JP4868268B1 - Solid oxide fuel cell - Google Patents

Abstract

Provided is a solid oxide fuel cell that prevents excessive temperature rise in the case of restart or the like while suppressing a decrease in energy efficiency.
The present invention relates to a solid oxide fuel cell (1), comprising a fuel cell module, a heat storage material (7), a reformer (20), a fuel supply means (38), and a modification. Quality oxidant gas supply means, steam supply means, power generation oxidant gas supply means, temperature detection means, and start-up that causes a reforming reaction in the order of POX, ATR, SR1, SR2 in the reformer And a control means (110) for starting the power generation process after the start-up process is completed while maintaining the fuel supply amount constant in the SR2 during the start-up process for a predetermined power generation transition time or longer SR2 is executed, and it is estimated that the amount of heat that can be used in the heat storage material is accumulated. When the temperature is excessively high, the fuel supply amount is decreased and the fuel utilization rate is increased as compared with the case where the temperature is not excessively high. It is characterized by starting the power generation process with high efficiency operation.
[Selection] Figure 10

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell that generates electric power by reacting a fuel and an oxidant gas for power generation.

  Conventionally, a solid oxide fuel cell device (SOFC) has a plurality of processes for reforming fuel in a reformer in a startup process, that is, a partial oxidation reforming reaction process (POX process), an autothermal reforming reaction process. (ATR process) and a steam reforming reaction process (SR process) are configured to shift to a power generation process (see, for example, Patent Document 1).

In SOFC, the reformer, the fuel cell stack, and the like disposed in the fuel cell module storage chamber can be heated to the operating temperature by sequentially executing these steps.
The SOFC has an operating temperature as high as 600 to 800 ° C., and a heat insulating material is disposed around the fuel cell module storage chamber. Therefore, this heat insulating material can suppress the dissipation of heat from the fuel cell module during operation, and can improve the energy efficiency of the fuel cell.

  On the other hand, Japanese Unexamined Patent Application Publication No. 2010-205670 (Patent Document 2) describes a fuel cell system and a fuel cell operation method. In this fuel cell system, an integrated value of the electric load of the fuel cell is acquired, and the fuel utilization rate is controlled based on the acquired integrated value. In the control of the fuel utilization rate, the temperature of the fuel cell is estimated based on the integral value of the electric load of the fuel cell, and the fuel utilization rate is controlled based on the estimation result. For this reason, the thermal independent operation of the fuel cell is enabled without using a temperature sensor. In addition, when the integrated value of the electric load is equal to or greater than a predetermined value, the control unit corrects the fuel utilization rate to a value equal to or greater than a reference value that allows the fuel cell to perform thermal self-sustained operation. In this case, since the temperature of the fuel cell has risen, the fuel cell has residual heat, and the thermal self-sustained operation is maintained even if the fuel utilization rate is corrected to a value equal to or higher than the reference value that allows the heat self-sustaining operation . This improves the system efficiency of the fuel cell system.

JP 2004-319420 A JP 2010-205670 A

  However, when the solid oxide fuel cell device that has been operating at a high temperature is once stopped and then restarted, since a large amount of heat is stored in the heat insulating material, There was a problem that the temperature of the reformer and the fuel cell stack would rise too much.

  For example, during normal startup operation, heat generated in the POX process, which is an exothermic reaction among the reforming reaction processes in the reformer, raises the temperature of the reformer itself, but the configuration outside the reformer The temperature of the heat insulating material as a member is also raised.

  On the other hand, during the restarting operation, the components outside the reformer are already heated to a certain temperature, and the heat insulating material holds a large amount of heat. Heat is not easily taken away by components outside the reformer. Therefore, the reformer is efficiently heated, and as a result, during the restarting operation, the reformer is heated at a higher temperature rising rate than during the normal starting operation, and exceeds the predetermined operating temperature. There was a risk of overheating. And there existed a possibility that a reformer might deteriorate or be damaged by this excessive temperature rise.

  In order to prevent such a problem due to excessive temperature rise, in the conventional solid oxide fuel cell device, when the temperature of the reformer or the like is too high, the flow rate of the power generation air is increased and the power generation air is increased. By taking the heat of the reformer and the like, the temperature is prevented from rising excessively.

  However, lowering the temperature of the reformer or the like by increasing the flow rate of power generation air increases the exhaust heat from the solid oxide fuel cell device, thus reducing the overall energy efficiency of the fuel cell device. Will do.

  On the other hand, Japanese Patent Application Laid-Open No. 2010-205670 describes a technique for increasing the fuel utilization rate by using the residual heat accumulated in the fuel cell system. A fuel cell system can be operated at a high temperature in a high load zone where a large amount of power is generated. For this reason, after the load changes from a high load to a low load, the temperature in the high load region is maintained for a while, and the inside of the module is maintained at a temperature higher than the operation temperature in the low load region due to the accumulated heat. In the present invention, the remaining heat is used to increase the fuel utilization rate, and the amount of heat necessary for heat self-supporting is supplemented by consuming the remaining heat. In other words, it is an excellent technology that enables operation with an increased fuel utilization rate up to fuel that is less than the amount of fuel that can be thermally independent. It is conceivable to use this technique to lower the excessively raised temperature in the startup process.

  However, in the invention described in Japanese Patent Application Laid-Open No. 2010-205670, since the accumulated residual heat is estimated from the integrated value of the electric load without using the temperature sensor, the residual heat cannot be estimated. Specifically, in the invention described in Japanese Patent Application Laid-Open No. 2010-205670, the generated heat (Joule heat) generated when generating power in the fuel cell is estimated based on the amount of power generation, and thereby the residual heat is estimated. . On the other hand, the heat generated during the start-up process of the fuel cell device is combustion heat generated by burning the remaining fuel that is not used for power generation, and is disclosed in Japanese Patent Application Laid-Open No. 2010-205670. It is not possible to estimate the amount of heat stored during the start-up process using the technology that is being used.

  The present invention has been made to solve such a problem, and is capable of preventing an excessive temperature rise in the case of restarting or the like while suppressing a decrease in overall energy efficiency. The object is to provide a fuel cell.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates electric power by reacting a fuel and an oxidant gas for power generation, and includes a plurality of solid oxide fuel cells inside. A fuel cell module stored in the fuel cell module, a heat storage material that is disposed in the fuel cell module and accumulates heat generated in the fuel cell module , and a modification that partially reforms the fuel by chemically reacting the fuel and oxidant gas. POX, which is a quality reaction, and ATR, which is a reforming reaction that autothermally reforms fuel by simultaneously generating partial oxidation reforming and steam reforming that chemically reacts fuel and steam, and steam reforming only reforming reaction in which SR1 to generate, and to produce hydrogen by generating reforming reaction a is SR2 where a small amount of fuel steam reforming than SR1, fuel And placed reformer in the battery module, by supplying fuel to the reformer, a fuel supply means for feeding fuel reformed in the reformer to the solid oxide fuel cell, a reformer A reforming oxidant gas supply means for supplying reforming oxidant gas to the reactor, a steam supply means for supplying reforming steam to the reformer, and an oxidant for power generation in the solid oxide fuel cell Power generation oxidant gas supply means for supplying gas, temperature detection means for detecting temperatures at a plurality of locations in the fuel cell module , at least one of which reflects the temperature of the reformer, fuel supply means, for reforming The reforming reaction is performed in the order of POX, ATR, SR1, and SR2 in the reformer in the temperature range determined in advance by controlling the oxidant gas supply unit, the water vapor supply unit, and the power generation oxidant gas supply unit. The fuel cell module The startup process is performed to raise the temperature of the solid oxide fuel cell up to the power generation start temperature at which power can be extracted from the fuel cell, while the power generation process for extracting power from the fuel cell module is started after the startup process is completed. And when the temperature of the plurality of locations detected by the temperature detection means is equal to or higher than the temperature of a predetermined transition condition set for each reforming reaction. , is configured to effect the following reforming reaction, further, to have contact during startup process, among the temperature of the plurality of positions, some of the temperature does not reach the temperature of the transition condition, the temperature of the reformer When the reflected temperature value reaches the forced transition temperature set higher than the temperature of the transition condition, the excessive temperature rise determination means for determining that there is an excessive temperature rise, the detected temperature detected by the temperature detection means, and a predetermined temperature Based on deviation from reference temperature The cumulative value that reflects the amount of heat stored in the heat storage material is calculated by integrating the addition and subtraction values determined over time, and the excess heat storage amount accumulated in the heat storage material based on this integrated value And a heat storage amount estimating means for starting addition of the addition / subtraction value from SR2 , and the control means maintains the fuel supply amount constant in SR2 during the start-up process, and at the same time, the solid oxide fuel cell Even if the cell has reached the power generation start temperature, it is configured not to start the power generation process until SR2 is executed for a predetermined power generation transition time or more, and the control means is used as a heat storage material by the heat storage amount estimation means. When it is estimated that an excessive amount of heat is accumulated, and when the excessive temperature rise determination means determines that the excessive temperature rise, the case where the excessive temperature rise does not occur after executing SR2 for a predetermined power generation transition time or longer Yo Also reduces the fuel supply quantity, it is characterized by starting the power generation process with high efficiency operation with increased fuel utilization.

  In the present invention configured as above, the control means controls the fuel supply means, the reforming oxidant gas supply means, and the steam supply means, respectively, to reform the fuel, the reforming oxidant gas, and the steam. In the reformer during the start-up process, each reforming reaction of POX, ATR, SR1, and SR2 is sequentially generated to generate hydrogen. After the start-up process, the temperature of the solid oxide fuel cell provided in the fuel cell module rises to the power generation start temperature, and then a power generation process for extracting power from the fuel cell module is started. The control means maintains the fuel supply amount constant in SR2 during the starting process, and executes SR2 for a predetermined power generation transition time or more even when the solid oxide fuel cell reaches the power generation start temperature. The heat generated in the fuel cell module is accumulated in the heat storage material. The heat storage amount estimation means starts the addition of the addition / subtraction value based on the detected temperature detected by the temperature detection means from SR2, and estimates the heat storage amount accumulated in the heat storage material based on the integrated value. The excessive temperature rise determining means determines an excessive temperature rise of the reformer and the solid oxide fuel cell during the startup process. The control means is estimated that the amount of heat that can be used in the heat storage material is accumulated, and when it is determined that the temperature is excessive, the fuel supply amount is decreased as compared to the case where the temperature is not excessive. Start the power generation process with high-efficiency operation with increased fuel utilization.

