JP2012156065A - Solid electrolyte fuel cell device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell device capable of continuing an operation as much as possible within a range where safety is secured even when an abnormality occurs in a temperature sensor.SOLUTION: A controller 110 in a solid electrolyte fuel cell device 1 determines whether or not an abnormality occurs in temperature detection of a power generation chamber temperature sensor 142, and when, as a result of the determination, the controller determines that an abnormality occurs in the power generation chamber temperature sensor 142, the controller performs a substitute control mode in which temperature in a vessel is projected by open circuit voltage detection using a power state detection sensor 126.

Description

  The present invention relates to a solid oxide fuel cell device that generates power using a fuel gas and an oxidant gas.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, has electrodes attached to both sides thereof, supplies fuel gas on one side, and supplies the other This is a fuel cell device that generates power by supplying an oxidant gas (air, oxygen, etc.) to the side and generating a power generation reaction at a relatively high temperature.

  Specifically, this fuel cell apparatus (SOFC) is a fuel having a plurality of fuel cells that operate when fuel gas and oxidant gas (air, oxygen, etc.) flow from one end side to the other end side. Hydrogen-rich fuel that has a battery cell assembly, is supplied with a reformed gas (city gas, etc.), which is a raw material gas, and is introduced into a reformer containing a reforming catalyst. After reforming into gas, the fuel cell assembly is supplied.

  In the fuel cell device, the remaining fuel gas that has not been used for the power generation reaction in the fuel gas is burned and discharged to the outside as a combustion gas, while either one of the fuel gas and the oxidant gas is used as the external gas, The fuel cell assembly is supplied to the outside.

  The solid oxide fuel cell device (SOFC) includes a plurality of processes for reforming fuel gas in a reformer in a start-up process, that is, a partial oxidation reforming reaction process (POX process), an autothermal reforming reaction process ( An ATR process) and a steam reforming reaction process (SR process) are followed to shift to a power generation process (see, for example, Patent Document 1 below). In SOFC, the reformer, the fuel cell stack, and the like disposed in the fuel cell module storage chamber can be heated to the operating temperature by sequentially executing these steps.

  By the way, in addition to the operating temperature in the power generation process of SOFC being as high as 600 to 800 ° C., in order to lead to the power generation process while transitioning a plurality of processes as described above in the startup process, It is necessary to accurately grasp the temperature and switch the operating conditions. For this reason, a plurality of temperature sensors are arranged in a container in which the fuel cell assembly is housed to grasp the internal temperature.

  Such a temperature sensor has low durability compared to other parts constituting the solid oxide fuel cell device such as a fuel cell assembly, and the tendency is particularly remarkable under high temperature use conditions. Become a thing. Therefore, there is a need to replace the temperature sensor, but it is necessary to consider that the temperature sensor is also in a high temperature environment when replacing the temperature sensor. In the temperature sensor described in Patent Document 2 below, a protection tube is inserted into a high-temperature environment furnace, and the temperature sensor can be inserted into the protection tube. One proposal for replacement of the temperature sensor in a high-temperature environment I am doing.

JP 2004-319420 A JP-A-8-210923

  Since the technique described in Patent Document 2 proposes only replacement of the temperature sensor, if an abnormality occurs in the temperature sensor used in the solid oxide fuel cell device, the solid oxide fuel cell device It is necessary to stop the operation and replace the temperature sensor.

  However, in the first place, when an abnormality occurs in a temperature sensor with low durability, stopping the operation of the solid oxide fuel cell device only for the purpose of replacing the temperature sensor imposes an excessive burden on the user. Therefore, it should be avoided in actual use of the solid oxide fuel cell device.

  By the way, the internal temperature is accurately grasped by a temperature sensor, and a plurality of processes such as a partial oxidation reforming reaction process (POX process), an autothermal reforming reaction process (ATR process), and a steam reforming reaction process (SR process) are transitioned. It is necessary only in the start-up process to lead to the power generation process. Therefore, if the start-up process is overcome, the temperature measurement accuracy as high as the start-up process is not required in the power generation process that is in a stable reaction state. Focusing on the difference in the importance of temperature measurement accuracy between the start-up process and the power generation process, even if an abnormality occurs in the temperature sensor, the operation of the solid oxide fuel cell device is not stopped unnecessarily. The present inventors have found that there is a possibility that the operation can be continued while ensuring safety.

  The present invention has been made in view of such problems and knowledge, and its purpose is to continue operation as much as possible within a range in which safety is ensured even when an abnormality occurs in the temperature sensor. It is an object of the present invention to provide a solid oxide fuel cell device that can be used.

  In order to solve the above-described problems, a solid oxide fuel cell device according to the present invention is a solid oxide fuel cell device that generates power using a fuel gas and an oxidant gas, and reforms a raw material gas containing hydrocarbons. A reformer that generates fuel gas and a plurality of single cells that are electrically connected and are erected so as to be along each other, and the fuel gas and the oxidant are provided from one end side to the other end side of the plurality of single cells. A cell assembly that generates electricity by flowing gas, a container that houses the reformer and the cell assembly, a temperature sensor in a container that detects a temperature in the container, and a power state of the cell assembly. A power state sensor to be detected; and a control means for controlling an operation state of the solid oxide fuel cell device based on signals output from the in-container temperature sensor and the power state sensor. The control means determines whether or not an abnormality has occurred in the temperature detection of the temperature sensor in the container, and when it is determined that an abnormality has occurred in the temperature sensor in the container as a result of the determination, An alternative control mode is executed in which the operating state is controlled by detecting an open circuit voltage by the state sensor.

  Since the solid oxide fuel cell device according to the present invention is a solid oxide fuel cell device that generates power using fuel gas and oxidant gas, the in-container temperature sensor disposed inside the solid oxide fuel cell device is used under severe use at high temperatures. Exposed to the environment. On the other hand, since the solid oxide fuel cell device is a power generation device, it is required to continue the operation as much as possible even if an abnormality occurs in a part of the in-container temperature sensor. Therefore, when an abnormality occurs in the temperature sensor in the container, the control means executes an alternative control mode in which the operation state is controlled by detecting the open circuit voltage by the power state sensor. In this case, the present inventors have found that the temperature inside the container and the open circuit voltage are in a correlation, and based on this knowledge, the operation state is controlled using the open circuit voltage. As described above, even when an abnormality occurs in the temperature sensor inside the container, an abnormality occurs in a part of the temperature sensor inside the container by executing the alternative control mode using the normal power state sensor. However, the operation is not immediately stopped, and the user is not burdened with being unusable.

  In the solid oxide fuel cell device according to the present invention, the in-container temperature sensor is composed of a plurality of temperature sensors, and the control means includes the power state sensor and at least one of the plurality of temperature sensors if the temperature sensor is normal. It is also preferable to execute the alternative control mode by using it together and not execute the alternative control mode if an abnormality has occurred in all of the plurality of temperature sensors.

  As described above, since the open circuit voltage and the temperature in the container have a correlation, it can be estimated that the container is in a certain temperature band. However, it is difficult to know the temperature inside the container accurately and to know the tendency of the temperature inside the container. Therefore, in this preferred embodiment, if at least one of the plurality of temperature sensors is normal, it can be used in combination with the power state sensor, so that it is possible to use both the temperature estimation by the open circuit voltage and the temperature detection by the normal temperature sensor, The accuracy of grasping the temperature in the container can be improved. Further, if all of the in-container temperature sensors are abnormal, the alternative control mode is not executed, so that it is possible to prevent problems other than the abnormality in the temperature sensor from being expanded.

