JP2011009104A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system for preventing a fuel cell from damaging in a process transiting from a cold state to a power generation state by starting it, in one using a long fuel cell.SOLUTION: The fuel cell system FCS makes a partial oxidation reformer RFP to be as a second reformer generate high-temperature fuel gas with the use of heat generation by partial oxidation reforming reaction to supply to the fuel cell CE at a starting operation, and supplies fuel gas generated mainly through steam reforming reaction by a steam reformer RFS to be as a first reformer to the fuel cell CE at a power generation operation. The fuel gas reformed at the partial oxidation reformer RFP is supplied from downward of the fuel cell CE, and oxidation gas with its temperature made to be raised at a catalyst combustor 10 to be as an air heating part is supplied from upward of the fuel cell CE.

Description

  The present invention relates to a fuel cell system including a solid electrolyte fuel cell.

  As such a fuel cell system, a solid electrolyte fuel cell is formed into a bottomed or bottomed cylindrical shape, etc., and a fuel gas containing hydrogen is passed inside or outside the fuel cell, and on the opposite side. Is known to cause a power generation reaction by passing an oxidizing gas such as air (see, for example, Patent Document 1 below). The fuel cell system described in the following Patent Document 1 is for preventing oxidation of the fuel cell at the start or stop of power generation.

JP 2005-293951 A

  By the way, a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell) configured by combining a plurality of solid electrolyte fuel cells has high power generation efficiency and uses less fuel gas. In some cases, the size may be increased. In that case, when each fuel cell is formed in a tubular shape, the fuel cell is elongated in the longitudinal direction of the tubular shape.

  In the solid electrolyte fuel cell system that has been increased in size in this way, there are various problems to be solved when starting from a completely stopped cold state. As one of the problems, there is a problem that the fuel cell is likely to be damaged when starting from a cold state. As a cause of the damage, a temperature difference between the fuel cells when a plurality of fuel cells are combined, or a temperature unevenness in the individual fuel cells is assumed. When fuel cells are structured in layers, if temperature unevenness occurs in which the upper and lower temperatures of the fuel cells deviate, delamination proceeds and eventually leads to damage of the fuel cells There is also. The fear of such damage is particularly significant during the transition of a long fuel cell from a cold state to a high temperature state where power can be generated.

  Specifically, as the fuel cell becomes longer, it becomes difficult to provide a temperature raising means such as a heater in the middle of the fuel cell, so a temperature raising means is provided near one or both ends to make a transition to a high temperature state. Can be considered. However, although the temperature in the vicinity where the temperature raising means is provided rises, it is difficult to raise the temperature of the part away from the temperature raising means in the same way. In particular, when the fuel cells are arranged so as to extend vertically along the vertical direction, the reaction gas (fuel gas and oxidizing gas) flows from the bottom to the top. Due to the property that heat rises, the temperature below the fuel cell tends to hardly rise. On the other hand, in the conventional technique described above, the fuel cell is preheated with a burner at the start of operation. The position of the burner with respect to the fuel cell is below the fuel cell (see FIG. 1 of Patent Document 1). When the burner is disposed below and the fuel cell is heated as described above, the radiant heat lowers the fuel cell. There is a risk that only the local high temperature state.

  The present invention has been made in view of such a problem, and the object of the present invention is to provide a fuel cell in the process of starting from a cold state and shifting to a power generation state even in a fuel cell system using a long fuel cell. An object of the present invention is to provide a fuel cell system that can prevent damage to the fuel cell.

  In order to solve the above-described problem, a fuel cell system according to the present invention includes a solid electrolyte fuel cell, and a fuel cell in which an operation state is shifted to a power generation operation in which power generation is performed in the fuel cell after the start-up operation is performed. A tubular fuel cell configured to perform a power generation reaction by supplying fuel gas to the anode side and supplying oxidizing gas to the cathode side, and a plurality of the fuel cells standing in the vertical direction; The first reformer that is mainly used in the power generation operation and reforms the gas to be reformed to generate fuel gas, and is mainly used in the start-up operation to reform the gas to be reformed. A second reformer that generates fuel gas, an air heating unit that supplies a heated oxidizing gas to the fuel cells, the first reformer, the second reformer, and the air Control the heating unit and start operation A control unit that shifts the operation to a power generation operation, and the control unit causes the second reformer to generate high-temperature fuel gas using heat generated by a partial oxidation reforming reaction in the start-up operation. The fuel cell is controlled to be supplied, and in the power generation operation, the first reformer is controlled to mainly perform a steam reforming reaction so as to supply the fuel cell generated fuel gas. The fuel gas reformed in the second reformer is supplied from below the fuel battery cell, and the oxidizing gas heated in the air heating unit is supplied from above the fuel battery cell. Each is configured as described above.

  The first reformer in the present invention performs reforming of a gas to be reformed mainly using water, that is, reforming by autothermal reforming reaction or steam reforming reaction. On the other hand, the second reformer generates high-temperature fuel gas using heat generated by the partial oxidation reforming reaction that is an exothermic reaction. The second reformer reforms the gas to be reformed by partial oxidation reforming reaction, or reforms the gas to be reformed by autothermal reforming reaction in connection with the partial oxidation reforming reaction. The heat generated by the partial oxidation reforming reaction is maintained and high-temperature fuel gas is generated. The fuel cell system of the present invention shifts from start-up operation to power generation operation, and in the start-up operation, the temperature of the fuel cell is increased to a temperature required for the power generation operation. Therefore, in the present invention, the fuel gas supplied from the second reformer is supplied to the fuel cell in the start-up operation, and the fuel gas supplied from the first reformer is supplied to the fuel cell in the power generation operation. Thus, the heat necessary for the start-up operation is given to the fuel cell. Furthermore, in the present invention, the fuel gas reformed in the second reformer is supplied from below the fuel cell, and the oxidizing gas heated in the air heating unit is supplied from above the fuel cell. Thus, the heated gas is supplied from above and below the fuel cell, and the fuel cell is heated by heat exchange with the heated gas. Thus, by heating the fuel cell with the heated gas supplied from above and below the fuel cell, a local temperature rise due to radiant heat can be suppressed, and the longitudinal direction of the fuel cell Temperature unevenness can be eliminated.

  Further, in the fuel cell system according to the present invention, the control unit is configured such that a difference between a temperature at a lower portion of the fuel cell and a temperature at a specific position above the lower portion of the fuel cell is within a first predetermined temperature difference. It is also preferable to execute temperature deviation relaxation control by controlling at least one of the second reformer and the air heating unit so as to be within the range.

  When the tubular fuel cells are arranged so as to extend vertically along the vertical direction as in the present invention, the region where the reaction off gas is burned is located above, and the heat rises. The temperature below the fuel cell tends to hardly increase. Therefore, in this aspect of the present invention, the temperature rises by performing temperature deviation relaxation control so that the difference between the temperature at the lower part of the fuel cell and the temperature at the specific position above it falls within the first predetermined temperature difference. The occurrence of extreme temperature unevenness can be prevented without leaving the lower part of the difficult fuel cell.

