JP2010238591A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of continuing operation as long as possible even if there is malfunction of a water level detecting means installed at a tank to store water in order to supply it to a reformer. <P>SOLUTION: Separately from an initial check during an operation starting period, just on the supply of exhaust gas to a heat exchanger HW1, this fuel cell system FCS carries out an abnormality judging treatment to determine presence/absence of abnormalities of a plurality of water level sensors DS5a, Ds5b, DS5c, DS5d to detect water levels of water storage tanks WP2a, WP2b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a solid oxide fuel cell (SOFC) cell.

  Conventionally, as such a fuel cell system, a solid oxide fuel cell (hereinafter also referred to as SOFC) cell has a bottomless or bottomed cylindrical shape or the like, and a fuel gas containing hydrogen inside or outside the cell. It is known that a power generation reaction is performed by passing an oxidant gas (air) on the opposite side. The fuel gas is obtained by reforming a gas to be reformed such as city gas, and a so-called steam reforming reaction (hereinafter also referred to as SR) is performed in a reformer that performs the reforming. . A technique for supplying pure water to the reformer has been proposed (see, for example, Patent Document 1 below).

  The following Patent Document 1 describes that pure water is rapidly supplied to the reformer. Patent Document 2 below discloses a technique for supplying water to a tank so that the operation of the fuel cell system can be continued even when there is a water outage.

JP 2008-135271 A JP 2008-53209 A

  By the way, since SOFC has high power generation efficiency and uses less fuel gas, there is an advantage that both non-reformed gas and water vapor are very small. For example, in the steam reforming reaction SR described above, the amount of water required is about 8 ml per minute.

  On the other hand, paying attention to the start-up method peculiar to the fuel cell system including SOFC, the steam reforming reaction SR described above is an endothermic reaction. Therefore, if the steam reforming reaction SR is performed immediately at the start-up, the temperature of the SOFC module Does not rise and does not rise to a stable operating temperature. Therefore, at the beginning of startup, only air and the gas to be reformed are sent to the reformer to perform a partial oxidation reforming reaction (hereinafter also referred to as POX) as an exothermic reaction. Comparing the partial oxidation reforming reaction POX and the steam reforming reaction SR, the hydrogen generation efficiency is higher in the steam reforming reaction SR, so that the steam reforming reaction SR gradually increases as the temperature of the SOFC module rises. There is a need to migrate. Therefore, when paying attention to the amount of water supplied to the reformer, it is necessary to smoothly shift from a state where no water is used to a water supply of about 8 ml per minute. In the middle of such a transition, the autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX and the steam reforming reaction SR are used together may be advanced.

  In view of the circumstances described above, it should be preferable to gradually increase the amount of water supplied to the reformer from the smallest possible amount, but it is extremely difficult to actually supply such water. As described above, the fuel cell system including the SOFC is not only highly efficient but also extremely high in temperature (about 700 ° C.). For example, when restarting after starting and stopping once, the temperature of the water supply pipe for supplying water to the reformer becomes high, and it is highly possible that the water in the water supply pipe has evaporated. It is extremely difficult to accurately supply a small amount of water to a water supply pipe in such a state where there is no water at all, but if there is not enough water if it is not possible to accurately supply water to the reformer In some cases, carbon deposition may occur in the reformer and the cell or catalyst may be damaged. When there is a large amount of water, the temperature of the fuel cell does not rise and stable operation may not be possible. It is important to supply a small amount of water accurately. In order to accurately supply a small amount of water, it is also necessary to devise a flow rate measurement method and control based on the measurement results, resulting in problems with various sensors. It is also important how to control the case.

  The present invention has been made in view of such problems, and an object of the present invention is a fuel cell system including SOFC, in which a problem occurs in the water storage state in a tank for storing water to be supplied to a reformer. It is an object of the present invention to provide a fuel cell system that can continue operation as much as possible even if a situation such as a malfunction occurs in the water level detection means provided in the tank.

  In order to solve the above-described problems, a fuel cell system according to the present invention is a fuel cell system including a solid electrolyte fuel cell, and performs reforming of steam of fuel gas supplied to the fuel cell. A heat exchanger for exchanging heat with the exhaust gas discharged by burning the fuel gas that has passed through the fuel cell, water supply means for supplying water to the reformer, and the water supply means Control means for controlling the water supply means, the water supply means for storing dew condensation water in the heat exchanger as water to be supplied to the reformer, water level detection means for detecting the water level of the water storage tank, A pump that pumps the water stored in the water storage tank to the reformer, and the control means supplies the exhaust gas to the heat exchanger separately from the initial check during the operation start period. Combined with the water And executes an abnormality determination process for determining an abnormality presence or absence of the detection means.

  A fuel cell system according to the present invention includes a heat exchanger that exchanges heat with exhaust gas discharged from a fuel cell, and a water storage tank that stores condensed water in the heat exchanger as water to be supplied to the reformer. Yes. The water stored in the water storage tank is pumped to the reformer by a pump. Since the water supplied to the reformer needs to be supplied stably, a water level detecting means for detecting the water level of the water storage tank is provided. In the present invention, in addition to the initial check during the operation start period, an abnormality determination process for determining whether or not the water level detection means is abnormal is performed in accordance with the supply of exhaust gas to the heat exchanger. The abnormality determination process can be executed at an arbitrary timing after a predetermined time from the start of gas supply. By controlling the timing for executing the abnormality determination process in this way, it becomes possible to execute the abnormality determination process in accordance with the timing at which dew condensation in the heat exchanger starts and condensation water will accumulate in the water storage tank. Even when only dew condensation water is stored without supplying clean water to the water storage tank, it is possible to accurately and quickly determine whether the water level detection means is abnormal.

  In the fuel cell system according to claim 2 of the present application, at the time of start-up, the reforming reaction in the reformer is started from the partial oxidation reforming reaction, and transitioned to the reforming reaction using water, The control means executes the abnormality determination process when a partial oxidation reforming reaction is occurring in the reformer.