  According to the present invention configured as described above, when the temperature rises during the start-up process and the amount of heat that can be used in the heat storage material is accumulated, the power generation process is performed with high efficiency operation with an increased fuel utilization rate. Since it is started, the heat quantity deficient by increasing the fuel utilization rate is supplemented by the heat quantity accumulated in the heat storage material. By consuming the accumulated amount of heat in the power generation process, it becomes possible to quickly eliminate the excessive temperature rise. Moreover, since the amount of heat stored in the heat storage material is used in the power generation process, it is possible to eliminate the excessive temperature rise while improving energy efficiency.

  In general, in a solid oxide fuel cell, the operation state tends to become unstable when shifting from the start-up process to the power generation process, and there is a risk that the fuel cell module will undergo a rapid temperature drop. According to the present invention, in SR2 during the starting process, the fuel supply amount is maintained constant, and SR2 is maintained for a predetermined power generation transition time or longer. For this reason, an operation state is stabilized at the time of transfer to a power generation process, and the risk of a rapid temperature drop can be avoided. In addition, according to the present invention, the amount of heat stored in the heat storage material is estimated based on the sum of the addition / subtraction values started from SR2, so that the amount of heat storage can be accurately estimated. In addition, since the estimation is based on the integration started from SR2, fluctuations in the integration value can be suppressed with respect to changes in the amount of fuel supply at the start of power generation. This makes it possible to stabilize the control when shifting to a power generation process that has a high risk of unstable operating conditions, and to reduce the amount of fuel supplied from when shifting to a power generation process with a high risk. Can be executed safely and reliably.

  In the present invention, preferably, the fuel cell module is configured to generate variable generated power in a predetermined power range according to demand power, and the fuel supply amount in SR2 corresponds to the generated power in the intermediate band of the power range. When the temperature of the fuel cell module rises excessively during the start-up process, the control means starts the power generation process with the generated power below the intermediate band regardless of the demand power. .

  In general, solid oxide fuel cells are operated so that the fuel utilization rate is high in the high power generation band of the power range, and in order to maintain the temperature of the fuel cell module in the low power generation band, It is operated so that the utilization rate is low. For this reason, when the power generation process is operated in the high power generation band, there is little room for further increasing the fuel utilization rate, and it is difficult to consume the amount of heat accumulated in the heat storage material. According to the present invention configured as described above, in the case of excessive temperature rise, regardless of the demand power, the power generation process is started with the generated power below the intermediate band, so by increasing the fuel utilization rate, The amount of heat stored in the heat storage material is quickly consumed, and the excessive temperature rise can be quickly resolved.

In the present invention, preferably, the integrated value for estimating the heat storage amount accumulated in the heat storage material, upon reaching to a Jo Tokoro of the maximum value is not performed in an increase in the integrated value, Jo Tokoro of minimum value when reached are integrated so as not to decrease the integrated value, at the time of integration start of addition and subtraction value in SR2, predetermined to integration from an intermediate value of the maximum value and the minimum value is started The predetermined integrated value is used as an initial value, and the addition / subtraction value integration is started from the initial value .

According to the thus configured present invention, integration is, since starting from a value greater than the intermediate value of maximum value and minimum value, the heat storage material until the integration in SR2 starts The accumulated heat amount can be reflected in the estimated value of the heat storage amount.

In the present invention, preferably, when the temperature of the reformer exceeds a predetermined SR2 transition reformer temperature and the temperature of the solid oxide fuel cell exceeds a predetermined SR2 transition cell temperature, the control means SR1 When the reformer temperature exceeds a predetermined SR2 forced transition temperature set higher than the SR2 transition reformer temperature , the solid oxide fuel cell unit is configured to transition from the SR2 to the SR2. Before the temperature reaches the SR2 transition cell temperature.

  According to the present invention configured as described above, when the reformer exceeds the SR2 forced transition temperature, the SR2 is forcibly shifted to SR2, so that the SR2 in which the fuel supply amount is reduced as compared with SR1 is being executed. An increase in the temperature of the solid oxide fuel cell can be waited, and an excessive increase in the temperature of the reformer can be prevented.

In the present invention, preferably, the control means causes the fuel cell module to generate a predetermined weak power while generating SR2 during the starting process.
According to the present invention configured as described above, since weak power is generated during the execution of SR2, the operation state in the startup process can be approximated to the power generation process, and the process can be more smoothly shifted to the power generation process. it can.

  ADVANTAGE OF THE INVENTION According to this invention, the solid oxide fuel cell which prevents the excessive temperature rise in the case of restart etc. can be provided, suppressing the fall of comprehensive energy efficiency.

1 is an overall configuration diagram showing a fuel cell device according to an embodiment of the present invention. It is front sectional drawing which shows the fuel cell module of the fuel cell apparatus by one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a fuel cell device by one embodiment of the present invention. It is a perspective view which shows the fuel cell stack of the fuel cell apparatus by one Embodiment of this invention. 1 is a block diagram showing a fuel cell device according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the stop of the fuel cell apparatus by one Embodiment of this invention. It is an operation | movement table of the starting process procedure of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of starting in case the fuel cell apparatus by one Embodiment of this invention is restarted. It is a flowchart which shows the control during transfer from the SR1 process to the power generation process through the SR2 process. It is a graph which shows the relationship between the output electric current and fuel supply amount in the solid oxide fuel cell of 1st Embodiment of this invention. It is a graph which shows the relationship between the output electric current in the solid oxide fuel cell of 1st Embodiment of this invention, and the calorie | heat amount which generate | occur | produces with the supplied fuel. It is a heat storage amount estimation table used in order to estimate the heat amount stored in the heat insulating material in the solid oxide fuel cell according to the first embodiment of the present invention. 15 is a graph of the heat storage amount estimation table of FIG. It is a figure which shows notionally the effect | action of the solid oxide fuel cell by 1st Embodiment of this invention. It is a figure which shows typically the transition of the daily demand electric power in a general house, and the transition of the calorie | heat amount accumulate | stored in a heat insulating material. It is a graph which shows the electric current correction coefficient in the modification of 1st Embodiment of this invention. It is the graph which showed typically the relation of the change of demand electric power, the amount of fuel supply, and the current actually taken out from a fuel cell module. It is the graph which showed an example of the relationship of the electric current actually taken out from the air supply amount for power generation, the water supply amount, the fuel supply amount, and the fuel cell module. It is a flowchart which shows the procedure which determines the air supply amount for electric power generation, the water supply amount, and the fuel supply amount based on detection temperature Td. It is a graph which shows the temperature of the appropriate fuel cell stack with respect to a generated electric current. It is a graph which shows the fuel usage rate determined according to an integrated value. It is a graph which shows the range of the value of the fuel utilization factor which can be determined with respect to each generated electric current. It is a graph which shows the air utilization factor determined according to an integrated value. It is a graph which shows the range of the value of the air utilization factor which can be determined with respect to each generated electric current. It is a graph for determining water supply with respect to the determined air utilization rate. It is a graph which shows the electric power generation voltage of the fuel cell module appropriate with respect to electric power generation current. In 2nd Embodiment of this invention, it is a flowchart which shows the procedure which restrict | limits the range of the electric power which a fuel cell module produces | generates. It is a map which shows the electric current limitation with respect to a generated current and detection temperature. It is a time chart which shows an example of the effect | action in 2nd Embodiment of this invention. It is a graph which shows an example of the relationship between the temperature in a fuel cell module, and the maximum electric power which can be generated.

Next, a solid oxide fuel cell (SOFC) according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell (SOFC) 1 according to an embodiment of the present invention includes a fuel cell module 2 and an auxiliary unit 4.

  The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed inside the housing 6 via a heat insulating material 7. A fuel cell assembly 12 that performs a power generation reaction with fuel and oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, residual fuel and residual oxidant (air) that have not been used for the power generation reaction. Burns and produces exhaust gas.
Further, a reformer 20 for reforming the fuel is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which a reforming reaction can be performed by the combustion heat of the residual gas. Yes. Further, an air heat exchanger 22 is disposed above the reformer 20 to heat the air by receiving heat from the reformer 20 and suppress a temperature drop of the reformer 20.

  Next, the auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as tap water and uses the filter to obtain pure water, and a water flow rate that adjusts the flow rate of the water supplied from the water storage tank. An adjustment unit 28 (such as a “water pump” driven by a motor) is provided. In addition, the auxiliary unit 4 adjusts the flow rate of the fuel gas, the gas shutoff valve 32 for shutting off the fuel supplied from the fuel supply source 30 such as city gas, the desulfurizer 36 for removing sulfur from the fuel gas, A fuel flow rate adjustment unit 38 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the air flow rate, and a power generation air flow rate adjusting unit 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

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

Next, the internal structure of a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a side sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention, and FIG. 3 is a sectional view taken along line III-III in FIG. .
As shown in FIGS. 2 and 3, in the sealed space 8 in the housing 6 of the fuel cell module 2, as described above, the fuel cell assembly 12, the reformer 20, and the air heat exchange are sequentially performed from below. A vessel 22 is arranged.

  The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In the reformer 20, an evaporator 20a and a reformer 20b are formed in this order from the upstream side, and the evaporator 20a and the reformer 20b are filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 20 are reformed by the reforming catalyst filled in the reformer 20. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

  A fuel gas supply pipe 64 is connected to the downstream end side of the reformer 20, and the fuel gas supply pipe 64 extends downward and further in an manifold 66 formed below the fuel cell assembly 12. It extends horizontally. A plurality of fuel supply holes 64 b are formed in the lower surface of the horizontal portion 64 a of the fuel gas supply pipe 64, and the reformed fuel gas is supplied into the manifold 66 from the fuel supply holes 64 b.