  Further, in the fuel cell system according to the present invention, the control unit is configured such that a difference between a temperature at the lower part of the fuel cell and a temperature at the middle part above the lower part of the fuel cell is within a second predetermined temperature difference. The second reformer and the air so that the difference between the temperature in the middle portion of the fuel cell and the temperature in the upper portion above the middle portion of the fuel cell falls within a third predetermined temperature difference. It is also preferable to execute the temperature deviation relaxation control by controlling at least one of the heating units.

  As described above, in the configuration of the present invention, the lower temperature of the fuel battery cell tends to hardly rise, so that the difference between the temperature at the lower part of the fuel battery cell and the temperature at a specific position above the lower part falls within a predetermined range. Temperature deviation relaxation control is performed. Further, in this preferred embodiment, the difference between the lower temperature and the middle temperature of the fuel cell falls within the second predetermined temperature difference, and the difference between the middle temperature and the upper temperature of the fuel battery cell falls within the second predetermined temperature difference. The second reformer or the air heating unit is controlled. By this control, the temperature difference toward the upper side and the temperature difference toward the lower side across the middle part of the fuel battery cell can be configured not to widen greatly, so that temperature unevenness of the entire fuel battery cell can be suppressed. .

  Further, in the fuel cell system according to the present invention, a lower temperature measuring unit that measures a temperature at the lower part of the fuel cell, a middle temperature measuring unit that measures a temperature at the middle part of the fuel cell, and the fuel cell An upper temperature measuring unit for measuring the temperature at the upper part of the fuel cell, the control unit is configured to measure the temperature of the fuel cell measured by the lower temperature measuring part, the middle temperature measuring part, and the upper temperature measuring part. It is also preferable to execute the temperature deviation relaxation control based on this.

  In this aspect, the lower temperature measuring unit, the middle temperature measuring unit, and the upper temperature measuring unit are provided, and the lower temperature, middle temperature, and upper temperature of the fuel cell can be measured by each, so that the control unit measures them. Based on the temperature, the temperature deviation relaxation control can be executed accurately so as to suppress the temperature variation of the entire fuel cell.

  In the fuel cell system according to the present invention, the fuel cell is configured to be supplied with oxidizing gas inside, and the control unit controls the air heating unit to control the air heating unit. It is also preferable to execute temperature deviation relaxation control.

  In this aspect, since the heated oxidizing gas is supplied to the inside of each fuel cell, the fuel gas reformed in the second reformer is supplied to the outside of each fuel cell. Will be. Since the control unit performs temperature deviation mitigation control by controlling the air heating unit, the temperature unevenness of the fuel cell is directly eliminated by adjusting the temperature of the gas supplied to each fuel cell. Thus, the temperature deviation of the fuel cell can be reliably reduced. Further, since the temperature deviation relaxation control is performed only by controlling the air heating unit, it is not necessary to control the reforming reaction in the second reformer, and the temperature deviation relaxation control can be executed easily and efficiently. On the other hand, if temperature deviation mitigation control is performed by controlling the second reformer, temperature unevenness of the fuel cells is eliminated from the outside of each fuel cell, and the fuel gas is transferred to portions other than the fuel cell. Will also come into contact with each other, resulting in temperature unevenness among the plurality of fuel cells. Therefore, in this aspect, the temperature of the oxidizing gas introduced from above into the inside of the fuel cell is adjusted by the control of the air heating unit, and the temperature unevenness of the fuel cell is eliminated efficiently and reliably.

  In the fuel cell system according to the present invention, it is also preferable that the control unit controls the air heating unit so as to reduce the amount of heat of the oxidizing gas supplied to the inside of the fuel cell. As described above, in the present invention, the tubular fuel cells are arranged so as to extend vertically along the vertical direction, so that the region where the reaction off gas is burned is located above, and the heat rises. Due to certain properties, the temperature below the fuel cell tends to hardly rise. Therefore, in this aspect, it is not necessary to control the reforming reaction in the second reformer by suppressing the temperature rise above the fuel cell by reducing the amount of heat of the oxidizing gas supplied to the inside of the fuel cell. The temperature unevenness of the fuel cell can be easily and effectively suppressed.

  In the fuel cell system according to the present invention, it is also preferable that the control unit controls the air heating unit so as to reduce the amount of heat input to the oxidizing gas supplied to the inside of the fuel cell. In this aspect, since the amount of heat of the oxidizing gas is reduced by reducing the amount of heat input to the oxidizing gas, the energy for supplying heat to the oxidizing gas can be reduced, contributing to energy saving and the fuel cell. Temperature unevenness can be suppressed.

  In the fuel cell system according to the present invention, the air heating unit has a combustion catalyst for further raising the temperature of the oxidizing gas preheated by the heater by the combustion of the fuel, and reduces the fuel preferentially. It is also preferable to reduce the amount of heat input to the oxidizing gas. In this aspect, since the amount of heat input to the oxidizing gas is reduced by preferentially reducing the fuel, the temperature unevenness of the fuel cell can be effectively suppressed without consuming unnecessary fuel.

  According to the present invention, even in a fuel cell system using a long fuel cell, a fuel cell system capable of preventing damage to the fuel cell in the process of starting from a cold state and making a transition to a power generation state is provided. be able to.

1 is a schematic configuration diagram illustrating an overall configuration of a fuel cell system according to an embodiment of the present invention. It is a block diagram which shows the control structure of the fuel cell system shown in FIG. It is a block diagram which shows the detailed structure centering on the fuel cell module of the fuel cell system shown in FIG. It is a figure for demonstrating the starting operation of the fuel cell system shown in FIGS. It is a flowchart for demonstrating the temperature deviation relaxation control of the fuel cell system shown in FIGS. It is a figure which shows the example of the temperature distribution of a fuel cell in order to demonstrate the temperature deviation relaxation control shown in FIG. It is a figure which shows the example of the temperature distribution of a fuel cell in order to demonstrate the temperature deviation relaxation control shown in FIG. It is a figure which shows the example of the temperature distribution of a fuel cell in order to demonstrate the temperature deviation relaxation control shown in FIG. It is a figure which shows the example of the temperature distribution of a fuel cell in order to demonstrate the temperature deviation relaxation control shown in FIG.

  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 components are denoted by the same reference numerals as much as possible in the drawings, and redundant descriptions are omitted.

  A fuel cell system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an overall configuration of a fuel cell system FCS as an embodiment. As shown in FIG. 1, the fuel cell system FCS includes a fuel cell module FCM, an auxiliary device unit ADU, a water storage tank WP2, and a hot water production apparatus HW.

  First, the fuel cell module FCM will be described. The fuel cell module FCM includes a fuel cell FC, a reformer RF, a control box CB, a carbon monoxide detector COD, and a combustible gas detector GD1. The fuel cell FC is a solid oxide fuel cell (SOFC), and includes a power generation chamber FC1 and a combustion chamber FC2.

