JP5348401B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including fuel cells.

  Conventionally, there is a solid oxide fuel cell (hereinafter also referred to as SOFC) as a kind of fuel cell. As a fuel cell system including this fuel cell, for example, the fuel cell is formed into a bottomed or bottomed cylindrical shape and the like, and a fuel gas containing hydrogen is passed inside or outside thereof, and oxidation is performed on the opposite side. What makes an electric power generation reaction by passing agent gas (air) is known. As the fuel gas supply source, a gas to be reformed such as city gas is usually used. Therefore, a steam reforming reaction (SR: Steam Reforming) is caused by a reformer to obtain a hydrogen-rich fuel gas. ing.

  As a problem associated with the operation of the fuel cell system including such a fuel cell, oxidation of the fuel cell in the initial start (operation start period) and the operation stop period can be cited. Further, since the steam reforming reaction (SR) is an endothermic reaction, if the steam reforming reaction (SR) is performed immediately at the beginning of the start of the fuel cell system, the temperature of the fuel cell module does not rise, It is also known that it does not rise to a stable operating temperature. Therefore, at the beginning of startup, only the air and the gas to be reformed are sent to the reformer, and a partial oxidation reforming reaction (POX: Partial Oxidation Reforming) is performed as an exothermic reaction. When the temperature reaches about 700 ° C., the steam reforming reaction (SR) is switched, and during the shutdown period, the steam reforming reaction (SR) is switched to the partial oxidation reforming reaction (POX) to oxidize the fuel cell. There is a driving method to prevent it. (For example, refer to Patent Document 1).

JP 2005-293951 A

  Here, the partial oxidation reforming reaction (POX) is performed at about 300 ° C. or more, and the partial oxidation reformer that performs the partial oxidation reforming reaction (POX) is usually about 10 minutes from the start of operation. Heated to about 300 ° C. or higher. On the other hand, the power generation temperature region of the fuel cell is about 650 ° C. or higher, preferably 700 ° C. or higher, but the temperature increase rate of the fuel cell is very slow compared to the temperature increase rate of the partial oxidation reformer. Even when the partial oxidation reformer reaches 300 ° C. or higher, the temperature of the fuel cell is usually less than 50 ° C. or about room temperature.

  By the way, the fuel cell system described in Patent Document 1 described above has a configuration in which both a steam reformer that performs a steam reforming reaction (SR) and a partial oxidation reformer are disposed in the fuel cell module. It has. That is, the partial oxidation reformer is disposed at a position close to the fuel cell. Therefore, in the fuel cell system described in Patent Document 1, when the partial oxidation reformer is heated in order to perform a partial oxidation reforming reaction (POX) at the beginning of startup, before the temperature of the fuel cell rises, The temperature of the oxidation reformer becomes 300 ° C. or higher, and the region of the fuel cell that receives the radiant heat from the partial oxidation reformer is locally heated. For this reason, a high-temperature part and a low-temperature part are generated in the fuel cell (heat unevenness occurs), and there is a possibility that the fuel cell is likely to be damaged. Further, when focusing on the entire cell stack composed of a plurality of fuel cells, the temperature of the fuel cells arranged near the partial oxidation reformer increases, and the high temperature portion is also unevenly distributed in the entire cell stack. Temperature distribution may occur, and stable operation may not be possible.

  The present invention has been made in view of such circumstances, and in a fuel cell system including fuel cells, the fuel cells can be prevented from being oxidized, and the fuel cells and the cell stack at the beginning of startup. An object of the present invention is to provide a fuel cell system capable of suppressing the occurrence of heat unevenness throughout.

  In order to achieve this object, the present invention provides a fuel cell system including solid electrolyte fuel cells, a power generation chamber in which a plurality of fuel cells are disposed, and a combustion disposed above the power generation chamber. A first reformer that is disposed above the combustion chamber and performs steam reforming of the fuel gas, a start mode for starting the fuel cell system, and a stop mode for stopping the power generation A fuel cell module having a second reformer that performs partial oxidation reforming of the fuel gas, and the power generation chamber contains the fuel gas reformed by the first reformer and the second reformer. The second reformer is introduced from the lower part and provides a fuel cell system that is disposed outside and outside the vessel forming the power generation chamber and the combustion chamber.

