to the hydrogen electrode of the fuel cell 1.

  A hydrogen purge valve 9 is provided on the outlet side of the fuel cell 1, that is, on the hydrogen exhaust pipe 7. In a fuel cell system that circulates and reuses hydrogen, by circulating hydrogen, impurities such as nitrogen and CO accumulate in the fuel cell 1 and in the hydrogen circulation pipe 8, and this impurity accumulates excessively. As the hydrogen partial pressure decreases, the efficiency of the fuel cell 1 decreases. In addition, after the system is stopped for a long time, the hydrogen partial pressure in the fuel cell 1 and the hydrogen circulation pipe 8 decreases with time. Therefore, in such a fuel cell system, when the impurity concentration becomes high or when the system is started, the hydrogen purge valve 9 is opened to purge the gas in the fuel cell 1 or the hydrogen circulation pipe 8.

  A hydrogen sensor 10 for detecting the amount of hydrogen discharged from the hydrogen electrode of the fuel cell 1 and flowing through the hydrogen exhaust pipe 7 is provided at a position downstream of the hydrogen purge valve 9 in the hydrogen exhaust pipe 7. As the hydrogen sensor 10, in addition to the one that directly detects the hydrogen flow rate, a pressure sensor that detects the exhaust hydrogen pressure or a means that measures the open time of the hydrogen purge valve 9 is used to determine the amount of hydrogen flowing through the hydrogen exhaust pipe 7. You may make it detect indirectly.

  Further, in the fuel cell system of the present embodiment, a hydrogen bypass pipe 11 is provided so as to branch from the hydrogen exhaust pipe 7, and an oxidation catalyst 12 is provided in the path. Here, the bypass pipe 11 is branched from the hydrogen exhaust pipe 7 via a three-way valve 13 which is a control valve for controlling the introduction of the exhaust hydrogen into the bypass pipe 11 and is joined again with the hydrogen exhaust pipe 7 on the downstream side. ing. Further, as the oxidation catalyst 12, one that exhibits a reducing action of the catalyst composition by supplying hydrogen, and the oxidation catalyst 12 is provided with a temperature sensor 14 for detecting its temperature, and an electric heater for warming up. (Illustration is omitted).

  As described above, when the impurity concentration in the fuel cell 1 or in the hydrogen circulation pipe 8 becomes high or when the system is started, the hydrogen purge valve 9 is opened to perform hydrogen purge. In the fuel cell system of the present embodiment, The hydrogen amount at that time is detected by the hydrogen sensor 10, and when the hydrogen amount is equal to or greater than the threshold value, the exhausted hydrogen purged by the three-way valve 13 is guided to the oxidation catalyst 12 of the hydrogen bypass pipe 11. As a result, the exhausted hydrogen is oxidized by reacting with oxygen in the oxidation catalyst 12, and then discharged to the outside.

  On the other hand, the air supply system includes a compressor 15 for sending air to the air electrode of the fuel cell 1, a filter 16, an air supply pipe 17, a humidifier 18 for humidifying supplied air, and an air electrode of the fuel cell 1. An air exhaust pipe 19 and an exhaust valve 20 for discharging exhaust gas are provided.

  The air pumped into the air supply pipe 17 by the compressor 15 that sucks and pumps air is purified by the filter 16 by trapping microdust, sulfur content, oil discharged from the compressor 15 and the like. The purified air is humidified by a humidifier 18 provided in the path of the air supply pipe 17 and supplied to the air electrode of the fuel cell 1. A temperature / humidity sensor 21 is provided at a downstream position of the humidifier 18, and the humidity contained in the air after passing the humidifier 18 is measured by the temperature / humidity sensor 21. The exhaust gas from the air electrode of the fuel cell 1 is discharged from the air exhaust pipe 19, and the pressure of the air system is controlled to a desired pressure by the exhaust valve 20 provided downstream of the fuel cell 1.

  Further, in the air supply pipe 17, an oxidation air supply pipe 22 led to the oxidation catalyst 12 provided in the path of the hydrogen bypass pipe 11 of the hydrogen supply system is branched from the upstream position of the gas humidifying means 18. . A valve 23 is provided in the middle of the oxidation air supply pipe 22, and the supply of air to the oxidation catalyst 12 is controlled by the valve 23.

