JP2020027714A - Fuel cell system - Google Patents

Abstract

To prevent generation of coking by appropriately monitoring high temperature abnormality of a reforming system.SOLUTION: A fuel cell system comprises: a fuel cell for generating power on the basis of fuel gas and oxidant gas; a reformer for reforming raw material gas to fuel gas using water vapor to supply the fuel gas to the fuel cell; a raw material gas supply device for supplying the raw material gas to the reformer; a vaporizer for supplying water vapor obtained by vaporizing reforming water to the reformer; a reforming water supply device for supplying the reforming water to the vaporizer; a control device that controls the raw material gas supply device by setting a target gas flow rate depending on output required of the fuel cell and controls the reforming water supply device by setting a target reforming water amount; and a temperature detector for detecting a temperature of a reforming system including the vaporizer and the reformer. The control device executes monitoring processing of monitoring presence/absence of high temperature abnormality in which a temperature detected by the temperature detector exceeds a predetermined threshold in a state in which power generation output of the fuel cell is stable. In the case that the power generation output of the fuel cell is low, the predetermined threshold is set to be a higher temperature than that in the case that the power generation output is high.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel cell system.

  Conventionally, as a fuel cell system of this type, a fuel cell that generates electric power based on a fuel gas and an oxidizing gas, a vaporizer (evaporator) that vaporizes supplied reformed water, and a vaporizer that is vaporized by the vaporizer A reformer for reforming a raw material gas using steam to generate a fuel gas (reformed gas), and a reforming system including a vaporizer and a reformer by burning off-gas not used in the fuel cell And a combustion section that heats the fuel cell (for example, see Patent Document 1). The control unit of the fuel cell system controls the supply amount of the reforming water based on the steam carbon ratio, which is the ratio between the amount of steam supplied to the reformer and the amount of carbon in the raw material gas. Since the reforming catalyst is liable to cause coking when exposed to high temperatures, the higher the temperature of the reforming system, the larger the target value of the steam carbon ratio is changed to a larger value (ratio). Thus, the temperature rise of the reforming catalyst is suppressed to prevent coking.

JP 2013-187118 A

  As described above, coking is likely to occur in a high temperature state. Therefore, it is conceivable to detect the temperature of the reforming system to determine whether there is a high temperature abnormality that may cause coking. However, the temperature of the reforming system changes depending on the supply amount of reforming water, the amount of off-gas, and the like in accordance with the output of the fuel cell, and the temperature change has a delay with respect to the output change of the fuel cell. For this reason, in a method of determining an abnormality by simply comparing the temperature of the reforming system with a uniform threshold, a high-temperature abnormality may be erroneously determined.

  An object of the present invention is to appropriately monitor a high-temperature abnormality of a reforming system to prevent occurrence of coking.

  The present invention employs the following means in order to achieve the above main object.

  A fuel cell system according to the present invention includes a fuel cell that generates electric power based on a fuel gas and an oxidizing gas, a reformer that reforms a raw material gas into a fuel gas using water vapor and supplies the fuel gas to the fuel cell, A raw material gas supply device for supplying gas to the reformer, a vaporizer for supplying vaporized vaporized reformed water to the reformer, and a reformed water supply device for supplying reformed water to the vaporizer; Setting a target gas flow rate such that the fuel cell generates electric power in accordance with the output required of the fuel cell to control the raw material gas supply device, and setting a target reforming water amount according to the target gas flow rate. A control device that controls the reforming water supply device, and a temperature detector that detects a temperature of a reforming system including the vaporizer and the reformer. When the power generation output is stable, the temperature is detected by the temperature detector. Executing a monitoring process for monitoring the presence or absence of a high temperature abnormality in which the temperature of the reforming system exceeds a predetermined threshold, wherein the predetermined threshold is higher when the power output of the fuel cell is smaller than when it is higher. The gist is that the temperature is set to be the temperature.

  In the fuel cell system of the present invention, a monitoring process for monitoring whether or not there is a high temperature abnormality in which the temperature of the reforming system detected by the temperature detector exceeds a predetermined threshold value is performed while the power output of the fuel cell is stable. Further, the predetermined threshold value used for determining the high temperature abnormality is set so that the temperature becomes higher when the power generation output of the fuel cell is small than when it is large. For this reason, regardless of the magnitude of the power generation output of the fuel cell, it is possible to monitor the presence or absence of a high temperature abnormality using a predetermined threshold value set according to the magnitude of the power generation output. And appropriate measures can be taken. In addition, since the monitoring process is executed in a state where the power output of the fuel cell is stable, the influence of the delay in the temperature change of the reforming system with respect to the fluctuation of the power output can be eliminated, and the erroneous determination of the high temperature abnormality can be prevented. . Therefore, the occurrence of coking can be prevented by appropriately monitoring the high temperature abnormality of the reforming system.