  A plurality of fuel cells CE are arranged in the power generation chamber FC1. The fuel cell CE is provided with a fuel electrode (anode) and an air electrode (cathode) with an electrolyte interposed therebetween. The fuel cell CE passes fuel gas to the fuel electrode side and air as an oxidizing gas to the air electrode side. It is configured to generate a power generation reaction by passing through. Since the fuel cell FC of the present embodiment is a solid electrolyte fuel cell (SOFC), the material constituting the electrolyte is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, and rare earth elements. An oxygen ion conductive oxide such as ceria doped with at least one selected from lanthanum gallate doped with at least one selected from Sr and Mg is used.

  As a material constituting the fuel electrode, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, Ni and at least one selected from rare earth elements are doped. A material such as a mixture of ceria, a mixture of Ni and lanthanum gallate doped with at least one selected from Sr, Mg, Co, Fe, and Cu is used. Examples of the material constituting the air electrode include 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, A material such as lanthanum cobaltite or silver doped with at least one selected from Cu is used. But the material which comprises an electrolyte, a fuel electrode, and an air electrode is not restricted to these.

  The electricity generated in the power generation chamber FC1 is taken out and used as generated power by the power extraction line EP1. The combustion chamber FC2 is a portion where the remaining fuel gas used for the power generation reaction is burned by the fuel cell CE arranged in the power generation chamber FC1. The exhaust gas generated as a result of the combustion of the fuel gas in the combustion chamber FC2 is supplied to the hot water production apparatus HW after heat exchange with the reformer RF. The exhaust gas supplied to the hot water production apparatus HW is further subjected to heat exchange, the temperature of the tap water is raised to warm water, and then discharged to the outside.

  The reformer RF is a portion that reforms the gas to be reformed into fuel gas and supplies it to the power generation chamber FC1 of the fuel cell FC. As reforming modes of the gas to be reformed, there are partial oxidation reforming reaction (POX: Partial Oxidation Reforming), auto thermal reforming reaction (ATR: Auto Thermal Reforming), steam reforming reaction (SR: Steam Reforming), It is selectively executed according to the driving situation. The reformer RF includes a reforming unit RF1 and an evaporation unit RF2.

  The evaporating unit RF2 is a part that evaporates pure water supplied from the auxiliary unit ADU side into water vapor and supplies the water vapor to the reforming unit RF1. The reforming unit RF1 is a part that reforms the gas to be reformed using the gas to be reformed supplied from the auxiliary unit ADU side, air, and water vapor supplied from the evaporation unit RF2 to form a fuel gas. A reforming catalyst is enclosed in the reforming unit RF1. As the reforming catalyst, a catalyst in which nickel is applied to the surface of the alumina sphere and a catalyst in which ruthenium is applied to the surface of the alumina sphere are appropriately used. In the present embodiment, these reforming catalysts are spheres.

  The control box CB houses the fuel cell system control unit therein, and is provided with an operation device, a display device, and a notification device. The fuel cell system control unit, operation device, display device, and notification device will be described later.

  The carbon monoxide detector COD is a sensor for detecting whether incomplete combustion of the remaining fuel gas has occurred in the combustion chamber FC2 of the fuel cell module FCM and carbon monoxide is not generated in the fuel cell module FCM. It is. The combustible gas detector GD1 is a sensor for detecting whether the remaining fuel gas remains in the combustion chamber FC2 of the fuel cell module FCM and so-called raw gas is not generated in the fuel cell module FCM.

  Subsequently, the auxiliary unit ADU will be described. The auxiliary device unit ADU is a unit including auxiliary devices for supplying water, reformed gas, and air to the fuel cell module FCM. The auxiliary unit ADU includes flow rate adjustment units AP1a and AP1b and an electromagnetic valve AP2 including air blowers and flow rate adjustment valves as an air supply unit, and a flow rate adjustment unit FP1 including a fuel pump and a flow rate adjustment valve as a fuel supply unit, A desulfurizer FP2, a gas cutoff valve FP4, and a gas cutoff valve FP5, a flow rate adjustment unit WP1 including a water pump and a flow rate adjustment valve as a water supply unit, and a combustible gas detector GD2 are provided.

  Air supplied from an external air supply source is not supplied to the flow rate adjustment units AP1a and AP1b when the electromagnetic valve AP2 is closed, and is supplied to the flow rate adjustment units AP1a and AP1b when the electromagnetic valve AP2 is open. The air whose flow rate is adjusted by the flow rate adjusting unit AP1a is heated as the reforming air by the heater AH1 and supplied to the mixing portion MV with the reformed gas. The air whose flow rate is adjusted by the flow rate adjusting unit AP1b is heated as the power generation air by the heater AH2 (air heating unit) and supplied to the power generation chamber FC1 of the fuel cell module FCM. The power generation air supplied to the power generation chamber FC1 is supplied to the air electrode of the fuel cell CE.

  The inflow of city gas supplied from an external fuel supply source is controlled by a gas shut-off valve FP4 and a gas shut-off valve FP5 which are double solenoid valves. If any of the gas cutoff valves FP4 and FP5 is open, the city gas is supplied to the desulfurizer FP2, and if any of the gas cutoff valves FP4 and FP5 is closed, the city gas is shut off. The city gas supplied to the desulfurizer FP2 is removed from the sulfur component to become a reformed gas, and is supplied to the flow rate adjustment unit FP1. The to-be-reformed gas whose flow rate has been adjusted by the flow rate adjusting unit FP1 is supplied to the mixing unit MV with the reforming air. The gas to be reformed and the reforming air mixed in the mixing unit MV are supplied to the reformer RF of the fuel cell module FCM.

  Tap water supplied from an external water supply source is made pure water and then stored in the water storage tank WP2. The pure water stored in the water storage tank WP2 is supplied to the reformer RF of the fuel cell module FCM after the flow rate is adjusted by the flow rate adjustment unit WP1.

  The combustible gas detector GD2 is a system that serves as a fuel supply unit. In the gas cutoff valve FP5, the gas cutoff valve FP4, the desulfurizer FP2, and the flow rate adjustment unit FP1, gas leakage occurs and so-called raw gas is not released to the outside. It is a sensor for detecting.

  Next, a control configuration of the fuel cell system FCS of the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a control configuration of the fuel cell system FCS. As shown in FIG. 2, the fuel cell system FCS supplies a fuel cell module FCM, an air supply unit AP that supplies air to the fuel cell module FCM, and a reformed gas that becomes fuel gas to the fuel cell module FCM. A fuel supply unit FP, a water supply unit WP that supplies water to the fuel cell module FCM, and a power extraction unit EP that extracts power from the fuel cell module FCM are provided. The air supply unit AP, the fuel supply unit FP, the water supply unit WP, and the power extraction unit EP are housed in the auxiliary unit ADU.

  The fuel cell module FCM, the air supply unit AP, the fuel supply unit FP, the water supply unit WP, and the power extraction unit EP are controlled based on a control signal output from the fuel cell system control unit CS. The fuel cell system control unit SC includes a CPU, a memory such as a ROM and a RAM, and an interface for sending and receiving control signals and sensor signals. An operating device CS1, a display device CS2, and a notification device CS3 are attached to the fuel cell system controller SC.