  In the fuel cell system of the present embodiment configured as described above, the exhaust hydrogen processing operation is performed according to the following control flow. FIG. 2 shows a flowchart of the operation after system startup in the fuel cell system of the present embodiment.

  In the fuel cell system of the present embodiment, after starting the system, information is read from various sensors (step S1). First, it is determined whether or not the detection value Ce of the temperature sensor 14 that detects the temperature of the oxidation catalyst 12 provided in the path of the hydrogen bypass pipe 11 is equal to or lower than a predetermined threshold Cth (step S2). . Here, the threshold value Cth may be set to an optimum value according to the type of catalyst used for the oxidation catalyst 12, and is set to 20 ° C., for example.

  When the detected value Ce of the temperature sensor 14 is equal to or less than the threshold value Cth, it is recognized that there is a possibility that the oxidation catalyst 12 may be defective in catalytic activity, and the operation of the fuel cell 1 is restricted so that the oxidation catalyst 12 The attached electric heater is energized to promote warming up of the oxidation catalyst 12 (step S3). That is, as a stage before starting the supply of hydrogen from the hydrogen tank 3 to the fuel cell 1, the oxidation catalyst 12 is heated by an electric heater to create an atmosphere in which the oxidation-reduction action of the oxidation catalyst 12 is likely to proceed. . Then, after the warm-up of the oxidation catalyst 12 is completed, hydrogen supply from the hydrogen tank 3 is started (step S4). The energization state of the electric heater is controlled according to the detection value Ce of the temperature sensor 14, and the temperature is adjusted so that the temperature of the oxidation catalyst 12 is maintained at a predetermined temperature.

  On the other hand, if the detected value Ce of the temperature sensor 14 exceeds the threshold value Cth, it is recognized that the catalytic activity of the oxidation catalyst 12 is in a good state, and heating is not performed by energizing the electric heater, step S4. Then, the hydrogen supply from the hydrogen tank 3 is started.

  Next, after elapse of a predetermined time from the start of hydrogen supply, the hydrogen purge valve 9 is opened to perform hydrogen purge (step S5), and the detection value Vh by the hydrogen sensor 10 at this time is read (step S6). Then, it is determined whether or not the detection value Vh by the hydrogen sensor 10 exceeds a predetermined threshold value Vth (step S7). Note that the threshold value Vth here may be set based on the amount of hydrogen considered to be a problem when discharged unprocessed, and is set to 100 L / min, for example.

  Then, when the detection value Vh by the hydrogen sensor 10 exceeds the threshold value Vth, the three-way valve 13 is switched so that the hydrogen bypass pipe 11 side is opened, and introduction of exhaust hydrogen into the hydrogen bypass pipe 11 is started (step) S8). As a result, the exhausted hydrogen is oxidized by the oxidation catalyst 12 and then discharged to the outside.

  When the introduction of the exhaust hydrogen into the hydrogen bypass pipe 11 is started, the introduction time Th1 of the exhaust hydrogen is read (step S9), and it is determined whether or not the introduction time Th1 of the exhaust hydrogen into the hydrogen bypass pipe 11 exceeds a predetermined threshold value Tth1. Judgment is made (step S10). Here, the threshold value Tth1 is set according to the catalytic capacity and amount of the oxidation catalyst 12, and is set to 300 seconds, for example.

  Then, when the introduction time T of the exhaust hydrogen to the hydrogen bypass pipe 11 exceeds the threshold value Tth1, the three-way valve 13 is switched so that the hydrogen bypass pipe 11 side is closed to the hydrogen bypass pipe 11 (oxidation catalyst 12). The introduction of the exhausted hydrogen is stopped (step S11). Thereafter, the valve 23 provided in the oxidation air supply pipe 22 is opened, and air for reactivating the oxidation catalyst 12 is sent from the oxidation air supply pipe 22 (step S12).

  When the feeding of air for reactivating the oxidation catalyst 12 is started, the feeding time Th2 is read (step S13), and it is determined whether or not the air feeding time Th2 exceeds a predetermined threshold value Tth2 (step S14). . Here, the threshold value Tth2 is set according to the type and amount of the oxidation catalyst 12, and is set to 60 seconds, for example.

  Then, when the air feed time Th2 exceeds the threshold value Tth2, the valve 23 provided in the oxidation air supply pipe 22 is closed to stop the air feed from the oxidation air supply pipe 22 to the oxidation catalyst 12 (step). S15).