  According to the fuel cell system of the present invention, the second reformer that performs partial oxidation reforming of the fuel gas during the start-up mode and the operation stop mode (operation stop period) of the fuel cell system includes the power generation chamber. In addition, since the second reformer is disposed outside the container forming the combustion chamber, the radiant heat of the second reformer does not directly affect the fuel cells disposed in the container. Accordingly, the second reformer reaches about 300 ° C. or more in about 10 minutes from the start of startup, and at this time, even if the temperature of the fuel cell disposed in the container is low, the fuel It is possible to prevent the battery cell from being locally heated by the radiant heat of the second reformer, and to suppress the occurrence of heat unevenness in the fuel battery cell. In addition, it is possible to prevent a temperature distribution in which local high temperature portions are unevenly distributed in the entire cell stack including a plurality of fuel cells. In addition, the second reformer is disposed on the outside lower side of the container, and the fuel gas is introduced into the power generation chamber from the bottom, thereby preventing the second reformer from radiating heat. The heating in the container can be promoted. Furthermore, since the second reformer is disposed outside the vessel, the catalyst can be easily exchanged. On the other hand, since the first reformer that performs steam reforming of the fuel gas is disposed above the combustion chamber, it can efficiently perform an endothermic reaction using heat generated in the combustion chamber.

  In the fuel cell system according to the present invention, the second reformer can be disposed in the vicinity of the power generation chamber. With this configuration, it is possible to further prevent the second reformer from radiating heat during the start-up mode, and to promote heating in the container. On the other hand, when the operation stop mode is entered, since the power generation chamber is at a high temperature (for example, about 900 ° C.), the steam reforming reaction (SR) is shifted to the partial oxidation reforming reaction (POX). In this case, the heat of the power generation chamber can be used as heat for raising the temperature of the second reformer, and the switching can be performed smoothly.

  Moreover, in the fuel cell system according to the present invention, the second reformer can be disposed below the outside of the container via a heat insulating material. With this configuration, even when the second reformer reaches a high temperature at the beginning of startup, since this heat is absorbed by the heat insulating material, the fuel cell is further affected by the radiant heat of the second reformer. Can be prevented.

  Furthermore, in the fuel cell system according to the present invention, a heat insulating material can be provided in a pipe for supplying the fuel gas reformed by the second reformer into the container. With this configuration, heat radiation from the pipe can be prevented, and heating in the container can be further promoted in the startup mode.

  Further, in the fuel cell system according to the present invention, the container is disposed below the power generation chamber and the fuel gas reformed by the first reformer and the second reformer is dispersed to generate the power generation. A dispersion chamber supplied to the chamber may be further formed, and the second reformer may be disposed at a position outside the lower surface of the dispersion chamber. With this configuration, since the fuel gas heated in the second reformer is introduced into the power generation chamber via the dispersion chamber, the fuel gas can be supplied to the power generation chamber in a uniform state. In addition, heating in the container can be promoted during the start-up mode.

  In addition, in the case of this configuration, by disposing the second reformer in the central portion at the position outside the lower surface of the dispersion chamber, it is possible to further prevent heat dissipation from the second reformer. In addition, the dispersibility of the fuel gas can be improved, and the fuel gas can be supplied to the power generation chamber in a more uniform state.

  In the fuel cell system according to the present invention, the second reformer includes a partial oxidation reformer for start-up that performs partial oxidation reforming of the fuel gas in the start-up mode of the fuel cell system, and the fuel cell. A partial oxidation reformer for stopping that performs partial oxidation reforming of the fuel gas during the system shutdown mode, and the partial oxidation reformer for stop is more than the partial oxidation reformer for startup It can also be arranged at a position far from the container. Here, the second reformer can prevent heat radiation as it is disposed in the vicinity of the container. Therefore, with this configuration, in the start-up mode, heat release from the second reformer can be efficiently prevented, and heating in the vessel can be promoted. Since it is possible to supply the container with a fluid having a temperature lower than that in the activation mode, the inside of the container can be cooled more efficiently.

  Furthermore, the fuel cell system according to the present invention includes a plurality of pipes that are disposed on the downstream side of the second reformer, and communicates the second reformer and the container. Among them, the fluid discharged from the second reformer during the start-up mode of the fuel cell system is passed through a pipe disposed at a position closest to the container, and is disposed at a position farthest from the container. The pipe that is provided can be provided with a configuration that allows the fluid discharged from the second reformer to pass in the operation stop mode of the fuel cell system. With this configuration, in the start-up mode, it is possible to efficiently prevent heat dissipation of the pipe through which the fluid discharged from the second reformer flows, and to promote heating in the container. In this case, since the fluid having a temperature lower than that in the activation mode can be supplied into the container, the inside of the container can be cooled more efficiently.

  According to the present invention, in a fuel cell system including a fuel cell, it is possible to prevent the fuel cell from being oxidized, and to suppress the occurrence of heat unevenness in the entire fuel cell or cell stack at the beginning of startup. The fuel cell system which can be provided can be provided.

