JP2015185522A - fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of being stably operated without excessively increasing the temperature of a combustor even when removing adhering carbon.SOLUTION: A fuel cell system 1 comprises: a fuel cell 11; a reformer 12 which generates a reformed gas G2 supplied to the fuel cell 11 by reacting fuel G1 with water W on a catalyst; a reformed gas supply line L3 through which the reformed gas G2 formed by the reformer 12 flows to the fuel cell 11; a combustor 13 which burns an offgas G3 discharged from the fuel cell 11; a first exhaust line L5 through which the offgas G3 flows to the combustor 13; a second exhaust line L6 which discharges a flue gas G4 discharged from the combustor 13; and a bypass line L7 through which the reformed gas G2 formed by the reformer 12 or the offgas G3 is discharged without flowing through the combustor 13.

Description

  The present invention relates to a fuel cell system.

  There is a fuel cell (such as a solid oxide fuel cell (SOFC)) that generates electricity by electrochemically reacting a hydrogen-containing gas containing hydrogen and air. A fuel cell system including a reformer and a combustor in addition to such a fuel cell is known. In a fuel cell system, a reformer supplies a hydrogen-containing gas generated by reforming a hydrocarbon-based fuel such as city gas to the fuel cell, and a combustor treats anode off-gas exhausted from the fuel cell. To do. Such a fuel cell system is desired to be able to operate stably and for a long time.

  In Patent Document 1, when burning hydrogen contained in off-gas discharged from a fuel cell, the consumption of the catalyst used for off-gas hydrogen combustion is suppressed as much as possible by changing the catalyst used depending on the operation type, and A fuel cell system capable of efficient heat exchange is described. According to such an invention of Patent Document 1, the fuel cell system can be operated stably and in a long term.

JP 2014-17211 A

  By the way, when the fuel cell system is operated for a long period of time, carbon derived from the fuel gas may adhere to the cell stack of the fuel cell. Such carbon adhesion may reduce the power generation efficiency of the fuel cell, reduce the generation efficiency of the reformer, and clog the piping.

  Therefore, in order to operate the fuel cell system stably and for a long time, it is necessary to remove the attached carbon. In order to remove the adhering carbon, a fuel cell system that performs a refresh operation for supplying a vapor-rich fuel gas is conceivable.

  However, when the adhering carbon is removed by supplying the vapor-rich fuel gas, the off-gas discharged from the fuel cell contains a large amount of hydrogen and carbon monoxide. When trying to burn off gas containing many of these hydrogen and carbon monoxide, the temperature of the combustor rises excessively, so that the temperature of the entire fuel cell system rises excessively, and the fuel cell system stably. Could not be operated.

  An object of the present invention is to provide a fuel cell system that can be stably operated without excessively increasing the temperature of the combustor even when the adhering carbon is removed.

  The present invention relates to a fuel cell, a reformer that reacts fuel and water on a catalyst to generate a reformed gas supplied to the fuel cell, and a reformed gas generated by the reformer. A reformed gas supply line that circulates toward the fuel cell, a combustor that burns off-gas discharged from the fuel cell, a first exhaust line that circulates the off-gas toward the combustor, and the combustor A fuel cell system, comprising: a second exhaust line that discharges combustion exhaust gas discharged from a gas; and a bypass line that discharges the reformed gas generated by the reformer or the off-gas without passing through the combustor. About.

  In the present invention, it is preferable that the bypass line connects the reformer and the outside without passing through the fuel cell and the combustor, and the reformed gas generated by the reformer flows. .

  Further, according to the present invention, the bypass line communicates the reformed gas supply line and the second exhaust line without passing through the fuel cell and the combustor, and the reformed gas generated by the reformer. Is preferably distributed.

  Further, the present invention provides a flow rate adjusting unit that adjusts an inflow amount of the reformed gas generated by the reformer to the bypass line, and a reformed gas generated by the reformer by the flow rate adjusting unit. It is preferable to further include a control unit that controls the adjustment of the inflow amount.

  In the present invention, it is preferable that the bypass line connects the fuel cell and the outdoors, and the off-gas flows.

  In the present invention, it is preferable that the bypass line communicates the first exhaust line and the second exhaust line so that the off-gas flows.

  The present invention preferably further includes a flow rate adjusting unit that adjusts the inflow amount of the off gas to the bypass line, and a control unit that controls adjustment of the inflow amount of the off gas by the flow rate adjusting unit. .