  In the fuel cell system according to the aspect of the invention, the control device may be configured such that when a state in which the fluctuation of the power generation output of the fuel cell is within a predetermined width continues for a predetermined time or more, the power generation output of the fuel cell is stable. It may be assumed that there is. This makes it possible to determine the state in which the power generation output is stable by simple processing, and to appropriately execute the monitoring processing.

  In the fuel cell system of the present invention, the control device sets the target reformed water amount based on the steam gas ratio, which is a ratio of a raw material gas to steam, and the target gas flow rate. When the temperature of the reforming system detected by the temperature detector is high, the ratio may be changed so as to be larger than when the temperature is low. Such a change in the steam carbon ratio suppresses a further increase in temperature when the temperature of the reforming system is high, so that the occurrence of coking can be more appropriately prevented in conjunction with the execution of the monitoring process.

  In the fuel cell system according to the present invention, the control device may stop the system when a high temperature abnormality of the reforming system is detected by performing the monitoring process. In this way, when a high temperature abnormality of the reforming system is detected, the occurrence of coking can be more reliably prevented, and the reforming system can be prevented from failing.

FIG. 1 is a configuration diagram illustrating a schematic configuration of a fuel cell system 10 according to an embodiment. It is explanatory drawing which shows an example of the relationship between reformer temperature T and S / C. 13 is a flowchart illustrating an example of a threshold setting processing routine. It is a flowchart which shows an example of an abnormality monitoring processing routine. FIG. 4 is an explanatory diagram illustrating an example of a threshold Tref setting map.

  An embodiment for carrying out the present invention will be described.

  FIG. 1 is a configuration diagram schematically showing the configuration of the fuel cell system 10 of the present embodiment. As shown in FIG. 1, the fuel cell system 10 according to the present embodiment includes a power generation unit 20 having a fuel cell stack 36 that receives a supply of a fuel gas containing hydrogen and an oxidant gas (air) containing oxygen to generate power. A hot water supply unit 100 having a hot water storage tank 101 for recovering and supplying hot water generated by the power generation of the power generation unit 20, and a control device 80 for controlling the entire system.

  The power generation unit 20 includes a fuel cell module 30 including a vaporizer 32, a reformer 33, and a fuel cell stack 36, a source gas supply device 40 that supplies a source gas (eg, natural gas or LP gas) to the vaporizer 32, An air supply device 50 for supplying air to the fuel cell stack 36, a reformed water supply device 55 for supplying reformed water to the vaporizer 32, and a waste heat recovery device 60 for recovering waste heat generated in the fuel cell module 30 And. These are housed in the housing 22. The casing 22 is provided with an intake port 22a and an exhaust port 22b, and a ventilation fan 24 for taking in outside air and ventilating the inside of the casing 22 is provided near the intake port 22a.

  The vaporizer 32 evaporates the reforming water from the reforming supply device 55 to generate steam and preheats the source gas from the source gas supply device 40. The reformer 33 is configured by supporting a reforming catalyst (for example, a Ru or Ni-based catalyst) on a carrier such as a ceramic, and steam reforming a mixed gas of the raw material gas and the steam supplied from the vaporizer 32. It is reformed into fuel gas (reformed gas) by the reaction. Near the inlet of the reformer 33, a temperature sensor 91 for detecting the temperature at the inlet of the reformer 33 (reformer temperature T) is provided. The temperature sensor 91 only needs to detect the temperature of the reforming system including the vaporizer 32 and the reformer 33, and may be provided near the outlet of the vaporizer 32. It may be provided between the reformer 33.