1 is a schematic configuration diagram showing 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 graph which shows the temperature of each part in the starting mode of the fuel cell system shown in FIG. 1, and the control voltage of each part. FIG. 2 is a schematic configuration diagram more specifically showing a configuration in the vicinity of the fuel cell module of the fuel cell system shown in FIG. 1. It is sectional drawing along the VV line shown in FIG. It is a graph which shows the temperature of each part in the motion stop mode of the fuel cell system shown in FIG. 1, and the fluid flow volume supplied to each part. It is a schematic block diagram which shows more specifically the structure of the vicinity of the fuel cell module of the fuel cell system according to another embodiment of the present invention. It is a schematic block diagram which shows more specifically the structure of the vicinity of the fuel cell module of the fuel cell system according to another embodiment of the present invention. It is a schematic block diagram which shows more specifically the structure of the vicinity of the fuel cell module of the fuel cell system according to another embodiment of the present invention.

  Next, a fuel cell system according to an embodiment of the present invention will be described with reference to the drawings. In addition, the Example described below is the illustration for demonstrating this invention, and this invention is not limited only to these Examples. Therefore, the present invention can be implemented in various forms without departing from the gist thereof.

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

  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 electrolyte 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 and an air electrode with an electrolyte sandwiched between them. Electric power is generated by passing fuel gas to the fuel electrode side and air as oxidant gas to the air electrode side. It is configured so that a reaction can occur.

  In addition, since the fuel cell FC according to the present embodiment is a solid electrolyte fuel cell (SOFC), the material constituting the electrolyte is doped with at least one selected from rare earth elements such as Y and Sc, for example. Oxygen ion conductive oxides such as ceria doped with at least one selected from zirconia and rare earth elements, and lanthanum gallate doped with at least one selected from Sr and Mg are 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 a gas to be reformed, such as city gas, 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), auto thermal reforming reaction (ATR), and steam reforming reaction (SR). (Details will be described later). The reformer RF includes a reforming unit RF1 and an evaporation unit RF2. Details of the reformer RF will be described later.

  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, those obtained by imparting Ni to the sphere surface of alumina and those imparting Ru to the sphere surface of alumina are appropriately used. In this 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 or not carbon monoxide is generated due to incomplete combustion of the remaining fuel gas in the combustion chamber FC2. The combustible gas detector GD1 is a sensor for detecting whether the remaining fuel gas remains unburned in the combustion chamber FC2, and so-called raw gas is discharged outside as exhaust gas.

  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, AP1b, and an electromagnetic valve AP2 that include an air blower, a flow rate adjustment valve, and the like as an air supply unit, and a flow rate adjustment unit FP1, which includes a fuel pump, a flow rate adjustment valve, and the like 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 by the heater AH2 as power generation air and supplied to the power generation chamber FC1. The power generation air supplied to the power generation chamber FC1 is supplied to the air electrode of the fuel cell CE and used for power generation 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 both of the gas cutoff valves FP4 and FP5 are open, the city gas is supplied to the desulfurizer FP2, and if one 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.

  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 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, the 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, the operation device CS1, the display device CS2, and the notification device CS3 are housed in a control box CB.

  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.

  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 the generation of carbon monoxide in the fuel cell module FCM. The combustible gas detection sensor DS13 is a sensor provided in the combustible gas detectors GD1 and GD2. In the combustible gas detector GD1, the remaining fuel gas remains unburned in the combustion chamber FC2 of the fuel cell module FCM. In other words, the combustible gas detector GD2 is a sensor that detects leakage of combustible gas in the fuel cell module FCM and the auxiliary unit ADU.

  Next, switching of various reforming reactions when the fuel cell system FCS is started (starting mode) will be described with reference to FIG. FIG. 3 is a graph showing the temperature of each part and the control voltage of each part in the startup mode of the fuel cell system FCS.

  In the start-up mode of the fuel cell system FCS in this embodiment, combustion operation, partial oxidation reforming reaction (POX), first autothermal reforming reaction (ATR1), and second autothermal reforming reaction (ATR2) And the steam reforming reaction (SR) are sequentially switched and the reforming reaction proceeds. Prior to explaining FIG. 3, each reforming reaction will be explained.

The partial oxidation reforming reaction (POX) is a reforming reaction performed by supplying a reformed gas and air to the reformer SR, and the reaction shown in the chemical reaction formula (1) proceeds.
_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)
Since this partial oxidation reforming reaction (POX) is an exothermic reaction, its 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 used only at the beginning of startup when heat supply to the fuel cell module FCM is required. This is a preferred reforming reaction. If attention is paid only to the partial oxidation reforming reaction (POX), the space velocity is set high. For example, when the reformer RF is dividedly formed and a reformer dedicated to the partial oxidation reforming reaction (POX) is provided. In addition, the dedicated reformer can be miniaturized.

The steam reforming reaction (SR) is a reforming reaction performed by supplying the reformed gas and steam to the reformer SR, and the reaction shown in the chemical reaction formula (2) proceeds.
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (2)
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 beginning of the start of the fuel cell system FCS. If attention is paid only to the steam reforming reaction (SR), the space velocity is set low, so that the reformer RF tends to increase in size.