  The operation instruction signal input from the operation device CS1 is output to the fuel cell system control unit CS, and the fuel cell system control unit CS controls the fuel cell module FCM and the like based on the operation instruction signal. Information controlled by the fuel cell system control unit CS and predetermined warning information are output to the display device CS2 and the notification device CS3. Specific hardware configurations of the operation device CS1, the display device CS2, and the notification device CS3 are not particularly limited, and an optimal hardware configuration is selected according to a required function. As an example, hardware such as a keyboard, a mouse, and a touch panel is used as the operating device CS1. As the display device CS2, display system hardware such as a CRT display or a liquid crystal display is used. As the notification device CS3, hardware such as a speaker and a lighting device is used. The fuel cell system controller CS is housed in a control box CB. In addition, the operation device CS1, the display device CS2, and the notification device CS3 are housed in a box (not shown).

  Sensor signals are output to the fuel cell system controller CS from sensors provided at various locations in the fuel cell system FCS. The sensors that output signals to the fuel cell system controller CS include a reformer temperature sensor DS1, a stack temperature sensor DS2, an exhaust temperature sensor DS3, a reformer pressure sensor DS4, a water level sensor DS5, a water flow rate sensor DS6, fuel A flow rate sensor DS7, a reforming air flow rate sensor DS8, a power generation air flow rate sensor DS9, a power state detection unit DS10, a hot water storage state detection sensor DS11, a carbon monoxide detection sensor DS12, and a combustible gas detection sensor DS13 are provided.

  The reformer temperature sensor DS1 is a sensor for measuring the temperature of the reformer RF. In the present embodiment, two reformer temperature sensors DS1 are provided. The stack temperature sensor DS2 is a sensor for measuring the temperature of the fuel cell CE arranged in the power generation chamber FC1, and is arranged in the vicinity of the fuel cell stack composed of a plurality of fuel cells CE. The exhaust temperature sensor DS3 is a sensor for measuring the temperature of the exhaust gas discharged from the combustion chamber FC2, and is disposed in a path from the combustion chamber FC2 through the vicinity of the reformer RF to the hot water production apparatus HW. Yes. The reformer pressure sensor DS4 is a sensor for measuring the pressure in the reformer RF. Here, the pressure in the reformer RF is measured by a sensor, but the pressure in the portion where the fuel and water are mixed may be detected in the previous stage of the reformer RF.

  The water level sensor DS5 is a sensor for measuring the water level of the water storage tank WP2. In the present embodiment, four water level sensors DS5 are provided. The water flow rate sensor DS6 is a sensor for measuring the flow rate of pure water supplied from the auxiliary unit ADU to the fuel cell module FCM. The fuel flow rate sensor DS7 is a sensor for measuring the flow rate of the reformed gas supplied from the auxiliary unit ADU to the fuel cell module FCM. The reforming air flow rate sensor DS8 is a sensor for measuring the flow rate of the reforming air supplied from the auxiliary unit ADU to the reformer RF of the fuel cell module FCM. The power generation air flow rate sensor DS9 is a sensor for measuring the flow rate of power generation air supplied from the auxiliary unit ADU to the fuel cell module FCM.

  The power state detection unit DS10 is an assembly of sensing means, and is a part that detects the state of generated power extracted from the fuel cell module FCM. The hot water storage state detection sensor DS11 is an assembly of sensing means, and is a part that detects the hot water storage state of the hot water production apparatus HW.

  The carbon monoxide detection sensor DS12 is a sensor provided in the carbon monoxide detector COD, and is a sensor that detects leakage of carbon monoxide into the housing in the fuel cell module FCM. The combustible gas detection sensor DS13 is a sensor provided in the combustible gas detectors GD1 and GD2, and is a sensor that detects the leakage of combustible gas in the fuel cell module FCM and the auxiliary unit ADU.

  Next, a detailed configuration of the fuel cell module FCM constituting the fuel cell system FCS of the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating a control configuration of the fuel cell system FCS.

  As shown in FIG. 3, the fuel cell module FCM includes a power generation chamber FC1, a dispersion chamber DB, a combustion chamber FC2, a steam reformer RFS (first reformer), and a partial oxidation reformer RFP (first 2 reformer). The power generation chamber FC1, the dispersion chamber DB, the combustion chamber FC2, and the steam reformer RFS are accommodated in the same container C, and the partial oxidation reformer RFP is disposed outside the container C.

  The dispersion chamber DB is disposed below the power generation chamber FC1. The dispersion chamber DB is for dispersing the fuel gas reformed by the steam reformer RFS or the partial oxidation reformer RFP, and for uniformly supplying the fuel gas into the power generation chamber FC1, and its upper wall. Are formed with a plurality of holes (not shown) through which fuel gas is supplied into the power generation chamber FC1. In addition, an introduction hole (not shown) for introducing the fuel gas supplied from the steam reformer RFS or the partial oxidation reformer RFP into the dispersion chamber DB is formed through the bottom surface of the dispersion chamber DB. Yes. As a result, the fuel gas introduced from the bottom surface side (lower side) of the dispersion chamber DB is dispersed here and introduced into the power generation chamber FC1 from the bottom surface side (lower side) of the power generation chamber FC1 to enter the power generation chamber FC1. It is supplied to the fuel electrode of the standing fuel cell CE.

  In the case of the embodiment shown in FIG. 3, the reformer RF is divided into a steam reformer RFS and a partial oxidation reformer RFP. First, the configuration of the steam reformer RFS will be described. The steam reformer RFS includes an evaporation unit RFS1, a preheating unit RFS2, and a reforming unit RFS3.

  The reforming unit RFS3 is disposed in the upper part of the combustion chamber FC2. A preheating unit RFS2 is disposed above the reforming unit RFS3, and an evaporation unit RFS1 is disposed above the preheating unit RFS2. The evaporating unit RFS1 is supplied with pure water from the auxiliary unit ADU side, evaporates the pure water to form water vapor, and sends the water vapor to the preheating unit RFS2. The preheating unit RFS2 is supplied with water vapor from the evaporation unit RFS1 and is supplied with city gas as a reformed gas from the auxiliary unit ADU side. In the preheating unit RFS2, water vapor and city gas as the reformed gas are mixed, and the mixed gas is sent to the reforming unit RFS3. The reforming unit RFS3 is supplied with water vapor and a gas to be reformed from the preheating unit RFS2, reforms the gas to be reformed by the action of the reforming catalyst to be a fuel gas, and sends it to the dispersion chamber DB. As described above, the steam reformer RFS (reformer RFS3) is disposed in the container C and is disposed above the combustion chamber FC2 disposed in the same container C. The steam reforming reaction, which is an endothermic reaction, can be efficiently performed using the heat generated in the combustion chamber FC2.

