Fuel Cell Systems

Abstract

To provide a fuel cell system that is hard to make false detection of fire extinguish.SOLUTION: A disclosed fuel cell system 1 includes: a hydrogen generation unit that generates a hydrogen-containing gas from a raw material gas; a raw material gas supply unit that supplies the raw material gas to the hydrogen generation unit; an oxidant gas supply unit that supplies oxidant gas required for combustion; a fuel cell that generates electricity using the hydrogen-containing gas based on power generation instruction; a combustion unit that is configured to combust off fuel gas which is a hydrogen-containing gas not used in the fuel cell to heat the hydrogen generation unit; a measurement unit that measures flame current in the combustion unit; and a control unit that is configured so as to, when the flame current value measured by the measurement unit becomes lower than a first predetermined value, carry out protection control to control at least one of the amount of raw material gas supplied by the raw material gas supply unit, the amount of oxidant gas supplied by the oxidant gas supply unit, and the output of the fuel cell.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell system that is less likely to erroneously detect the combustion state of a combustion section as being in an extinguished state. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system that controls the power generation output to make it difficult to erroneously estimate the combustion state of the combustion section as an extinguished state. This fuel cell system includes a fire extinguishing estimation section that estimates whether the flame in the combustion section is in a burning state or an extinguished state, and a control device that controls the power generation output of the fuel cell, and when the fire extinguishing estimation section estimates the extinguishing state, the control device increases the output command value of the fuel cell above the output command value before the extinguishing state was estimated to be extinguished, thereby allowing the fuel cell to continue generating power, or stops the operation of the fuel cell system, and when the fuel cell system is subsequently operated, controls the output command value of the fuel cell to be increased above the output command value before the extinguishing state was estimated to be extinguished. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-137948 A Summary of the Invention [Problem to be solved by the invention]

[0004] The combustion section is supplied with a raw material gas and an off-fuel gas, i.e., hydrogen. When a gas in which raw material gas and hydrogen are mixed is burned, the flame current is smaller than when a gas in which hydrogen is not mixed with the raw material gas is burned. Therefore, based on this decrease in flame current, it is possible that the fire is erroneously detected as being in an extinguished state even when the fire is not in an extinguished state. If the fire is erroneously detected as being in an extinguished state and countermeasure control such as a re-ignition operation is repeatedly performed, the risk of failure of the igniter and the circuit increases. In addition, if the frequency of stopping power generation based on erroneous detection increases, problems such as the inability to secure power generation time and the deterioration of energy saving properties arise. The present disclosure provides a fuel cell system that performs protective control before determining that the fire is in an extinguished state. [Means for solving the problem]

[0005] A fuel cell system according to the present disclosure includes a hydrogen generating unit that generates a hydrogen-containing gas from a raw material gas, a raw material gas supply unit that supplies the raw material gas to the hydrogen generating unit, an oxidant gas supply unit that supplies an oxidant gas required for combustion, a fuel cell that generates power using the hydrogen-containing gas based on a power generation command, and a combustion unit that burns off-fuel gas that is the hydrogen-containing gas that has not been used in the fuel cell, the combustion unit heating the hydrogen generating unit, a measurement unit that measures a flame current in the combustion unit, and a value of the flame current measured by the measurement unit. is greater than the value of the flame current when the combustion portion is in an extinguished state. and a control device that implements protective control to control at least one of the amount of raw gas supplied by the raw gas supply unit, the amount of oxidant gas supplied by the oxidant gas supply unit, and the output by the fuel cell when the value of the flame current becomes lower than a first predetermined value, and further includes a timing unit that measures a protection implementation time, which is the time during which the protective control is implemented, and the control device controls at least one of the raw gas supply unit, the oxidant gas supply unit, and the fuel cell in accordance with the protection implementation time measured by the timing unit, and further, as the protective control, the control device sets the output by the fuel cell based on the power generation command at the time when the value of the flame current becomes lower than the first predetermined value as an output lower limit value, and controls the fuel cell so that the output of the fuel cell is equal to or higher than the output lower limit value. Effect of the Invention

[0006] The fuel cell system of the present disclosure performs protection control before estimating the extinguished state, thereby reducing the number of re-ignition operations that are performed when the extinguished state is estimated. This reduces the risk of failure of the igniter, circuits, etc. In addition, since the number of times power generation is stopped due to the estimation of the extinguished state is reduced, power generation can be continued stably, improving energy conservation. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of a fuel cell system according to a first embodiment. [Diagram 2] 1 is a flowchart for controlling the fuel cell system according to the first embodiment. [Diagram 3] Illustrative diagram of flame current value in a fuel cell system [Figure 4] FIG. 1 is a diagram illustrating the amount of raw material gas supplied in the fuel cell system according to the first embodiment. [Diagram 5] 11 is a flowchart for protection control of a fuel cell system according to a second embodiment. [Figure 6] FIG. 13 is an explanatory diagram of an oxidant gas supply amount in a fuel cell system according to a second embodiment. [Figure 7] 11 is a flowchart for protection control of a fuel cell system according to a third embodiment. [Figure 8] FIG. 13 is an explanatory diagram of an output value in a fuel cell system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (The knowledge and other information that formed the basis of this disclosure) At the time the inventors came up with the idea for this disclosure, when attempting to detect the presence or absence of a flame in the combustion section of a fuel cell system using a straightening flame rod, which is a flame detection device commonly used in combustion appliances, there were cases where the device would erroneously detect an extinguished state even when combustion was proceeding smoothly.