The autothermal reforming reaction (ATR) comprising the first autothermal reforming reaction (ATR1) and the second autothermal reforming reaction (ATR2) is a partial oxidation reforming reaction (POX) and a steam reforming reaction (SR). Is a reforming reaction that is performed by supplying a reforming gas, air, and steam to the reformer RF, and the reaction shown in the chemical reaction formula (3) proceeds. .
_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (3)
Autothermal reforming reaction (ATR) is a combined use of partial oxidation reforming reaction (POX) and steam reforming reaction (SR) in hydrogen yield, and it is easy to balance reaction heat. POX) is a reforming reaction suitable as a reaction that connects the steam reforming reaction (SR). In the case of the present embodiment, the first autothermal reforming reaction (ATR1) closer to the partial oxidation reforming reaction (POX) is performed by supplying a small amount of water, and the water is supplied to increase after the temperature rises. Then, the second autothermal reforming reaction (ATR2) closer to the steam reforming reaction (SR) is performed later.

  Next, the startup mode of the fuel cell system FCS will be described. In FIG. 3, the horizontal axis indicates the elapsed time after the start of startup, and the left vertical axis indicates the temperature of each part. Although it is a control voltage, no special scale is provided, but the control voltage of the reforming air blower included in the flow rate adjusting unit AP1a for supplying reforming air, the flow rate adjustment for supplying power generation air Included in the control voltage of the power generation air blower included in the unit AP1b, the control voltage of the fuel pump included in the flow rate adjustment unit FP1 for supplying the reformed gas, and the flow rate adjustment unit WP1 for supplying pure water The control voltage of the water pump is shown so that the voltage increases (the supply amount increases) as it goes upward in the figure. FIG. 3 shows the temperature of the reformer RF, the stack temperature of the fuel cell CE, the temperature of the combustion chamber FC2 (estimated from the temperature of the reformer RF, etc.), and the reforming included in the flow rate adjustment unit AP1a. The control voltage of the air blower, the control voltage of the power generation air blower included in the flow rate adjustment unit AP1b, the control voltage of the fuel pump included in the flow rate adjustment unit FP2, and the control voltage of the water pump included in the flow rate adjustment unit WP1 are shown. .

  First, the flow rate adjustment unit AP1a, the electromagnetic valve AP2, the heater AH1, and the mixing unit MV are controlled so as to increase the reforming air, and air is supplied to the reformer RF. Further, the flow rate adjusting unit FP1, the gas cutoff valves FP4 and FP5, and the mixing unit MV are controlled so as to increase the supply of the reformed gas, and the reformed gas is supplied to the reformer RF. In this way, air and the gas to be reformed are supplied, and ignited by the igniter to execute the combustion operation. The combustion operation may be performed by raising the temperature of the combustion chamber FC2 and spontaneously igniting the air and the reformed gas. In the combustion chamber FC2 above the power generation chamber FC1, the fuel gas that has passed through the reformer RF and the power generation air are mixed and burned, and the temperature of the combustion chamber FC2 gradually increases.

  Subsequently, when the temperature of the reformer RF reaches about 300 ° C., the reformer RF becomes ready for partial oxidation reforming reaction operation (POX operation). The partial oxidation reforming reaction (POX) proceeds when it becomes forward or backward. Since the partial oxidation reforming reaction (POX) is an exothermic reaction, the temperature of each part increases. After a predetermined time has elapsed since the partial oxidation reforming reaction (POX) was started, the supply amount of reforming air is further increased to further advance the partial oxidation reforming reaction (POX).

  Subsequently, the first autothermal reforming reaction ATR1 is performed on the condition that the temperature of the reformer RF becomes about 600 ° C. or higher and the temperature of the cell stack constituted by the fuel cells CE exceeds about 250 ° C. To move to. In the first autothermal reforming reaction ATR1, the flow rate of reforming air supplied to the reformer RF is reduced, the flow rate of the gas to be reformed supplied to the reformer RF is maintained as it is, and a very small amount of pure water is supplied. Supply to reformer RF. The autothermal reforming reaction (ATR) is a reaction in which a partial oxidation reforming reaction (ATR) and a steam reforming reaction (SR) are mixed and is thermally balanced in the reformer RF. The reaction proceeds independently. The first autothermal reforming reaction (ATR1) is a reaction that has a relatively large amount of air and is close to the partial oxidation reforming reaction (POX), and heat generation is the dominant reaction. Note that, in the first autothermal reforming reaction (ATR1), the temperature of the cell stack constituted by the fuel cells CE is about 250 to about 400 ° C.