  The partial oxidation reformer RFP is disposed on the lower portion of the outer surface of the container C via a heat insulating material. The partial oxidation reformer RFP is configured to be supplied with a gas to be reformed, air, and pure water. The fuel gas reformed by the partial oxidation reformer RFP is supplied to the dispersion chamber DB from the aforementioned introduction hole (not shown) formed on the bottom surface of the dispersion chamber DB. A pipe that allows the fuel gas to flow through the partial oxidation reformer RFP and the dispersion chamber DB is wrapped with a heat insulating material HI. The partial oxidation reformer RFP performs partial oxidation reforming or reforming using water for the gas to be reformed in the startup mode and the shutdown mode, but does not require water. During the reaction (POX), the fuel cell system control unit CS performs control so that the pure water is not supplied to the partial oxidation reformer RFP.

  In order to measure the temperature of the fuel cell CE arranged in the power generation chamber FC1, the stack temperature sensor DS2a (upper temperature measuring unit), the stack temperature sensor DS2b (middle temperature measuring unit), and the stack temperature sensor DS2c (lower temperature measuring unit) Is arranged. The stack temperature sensor DS2a is disposed above the stack temperature sensor DS2b in order to measure the upper temperature of the fuel cell CE. The stack temperature sensor DS2c is disposed below the stack temperature sensor DS2b in order to measure the lower temperature of the fuel cell CE. The stack temperature sensor DS2b is disposed between the stack temperature sensor DS2a and the stack temperature sensor DS2c and near the center of the fuel cell CE in order to measure the middle temperature of the fuel cell CE.

  A catalytic combustor 10 and an air header 15 are provided to supply high-temperature oxidizing gas to each fuel cell CE. The catalyst combustor 10 is filled with a catalyst, and is configured to be ignited and combusted when an ignition condition exceeding a predetermined SV (space velocity) value is satisfied by supplying air and fuel gas. Yes. The catalyst combustor 10 is configured to be supplied with air that is sent from the flow rate adjustment unit AP1b and heated by the heater AH2. Further, the catalytic combustor 10 is configured to be supplied with city gas directly. The air further heated by the catalytic combustor 10 is supplied to the air header 15. The air header 15 is configured to distribute and supply air to each of the plurality of fuel cells CE.

  Next, switching of various reforming reactions in the start-up operation and power generation operation of the fuel cell system FCS will be described with reference to FIG. FIG. 4 is a graph showing the temperature and flow rate of each part when the fuel cell system FCS is started. 4 (a) shows the flow rate of air supplied to the air electrode (cathode) side of the fuel cell CE, FIG. 4 (b) shows the gas flow rate and the like related to the partial oxidation reformer RFP, FIG. 4C shows the gas flow rate and the like related to the steam reformer RFS.

  Specifically, FIG. 4A shows the flow rate of air supplied to the catalytic combustor 10 (detected by the power generation air flow rate sensor DS9) 20 and the flow rate of city gas supplied directly to the catalytic combustor 10. (Detected by a city gas flow sensor not shown) 21, the temperature of the heater AH2 (calculated by the specification and applied voltage of the heater AH2) 22, the outlet temperature of the catalyst combustor 10 (detected by a temperature sensor not shown) 23, combustion The temperature (detected by a temperature sensor not shown) 24 of the chamber FC2 is shown. The horizontal axis represents time, the left vertical axis represents temperature (° C.) and air flow rate (NLM), and the right vertical axis represents city gas flow rate (NLM).

  4B shows the flow rate of air supplied to the partial oxidation reformer RFP (detected by the reforming air flow rate sensor DS8) 25 and the flow rate of city gas supplied to the partial oxidation reformer RFP ( 26 (detected by the fuel flow sensor DS7) 26, the flow rate of water supplied to the partial oxidation reformer RFP (detected by the water flow sensor DS6) 27, and the temperature of the heater AH1 (calculated by the specification and applied voltage of the heater AH1) 28 And a reaction tube inlet temperature (detected by the reformer temperature sensor DS1) 29 of the partial oxidation reformer RFP and a reaction tube outlet temperature (detected by the reformer temperature sensor DS1) 30 of the partial oxidation reformer RFP. Show. The horizontal axis indicates time, the left vertical axis indicates temperature (° C.), and the right vertical axis indicates air flow rate, city gas flow rate (NLM), and water flow rate (mlM: ml per minute). .

  FIG. 4C shows the temperature of the fuel cell CE (detected by the stack temperature sensor DS2) 31, the flow rate of the city gas supplied to the steam reformer RFS (detected by the fuel flow rate sensor DS7) 32, the steam A flow rate of water supplied to the reformer RFS (detected by the water flow rate sensor DS6) 33 and a current (detected by the power state detection unit DS10) 34 taken out from the power extraction line EP1 are shown. The horizontal axis represents time, the left vertical axis represents temperature (° C.), and the right vertical axis represents fuel gas flow rate (NLM) and water flow rate (mlM).

  First, air supply to the cathode side is started simultaneously with the start ((a) of FIG. 4). The air flow rate 20 is 400 NLM. At the same time as the start, the supply of air to the partial oxidation reformer RFP is started ((b) of FIG. 4). The air flow rate 25 is 20 NLM. After confirming that air to the cathode side has started to flow, the heater AH2 is turned on (time t1 in FIG. 4A). Energization of the heater AH2 is started from time t1, and control is performed so that the temperature 22 of the heater AH2 becomes 750 ° C. by time t2. On the other hand, it is confirmed that the air to the partial oxidation reformer RFP has started to flow, and the heater AH1 is turned on (time t1 in FIG. 4B). Energization to the heater AH1 is started from time t1, and control is performed so that the temperature 28 of the heater AH1 becomes 600 ° C. by time t2.

  Since the air heated by the heater AH2 is supplied on the cathode side, the outlet temperature 23 of the catalytic combustor 10 and the temperature 24 of the combustion chamber FC2 rise. When the outlet temperature 23 of the catalytic combustor 10 reaches 400 ° C., an ignition condition is set such that the air supply flow rate 20 is reduced to 150 NLM and the heat shock to the fuel cell CE is suppressed as much as possible ((a) of FIG. 4). From time t3 to time t4). Thereafter, the supply of city gas directly to the catalytic combustor 10 is started at time t4. The flow rate 21 of this city gas is 0.5 NLM. Thereafter, the supply amount of air and city gas is gradually increased from time t5 so as to prevent heat shock to the fuel cell CE. The air supply flow rate 20 is returned to 400 NLM, and the city gas supply flow rate 21 is increased to 2 NLM. As a result, the outlet temperature 23 of the catalytic combustor 10 becomes 700 ° C. or higher and 900 ° C. or lower, and the fuel cell CE is heated from above. The temperature difference between the upper and lower sides of the fuel cell CE is controlled to be within 150 ° C., and the difference between the temperature of the combustion chamber FC2 and the temperature of the upper portion of the fuel cell CE is controlled to be within 150 ° C.

  As shown in FIG. 4B, in the partial oxidation reformer RFP, the air heated by the heater AH1 is supplied, so that the reaction tube inlet temperature 29 and the reaction tube outlet temperature of the partial oxidation reformer RFP are supplied. 30 rises. On condition that the reaction tube inlet temperature 29 of the partial oxidation reformer RFP is 400 ° C. or more, the air supply flow rate 25 is reduced from time t4 to time t5, and is reduced to about 5 NLM, and the fuel cell CE is supplied to the fuel cell CE. Set ignition conditions to minimize heat shock. The city gas as the reformed gas is supplied to the partial oxidation reformer RFP (time t6 in FIG. 4B). This supply flow rate 26 is 1 NLM. Furthermore, water is also supplied from time t7. The supply flow rate 27 is 1 mlM.