[0009] Specifically, in the case of a fuel cell system, the combustion section is supplied with raw material gas and off-fuel gas. Usually, when the power generation output of the fuel cell system is reduced, the settings of the raw material gas flow rate and the reformer temperature are also reduced according to the degree of reduction. However, due to the relationship of the heat capacity of the reformer, the temperature of the reformer does not immediately decrease. As a result, the temperature of the reformer relative to the raw material gas flow rate becomes higher than the appropriate value for a while, and the reforming efficiency during that time increases, and the ratio of hydrogen in the off-fuel gas increases. In that case, since hydrogen has a lower combustion temperature than, for example, methane contained in the raw material gas, a phenomenon may occur in which the value of the output current (flame current) of the flame rod decreases. In other words, the inventors discovered a problem that the fuel cell system may erroneously detect that the combustion section is in an extinguished state even though the combustion in the combustion section continues smoothly, and in order to solve the problem, the inventors have come to constitute the subject of the present disclosure.

[0010] Therefore, the present disclosure provides a fuel cell system that controls the amount of raw material gas supplied, the amount of oxidant gas supplied, or the output of the fuel cell when the value of the flame current falls below a first predetermined value.

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming more redundant than necessary and to facilitate understanding by those skilled in the art. It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiment 1) [1-1. Configuration] Fig. 1 shows the configuration of a fuel cell system 1 according to a first embodiment of the present disclosure, and the components of the fuel cell system 1 are housed in a housing 2. In Fig. 1, a hydrogen generation unit 3 is composed of a reformer 4 that reforms a raw material gas into a hydrogen-rich gas, a CO transformation unit 5 that transforms CO generated in the reformer 4, and a CO removal unit 6 that removes contained CO. A combustion unit 7 is provided to heat the hydrogen generation unit 3, including the reformer 4, to an appropriate temperature.

[0013] The raw material gas is supplied from outside the system and introduced into the hydrogen generation unit 3 at an appropriate flow rate by a raw material gas supply unit 8 and a raw material gas flow meter 9. Furthermore, air is supplied to the combustion unit 7 at an appropriate flow rate by a combustion air supply unit 10 and a combustion air flow meter 11 so that combustion in the combustion unit 7 is in an optimal state.

[0014] The fuel gas generated in the hydrogen generation unit 3 is supplied to an anode (not shown) of the fuel cell 12. On the other hand, an oxidant gas outside the housing 2 that is humidified to an appropriate dew point by a humidifier 14 as an oxidant gas containing oxygen is supplied to a cathode (not shown) of the fuel cell 12 by an oxidant gas supply unit 13.

[0015] The off fuel gas discharged from the anode of the fuel cell 12 is supplied to the combustion section 7 after heat is recovered and condensed water is separated by the condenser 15. The condensed water separated by the condenser 15 is collected in a condensed water tank 17. On the other hand, the off oxidant gas discharged from the cathode of the fuel cell 12 is discharged to the outside of the system after heat is recovered and condensed water is separated by the condenser 16. The condensed water separated by the condenser 16 is collected in the condensed water tank 17. In addition, the combustion exhaust gas discharged from the hydrogen generation section 3 is discharged to the outside of the housing 2 after heat is recovered and condensed water is separated by the condenser 18. The condensed water separated by the condenser 18 is collected in the condensed water tank 17.

[0016] The water recovered in the condensed water tank 17 is stored in a water tank 20 by a water supply pump 19. The water stored in the water tank 20 is supplied as cooling water to the fuel cell 12 by a cooling water circulation pump 21, and heat generated during power generation in the fuel cell 12 is recovered in the circulating water. The heat recovered in the circulating water is stored in hot water stored in an external hot water storage tank (not shown) by a heat exchanger 22. In addition, heat recovered from the above-mentioned condensers 15, 16, and 18 is also stored in hot water stored in an external hot water storage tank.

[0017] A control device 23 is also disposed inside the housing 2. The control device 23 converts the direct current generated by the fuel cell 12 into alternating current. The control device 23 is also connected to various actuators used in the fuel cell system 1 and controls these. A fire extinguishing estimation unit 24 is formed inside the control device 23.

[0018] Specifically, the fuel cell system 1 includes a hydrogen generation unit 3 that generates a hydrogen-containing gas from a raw material gas, a raw material gas supply unit 8 that supplies raw material gas to the hydrogen generation unit 3, an oxidant gas supply unit 13 that supplies an oxidant gas required for combustion, a fuel cell 12 that generates electricity using the hydrogen-containing gas based on a power generation command, a combustion unit 7 that is configured to combust off-fuel gas, which is the hydrogen-containing gas not used in the fuel cell 12, and heats the hydrogen generation unit 3, a measurement unit 25 that measures a flame current in the combustion unit 7, and a control device 23 that performs protective control to control at least one of the amount of raw material gas supplied by the raw material gas supply unit, the amount of oxidant gas supplied by the oxidant gas supply unit, and the output by the fuel cell when the value of the flame current measured by the measurement unit 25 becomes lower than a predetermined first specified value.