  Subsequently, the second autothermal reforming reaction (ATR2) is performed on the condition that the temperature of the reformer RF becomes 600 ° C. or higher and the temperature of the cell stack constituted by the fuel cell CE exceeds about 400 ° C. To move to. In the second autothermal reforming reaction (ATR2), the flow rate of reforming air supplied to the reformer RF is reduced, the flow rate of reformed gas supplied to the reformer RF is also reduced, and a small amount of pure water is modified. Supply to mass device RF. The second autothermal reforming reaction (ATR2) is a reaction close to the steam reforming reaction (SR) because of relatively little air and a lot of water, and the endothermic reaction is dominant. However, since the cell stack temperature indicating the temperature in the power generation chamber FC1 exceeds about 400 ° C., even if the endothermic reaction is dominant, there is no significant temperature drop. In addition, the temperature of the evaporation part RF2 in the second autothermal reforming reaction (ATR2) is about 100 ° C. or higher.

  Subsequently, the process proceeds to the steam reforming reaction (SR) on the condition that the temperature of the reformer RF becomes 650 ° C. or higher and the temperature of the cell stack constituted by the fuel cell CE exceeds about 600 ° C. Let In the steam reforming reaction (SR), the reforming air supplied to the reformer RF is shut off, the flow rate of the reformed gas supplied to the reformer RF is reduced, and a predetermined amount of pure water is supplied to the reformer RF. To supply. Since this steam reforming reaction (SR) is an endothermic reaction, the reaction proceeds while maintaining a heat balance by the combustion heat from the combustion chamber FC2. At this stage, since it is already the final stage of startup, the inside of the power generation chamber FC1 has been heated to a sufficiently high temperature, so that no significant temperature decrease is caused even with the endothermic reaction as a main component. Even if the steam reforming reaction (SR) proceeds, the combustion reaction continues in the combustion chamber FC2.

  As described above, the temperature in the power generation chamber FC1 gradually increases by switching the reforming process from the ignition to the progress of the combustion process. When the temperature of the power generation chamber FC1 (cell stack temperature) reaches a predetermined power generation temperature lower than the rated temperature (about 700 ° C.) at which the fuel cell module FCM is stably operated, the electric circuit including the fuel cell module FCM is changed. close up. As a result, the fuel cell module FCM starts power generation, and a current flows through the circuit to supply power to the outside. Due to the power generation of the fuel cell CE, the fuel cell CE itself also generates heat, and the temperature of the fuel cell CE rises. As a result, the rated temperature for operating the fuel cell module FCM, for example, 700 to 800 ° C. is reached.

  Thereafter, in order to maintain the rated temperature, fuel gas and air in an amount larger than the amount of fuel gas and air consumed in the fuel battery cell CE are supplied, and combustion in the combustion chamber FC2 is continued. During power generation, power generation proceeds by a steam reforming reaction (SR) with high reforming efficiency. Strictly speaking, the steam reforming reaction (SR) itself is performed at about 400 to 800 ° C., but the reaction proceeds at about 500 to 700 ° C. in combination with the fuel cell CE.

  Next, the fuel cell module according to this embodiment will be described in more detail with reference to FIGS. FIG. 4 is a schematic configuration diagram more specifically showing the configuration in the vicinity of the fuel cell module according to the present embodiment, and FIG. 5 is a cross-sectional view taken along line VV shown in FIG.

  As shown in FIG. 4, the fuel cell module FCM according to the present embodiment includes a power generation chamber FC1, a dispersion chamber DB, a combustion chamber FC2, a steam reformer RFS, a preheater PH, an evaporation unit RF2, The partial oxidation reformer RFP is provided, and the power generation chamber FC1, the dispersion chamber DB, the combustion chamber FC2, the steam reformer RFS, the preheater PH, and the evaporation unit RF2 are accommodated in the same container C. 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 reformer RF and uniformly supplying the fuel gas into the power generation chamber FC1, and the fuel gas is generated on the upper wall of the power generation chamber. A plurality of holes DBH to be supplied into FC1 are formed through. As shown in FIG. 5 in particular, the plurality of holes DBH are opened in the gaps between the plurality of fuel cells CE provided upright in the power generation chamber FC1. Further, an introduction hole (not shown) for introducing a fuel gas supplied from a partial oxidation reformer RFP, which will be described in detail later, into the dispersion chamber DB is formed through the bottom surface of the dispersion chamber DB. Thereby, 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, and FIG. 1 and FIG. As shown in FIG. 2, the fuel cell CE is installed in the power generation chamber FC1 and supplied to the fuel electrode of the fuel cell CE. A heat insulating material HI is disposed on the outer surface of the side wall and the outer surface of the bottom surface of the container C.

  As described above, the reformer RF includes the reforming unit RF1 and the evaporation unit RF2. The reforming unit RF1 further includes a steam reformer RFS that performs steam reforming of the fuel gas, and a fuel gas. And a partial oxidation reformer RFP for performing partial oxidation reforming.