  As described above, in the partial oxidation reformer RFP in which the predetermined temperature is secured by supplying the city gas, air, and water as the reformed gas, the partial oxidation reforming reaction POX and the autothermal reforming reaction ATR are performed. It is assumed that

The partial oxidation reforming reaction POX is a reforming reaction performed by supplying the reformed gas and air to the partial oxidation reformer RFP, and the reaction shown in the chemical reaction formula (1) proceeds.
_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)
Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is high, and is a suitable reforming reaction at the beginning of starting the fuel cell system FCS. However, since the partial oxidation reforming reaction POX has a theoretically low hydrogen yield and it is difficult to control the exothermic reaction, the partial oxidation reforming reaction POX is preferably used only at the beginning of startup when the fuel cell module FCM requires heat supply. It is a quality reaction.

The autothermal reforming reaction ATR is an intermediate reforming reaction between the partial oxidation reforming reaction POX and the steam reforming reaction SR, and supplies the reformed gas, air, and steam to the partial oxidation reformer RFP. The reaction shown in the chemical reaction formula (2) proceeds.
_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (2)
In the autothermal reforming reaction ATR, the hydrogen yield is intermediate between the partial oxidation reforming reaction POX and the steam reforming reaction SR, and it is easy to balance the reaction heat, and the partial oxidation reforming reaction POX and the steam reforming reaction SR. It is a suitable reforming reaction as a reaction connecting In the case of the present embodiment, a small amount of water is supplied and the autothermal reforming reaction ATR1 closer to the partial oxidation reforming reaction POX is performed first, and after the temperature rises, the water is increased to supply the steam reforming reaction SR. A closer autothermal reforming reaction ATR2 is performed later.

  As shown in FIG. 4B, from the time t6 to the time t7 when the partial oxidation reforming reaction POX seems to be proceeding dominantly, the reaction tube inlet temperature 29 and the reaction tube of the partial oxidation reformer RFP. The outlet temperature 30 is rising rapidly. Thereafter, from time t8 to time t9, air, city gas, and water are gradually increased to shift from autothermal reforming reaction ATR1 close to partial oxidation reforming reaction POX to autothermal reforming reaction ATR2 closer to steam reforming reaction. Thus, the reaction tube inlet temperature 29 and the reaction tube outlet temperature 30 of the partial oxidation reformer RFP are gradually increased while maintaining a temperature balance. At time t9, the air supply flow rate 25 is 20 NLM, the city gas supply flow rate 26 is 4 NLM, and the water supply flow rate 27 is 4 mlM.

  As described above, air as the oxidizing gas heated by the catalytic combustor 10 is supplied from above the fuel cell CE, and the temperature is raised by the partial oxidation reformer RFP from below the fuel cell CE. The supplied fuel gas is supplied, and the temperature of the fuel cell CE gradually rises in a balanced manner ((c) in FIG. 4). Water supply to the steam reformer RFS is started from time t10 when the temperature of the evaporation unit RF2 exceeds a predetermined temperature. The supply flow rate of water at this time is 1 to 3 mlM. Thereafter, the supply of the city gas as the reformed gas to the steam reformer RFS is started from the time t11 when the temperature of the steam reformer RFS exceeds the predetermined temperature. At this time, the supply flow rate of the city gas is 1 NLM. After time t11, the supply flow rates of water and city gas are gradually increased. In this steam reformer RFS, it is assumed that the steam reforming reaction SR is proceeding predominantly.

The steam reforming reaction SR is a reforming reaction performed by supplying the gas to be reformed and steam to the steam reformer RFS, and the reaction shown in the chemical reaction formula (3) proceeds.
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (3)
The steam reforming reaction SR has the highest hydrogen yield and is a highly efficient reaction. However, since the steam reforming reaction SR is an endothermic reaction, it requires a heat source, and is a suitable reforming reaction at a stage where the temperature has risen to some extent from the start of the fuel cell system FCS.

  From time t12 after preparing for power generation in this way, power extraction is started and power generation operation is started. In response to this, at time t13 after time t12, direct city gas supply to the catalytic combustor 10 is stopped ((a) of FIG. 4). Thereafter, the heater AH2 is also stopped (time t16 in FIG. 4A).

  From the time t14 after the time t13, the energization amount of the heater AH1 that raises the temperature of the air to the partial oxidation reformer RFP is gradually reduced and stopped at the time t15. From the time t15, the supply of air, city gas, and water to the partial oxidation reformer RFP is also reduced. At time t16 after time t15, the supply flow rate of air, city gas, and water is maintained at a predetermined value, and then the supply of air is stopped at time t17. Thereafter, the city gas and water are continuously supplied until time t18, and an endothermic reaction due to the steam reforming reaction SR is caused to lower the temperature. After the supply of city gas is stopped at time t18 and the inside of the reaction tube of the partial oxidation reformer RFP is purged with steam, the supply of water is stopped at time t19.

  In the embodiment shown in FIG. 4, the amount of current supplied to the heater AH1 is reduced and the heat generation of the heater AH1 is gradually reduced, and then the air supply flow rate is reduced. It is also preferable to control to increase the flow rate. By gradually reducing the heat generated by the heater AH1, it is possible to prevent a sudden change in the temperature of the air supplied to the partial oxidation reformer RFP, and consequently a sudden change in the temperature of the fuel gas supplied from the partial oxidation reformer RFP. Can be prevented. Furthermore, by increasing the amount of air supplied to the partial oxidation reformer RFP in accordance with the suppression of heat generation by the heater AH1, it is possible to prevent a sudden change in the amount of heat input.

  In addition, after the start of the power generation operation (after time t12 in the embodiment shown in FIG. 4), the amount of hydrogen contained in the fuel gas supplied from the steam reformer RFS and the fuel gas supplied from the partial oxidation reformer RFP The supply of fuel gas by the partial oxidation reformer RFP is gradually decreased so that the total amount with the amount of hydrogen contained is substantially constant. Maintaining the total amount of hydrogen contained in the fuel gas supplied from the steam reformer RFS and the partial oxidation reformer RFP when gradually reducing the supply of fuel gas from the partial oxidation reformer RFP after the start of power generation operation By doing so, it is possible to reduce the influence on the power generation operation by continuing the operation of the partial oxidation reformer RFP until after the start of the power generation operation.

  In the present embodiment, after the start of the power generation operation, the temperature rise by the catalytic combustor 10 that is an air heating medium is gradually decreased so that the temperature of the oxidizing gas supplied to the fuel cell CE becomes substantially constant. ing. When shifting to the power generation operation, the fuel gas reformed by the steam reformer RFS is also supplied, and the amount of combustion of the remaining fuel gas and the remaining oxidizing gas above the fuel cell CE increases, resulting in the fuel cell. The upper part of CE tends to become higher temperature. Therefore, in this aspect, the temperature difference in the vertical direction of the fuel cell CE is reduced by lowering the temperature rise of the oxidizing gas by the catalytic combustor 10 and making the temperature of the oxidizing gas supplied to the fuel cell CE substantially constant. Can be suppressed.