[0019] The fuel cell system 1 further includes a timer 26 that measures a protection implementation time, which is the time during which protective control is being performed. The control device 23 controls at least one of the raw material gas supply unit 8, the oxidant gas supply unit 13, and the fuel cell 12, in accordance with the protection implementation time measured by the timer 26.

[0020] Here, the oxidizing gas may be air. The measuring unit 25 may be a flame rod that detects the combustion state by utilizing a change in the value of the flame current, specifically, a change in electrical resistance due to the action of ions contained in the flame.

[0021] The control device 23 may be any device capable of controlling the system of the present disclosure. When expressing the subject matter of the invention, the device that controls the system of the present disclosure may be expressed as a control device, a control means, a control device, or a similar term. The control device 23 can be realized in various forms. For example, a processor may be used as the control device. If a processor is used as the control device 23, various processes can be executed by loading a program from a storage medium storing the program into the processor and executing the program by the processor. Therefore, the process contents can be changed by changing the program stored in the storage medium, so that the degree of freedom in changing the control contents can be increased. Examples of the processor include a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit). Examples of the storage medium include a hard disk, a flash memory, and an optical disk. In addition, a wired logic in which a program cannot be rewritten may be used as the control device 23. Using a wired logic as the control device 23 is effective in improving the processing speed. Examples of the wired logic include an ASIC (Application Specific Integrated Circuit). In addition, the control device 23 may be realized by combining a processor and a wired logic. If the control device 23 is realized by combining a processor and wired logic, it is possible to increase the degree of freedom of software design and improve the processing speed. The control device 23 and a circuit having a function different from that of the control device 23 may be configured with one semiconductor element. An example of a circuit having a function different from that of the control device 23 is an A / D·D / A conversion circuit. The control device 23 may be configured with one semiconductor element or multiple semiconductor elements. When configured with multiple semiconductor elements, each control described in the claims may be realized by different semiconductor elements. Furthermore, the control device 23 may be configured with a configuration including a semiconductor element and a passive component such as a resistor or a capacitor.

[0022] [1-2. Basic operation of fuel cell system] The operation and function of the fuel cell system 1 configured as above will be described below. When the fuel cell system is started up, a heater (not shown) attached to the hydrogen generation unit 3 raises the temperature of the hydrogen generation unit 3. When the hydrogen generation unit 3 rises to a temperature necessary for reforming the raw material gas, the raw material gas is supplied to the hydrogen generation unit 3, and hydrogen-rich fuel gas is generated. When fuel gas is generated by the hydrogen generation unit 3, water in the water tank 20 is supplied to the hydrogen generation unit 3 by driving the reforming water supply pump 27 as moisture necessary for the reforming reaction.

[0023] The fuel gas generated in the hydrogen generation unit 3 is supplied to the fuel cell 12, where it reacts with the oxidant gas supplied by the oxidant gas supply unit 13 and humidified by the humidifier 14 to generate electricity. The fuel gas used to generate electricity in the fuel cell 12 is discharged from the fuel cell 12 as off-fuel gas containing residual combustible components not used in the cell reaction, and is supplied to the combustion unit 7 after heat recovery and condensed water separation in the condenser 15. The off-fuel gas supplied to the combustion unit 7 is used as combustion gas for maintaining the temperature of the hydrogen generation unit 3. The combustion exhaust gas generated by combustion in the combustion unit 7 is discharged to the outside of the housing 2 after heat recovery and condensed water separation in the condenser 18 arranged midway.

[0024] [1-3. Protection and control] 2 is a flowchart of protection control of the fuel cell system 1 according to embodiment 1. First, in the fuel cell system 1, the flame current is measured by the measurement unit 25 to check the combustion state of the combustion unit 7 (step SA1). The control device 23 determines whether the measured flame current value is lower than a first predetermined value (step SA2).

[0025] The first predetermined value is determined in advance as a value between the flame current value during normal operation and the flame current value in the extinguished state. Specifically, the first predetermined value may take various values ​​depending on the size and structure of the fuel cell system 1, the type of the flame rod and the detection circuit, etc. For example, if the threshold value for the extinction estimation unit 24 to determine whether or not the fuel cell system is in the extinguished state is 0.3 μA and the value of the flame current during normal operation is 10 μA, the first predetermined value may be determined as 0.5 μA.

[0026] If the value of the flame current is lower than the first predetermined value (step SA2: YES), the control device 23 sets the amount of raw material gas supplied by the raw material gas supply unit 8 at the time when the value of the flame current becomes lower than the first predetermined value as a first lower limit value (step SA3). Then, the controller 23 controls the raw material gas supply unit 8 as protective control so that the amount of raw material gas supplied by the raw material gas supply unit 8 becomes equal to or greater than the first lower limit (step SA4). If the value of the flame current is not lower than the first predetermined value (step SA2: NO), the process returns to measuring the value of the flame current (step SA1).