  The vaporizer 32, the reformer 33, and the fuel cell stack 36 are housed in a box-shaped module case 31 formed of a heat insulating material. In the module case 31, a combustion section 34 for supplying heat necessary for starting the fuel cell stack 36, generating steam in the vaporizer 32, and performing a steam reforming reaction in the reformer 33 is provided. A fuel off-gas (anode off-gas) and an oxidant off-gas (cathode off-gas) that have passed through the fuel cell stack 36 are supplied to the combustion unit 34, and the mixed gas is ignited by an ignition heater 35 and burned, thereby burning the fuel cell. The stack 36, the vaporizer 32, and the reformer 33 are heated. The combustion section 34 is provided with a temperature sensor 92 for detecting the temperature of the combustion section 34. The combustion exhaust gas generated by the combustion of the fuel off-gas and the oxidant off-gas is supplied to the heat exchanger 62 via the combustion catalyst 37. The combustion catalyst 37 is an oxidation catalyst that reburns the fuel gas remaining in the combustion section 34 with the catalyst.

  The exhaust heat recovery device 60 includes a circulation pipe 61 that connects a heat exchanger 62 to which combustion exhaust gas is supplied from the fuel cell module 30 and a hot water storage tank 101 that stores hot water to form a circulation path of the hot water. The circulation pipe 61 is provided with a circulation pump 63. By driving the circulation pump 63, the hot water is heated by heat exchange between the hot water and the combustion exhaust gas in the heat exchanger 62, and the hot water is heated. Water is stored in hot water storage tank 101. The heat exchanger 62 is connected to the reforming water tank 57 via a condensed water supply pipe 66 and to the outside air via an exhaust gas discharge pipe 67. The combustion exhaust gas supplied to the heat exchanger 62 is condensed with a steam component by heat exchange with the hot water, and the condensed water (condensed water) is purified by a water purifier (not shown) and collected in the reformed water tank 57. Is done. Further, the remaining exhaust gas (gas component) is exhausted to the outside air via an exhaust gas exhaust pipe 67.

  The source gas supply device 40 has a source gas supply pipe 41 that connects the gas supply source 1 and the vaporizer 32. The source gas supply pipe 41 is provided with source gas supply valves (electromagnetic valves) 42 and 43, an orifice 44, a source gas pump 45, and a desulfurizer 46 in this order from the gas supply source 1 side. By driving the raw material gas pump 45 with the valve 43 opened, the raw material gas from the gas supply source 1 passes through the desulfurizer 46 and is supplied to the vaporizer 32. The raw material gas supplied to the vaporizer 32 is supplied to the reformer 33 via the vaporizer 32 and is reformed into a fuel gas. The source gas supply valves 42 and 43 are double valves connected in series. The desulfurizer 46 is for removing sulfur contained in the raw material gas. For example, a normal temperature desulfurization method in which a sulfur compound is adsorbed by an adsorbent such as zeolite and removed can be employed. In addition, the desulfurization method is not limited to the normal temperature desulfurization method, and various methods can be adopted. Further, a pressure sensor 47 for detecting the pressure of the source gas in the source gas supply pipe 41 is provided between the source gas supply valve 43 and the orifice 44 of the source gas supply pipe 41, and the orifice 44 and the source gas pump 45 are provided. A flow sensor 48 for detecting a flow rate (gas flow rate Fg) of the raw material gas flowing through the raw material gas supply pipe 41 per unit time is provided.

  The air supply device 50 has an air supply pipe 51 that connects the filter 52 communicating with the outside air and the fuel cell stack 36. The air supply pipe 51 is provided with an air blower 53. By driving the air blower 53, the air sucked through the filter 52 is supplied to the fuel cell stack 36. The air supply pipe 51 is provided, downstream of the air blower 53, with a flow rate sensor 54 for detecting a flow rate of air flowing through the air supply pipe 51 per unit time (air flow rate Fa).

  The reformed water supply device 55 has a reformed water supply pipe 56 that connects the reformed water tank 57 that stores the reformed water and the vaporizer 32. The reforming water supply pipe 56 is provided with a reforming water pump 58. By driving the reforming pump 58, the reforming water in the reforming water tank 57 is supplied to the vaporizer 32. The reforming water supplied to the vaporizer 32 is converted into steam in the vaporizer 32 and used for a steam reforming reaction in the reformer 33. The reformed water tank 57 is provided with a water purifier (not shown) for purifying the stored reformed water.

  The fuel cell stack 36 includes a solid oxide fuel cell including a solid electrolyte made of an oxygen ion conductor, an anode provided on one surface of the solid electrolyte, and a cathode provided on the other surface of the solid electrolyte. They are stacked. The fuel cell stack 36 generates power by an electrochemical reaction between hydrogen in the fuel gas supplied to the anode and oxygen in the air supplied to the cathode. In the vicinity of the fuel cell stack 36, a temperature sensor 93 for detecting the temperature of the fuel cell stack 36 is provided. The power line 3 from the commercial power supply 2 to the load 4 is connected to the output terminal of the fuel cell stack 36 via the power conditioner 70.