  A lower support plate 68 having a through hole for supporting the fuel cell stack 14 described above is attached above the manifold 66, and the fuel gas in the manifold 66 flows into the fuel cell unit 16. Supplied.

  Next, an air heat exchanger 22 is provided above the reformer 20. The air heat exchanger 22 includes an air aggregation chamber 70 on the upstream side and two air distribution chambers 72 on the downstream side. The air aggregation chamber 70 and the air distribution chamber 72 include six air flow path tubes 74. Connected by. Here, as shown in FIG. 3, three air flow path pipes 74 form a set (74a, 74b, 74c, 74d, 74e, 74f), and the air in the air collecting chamber 70 is in each set. It flows into each air distribution chamber 72 from the air flow path pipe 74.

The air flowing through the six air flow path pipes 74 of the air heat exchanger 22 is preheated by exhaust gas that burns and rises in the combustion chamber 18.
An air introduction pipe 76 is connected to each of the air distribution chambers 72, the air introduction pipe 76 extends downward, and the lower end side communicates with the lower space of the power generation chamber 10, and the air that has been preheated in the power generation chamber 10. Is introduced.

Next, an exhaust gas chamber 78 is formed below the manifold 66. Further, as shown in FIG. 3, an exhaust gas passage 80 extending in the vertical direction is formed inside the front surface 6 a and the rear surface 6 b which are surfaces along the longitudinal direction of the housing 6, and the upper end of the exhaust gas chamber passage 80 is formed. The side communicates with the space in which the air heat exchanger 22 is disposed, and the lower end side communicates with the exhaust gas chamber 78. Further, an exhaust gas discharge pipe 82 is connected to substantially the center of the lower surface of the exhaust gas chamber 78, and the downstream end of the exhaust gas discharge pipe 82 is connected to the above-described hot water producing apparatus 50 shown in FIG.
As shown in FIG. 2, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.

Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 4 is a partial sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolyte layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

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

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

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

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

Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 5 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 5, the fuel cell stack 14 includes 16 fuel cell units 16, and the lower end side and the upper end side of these fuel cell units 16 are a ceramic lower support plate 68 and an upper side, respectively. It is supported by the support plate 100. The lower support plate 68 and the upper support plate 100 are formed with through holes 68a and 100a through which the inner electrode terminal 86 can pass.

  Furthermore, a current collector 102 and an external terminal 104 are attached to the fuel cell unit 16. The current collector 102 includes a fuel electrode connection portion 102a that is electrically connected to an inner electrode terminal 86 attached to the inner electrode layer 90 that is a fuel electrode, and an entire outer peripheral surface of the outer electrode layer 92 that is an air electrode. And an air electrode connecting portion 102b electrically connected to each other. The air electrode connecting portion 102b is formed of a vertical portion 102c extending in the vertical direction on the surface of the outer electrode layer 92 and a plurality of horizontal portions 102d extending in a horizontal direction along the surface of the outer electrode layer 92 from the vertical portion 102c. Has been. The fuel electrode connection portion 102a is linearly directed obliquely upward or obliquely downward from the vertical portion 102c of the air electrode connection portion 102b toward the inner electrode terminal 86 positioned in the vertical direction of the fuel cell unit 16. It extends.

  Further, the inner electrode terminals 86 at the upper end and the lower end of the two fuel cell units 16 located at the ends of the fuel cell stack 14 (the far left side and the near side in FIG. 5) are external terminals, respectively. 104 is connected. These external terminals 104 are connected to the external terminals 104 (not shown) of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and as described above, the 160 fuel cell units 16 Everything is connected in series.

Next, sensors and the like attached to the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 6, the solid oxide fuel cell 1 includes a control unit 110, and the control unit 110 includes operation buttons such as “ON” and “OFF” for operation by the user. An operation device 112, a display device 114 for displaying various data such as a power generation output value (wattage), and a notification device 116 for issuing a warning (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 110.
First, the combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4.
The CO detection sensor 122 detects whether or not CO in the exhaust gas originally discharged to the outside through the exhaust gas passage 80 or the like leaks to an external housing (not shown) that covers the fuel cell module 2 and the auxiliary unit 4. Is to do.
The hot water storage state detection sensor 124 is for detecting the temperature and amount of hot water in a water heater (not shown).

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

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

As shown in FIG. 3, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14 to thereby detect the fuel cell stack. 14 (ie, the fuel cell 84 itself) is estimated.
The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20.
The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

  Signals from these sensors are sent to the control unit 110, and the control unit 110, based on data based on these signals, the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, A control signal is sent to the power generation air flow rate adjusting unit 45 to control each flow rate in these units.

Next, the operation at the time of start-up by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 7 is a time chart showing the operation at the start-up of the solid oxide fuel cell (SOFC) according to the embodiment of the present invention.
Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

First, reforming air is supplied from the reforming air flow rate adjustment unit 44 to the reformer 20 of the fuel cell module 2 via the first heater 46. At the same time, the power generation air is supplied from the power generation air flow rate adjustment unit 45 to the air heat exchanger 22 of the fuel cell module 2 via the second heater 48, and this power generation air is supplied to the power generation chamber 10 and the combustion chamber. Reach chamber 18.
Immediately after this, the fuel gas is also supplied from the fuel flow rate adjustment unit 38, and the fuel gas mixed with the reforming air passes through the reformer 20, the fuel cell stack 14, and the fuel cell unit 16, and It reaches the combustion chamber 18.

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

  At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction POX shown in FIG. Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. Further, the heated fuel gas is supplied to the lower side of the fuel cell stack 14 through the fuel gas supply pipe 64, whereby the fuel cell stack 14 is heated from below, and the combustion chamber 18 also has the fuel gas and air. The fuel cell stack 14 is also heated from above, and as a result, the fuel cell stack 14 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)

  When the reformer temperature sensor 148 detects that the reformer 20 has reached a predetermined temperature (for example, 600 ° C.) after the partial oxidation reforming reaction POX is started, the water flow rate adjustment unit 28 and the fuel flow rate adjustment unit 38 are detected. In addition, the reforming air flow rate adjusting unit 44 supplies a gas in which fuel gas, reforming air, and water vapor are mixed in advance to the reformer 20. At this time, in the reformer 20, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 20 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

  When the reformer temperature sensor 146 detects that the reformer 20 has reached a predetermined temperature (for example, 700 ° C.) after the start of the autothermal reforming reaction ATR shown in Formula (2), the reforming air flow rate The supply of reforming air by the adjustment unit 44 is stopped, and the supply of water vapor by the water flow rate adjustment unit 28 is increased. As a result, the reformer 20 is supplied with a gas that does not contain air and contains only fuel gas and water vapor, and the steam reforming reaction SR of formula (3) proceeds in the reformer 20.

_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (2)
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (3)

  Since the steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 18. At this stage, since the fuel cell module 2 is in the final stage of start-up, the power generation chamber 10 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 10 is greatly reduced in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 18.

  In this way, after the fuel cell module 2 is ignited by the ignition device 83, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the inside of the power generation chamber 10 The temperature gradually increases. Next, when the temperature in the power generation chamber 10 and the fuel cell 84 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module 2 is stably operated, the circuit including the fuel cell module 2 is closed, and the fuel cell Power generation by the module 2 is started, so that a current flows in the circuit. Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises. As a result, the rated temperature at which the fuel cell module 2 is operated becomes, for example, 600 ° C. to 800 ° C.

  Thereafter, in order to maintain the rated temperature, more fuel gas and air than the amount of fuel gas and air consumed in the fuel cell 84 are supplied, and combustion in the combustion chamber 18 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

Next, the operation when the operation of the solid oxide fuel cell (SOFC) according to the present embodiment is stopped will be described with reference to FIG. FIG. 8 is a time chart showing the operation when the solid oxide fuel cell (SOFC) is stopped according to this embodiment.
As shown in FIG. 8, when the operation of the fuel cell module 2 is stopped, first, the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28 are operated to supply fuel gas and water vapor to the reformer 20. Reduce the amount.

  Further, when the operation of the fuel cell module 2 is stopped, the amount of fuel gas and water vapor supplied to the reformer 20 is reduced, and at the same time, the fuel cell module for generating air by the reforming air flow rate adjusting unit 44 The supply amount into 2 is increased, the fuel cell assembly 12 and the reformer 20 are cooled by air, and these temperatures are lowered. Thereafter, when the temperature of the reformer 20 decreases to a predetermined temperature, for example, 400 ° C., the supply of fuel gas and steam to the reformer 20 is stopped, and the steam reforming reaction SR of the reformer 20 is ended. . This supply of power generation air continues until the temperature of the reformer 20 decreases to a predetermined temperature, for example, 200 ° C., and when this temperature is reached, the power generation air from the power generation air flow rate adjustment unit 45 is supplied. Stop supplying.

  As described above, in the present embodiment, when the operation of the fuel cell module 2 is stopped, the steam reforming reaction SR by the reformer 20 and the cooling by the power generation air are used in combination. The operation of the fuel cell module can be stopped.

Next, with reference to FIG. 7 and FIG. 9, the operation at the time of starting of the solid oxide fuel cell (SOFC) according to the present embodiment will be described in detail.
FIG. 9 is an operation table showing a startup process procedure of the fuel cell 1. As shown in FIG. 9, in the start-up process, the control unit 110 executes each operation control state (combustion operation process, POX1 process, POX2 process, ATR1 process, ATR2 process, SR1 process, SR2 process) in time order. It is configured to shift to a power generation process.