  Further, the present invention further includes a temperature sensor that measures the temperature in the combustor, and the control unit detects that the temperature in the combustor is a predetermined temperature when the temperature sensor measures a predetermined temperature or more. It is preferable to control the flow rate adjusting unit so as to be as follows.

  According to the present invention, there is provided a fuel cell system that can be stably operated without excessively raising the temperature of a combustor even when adhering carbon is removed.

1 is a schematic diagram showing a fuel cell system 1 according to a first embodiment of the present invention. It is a flowchart which shows the flow of the refresh operation control of 1st Embodiment of this invention. It is the schematic which shows 1 A of fuel cell systems of 2nd Embodiment of this invention.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a fuel cell system 1 of the present embodiment. In FIG. 1, solid arrows indicate lines, and dotted arrows indicate signals from the control device 50.

  As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 11, a reformer 12, a combustor 13, flow rate adjusters 21 and 22, a pump 30, a temperature sensor 40, and a control device 50. Is provided.

  The fuel cell system 1 also includes a fuel gas supply line L1, a water supply line L2, a reformed gas supply line L3, an air supply line L4, a first exhaust line L5, a second exhaust line L6, and a bypass. A line L7. The “line” is a general term for a flow path, a path, a pipe line, and the like.

[Description of line]
In the fuel gas supply line L1, one end of the fuel gas supply line L1 is connected to a fuel gas supply unit (not shown) capable of supplying a fuel gas (fuel) G1 such as city gas, and the fuel gas supply line L1. Is connected to the reformer 12. The fuel gas G1 is supplied from the fuel gas supply unit to the reformer 12 through the fuel gas supply line L1.

  One end of the water supply line L2 is connected to a water reservoir (not shown), and the other end of the water supply line L2 is connected to the reformer 12. A pump 30 is connected in the middle of the water supply line L2. The pump 30 pressurizes the reforming water W from the water storage unit in order to supply the reforming water W to the reformer 12. The reforming water W in the water storage unit is supplied to the reformer 12 through the water supply line L2 from the water storage unit by driving the pump 30. The pump 30 adjusts the supply amount of the reforming water W by increasing or decreasing the driving force of the pump 30.

  In the reformed gas supply line L3, one end of the reformed gas supply line L3 is connected to the reformer 12, and the other end of the reformed gas supply line L3 is connected to the fuel cell 11. The reformed gas G2 containing hydrogen generated in the reformer 12 flows through the reformed gas supply line L3, is supplied to the fuel cell 11, and is used for power generation.

  In the air supply line L4, one end of the air supply line L4 is connected to a blower (not shown) and a filter (not shown) as an air supply part for supplying the air A1 containing oxygen to the fuel cell 11. Has been. The other end of the air supply line L4 is connected to the fuel cell 11. The air A1 passes through the filter from the blower, flows through the air supply line L4, and is supplied to the fuel cell 11.

  In the first exhaust line L5, one end of the first exhaust line L5 is connected to the fuel cell 11, and the other end of the first exhaust line L5 is connected to the combustor 13. A flow rate adjustment unit 21 is provided in the middle of the first exhaust line L5. The flow rate adjusting unit 21 functions to adjust the flow rate to the combustor 13 and may be configured as a valve that opens and closes by electrical control, for example. The off gas G3 flows through the first exhaust line L5 and is supplied to the combustor 13 when the flow rate adjusting unit 21 is open.

  In the second exhaust line L6, one end of the second exhaust line L6 is connected to the combustor 13, and the other end of the second exhaust line L6 is connected outdoors. The combustion exhaust gas G4 combusted by the combustor 13 flows through the second exhaust line L6 and is discharged outdoors.

  In the bypass line L7, one end of the bypass line L7 is connected to the fuel cell 11, and the other end of the bypass line L7 is connected outdoors. A flow rate adjusting unit 22 is provided in the middle of the bypass line L7. The flow rate adjusting unit 22 functions to adjust the flow rate to the bypass line L7, and may be configured as a valve that opens and closes by electrical control, for example. The off-gas G3 flows through the bypass line L7 and is discharged outside without passing through the combustor 13 when the flow rate adjusting unit 22 is open.