  Thereafter, it is determined whether or not the hydrogen purge is finished, that is, whether or not the hydrogen purge valve 9 is closed (step S16). When the hydrogen purge is finished, the process is finished as it is. On the other hand, when the hydrogen purge continues, the three-way valve 13 is switched again so that the hydrogen bypass pipe 11 side is opened, and the introduction of the exhaust hydrogen into the hydrogen bypass pipe 11 is started again (step S17). Returning to step S9, the subsequent processing is repeated.

  Although the operation contents executed after the system startup has been described above, the same operation is also executed when performing a hydrogen purge during system operation. However, during the hydrogen purge during the system operation, it is considered that the warming-up of the oxidation catalyst 12 provided in the path of the hydrogen bypass pipe 11 is completed, so the operations from step S1 to step S4 are omitted, and the step The operations after S5 are executed.

  As described above, according to the fuel cell system of the present embodiment, the hydrogen bypass pipe 11 is branched from the hydrogen exhaust pipe 7 that discharges the exhaust hydrogen from the fuel cell 1, Since the oxidation catalyst 12 exhibiting the reducing action of the catalyst composition is provided by supplying hydrogen, and the exhaust hydrogen introduced into the hydrogen bypass pipe 11 by switching the three-way valve 13 is oxidized by the oxidation catalyst 12 and discharged. Even when there is no air (oxygen) supply, the amount of hydrogen discharged to the outside can be reduced.

  Further, when hydrogen exceeding a predetermined standard is supplied to the oxidation catalyst 12 in the hydrogen bypass pipe 11, the oxygen in the oxidation catalyst 12 is consumed, and the exhaust hydrogen concentration cannot be reduced. In the fuel cell system of the embodiment, air is supplied from the oxidation air supply pipe 23 to the oxidation catalyst 12, and when the supply amount of exhaust hydrogen to the oxidation catalyst 12 reaches a reference value, the hydrogen bypass pipe 11 is supplied. Since the introduction of the exhaust hydrogen is cut off and air is supplied from the oxidation air supply pipe 12 to the oxidation catalyst 12 to hold the oxygen in the oxidation catalyst 12, the oxidation catalyst 12 is stabilized and oxidized. The catalytic action of the catalyst 12 can be maintained over a long period of time.

  Further, in the fuel cell system of the present embodiment, the amount of exhausted hydrogen is monitored by the hydrogen sensor 10 provided at the hydrogen electrode outlet of the combustion cell 1, and when the detected value of the hydrogen sensor 10 exceeds a predetermined threshold value, the hydrogen bypass is performed. Since hydrogen is introduced into the pipe 11 and supplied to the oxidation catalyst 12, the exhaust hydrogen concentration can be efficiently reduced as necessary.

  Furthermore, in the fuel cell system of the present embodiment, a heating means (electric heater) for heating the oxidation catalyst 12 in the hydrogen bypass pipe 11 is provided. If the temperature of the oxidation catalyst 12 is low immediately after the system is started, Since the oxidation catalyst 12 is heated by the heating means to create an atmosphere in which the redox action tends to proceed, the reaction can proceed efficiently. In addition, a temperature sensor 14 for detecting the temperature of the oxidation catalyst 12 is provided, and the heating means is controlled in accordance with the detected value of the temperature sensor 14 so as to maintain a predetermined temperature at which the catalytic activity of the oxidation catalyst 12 becomes good. Therefore, the oxidation-reduction reaction can proceed more efficiently. Further, since the power generation (hydrogen supply) of the fuel cell 1 is restricted until the oxidation catalyst 12 reaches a predetermined temperature, high concentration hydrogen discharge can be reliably prevented.

(Second Embodiment)
In the fuel cell system of this embodiment, as shown in FIG. 3, a combustor 24 is provided in the path of the hydrogen exhaust pipe 7, and exhaust hydrogen from the fuel cell 1 is mainly used in the combustor 24. To reduce the hydrogen concentration. Further, an oxidation catalyst 26 similar to the oxidation catalyst 12 provided in the hydrogen bypass pipe 11 is installed in series behind the heat exchanger 25 that absorbs the heat energy of the combustion reaction that occurs in the combustor 24, and the combustor Even if hydrogen remains in the exhaust gas after the combustion reaction at 24, the oxidation catalyst 26 enables the residual hydrogen to be oxidized.