[0027] Following step SA4, the measurement unit 25 measures the flame current to check the combustion state of the combustion unit 7 (step SA5). The control device 23 determines whether the measured flame current value is lower than a first predetermined value (step SA6). If the flame current value is not lower than the first predetermined value (step SA6: NO), the control device 23 determines whether the protection implementation time measured by the timing unit 26 after the start of protection control has exceeded a second predetermined value (step SA7). The second predetermined value is, for example, 3 seconds. If the protection implementation time has exceeded the second predetermined value (step SA5: YES), the control device 23 cancels the setting of the first lower limit value of the supply amount of raw material gas by the raw material gas supply unit 8 (step SA8) and returns to step SA1.

[0028] In step SA6, if the value of the flame current is lower than the first predetermined value (step SA6: YES), the process returns to step SA5. If the protection implementation time does not exceed the second predetermined value (step SA6: NO), the process returns to step SA5.

[0029] 2, the determination is made in step SA5 based on whether the flame current value is lower than a first predetermined value, but in order to prevent the protective control from being repeatedly turned on and off in a short period of time, the threshold in step SA5 may be set to a value greater than the first predetermined value, which is the threshold in step SA2. Specifically, when the protection implementation time exceeds the second predetermined value after implementing the protective control and when the flame current value becomes equal to or greater than a third predetermined value that is greater than the first predetermined value, the control device 23 may cancel the setting of the first lower limit value of the supply amount of raw material gas by the raw material gas supply unit 8.

[0030] FIG. 3 is an explanatory diagram for explaining the change in the value of the flame current in the fuel cell system 1. It is assumed that the value of the flame current drops for some reason during operation of the fuel cell system 1 and becomes lower than a first predetermined value. In this case, the fuel cell system 1 according to this embodiment performs a protective control operation before the extinction estimation unit 24 determines that the combustion unit 7 is in an extinguished state. Specifically, the time when the value of the flame current becomes the first predetermined value is set as T1, and protective control is performed until the protective control implementation time during which protective control is implemented reaches a second predetermined value T2. Specific protective control in the fuel cell system 1 according to this embodiment will be described with reference to FIG. 4.

[0031] 4 is a graph illustrating the change in the raw material gas supply amount during the protective control performed by the fuel cell system 1 according to embodiment 1. The protective control will be described below with reference to FIGS. Here, the dashed line in the graph indicates the change over time in the supply amount of the raw material gas supplied from the raw material gas supply unit 8. Moreover, the solid line in the graph indicates the change over time in the lower limit value of the supply amount of the raw material gas determined by the control device 23. When the amount of raw gas supply decreases and the value of the flame current measured by measuring unit 25 at time T1 shown in Fig. 3 becomes a first predetermined value, controller 23 controls raw gas supply unit 8 as protective control so that the amount of raw gas supplied by raw gas supply unit 8 becomes equal to or greater than a first lower limit value according to step SA4 in Fig. 2. At this time, controller 23 sets the amount of raw gas supplied by raw gas supply unit 8 at the time when the value of the flame current becomes lower than the first predetermined value as the first lower limit value according to step SA3 in Fig. 2 at time T1.

[0032] When the flame current value becomes equal to or greater than the first predetermined value and the protective control implementation time exceeds the second predetermined value T2, the control device 23 cancels the setting of the first lower limit value of the amount of raw material gas supplied by the raw material gas supply unit 8, in accordance with step SA8 of FIG. 2.

[0033] [1-4. Effects, etc.] As described above, in this embodiment, the fuel cell system 1 includes a hydrogen generation unit 3 that generates a hydrogen-containing gas from a raw material gas, a raw material gas supply unit 8 that supplies raw material gas to the hydrogen generation unit 3, an oxidant gas supply unit 13 that supplies an oxidant gas required for combustion, a fuel cell 12 that generates electricity using the hydrogen-containing gas based on a power generation command, a combustion unit 7 that is configured to combust off-fuel gas, which is the hydrogen-containing gas that was not used in the fuel cell 12, and heats the hydrogen generation unit 3, a measurement unit 25 that measures a flame current in the combustion unit 7, and a control device 23 that performs protective control to control at least one of the amount of raw material gas supplied by the raw material gas supply unit 8, the amount of oxidant gas supplied by the oxidant gas supply unit 13, and the output by the fuel cell 12 when the value of the flame current measured by the measurement unit 25 becomes lower than a first predetermined value.

[0034] As a result, the fuel cell system 1 performs protective control before estimating the extinguishing state, thereby reducing the number of times re-ignition operations are performed when the extinguishing state is estimated. This reduces the risk of failure of the igniter, circuits, etc. In addition, since the number of times power generation is stopped due to the estimation of the extinguishing state is reduced, power generation can be continued stably, and energy conservation is improved.

[0035] In this embodiment, the fuel cell system 1 further includes a timing unit 26 that measures a protection implementation time, which is the time during which protective control is carried out, and the control device 23 controls at least one of the raw material gas supply unit 8, the oxidant gas supply unit 13, and the fuel cell 12 in accordance with the protection implementation time measured by the timing unit 26.

[0036] This allows the fuel cell system 1 to limit the time for which protective control is performed, and therefore the time until re-ignition is performed when the fuel cell is truly in an extinguished state can be shortened, resulting in the effect that the fuel cell can be operated without performing unnecessary long periods of protective control.