  In the solid oxide fuel cell device according to the present invention, the in-container temperature sensor includes a power generation chamber temperature sensor that detects the temperature of the cell assembly, and a reformer temperature sensor that detects the temperature of the reformer. And when the controller determines that an abnormality has occurred in the power generation chamber temperature sensor, the control means detects the open circuit voltage by the power state sensor and detects the reformer temperature by the reformer temperature sensor. It is also preferable to execute the alternative control mode by controlling a start-up process for transitioning the process from the partial oxidation reforming reaction process to the steam reforming reaction process through the autothermal reforming reaction process.

  In the solid oxide fuel cell device according to the present invention, since the power generation and the load following operation are not performed during the starting process, the correlation between the temperature in the container and the open circuit voltage is further increased. Therefore, in this preferred embodiment, by executing the alternative control mode using open circuit voltage detection in combination with the reformer temperature detection in the start-up step, the start-up step can be performed without stopping the operation of the solid oxide fuel cell device. Can be advanced.

  In the solid oxide fuel cell device according to the present invention, it is also preferable that the control means changes the transition temperature condition of the process transition in the start-up process so as to become a high temperature in the alternative control mode.

  As described above, since the open circuit voltage and the temperature in the container have a correlation, it can be estimated that the container is in a certain temperature band. However, it is difficult to know the temperature inside the container accurately and to know the tendency of the temperature inside the container. Therefore, in this preferable aspect, by changing the transition temperature condition of the process transition in the start-up process so as to become a high temperature in the alternative control mode, it is possible to prevent the process transition from being executed without the temperature in the container being increased. Therefore, it is possible to prevent the occurrence of problems other than abnormalities in the temperature sensor.

  In the solid oxide fuel cell device according to the present invention, the control means sets the transition temperature condition based on the reformer temperature detected by the reformer temperature sensor to a high temperature in the alternative control mode. It is also preferable to change.

  In this preferred embodiment, since the process transition can be performed by utilizing the fact that the temperature of the reformer that causes the endothermic reaction is sufficiently high, it is estimated that the temperature in the container is also increased to the required temperature. Therefore, the transition temperature condition based on the reformer temperature detected by the reformer temperature sensor is changed so as to be a high temperature in the alternative control mode. Therefore, it is possible to prevent the process transition from being performed without increasing the temperature in the container, and it is possible to prevent a problem other than an abnormality in the temperature sensor from being expanded.

  In the solid oxide fuel cell device according to the present invention, when the control means transitions from the start-up process to the power generation process, after satisfying the transition temperature condition from the steam reforming reaction process to the power generation process, It is also preferable to extend the period during which the steam reforming reaction step is continued.

  In the solid oxide fuel cell device according to the present invention, if the process proceeds to the power generation process without sufficiently increasing the temperature in the container, there is a possibility that a great number of problems may occur in parts other than the temperature sensor. Therefore, in this preferred embodiment, after satisfying the transition temperature condition from the steam reforming reaction step to the power generation step, the temperature in the container can be more reliably increased by extending the period for continuing the steam reforming reaction step. it can.

  In the solid oxide fuel cell device according to the present invention, the control means changes the upper limit value of the power generation output so as to be a low output in the alternative control mode after shifting from the start-up process to the power generation process. Is also preferable.

  In this preferred embodiment, when the process shifts to the power generation process while the alternative control mode is being executed, the influence of the variation in the container temperature is minimized by suppressing the upper limit value of the power generation output. Can do. Moreover, the effect which raises the temperature in a container uniformly can also be show | played by suppressing electric power generation output.

  In the solid oxide fuel cell device according to the present invention, it is also preferable that the control means lowers at least one of a fuel utilization rate and a power generation output in the power generation step in the alternative control mode.

  In this preferred embodiment, in the power generation process in the alternative control mode, by reducing at least one of the fuel utilization rate and the power generation output, the cause of the drop in the container temperature is eliminated, and problems other than abnormalities in the temperature sensor are expanded. Can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where abnormality arises in a temperature sensor, the solid oxide fuel cell apparatus which can continue a driving | operating as much as possible within the range which ensured safety can be provided.

1 is an overall configuration diagram showing a fuel cell device according to an embodiment of the present invention. 1 is a perspective view showing a fuel cell module in a state where a housing of a fuel cell device according to an embodiment of the present invention is removed. It is sectional drawing which looked at the fuel cell module of the fuel cell apparatus by one Embodiment of this invention from the A direction of FIG. It is sectional drawing which looked at the fuel cell module of the fuel cell apparatus by one Embodiment of this invention from the B direction of FIG. It is a front view which shows the fuel cell unit of the fuel cell apparatus by one Embodiment of this invention. FIG. 3 is a perspective view of the fuel cell module showing a state where a casing covering the fuel cell assembly is removed from the fuel cell module shown in FIG. 2. It is a perspective view which shows the evaporative mixer in the fuel cell module shown in FIG. It is the schematic plan view which looked at the heat exchanger of the fuel cell module of the fuel cell apparatus by one Embodiment of this invention from upper direction. 1 is a block diagram showing a fuel cell device according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by one Embodiment of this invention. It is a flowchart for demonstrating the control pattern in this embodiment. It is a flowchart for demonstrating the control pattern in this embodiment. It is a flowchart for demonstrating the control pattern in this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  A solid oxide fuel cell device that is a fuel cell device according to an embodiment of the present invention will be described. FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell according to an embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell 1 according to an embodiment of the present invention includes a fuel cell module 2 and an auxiliary unit 4.

  The fuel cell module 2 includes a housing 6. Inside the housing 6, a sealed space 8 is formed surrounded by a heat insulating material (not shown). A fuel cell assembly 12 that performs a power generation reaction with fuel gas and oxidant gas (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8.

  The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 6). The fuel cell stack 14 is composed of 16 fuel cell units 16 (single cell, see FIG. 5). The fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

  A combustion chamber 18 is formed in the sealed space 8 of the fuel cell module 2 above the power generation chamber 10 described above. In the combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant gas (air) are combusted to generate combustion gas (exhaust gas).

  Above the combustion chamber 18 is disposed a reformer 20 that reforms the raw material gas to generate fuel gas. The reformer 20 is heated to a temperature at which the reforming reaction can be performed by the combustion heat of the combustion gas described above. Further, a heat exchanger 22 for heating an oxidant gas (power generation air) introduced from the outside by heat of the combustion gas is disposed above the reformer 20.

  The auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as a tap water and makes it pure water with a filter, and a water flow rate adjusting unit 28 that adjusts the flow rate of water supplied from the water storage tank. (Such as a “water pump” driven by a motor). The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided.

  Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant gas supplied from an air supply source 40, and a reforming air flow rate adjustment unit 44 that adjusts the flow rate of air (driven by a motor). An “air blower” and the like, a power generation air flow rate adjustment unit 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and power generation And a second heater 48 for heating the power generation air supplied to the chamber. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at the time of startup, but may be omitted.

  The fuel cell module 2 is connected to a hot water production apparatus 50 to which exhaust gas is supplied. The hot water production apparatus 50 is supplied with tap water from the water supply source 24, and the tap water is heated by the heat of the exhaust gas and supplied to a hot water storage tank of an external hot water heater (not shown). The fuel cell module 2 is provided with a control box 52 for controlling the amount of fuel gas supplied and the like. The fuel cell module 2 is connected to an inverter 54 that is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module to the outside.

  Subsequently, the internal structure of the SOFC fuel cell module 2 according to the embodiment of the present invention will be described with reference to FIGS. 2 to 4, 6, and 7. FIG. 2 is a perspective view showing the fuel cell module 2 in a state where the housing 6 of the fuel cell device according to the embodiment of the present invention is removed. In FIG. 2, in each fuel cell stack 14 constituting the fuel cell module 2, the direction in which eight fuel cell units 16 are arranged is the x-axis direction. The direction in which the fuel cell unit 16 is erected and extends is the y-axis direction, and the direction orthogonal to the x-axis and the y-axis is the z-axis direction. The x-axis, y-axis, and z-axis described in FIG. 3 and thereafter are based on the x-axis, y-axis, and z-axis in FIG.