[Description of each device]
As the fuel cell 11, a high temperature solid oxide fuel cell (SOFC) is used. The fuel cell 11 has a fuel cell stack (not shown). The fuel cell stack is formed by alternately stacking a plurality of power generation cells (not shown) and separators (not shown).

  The power generation cell includes an anode (fuel electrode), a cathode (air electrode), and an electrolyte layer provided between the anode and the cathode. The anode is made of nickel or the like and is maintained in a reducing atmosphere with a reducing gas. The fuel cell 11 reacts the reformed gas G2 supplied to the anode from the reformer 12 via the reformed gas supply line L3 and the oxygen in the air A1 supplied to the cathode from the air supply line L4. Thus, power generation can be performed. The operating temperature, which is the temperature during power generation by the fuel cell 11, is a high temperature of about 700 ° C to 1000 ° C. The electricity generated by the fuel cell 11 is sent to a power conditioner (not shown) and converted into an AC voltage.

  The fuel cell 11 exhausts off-gas G3 including anode off-gas that is off-gas from the anode and cathode off-gas that is off-gas from the cathode.

  The reformer 12 generates a reformed gas G2 containing hydrogen on the catalyst based on the fuel gas G1 supplied from the fuel gas supply line L1 and the reformed water W supplied from the water supply line L2. At this time, the fuel gas G1 is heated to about 800 ° C. and supplied. The reformed gas G2 containing hydrogen generated by the reformer 12 is supplied to the fuel cell 11 via the reformed gas supply line L3.

During the refresh operation, the reformer 12 increases the amount of reforming water W supplied to the reformer 12, so that the ratio of steam to carbon (S / C ratio) is high. A quality gas G2 is generated.
Since the reformed gas G2 having a high S / C ratio contains a lot of steam, the carbon adhering to the piping of the fuel cell 11, the reformer 12, the first exhaust line L5, and the like is steamed. Removed by reacting with.
Here, the refresh operation is performed in a state where power generation by the fuel cell 11 is suspended. In addition, in the refresh operation, in order to remove carbon adhering to pipes such as the fuel cell 11, the reformer 12, and the first exhaust line L5, the carbon adhering is performed every predetermined period during which carbon adheres. It is performed when the power generation efficiency, which is considered to be the cause, is reduced.

  The combustor 13 combusts the off gas G3 exhausted from the fuel cell 11. The off-gas G3 combusted by the combustor 13 is discharged as a combustion exhaust gas G4 through a second exhaust line L6 connected to the downstream side of the combustor 13.

  The temperature sensor 40 is installed so that the temperature in the combustor 13 can be measured, and the temperature in the combustor 13 can be estimated. The temperature sensor 40 can measure a temperature range including an appropriate combustion temperature of the combustor 13 and an unsuitable combustion temperature. For example, a temperature from 0 ° C. to 1400 ° C. can be measured.

The control device 50 is intended to control the pump 30 and the flow rate adjusting units 21 and 22, and in addition to a control unit 51 that performs various arithmetic processes and a storage unit that stores various information, a keyboard, a touch panel, and the like. A general-purpose personal computer including an input unit and a display unit using a display.
As shown in FIG. 1, the control device 50 is connected to the pump 30, the flow rate adjusting units 21 and 22, and the temperature sensor 40 by wire or wirelessly, and can input and output various signals.
Specifically, the control device 50 inputs temperature information from the temperature sensor 40. The control unit 51 of the control device 50 outputs a command signal to the flow rate adjustment units 21 and 22 and the pump 30 based on the received temperature information.

[Control processing for refresh operation]
Next, with reference to FIG. 2, the control process of the refresh operation controlled by the control unit 51 in the fuel cell system 1 will be described. FIG. 2 is a flowchart showing the flow of control processing for refresh operation controlled by the control unit 51 in the fuel cell system 1.
The control unit 51 of the control device 50 constituting the fuel cell system 1 starts the process by receiving a refresh operation start signal of the fuel cell system 1. The control unit 51 continues the process until the refresh operation end signal is received. The control unit 51 receives a refresh operation end signal by an interrupt process (not shown) and ends the process.
The refresh operation start signal may be received every predetermined period. In addition, the refresh operation start signal may be accepted when it is determined that carbon is attached when the power generation efficiency decreases. Here, the predetermined period may be set to a period during which carbon is considered to adhere to the fuel cell system 1 or a period until power generation is suspended.