  In the present invention, at the start-up, the reforming reaction in the reformer starts from the partial oxidation reforming reaction, and transitions to the reforming reaction using water such as autothermal reforming reaction or steam reforming reaction. A quality reaction is a reaction that does not require water in the reformer. Therefore, by performing abnormality determination processing at the stage where the partial oxidation reforming reaction is occurring in the reformer, the water level is detected at a stage where condensed water can be stored and water is not yet required in the reformer. The presence or absence of abnormality of the means can be determined, and reliable abnormality determination can be executed at an optimal timing. Furthermore, by continuing the partial oxidation reforming reaction, the heated fuel gas can be supplied to the fuel cell, and the fuel cell can be heated together with the reformer.

  In the fuel cell system according to claim 3 of the present application, at the time of start-up, the reforming reaction in the reformer is started from the partial oxidation reforming reaction, and transitioned to the reforming reaction using water, The control means performs the abnormality determination process when a partial oxidation reaction is occurring in the reformer, and the water level detection means does not detect the water level even if the reformer temperature exceeds a predetermined temperature. Is characterized in that the reforming reaction using water is controlled so as not to occur in the reformer.

  As described above, the present invention starts the reforming reaction in the reformer from the partial oxidation reforming reaction at the time of start-up and makes a transition to a reforming reaction using water such as an autothermal reforming reaction or a steam reforming reaction. The partial oxidation reforming reaction is a reaction that does not require water in the reformer. Therefore, by performing abnormality determination processing at the stage where the partial oxidation reforming reaction is occurring in the reformer, the water level is detected at a stage where condensed water can be stored and water is not yet required in the reformer. The presence or absence of abnormality of the means can be determined, and reliable abnormality determination can be executed at an optimal timing. Furthermore, if the water level detection means still does not detect the water level even if the reformer temperature exceeds the predetermined temperature, whether the water level detection means itself is abnormal or whether condensed water cannot be stored. Since it is unknown, the transition to the reforming reaction using water is limited, and carbon deposition in the reformer due to water shortage is prevented.

In the fuel cell system according to claim 4 of the present application, at the time of start-up, the reforming reaction in the reformer is started from the partial oxidation reforming reaction, and transitioned to the reforming reaction using water,
The water supply means has a reverse osmosis membrane for making the water supplied to the reformer pure water, and the water storage tank is a first tank disposed upstream of the reverse osmosis membrane; And a second tank disposed on the reformer side, which is downstream from the reverse osmosis membrane, and pumps water stored in the first tank to the second tank through the reverse osmosis membrane. And a second pump for pumping the water stored in the second tank to the reformer, and the water level detecting means is provided in each of the first tank and the second tank. The control means executes the abnormality determination process at a stage where the partial oxidation reforming reaction is occurring in the reformer, and the second tank even if the reformer temperature exceeds a predetermined temperature. The water level detecting means provided in the If not come out, characterized in that the forcibly supplying water to the first driven pump to the second tank.

  In this aspect, when the water level detection means provided in the second tank on the reformer side among the first tank and the second tank arranged with the reverse osmosis membrane interposed therebetween does not detect the water level, Since one pump is driven to forcibly supply water from the first tank through the reverse osmosis membrane to the second tank, the water level is detected if there is no abnormality in the water level detection means provided in the second tank. The start-up operation can be continued without deferring the transition to the reforming reaction using water.

  In the fuel cell system according to claim 5 of the present application, the control means controls the partial oxidation reforming reaction in the reformer when controlling the reforming reaction using the water so as not to occur in the reformer. The temperature suppression control is performed so that the temperature does not rise above a predetermined temperature.

  According to this aspect, in the state where the transition from the partial oxidation reforming reaction to the reforming reaction using water is suspended, the temperature suppression control is executed so that the temperature in the reformer does not rise above a predetermined temperature. Therefore, it is possible to prevent an adverse effect on the fuel battery cell due to an excessive temperature rise.

  In the fuel cell system according to claim 6 of the present application, the control means executes the temperature suppression control by suppressing a supply amount of the reformed gas supplied to the reformer.

  According to this aspect, since the temperature suppression control is executed by suppressing the supply amount of the reformed gas supplied to the reformer, the temperature of the reformer is more reliably suppressed from rising above a predetermined temperature. It is possible to reliably prevent adverse effects on the fuel cell due to excessive temperature rise. In addition, since it is not necessary to separately provide a cooling device for cooling the reformer, the entire fuel cell system can be reduced in size.

  In the fuel cell system according to claim 7 of the present application, when the state in which the water level detection unit does not detect the water level continues for a predetermined time or more, the control unit determines that an abnormality has occurred in the water level detection unit. Processing control is executed.

  In the fuel cell system of the present invention, it is considered that if the supply of the exhaust gas to the heat exchanger is continued for a predetermined time, the condensed water is likely to be accumulated in the water storage tank. Therefore, in this aspect, when the state in which the water level detection means does not detect the water level continues for a predetermined time or longer, it is determined that an abnormality has occurred in the water level detection means. By making such a determination, it is possible to shift to abnormality processing control on the assumption that an abnormality has occurred in the water level detection means, and an appropriate response can be taken.

  In the fuel cell system according to claim 8 of the present application, the control means controls the temperature so as to suppress the oxidation of the fuel cell constituting the fuel cell when the water level detection means does not detect the water level. In the abnormal process control, the cooling stop process is executed by reducing the supply amount of the reformed gas to the reformer.

  Since it has been found that an abnormality has occurred in the water level detecting means as described above, in this aspect, the temperature is controlled so as to suppress the oxidation of the fuel battery cells constituting the fuel cell, and the abnormality processing control is performed. In this case, the supply of the gas to be reformed to the reformer is lowered and the cooling stop process is executed, so that each part of the fuel cell is safely stopped without being damaged.

  According to the present invention, a problem such as a problem occurs in the water storage state in a tank for storing water to be supplied to the reformer, or a problem occurs in the water level detection means provided in the tank. However, it is possible to provide a fuel cell system that can continue operation as much as possible.