[0037] In this embodiment, the fuel cell system 1 has a control device 23 that, as a protective control, sets the amount of raw gas supplied by the raw gas supply unit 8 at the time when the flame current value becomes lower than a first predetermined value as a first lower limit value, and controls the raw gas supply unit 8 so that the amount of raw gas supplied is equal to or greater than the first lower limit value.

[0038] As a result, the fuel cell system 1 can continue to supply the raw material gas, and by waiting for the temperature of the reforming section and other sections to reach an appropriate value when the fire is not in an extinguished state, the amount of ions increases and the flame current increases, so that the re-ignition operation can be avoided before the fire extinguishing estimation section 24 erroneously estimates that the fire is in an extinguished state. This reduces the risk of failure of the igniter and circuits, etc. Also, since the number of times power generation is stopped due to the estimation of the extinguished state is reduced, power generation can be continued stably, and energy saving is improved.

[0039] In this embodiment, the fuel cell system 1 cancels the setting of the first lower limit value of the amount of raw gas supplied by the raw gas supply unit 8 when the protection implementation time exceeds a second predetermined value after the control device 23 performs protection control and when the flame current value becomes equal to or greater than a first predetermined value.

[0040] This allows the fuel cell system 1 to maintain the lower limit of the supply amount of the raw material gas at a high value only during the necessary protective control, and prevents a wasteful supply of a large amount of raw material gas to the fuel cell 12. This provides the effect of achieving both stable and continuous power generation and energy conservation.

[0041] In this embodiment, the fuel cell system 1 cancels the setting of the first lower limit value of the amount of raw material gas supplied by the raw material gas supply unit 8 when the protection implementation time exceeds a second predetermined value after the control device 23 performs protection control and when the value of the flame current becomes equal to or greater than a third predetermined value that is greater than the first predetermined value.

[0042] This allows the fuel cell system 1 to maintain a high lower limit for the supply of raw material gas only during the necessary protective control, and prevents a large amount of raw material gas from being unnecessarily supplied to the fuel cell 12. It also prevents the protective control from being repeatedly turned on and off in a short period of time. This provides the effect of achieving both stable and continuous power generation and energy conservation.

[0043] (Embodiment 2) [2-1. Configuration] The physical configuration and basic operation of the fuel cell system 1 according to the second embodiment of the present disclosure are similar to those of the fuel cell system 1 according to the first embodiment described above, and therefore a description thereof will be omitted.

[0044] [2-2. Explanation of protection and control] 5 is a flowchart of the control of the fuel cell system 1 according to embodiment 2. First, in the fuel cell system 1, the flame current is measured by the measurement unit 25 to check the combustion state of the combustion unit 7 (step SB1). The control device 23 determines whether the measured flame current value is lower than a first predetermined value (step SB2).

[0045] The first predetermined value is determined in advance as a value between the flame current value during normal operation and the flame current value in the extinguished state. Specifically, the first predetermined value may take various values ​​depending on the size and structure of the fuel cell system 1, the type of the flame rod and the detection circuit, etc. For example, if the threshold value for the extinction estimation unit 24 to determine whether or not the fuel cell system is in the extinguished state is 0.3 μA and the value of the flame current during normal operation is 10 μA, the first predetermined value may be determined as 0.5 μA.

[0046] If the value of the flame current is lower than the first predetermined value (step SB2: YES), the control device 23 sets the amount of oxidizing gas supplied by the oxidizing gas supply unit 13 at the time when the value of the flame current becomes lower than the first predetermined value as a second lower limit value (step SB3). Then, the control device 23 controls the oxidizing gas supply unit 13 as protective control so that the supply amount of the oxidizing gas is equal to or greater than the second lower limit (step SB4). If the value of the flame current is not lower than the first predetermined value (step SB2: NO), the process returns to measuring the value of the flame current (step SB1).

[0047] Following step SB4, the measurement unit 25 measures the flame current to check the combustion state of the combustion unit 7 (step SB5). The control device 23 determines whether the measured flame current value is lower than a first predetermined value (step SB6). If the flame current value is not lower than the first predetermined value (step SB6: NO), the control device 23 determines whether the protection implementation time measured by the timer unit 26 after the start of protection control has exceeded a fourth predetermined value (step SB7). The third predetermined value is, for example, 3 seconds. If the protection implementation time has exceeded the fourth predetermined value (step SB5: YES), the control device 23 cancels the setting of the second lower limit value of the supply amount of oxidizing gas by the oxidizing gas supply unit 13 (step SB8) and returns to step SB1.

[0048] In step SB6, if the value of the flame current is lower than the first predetermined value (step SB6: YES), the process returns to step SB5. If the protection implementation time does not exceed the fourth predetermined value (step SB7: NO), the process returns to step SB5.

[0049] 5, the determination is made in step SB5 based on whether the flame current value is lower than a first predetermined value, but in order to prevent the protective control from being repeatedly turned on and off in a short period of time, the threshold in step SB5 may be set to a value greater than the first predetermined value, which is the threshold in step SB2. Specifically, when the protection implementation time exceeds a fourth predetermined value after implementing protective control and when the flame current value becomes equal to or greater than a fifth predetermined value that is greater than the first predetermined value, the control device 23 may cancel the setting of the second lower limit value of the amount of oxidant gas supplied by the oxidant gas supply unit 13.