  The power conditioner 70 is capable of connecting a DC / DC converter that boosts a DC voltage output from the fuel cell stack 36 to a predetermined voltage (for example, DC 250 V to 300 V), and interconnects the boosted DC voltage with the commercial power system 2. Includes an inverter that converts to AC voltage (for example, AC 200V). A power supply board 78 is connected to a power line branched from the power conditioner 70. The power supply board 78 converts a DC voltage output from the fuel cell stack 36 or an AC voltage from the commercial power system 2 into a DC voltage suitable for the operation of the auxiliary devices and supplies the DC voltage to the auxiliary devices. In the embodiment, the auxiliary equipment includes source gas supply valves 42 and 43, a source gas pump 45, an air blower 53, a reforming water pump 58, a circulation pump 63, and the like.

  The control device 80 is configured as a microprocessor mainly including a CPU 81, and in addition to the CPU 81, a ROM 82 for storing a processing program, a RAM 83 for temporarily storing data, a timer 84 for measuring time, and an input device (not shown). An output port. Various detection signals from the pressure sensor 47, the flow sensors 48 and 54, the current sensor 73, and the temperature sensors 91 to 93 are input to the control device 80 via input ports. In addition, the control device 80 sends a drive signal to the fan motor of the ventilation fan 24, a drive signal to the solenoids of the source gas supply valves 42 and 43, a drive signal to the pump motor of the source gas pump 45, and a drive signal of the air blower 53 to the blower motor. Drive signal, drive signal to the pump motor of the reforming water pump 58, drive signal to the pump motor of the circulation pump 63, control signal to the power conditioner 70 (DC / DC converter or inverter), control to the power supply board 78 A signal, a drive signal to the ignition heater 35, a display signal to a display panel 90 for displaying various information, and the like are output through an output port.

  In the fuel cell system 10 configured as described above, a system request value (system request output) based on the request output required by the load 4 is input, and the target stack current Iout * of the fuel cell stack 36 is calculated based on the input system request value. The source gas supply device 40, the reformed water supply device 55, and the air supply device 50 are controlled according to the set and set target stack current Iout *, and the power conditioner 70 is controlled. More specifically, the control of the source gas supply device 40 is performed by setting a target gas flow rate Fg * to be supplied by the source gas supply device 40 based on the target stack current Iout *, and using the target gas flow rate Fg * and the flow rate sensor 48. The duty Dg is set by feedback control based on a deviation from the detected gas flow rate Fg, and the pump motor of the raw material gas pump 45 is controlled based on the set duty Dg. The control of the reforming water supply device 55 is such that the steam carbon ratio (S / C), which is the ratio of the flow rate of the steam per unit time to the flow rate of the raw material gas supplied to the reformer 33, is a predetermined ratio. The target reforming water flow rate Fw * is set such that the following equation is satisfied, the duty Dw is set based on the set target reforming water flow rate Fw *, and the pump motor of the reforming water pump 58 is controlled based on the set duty Dw. It is done by doing. The air supply device 50 is controlled by setting a target air flow rate Fa * to be supplied by the air supply device 50 so as to have a predetermined ratio (air-fuel ratio) with respect to a target gas flow rate Fg * of the raw material gas, and setting the target value. This is performed by setting the duty Da by feedback control based on the difference between the air flow rate Fa * and the air flow rate Fa detected by the flow rate sensor 54, and controlling the blower motor of the air blower 53 based on the set duty Da. The power conditioner 70 is controlled by generating a PWM signal of the inverter of the power conditioner 70 by feedback control based on a deviation between the target stack current Iout * and the stack current Iout detected by the current sensor 73, and by using the generated PWM signal. This is performed by switching the inverter.