  Further, in the fuel cell system according to the second embodiment, the combustor exhaust pipe 27 branches from the upstream side of the combustor 24 and is downstream of the combustor 24 (this combustor exhaust pipe 27 also corresponds to a hydrogen exhaust pipe). The hydrogen bypass pipe 11 is provided so as to merge with. Then, in a situation where combustion by the combustor 24 cannot be performed, such as when the system is started in a cold region, or when combustion takes a long time in the combustor 24, the fuel cell 1 is used as in the first embodiment. The exhausted hydrogen is treated by an oxidation catalyst 12 provided in the path of the hydrogen bypass pipe 11. Even when combustion by the combustor 24 is possible, when the amount of exhausted hydrogen from the fuel cell 1 is large, a part thereof is introduced into the hydrogen bypass pipe 11 and treated by the oxidation catalyst 12. Thus, the burden on the combustor 24 can be reduced.

  As described above, according to the fuel cell system of this embodiment, it is possible to treat a part of the amount of hydrogen supplied to the combustor 24 with the oxidation catalyst 12, and particularly when starting up in a cold region. Thus, even in a situation where the temperature of the combustor 24 is too low to function, it is possible to reduce the amount of hydrogen discharged to the outside by treating the exhaust hydrogen. In the present embodiment, since the oxidation catalyst 26 is installed in series with the combustor 24, even if residual hydrogen is contained in the exhaust gas after combustion by the combustor 24, This can be processed by the oxidation catalyst 26 to reduce the hydrogen concentration of the exhaust gas.

It is a figure which shows the structure of the fuel cell system of 1st Embodiment. It is a flowchart which shows the operation | movement flow at the time of starting of the fuel cell system of 1st Embodiment. It is a figure which shows the structure of the fuel cell system of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 7 Hydrogen exhaust pipe 9 Hydrogen purge valve 11 Hydrogen bypass piping 12 Oxidation catalyst 13 Three-way valve 14 Temperature sensor 22 Air supply pipe for oxidation 24 Combustor 25 Combustor exhaust pipe 28 Oxidation catalyst

Claims (8)

A fuel cell that generates electricity by supplying hydrogen and air;
A hydrogen exhaust pipe for discharging the exhausted hydrogen from the fuel cell to the outside;
A hydrogen bypass pipe branched from the hydrogen exhaust pipe and rejoined with the hydrogen exhaust pipe downstream;
A control valve for controlling the introduction of waste hydrogen into the hydrogen bypass pipe,
A fuel characterized in that, in the path of the hydrogen bypass pipe, an oxidation catalyst that exhibits a reducing action of the catalyst composition by supplying hydrogen is provided, and an air pipe for supplying air to the oxidation catalyst is provided. Battery system. A hydrogen amount detection means at the exhaust hydrogen outlet of the fuel cell;
2. The fuel cell system according to claim 1, wherein when the value detected by the hydrogen amount detection means exceeds a predetermined value, the control valve is switched to introduce exhaust hydrogen into the bypass pipe.   3. The introduction of exhaust hydrogen into the bypass pipe is cut off by switching the control valve when the amount of exhaust hydrogen introduced into the bypass pipe exceeds a predetermined amount. 4. Fuel cell system. Heating means for heating the oxidation catalyst in the bypass pipe;
The fuel cell system according to any one of claims 1 to 3, wherein the oxidation catalyst is heated by the heating means immediately after the system is started. Temperature detecting means for detecting the temperature of the oxidation catalyst in the bypass pipe;
The temperature of the oxidation catalyst is adjusted so as to keep the temperature of the oxidation catalyst at a predetermined temperature based on a detection value of the temperature detection unit when the oxidation catalyst is heated by the heating unit. Fuel cell system.   The fuel cell system according to claim 4 or 5, wherein when the temperature of the oxidation catalyst is equal to or lower than a predetermined temperature, the operation of the fuel cell is restricted. A combustor is provided in the path of the hydrogen exhaust pipe;
The fuel cell system according to any one of claims 1 to 6, wherein the bypass pipe is branched from an upstream side of the combustor and joined again with the hydrogen exhaust pipe downstream of the combustor.   The fuel cell system according to claim 7, wherein a second oxidation catalyst is provided downstream of the combustor.

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