  The steam reformer RFS is disposed in the upper part of the combustion chamber FC2. A preheater PH is disposed above the steam reformer RFS, and the pure water and the gas to be reformed supplied to the steam reformer RFS are supplied to the steam reformer RFS via the preheater PH. Supplied. The evaporating unit RF2 evaporates pure water supplied from the auxiliary unit ADU side into steam, and supplies the steam to the steam reformer RFS. Since this steam reformer RFS is disposed in the container C and is disposed above the combustion chamber FC2 disposed in the same container C, it uses heat generated in the combustion chamber FC2. An endothermic reaction can be performed efficiently.

  The partial oxidation reformer RFP is disposed substantially at the center of the outer bottom surface of the dispersion chamber DB that defines the outer bottom surface of the container C. In this embodiment, the partial oxidation reformer RFP is supplied with a gas to be reformed, air, and pure water. The reformed fuel gas is formed on the bottom surface of the dispersion chamber DB. The dispersion chamber DB is supplied from the introduction hole (not shown). By disposing the partial oxidation reformer RFP at the lower center of the dispersion chamber DB, heat radiation from the partial oxidation reformer RFP can be prevented and the dispersibility of the fuel gas in the dispersion chamber DB can be improved. Can do. Therefore, the fuel gas can be supplied to the power generation chamber FC1 in a uniform state, and the power generation efficiency can be improved. The partial oxidation reformer RFP performs partial oxidation reforming on the gas to be reformed in the start-up mode and in the operation stop mode described in detail later, but does not require water. At (POX), the fuel cell system control unit CS performs control so that pure water is not supplied to the partial oxidation reformer RFP.

  Here, as shown in FIG. 3, the partial oxidation reformer RFP reaches about 300 ° C. in about 10 minutes after ignition in the startup mode, and at this time, the temperature of the cell stack is about 100 ° C. There is a significant temperature difference between the two. At this time, if the partial oxidation reformer RFP is disposed in the container C as in the conventional fuel cell system, the fuel cell CE is locally heated by the radiant heat of the partial oxidation reformer RFP, Heat unevenness occurs in the fuel cell CE and is easily damaged. In addition, a temperature distribution in which local high temperature portions are unevenly distributed occurs in the entire cell stack, and power generation efficiency may be reduced. On the other hand, in the present embodiment, the partial oxidation reformer RFP is disposed on the outside lower side of the container C (outside of the bottom surface of the dispersion chamber DB), so that in the start-up mode, the partial oxidation reformer RFP radiates heat. The fuel cell CE can be prevented from being locally heated, and the temperature distribution in which local high temperature portions are unevenly distributed can be prevented from occurring in the entire cell stack. In addition, since the piping for fuel gas distribution between the partial oxidation reformer RFP and the dispersion chamber DB can be shortened or eliminated, the heat radiation in the piping portion can be reduced as much as possible, and the partial oxidation reforming can be performed. Heating of the container C by the fuel gas heated by the mass device RFP can be further promoted. Further, since the heat insulating material HI is disposed on the outer surface of the side wall and the bottom surface of the container C, the fuel cell CE and the entire cell stack are caused by the radiant heat of the partial oxidation reformer RFP in the start-up mode. It can be further prevented from being affected.

  Next, switching of various reforming reactions when the fuel cell system FCS is stopped (operation stop mode) will be described with reference to FIG. FIG. 6 is a graph showing the temperature of each part and the flow rate of fluid supplied to each part in the motion stop mode of the fuel cell system FCS. In FIG. 6, the horizontal axis represents the elapsed time of the operation stop mode, and the left vertical axis represents the flow rate of the fluid supplied to each part. Since it is a fluid flow rate, no special scale is given, but the flow rate increases as it goes upward in the figure.

  FIG. 6 shows the temperature of the partial oxidation reformer RFP, the stack temperature of the fuel cell CE, the flow rate of pure water supplied to the steam reformer RFS, the flow rate of fuel gas supplied to the steam reformer RFS, and the partial oxidation. The flow rate of air supplied to the reformer RFP, the flow rate of pure water supplied to the partial oxidation reformer RFP, the flow rate of fuel gas supplied to the partial oxidation reformer RFP, and the amount of power generation current of the fuel cell FC are shown. Yes.

  In the shutdown mode, first, in order to shift from the steam reforming reaction (SR) to the reaction including the partial oxidation reforming reaction (POX), the flow rate adjusting unit WP1 is controlled to control the flow rate of pure water to the steam reformer RFS. Decrease. Further, the flow rate adjusting unit FP1, the gas shut-off valves FP4 and FP5, and the mixing unit MV are controlled so as to reduce the flow rate of the reformed gas supplied to the steam reformer RFS. Further, the flow rate adjusting unit AP1b is controlled so as to reduce the flow rate of the power generation air supplied to the power generation chamber FC1. The current generated by the fuel cell FC decreases as the pure water flow rate and the fuel gas flow rate to the steam reformer RFS decrease. During the steam reforming reaction (SR), the partial oxidation reformer RFP is about 500 ° C. due to the radiant heat from the container C. At this time, the fuel cell CE is more than the partial oxidation reformer RFP. Therefore, the temperature of the partial oxidation reformer RFP does not locally increase the temperature of the fuel cell CE.