  In response to the reception of the refresh operation start signal, the control unit 51 outputs a command signal to the pump 30 so that the driving force of the pump 30 is increased as compared with the operation other than the refresh operation ( Step S1). In response to receiving the command signal, the pump 30 supplies the reforming water W with the driving force during the refresh operation. The reformer 12 supplies the reformed gas G2 having a high S / C ratio (that is, containing a large amount of steam and hydrogen) because the supply of the reforming water W is increased compared to the operation other than the refresh operation. Generate.

  Then, the control part 51 receives the input of the temperature information from the temperature sensor 40, and confirms whether the temperature of the combustor 13 is in a predetermined range (step S2). When the temperature is outside the predetermined range (NO), the control unit 51 advances the process to step S3 in order to adjust the flow rate adjustment units 21 and 22. When the temperature is within the predetermined range (YES), the control unit 51 returns the process to the beginning and continues the process.

  Here, the temperature within a predetermined range is set according to the operating temperature of each device in the fuel cell system 1 such as the fuel cell 11 and the reformer 12 and the type of the combustor 13. The temperature is within a normal operating range. For example, when a burner is used for the combustor 13, a temperature range of about 1000 ° C. is set, and when catalytic combustion is used for the combustor 13, a temperature range of several hundred degrees (300 to 700 ° C.) is set. .

As described above, the purpose of confirming whether the temperature of the combustor 13 is within a predetermined range is that, during the refresh operation, the reformed gas G2 having a high S / C ratio is generated, so that a large amount of hydrogen serving as a combustion source is contained. Therefore, it is to detect that the temperature of the combustor 13 becomes high.
Further, during the refresh operation, the reformed gas G2 having a high S / C ratio removes carbon adhering to piping such as the fuel cell 11, the reformer 12, and the first exhaust line L5 and is supplied to the combustor 13. That is, off-gas G3 containing a large amount of carbon as a combustion source is supplied. Therefore, it is detecting that the temperature of the combustor 13 becomes high.

  Subsequently, the control unit 51 outputs a flow rate adjustment signal to the flow rate adjustment units 21 and 22 (step S3). Specifically, the control unit 51 outputs a flow rate adjustment signal that decreases the flow rate of the off gas G3 (closes the valve) to the flow rate adjustment unit 21. The control unit 51 outputs a flow rate adjustment signal for increasing the flow rate of the off gas G3 (opening the valve) to the flow rate adjustment unit 22.

  Thereby, since the supply of the hydrogen and carbon used as a combustion source reduces in the combustor 13, the raised temperature falls.

According to the fuel cell system 1 of the present embodiment, for example, the following effects are produced.
The fuel cell system 1 of the present embodiment includes a fuel cell 11, a reformer 12 that reacts the fuel G1 and water W on the catalyst to generate the reformed gas G2 supplied to the fuel cell 11, and the reformer. A reformed gas supply line L3 through which the reformed gas G2 generated by the massifier 12 flows toward the fuel cell 11, a combustor 13 for combusting the offgas G3 discharged from the fuel cell 11, and an offgas G3 as the combustor The first exhaust line L5 that circulates toward the exhaust gas 13, the second exhaust line L6 that exhausts the combustion exhaust gas G4 exhausted from the combustor 13, and the reformed gas G2 or the offgas G3 generated by the reformer 12 are combusted. And a bypass line L7 that is discharged without passing through the vessel 13.

  In such a fuel cell system 1, the reformer 12 generates the reformed gas G2 containing a lot of steam, and the fuel cell 11, the reformer 12, the first exhaust line L5, etc. are generated by the generated reformed gas G2. Even when the carbon adhering to the pipe is removed, the reformed gas G2 containing many combustion sources such as hydrogen and the offgas G3 containing many combustion sources such as hydrogen and removed carbon do not pass through the combustor 13. Since it is discharged, the temperature of the combustor 13 can be stably operated without excessively increasing the temperature.

  Moreover, in the fuel cell system 1, the bypass line L7 connects the fuel cell 11 and the outdoors, and the off gas G3 circulates.

  In such a fuel cell system 1, the reformer 12 generates the reformed gas G2 containing a lot of steam, and the reformed gas G2, the reformer 12, the reformed gas supply line L3, etc. The carbon adhering to the fuel cell 11 is removed, and the off-gas G3 containing a large amount of combustion sources such as hydrogen and removed carbon is discharged without passing through the combustor 13, so that the carbon can be removed and burned. It can be stably operated without excessively raising the temperature of the vessel 13.