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 graph which shows the temperature of each part at the time of starting of the fuel cell system shown in FIG. 1, and the control voltage of each part. In the fuel cell system shown in FIG. 1, it is a schematic block diagram which shows the structure of the part which supplies water to a fuel cell module. It is the flowchart which showed the basic flow for supplying water to the reformer shown in FIG.1 and FIG.4. It is the flowchart which showed the flow for judging abnormality of the water level sensor shown in FIG.2 and FIG.4. FIG. 7 is a flowchart showing a flow for setting a flag used in the flowchart shown in FIG. 5 when a determination is made based on the flowchart shown in FIG. 6. It is the flowchart which showed the flow which withholds transfer to the 1st autothermal reforming reaction ATR1 from the partial oxidation reforming reaction POX. It is the flowchart which showed the flow which performs a 2nd initial check.

  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 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. 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), steam reforming reaction (SR; Steam Reforming), It is selectively executed according to the driving situation (details will be described later). 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 detects whether or not CO in exhaust gas that is originally discharged to the outside through an exhaust gas passage or the like has leaked to an external housing (not shown) that covers the fuel cell module FCM and the auxiliary unit ADU. It is for detection. The combustible gas detector GD1 is for detecting gas leakage, and is attached to the fuel cell module FCM and the auxiliary unit ADU.

  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 by the heater AH2 as power generation air 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 adjusted for diversion by the flow rate adjustment unit WP1 and supplied to the reformer RF of the fuel cell module FCM.

  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.

  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, 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 when the fuel cell system FCS is started.

  In the start-up mode of the fuel cell system FCS in the present embodiment, combustion operation, partial oxidation reforming reaction POX, first autothermal reforming reaction ATR1, second autothermal reforming reaction ATR2, and steam reforming reaction The reforming reaction is proceeding while sequentially switching to SR. 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 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 heat supply to the fuel cell module FCM is required. It is a quality reaction. If attention is paid only to the partial oxidation reforming reaction POX, the space velocity is set high. For example, when a reformer dedicated to the partial oxidation reforming reaction POX is provided by dividing the reformer RF, A dedicated reformer can be reduced in size.

The steam reforming reaction SR is a reforming reaction performed by supplying a 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 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 an intermediate reforming reaction between the partial oxidation reforming reaction POX and the steam reforming reaction SR. The reforming reaction is performed by supplying a reforming gas, air, and water vapor 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)
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 this 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 steam is reformed by supplying the water after the temperature rises. The second autothermal reforming reaction ATR2 closer to the reaction SR is performed later.

  Returning to FIG. 3, the start-up 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 an igniter to execute a combustion operation (it is ignited by spontaneous ignition and performs a combustion operation depending on conditions). In this case, the flow rate of reforming air supplied to the reformer RF is 10.0 L (liters) per minute, and the flow rate of the reformed gas supplied to the reformer RF is 6.0 L per minute. Further, the flow rate adjustment unit AP1b is controlled so that the flow rate of the power generation air supplied to the power generation chamber FC1 is 100.0 L per minute throughout the start-up mode. 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 becomes ready for POX operation, so the partial oxidation reforming reaction POX proceeds at about 300 ° C. To do. Since the partial oxidation reforming reaction POX is an exothermic reaction, the temperature of each part rises. 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. Specifically, the flow rate of reforming air supplied to the reformer RF is 18.0 L / min, and the flow rate of reformed gas supplied to the reformer RF is 5.0 L / min.

  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 to 8.0 L / min, and the flow rate of reformed gas supplied to the reformer RF is 5. Maintain 0L. Further, 1.0 ml of minute pure water per minute is supplied to the reformer RF. The autothermal reforming reaction ATR is a reaction in which the partial oxidation reforming reaction ATR and the steam reforming reaction SR are mixed. Since the internal thermal balance is achieved, the reaction proceeds while the heat is self-supporting in the reformer RF. To do. 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 is a reaction in which heat generation is dominant. In the first autothermal reforming reaction ATR1, the temperature of the cell stack constituted by the fuel cell CE is about 250 ° C. to about 400 ° C.

  Subsequently, the second autothermal reforming reaction ATR2 is performed on condition that the temperature of the reformer RF is 600 ° C. or higher and the temperature of the cell stack constituted by the fuel cell CE exceeds about 400 ° C. Transition. In the second autothermal reforming reaction ATR2, the flow rate of reforming air supplied to the reformer RF is reduced to 4.0 L / min, and the flow rate of reformed gas supplied to the reformer RF is also 4. Reduce to 0L. Further, a minute amount of pure water of 3.0 ml per minute is supplied to the reformer 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 the second autothermal reforming reaction ATR2, the temperature of the evaporation part RF2 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 cells CE exceeds about 600 ° C. In the steam reforming reaction SR, the reforming air supplied to the reformer RF is shut off, and the flow rate of the reformed gas supplied to the reformer RF is reduced to 3.0 L / min. Further, 8.0 ml of pure water per minute is supplied to the reformer RF. Since the 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. 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 with a steam reforming reaction SR with high reforming efficiency. Strictly speaking, the steam reforming reaction SR itself is performed at about 400 ° C. to 800 ° C., but in the combination with the fuel cell CE, the reaction is set so that the reaction proceeds at about 500 ° C. to 700 ° C.

  In this embodiment, at the start of the first autothermal reforming reaction ATR1 shown in FIG. 3, a very small amount of water of 1 cc per minute is supplied to the reformer SR. One embodiment for accurately supplying such a small amount of water will be described with reference to FIG. FIG. 4 is a diagram schematically showing a piping path from the water storage tank WP2 shown in FIG. 1 to the fuel cell module FCM via the flow rate adjustment unit WP1.

  As shown in FIG. 4, the water storage tank WP2 includes a first water storage tank WP2a and a second water storage tank WP2b. A water supply pipe 10 to which clean water is supplied is connected to the first water storage tank WP2a. The water supply pipe 10 is provided with an electromagnetic valve 101. By opening and closing the electromagnetic valve 101, it is possible to supply or stop clean water to the first water storage tank WP2a. The 1st water storage tank WP2a is arrange | positioned so that the water condensed in the heat exchanger HW1 of the warm water manufacturing apparatus HW can be received. Therefore, the first water storage tank WP2a can store water condensed in the heat exchanger HW1 of the hot water production apparatus HW, and can supply water from the water supply pipe 10 when the amount of water is insufficient. The first water storage tank WP2a is provided with a heater H1, so that the water in the first water storage tank WP2a is not frozen.