  The POX1 process and the POX2 process are processes in which a partial oxidation reforming reaction is performed in the reformer 20. The ATR1 process and the ATR2 process are processes in which an autothermal reforming reaction is performed in the reformer 20. The SR1 process and the SR2 process are processes in which a steam reforming reaction is performed in the reformer 20. Each of the POX process, the ATR process, and the SR process is subdivided into two parts. However, the present invention is not limited to this, and the POX process, ATR process, and SR process may be subdivided into three or more, or may be configured not to subdivide.

First, when the fuel cell 1 is started at time t ₀ , the control unit 110 causes the reforming air flow rate adjustment unit 44 that is reforming oxidant gas supply means and the power generation air flow rate that is power generation oxidant gas supply means. Signals are sent to the adjustment unit 45 to activate them, and reforming air (oxidant gas) and power generation air are supplied to the fuel cell module 2. In this embodiment, the supply amount of reforming air that is started to be supplied at time t ₀ is 10.0 (L / min), and the supply amount of power generation air is 100.0 (L / min). It is set (see “combustion operation” step in FIG. 9).

Next, at time t ₁ , the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to start fuel supply to the reformer 20. Thus, the fuel and reforming air sent to the reformer 20 are sent into each fuel cell unit 16 via the reformer 20, the fuel gas supply pipe 64, and the manifold 66. The fuel and reforming air sent into each fuel cell unit 16 flow out from the upper end of the fuel gas flow path 98 of each fuel cell unit 16. In the present embodiment, the supply amount of fuel to be supplied at time t ₁ is set to 6.0 (L / min) (see “combustion operation” step in FIG. 9).

Further, at time t ₂ , the control unit 110 sends a signal to the ignition device 83 to ignite the fuel flowing out from the fuel cell unit 16. As a result, the fuel is combusted in the combustion chamber 18, and the heat is used to heat the reformer 20 disposed above the combustion chamber 18, and the combustion chamber 18, the power generation chamber 10, and each fuel disposed therein. temperature of the battery cell unit 16, i.e., the temperature of the fuel cell stack 14 also rises (see time t ₂ ~t ₃ in FIG. 7). The fuel cell unit 16 including the fuel gas passage 98 and the upper end portion thereof correspond to a combustion portion.

When the temperature of the reformer 20 (hereinafter referred to as “reformer temperature”) rises to about 300 ° C. by heating the reformer 20, a partial oxidation reforming reaction (POX) occurs in the reformer 20. (Time t _{3 in} FIG. 7: POX1 process starts). Also in this POX1 step, the fuel supply amount is maintained at 6.0 (L / min) and the reforming air supply amount is maintained at 10.0 (L / min) (see the “POX1” step in FIG. 9). Since the partial oxidation reforming reaction is an exothermic reaction, the reformer 20 is also heated by the reaction heat due to the occurrence of the partial oxidation reforming reaction (time t _{3 to} t _{5 in} FIG. 7).

When the temperature further rises and the reformer temperature reaches 350 ° C. (POX2 transition condition), the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to reduce the fuel supply amount and the reforming air flow rate. A signal is sent to the adjustment unit 38 to increase the supply amount of reforming air (time t _{4 in} FIG. 7: POX2 process start). As a result, the fuel supply amount is changed to 5.0 (L / min), and the reforming air supply amount is changed to 18.0 (L / min) (see the “POX2” step in FIG. 9). These supply amounts are appropriate supply amounts for generating the partial oxidation reforming reaction. In other words, in the initial temperature range where the partial oxidation reforming reaction starts to occur, by increasing the ratio of the fuel to be supplied, a state in which the fuel is surely ignited is formed, and the supplied amount is maintained and ignition is performed. Stabilize (see “POX1” step in FIG. 9). Further, after stable ignition and the temperature rise, waste of fuel is suppressed as a sufficient fuel supply amount necessary for generating the partial oxidation reforming reaction (“POX2” process in FIG. 9). reference).

Next, at time t ₅ in FIG. 7, when the reformer temperature is 600 ° C. or higher and the cell stack temperature is 250 ° C. or higher (ATR1 transition condition), the controller 110 changes the reforming air flow rate adjustment unit 44. Is sent to the water flow rate adjusting unit 28, which is a steam supply means, to start the supply of water (ATR1 process start). As a result, the reforming air supply amount is changed to 8.0 (L / min), and the water supply amount is set to 2.0 (cc / min) (see “ATR1” step in FIG. 9). By introducing water (steam) into the reformer 20, a steam reforming reaction also occurs in the reformer 20. That is, in the “ATR1” process of FIG. 9, autothermal reforming (ATR) in which a partial oxidation reforming reaction and a steam reforming reaction are mixed occurs.

  In the present embodiment, the cell stack temperature is measured by a power generation chamber temperature sensor 142 disposed in the power generation chamber 10. Although the temperature of each fuel cell unit 16 is not perfectly uniform, the cell stack temperature can be thought of as their average temperature. The temperature actually measured in the power generation chamber and the cell stack temperature are not exactly the same, but the temperature detected by the power generation chamber temperature sensor reflects the cell stack temperature. The room temperature sensor can grasp the average temperature of each fuel cell unit 16. On the other hand, the temperature of the reformer 20 is measured by a reformer temperature sensor 148. In the present specification, the cell stack temperature means a temperature measured by an arbitrary sensor that indicates a value reflecting the cell stack temperature.

Further, at time t ₆ in FIG. 7, the reformer temperature is 600 ° C. or above and the stack temperature is more than 400 ° C. (ATR2 transition condition), the control unit 110 sends a signal to the fuel flow regulator unit 38, Reduce fuel supply. Further, the control unit 110 sends a signal to the reforming air flow rate adjustment unit 44 to reduce the reforming air supply amount and sends a signal to the water flow rate adjustment unit 28 to increase the water supply amount (ATR2). Process start). As a result, the fuel supply amount is changed to 4.0 (L / min), the reforming air supply amount is changed to 4.0 (L / min), and the water supply amount is 3.0 (cc / min). (Refer to “ATR2” step in FIG. 9). By reducing the reforming air supply amount and increasing the water supply amount, the ratio of the partial oxidation reforming reaction that is an exothermic reaction is reduced in the reformer 20, and the steam reforming that is an endothermic reaction. The rate of reaction increases. As a result, the rise in the reformer temperature is suppressed, while the fuel cell stack 14 is heated by the gas flow received from the reformer 20, so that the cell stack temperature rises to catch up with the reformer temperature. As the temperature is increased, the temperature difference between the two is reduced, and the temperature is stably increased.

Next, at time t ₇ in FIG. 7, when the temperature difference between the reformer temperature and the cell stack temperature is reduced and the reformer temperature is 650 ° C. or higher and the stack temperature is 600 ° C. or higher (SR1 transition condition), The controller 110 sends a signal to the reforming air flow rate adjustment unit 44 and stops the supply of the reforming air. Further, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to reduce the fuel supply amount and sends a signal to the water flow rate adjustment unit 28 to increase the water supply amount (SR1 process start). As a result, the fuel supply amount is changed to 3.0 (L / min), and the water supply amount is changed to 8.0 (cc / min) (see the “SR1” process in FIG. 9). When the supply of the reforming air is stopped, the partial oxidation reforming reaction does not occur in the reformer 20, and SR in which only the steam reforming reaction occurs is started.

Further, at time t ₈ in FIG. 7, the temperature difference between the reformer temperature and the cell stack temperature is further reduced, the reformer temperature is 650 ° C., which is the SR2 transition reformer temperature, and the cell stack temperature transitions to SR2. When the cell temperature reaches 650 ° C. or higher (SR2 transition condition), the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to reduce the fuel supply amount, and sends a signal to the water flow rate adjustment unit 28 to Reduce supply. In addition, the control unit 110 sends a signal to the power generation air flow rate adjustment unit 45 to reduce the supply amount of power generation air (SR2 process start). As a result, the fuel supply amount is changed to 2.3 (L / min), the water supply amount is changed to 6.3 (cc / min), and the power generation air supply amount is changed to 80.0 (L / min). It is changed (see “SR2” step in FIG. 9). Moreover, the heat storage amount estimation means 110a built in the control unit 110 starts integration of the detected temperature of the power generation chamber 10 in order to estimate the amount of heat stored in the heat insulating material 7 together with the start of the SR2 step. The estimation of the heat storage amount will be described later.

  In the SR1 process, the fuel supply amount and the water supply amount are kept high in order to raise the reformer temperature and the stack temperature to near the temperature at which power generation is possible. Thereafter, in the SR2 step, the fuel flow rate and the water supply amount are reduced, the temperature distributions of the reformer temperature and the cell stack temperature are settled, and are stabilized at a temperature at which power generation is possible. Moreover, the control part 110 starts taking out weak electric power from the fuel cell module 2 with the start of SR2 process. This weak power is a constant power and is not output to the inverter 54 but is used as a part of the power for operating the auxiliary unit 4. By taking out a constant weak power in the SR2 process before the power generation process transition, the operation of the fuel cell module 2 is made unstable without giving the operation condition approximate to that of the power generation process. Become smooth. In this embodiment, the weak power is about 50W. In the present specification, the weak power means a power of about 3% to 15% of the rated power of the solid oxide fuel cell 1.

In the SR2 process, the controller 110 maintains each supply amount for a predetermined power generation transition time, and when the reformer temperature is 650 ° C. or higher and the stack temperature is 700 ° C. or higher (power generation process transition condition), the fuel to output power from the battery module 2 to the inverter 54, to start the transition to the power generation in the power generation process (time in FIG. 7 t _9: power step starts). Thereafter, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28 to change the fuel supply amount and the water supply amount so that the electric power according to the demand power can be generated. Is executed.

  Note that the control unit 110 does not change the predetermined power generation transition time, SR2 even when the reformer temperature reaches 650 ° C. and the stack temperature 700 ° C. before the power generation transition time elapses after the SR2 process starts. After maintaining the process, the power generation process is started.

  Next, with reference to FIG. 10, the operation of the starting process when the solid oxide fuel cell 1 according to the present embodiment is restarted will be described. FIG. 10 is a graph showing an example of changes in the supply amounts of temperatures, fuels, etc. of the respective parts when the solid oxide fuel cell 1 is restarted.