  FIG. 3 is a cross-sectional view of the fuel cell module 2 of the fuel cell apparatus according to the embodiment of the present invention as viewed from the direction A in FIG. 4 is a cross-sectional view of the fuel cell module 2 of the fuel cell apparatus according to the embodiment of the present invention as viewed from the direction B of FIG. FIG. 6 is a perspective view of the fuel cell module showing a state in which a casing covering the fuel cell assembly is removed from the fuel cell module shown in FIG. FIG. 7 is a perspective view showing an evaporating mixer in the fuel cell module shown in FIG.

  As shown in FIGS. 2 to 4, the fuel cell assembly 12 of the fuel cell module 2 is entirely covered with a casing 56. As shown in FIG. 6, the fuel cell assembly 12 has a substantially rectangular parallelepiped shape that is longer in the A direction than in the B direction, and includes an upper surface 12a, a lower surface 12b, and a long side surface 12c extending along the A direction in FIG. 2 is provided with a short side surface 12d extending along the direction B of FIG.

  As shown in FIG. 3, an evaporative mixer 58 is provided along the long side surface 12 c of the fuel cell assembly 12 in the lowermost portion of the sealed space 8 in the fuel cell module 2. The evaporative mixer 58 is heated by the combustion gas to turn water into water vapor, and to mix the water vapor with fuel gas (city gas) as reformed gas and air as oxidant gas. Is. As shown in FIGS. 2, 4, and 7, a reformed gas supply pipe 60 and a water supply pipe 62 are connected to one end side of the evaporation mixer 58. The to-be-reformed gas supply pipe 60 introduces the to-be-reformed gas (raw material gas) and the reforming air from the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44.

  As shown in FIG. 4, the lower end of the fuel supply pipe 64 is connected to the other end side of the evaporative mixer 58. The upper end of the fuel supply pipe 64 is connected to the upstream end of the reformer 20. The fuel gas is supplied from the evaporation mixer 58 to the reformer 20 through the fuel supply pipe 64. The upper end of the fuel supply pipe 66 is connected to the downstream end of the reformer 20. The lower end side 66a of the fuel supply pipe 66 enters the fuel gas tank 68 and extends in the horizontal direction.

  As shown in FIGS. 3 and 4, the fuel gas tank 68 is provided directly below the fuel cell assembly 12. A plurality of small holes (not shown) are formed along the longitudinal direction (A direction) on the outer periphery of the lower end side 66 a of the fuel supply pipe 66 inserted into the fuel gas tank 68. The fuel gas reformed by the reformer 20 is uniformly supplied in the longitudinal direction into the fuel gas tank 68 through the plurality of small holes (not shown). The fuel gas supplied to the fuel gas tank 68 is supplied into a fuel gas flow path 88 (see FIG. 5) inside the fuel cell unit 16 and rises in the fuel cell unit 16 to enter the combustion chamber 18. It has come to.

  Next, a structure for supplying power generation air to the fuel cell module 2 will be described. As shown in FIG. 2-4, above the reformer 20, along the upper surface 12 a and the short side surface 12 d (the right short side surface in FIGS. 2 and 4) of the fuel cell assembly 12 of the fuel cell module 2. A heat exchanger 22 is provided. The heat exchanger 22 is provided with a plurality of combustion gas pipes 70 and a power generation air flow path 72 formed around the combustion gas pipes 70.

  In the present embodiment, the heat exchanger 22 is provided along the upper surface 12a and the right short side surface 12d of the fuel cell assembly 12, but not limited thereto, the heat exchanger 22 is provided. Further, it may be provided along only the right short side surface 12d, may be provided only along both the right and left short side surfaces 12d, and further along the upper surface 12a and the short side surfaces 12d on both sides. It may be provided.

  As shown in FIG. 2, an introduction port 74 a of a power generation air introduction pipe 74 is attached to one end side of the lower end of the portion provided along the short side surface 12 d of the heat exchanger 22. The power generation air is introduced into the heat exchanger 22 from the power generation air flow rate adjustment unit 45 by the power generation air introduction pipe 74.

  As shown in FIGS. 4 and 8, an outlet port 72 a of the power generation air flow path 72 is formed on the other end on the upper side of the heat exchanger 22. Further, as shown in FIG. 3, power generation air supply passages 76 are formed on the outer sides of both sides in the width direction (B direction: short side surface direction) of the casing 56 of the fuel cell module 2. Power generation air is supplied from an outlet port 72 a of the power generation air flow path 72. The power generation air supply path 76 is formed along the longitudinal direction of the fuel cell assembly 12 (in the direction of the long side surface 12c). Furthermore, in order to blow out the air for power generation toward each fuel cell unit 16 of the fuel cell assembly 12 in the power generation chamber 10 at a position corresponding to the lower side of the fuel cell assembly 12 below the fuel cell assembly 12. Are formed at equal intervals along the longitudinal direction. The power generation air blown out from these air outlets 78 flows from below to above along the outside of each fuel cell unit 16.

  Next, a structure for discharging combustion gas generated by combustion of fuel gas and power generation air (oxidant gas) will be described. As described above, a plurality of combustion gas pipes 70 are provided in the heat exchanger 22 for discharging the combustion gas generated by burning the fuel gas and the power generation air (oxidant gas) in the combustion chamber 18. It has been. As shown in FIG. 4, a combustion gas discharge chamber 80 located below the fuel cell assembly 12 and extending in the longitudinal direction is formed on the downstream end side of these combustion gas pipes 70. The side and the combustion gas discharge chamber 80 are connected. The above-described evaporative mixer 58 is disposed in the combustion gas discharge chamber 80, and the fuel gas in the evaporative mixer 58 is heated along the longitudinal direction by the high-temperature combustion gas. ing. Further, a combustion gas discharge pipe 82 is connected to the lower surface of the combustion gas discharge chamber 80 so that the combustion gas is discharged to the outside.

  Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 5 is a partial cross-sectional view showing a SOFC fuel cell unit according to an embodiment of the present invention. As shown in FIG. 5, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.

  The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 inside (inside), a cylindrical outer electrode layer 92, and an inner electrode layer. 90 and an electrolyte layer 94 between the outer electrode layer 92 and the outer electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

  Since the inner electrode terminals 86 attached to the upper end side and the lower end side of the fuel cell unit 16 have the same structure, the inner electrode terminal 86 attached to the upper end side will be specifically described here. The upper portion 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an upper end surface 90 c exposed to the electrolyte layer 94 and the outer electrode layer 92. The inner electrode terminal 86 is connected to the outer peripheral surface 90b of the inner electrode layer 90 through a conductive sealing material 96, and is further in direct contact with the upper end surface 90c of the inner electrode layer 90, thereby Electrically connected. A fuel gas passage 98 communicating with the fuel gas passage 88 of the inner electrode layer 90 is formed at the center of the inner electrode terminal 86.

  The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 94 is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

  Next, sensors and the like attached to the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 9 is a block diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.

  As shown in FIG. 9, the solid oxide fuel cell 1 includes a control unit 110. The control unit 110 includes an operation device 112 having operation buttons such as “ON” and “OFF” for operation by the user, and a display for displaying various data such as a power generation output value (wattage). A device 114 and a notification device 116 that issues a warning (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

  Signals from various sensors described below are input to the control unit 110. The combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4. The CO detection sensor 122 indicates whether or not CO in the exhaust gas originally discharged to the outside through the combustion gas discharge chamber 80 or the like has leaked to an external housing (not shown) that covers the fuel cell module 2 and the accessory unit 4. It is for detection. The hot water storage state detection sensor 124 is for detecting the temperature and amount of hot water in a water heater (not shown).