  A pump 111 and a reverse osmosis membrane 20 are provided in the pipe line 11 connecting the first water storage tank WP2a and the second water storage tank WP2b. The pump 111 can feed 1 L of water per minute from the first water storage tank WP2a to the second water storage tank WP2b. Since the pump 111 pushes water through the reverse osmosis membrane 20 to the second water storage tank WP2b, the water that has passed through the reverse osmosis membrane 20 becomes pure water and is stored in the second water storage dunk WP2b. The second water storage tank WP2b is provided with a heater H2, so that the water in the second water storage tank WP2b is not frozen.

  A pulse pump 131 and a water flow rate sensor DS6 are provided in the pipe line 13 connecting the second water storage tank WP2b and the fuel cell module FCM. Accordingly, the pipeline 13 includes a pipeline 13a from the second water storage tank WP2b to the pulse pump 131, a pipeline 13b from the pulse pump 131 to the water flow sensor DS6, and a pipe from the water flow sensor DS6 to the fuel cell module FCM. It is comprised by the path | route 13c. A heater H3 is provided in the vicinity of the second water storage tank WP2b of the pipe line 13a so that water in the pipe line 13a, particularly water at a position away from the fuel cell module FCM, is not frozen.

  The first water storage tank WP2a is provided with a high water level sensor DS5a and a low water level sensor DS5b corresponding to the water level sensor DS5 described above. The high water level sensor DS5a (high water level detecting means) is a float sensor for detecting that water has been supplied to the high water level of the first water storage tank WP2a. When the water level rises to the attached position, the Hi signal is output. Output. The low water level sensor DS5b (low water level detection means) is a float sensor for detecting that water has been supplied to the low water level of the first water storage tank WP2a. When the water level rises to the attached position, the Hi signal is output. Output. The high water level sensor DS5a and the low water level sensor DS5b output a Lo signal when the water surface has not reached the position where the high water level sensor DS5a and the low water level sensor DS5b are attached.

  The second water storage tank WP2b is provided with a high water level sensor DS5c (high water level detecting means) and a low water level sensor DS5d (low water level detecting means) corresponding to the water level sensor DS5 described above. The high water level sensor DS5c is a float sensor for detecting that water has been supplied up to the high water level of the second water storage tank WP2b, and outputs a Hi signal when the water level rises to the attached position. The low water level sensor DS5c is a float sensor for detecting that water has been supplied to the low water level of the second water storage tank WP2b, and outputs a Hi signal when the water level rises to the attached position. The high water level sensor DS5c and the low water level sensor DS5d output a Lo signal when the water surface has not reached the position where the high water level sensor DS5c and the low water level sensor DS5d are attached.

  Subsequently, in the fuel cell system FCS of the present embodiment, the combustion operation is performed from the start of the operation, and after the partial oxidation reforming reaction POX is performed in the reformer RF, the process proceeds to the first autothermal reforming reaction ATR1. Control of water supply to the reformer RF will be described. FIG. 5 is a flowchart showing a basic flow for supplying water to the reformer RF in this case. In the description of FIG. 5, if the flag F is “0”, it indicates that water is normally stored in the first water storage tank WP2a and the second water storage tank WP2b and normal control is possible. If the flag F is “5”, it is possible to determine that there is water in the first water storage tank WP2a and the second water storage tank WP2b although an abnormality has occurred in the water supply system, and the operation is continued by the estimated supply control. Indicates that it is possible. If the flag F is “6”, it is impossible to determine that there is an abnormality in the water supply system and there is water in the first water storage tank WP2a and the second water storage tank WP2b. Indicates that the operation is to be stopped. If the flag F is “7”, an abnormality occurs in the water supply system, and it is impossible to supply water to the first water storage tank WP2a and the second water storage tank WP2b, and the operation of the fuel cell system FCS is stopped. It shows that

  In step S01, the fuel cell system FCS starts operation, performs combustion operation, and then performs a partial oxidation reforming reaction POX in the reformer RF, satisfying a predetermined condition and using a steam reforming reaction (this implementation) In the case of the embodiment, it is determined whether it is time to execute the first autothermal reforming reaction ATR1) as described above. If it is determined in step S01 that the conditions for shifting to the first autothermal reforming reaction ATR1 are not satisfied, the process returns. If it is satisfied, the process proceeds to step S02.

  In step S02, it is determined whether the flag F is “0”. If the flag F is “0”, the process proceeds to step S03. If the flag F is not “0”, the process proceeds to step S06. If the flag F is “0”, normal control is possible. Therefore, in step S03, it is determined whether it is the start timing of the first autothermal reforming reaction ATR1. In step S03, if it is not the start timing of the first autothermal reforming reaction ATR1, it is determined that the first autothermal reforming reaction ATR1 has already been performed, the process proceeds to step S04, and the first autothermal reforming reaction is performed. If it is the start timing of the reaction ATR1, the process proceeds to step S09.

  In step S04, the pulse pump 131 is controlled so that the flow rate detected by the water flow rate sensor DS6 becomes the flow rate Q required in the first autothermal reforming reaction ATR1. In step S05 subsequent to step S04, it is determined whether or not the detected pressure of the reformer internal pressure sensor DS4 provided in the reformer RF is small. If the pressure detected by the reformer pressure sensor DS4 provided in the reformer RF is small and fluctuates, a small amount of water is pulsatingly supplied to the reformer RF with little water by the pulse pump 131. And return. If the detected pressure of the reformer internal pressure sensor DS4 provided in the reformer RF does not fluctuate little, it is determined that a small amount of water is not supplied into the reformer RF, and the process proceeds to step S08. . In step S08, the flag F is set to “7”, and processing for urgently stopping the operation of the fuel cell system FCS is executed.

  If it is determined in step S03 that it is the start timing of the first autothermal reforming reaction ATR1, in step S09, water is sent out toward the reformer RF with the supply amount of the pulse pump 131 as the maximum value. In step S10 subsequent to step S09, it is determined whether or not the pressure in the reformer RF varies greatly. If the pressure in the reformer RF has greatly fluctuated, it is determined that water has started to be pumped by the pulse pump 131, and the process proceeds to step S11. If the pressure in the reformer RF has not fluctuated significantly, The process proceeds to step S13.