  The graph of FIG. 10 is the same as the graph of FIG. 7, but the start-up process is started from a state in which a large amount of heat remains in the heat insulating material or the like, so that the reformer temperature rises more than in the case of FIG. 7. Is getting faster. In FIG. 10, the reformer temperature in FIG. 7 is shown by a thin one-dot chain line for comparison.

Transition from “combustion operation” to “SR1” stroke in FIG. 10 is the same as FIG. 7 except that the temperature of the reformer is increased rapidly and the time to transition is short. Next, at time t ₂₈ in FIG. 10, the cell stack temperature is about 630 ° C., and the reformer temperature is 700 ° C. Therefore, in this state, the reformer temperature exceeds the SR2 transition reformer temperature of 650 ° C., but the cell stack temperature does not reach the SR2 transition cell temperature of 650 ° C. It does not meet normal transition temperature conditions. However, when the reformer temperature reaches 700 ° C. which is the SR2 forced transition temperature in the “SR1” stroke, the excessive temperature rise determination unit 110b built in the control unit 110 determines that the temperature is excessive. Then, before the cell stack temperature reaches 650 ° C., the process is forcibly shifted to the “SR2” process (temperature condition in a square box in the “SR1” column in FIG. 9).

When the process proceeds to the “SR2” step, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to reduce the fuel supply amount, and sends a signal to the water flow rate adjustment unit 28 to reduce the water supply amount. . Further, the control unit 110 sends a signal to the power generation air flow rate adjustment unit 45 to decrease the supply amount of the power generation amount air. As a result, the fuel supply amount is changed to 2.3 (L / min), the water supply amount is changed to 6.3 (cc / min), and the power generation air supply amount is changed to 80.0 (L / min). Be changed. The control unit 110 reduces the fuel supply amount, the water supply amount, and the power generation air supply amount to these values over about 2 minutes (time t _{29 in} FIG. 10).

Then, at time t ₃₀ in Figure 10, the cell stack temperature is about 680 ° C., the reformer temperature is 720 ° C.. Therefore, this state does not meet the normal transition temperature conditions for the power generation process in which the cell stack temperature is 700 ° C. or higher and the reformer temperature is 650 ° C. or higher. However, when the reformer temperature reaches 720 ° C., which is the power generation forced transition temperature, in the “SR2” process, the excessive temperature rise determination unit 110b built in the control unit 110 generates an excessive temperature rise. Therefore, before the cell stack temperature reaches 700 ° C., the process is forcibly shifted to the power generation process (temperature conditions in a square box in the column “SR2” in FIG. 9).

However, the control unit 110, a fuel supply amount, water supply, and to the generating air supply amount after the time t ₂₉ which has reached the predetermined flow rate in each "SR2" process, at least a predetermined transition time electrical generation has elapsed Keeps each flow rate constant and continues the “SR2” step. That is, after the time t _29, is satisfied normal power transition temperature before the transition time electrical generation has elapsed, or, even when the reformer temperature reached generating forced migration temperature, power generation transition time The “SR2” process is maintained until the time has elapsed, and then the power generation process is started. In the present embodiment, the power generation transition time is 2 minutes.

  The power generation transition time is determined by maintaining the fuel supply amount at a constant value over the power generation transition time before the transition to the power generation process where the operation of the solid oxide fuel cell 1 is likely to become unstable. It is provided for stabilization. Further, in the present embodiment, the control unit 110 sets each control parameter necessary for the control of the fuel cell module 2 such as a heat storage amount, a temperature of each unit, a fuel supply amount, etc., which will be described later, a time of each measured value of temperature and flow rate. The calculation is performed based on the actual transition and the control is performed based on the calculation. In other words, the control unit 110 obtains each control parameter by performing an operation such as moving average or integral calculation on the temperature, flow rate, and the like measured by each sensor. Alternatively, the heat storage amount that is one of the control parameters is estimated by integration of the power generation room temperature that is one of the control parameters. As described above, in the present embodiment, each control parameter is calculated based on their temporal transition, and each control parameter calculated based on the measured value during the SR2 period is transferred to the power generation process. The initial value of each control parameter in the power generation process. In SR2, since the fuel supply amount and the like are maintained at a constant value over at least the power generation transition time, each measured value is also stable, and the initial value of each control parameter at the start of the power generation process is highly reliable. It will be a thing.

  Next, at the start of the power generation process, it is estimated that the amount of heat that can be used in the heat insulating material 7 is accumulated by the integration described later, and the excessive temperature rise determination means 110b performs the “SR1” process or the “SR2” process. When it is determined that an excessive temperature rise has occurred, the control unit 110 starts the power generation process with high efficiency operation with a reduced fuel supply amount and a higher fuel utilization rate than when the temperature is not excessively high. . As described above, by generating power by reducing the fuel supply amount as compared with the normal power generation process, the amount of fuel burned to maintain the temperature of the fuel cell module 2 decreases. Thus, the shortage of heat is supplemented by the amount of heat accumulated in the heat insulating material 7 and the like. By consuming the amount of heat accumulated in the heat insulating material 7 or the like, the temperature of the reformer 20 or the like that has been excessively raised is lowered to an appropriate temperature. As described above, the power generation process with the increased fuel utilization rate is executed until there is no more heat available in the heat insulating material 7 or the like.

  Next, with reference to FIG. 11, the transition from the startup process to the power generation process will be described. FIG. 11 is a flowchart showing the control during the transition from the SR1 process to the power generation process through the SR2 process. The startup process shown in FIGS. 7 and 10 is also executed based on the flowchart shown in FIG.

  First, in step S1 of FIG. 11, temperature detection values are read from the power generation chamber temperature sensor 142 and the reformer temperature sensor 148 which are temperature detection means. Here, the first detected temperature, which is the temperature read from the reformer temperature sensor 148, is a temperature reflecting the temperature of the reformer 20, and corresponds to the reformer temperature in FIG. Further, the second detected temperature, which is the temperature read from the power generation chamber temperature sensor 142, reflects the temperature of the fuel cell stack 14 composed of the plurality of fuel cell units 16, and the cell stack temperature in FIG. The corresponding temperature. The cell stack temperature and the reformer temperature are sequentially read and updated to new values during execution of the flowchart of FIG. Further, in this specification, the temperature reflecting the temperature of the reformer 20 is simply referred to as “reformer temperature”, and the temperature reflecting the temperature of the fuel cell unit 16 is simply referred to as “temperature of the fuel cell unit”. "

  Next, in step S2, it is determined whether or not the cell stack temperature and the reformer temperature have reached the SR1 transition condition. That is, when the reformer temperature is 650 ° C. or higher and the cell stack temperature is 600 ° C. or higher, it is determined that the SR1 transition condition is satisfied, and the process proceeds to step S3. If the SR1 transition condition is not satisfied, the one-time process of the flowchart shown in FIG. 11 is terminated, and the ATR2 process is continued. Thereafter, the flowchart of FIG. 11 is executed at predetermined time intervals until the SR1 transition condition is satisfied.

  On the other hand, when the SR1 transition condition is satisfied in step S2 and the process proceeds to step S3, the operation of the condition in the SR1 process is executed in step S3 (see the “SR1” process in FIG. 9). Next, in step S4, it is determined whether or not the reformer temperature has reached the SR2 forced transition temperature of 700 ° C. (temperature condition in a square box in the “SR1” column in FIG. 9). If the reformer temperature has reached the SR2 forced transition temperature, the process proceeds to step S6, and if not, the process proceeds to step S5.

  In step S5, it is determined whether or not the cell stack temperature and the reformer temperature have reached the SR2 transition condition. That is, when the reformer temperature is 650 ° C. or higher and the cell stack temperature is 650 ° C. or higher, it is determined that the SR2 transition condition is satisfied, and the process proceeds to step S7. If the SR2 transition condition is not satisfied, the process returns to step S3. For this reason, after the SR1 transition condition is satisfied, until the SR2 transition condition (cell stack temperature of 650 ° C. or higher) is satisfied, the process of step S3 → step S4 → step S5 → step S3 is repeated. On the other hand, if the reformer temperature reaches 700 ° C. which is the SR2 forced transition temperature before the cell stack temperature reaches 650 ° C. after the SR1 transition condition is satisfied, the process proceeds from step S4 to step S6. The SR2 process is forcibly started. That is, the excessive temperature rise determination means 110b built in the control unit determines that the temperature is excessively high, and the process is forcibly shifted to the SR2 step.

  In the time chart of FIG. 7 described above, since the cell stack temperature has reached 650 ° C. before the reformer temperature reaches the SR2 forced transition temperature, the SR2 process is performed in the path from step S5 to step S7. Has been started. On the other hand, in the time chart of FIG. 10 described above, since the reformer temperature has reached the SR2 forced transition temperature before the cell stack temperature reaches 650 ° C., the SR2 process is performed in the path from step S6 to step S7. Has been started.

  In step S7, the driving | running of the conditions in SR2 process is performed (refer "SR2" process in FIG. 9). Next, in step S8, it is determined whether or not the fuel supply amount, power generation air supply amount, and water supply amount set in the SR2 step are stably obtained. That is, the supply amount in the SR1 process is changed to each supply amount set in the SR2 process, and it takes a certain time until each supply amount after the change is stably obtained. It is determined whether the supply amount is stably obtained. In the present embodiment, it is determined whether or not each supply amount is stable based on the elapsed time after execution of step S7, and the process of step S8 is repeated until a predetermined time elapses.