  The power state detection sensor 126 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown). The power state detection sensor 126 is configured to detect an open circuit voltage. The power generation air flow rate detection sensor 128 is for detecting the flow rate of the power generation air supplied to the power generation chamber 10. The reforming air flow rate sensor 130 is for detecting the flow rate of the reforming air supplied to the reformer 20. The fuel flow sensor 132 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

  The water flow rate sensor 134 is for detecting the flow rate of pure water (steam) supplied to the reformer 20. The water level sensor 136 is for detecting the water level of the pure water tank 26. The pressure sensor 138 is for detecting the pressure on the upstream side outside the reformer 20. The exhaust temperature sensor 140 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

  As shown in FIGS. 3 and 4, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14, This is for estimating the temperature of the battery cell stack 14 (that is, the fuel battery cell 84 itself).

  The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18. As shown in FIGS. 3 and 4, the combustion chamber temperature sensor 144 is provided between the fuel cell assembly 12 and the ignition device 83. The combustion chamber temperature sensor 144 also functions as an ignition confirmation temperature sensor (first temperature sensor) for determining whether or not the fuel cell 84 has been ignited. The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the combustion gas discharge chamber 80.

  The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20. As shown in FIGS. 3 and 4, the reformer temperature sensor 148 is provided in the vicinity of each of the inlet side and the outlet side of the reformer 20. The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

  Signals from these sensors are sent to the control unit 110. The control unit 110 sends control signals to the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, and the power generation air flow rate adjustment unit 45 based on the data based on these signals. Each flow rate in the unit is controlled. Further, the control unit 110 sends a control signal to the inverter 54 to control the power supply amount.

  Next, the operation at the time of start-up by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 10 is a time chart showing the operation at the start-up of the solid oxide fuel cell (SOFC) according to one embodiment of the present invention.

  Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

  First, reforming air is supplied from the reforming air flow rate adjustment unit 44 to the reformer 20 of the fuel cell module 2 via the first heater 46. At the same time, power generation air is supplied from the power generation air flow rate adjustment unit 45 to the heat exchanger 22 of the fuel cell module 2 via the second heater 48. The power generation air reaches the power generation chamber 10 and the combustion chamber 18 via the heat exchanger 22.

  Immediately thereafter, fuel gas is supplied from the fuel flow rate adjustment unit 38. This fuel gas is mixed with reforming air, passes through the reformer 20, the fuel cell stack 14, and the fuel cell unit 16, and reaches the combustion chamber 18.

  Next, the ignition device 83 is ignited to burn the fuel gas and air (reforming air and power generation air) in the combustion chamber 18. Exhaust gas is generated by the combustion of the fuel gas and air, and the power generation chamber 10 is warmed by the exhaust gas, and when the exhaust gas rises in the sealed space 8 of the fuel cell module 2, The fuel gas containing the reforming air is warmed, and the power generation air in the heat exchanger 22 is also warmed.

At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction POX shown in FIG.
C _m H _n + xO ₂ → bCO + cH ₂ (1)
Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. The fuel gas heated by the exothermic reaction is supplied below the fuel cell stack 14 through the fuel supply pipe 64. Thereby, the fuel cell stack 14 is heated from below. Since the combustion chamber 18 is also heated by burning the fuel gas and air, the fuel cell stack 14 is also heated from above. As a result, the fuel cell stack 14 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

  After the partial oxidation reforming reaction POX is started, the water flow rate is determined based on the temperature of the reformer 20 detected by the reformer temperature sensor 148 and the temperature of the fuel cell stack 14 detected by the power generation chamber temperature sensor 142. The adjustment unit 28, the fuel flow rate adjustment unit 38, and the reforming air flow rate adjustment unit 44 start supplying a gas in which fuel gas, reforming air, and water vapor are mixed in advance to the reformer 20. At this time, in the reformer 20, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used proceeds.

  Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 20 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

After the start of the autothermal reforming reaction ATR shown in Formula (2), the temperature of the reformer 20 detected by the reformer temperature sensor 148 and the temperature of the fuel cell stack 14 detected by the power generation chamber temperature sensor 142 Based on the above, the supply of reforming air by the reforming air flow rate adjusting unit 44 is stopped and the supply of water vapor by the water flow rate adjusting unit 28 is increased.
C _m H _n + xO ₂ + yH ₂ O → bCO + cH ₂ (2)
As a result, the reformer 20 is supplied with a gas that does not contain air and contains only fuel gas and water vapor, and the steam reforming reaction SR of formula (3) proceeds in the reformer 20.
C _m H _n + xH ₂ O → bCO + cH ₂ (3)
Since the steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 18. At this stage, since the fuel cell module 2 is in the final stage of start-up, the power generation chamber 10 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 10 is greatly reduced in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 18.

  In this way, after the fuel cell module 2 is ignited by the ignition device 83, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the inside of the power generation chamber 10 The temperature gradually increases. As shown in FIG. 10, in the startup process, the temperature rise in the power generation chamber 10 and the open circuit voltage OCV of the fuel cell stack 14 are in a correlation. After the above startup processing is completed, power is taken out from the fuel cell module 2 to the inverter 54. That is, power generation is started. Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises.

  Even after the start of power generation, in order to maintain the temperature of the reformer 20, fuel gas and power generation air that are larger than the amount of fuel gas and power generation air consumed for power generation in the fuel cell 84 are supplied and burned. The combustion in the chamber 18 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

  In the start-up process shown in FIG. 10, although the partial oxidation reforming reaction (POX) process, the autothermal reforming reaction (ATR) process, and the steam reforming reaction (SR) process have been described as single processes, It is also preferable that each of the steps is subdivided. An example will be described in which the POX process is subdivided into a POX1 process and a POX2 process, the ATR process is subdivided into an ATR1 process and an ATR2 process, and the SR process is subdivided into an SR1 process and an SR2 process.

  First, the control unit 110 sends a signal to the reforming air flow rate adjustment unit 44 and the power generation air flow rate adjustment unit 45 to activate them, and the reforming air (oxidant gas) and the power generation air are supplied to the fuel cell. Supply to module 2. Note that the supply amount of reforming air to be supplied is set to 10.0 (L / min), and the supply amount of power generation air is set to 100.0 (L / min).

  Next, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to start supplying fuel gas to the reformer 20. Thereby, the fuel gas and the reforming air sent to the reformer 20 are sent into each fuel cell unit 16 via the reformer 20, the fuel supply pipe 64, and the manifold 66. The fuel gas and reforming air sent into each fuel cell unit 16 flow out from the upper end of the fuel gas flow path 98 of each fuel cell unit 16. Note that the supply amount of the fuel gas to be supplied is set to 6.0 (L / min).

  Further, the control unit 110 sends a signal to the ignition device 83 to ignite the fuel gas flowing out from the fuel cell unit 16. As a result, the fuel gas is combusted in the combustion chamber 18, and the reformer 20 disposed above the fuel gas is heated by the exhaust gas generated thereby, and the combustion chamber 18, the power generation chamber 10, and the inside thereof. The temperature of the disposed fuel cell stack 14 (hereinafter referred to as “cell stack temperature”) also increases. The fuel cell unit 16 including the fuel gas passage 98 and the upper end portion thereof correspond to a combustion portion.

  When the temperature of the reformer 20 (hereinafter referred to as “reformer temperature”) rises to about 300 ° C. by heating the reformer 20, a partial oxidation reforming reaction (POX) occurs in the reformer 20. ) Occurs (the POX1 process starts). Since the partial oxidation reforming reaction is an exothermic reaction, the reformer 20 is also heated by the reaction heat due to the occurrence of the partial oxidation reforming reaction.