  Here, in the present embodiment, the target reforming water flow rate Fw * is set by changing the S / C based on the reformer temperature T detected by the temperature sensor 91. FIG. 2 is an explanatory diagram showing an example of the relationship between the reformer temperature T and S / C. As shown in the figure, in the present embodiment, the S / C is set to a larger ratio (value) when the reformer temperature T is high than when it is low. For example, when the reformer temperature T is a first temperature (high temperature) such as 600 ° C., the S / C is set to a value of 5, and when the reformer temperature T is lower than the first temperature, the S / C is S 2 at a second temperature (medium temperature) such as 450 ° C. / C is set to a value of 4, and S / C is set to a value of 3 at a third temperature (low temperature) such as 300 ° C. where the reformer temperature T is lower than the second temperature. When the reforming catalyst is exposed to a high temperature, coking is likely to occur in the reformer 33, so that the reforming performance may be reduced. For this reason, when the reformer temperature T is high, the S / C is changed to a large value in order to suppress a further rise in temperature and to prevent the reforming catalyst from being exposed to a high temperature. Thereby, the target reforming water flow rate Fw * set using S / C becomes a large value, and more reforming water is supplied to the vaporizer 32, so that it is possible to suppress a rise in temperature. . Further, a state in which the actual S / C is reduced to, for example, about 2 or less (low S / C state) is a state in which coking is likely to occur due to a small amount of water vapor and an excessive supply of the raw material gas. It can be said that. For this reason, it is necessary to monitor abnormalities in the reforming system such as the low S / C state and take appropriate measures.

  Hereinafter, the operation when monitoring the abnormality of the reforming system of the fuel cell system 10 will be described. FIG. 3 is a flowchart illustrating an example of a threshold setting processing routine, and FIG. 4 is a flowchart illustrating an example of an abnormality monitoring processing routine. These processes are executed by the CPU 81 of the control device 80. In the threshold setting routine of FIG. 3, the CPU 81 of the control device 80 first obtains the stack current Iout detected by the current sensor 73 as the output of the fuel cell stack 36 (S100), and the fluctuation of the obtained stack current Iout It is determined whether or not the state within the predetermined width has continued for a predetermined time (S110). The process of S110 is performed to determine that the output of the fuel cell stack 36 is in a stable state. For example, the fluctuation of the stack current Iout is changed over a predetermined time of about ten minutes, such as 10 minutes or 15 minutes. It is determined whether it is within a predetermined width of about several A.

  When determining that the state of the variation of the stack current Iout within the predetermined width has continued for the predetermined time in S110, the CPU 81 determines whether or not the monitoring flag is off (S120). When determining that the monitoring flag is off, the CPU 81 turns on the monitoring flag to execute the abnormality monitoring process (S130), and sets a threshold Tref which is a predetermined threshold for abnormality determination (S140). ), And terminates the threshold setting processing routine. On the other hand, if it is determined in S120 that the monitoring flag is ON instead of OFF, S130 and S140 are skipped, and the threshold setting processing routine ends. When the CPU 81 determines in S110 that the variation of the stack current Iout is not within the predetermined width, or determines that the variation does not continue for the predetermined time even within the predetermined width, the CPU 81 determines whether the monitoring flag is on. It is determined whether or not it is (S150). When determining that the monitoring flag is on, the CPU 81 turns off the monitoring flag (S160) and ends the threshold setting processing routine. On the other hand, if it is determined in S150 that the monitoring flag is not on but off, the process skips S160 and ends the threshold setting routine.

  In the setting of the threshold Tref in S140, the relationship between the stack current Iout and the threshold Tref is previously obtained and stored in the ROM 82 as a threshold setting map, and the threshold Tref corresponding to the stack current Iout acquired in S100 is derived from the map. It does by doing. FIG. 5 shows an example of the threshold value Tref setting map. As shown in the figure, the threshold value Tref is set to a first temperature (high temperature) such as 600 ° C. when the stack current Iout is equal to or less than the first current I1, and when the stack current Iout exceeds the first current I1, the second current When the temperature is equal to or lower than I2, the temperature is set to a second temperature (medium temperature) such as 450 ° C., and when the stack current Iout exceeds the second current I2, the temperature is set to a third temperature (low temperature) such as 300 ° C. That is, the threshold value Tref is set so that the temperature is higher when the stack current Iout is small than when it is large.