  The fuel cell system 1 further includes flow rate adjustment units 21 and 22 that adjust the inflow amount of the off gas G3, and a control unit 51 that controls adjustment of the inflow amount of the off gas G3 by the flow rate adjustment units 21 and 22. Prepare.

  Since the fuel cell system 1 includes the flow rate adjusting units 21 and 22 and the control unit 51 that controls the flow rate adjusting units 21 and 22, when the refresh operation is performed, the off-gas G3 is automatically supplied to the combustor 13. The amount of inflow can be adjusted so that it is discharged outside without flowing in. For this reason, the reformer 12 generates reformed gas G2 containing a lot of steam, and the carbon attached to the piping of the fuel cell 11, the reformer 12, the first exhaust line L5, and the like by the generated reformed gas G2. Even in the case of removal, the off-gas G3 containing a large amount of combustion sources such as hydrogen and removed carbon is discharged without going through the combustor 13, and can be stably operated without easily raising the temperature of the combustor 13. .

  The fuel cell system 1 further includes a temperature sensor 40 that measures the temperature in the combustor 13, and the control unit 51 detects the temperature in the combustor 13 when the temperature sensor 40 measures a predetermined temperature or higher. The flow rate adjusting units 21 and 22 are controlled so that the temperature becomes below a predetermined temperature.

  In such a fuel cell system 1, since the control unit 51 controls the flow rate adjustment based on the temperature sensor 40, the flow rate adjustment units 21 and 22 are automatically burned when the temperature of the combustor 13 begins to rise. The amount of inflow can be adjusted so that off gas is not flowed into the vessel 13 and is discharged to the outside. For this reason, the reformer 12 generates reformed gas G2 containing a lot of steam, and the carbon attached to the piping of the fuel cell 11, the reformer 12, the first exhaust line L5, and the like by the generated reformed gas G2. Also in the case of removal, the refresh operation is performed to burn off a combustion source such as hydrogen or removed carbon, but when the fuel cell system 1 rises to a temperature at which the fuel cell system 1 becomes unstable, the off-gas G3 including the combustion source is generated. It is discharged without going through the combustor 13 and can be operated stably without easily increasing the temperature of the combustor 13 easily.

[Second Embodiment]
Next, a fuel cell system 1A according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing a fuel cell system 1A according to the second embodiment of the present invention.

  Here, 1 A of fuel cell systems in 2nd Embodiment differ in the point provided with the bypass line L8 and the flow volume adjustment part 23 compared with the fuel cell system 1 in 1st Embodiment. Other configurations similar to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the bypass line L8, one end of the bypass line L8 is connected to the reformer 12, and the other end of the bypass line L8 is connected outdoors. A flow rate adjusting unit 23 is provided in the middle of the bypass line L8. The flow rate adjusting unit 23 functions to adjust the flow rate to the bypass line L8, and may be configured as a valve that opens and closes by electrical control, for example. The reformed gas G2 flows through the bypass line L8 and is discharged outside without passing through the combustor 13 when the flow rate adjusting unit 23 is open.

  Subsequently, the flow of control of the refresh operation in the present embodiment will be described with reference to FIG. 2 in the first embodiment. The control unit 51 receives input of temperature information from the temperature sensor 40 and checks whether or not the temperature of the combustor 13 is within a predetermined range (step S2). And the control part 51 outputs a flow volume adjustment signal with respect to the flow volume adjustment parts 21, 22, and 23 (step S3). Specifically, the control unit 51 outputs a flow rate adjustment signal for increasing the flow rates of the reformed gas G2 and the offgas G3 (opening the valves) to the flow rate adjusting units 22 and 23. The control unit 51 outputs a flow rate adjustment signal for decreasing the flow rate of the off gas G3 (closing the valve) to the flow rate adjustment unit 21.

According to the fuel cell system 1A of the second embodiment, for example, the following effects are exhibited.
In the fuel cell system 1A of the second embodiment, the bypass line L8 connects the reformer 12 and the outside without passing through the fuel cell 11 and the combustor 13, and the reformed gas generated by the reformer 12 G2 circulates.