  When the temperature further rises and the reformer temperature reaches 350 ° C. (POX2 transition condition), the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to reduce the fuel gas supply amount and the reforming air. A signal is sent to the flow rate adjusting unit 44 to increase the supply amount of reforming air (POX2 process start). Thereby, the fuel gas supply amount is changed to 5.0 (L / min), and the reforming air supply amount is changed to 18.0 (L / min). These supply amounts are appropriate supply amounts for generating the partial oxidation reforming reaction. That is, in the initial temperature region where the partial oxidation reforming reaction starts to occur, by increasing the ratio of the fuel gas to be supplied, a state in which the fuel gas is surely ignited is formed and the supply amount is maintained. Ignition is stabilized (see “POX1” step in FIG. 9). Furthermore, after ignition is stably performed and the temperature rises, waste of fuel is suppressed as a sufficient fuel gas supply amount necessary for generating the partial oxidation reforming reaction.

  Next, when the reformer temperature is 600 ° C. or higher and the cell stack temperature is 250 ° C. or higher (ATR1 transition condition), the control unit 110 sends a signal to the reforming air flow rate adjusting unit 44 for reforming. While reducing the air supply amount, a signal is sent to the water flow rate adjusting unit 28 to start the supply of water (ATR1 process start). As a result, the reforming air supply amount is changed to 8.0 (L / min), and the water supply amount is set to 2.0 (cc / min). By introducing water (steam) into the reformer 20, a steam reforming reaction also occurs in the reformer 20. That is, in the ATR1 step, autothermal reforming (ATR) in which a partial oxidation reforming reaction and a steam reforming reaction are mixed occurs.

  The cell stack temperature is measured by a power generation chamber temperature sensor 142 disposed in the power generation chamber 10. Although the temperature inside the power generation chamber and the cell stack temperature are not exactly the same, the temperature detected by the power generation chamber temperature sensor reflects the cell stack temperature, and the cell temperature is detected by the power generation chamber temperature sensor located in the power generation chamber. The stack temperature can be grasped. In the present specification, the cell stack temperature means a temperature measured by an arbitrary sensor that indicates a value reflecting the cell stack temperature.

  Further, when the reformer temperature is 600 ° C. or higher and the cell stack temperature is 400 ° C. or higher (ATR2 transition condition), the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to decrease the fuel gas supply amount. . Further, the control unit 110 sends a signal to the reforming air flow rate adjustment unit 44 to reduce the reforming air supply amount and sends a signal to the water flow rate adjustment unit 28 to increase the water supply amount (ATR2). Process start). Accordingly, the fuel gas supply amount is changed to 4.0 (L / min), the reforming air supply amount is changed to 4.0 (L / min), and the water supply amount is set to 3.0 (cc / min). ). By reducing the reforming air supply amount and increasing the water supply amount, the ratio of the partial oxidation reforming reaction that is an exothermic reaction is reduced in the reformer 20, and the steam reforming that is an endothermic reaction. The rate of reaction increases. As a result, an increase in the reformer temperature is suppressed, and on the other hand, the fuel cell stack 14 is heated by the gas flow received from the reformer 20, whereby the cell stack temperature rises to catch up with the reformer temperature. As the temperature is increased, the temperature difference between the two is reduced, and the temperature is stably increased.

  Next, when the temperature difference between the reformer temperature and the cell stack temperature is reduced and the reformer temperature is 650 ° C. or higher and the stack temperature is 600 ° C. or higher (SR1 transition condition), the control unit 110 A signal is sent to the air flow rate adjusting unit 44 to stop the supply of reforming air. Further, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to decrease the fuel gas supply amount, and sends a signal to the water flow rate adjustment unit 28 to increase the water supply amount (SR1 process start). Accordingly, the fuel gas supply amount is changed to 3.0 (L / min), and the water supply amount is changed to 8.0 (cc / min). When the supply of reforming air is stopped, the partial oxidation reforming reaction does not occur in the reformer 20, and SR in which only the steam reforming reaction occurs is started.

  When the temperature difference between the reformer temperature and the cell stack temperature is further reduced and the reformer temperature is 650 ° C. or higher and the stack temperature is 650 ° C. or higher (SR2 transition condition), the controller 110 controls the fuel flow rate adjustment unit 38. Is sent to the water flow rate adjusting unit 28 to reduce the supply amount of water. Further, the control unit 110 sends a signal to the power generation air flow rate adjustment unit 45 to reduce the supply amount of the power generation amount air (SR2 process start). Thereby, the fuel gas supply amount is changed to 2.3 (L / min), the water supply amount is changed to 6.3 (cc / min), and the power generation air supply amount is 80.0 (L / min). Changed to

  In the SR1 process, the fuel gas supply amount and the water supply amount are kept high in order to raise the reformer temperature and the stack temperature to near the temperature at which power generation is possible. Thereafter, in the SR2 step, the fuel gas flow rate and the water supply amount are reduced, the temperature distributions of the reformer temperature and the cell stack temperature are settled, and are stabilized in a temperature range where power generation is possible.

  In the SR2 step, the control unit 110 reduces each supply amount including the fuel gas supply amount at a predetermined reduction rate to a supply amount for the SR2 step, and maintains it for a predetermined power generation transition period. Thus, the reformer 20, the fuel cell stack 14 and the like are kept in a stable state for a predetermined power generation transition period until the power generation shift, and the temperatures such as the reformer temperature and the cell stack temperature in the fuel cell module 2 are maintained. Distribution can be calmed down. That is, the power generation transition period functions as a stabilization period after the supply amount is reduced.

  When the reformer temperature is 650 ° C. or higher and the stack temperature is 700 ° C. or higher after the predetermined power generation transition period has elapsed (power generation process transition condition), power is output from the fuel cell module 2 to the inverter 54, The power generation process starts and power generation starts (power generation process starts).

  Subsequently, in the solid oxide fuel cell 1 according to the present embodiment, the power generation chamber temperature sensor 142 (second temperature sensor), the combustion chamber temperature sensor 144 (first temperature sensor), and the reformer temperature sensor 148 (second Processing when an abnormality (error) occurs in at least one of the temperature sensors will be described with reference to FIGS. FIG. 11 is a flowchart for explaining processing when a temperature sensor error (abnormality) occurs. FIG. 12 is a flowchart for explaining processing in the startup period when a temperature sensor error has occurred. FIG. 13 is a flowchart for explaining processing in a power generation period when a temperature sensor error has occurred.

  As shown in FIG. 11, when a temperature sensor error occurs, the control unit 110 determines whether the flag F = 2 (step S01). If the flag F = 2, the process proceeds to step S06. If the flag F = 2 is not satisfied, the process proceeds to step S02.

  In step S02, the control unit 110 determines whether the temperature sensor error status is a system stop error status. Specifically, both of the two reformer temperature sensors 148 are simultaneously in an error state, or all of the power generation chamber temperature sensor 142, the combustion chamber temperature sensor 144, and the reformer temperature sensor 148 are in an error state. If so, it is determined that a system stop error has occurred. If the temperature sensor error status is a system stop error status, the process proceeds to step S06. If the temperature sensor error status is not a system stop error status, the process proceeds to step S03.

  In step S03, the control unit 110 determines whether the temperature sensor error status is a provisional operation continuation error status. If the temperature sensor error status is a provisional operation continuation error status, the process proceeds to step S05. If the temperature sensor error status is not a provisional operation continuation error status, the process proceeds to step S04.

  In step S04, the control unit 110 sets a flag F = 0 to perform normal operation. In step S05, the control unit 110 sets a flag F = 1 to perform the temporary operation continuation control at the time of abnormality. In step S06, the control unit 110 sets a flag F = 2 to stop the system.