  In step S11, it is determined whether the amount of water detected by the water flow sensor DS6 has changed. If the amount of water detected by the water flow sensor DS6 changes, it is determined that the water sent from the pulse pump 131 has reached the water flow sensor DS6, and the process proceeds to step S12, where the amount of water detected by the water flow sensor DS6 changes. If not, the process proceeds to step S13.

  In step S12, the pulse pump 131 is controlled so that the flow rate of the water flow rate sensor DS6 becomes the flow rate Q required in the first autothermal reforming reaction ATR1, and the process returns.

  In step S13, it is determined whether the predetermined time has elapsed and the time is up. If the predetermined time has not elapsed, the process returns. If the predetermined time has elapsed, the process proceeds to step S14. In step S14, the flag F is set to “7”, and processing for urgently stopping the operation of the fuel cell system FCS is executed.

  Next, a flow for determining whether or not an abnormality has occurred in any of the high water level sensor DS5a, the low water level sensor DS5b, the high water level sensor DS5c, and the low water level sensor DS5d will be described with reference to the flowchart shown in FIG. To do. In the description of FIG. 6, if the flag F is “0”, it means that no abnormality has occurred in any of the water level sensors (high water level sensor DS5a, low water level sensor DS5b, high water level sensor DS5c, low water level sensor DS5d). Show. If the flag F is “2”, it indicates that the high water level sensor DS5a of the first water storage tank WP2a is abnormal. If the flag F is “1”, it indicates that the low water level sensor DS5b of the first water storage tank WP2a is abnormal. If the flag F is “4”, it indicates that the high water level sensor DS5c of the second water storage tank WP2b is abnormal. If the flag F is “3”, it indicates that the low water level sensor DS5d of the second water storage tank WP2b is abnormal. 6 to 9, “SW1” indicates the high water level sensor DS5a, “SW2” indicates the low water level sensor DS5b, “SW3” indicates the high water level sensor DS5c, and “SW4” indicates the low level. The water level sensor DS5d is shown. “Pump 1” indicates the pump 111, “Tank 1” indicates the first water storage tank WP2a, and “Tank 2” indicates the second water storage tank WP2b.

  In step S21, it is determined whether a Hi signal is output from all of the high water level sensor DS5a, the low water level sensor DS5b, the high water level sensor DS5c, and the low water level sensor DS5d. If the Hi signal is output from all the sensors, all the sensors detect the water level, so the process proceeds to step S32. If Hi signals are not output from all sensors, the process proceeds to step S22.

  In step S22, it is determined whether the Lo signal is output from the low water level sensor DS5b of the first water storage tank WP2a. If the Lo signal is output from the low water level sensor DS5b of the first water tank WP2a, the process proceeds to step S23. If the Lo signal is not output from the low water level sensor DS5b of the first water tank WP2a, the process proceeds to step S34. Proceed to processing.

  In step S23, it is determined whether a Hi signal is output from the high water level sensor DS5a of the first water storage tank WP2a. If the Hi signal is output from the high water level sensor DS5a of the first water storage tank WP2a, the process jumps to J1 to proceed to the process of Step S43, and the Hi signal must be output from the high water level sensor DS5a of the first water storage tank WP2a. If so, the process proceeds to step S24.

  In step S24, water is supplied to the first water storage tank WP2a, and the process proceeds to step S25.

  In step S34, it is determined whether the Lo signal is output from the high water level sensor DS5a of the first water storage tank WP2a. If the Lo signal is output from the high water level sensor DS5a of the first water storage tank WP2a, the process proceeds to step S24 described above. If the Lo signal is not output from the high water level sensor DS5a of the first water storage tank WP2a, the process proceeds to step S35. Proceed to processing.

  In step S35, it is determined whether the Lo signal is output from the low water level sensor DS5d of the second water storage tank WP2b. If the Lo signal is output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S36. If the Lo signal is not output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S37. Proceed to processing.

  In step S36, it is determined whether a Hi signal is output from the high water level sensor DS5c of the second water storage tank WP2b. If the Hi signal is output from the high water level sensor DS5c of the second water storage tank WP2b, the process jumps to J2 to proceed to step S41, and the Hi signal must be output from the high water level sensor DS5c of the second water storage tank WP2b. If so, the process jumps to J3 and proceeds to step S29.

  In step S37, it is determined whether the Lo signal is output from the high water level sensor DS5c of the second water storage tank WP2b. If the Lo signal is output from the high water level sensor DS5c of the second water storage tank WP2b, the process jumps to J3 and proceeds to the processing of Step S29, and the Lo signal is output from the high water level sensor DS5c of the second water storage tank WP2b. If it is full, return.

  In step S25, it is determined whether a Hi signal is output from the low water level sensor DS5b of the first water storage tank WP2a. If the Hi signal is output from the low water level sensor DS5b of the first water storage tank WP2a, the process proceeds to step S26. If the Hi signal is not output from the low water level sensor DS5b of the first water storage tank WP2a, the process proceeds to step S42. Proceed to processing.

  In step S42, it is determined whether a predetermined time has elapsed and time is up. If the predetermined time has not elapsed, the process returns. If the predetermined time has elapsed, the process proceeds to step S43.

  In step S43, it is determined that the low water level sensor DS5b of the first water storage tank WP2a is abnormal, the flag F is set to “1”, and the process returns. This is because, although water is supplied to the first water storage tank WP2a in step S24, a Hi signal is not output from the low water level sensor DS5b even after a predetermined time has elapsed, or a Lo signal is output from the low water level sensor DS5b in step S22. This is because the Hi signal is output from the high water level sensor DS5a in step S23. Note that, in the process of step S43, it is set in a pseudo manner that the Hi signal is output from the low water level sensor DS5b, and the process returns.

  In step S26, it is determined whether a Hi signal is output from the high water level sensor DS5a of the first water storage tank WP2a. If the Hi signal is output from the high water level sensor DS5a of the first water tank WP2a, the process proceeds to step S27. If the Hi signal is not output from the high water level sensor DS5a of the first water tank WP2a, the process proceeds to step S38. Proceed to processing.