[0050] 6 is a graph illustrating the change in the oxidant gas supply amount in the fuel cell system 1 according to embodiment 2. Protection control will be described with reference to FIGS. Here, the dashed line in the graph indicates the change over time in the supply amount of oxidant gas supplied from the oxidant gas supply unit 13. Also, the solid line in the graph indicates the change over time in the lower limit value of the supply amount of oxidant gas determined by the control device 23. When the amount of oxidant gas supplied decreases and the value of the flame current measured by measuring unit 25 at time T1 shown in Fig. 3 becomes a first predetermined value, according to step SB4 in Fig. 5, control unit 23 controls oxidant gas supply unit 13 as protective control so that the amount of oxidant gas supplied by oxidant gas supply unit 13 becomes equal to or greater than a second lower limit. At this time, according to step SB3 in Fig. 5 at time T1, control unit 23 sets the amount of oxidant gas supplied by oxidant gas supply unit 13 at the time when the value of the flame current becomes lower than the first predetermined value as the second lower limit.

[0051] When the flame current value becomes equal to or greater than the first predetermined value and the protective control implementation time exceeds the fourth predetermined value T4, the control device 23 cancels the setting of the second lower limit value of the amount of oxidant gas supplied by the oxidant gas supply unit 13 in accordance with step SB6 of Figure 5.

[0052] In this embodiment, the fuel cell system 1 has a control device 23 that, as a protective control, sets the amount of oxidant gas supplied by the oxidant gas supply unit 13 at the time when the flame current value becomes lower than a first predetermined value as a second lower limit value, and controls the oxidant gas supply unit 13 so that the amount of oxidant gas supplied is equal to or greater than the second lower limit value.

[0053] This increases the output of the fuel cell 12 in the fuel cell system 1, which results in a decrease in the hydrogen concentration of the off fuel gas and an increase in the flame current value. Therefore, before the extinction estimation unit 24 erroneously determines that the fuel cell is in an extinguished state, the flame current value can be increased to indicate that the fuel cell is in a normal combustion state, thereby reducing the number of re-ignition operations.

[0054] In this embodiment, the fuel cell system 1 cancels the setting of the second lower limit value of the amount of oxidant gas supplied by the oxidant gas supply unit 13 when the protection implementation time exceeds a fourth predetermined value T4 after the control device 23 performs protection control and when the value of the flame current becomes equal to or greater than the first predetermined value.

[0055] This allows the fuel cell system 1 to maintain the lower limit of the oxidant gas supply at a high value only during the necessary protective control, and prevents unnecessary supply of a large amount of oxidant gas to the fuel cell 12. This provides the advantage of achieving both stable and continuous power generation and energy conservation.

[0056] In this embodiment, the fuel cell system 1 cancels the setting of the second lower limit value of the amount of oxidant gas supplied by the oxidant gas supply unit 13 when the protection implementation time exceeds a fourth predetermined value after the control device 23 performs protection control and when the value of the flame current becomes equal to or greater than a fifth predetermined value that is greater than the first predetermined value.

[0057] This allows the fuel cell system 1 to maintain a high lower limit for the amount of oxidant gas supplied only during the necessary protective control, and prevents unnecessary supply of a large amount of oxidant gas to the fuel cell 12. It also prevents the protective control from being repeatedly turned on and off in a short period of time. This provides the advantage of achieving both stable and continuous power generation and energy conservation.

[0058] (Embodiment 3) [3-1. Configuration] The physical configuration and basic operation of the fuel cell system 1 according to the third embodiment of the present disclosure are similar to those of the fuel cell system 1 according to the first embodiment described above, and therefore a description thereof will be omitted.

[0059] [3-2. Explanation of protection and control] 7 is a flowchart of the control of the fuel cell system 1 according to embodiment 3. First, in the fuel cell system 1, the flame current is measured by the measurement unit 25 to check the combustion state of the combustion unit 7 (step SC1). The control device 23 determines whether the measured flame current value is lower than a first predetermined value (step SC2).

[0060] The first predetermined value is determined in advance as a value between the flame current value during normal operation and the flame current value in the extinguished state. Specifically, the first predetermined value may take various values ​​depending on the size and structure of the fuel cell system 1, the type of the flame rod and the detection circuit, etc. For example, if the threshold value for the extinction estimation unit 24 to determine whether or not the fuel cell system is in the extinguished state is 0.3 μA and the value of the flame current during normal operation is 10 μA, the first predetermined value may be determined as 0.5 μA.

[0061] If the value of the flame current is lower than the first predetermined value (step SC2: YES), the control device 23 sets the output by the fuel cell 12 based on the power generation command at the time when the value of the flame current becomes lower than the first predetermined value as the output lower limit value (step SC3).

[0062] As protective control, the controller 23 controls the fuel cell so that the output of the fuel cell is equal to or greater than the output lower limit (step SC4).

[0063] If the value of the flame current is not lower than the first predetermined value (step SC2: NO), the process returns to measuring the value of the flame current (step SC1).