  Next, the control at the time of activation will be described with reference to FIG. In step S11, the control unit 110 determines whether or not the flag F = 1. If flag F = 1, return to perform provisional continuous operation. If the flag F is not 1, the process proceeds to step S12.

  In step S12, the control unit 110 determines whether or not the operating state of the solid oxide fuel cell 1 is the startup period. If the operation state of the solid oxide fuel cell 1 is the start-up period, the process proceeds to step S13, and if the operation state of the solid oxide fuel cell 1 is not the start-up period, the process returns.

  In step S13, control unit 110 determines whether combustion chamber temperature sensor 144 is in an error state. If the combustion chamber temperature sensor 144 is in an error state, the process proceeds to step S16. If the combustion chamber temperature sensor 144 is not in an error state, the process proceeds to step S14.

  In step S14, the control unit 110 determines whether the power generation chamber temperature sensor 142 is in an error state. If the power generation chamber temperature sensor 142 is in an error state, the process proceeds to step S17. If the power generation chamber temperature sensor 142 is not in an error state, the process proceeds to step S15.

  In step S15, the control unit 110 determines whether the reformer temperature sensor 148 is in an error state. If the reformer temperature sensor 148 is in an error state, the process proceeds to step S18, and if the reformer temperature sensor 148 is not in an error state, the process returns.

  In step S <b> 16, the control unit 110 performs the ignition determination for determining whether or not the fuel gas is ignited in the fuel cell 84 (single cell) included in the fuel cell assembly 12 from the determination by the combustion chamber temperature sensor 144. Then, the determination is made by the reformer temperature sensor 148. Further, the control unit 110 switches from the frequency of performing the ignition frequency by the ignition device 83 three times in a 10-second cycle to the frequency of performing 15-second ignition and five-second stop five times. Further, the control unit 110 increases the voltage applied to the spark plug in the ignition device 83 by 20%. Further, in the ignition determination, the controller 110 determines to ignite if the temperature rises by 100 ° C. in 3 seconds, and switches to determine that it has ignited if the temperature rises by 50 ° C. in 10 seconds. Furthermore, the control unit 110 reduces the flow rate of the air supplied to the fuel cell assembly 12 by 10%. Further, the control unit 110 increases the flow rate of the air supplied to the reformer 20 by 5%. When the processing in step S16 is completed, the process returns.

  In step S <b> 17, the control unit 110 switches the estimation of the stack temperature, which is the temperature of the fuel cell assembly 12, from the estimation using the power generation chamber temperature sensor 142 to the estimation based on the OCV voltage value. As shown in FIG. 10, since there is a correlation between the stack temperature and the OCV voltage value, the stack temperature is estimated using this relationship. Further, the control unit 110 increases the threshold value based on the temperature value of the reformer 20 by 20 ° C. Furthermore, the control unit 110 increases the transition condition to the autothermal reforming reaction (ATR) process by 40 ° C., and increases the transition condition to the steam reforming reaction (SR) process by 20 ° C. Further, the control unit 110 executes control to limit the transition to the power generation process for 3 minutes after the temperature reaches the condition for satisfying the transition condition to the power generation process. Further, the control unit 110 executes control for limiting the rated maximum value to 400 W for 10 minutes after the shift to the power generation process. Further, the controller 110 increases the flow rate of the supplied fuel gas by 5% for 10 minutes after the shift to the power generation process. When the process in step S17 is completed, the process returns.

  In step S <b> 18, the control unit 110 prohibits reading from the reformer temperature sensor 148 in the error state among the reformer temperature sensors 148. Further, the control unit 110 increases the temperature value of the reformer 20 read from the reformer temperature sensor 148 by 20 ° C. Further, the control unit 110 executes control to limit the transition to the power generation process for 3 minutes after the temperature reaches the condition for satisfying the transition condition to the power generation process. Further, the control unit 110 executes control for limiting the rated maximum value to 400 W for 10 minutes after the shift to the power generation process. Further, the controller 110 increases the flow rate of the supplied fuel gas by 5% for 10 minutes after the shift to the power generation process. When the process in step S18 is completed, the process returns.

  Next, control during power generation will be described with reference to FIG. In step S21, the control unit 110 determines whether the flag F = 1. If flag F = 1, return to perform provisional continuous operation. If the flag F is not 1, the process proceeds to step S22.

  In step S22, the control unit 110 determines whether the operation state of the solid oxide fuel cell 1 is the power generation period. If the operation state of the solid oxide fuel cell 1 is the power generation period, the process proceeds to step S23, and if the operation state of the solid oxide fuel cell 1 is not the power generation period, the process returns.

  In step S23, the control unit 110 determines whether the combustion chamber temperature sensor 144 is in an error state. If the combustion chamber temperature sensor 144 is in an error state, the process proceeds to step S26, and if the combustion chamber temperature sensor 144 is not in an error state, the process proceeds to step S24.

  In step S24, the control unit 110 determines whether the power generation chamber temperature sensor 142 is in an error state. If the power generation chamber temperature sensor 142 is in an error state, the process proceeds to step S27. If the power generation chamber temperature sensor 142 is not in an error state, the process proceeds to step S25.

  In step S25, the control unit 110 determines whether the reformer temperature sensor 148 is in an error state. If the reformer temperature sensor 148 is in an error state, the process proceeds to step S28, and if the reformer temperature sensor 148 is not in an error state, the process returns.

  In step S <b> 26, the control unit 110 prohibits reading from the combustion chamber temperature sensor 144. When the process of step S26 ends, the process returns.

In step S <b> 27, the control unit 110 switches the estimation of the stack temperature, which is the temperature of the fuel cell assembly 12, from the estimation using the power generation chamber temperature sensor 142 to the estimation using the reformer temperature sensor 148. Further, the control unit 110 increases the temperature value read by the reformer temperature sensor 148 by 20 ° C. Furthermore, the control unit 110 lowers the upper threshold value of the temperature determined to be abnormal in the power generation operation by 10 ° C. and increases the lower threshold value by 10 ° C.
When the processing in step S27 is completed, the process returns.

  In step S <b> 28, the control unit 110 prohibits reading from the reformer temperature sensor 148 in the error state among the reformer temperature sensors 148. Further, the control unit 110 increases the temperature value of the reformer 20 read from the reformer temperature sensor 148 by 20 ° C. Furthermore, the control unit 110 lowers the upper threshold value of the temperature determined to be abnormal in the power generation operation by 10 ° C. and increases the lower threshold value by 10 ° C. When the process in step S28 is completed, the process returns.

  As described above, in the present embodiment, the control unit 110 determines whether or not an abnormality has occurred in the temperature detection of the combustion chamber temperature sensor 144 (first temperature sensor). An alternative detection control mode (step S13 in FIG. 12, step S13 in FIG. 12) that detects ignition of fuel gas in a specific single cell by detecting the temperature with another temperature sensor (second temperature sensor) when it is determined that an abnormality has occurred. S16) is executed.

  Since the solid oxide fuel cell 1 according to the present embodiment is a solid oxide fuel cell device that generates power using fuel gas and oxidant gas, the combustion chamber temperature sensor 144 and other temperature sensors disposed therein are used. (The power generation chamber temperature sensor 142 and the reformer temperature sensor 148) are exposed to a high-temperature and severe environment. On the other hand, since the solid oxide fuel cell 1 is a power generation device, it is required to continue operation as much as possible even if an abnormality occurs in a part of the temperature sensor. Therefore, when an abnormality occurs in the combustion chamber temperature sensor 144 that detects ignition of the fuel gas in a specific unit cell by detecting a temperature increase on the other end side of the specific unit cell, the control unit 110 performs other processing. An alternative detection control mode in which ignition of fuel gas in a specific single cell is detected by temperature detection by a temperature sensor is executed. As described above, even if an abnormality occurs in the first temperature sensor, an abnormality occurs in a part of the temperature sensor by executing the alternative detection control mode using the normal second temperature sensor. However, the operation is not immediately stopped, and the user is not burdened with being unusable.