  When the predetermined time has elapsed, the process proceeds to step S9, and the extraction of the weak power from the fuel cell module 2 is started. This weak power is not output to the inverter 54 but is used as a part of power for operating the auxiliary machine unit 4. In this way, by extracting the weak power for raising temperature from the fuel cell module 2 during the startup process, each fuel cell unit 16 is heated by the generated heat. Since this generated heat mainly heats the low temperature portion of the fuel cell unit 16, the temperature distribution of each fuel cell unit 16 is made to be uniform. Further, in the fuel cell module 2, when the temperature of the reformer 20 is higher than the appropriate temperature and the temperature of each fuel cell unit 16 is lower than the appropriate temperature, each fuel cell unit is extracted by taking out weak electric power. 16 rises, and the temperature of the fuel cell stack 14 approaches the temperature of the reformer 20. Therefore, step S9 for taking out the weak power acts as a temperature uniformizing means for bringing the temperature in the fuel cell module 2 close to uniform.

  Next, in step S10, addition / subtraction value integration processing is started. As will be described later, the addition / subtraction value is determined based on the temperature detected by the power generation chamber temperature sensor 142, and the heat storage amount to the heat insulating material 7 is estimated by integrating the addition / subtraction value.

  Next, in step S11, after the integration process is started in step S10, it is determined whether or not a predetermined power generation transition time of 2 minutes has elapsed. Until the predetermined power generation transition time elapses, the process of step S11 is repeated.

  When the power generation transition time elapses after the integration process starts, the process proceeds to step S12. In step S12, it is determined whether or not the cell stack temperature and the reformer temperature have reached the power generation transition condition. That is, when the reformer temperature is 650 ° C. or more which is the power generation transition threshold temperature and the cell stack temperature is 700 ° C. or more which is the power generation transition threshold temperature, it is determined that the power generation transition condition is satisfied, Proceed to S13. Moreover, when the power generation transfer condition is not satisfied, the process proceeds to step S14.

  Next, in step S14, it is determined whether or not the reformer temperature has reached the power generation forced transition temperature of 720 ° C. (temperature condition in a square box in the “SR2” column in FIG. 9). If the reformer temperature has reached the power generation forced transition temperature, the process proceeds to step S15. If the reformer temperature has not reached the power generation forced transition temperature, the process returns to step S12. Therefore, after the power generation transition time has elapsed in step S11, the process of step S12 → step S14 → step S12 is repeated until the power generation transition condition is satisfied or the reformer temperature reaches the power generation forced transition temperature. It is.

  In the time chart of FIG. 7 described above, since the cell stack temperature reaches 700 ° C. before the reformer temperature reaches the power generation forced transition temperature, the power generation process takes place along the path from step S12 to step S13. Has been started. On the other hand, in the time chart of FIG. 10 described above, since the reformer temperature has reached the power generation forced transition temperature before the cell stack temperature reaches 700 ° C., the power generation process follows the path from step S14 to step S15. Has been started.

  When the power generation transition condition is satisfied in step S12, the process proceeds to step S13, and in step S13, a normal power generation process is started. On the other hand, when the reformer temperature reaches the power generation forced transition temperature in step S14, the process proceeds to step S15 even if the cell stack temperature does not reach the power generation transition threshold temperature, and is forcibly shifted to the power generation process. . That is, the excessive temperature rise determination means 110b built in the control unit determines that the temperature is excessively high, and forcibly shifts to the power generation process. In step S15 for forcibly starting the power generation process, high-efficiency control using the amount of heat accumulated in the heat insulating material 7 is executed. Specific high-efficiency control will be described later.

Next, the estimation of the amount of heat and the amount of heat stored in the fuel cell module will be described with reference to FIGS.
FIG. 12 is a graph showing the relationship between the output current and the fuel supply amount in the solid oxide fuel cell 1 of the present embodiment. FIG. 13 is a graph showing the relationship between the output current in the solid oxide fuel cell 1 and the amount of heat generated by the supplied fuel.

  First, as shown by the solid line in FIG. 12, the solid oxide fuel cell 1 of the present embodiment is configured so that the output can be varied at 700 W (output current 7 A) or less, which is the rated output power, according to the demand power. Has been. The fuel supply amount (L / min) required to output the required power is set as a basic fuel supply table indicated by a solid line in FIG. The control unit 110 serving as the control means determines the fuel supply amount based on the basic fuel supply table in accordance with the demand power detected by the power state detection sensor 126 serving as the demand power detection means, and supplies the fuel based on this. It is configured to control the fuel flow rate adjusting unit 38 as a means.

  The amount of fuel required for power generation is proportional to the output power (output current), but as shown by the solid line in FIG. 12, the fuel supply amount set in the basic fuel supply table is not proportional to the output current. This is because if the fuel supply amount is reduced in proportion to the output power, the fuel cell unit 16 in the fuel cell module 2 cannot be maintained at a temperature at which power can be generated. For this reason, in the present embodiment, the basic fuel supply table is set to a fuel utilization rate of about 70% when the generated power is near the output current 7A, and is set to about 50% when the generated power is about 2A. Is set. Thus, the temperature of the fuel cell unit 16 is reduced by reducing the fuel utilization rate in the small power generation region and burning the remaining fuel that has not been used for power generation to heat the reformer 20 and the like. The decrease is suppressed, and the inside of the fuel cell module 2 is maintained at a temperature capable of generating power.

  However, since the fuel that does not contribute to power generation is increased by reducing the fuel utilization rate, the energy efficiency of the solid oxide fuel cell 1 in the small power generation region is reduced. In the solid oxide fuel cell 1 of the present embodiment, the fuel table changing means 110c (FIG. 6) built in the control unit 110 sets the fuel supply amount set in the basic fuel supply table according to a predetermined condition. By changing / correcting, the fuel supply amount is decreased as shown by the broken line in FIG. 12, and the fuel utilization rate in the small power generation region is increased. Thereby, the energy efficiency of the solid oxide fuel cell 1 is improved.

  FIG. 13 is a graph schematically showing the relationship between the output current and the amount of heat of the supplied fuel when the fuel is supplied based on the basic fuel supply table in the solid oxide fuel cell 1 of the present embodiment. is there. As indicated by a one-dot chain line in FIG. 13, the amount of heat necessary to make the fuel cell module 2 thermally independent and operate stably increases monotonically with an increase in output current. The graph shown by the solid line in FIG. 13 indicates the amount of heat when fuel is supplied according to the basic fuel supply table. In the present embodiment, in a region lower than the output current 5A corresponding to the medium generated power, the required amount of heat indicated by the alternate long and short dash line and the amount of heat supplied based on the basic fuel supply table indicated by the solid line substantially coincide.

  Further, in a region higher than the output current 5A, the amount of heat indicated by the solid line supplied in accordance with the basic fuel supply table exceeds the amount of heat indicated by the one-dot chain line necessary for heat self-sustainment. The surplus heat amount between the solid line and the broken line is accumulated in the heat insulating material 7 that is a heat storage material provided in the fuel cell module 2. Further, when a large output current is taken out from the solid oxide fuel cell 1, heat generation in the fuel cell unit 16 increases, and the temperature in the fuel cell module 2 rises. For this reason, there is a correlation between the output current from the solid oxide fuel cell 1 and the temperature of the fuel cell unit 16 in the fuel cell module 2 when this current is constantly output, and the output current is In a large state, the temperature of the fuel cell unit 16 is high. In the present embodiment, the output current 5A corresponds to about 633 ° C. which is the heat storage temperature Th. Therefore, in the solid oxide fuel cell 1 of the present embodiment, a larger amount of heat is accumulated in the heat insulating material 7 when the output current is 5 A and the heat storage temperature Th is about 633 ° C. or higher.

  This heat storage temperature Th is set to a temperature corresponding to 500 W (output current 5 A) that is larger than 350 W, which is the median value of 0 W to 700 W that is the generated power range. In the region where the output current is 5 A or less, the amount of heat supplied based on the basic fuel supply table is substantially the same as the minimum amount of heat necessary for heat self-sustainment (the amount of heat of the basic fuel supply table is slightly larger). Is set. For this reason, as shown by an example of the broken line in FIG. 13, when the fuel supply amount by the basic fuel supply table is corrected and the fuel supply amount is reduced, the amount of heat necessary for thermal independence is insufficient.

  In the present embodiment, as will be described later, in a region where the generated power is small, the fuel supply rate set in the basic fuel supply table is corrected so as to be temporarily reduced to improve the fuel utilization rate. On the other hand, the amount of heat that is deficient by reducing the fuel supply amount of the basic fuel supply table uses the amount of heat accumulated in the heat insulating material 7 while the fuel cell module 2 is operated in a region higher than the heat storage temperature Th. And replenished. In this embodiment, since the heat capacity of the heat insulating material 7 is very large, the heat insulating material is operated when the fuel cell module 2 is operated in a region where the generated power is small after being operated for a predetermined time with large generated power. The amount of heat stored in 7 can be used for 2 hours or more, and the fuel utilization rate is improved by performing correction to reduce the fuel supply amount during this period.

  In the present embodiment, the basic fuel supply table is set so that more heat is accumulated in the heat insulating material 7 when the output current is 5A and the heat storage temperature Th is about 633 ° C. or higher. Even in the region where the current is 5 A or more, the basic fuel supply table can be set to be substantially the same as the minimum amount of heat necessary for heat self-sustainment (the amount of heat of the basic fuel supply table is slightly larger). That is, in the region where the generated power is large, the operating temperature of the fuel cell module 2 is higher than when the generated power is small, so even if the fuel supply amount is set to the minimum heat amount necessary for heat self-sustaining, The amount of heat available at the time of small power generation can be stored in the heat insulating material 7. As in this embodiment, by actively setting a large amount of fuel supply at the time of large power generation, the amount of heat necessary for the heat insulating material 7 can be reliably accumulated in a short period of time during the night when power demand peaks. be able to.

Next, with reference to FIG.14 and FIG.15, estimation of the heat storage amount accumulate | stored in the heat insulating material 7 grade | etc., Is demonstrated concretely.
FIG. 14 is a heat storage amount estimation table used for estimating the amount of heat accumulated in the heat insulating material 7. FIG. 15 is a graph of the heat storage amount estimation table.