[0064] Next, the flame current is measured by the measuring unit 25, and the controller 23 determines whether the measured flame current value is lower than a predetermined first predetermined value (step SC5). If the flame current value is lower than the first predetermined value (step SC5: YES), the controller 23 determines whether the protection control time measured by the timer 26 exceeds a predetermined sixth predetermined value (step SC6). The sixth predetermined value is, for example, 3 seconds. If the protection implementation time exceeds the sixth predetermined value (step SC6: YES), the controller 23 controls the fuel cell so that the output lower limit of the fuel cell is higher by a seventh predetermined value (step SC7). Then, the process returns to step SC5.

[0065] If the protection implementation time does not exceed the sixth predetermined value (step SC6: NO), the process returns to the determination of whether or not the flame current value is lower than the first predetermined value (step SC5).

[0066] If the value of the flame current is not lower than the first predetermined value (step SC5: NO), the controller 23 cancels the setting of the output lower limit value of the fuel cell 12 (step SC8), and returns to step SC1.

[0067] 7, the determination is made in step SC5 based on whether the flame current value is lower than a first predetermined value, but in order to prevent the protective control from being repeatedly turned on and off in a short period of time, the threshold in step SC5 may be set to a value greater than the first predetermined value, which is the threshold in step SC2. Specifically, the control device 23 may cancel the setting of the output lower limit value when the protection implementation time exceeds a sixth predetermined value after implementing the protective control and when the flame current value becomes equal to or greater than an eighth predetermined value that is greater than the first predetermined value.

[0068] 8 is a graph illustrating changes in output value in the fuel cell system 1 according to embodiment 3. Protection control will be described with reference to FIGS. Here, the dashed line in the graph indicates the change over time in the output of the fuel cell 12. Also, the solid line in the graph indicates the change over time in the lower limit value for the output of the fuel cell 12 in the power generation command determined by the control device 23.

[0069] If the output of the fuel cell 12 decreases and the value of the flame current measured by the measuring unit 25 at time T1 shown in Fig. 3 falls below the first predetermined value, the control device 23 controls the fuel cell as protective control so that the output of the fuel cell is equal to or greater than the output lower limit value according to step SC4 in Fig. 7. At this time, at time T1, according to step SC3 in Fig. 7, the control device 23 sets the output of the fuel cell 12 at the time when the value of the flame current fell below the first predetermined value as the output lower limit value.

[0070] Next, when the flame current value becomes equal to or exceeds the first predetermined value and the protection implementation time exceeds the sixth predetermined value T6, the control device 23 controls the fuel cell 12 to increase its output lower limit by a seventh predetermined value. This control is repeated until the flame current value measured by the measurement unit 25 becomes equal to or exceeds the first predetermined value. The control device 23 then cancels the setting of the output lower limit of the fuel cell 12.

[0071] In this embodiment, in the fuel cell system 1, the control device 23 sets, as a protective control, the output by the fuel cell 12 based on the power generation command at the time when the value of the flame current becomes lower than a first predetermined value as an output lower limit value, and controls the fuel cell 12 so that the output of the fuel cell 12 is equal to or greater than the output lower limit value.

[0072] This increases the output of the fuel cell 12 in the fuel cell system 1, which results in a decrease in the hydrogen concentration of the off fuel gas and an increase in the flame current value. Therefore, before the extinction estimation unit 24 erroneously determines that the fuel cell is in an extinguished state, the flame current value can be increased to indicate that the fuel cell is in a normal combustion state, thereby reducing the number of re-ignition operations.

[0073] In this embodiment, in the fuel cell system 1, when the protection implementation time exceeds a sixth predetermined value after the control device 23 performs protection control and when the value of the flame current is lower than the first predetermined value, the control device 23 controls the fuel cell 12 so that the output lower limit value of the fuel cell 12 is higher by a seventh predetermined value.

[0074] As a result, the fuel cell system 1 fixes the output value for the sixth predetermined value, which is the response time until the flame current value changes in response to the output change of the fuel cell, and therefore only needs to increase the output of the fuel cell by a necessary and sufficient amount, thereby achieving both stable power generation and energy conservation.

[0075] In this embodiment, the fuel cell system 1 cancels the setting of the output lower limit value when the protection implementation time exceeds a sixth predetermined value after the control device 23 performs protection control and when the value of the flame current becomes equal to or greater than a first predetermined value.

[0076] This allows the fuel cell system 1 to maintain the lower limit of the output at a high value only during the necessary protective control, eliminating the need for the fuel cell 12 to maintain an unnecessarily high output, thus achieving both stable and continuous power generation and energy conservation.

[0077] In this embodiment, the fuel cell system 1 cancels the setting of the output lower limit value when the protection implementation time exceeds a sixth predetermined value after the control device 23 performs protection control and when the value of the flame current becomes equal to or greater than an eighth predetermined value that is greater than the first predetermined value.

[0078] This allows the fuel cell system 1 to maintain the lower limit of the output at a high value only during the necessary protective control, and the fuel cell 12 does not need to maintain a high output unnecessarily. It also prevents the protective control from being repeatedly turned on and off in a short period of time. This provides the effect of achieving both stable and continuous power generation and energy conservation.

[0079] As described above, the first, second, and third embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in the first, second, and third embodiments to create new embodiments.