  In the present embodiment, the reformer temperature sensor 148 is used as an alternative to the combustion chamber temperature sensor 144, and the controller 110 ignites the ignition frequency of the ignition device 83 so as to enhance the ignition performance of the ignition device 83 in the alternative detection control mode. And the control which changes ignition force is performed (step S16 of FIG. 12).

  Thus, since the reformer temperature sensor 148 that is an alternative temperature sensor detects the temperature of the reformer 20, it is difficult to directly detect the ignition of the fuel gas in the single cell. In the alternative detection control mode, control is performed so that the ignition performance of the ignition device 83 is enhanced, so that it is possible to avoid continuing the operation while the ignition is poor.

  In the present embodiment, the control unit 110 detects that the fuel gas has been ignited in a specific single cell when the temperature rises within a predetermined period after the ignition operation by the ignition device 83, and the alternative detection In the control mode, the predetermined period is extended and the ignition frequency of the ignition device 83 is increased.

  As described above, since the ignition detection by the combustion chamber temperature sensor 144 is switched to the ignition detection by the reformer temperature sensor 148, even if the ignition performance by the ignition device 83 is improved, it is determined whether or not the ignition is surely performed. It will be difficult to do. Therefore, when it is detected that the fuel gas has been ignited in a specific single cell when the temperature rises within a predetermined period, the predetermined period is extended (in step S16 in FIG. 12, it is extended from 3 seconds to 10 seconds). As a result, the criterion for ignition detection in a specific single cell is relaxed. As described above, in addition to relaxing the criteria for determining the ignition detection in a specific single cell, by increasing the ignition frequency of the ignition device 83, erroneous determination of ignition in the specific single cell and erroneous control resulting from the erroneous determination are prevented. Try to avoid.

  In the present embodiment, the control unit 110 increases the number of repetitions of the ignition operation by the ignition device 83 in the alternative detection control mode. By increasing the number of repetitions of the ignition operation by the igniter 83, it is possible to reliably avoid ignition failure in a specific single cell and to avoid abnormal processing despite ignition in the specific single cell. be able to.

  In the present embodiment, the control unit 110 performs ignition promotion control that promotes ignition of fuel gas in a specific single cell, and the control unit 110 extends the execution period of ignition promotion control in the alternative detection control mode. is doing.

  In the start-up process of the solid oxide fuel cell 1 according to the present embodiment, the partial oxidation reforming reaction process (POX process), the autothermal reforming reaction process (ATR process), the steam reforming reaction process (SR process) and the processes are performed. The internal temperature rises as it progresses, and if it exceeds a predetermined temperature, the fuel gas spontaneously ignites in all of the plurality of single cells. In the temperature range leading to this spontaneous ignition, it is particularly necessary to accurately grasp the internal temperature. Therefore, in the partial oxidation reforming reaction step (POX step), which is the initial step of the start-up step, the fact that the POX reaction does not proceed in the first place unless the fuel gas is ignited in the single cell is used. By detecting that the temperature of the reformer 20 has risen to the temperature due to the POX reaction by the reformer temperature sensor 148 that detects the temperature, the ignition of the fuel gas in the single cell is detected. Furthermore, in such a period when it is difficult to determine ignition / misfire, by extending the execution period of the ignition promotion control, the ignition of the fuel gas in a specific single cell is surely promoted, and the risk of misfire is reduced. It is supposed to be.

  In the present embodiment, the control unit 110 extends the suppression period of the flow rate of the oxidant gas (air) that flows along with the fuel gas from one end side to the other end side of the plurality of single cells in the ignition promotion control in the alternative detection control mode. And the misfire in the some single cell is prevented by suppressing the fire transfer property from a specific single cell to another single cell (step S16 of FIG. 12).

  When an abnormality occurs in the combustion chamber temperature sensor 144 that directly detects ignition of fuel gas in a specific single cell, it is difficult to detect a sudden misfire in the single cell. Therefore, by suppressing the amount of oxidant gas (air) supplied to the plurality of single cells, in exchange for suppressing the fire transfer from a specific single cell to another single cell, It is intended to prevent misfire.

  In the present embodiment, the controller 110 increases the flow rate of air supplied to the reformer 20 in the ignition promotion control in the alternative detection control mode, and promotes the progress of the partial oxidation reforming reaction in the reformer 20. (Step S16 in FIG. 12). Thus, by increasing the flow rate of the air supplied to the reformer 20 in the ignition promotion control and promoting the progress of the partial oxidation reforming reaction in the reformer 20, it is possible to respond to the ignition of the fuel gas in the single cell. The temperature rise of the reformer 20 is promoted, and the ignition determination can be performed reliably.

  Further, as described above, in the present embodiment, the control unit 110 determines whether or not an abnormality has occurred in the temperature detection of the in-container temperature sensors (the power generation chamber temperature sensor 142, the combustion chamber temperature sensor 144, the reformer temperature sensor 148). Alternative control for controlling the operation state by detecting the open circuit voltage by the power state sensor (power state detection sensor 126) when it is determined that an abnormality has occurred in the temperature sensor in the container as a result of the determination. The mode (steps S14 and S17 in FIG. 12) is executed.

  In this case, the present inventors have found that the temperature inside the container and the open circuit voltage are in a correlation, and based on this knowledge, the operation state is controlled using the open circuit voltage. As described above, even when an abnormality occurs in the temperature sensor inside the container, an abnormality occurs in a part of the temperature sensor inside the container by executing the alternative control mode using the normal power state sensor. However, the operation is not immediately stopped, and the user is not burdened with being unusable.

  In the present embodiment, the control unit 110 is used in combination with the power state detection sensor 126 if at least one of a plurality of temperature sensors (power generation chamber temperature sensor 142, combustion chamber temperature sensor 144, reformer temperature sensor 148) is normal. Thus, the alternative control mode is executed, and if an abnormality has occurred in all of the plurality of temperature sensors, the alternative control mode is not executed.

  As described above, since the open circuit voltage and the temperature in the container have a correlation, it can be estimated that the container is in a certain temperature band. However, it is difficult to know the temperature inside the container accurately and to know the tendency of the temperature inside the container. Therefore, in this preferred embodiment, if at least one of the plurality of temperature sensors is normal, it can be used in combination with the power state sensor, so that it is possible to use both the temperature estimation by the open circuit voltage and the temperature detection by the normal temperature sensor, The accuracy of grasping the temperature in the container can be improved. Further, if all of the in-container temperature sensors are abnormal, the alternative control mode is not executed, so that it is possible to prevent problems other than the abnormality in the temperature sensor from being expanded.

  In the present embodiment, when the controller 110 determines that an abnormality has occurred in the power generation chamber temperature sensor 142, the controller 110 detects the open circuit voltage by the power state detection sensor 126 and the reformer by the reformer temperature sensor 148. Based on the temperature detection, the start-up process for transitioning the process from the partial oxidation reforming reaction process to the steam reforming reaction process through the autothermal reforming reaction process is controlled to execute the alternative control mode (FIG. 12). Step S17).

  In the present embodiment, since the power generation and the load following operation are not performed during the starting process, the correlation between the container temperature and the open circuit voltage is further increased. Therefore, by executing the alternative control mode using the open circuit voltage detection in combination with the reformer temperature detection in the startup process, the startup process can be advanced without stopping the operation of the solid oxide fuel cell 1. it can.

  In the present embodiment, the control unit 110 changes the transition temperature condition of the process transition in the startup process so as to be a high temperature in the alternative control mode (step S17 in FIG. 12).