  Here, the reformer temperature T has a correlation with the amount of reforming water supplied to the vaporizer 32 and the amount of fuel off-gas passing through the fuel cell stack 36. As described above, the target reformed water flow rate Fw * is set using S / C. However, even if the same S / C is used, the target reformed water flow rate Fw * is set according to the target gas flow rate Fg *. As a result, the amount of the reforming water supplied to the vaporizer 32 also changes. For example, if the power generation output of the fuel cell stack 36 is high, the target gas flow rate Fg * increases and the target reforming water flow rate Fw * also increases. The porcelain temperature T tends to decrease. Conversely, if the power generation output is low, the target gas flow rate Fg * decreases and the target reforming water flow rate Fw * also decreases, so the amount of reforming water supplied to the vaporizer 32 decreases and the reformer temperature T Tend to be higher. When the power generation output is low, the supply amount of the raw material gas decreases, but the fuel utilization rate also decreases and excess fuel off-gas increases. The temperature T increases. As described above, even when the same S / C is used, the reformer temperature T (the temperature range of the reforming system) is obtained because the supply amount of the reforming water changes depending on the magnitude of the power generation output of the fuel cell stack 36. Will be different. The above-described low S / C state is a state in which the reforming water amount (steam) decreases, and thus occurs when the reformer temperature T becomes higher than the temperature assumed from the power generation output of the fuel cell stack 36. I can say. From these facts, in the present embodiment, the threshold Tref is set according to the magnitude of the stack current Iout, and the presence or absence of a high temperature abnormality that causes a low S / C state is monitored.

  In the abnormality monitoring processing routine of FIG. 4, the CPU 81 first determines whether or not the monitoring flag is on (S200). If it is determined that the monitoring flag is off instead of on, the CPU 81 ends this routine. On the other hand, when determining that the monitoring flag is ON in S200, the CPU 81 acquires the reformer temperature T detected by the temperature sensor 91 (S210), and determines whether or not the acquired reformer temperature T exceeds the threshold value Tref. It is determined (monitored) whether or not there is a high temperature abnormality (S220). When determining that the reformer temperature T does not exceed the threshold value Tref, the CPU 81 determines that there is no abnormality and ends the abnormality monitoring processing routine.

  On the other hand, if the CPU 81 determines that the reformer temperature T exceeds the threshold value Tref, it determines that a high temperature abnormality has occurred, outputs a warning that a high temperature abnormality (low S / C state) has occurred, and outputs a warning to the fuel cell system 10. Is abnormally stopped (S230), and the abnormality monitoring processing routine ends. The warning indicating that the high temperature abnormality has occurred may include information indicating that the supply amount of the reforming water is small or that the supply amount of the fuel gas is large, information useful for maintenance, and the like. In the present embodiment, the presence or absence of a high temperature abnormality is determined in a state where the power output of the fuel cell stack 36 is stable. Erroneous determination of a high temperature abnormality can be prevented.

  In the fuel cell system 10 of the embodiment described above, the threshold value Tref is set so that the temperature becomes higher when the stack current Iout is small than when the stack current Iout is large, and whether the reformer temperature T exceeds the threshold value Tref. The presence or absence of a high temperature abnormality in the reforming system (low S / C state) is monitored based on the condition. Therefore, monitoring can be appropriately performed regardless of the magnitude of the power generation output of the fuel cell stack 36. In addition, since the power generation output of the fuel cell stack 36 is monitored in a stable state, it is possible to appropriately monitor the output of the fuel cell stack 36 while eliminating the influence of the temperature change delay on the fluctuation of the power generation output.

  Further, the state in which the power generation output is stable can be determined by a simple process of determining whether or not the state of the variation of the stack current Iout within a predetermined range continues for a predetermined time. Further, when the reformer temperature T is high, the S / C is changed so as to have a larger ratio than when the reformer temperature T is low. Therefore, the occurrence of coking can be more appropriately prevented in combination with the monitoring of the presence or absence of a high temperature abnormality. Further, when the abnormality is detected, the fuel cell system 10 is stopped, so that the failure of the reforming system can be prevented.

  In the above-described embodiment, the power generation output is determined to be stable when the state of the variation of the stack current Iout within the predetermined width continues for the predetermined time. However, the present invention is not limited to this. For example, the power generation output may be stabilized based on the fulfillment of other conditions such as the amount of change per unit time being less than a predetermined amount in a high output state where the stack current Iout is relatively high. Alternatively, the power output from the power generation unit 20 may be determined to be in a stable state.

  In the above-described embodiment, when an abnormality is determined, a warning is output and a measure to stop the fuel cell system 10 is taken. However, the present invention is not limited to this, and any one of the measures may be taken. Good.

  In the embodiment described above, the threshold Tref corresponding to the stack current Iout is set in three steps. However, the threshold Tref may be set in two steps, or may be set in four or more steps. Alternatively, the setting is not limited to the stepwise setting, but may be the stepless setting.