[0080] For example, the step units of the control operations shown in Figures 2, 5, and 7 are divided according to the main processing contents in order to facilitate understanding of the operation of each part of the fuel cell system 1, and the present invention is not limited by the manner in which the processing units are divided or the names thereof. The processing units may be further divided into more step units according to the processing contents. Furthermore, one step unit may be further divided to include more processing. Furthermore, the order of the steps may be appropriately changed within a range that does not impede the spirit of the present invention. [Industrial Applicability]

[0081] The present disclosure is generally applicable to fuel cell systems having a combustion section. [Explanation of symbols]

[0082] 1. Fuel cell system 2. Cabinet 3 Hydrogen generation section 4. Reformer 5 CO transformer 6 CO removal machine 7 Combustion section 8. Raw gas supply section 9. Raw gas flow meter 10 Combustion air supply section 11 Combustion air flow meter 12 Fuel Cell 13 Oxidant gas supply unit 14 Humidifier 15 Condenser 16 Condenser 17 Condensate tank 18 Condenser 19 Water supply pump 20 Water Tank 21 Cooling water circulation pump 22 Heat exchanger 23 Control device 24 Fire Extinguishing Estimation Department 25 Measurement section 26 Timing section 27 Reformed water supply pump

Claims

1. a hydrogen generating unit for generating a hydrogen-containing gas from a raw material gas; a raw material gas supply unit that supplies the raw material gas to the hydrogen generation unit; an oxidant gas supply unit for supplying an oxidant gas necessary for combustion; a fuel cell that generates electricity using the hydrogen-containing gas based on a power generation command; a combustion unit configured to combust the off-fuel gas, which is the hydrogen-containing gas not utilized in the fuel cell, and heat the hydrogen generation unit; A measurement unit that measures a flame current in the combustion unit; a control device that performs protection control to control at least one of the amount of the raw material gas supplied by the raw material gas supply unit, the amount of the oxidant gas supplied by the oxidant gas supply unit, and an output by the fuel cell when the value of the flame current measured by the measurement unit becomes lower than a first predetermined value that is larger than the value of the flame current when the combustion unit is in an extinguished state; and Equipped with A timer unit is further provided to measure a protection implementation time, which is a time during which the protection control is implemented, the control device controls at least one of the raw material gas supply unit, the oxidant gas supply unit, and the fuel cell in accordance with the protection implementation time measured by the timer, Furthermore, the control device performs the following protective control: an output by the fuel cell based on the power generation command at a time when the value of the flame current becomes lower than the first predetermined value is set as an output lower limit value, and the fuel cell is controlled so that the output of the fuel cell is equal to or higher than the output lower limit value. Fuel cell system.

2. The control device, as the protection control, setting a supply amount of the raw material gas by the raw material gas supply unit at a time point when the value of the flame current becomes lower than the first predetermined value as a first lower limit value; controlling the raw material gas supply unit so that the supply amount of the raw material gas is equal to or greater than the first lower limit value; The fuel cell system according to claim 1 .

3. when the protection implementation time exceeds a second predetermined value and the value of the flame current becomes equal to or greater than the first predetermined value after the protection control is performed, the control device cancels the setting of the first lower limit value of the supply amount of the raw material gas by the raw material gas supply unit. The fuel cell system according to claim 2 .

4. when the protection implementation time exceeds a second predetermined value and the value of the flame current becomes equal to or greater than a third predetermined value that is greater than the first predetermined value after the protection control is performed, the control device cancels the setting of the first lower limit value of the supply amount of the raw material gas by the raw material gas supply unit. The fuel cell system according to claim 2 .

5. The control device, as the protection control, an amount of the oxidant gas supplied by the oxidant gas supply unit at a time when the value of the flame current becomes lower than the first predetermined value is set as a second lower limit value; controlling the oxidant gas supply unit so that the supply amount of the oxidant gas is equal to or greater than the second lower limit value; The fuel cell system according to claim 2 .

6. when the protection implementation time exceeds a fourth predetermined value and the value of the flame current becomes equal to or greater than the first predetermined value after the protection control is performed, the control device cancels the setting of the second lower limit value of the amount of the oxidant gas supplied by the oxidant gas supply unit. The fuel cell system according to claim 5 .

7. when the protection implementation time exceeds a fourth predetermined value and the value of the flame current becomes equal to or greater than a fifth predetermined value that is greater than the first predetermined value after the protection control is performed, the control device cancels the setting of the second lower limit value of the amount of the oxidant gas supplied by the oxidant gas supply unit. The fuel cell system according to claim 5 .

8. The control device includes: after the protective control is performed, if the protection implementation time exceeds a sixth predetermined value and if the value of the flame current is lower than the first predetermined value, the fuel cell is controlled so that the output lower limit value of the fuel cell is higher by a seventh predetermined value. The fuel cell system according to claim 1 .

9. When the protection implementation time exceeds a sixth predetermined value and the value of the flame current becomes equal to or greater than the first predetermined value after the protection control is performed, the control device cancels the setting of the output lower limit value. The fuel cell system according to claim 8 .

10. When the protection implementation time exceeds a sixth predetermined value after the protection control is performed and when the value of the flame current becomes equal to or greater than an eighth predetermined value that is greater than the first predetermined value, the control device cancels the setting of the output lower limit value. The fuel cell system according to claim 8 .

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