  In step S38, it is determined whether the predetermined time has elapsed and time is up. If the predetermined time has not elapsed, the process returns. If the predetermined time has elapsed, the process proceeds to step S39.

  In step S39, it is determined that the high water level sensor DS5a of the first water storage tank WP2a is abnormal, the flag F is set to “2”, and the process returns. This is because the Hi signal is output from the low water level sensor DS5b after supplying water to the first water storage tank WP2a in Step S24, but the Hi signal is not output from the high water level sensor DS5a even after a predetermined time has elapsed. is there. In the case of the process of step S39, it is set in a pseudo manner that the Hi signal is output from the high water level sensor DS5a, and the process returns.

  In step S27, water supply to the first water storage tank WP2a is stopped. In step S28 following step S27, it is determined whether a Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b. If the Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b, the process returns. If the Hi signal is not output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to Step S29.

  In step S29, the pure water pump 111 is driven to supply water from the first water storage tank WP2a to the second water storage tank WP2b. In step S30 following step S29, it is determined whether the Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b. If the Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S31. If the Hi signal is not output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S44. move on.

  In step S44, it is determined whether the predetermined time has elapsed and time is up. If the predetermined time has not elapsed, the process returns. If the predetermined time has elapsed, the process proceeds to step S45.

  In step S45, it is determined that the low water level sensor DS5d of the second water storage tank WP2b is abnormal, the flag F is set to “3”, and the process returns. This is because although the water is supplied from the first water storage tank WP2a to the second water storage tank WP2b in step S29, the Hi signal is not output from the low water level sensor DS5d even if a predetermined time elapses. In the process of step S45, it is set in a pseudo manner that the Hi signal is output from the low water level sensor DS5d, and the process returns.

  In step S31, it is determined whether a Hi signal is output from the high water level sensor DS5c of the second water storage tank WP2b. If the Hi signal is output from the high water level sensor DS5c of the second water storage tank WP2b, the process proceeds to Step S32. If the Hi signal is not output from the high water level sensor DS5c of the second water storage tank WP2b, the process of Step S40 is performed. Proceed to

  In step S40, it is determined whether a predetermined time has elapsed and time is up. If the predetermined time has not elapsed, the process returns. If the predetermined time has elapsed, the process proceeds to step S41.

  In step S41, it is determined that the high water level sensor DS5c of the second water storage tank WP2b is abnormal, the flag F is set to “4”, and the process returns. This is because the water is supplied from the first water storage tank WP2a to the second water storage tank WP2b in step S29, and the Hi signal is output from the low water level sensor DS5d, but the high water level sensor DS5c even if a predetermined time has passed. This is because the Hi signal is not output from. Note that, in the process of step S41, the process is returned with a pseudo setting that the Hi signal is output from the high water level sensor DS5c.

  In step S32, it is determined whether or not a pseudo-set Hi signal is included. If the pseudo-set Hi signal is included, the process proceeds to step S46. If the pseudo-set Hi signal is not included, the process proceeds to step S48.

  In step S46, it is set whether to perform an abnormality handling operation or an estimated supply operation. In step S47, a flag F corresponding to the water level sensor in which an abnormality has occurred is set and the process returns. The flag F is set to one or more of “1”, “2”, “3”, and “4”. In step S48, it is set to perform normal operation control. In step S49, the flag F is set to “0” and the process returns.

  Next, the flow for setting the flag used in the flow shown in FIG. 5 when the flag relating to the abnormality of the water level sensor is set based on the flow shown in FIG. 6 will be described with reference to the flowchart shown in FIG.

  In step S51, it is determined whether the flag F is “0”. If the flag F is “0”, the process proceeds to step S57. If the flag F is not “0”, the process proceeds to step S52. In step S57, normal operation is permitted, the flag F is set to “0”, and the process returns.

  In step S52, it is determined whether or not the flag F is set in all of “1”, “2”, “3”, and “4”. If the flag F is set for all “1”, “2”, “3”, and “4”, the process proceeds to step S58, and the flag F is set for all “1”, “2”, “3”, and “4”. If not set, the process proceeds to step S53.

  In step S58, the water level sensors (high water level sensor DS5a, low water level sensor DS5b, high water level sensor DS5c, low water level sensor DS5d) are all in a state of failure at the same time, or no water is supplied at all. As a water supply system abnormality, the flag F is set to “6” and the process returns.

  In step S53, it is determined whether any one of “1”, “2”, “3”, and “4” is set. If the flag F is set to two to three instead of any one of “1”, “2”, “3”, and “4”, the process proceeds to step S59, and the flag F is set to “1”, “2”, “3”. If any one of “4” is set, the process proceeds to step S54.

  In step S59, since any two to three of the water level sensors (high water level sensor DS5a, low water level sensor DS5b, high water level sensor DS5c, low water level sensor DS5d) are in failure at the same time, Return flag F as “6”. In this embodiment, when any two to three of the water level sensors (the high water level sensor DS5a, the low water level sensor DS5b, the high water level sensor DS5c, and the low water level sensor DS5d) fail at the same time, the water supply system is abnormal. The flag F is set to “6”, but if any one of the water level sensors (high water level sensor DS5a, low water level sensor DS5b, high water level sensor DS5c, low water level sensor DS5d) is not abnormal, water is actually used. Since the supply of water from the supply system is not interrupted, it is possible to adopt a mode in which it is determined that water is supplied.

  In step S54, the flag F is set to “5” as allowing the estimated supply operation. In the case of this embodiment, both the first water storage tank WP2a and the second water storage tank WP2b are tanks having a maximum full water volume of 300 ml and capable of overflowing. This is set as the amount of water that can continue to supply 1 ml of water per minute for 4 hours or more so that the stop operation by steam reforming is possible even when the water is shut off.