  Next, the pure water flow rate and the fuel gas flow rate to the steam reformer RFS have reached a predetermined amount. In this state, a predetermined time has elapsed, and the flow rate of power generation air supplied to the power generation chamber FC1 has reached a predetermined amount. As a condition, a minute amount of pure water is supplied to the partial oxidation reformer RFP, and then a predetermined amount of fuel gas and reforming air are supplied to perform a reaction including a partial oxidation reforming reaction (POX). . As shown in FIG. 6, at the initial stage of supplying pure water, fuel gas, and reforming air to the partial oxidation reformer RFP, the supply of pure water and fuel gas to the steam reformer RFS is continued. However, the supply of pure water and fuel gas to the steam reformer RFS is stopped when the reaction including the partial oxidation reforming reaction (POX) proceeds to some extent. At the time of the reaction including the partial oxidation reforming reaction (POX), the power generation air of about 300 ° C. is supplied to the power generation chamber FC1, so that the temperature is raised to about 950 ° C. at the beginning of the reaction including the partial oxidation reforming reaction (POX). The heated cell stack is mainly cooled by the power generation air, and the reaction including the partial oxidation reforming reaction (POX) is performed until the cell stack temperature reaches about 300 ° C. Further, the oxidation of the fuel cell CE can be prevented by causing the reaction including the partial oxidation reforming reaction (POX) to occur in the cell oxidation temperature region in which the fuel cell CE is easily oxidized.

  On condition that the temperature of the cell stack reaches about 300 ° C., the supply of air to the partial oxidation reformer RFP is stopped, and then the supply of fuel gas and the supply of pure water are sequentially stopped. With this operation, the cell stack temperature gradually decreases, and the temperature of the partial oxidation reformer RFP decreases from the time when the supply of the fuel gas is stopped to 100 ° C. or less. After a predetermined time has elapsed after the temperature of the cell stack and the temperature of the partial oxidation reformer RFP have become 100 ° C. or less, the supply of power generation air is stopped.

  In addition, although the present Example demonstrated the case where the heat insulating material HI was arrange | positioned on the outer surface of the side wall of the container C, and the outer surface of the bottom face, it is not restricted to this but the heat insulating material HI does not necessarily need to be arrange | positioned. In the case where the material HI is disposed, if the partial oxidation reformer RFP is disposed in the container C via the heat insulating material HI, the location, area, etc. of the heat insulating material HI can be determined as appropriate. Good. For example, although the container C described in FIGS. 7 to 9 described later is described in a state in which the heat insulating material HI is not provided, the partial oxidation reformer RFP also includes the heat insulating material HI in these containers C. The heat insulating material HI may be disposed in the partial oxidation reformer RFP so as to be disposed through the heat exchanger. Further, the heat insulating material HI may be provided on the outer surface of the partial oxidation reformer RFP, or may be provided independently between the container C and the partial oxidation reformer RFP.

  In the present embodiment, the case where the partial oxidation reformer RFP is disposed at the substantially central portion of the outer bottom surface of the container C has been described. For example, as shown in FIG. 7, the partial oxidation reformer RFP may be located at the lower outer side of the side wall of the container C. In the case of this configuration, the piping that allows the fuel gas to flow through the partial oxidation reformer RFP and the dispersion chamber DB may be surrounded by the heat insulating material HI. Thus, by disposing the heat insulating material HI in the pipe, it is possible to prevent heat from being radiated from the pipe during the start-up mode, and it is possible to further promote the heating in the container C.

  Further, in the fuel cell system FCS according to the present invention, as shown in FIG. 8, a pipe PP1 for branching the pipe on the downstream side of the partial oxidation reformer RFP into two and allowing the fluid to pass in the start mode and It is good also as a structure divided into piping PP2 which lets a fluid pass in the case of operation stop mode. In this configuration, since the pipe PP1 promotes heating in the container C in the start mode, the path to the dispersion chamber DB is shortened so that the heat radiation from the pipe PP1 can be prevented, and the pipe PP2 is In order to promote cooling in the container C during the operation stop mode, it is desirable to lengthen the path to the dispersion chamber DB. The pipe PP1 and the pipe PP2 are provided with gas cutoff valves FP6 and FP7, respectively, and in the start mode, the fuel cutoff control valve CS opens the gas cutoff valve FP6 and closes the gas cutoff valve FP7. In the operation stop mode, the gas cutoff valve FP7 is opened and the gas cutoff valve FP6 is closed. In addition, also in this structure, you may arrange | position a heat insulating material to piping PP1.