  In the present embodiment, in order to measure the temperature of the fuel cell CE arranged in the power generation chamber FC1, the stack temperature sensor DS2a (upper temperature measurement unit) that measures the upper temperature of the fuel cell CE, the middle part of the fuel cell CE Since the stack temperature sensor DS2b (middle temperature measuring unit) for measuring the temperature and the stack temperature sensor DS2c (lower temperature measuring unit) for measuring the lower temperature of the fuel cell CE are arranged, the temperature balance of the fuel cell CE is adjusted. Driving at a higher level is possible. Next, details of temperature deviation relaxation control for controlling the temperature balance of the fuel cell CE to be maintained at a higher level will be described with reference to FIG. FIG. 5 is a flowchart for explaining the temperature deviation relaxation control.

  In step S01, it is determined whether activation control is being performed. “Starting control is being performed” indicates a case where the starting operation is before the power generation operation. For example, in the operation example shown in FIG. 4, the time is between 0 and t12. If the activation control is not in progress, the process returns. If the activation control is in progress, the process proceeds to step S02.

  In step S02, the temperature of the fuel cell CE is measured. The upper temperature T1 of the fuel cell CE is measured by the stack temperature sensor DS2a, the middle temperature T2 of the fuel cell CE is measured by the stack temperature sensor DS2b, and the lower temperature T3 of the fuel cell CE is measured by the stack temperature sensor DS2c. .

  In step S03 following step S02, it is determined whether the air heating operation is being performed. The air heating operation is in a stage before combustion starts in the catalytic combustor 10. For example, in the operation example shown in FIG. 4, the time is from time 0 to time t 4. If the air heating operation is not being performed, the process returns. If the air heating operation is being performed, the process proceeds to step S04.

  In step S04, it is determined whether the partial oxidation reformer RFP has been heated to the operation start temperature. For example, in the operation example as shown in FIG. 4, the determination is made based on whether or not the reaction tube inlet temperature of the partial oxidation reformer RFP is 400 ° C. or higher. If the partial oxidation reformer RFP has not been heated to the operation start temperature, the process returns. If the partial oxidation reformer RFP has been heated to the operation start temperature, the process proceeds to step S05.

  In step S05, it is determined whether the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 60 ° C. If the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is not within 60 ° C, the process proceeds to step S16, and the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 60 ° C. If so, the process proceeds to step S06.

  In step S06, it is determined whether the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 60 ° C. If the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is not within 60 ° C, the process proceeds to step S16, and the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 60 ° C. If so, the process proceeds to step S07. In the present embodiment, the upper temperature T1 and the middle temperature T2 of the fuel battery cell CE are compared, and the middle temperature T2 and the lower temperature T3 of the fuel battery cell CE are further compared. You may make it compare CE upper temperature T1 and lower temperature T3. In this case, the determination is made based on whether or not the difference between the upper temperature T1 and the lower temperature T3 of the fuel cell CE is within 120 ° C.

  In step S07, the shift to the combustion operation is permitted. In step S08 following step S07, it is determined whether the combustion operation is being performed. “Combustion operation” means a stage after combustion starts in the catalytic combustor 10. For example, in the operation example shown in FIG. 4, it is from time t 4 to time t 10. If the combustion operation is not being performed, the process returns. If the combustion operation is being performed, the process proceeds to step S09.

  In step S09, it is determined whether the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 75 ° C. If the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is not within 750 ° C., the process proceeds to step S16, and the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 75 ° C. If so, the process proceeds to step S10.

  In step S10, it is determined whether the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 75 ° C. If the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is not within 75 ° C, the process proceeds to step S16, and the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 75 ° C. If so, the process proceeds to step S11. In the present embodiment, the upper temperature T1 and the middle temperature T2 of the fuel battery cell CE are compared, and the middle temperature T2 and the lower temperature T3 of the fuel battery cell CE are further compared. You may make it compare CE upper temperature T1 and lower temperature T3. In this case, the determination is made based on whether or not the difference between the upper temperature T1 and the lower temperature T3 of the fuel cell CE is within 150 ° C.

  In step S11, a transition to a steam reforming operation (SR operation) is permitted. In step S12 following step S11, it is determined whether the steam reforming operation (SR operation) is being performed. The steam reforming operation (SR operation) means a stage before power generation starts after water and city gas are supplied so that the reforming reaction starts in the steam reformer RFS. In the example of operation as shown in FIG. 4, it is between time t10 and time t12. If the steam reforming operation (SR operation) is not in progress, the process returns. If the steam reforming operation (SR operation) is in progress, the process proceeds to step S13.

  In step S13, it is determined whether the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 100 ° C. If the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is not within 100 ° C., the process proceeds to step S16, and the difference between the upper temperature T1 and the middle temperature T2 of the fuel cell CE is within 100 ° C. If so, the process proceeds to step S14.

  In step S14, it is determined whether the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 100 ° C. If the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is not within 100 ° C, the process proceeds to step S16, and the difference between the middle temperature T2 and the lower temperature T3 of the fuel cell CE is within 100 ° C. If so, the process proceeds to step S15. In the present embodiment, the upper temperature T1 and the middle temperature T2 of the fuel battery cell CE are compared, and the middle temperature T2 and the lower temperature T3 of the fuel battery cell CE are further compared. You may make it compare CE upper temperature T1 and lower temperature T3. In this case, it is determined whether or not the difference between the upper temperature T1 and the lower temperature T3 of the fuel cell CE is within 200 ° C. Thus, in the present embodiment, the initial temperature difference limit in steps S05 and S06 is 60 ° C., and the late temperature difference limit in steps S13 and S14 is 100 ° C. Since the latter half of the operation is likely to have a temperature difference in the vertical direction, control according to the actual temperature state is possible by relaxing the temperature difference restriction in the second half.

  In step S15, permission to shift to power generation operation is given. On the other hand, in step S16, the energization amount to the air heater AH2 that supplies air to the catalytic combustor 10 is reduced, and the amount of heat given from the air heater AH2 is reduced. In step S17 following step S16, the shift to the power generation operation is prohibited.

  In step S16, although the energization amount to the air heater AH2 is reduced, it is also preferable to reduce the city gas supply amount to the catalytic combustor 10. Although it is more preferable to reduce the energization amount to the air heater AH2 from the viewpoint of temperature change sensitivity, it can be used in combination with a decrease in the supply amount of city gas when the temperature difference between the upper and lower fuel cells CE is extremely large. preferable.