  In such a fuel cell system 1A, the reformed gas G2 generated by the reformer 12 is discharged without passing through the fuel cell 11, so that the gas discharged outside without containing carbon has an influence on the environment. In the case where the reformed gas G2 containing a large amount of steam can be reduced and carbon adhering to the piping of the fuel cell 11, the reformer 12, the first exhaust line L5 and the like is removed by the generated reformed gas G2. However, since the reformed gas G2 containing many combustion sources such as hydrogen is discharged without passing through the combustor 13, the temperature of the combustor 13 can be stably operated without excessively rising.

  As mentioned above, although preferred embodiment was described, this invention is not limited to embodiment mentioned above, It can implement with a various form.

  For example, in the above-described embodiment, with respect to the bypass line L7, one end of the bypass line L7 is connected to the fuel cell 11, and the other end of the bypass line L7 is connected outdoors. One end of the bypass line L7 may be connected to the first exhaust line L5. Furthermore, the other end of the bypass line L7 may be connected to the second exhaust line L6.

  Moreover, in the above-mentioned embodiment, regarding the bypass line L8, one end of the bypass line L8 is connected to the reformer 12, and the other end of the bypass line L8 is connected outdoors. Instead, one end of the bypass line L8 may be connected to the reformed gas supply line L3. The other end of the bypass line L8 may be connected to the second exhaust line L6.

  Further, in the above-described embodiment, the combustion exhaust gas G4 flows through the second exhaust line L6 and is discharged outdoors, and the off-gas G3 flows through the bypass line L7 and is discharged outside without passing through the combustor 13. However, it is preferable that the combustion exhaust gas G4 and the off-gas G3 are discharged to the outdoors after being diluted with air to the combustion limit or less. For example, the combustion exhaust gas G4 may be diluted below the combustion limit and discharged to the outdoors by communicating the air supply line L4 and the second exhaust line L6 and diluting the combustion exhaust gas G4 with the air A1. Further, for example, the off gas G3 may be diluted to the combustion limit or less and discharged to the outdoors by communicating the air supply line L4 and the bypass line L7 and diluting the off gas G3 with the air A1.

DESCRIPTION OF SYMBOLS 1,1A Fuel cell system 11 Fuel cell 12 Reformer 13 Combustor 21, 22, 23 Flow rate adjustment part 40 Temperature sensor 51 Control part L5 1st exhaust line L6 2nd exhaust line L7, L8 Bypass line G1 Fuel gas G2 reform Quality gas G3 Off gas W Reformed water (water)

Claims (8)

A fuel cell;
A reformer that reacts fuel and water on a catalyst to generate a reformed gas to be supplied to the fuel cell;
A reformed gas supply line through which the reformed gas generated in the reformer flows toward the fuel cell;
A combustor that burns off-gas discharged from the fuel cell;
A first exhaust line through which the off-gas flows toward the combustor;
A second exhaust line for discharging the combustion exhaust gas discharged from the combustor;
A bypass line through which the reformed gas generated in the reformer or the off-gas is discharged without passing through the combustor;
A fuel cell system comprising: The bypass line connects the reformer and the outside without passing through the fuel cell and the combustor, and the reformed gas generated in the reformer flows.
The fuel cell system according to claim 1. The bypass line communicates the reformed gas supply line and the second exhaust line without passing through the fuel cell and the combustor, and the reformed gas generated by the reformer flows.
The fuel cell system according to claim 1. A flow rate adjusting unit for adjusting the amount of reformed gas generated by the reformer to the bypass line;
A control unit that controls adjustment of an inflow amount of the reformed gas generated in the reformer by the flow rate adjusting unit;
The fuel cell system according to claim 2, further comprising: The bypass line connects the fuel cell and the outdoors, and the off-gas flows.
The fuel cell system according to claim 1. The bypass line communicates the first exhaust line and the second exhaust line, and the off gas circulates.
The fuel cell system according to claim 1. A flow rate adjusting unit for adjusting the amount of the off gas flowing into the bypass line;
A control unit for controlling the adjustment of the inflow amount of the off gas by the flow rate adjustment unit;
The fuel cell system according to claim 5, further comprising: A temperature sensor for measuring the temperature in the combustor;
The control unit controls the flow rate adjusting unit so that the temperature in the combustor is equal to or lower than a predetermined temperature when the temperature sensor measures a predetermined temperature or higher.
The fuel cell system according to claim 4 or 7.

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