  Furthermore, in the fuel cell system FCS according to the present invention, as shown in FIG. 9, the partial oxidation reformer RFP is a partial oxidation reformer for start-up that performs a partial oxidation reforming reaction (POX) in the start-up mode. You may comprise RFP1 and the partial oxidation reformer RFP2 for a stop which performs a partial oxidation reforming reaction (POX) in the shutdown mode. In the configuration shown in FIG. 9, the partial oxidation reformer RFP2 for stopping is disposed at a position farther from the container C than the partial oxidation reformer RFP1 for activation. With this configuration, in the start-up mode, heat release from the start-up partial oxidation reformer RFP1 is efficiently prevented to promote heating in the container C, and in the operation stop mode, the heat-up is started in the container C. Since the fluid having a temperature lower than that in the mode can be supplied, the inside of the container C can be further efficiently cooled. In the case where the starting partial oxidation reformer RFP1 and the stopping partial oxidation reformer RFP2 are provided, the starting partial oxidation reformer RFP1 and the stopping partial oxidation reformer RFP2 are shown in FIG. They may be close to each other, or may be arranged with a desired interval between them. Moreover, also in this structure, you may arrange | position a heat insulating material to piping arrange | positioned downstream of the partial oxidation reformer RFP1 for starting.

  In this embodiment, the fuel gas reformed by the steam reformer RFS is circulated and introduced into the dispersion chamber DB, and the fuel gas reformed by the partial oxidation reformer RFP is circulated and dispersed. Although the case where the pipe to be introduced into the chamber DB is provided in parallel has been described, the present invention is not limited thereto, and the pipe for introducing the fuel gas from the steam reformer RFS to the dispersion chamber DB and the partial oxidation reformer RFP. The piping introduced into the dispersion chamber DB may be arranged in series.

ADU: Auxiliary unit C: Container CE: Fuel cell CS: Fuel cell system controller DB: Dispersion chamber FC: Fuel cell FC1: Power generation chamber FC2: Combustion chamber FCM: Fuel cell module FCS: Fuel cell system FP: Fuel supply Part FP4, FP5, FP6, FP7: Gas shut-off valve HI: Heat insulating material POX: Partial oxidation reforming reaction PP1, PP2: Pipe RF: Reformer RF1: Reforming part RF2: Evaporating part RFP: Partial oxidation reformer RFP1 : Start partial oxidation reformer RFP2: Stop partial oxidation reformer RFS: Steam reformer SC: Fuel cell system controller SR: Steam reforming reaction

Claims (7)

A fuel cell system including a solid electrolyte fuel cell,
A power generation chamber in which a plurality of fuel cells are disposed, a combustion chamber disposed above the power generation chamber, and a first reformer disposed above the combustion chamber and performing steam reforming of fuel gas And a second reformer that performs partial oxidation reforming of the fuel gas in the start mode for starting the fuel cell system and in the operation stop mode for stopping the power generation, and a fuel cell module,
In the power generation chamber, the fuel gas reformed by the first reformer and the second reformer is introduced from below,
The second reformer, a shall be disposed outside the lower container forming the power generating chamber and the combustion chamber,
The container further includes a dispersion chamber that is disposed below the power generation chamber and disperses the fuel gas reformed by the first reformer and the second reformer and supplies the fuel gas to the power generation chamber. And the second reformer is disposed at a position outside the lower surface of the dispersion chamber .   The fuel cell system according to claim 1, wherein the second reformer is disposed in the vicinity of the power generation chamber.   The fuel cell system according to claim 1, wherein the second reformer is disposed via a heat insulating material.   The fuel cell system according to any one of claims 1 to 3, wherein a heat insulating material is provided in a pipe for supplying the fuel gas reformed by the second reformer to the container. 2. The fuel cell system according to claim 1, wherein the second reformer is disposed at a central portion at a position on the outer side of the lower surface of the dispersion chamber . The second reformer includes a startup partial oxidation reformer that performs partial oxidation reforming of the fuel gas during a startup mode of the fuel cell system, and the fuel gas during a shutdown mode of the fuel cell system. A partial oxidation reformer for stopping that performs partial oxidation reforming of
  2. The fuel cell system according to claim 1, wherein the partial oxidation reformer for stop is disposed at a position farther from the container than the partial oxidation reformer for start-up. A plurality of pipes are provided downstream of the second reformer and communicate with the second reformer and the container, and are arranged at a position closest to the container among the plurality of pipes. The fluid discharged from the second reformer during the start-up mode of the fuel cell system is passed through the pipe that is in the fuel cell system, and the operation of the fuel cell system is stopped in the pipe that is disposed farthest from the container The fuel cell system according to any one of claims 1 to 5, wherein the fluid discharged from the second reformer is passed during the mode.

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