The estimation of the heat storage amount is executed by the heat storage amount estimation means 110a (FIG. 6) built in the control unit 110. The heat storage amount estimation means 110a starts estimation of the heat storage amount after time t ₂₉ (FIG. 10) when the fuel supply amount, the water supply amount, and the power generation air supply amount respectively reach predetermined flow rates in the “SR2” process. To do. That is, the heat storage amount estimation unit 110a determines the addition / subtraction value with reference to the heat storage amount estimation table shown in FIG. 14 based on the detected temperature Td of the power generation chamber temperature sensor 142 which is a temperature detection unit. The addition / subtraction values are determined at predetermined time intervals, and are sequentially integrated to calculate the integrated value Ni. In this embodiment, integration is performed once every 0.5 sec.

Such an integrated value Ni reflects a transition / history of the temperature in the fuel cell module 2 and the power generation chamber 10, and is a value serving as an index indicating the degree of the heat storage amount accumulated in the heat insulating material 7 or the like. is there. This integrated value Ni is calculated so as to take a value between 0 which is the minimum heat storage value and 1 which is the maximum heat storage value. That is, when the integrated value Ni reaches 1, the value is held at 1 until the next subtraction, and when the integrated value Ni decreases to 0, the value is 0 until the next addition is performed. Retained. In the present embodiment, when starting the integration of the integrated value Ni at time t ₂₉ in FIG. 10, the integrated value Ni 0.7 greater than 0.5 which is an intermediate value of the heat storage minimum heat storage maximum value Integration is started as an initial value of. This initial value is a value corresponding to a heat storage amount that is considered to be accumulated at a minimum in the startup process up to the “SR1” process.

  In the present specification, it is assumed that a value serving as an index indicating the degree of the heat storage amount is an estimated value of the heat storage amount, like the integrated value Ni in the present embodiment. Therefore, in this embodiment, the heat storage amount is estimated based on the temperature of the fuel cell module 2.

  As shown in FIG. 14, for example, when the detected temperature Td is 645 ° C., the addition / subtraction value is determined to be 1/50000. The determined addition / subtraction value is added to the integrated value Ni. Therefore, when the detected temperature Td is constant at 645 ° C., the value of 1/50000 is integrated once every 0.5 sec, and the integrated value Ni increases.

  As shown in FIGS. 14 and 15, in this embodiment, the integration is performed when the detected temperature Td is higher than 635 ° C., which is the change reference temperature Tcr, and is subtracted when the detected temperature Td is lower. . That is, when the detected temperature Td is higher than the changed reference temperature Tcr, the amount of heat that can be used for improving the fuel utilization rate is accumulated in the heat insulating material 7 or the like, and when it is lower than the changed reference temperature Tcr, the heat insulating material 7 is used. The integrated value Ni is calculated assuming that the heat accumulated in etc. is taken away. In other words, the integrated value Ni corresponds to the time integration of the temperature deviation of the detected temperature Td with respect to the change reference temperature Tcr, and the heat storage amount is estimated based on the integrated value Ni.

  Further, as shown in FIGS. 14 and 15, when the detected temperature Td is lower than 580 ° C., the addition / subtraction value is determined to be 20/50000, and this value is subtracted from the integrated value Ni by the heat storage amount estimation means 110a. When the detected temperature Td is not less than 580 ° C. and less than 620 ° C., 10/50000 × (620−Td) / (620−580) is subtracted from the integrated value Ni. When the detected temperature Td is 620 ° C. or higher and lower than 630 ° C., 1 / 50,000 is subtracted from the integrated value Ni.

  On the other hand, when the detected temperature Td is 650 ° C. or higher, 1/50000 × (Td−650) is added to the integrated value Ni. When the detected temperature Td is 640 ° C. or higher and lower than 650 ° C., 1 / 50,000 is added to the integrated value Ni.

Furthermore, when the detected temperature Td is between 630 and 640 ° C., the processing differs depending on whether the detected temperature Td is increasing or decreasing.
That is, when the detected temperature Td is 630 ° C. or higher and lower than 632 ° C., the added value is set to 0 (no addition / subtraction) when the detected temperature Td tends to increase, and 1 / 50,000 when the detected temperature Td tends to decrease. Is subtracted. As described above, when the detected temperature Td is lower than the change reference temperature Tcr and the difference between them is 5 ° C. or less which is a minute deviation temperature, when the detected temperature Td tends to decrease, the detected temperature Td tends to increase The integrated value Ni is decreased more rapidly than. Here, the heat insulating material 7 or the like has a very large heat capacity, and once the detected temperature Td starts to decrease, it is expected that the temperature will continue to decrease for a while. Therefore, in such a situation, it is necessary to quickly reduce the integrated value Ni to avoid the risk of a significant temperature drop in the fuel cell module 2.

  On the other hand, when the detected temperature Td is not less than 638 ° C. and less than 640 ° C., 1/50000 is added when the detected temperature Td tends to increase, and the added value is 0 (not added or subtracted) when the detected temperature Td tends to decrease ). As described above, the heat insulating material 7 and the like have a very large heat capacity, and once the detected temperature Td starts to rise, it is expected that the temperature will continue to rise for a while. Therefore, in such a situation, the integrated value Ni is quickly increased.

When the detected temperature Td is 632 ° C. or higher and lower than 638 ° C., the detected temperature Td is in the vicinity of 635 ° C., which is the change reference temperature Tcr, and is considered to be stable, regardless of the tendency of the detected temperature Td. The current state is maintained by setting the addition value to 0 (no addition / subtraction is performed).
In the above-described embodiment, the addition / subtraction value is determined based on the detection temperature Td of the power generation chamber temperature sensor 142. However, the addition / subtraction value is determined based on the detection temperature of the reformer temperature sensor 148, and the amount of stored heat. Can also be estimated. In this case, the reformer temperature sensor 148 functions as temperature detection means.

Next, control of the fuel cell module 2 at the start of the power generation process will be described.
Heat storage amount estimating means 110a is the integration of the subtraction value determined as described above, (time t ₂₉ in FIG. 10, step S10 in FIG. 11) SR2 step start starts from, at least a predetermined transition time electrical generation After the integration is performed, the process proceeds to the power generation process. In addition, the controller 110 determines that the excessive temperature rise determination unit 110b has caused an excessive temperature increase during the startup process, and if the amount of heat available in the heat insulating material 7 is accumulated, The power generation process is started with high-efficiency operation in which the fuel supply amount is reduced as compared with the case where there is no fuel (step S15 in FIG. 11). In the present embodiment, the excessive temperature rise determination unit 110b, during the start-up process, when the reformer temperature forcibly shifts to the SR2 process by exceeding the SR2 forced transition temperature (steps S4 to S6 in FIG. 11), Alternatively, when the reformer temperature forcibly shifts to the power generation process by exceeding the power generation forced transition temperature (steps S14 to S15 in FIG. 11), it is determined that an excessive temperature rise has occurred. In addition, when the integrated value Ni calculated by the heat storage amount estimation unit 110a is not 0, it is determined that the heat amount usable in the heat insulating material 7 is accumulated.

  Note that the excessive temperature rise is determined based on the rate of increase of the reformer temperature per time during the startup process, the time during which the reformer temperature rises from the first temperature to the second temperature, and the like. The excessive temperature rise determination means 110b can also be configured.

  In the high-efficiency operation, power generation is performed with fuel less than the fuel supply amount set by the basic fuel supply table shown in FIG. 13, and the fuel utilization rate is improved. That is, in high-efficiency operation, a reduction correction that reduces the fuel supply amount determined by the basic fuel supply table in accordance with the demand power is executed. The correction amount for decreasing the fuel supply amount is determined according to the estimated heat amount, and the greater the integrated value Ni, the more significant reduction correction is performed. By this reduction correction, the amount of heat of the supplied fuel is less than the amount of heat necessary for the fuel cell module 2 to become self-sustaining, but the insufficient amount of heat is supplemented by the heat accumulated in the heat insulating material 7 and the like. By utilizing the heat accumulated in the heat insulating material 7 and the like, the overall energy efficiency of the solid oxide fuel cell 1 is improved and the temperature of the heat insulating material 7 and the like is lowered. The condition is resolved.

  The high-efficiency operation is continued until there is no available heat amount estimated by the heat storage amount estimation unit 110a, that is, until the integrated value Ni becomes zero. At the time of transition to the power generation process, the operation of the fuel cell module 2 is likely to become unstable and a sudden temperature drop or the like is likely to occur. In this embodiment, however, the integration over the power generation transition time during the SR2 process Since the heat storage amount is estimated by the above, the estimation accuracy of the heat storage amount is high, and such a risk is surely avoided.

  In addition, the control unit 110 controls the fuel cell module 2 to change the generated power within the power range of 700 W or less, which is the maximum rated output power, according to the demand power, but starts the power generation process with high efficiency operation. In the case (step S15 in FIG. 11), regardless of the demand power, the power generation process is started with the upper limit power at the time of forced transition set below the intermediate band in the power range. In the SR2 process during the start-up process, the fuel supply amount is maintained at 2.3 (L / min), but this fuel supply amount corresponds to the generated power of about 500 W, which is an intermediate band within the power range. Is. When the controller 110 starts the power generation process with high efficiency operation, the generated power is set to the intermediate band regardless of the demand power so that the fuel supply amount is reduced as compared with the SR2 process. Suppress below the upper limit power. Therefore, even when the demand power increases beyond the forced transition upper limit power, the generated power is not followed and is maintained at the forced transition upper limit power. In the present specification, the generated power in the intermediate band refers to generated power of about 20% to 70% of the rated output power. Moreover, in this embodiment, the upper limit power at the time of forced transition is set to 400W.