  In the above-described embodiment, the S / C is changed so that the ratio is higher when the reformer temperature T is higher than when the reformer temperature T is lower. However, the present invention is not limited to this. May use a predetermined uniform S / C according to

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the section of “Means for Solving the Problems” will be described. In the embodiment, the fuel cell stack 36 corresponds to a “fuel cell”, the reformer 33 corresponds to a “reformer”, the source gas supply device 40 corresponds to a “source gas supply device”, and the vaporizer 32 Corresponds to a “vaporizer”, the reforming water supply device 55 corresponds to a “reforming water supply device”, the control device 80 corresponds to a “control device”, and the temperature sensor 91 corresponds to a “temperature detector”. I do.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the section of the means for solving the problem is as follows. This is merely an example for specifically describing a mode for carrying out the invention, and thus does not limit the elements of the invention described in the section of “Means for Solving the Problems”. That is, the interpretation of the invention described in the section of the means for solving the problem should be interpreted based on the description of the section, and the embodiment is an embodiment of the invention described in the section of the means for solving the problem. This is only a specific example.

  As described above, the embodiments for carrying out the present invention have been described using the embodiments. However, the present invention is not limited to these embodiments at all, and various forms are possible without departing from the gist of the present invention. Of course, it can be implemented.

  INDUSTRIAL APPLICABILITY The present invention is applicable to a fuel cell system manufacturing industry and the like.

  1 gas supply source, 2 commercial power source, 3 power lines, 4 load, 10 fuel cell system, 20 power generation unit, 22 housing, 22a intake port, 22b exhaust port, 24 ventilation fan, 30 fuel cell module, 31 module case, 32 vaporizer, 33 reformer, 34 combustion section, 35 ignition heater, 36 fuel cell stack, 37 combustion catalyst, 40 source gas supply device, 41 source gas supply pipe, 42, 43 source gas supply valve, 44 orifice, 45 Raw material gas pump, 46 desulfurizer, 47 pressure sensor, 48 flow sensor, 50 air supply device, 51 air supply tube, 52 filter, 53 air blower, 54 flow sensor, 55 reformed water supply device, 56 reformed water supply tube, 57 Reforming water tank, 58 Reforming water pump, 60 Exhaust heat recovery device, 61 Circulation pipe, 62 Heat Exchanger, 63 circulation pump, 66 condensed water supply pipe, 67 exhaust gas discharge pipe, 70 power conditioner, 73 current sensor, 78 power supply board, 80 control device, 81 CPU, 82 ROM, 83 RAM, 84 timer, 90 display Panel, 91-93 Temperature sensor, 100 hot water supply unit, 101 hot water storage tank.

Claims (4)

A fuel cell that generates power based on the fuel gas and the oxidant gas;
A reformer that reforms a raw material gas into a fuel gas using steam and supplies the fuel gas to the fuel cell;
A source gas supply device for supplying a source gas to the reformer,
A vaporizer for supplying steam reformed water to the reformer,
A reforming water supply device for supplying reforming water to the vaporizer,
Setting the target gas flow rate so that the fuel cell generates power according to the output required for the fuel cell, controlling the source gas supply device, and setting the target reforming water amount according to the target gas flow rate A control device for controlling the reformed water supply device,
A temperature detector for detecting a temperature of a reforming system including the vaporizer and the reformer,
With
The control device, in a state where the power generation output of the fuel cell is stable, executes a monitoring process of monitoring the presence or absence of a high temperature abnormality in which the temperature of the reforming system detected by the temperature detector exceeds a predetermined threshold,
The fuel cell system according to claim 1, wherein the predetermined threshold value is set such that the temperature is higher when the power generation output of the fuel cell is low than when the power generation output is high. The fuel cell system according to claim 1, wherein
The fuel cell system according to claim 1, wherein the control device is configured to stabilize the power generation output of the fuel cell when the fluctuation of the power generation output of the fuel cell is within a predetermined width for a predetermined time or more. The fuel cell system according to claim 1 or 2,
The control device sets the target reformed water amount based on the steam gas ratio and the target gas flow rate, which is a ratio between the raw material gas and steam,
The fuel cell system according to claim 1, wherein the steam carbon ratio is changed to be a larger ratio when the temperature of the reforming system detected by the temperature detector is high than when the temperature is low. The fuel cell system according to any one of claims 1 to 3, wherein
The fuel cell system, wherein the control device stops the system when a high temperature abnormality of the reforming system is detected by executing the monitoring process.

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