  In step S55 following step S54, if the low water level sensor DS5b or the low water level sensor DS5d is abnormal, it is changed to the estimated supply operation by the low water level estimation supply control in which the water level is estimated by the high water level sensor DS5a or the high water level sensor DS5c. . When the estimated supply operation is continued, the maximum amount of water used is 8 ml per minute. Accordingly, there is a possibility that 300 ml of water may be used up in about 35 minutes. Therefore, water supply is performed 25 minutes after the Hi signal output of the high water level sensor DS5a or the high water level sensor DS5c, and the full water state is maintained. By this operation, it is possible to ensure that water is always contained in the first water storage tank WP2a and the second water storage tank WP2b, and safety can be maintained.

  In step S56 following step S55, when the high water level sensor DS5a or the high water level sensor DS5c is abnormal, it is changed to the estimated supply operation by the high water level estimation supply control in which the water level is estimated by the low water level sensor DS5b or the low water level sensor DS5d. . In the case of the present embodiment, both the first water storage tank WP2a and the second water storage tank WP2b use a tank with a maximum water volume of 300 ml, and therefore normally about 30 seconds from the Hi signal output of the low water level sensor DS5b or the low water level sensor DS5d. Can fill the tank. Therefore, water supply is performed for about 40 seconds from the Hi signal output of the low water level sensor DS5b or the low water level sensor DS5d, and the tank is filled with an overflow condition. By this operation, it is possible to ensure that water is always contained in the first water storage tank WP2a and the second water storage tank WP2b, and safety can be maintained.

  The flags F “0”, “5”, and “6” described with reference to FIG. 7 are used in the flow described with reference to FIG. In addition, when the estimated supply operation is executed a predetermined number of times or for a predetermined time, it is assumed that an abnormality has occurred in the water level sensor, the flag F is shifted to 6, and the abnormality response control is executed. Is also preferable.

  In the above-described embodiment, the case where water can be supplied from clean water has been described. However, the case where water is supplied to the reformer RF using only condensed water without receiving water from clean water will be described. In this case, it may be assumed that condensed water does not accumulate as expected. In this case, it is preferable to defer the transition from the partial oxidation reforming reaction POX to the first autothermal reforming reaction ATR1. With reference to the flowchart shown in FIG. 8, the flow for deferring the transition from the partial oxidation reforming reaction POX to the first autothermal reforming reaction ATR1 will be described.

  In step S61, it is determined whether the operation start timing has come. If it is not the operation start timing, the process returns. If it is the operation start timing, the process proceeds to step S62. In step S62, a first initial check is executed to check each part of the fuel cell system FCS.

  In step S63 following step S62, it is determined whether there is no problem in the supply system of air and the gas to be reformed (fuel gas). If there is a problem in the air and reformed gas (fuel gas) supply system, the process proceeds to step S69. If there is no problem in the air and reformed gas (fuel gas) supply system, the process proceeds to step S64. In step S69, an abnormal stop process is executed, the flag F is set to “N”, and the process ends.

  In step S64, the igniter ignites the fuel gas and starts the combustion operation. In step S65 subsequent to step S64, it is determined whether a predetermined time has elapsed since the start of operation of the fuel cell system FCS. If the predetermined time has elapsed, the process proceeds to step S66. The reason for determining whether or not the predetermined time has passed is to secure a time during which the operation in the partial oxidation reforming reaction POX is continued to some extent and it is estimated that condensed water has accumulated. The determination in step S65 is based on the fact that the temperature of the reformer RF has exceeded the predetermined temperature, or based on the fact that the predetermined time has passed since the temperature of the reformer RF has exceeded the predetermined temperature. Is also preferable.

  In step S66, a second initial check is executed. The second initial check will be described with reference to FIG. FIG. 9 is a flowchart showing the flow of the second initial check.

  In step S81, it is determined whether it is time for the second initial check. If it is time for the second initial check, the process proceeds to step S82. If it is not time for the second initial check, the process returns.

  In step S82, it is determined whether a Hi signal is output from the low water level sensor DS5b of the first water storage tank WP2a. If the Hi signal is output from the low water level sensor DS5b of the first water storage tank WP2a, the process proceeds to step S83. If the Hi signal is not output from the low water level sensor DS5b of the first water storage tank WP2a, the process proceeds to step S90. move on. In step S90, the flag F is set to “1” on the assumption that the low water level sensor DS5b of the first water storage tank WP2a is abnormal. This is because the operation in the partial oxidation reforming reaction POX has continued to some extent as described above, and the time has passed although it is considered that condensed water is normally accumulated. This is because the Hi signal is not output from the low water level sensor DS5b of the one water storage tank WP2a.

  In step S83, the flag F is reset (when the flag F is “1”, it is reset to “0”). In step S84 following step S83, it is determined whether a predetermined time has elapsed after the start of the second initial check. If the predetermined time has not elapsed since the start of the second initial check, the process returns. If the predetermined time has elapsed after the start of the second initial check, the process proceeds to step S85.

  In step S85, the pure water pump 111 is driven to supply water from the first water storage tank WP2a to the second water storage tank WP2b. By supplying water to the second water storage tank WP2b before the first water storage tank WP2a becomes full, it is possible to shift to the first autothermal reforming reaction ATR1 at an early stage. If there is an abnormality in the low water level sensor DS5b of the first water storage tank WP2a, the HI signal is output from the high water level sensor DS5a of the first water storage tank WP2a and water is supplied to the second water storage tank WP2b. You can also. However, since it is condensed water that is stored in the first water storage tank WP2a, it takes a very long time.

  In step S86 following step S85, it is determined whether a Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b. If the Hi signal is output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S87. If the Hi signal is not output from the low water level sensor DS5d of the second water storage tank WP2b, the process proceeds to step S91. In step S91, it is determined whether a predetermined time has elapsed. If the predetermined time has elapsed, the process proceeds to step S92. If the predetermined time has not elapsed, the process proceeds to step S85.

  In step S87, it is determined whether or not the water supply to the second water storage tank WP2b is completed. If the water supply to the 2nd water storage tank WP2b is not completed, it will progress to the process of step S85, and if the water supply to the 2nd water storage tank WP2b is completed, it will progress to the process of step S88.

  In step S88, the estimated supply operation is permitted and the flag F is set to “OK”. This is because although it has not been confirmed whether or not there is an abnormality in the high water level sensor DS5a of the first water storage tank WP2a and the high water level sensor DS5c of the second water storage tank WP2b, it is certain that there is water in the second water storage tank WP2b.