  In the present embodiment, as described above, the oxidizing gas heated by the heater AH2 and the catalytic combustor 10 is supplied from above the fuel cell CE, and is raised by the partial oxidation reformer RFP from below the fuel cell CE. By supplying the heated fuel gas, the temperature is controlled above and below the fuel cell CE, and further, the temperature difference between the center part and the temperature difference between the upper part and the lower part is controlled not to open too much. ing. This concept is illustrated in FIG. 6. This is to prevent the temperature difference between the upper and lower sides of the fuel cell CE from opening after power generation. When the fuel cell CE enters a power generation state, the temperature at the center increases as shown in FIG. 7, and the upper and lower temperatures decrease. For example, if power generation is started without setting the temperature state as shown in FIG. 6, the temperature state as shown in FIG. 7 results, and the temperature deviation in the axial direction of the fuel cell CE increases, and the fuel cell CE becomes There is a risk of problems such as peeling. Therefore, by setting the temperature state as shown in FIG. 6 before the power generation state, the temperature state as shown in FIG. 8 can be obtained after the power generation, and the temperature deviation in the axial direction of the fuel cell CE is reduced. can do.

  Further, in the present embodiment, control is performed so that the downward heating of the fuel cell CE is performed as long as possible. This is because the combustion chamber FC2 is located above the fuel cell CE, so that it is heated from above even after the power generation operation, whereas there is no means for heating below the fuel cell CE. Because. For this reason, by supplying high temperature fuel gas from the partial oxidation reformer RFP below the fuel cell CE, the temperature below the fuel cell CE is prevented from lowering compared to the upper side. If power generation is started in a state where the temperature below the fuel cell CE is lower than the temperature above, the temperature state shown in FIG. 9 is reached, and only the temperature above the fuel cell CE rises, and the fuel cell This is because there is a possibility that defects such as peeling may occur in the cell CE.

ADU: Auxiliary unit AH1: Heater AH2: Heater AP: Air supply part AP1a, AP1b: Flow rate adjustment unit AP2: Solenoid valve CB: Control box CE: Fuel cell COD: Carbon monoxide detector CS: Fuel cell system controller CS1: Operating device CS2: Display device CS3: Notification device DS1: Reformer temperature sensor DS2: Stack temperature sensor DS3: Exhaust temperature sensor DS4: Reformer pressure sensor DS5: Water level sensor DS6: Water flow rate sensor DS7: Fuel flow rate Sensor DS8: Reforming air flow sensor DS9: Power generation air flow sensor DS10: Power state detection unit DS11: Hot water storage state detection sensor DS12: Carbon monoxide detection sensor DS13: Combustible gas detection sensor EP: Power extraction unit EP1: Power extraction Line FC: Fuel cell FC1: Power generation chamber FC2: Combustion chamber FCM: Fuel Pond module FCS: Fuel cell system FP: Fuel supply unit FP1: Flow rate adjustment unit FP2: Desulfurizer FP4, FP5: Gas shut-off valve GD1, GD2: Combustible gas detector HW: Hot water production device MV: Mixing unit RF: Reformer RF1: reforming unit RF2: evaporation unit SC: fuel cell system control unit WP: water supply unit WP1: flow rate adjusting unit WP2: water storage tank 10: catalytic combustor 15: air header RFP: partial oxidation reformer RFS: steam reforming Quality unit RFS1: Reforming unit RFS1: Evaporating unit RFS2: Preheating unit RFS3: Reforming unit 20: Air flow rate (catalyst combustor)
21: City gas flow rate (catalyst combustor)
22: Heater temperature 23: Catalyst combustor outlet temperature 24: Combustion chamber temperature 25: Air flow rate (partial oxidation reformer)
26: City gas flow rate (partial oxidation reformer)
27: Water flow rate (partial oxidation reformer)
28: Heater temperature 29: Reaction tube inlet temperature (partial oxidation reformer)
30: Reaction tube outlet temperature (partial oxidation reformer)
31: Fuel cell temperature 32: City gas flow rate (steam reformer)
33: Water flow rate (steam reformer)
34: Current

Claims (8)

A fuel cell system that includes a solid electrolyte fuel cell and transitions the operating state to a power generation operation in which power generation is performed in the fuel cell after performing a startup operation,
A fuel gas is supplied to the anode side, and an oxidizing gas is supplied to the cathode side so as to perform a power generation reaction, and a plurality of tubular fuel cells standing in the vertical direction; and
A first reformer that is mainly used in the power generation operation and reforms the gas to be reformed to generate fuel gas;
A second reformer that is mainly used in the start-up operation and reforms the gas to be reformed to generate fuel gas;
An air heating unit for supplying a heated oxidizing gas to the fuel cell;
A control unit that controls the first reformer, the second reformer, and the air heating unit, and shifts the operation from a start-up operation to a power generation operation,
The controller controls the second reformer to generate a high-temperature fuel gas using heat generated by the partial oxidation reforming reaction and supply the fuel cell to the fuel cell in the start-up operation. The first reformer is controlled so as to supply the fuel cell with fuel gas generated by mainly performing a steam reforming reaction,
The fuel gas reformed in the second reformer is supplied from below the fuel battery cell, and the oxidizing gas heated in the air heating unit is supplied from above the fuel battery cell. A fuel cell system.   The control unit is configured to control the second reformer so that a difference between a temperature at a lower portion of the fuel battery cell and a temperature at a specific position above the lower portion of the fuel battery cell is within a first predetermined temperature difference. 2. The fuel cell system according to claim 1, wherein temperature deviation relaxation control is executed by controlling at least one of the air heating unit.   The control unit is configured such that a difference between a temperature at the lower part of the fuel cell and a temperature at a middle part above the lower part of the fuel cell falls within a second predetermined temperature difference, and at the middle part of the fuel cell. Controlling at least one of the second reformer and the air heating unit so that the difference between the temperature and the temperature at the upper part above the middle part of the fuel cell falls within a third predetermined temperature difference, The fuel cell system according to claim 2, wherein temperature deviation relaxation control is executed. A lower temperature measuring unit for measuring a temperature at the lower part of the fuel cell, a middle temperature measuring unit for measuring a temperature at the middle part of the fuel cell, and an upper temperature for measuring a temperature at the upper part of the fuel cell. A measurement unit,
The said control part performs the said temperature deviation relaxation control based on the temperature of the said fuel cell measured by the said lower temperature measurement part, the said middle temperature measurement part, and the said upper temperature measurement part, It is characterized by the above-mentioned. 4. The fuel cell system according to 3. The fuel battery cell is configured to be supplied with oxidizing gas inside,
The fuel cell system according to claim 2, wherein the control unit executes the temperature deviation relaxation control by controlling the air heating unit.   The fuel cell system according to claim 5, wherein the control unit controls the air heating unit so as to reduce a heat amount of an oxidizing gas supplied to the inside of the fuel cell.   The fuel cell system according to claim 6, wherein the control unit controls the air heating unit so as to reduce an amount of heat input to the oxidizing gas supplied to the inside of the fuel cell.   The air heating unit has a combustion catalyst for further raising the temperature of the oxidizing gas preheated by the heater by combustion of the fuel, and the amount of heat input to the oxidizing gas is reduced by preferentially reducing the fuel. The fuel cell system according to claim 7, wherein:

Images