  As described above, since the open circuit voltage and the temperature in the container have a correlation, it can be estimated that the container is in a certain temperature band. However, it is difficult to know the temperature inside the container accurately and to know the tendency of the temperature inside the container. Therefore, by changing the transition temperature condition of the process transition in the start-up process so as to be a high temperature in the alternative control mode, it is possible to suppress the process transition from being executed without increasing the temperature in the container, It is possible to prevent the expansion of problems other than abnormalities in the temperature sensor.

  In the present embodiment, the control unit 110 changes the transition temperature condition based on the reformer temperature detected by the reformer temperature sensor 148 so as to be a high temperature in the alternative control mode (step S17 in FIG. 12). .

  Thus, since the process transition can be performed by utilizing the fact that the temperature of the reformer 20 causing the endothermic reaction is sufficiently high, it is estimated that the temperature in the container is also increased to a necessary temperature. Thus, the transition temperature condition based on the reformer temperature detected by the reformer temperature sensor 148 is changed so as to be a high temperature in the alternative control mode. Therefore, it is possible to prevent the process transition from being performed without increasing the temperature in the container, and it is possible to prevent a problem other than an abnormality in the temperature sensor from being expanded.

  In the present embodiment, when the control unit 110 transitions from the startup process to the power generation process, the controller 110 extends the period for continuing the steam reforming reaction process after satisfying the transition temperature condition from the steam reforming reaction process to the power generation process. (Step S17 in FIG. 12).

  In the present embodiment, if the process proceeds to the power generation process without sufficiently increasing the temperature in the container, there is a possibility that a great number of problems may occur in parts other than the temperature sensor. Then, after satisfy | filling the transition temperature conditions from a steam reforming reaction process to an electric power generation process, the temperature in a container can be raised more reliably by extending the period which continues a steam reforming reaction process.

In the present embodiment, the control unit 110 changes the upper limit value of the power generation output so as to be a low output in the alternative control mode after shifting from the startup process to the power generation process (step S17 in FIG. 12).
As described above, when the process shifts to the power generation process while the alternative control mode is being executed, the upper limit value of the power generation output may be suppressed to minimize the influence due to the variation in the temperature in the container. it can. Moreover, the effect which raises the temperature in a container uniformly can also be show | played by suppressing electric power generation output.

  In the present embodiment, the control unit 110 reduces at least one of the fuel utilization rate and the power generation output in the power generation process in the alternative control mode (step S17 in FIG. 12).

  As described above, in the power generation process in the alternative control mode, by reducing at least one of the fuel utilization rate and the power generation output, the cause of the drop in the temperature in the container is eliminated, and problems other than abnormalities in the temperature sensor are expanded. Can be prevented.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

1: Solid electrolyte fuel cell 2: Fuel cell module 4: Auxiliary unit 6: Housing 8: Sealed space 10: Power generation chamber 12: Fuel cell assembly 12a: Upper surface 12b: Lower surface 12c: Long side surface 12d: Short side Side 14: Fuel cell stack 16: Fuel cell unit 18: Combustion chamber 20: Reformer 22: Heat exchanger 24: Water supply source 26: Pure water tank 28: Water flow rate adjustment unit 30: Fuel supply source 32: Gas shutoff valve 36: Desulfurizer 38: Fuel flow rate adjustment unit 40: Air supply source 42: Electromagnetic valve 44: Reforming air flow rate adjustment unit 45: Power generation air flow rate adjustment unit 46: First heater 48: Second heater 50 : Hot water production device 52: Control box 54: Inverter 56: Casing 58: Evaporative mixer 60: Reformed gas supply pipe 62: Water supply pipe 64: Fuel supply pipe 66: Nihold 66a: Lower end side 68: Fuel gas tank 70: Combustion gas pipe 72: Power generation air flow path 72a: Outlet port 74: Power generation air introduction pipe 74a: Inlet 76: Power generation air supply path 78: Air outlet 80: Combustion Gas discharge chamber 82: Combustion gas discharge pipe 83: Ignition device 84: Fuel cell 86: Inner electrode terminal 88: Fuel gas flow path 90: Inner electrode layer 90a: Upper part 90b: Outer peripheral surface 90c: Upper end surface 92: Outer electrode layer 94: Electrolyte layer 96: Sealing material 98: Fuel gas flow path 110: Control unit 112: Operating device 114: Display device 116: Notification device 120: Combustible gas detection sensor 122: Detection sensor 124: Hot water storage state detection sensor 126: Power state Detection sensor 128: power generation air flow rate detection sensor 130: reforming air flow rate sensor 132: fuel flow rate sensor 134: water flow rate Nsa 136: water level sensor 138: pressure sensor 140: exhaust gas temperature sensor 142: generating chamber temperature sensor 144: combustion chamber temperature sensor 146: exhaust gas chamber temperature sensor 148: reformer temperature sensor 150: outside air temperature sensor

Claims (8)

A solid oxide fuel cell device that generates power with fuel gas and oxidant gas,
A reformer that reforms a raw material gas containing hydrocarbons to generate fuel gas;
A cell assembly that has a plurality of single cells that are electrically connected and are erected so as to be along each other, and that generates power by flowing fuel gas and oxidant gas from one end side to the other end side of the plurality of single cells. When,
A container containing the reformer and the cell assembly;
A temperature sensor in the container for detecting the temperature in the container;
A power state sensor for detecting a power state of the cell assembly;
Control means for controlling the operating state of the solid oxide fuel cell device based on signals output from the temperature sensor in the container and the power state sensor;
With
The control means determines whether or not an abnormality has occurred in the temperature detection of the temperature sensor in the container, and when it is determined that an abnormality has occurred in the temperature sensor in the container as a result of the determination, A solid oxide fuel cell device that executes an alternative control mode in which an operating state is controlled by detecting an open circuit voltage by a state sensor. The in-container temperature sensor is composed of a plurality of temperature sensors,
The control means executes the alternative control mode by using in combination with the power state sensor if at least one of the plurality of temperature sensors is normal, and if an abnormality has occurred in all of the plurality of temperature sensors. 2. The solid oxide fuel cell device according to claim 1, wherein the alternative control mode is not executed. The in-container temperature sensor includes a power generation chamber temperature sensor that detects the temperature of the cell assembly, and a reformer temperature sensor that detects the temperature of the reformer,
When it is determined that an abnormality has occurred in the power generation chamber temperature sensor, the control means performs partial detection by detecting an open circuit voltage by the power state sensor and detecting a reformer temperature by the reformer temperature sensor. 2. The alternative control mode is executed by controlling a start-up process for transitioning from an oxidation reforming reaction process to an autothermal reforming reaction process to a steam reforming reaction process. 2. A solid oxide fuel cell device according to 1.   4. The solid oxide fuel cell device according to claim 3, wherein the control unit changes a transition temperature condition of the process transition in the start-up process so as to become a high temperature in the alternative control mode. 5.   The said control means changes the said transition temperature conditions based on the reformer temperature which the said reformer temperature sensor detects so that it may become high temperature in the said alternative control mode. Solid oxide fuel cell device.   The control means extends a period for continuing the steam reforming reaction step after satisfying a transition temperature condition from the steam reforming reaction step to the power generation step when shifting from the start-up step to the power generation step. The solid oxide fuel cell device according to claim 4, wherein:   5. The solid electrolyte according to claim 4, wherein the control unit changes the upper limit value of the power generation output so as to become a low output in the alternative control mode after transitioning from the start-up process to the power generation process. Fuel cell device.   2. The solid oxide fuel cell device according to claim 1, wherein in the power generation process in the alternative control mode, the control unit reduces at least one of a fuel utilization rate and a power generation output.

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