  In step 92, it is determined whether the flag F is “1”. If the flag F is “1”, the process proceeds to step S94. If the flag F is not “1”, the process proceeds to step S88.

  In step S94, it is determined that two to three of the water level sensors (high water level sensor DS5a, low water level sensor DS5b, high water level sensor DS5c, low water level sensor DS5d) have failed at the same time, and there is an abnormality in the water supply system. As a result, the flag F is set to “N”.

  In step S89 following step S88 and step S94, the pure water pump 111 is stopped and the process is terminated.

  Returning to FIG. When the second initial check in step S66 is completed as described above, it is determined in step S67 whether there is no problem in the water supply system and whether the flag F is “0” or “OK”. If there is no problem in the water supply system, the process proceeds to step S68. If there is a problem in the water supply system, the process proceeds to step S70. In step S68, the transition to the first autothermal reforming reaction ATR1 is permitted and normal control is executed.

In step S70, it is determined whether abnormality determination is being performed. If the abnormality is being determined, the process proceeds to step S71. If the abnormality is not being determined, the process proceeds to step S73. In step S71, the transition to the first autothermal reforming reaction ATR1 is suspended. In step S72 following step S71, the supply amount of the fuel gas and power generation air is decreased and the process is terminated. In step S73, an abnormal stop process is executed, the flag F is set to “N”, and the process ends.
In addition, in the operation continuation period in which water is supplied from the water storage tank WP2 to the reformer RF, it is confirmed whether an abnormality has occurred in the water level sensor as a second initial check that is a continuation check. Although the estimated supply control is executed, it is also preferable to check whether an abnormality has occurred in the water level sensor as an initial check during the operation start period, and to execute the estimated supply control if an abnormality has occurred.

ADU: Auxiliary unit AH1: Heater AH2: Heater AP: Air supply part AP1: Flow rate adjusting unit AP2: Solenoid valve ATR: Autothermal reforming reaction ATR1: Autothermal reforming reaction ATR2: Autothermal reforming reaction 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: Reformed air flow rate sensor DS9: Power generation air flow rate 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 EP1: Power extraction line FC: Fuel cell FC1: Power generation chamber FC2: Combustion chamber FCM: Fuel cell module FCS: Fuel cell system FP: Fuel supply unit FP1: Flow rate adjustment unit FP2: Desulfurizers FP4, FP5: Gas shut-off valve GD1, GD2: Combustible gas detector HW: Hot water production apparatus MV: Mixing unit POX: Partial oxidation reforming reaction RF: Reformer RF1: Reforming unit RF2: Evaporating unit SC: Fuel cell system control unit SR: Steam reforming reaction WP : Water supply unit WP1: Flow rate adjustment unit WP2: Water storage tank

Claims (8)

A fuel cell system including a solid electrolyte fuel cell,
A reformer that performs steam reforming of the fuel gas supplied to the fuel battery cell; a heat exchanger that exchanges heat with the exhaust gas that is discharged by burning the fuel gas that has passed through the fuel battery cell; Water supply means for supplying water to the mass device, and control means for controlling the water supply means,
The water supply means
A water storage tank for storing dew condensation water in the heat exchanger as water to be supplied to the reformer;
Water level detecting means for detecting the water level of the water storage tank;
A pump for pumping water stored in the water storage tank to the reformer,
The control means includes
In addition to the initial check for the operation start period, an abnormality determination process for determining whether or not the water level detecting means is abnormal is executed in accordance with the supply of exhaust gas to the heat exchanger.   At the time of start-up, the reforming reaction in the reformer is started from a partial oxidation reforming reaction and is changed to a reforming reaction using water, and the control means The fuel cell system according to claim 1, wherein the abnormality determination process is executed at a stage where an oxidation reforming reaction is occurring.   At the time of start-up, the reforming reaction in the reformer is started from a partial oxidation reforming reaction and is changed to a reforming reaction using water, and the control means When the abnormality determination process is performed at the stage of causing the oxidation reaction, and the water level detection means does not detect the water level even when the reformer temperature exceeds a predetermined temperature, the reforming reaction using the water is performed. The fuel cell system according to claim 1, wherein the fuel cell system is controlled so as not to be raised in the reformer. At the time of start-up, the reforming reaction in the reformer is started from a partial oxidation reforming reaction, and transitioned to a reforming reaction using water,
The water supply means has a reverse osmosis membrane for making the water supplied to the reformer pure water,
The water storage tank is constituted by a first tank disposed on the upstream side of the reverse osmosis membrane and a second tank disposed on the reformer side, which is downstream of the reverse osmosis membrane. ,
A first pump for pumping water stored in the first tank to the second tank through the reverse osmosis membrane; and a second pump for pumping water stored in the second tank to the reformer. And
Each of the first tank and the second tank is provided with the water level detection means,
The control means includes
The abnormality determination process is executed at a stage where the partial oxidation reforming reaction is occurring in the reformer, and the water level detecting means provided in the second tank is provided even if the reformer temperature exceeds a predetermined temperature. 2. The fuel cell system according to claim 1, wherein when the water level is not detected, the first pump is driven to forcibly supply water to the second tank.   The control means controls the reforming reaction using the water so as not to occur in the reformer, so that the temperature of the partial oxidation reforming reaction does not rise above a predetermined temperature in the reformer. The fuel cell system according to claim 3, wherein suppression control is executed.   The fuel cell system according to claim 5, wherein the control unit executes the temperature suppression control by suppressing a supply amount of a gas to be reformed supplied to the reformer.   The control means, when the state where the water level detection means does not detect the water level continues for a predetermined time or more, executes an abnormal process control on the assumption that an abnormality has occurred in the water level detection means. Item 4. The fuel cell system according to Item 3.   The control means controls the temperature so as to suppress the oxidation of the fuel cells constituting the fuel cell when the water level detection means does not detect the water level, and to the reformer in the abnormal processing control. The fuel cell system according to claim 7, wherein a cooling stop process is executed by reducing a supply amount of the reformed gas.

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