  As shown in FIG. 12, in the high power generation band in the power range, the fuel utilization rate is high even in the basic fuel supply table, and there is little room for reducing fuel other than the portion used for power generation. For this reason, even if the fuel supply amount is corrected to decrease, the amount of heat accumulated in the heat insulating material 7 is not consumed much. Further, in the high power generation band, since the operating temperature of the fuel cell module 2 is high (FIG. 13), it is an operation state in which it is difficult to use the amount of heat accumulated in the heat insulating material 7. Therefore, when starting the power generation process with high efficiency operation, the control unit 110 suppresses the generated power to be equal to or lower than the intermediate band regardless of the demand power. With the generated power below the intermediate band, the fuel utilization rate in the basic fuel supply table is low, and the operating temperature of the fuel cell module 2 is relatively low. For this reason, the fuel supply amount can be corrected to be greatly reduced by high-efficiency operation, and the amount of heat stored in the heat insulating material 7 is easily consumed, so that the excessively high temperature state is quickly eliminated.

  Furthermore, when the power generation process is started with high-efficiency operation (step S15 in FIG. 11), the fuel fluctuation gain that increases the fuel supply amount following the increase in demand power is reduced by 30% compared to that during normal operation. . Thereby, the followability with respect to the demand power of generated electric power is reduced. As will be described later, the frequent increase or decrease in the generated power increases the temperature in the fuel cell module 2 in order to increase the residual fuel that is burned in the combustion chamber 18 without being used for power generation. By reducing the followability of the generated power to the demand power, the increase or decrease in the generated power is reduced, and the temperature rise in the fuel cell module 2 can be suppressed.

Next, with reference to FIGS. 16 and 17, the operation of the power generation process by high-efficiency operation will be described. FIG. 16 is a diagram conceptually showing the operation of the solid oxide fuel cell 1 according to the present embodiment, and FIG. 17 is a graph showing the daily demand power transition in a general house and the amount of heat accumulated in the heat insulating material. It is a figure which shows typically transition. The upper graph in FIG. 16 conceptually shows the operation when the heat quantity available in the heat insulating material 7 is not accumulated, and the middle and lower graphs show the cases where the accumulated heat quantity is small and large. Each shows. As shown in the upper part of FIG. 16, when the operation with a large amount of generated power and a large amount of fuel supply is performed for a short time, the amount of heat that can be used is not accumulated in the heat insulating material 7. It is determined based on the basic fuel supply table, and the fuel utilization rate is not increased. On the other hand, as shown in the middle of FIG. 16, when the operation with large generated power is performed for a certain period of time, the operation after the decrease in generated power is the amount of heat accumulated in the heat insulating material 7 when the generated power is large. Therefore, while the amount of heat available in the heat insulating material 7 remains, a highly efficient operation in which the fuel supply amount is reduced as compared with the basic fuel supply table is performed. This saves fuel corresponding to the hatched portion of the middle graph. Further, as shown in the lower part of FIG. 16, when an operation with large generated power is performed for a long time, a large amount of heat is accumulated in the heat insulating material 7, so the amount of heat accumulated over a longer time is reduced. Utilized high efficiency operation is performed and more fuel is saved.
Next, in FIG. 17, the demand power used in a house is indicated by a solid line, the power generated by the solid oxide fuel cell 1 is indicated by a broken line, and the integrated value Ni serving as an index of the amount of stored heat is indicated by a one-dot chain line.

  First, at times t40 to t41 when the family is sleeping, the demand power used in the house is small, and the demand power increases when the family wakes up at time t41. Along with this, the generated power of the solid oxide fuel cell 1 also increases, and the power exceeding the rated power of the fuel cell is supplied from the grid power among the demand power. In addition, since the state where the electric power used is low for about 6 to 8 hours while the family is sleeping, the heat storage amount (integrated value Ni) estimated by the heat storage amount estimation unit 110b is 0 or at the wake-up time t41. The value is very small.

  When the generated power increases at time t41 and the fuel cell module 2 is operated at a temperature higher than the heat storage temperature Th, the amount of heat storage gradually increases, and increases to about 1 which is the maximum integrated value at time t42. Thereafter, when the householder goes out at time t43, the power demand decreases rapidly. As described above, when the generated power decreases in a state where the heat storage amount is equal to or greater than the change execution heat storage amount, the basic fuel supply table is corrected by the fuel table changing unit 110a, and the fuel utilization rate in the small power generation is increased. When the operation with an increased fuel utilization rate is performed, the amount of heat accumulated in the heat insulating material 7 is used, so the integrated value Ni also decreases. In the present embodiment, it is possible to perform an operation with an increased fuel utilization rate for about 1 to 3 hours.

Next, when the householder comes home at time t44, the demand power increases again. The integrated value Ni increases after an increase in demand power at time t44 (time t44 to t45) and reaches the maximum value again. Next, at time t46, the householder goes to bed and the demand power decreases, and then the operation with an increased fuel utilization rate is performed (after time t46).
When the demand power in the house changes in this way, an operation that increases the fuel utilization rate using the amount of heat accumulated in the heat insulating material 7 is performed twice a day. The operation period in which the fuel utilization rate is increased reaches 20 to 50% of the period in which the generated power is low, and greatly improves the overall energy efficiency of the solid oxide fuel cell 1.

  In the conventional solid oxide fuel cell, when the generated power is small, the generated heat is reduced, so that the temperature of the fuel cell module is likely to decrease. For this reason, when the amount of power generated is small, the fuel utilization rate is lowered, and the fuel cell module is heated with fuel that has not been used for power generation to prevent an excessive temperature drop. In particular, in a solid oxide fuel cell of a type in which a reformer is disposed in a fuel cell module, an endothermic reaction occurs in the reformer, and thus a temperature drop is likely to occur.

  Further, in the above-described first embodiment of the present invention, the addition / subtraction value added to or subtracted from the integrated value Ni is calculated based only on the detected temperature Td as in the heat storage amount estimation table shown in FIG. However, as a modification, the addition / subtraction value can be determined in consideration of the output current. For example, the integrated value Ni can be calculated by integrating the value obtained by multiplying the addition / subtraction value determined based on the heat storage amount estimation table of FIG. 14 by the current correction coefficient shown in FIG. As shown in FIG. 18, the current correction coefficient is set to 1/7 when the output current is 3A or less, is set to 1/12 when the output current is 3A or more, and is linear from 1/7 to 1/12 between 3 and 4A. Has declined.

  By multiplying the current correction coefficient set in this way, the integrated value Ni rapidly increases and decreases in a region where the generated power is small, and the increase and decrease of the integrated value Ni becomes gentle in a region where the generated power is equal to or higher. For this reason, the integrated value Ni is rapidly reduced by the correction of the basic fuel supply table at the time of small power generation that consumes a large amount of heat accumulated in the heat insulating material 7. As a result, it is possible to more reliably prevent the risk of causing a significant temperature drop by overestimating the heat storage amount.

  In the embodiment described above, the addition / subtraction value to be added to or subtracted from the integrated value Ni is determined only by the detected temperature Td as shown in FIG. 15, but the addition / subtraction value is also dependent on the output current. The invention can also be configured. For example, when the output current is 3 A (output power 300 W) or less, the change reference temperature Tcr may be changed higher by about 2 ° C., and the entire graph of FIG. 15 may be shifted to the left by about 2 ° C. With this configuration, when the generated power is small, the change reference temperature Tcr is changed to a high value, and the estimated value of the heat storage amount is calculated to a small value. As a result, the correction amount for increasing the fuel utilization rate is reduced, so that the fuel utilization rate is significantly improved in the region where the generated power is small and the absolute amount of the fuel supply amount is small, and the fuel supply amount is reduced excessively. Can be suppressed.

  According to the solid oxide fuel cell 1 of the embodiment of the present invention, when the temperature rises during the start-up process and the amount of heat available in the heat insulating material 7 is accumulated, the high fuel utilization rate is increased. Since the power generation process is started by the efficient operation, the heat quantity deficient by increasing the fuel utilization rate is supplemented by the heat quantity accumulated in the heat insulating material 7. That is, during the start-up process, when the reformer temperature reaches the SR2 forced transition temperature, or when the reformer temperature reaches the power generation forced transition temperature, it is determined that the temperature rises excessively, and the integrated value Ni is greater than zero. In this case, it is determined that the heat quantity available for the heat insulating material 7 is accumulated. In such a case, the power generation process is started in a highly efficient operation in which the fuel supply amount is decreased and the fuel utilization rate is increased as compared with the normal fuel supply amount based on the basic fuel supply table. Due to the high-efficiency operation, the amount of heat accumulated in the heat insulating material 7 is consumed in the power generation process, and the excessive temperature rise is quickly eliminated. Further, since the amount of heat accumulated in the heat insulating material 7 is used in the power generation process, it is possible to eliminate the excessive temperature rise while improving energy efficiency.

In general, in the solid oxide fuel cell 1, the operation state tends to become unstable when shifting from the start-up process to the power generation process, and there is a risk that the fuel cell module 2 will undergo a rapid temperature drop. According to the solid oxide fuel cell 1 of the present embodiment, the fuel supply amount is kept constant during SR2 (t ₂₉ to t _{30 in} FIG. 10) during the start-up process, and the SR2 exceeds the predetermined power generation transition time. Is maintained. For this reason, the operation state is stabilized at the time of transition to the power generation process (t _{30 in} FIG. 10), and the risk of a sudden temperature drop can be avoided. Further, the solid oxide fuel cell 1 of this embodiment, the heat storage amount accumulated in the heat insulating material 7, based from SR2 (from t ₂₉ in FIG. 10) to the integration of the initiated subtraction value estimation Therefore, the heat storage amount can be accurately estimated, and the risk of a temperature decrease due to the reduction of the fuel supply amount by high-efficiency operation when shifting to the power generation process can be avoided more reliably.

  In the solid oxide fuel cell 1 of the present embodiment, the fuel supply amount in SR2 is set to a fuel supply amount corresponding to about 500 W of generated power that is an intermediate band of the power range. When the temperature of the fuel cell module 2 rises excessively during the startup process, the control unit 110 starts the power generation process with the generated power in the intermediate band or less regardless of the demand power.

  In the basic fuel supply amount table (FIG. 12) of the solid oxide fuel cell 1, the fuel cell module is operated so that the fuel utilization rate is high in the high power generation band in the power range, and the fuel cell module in the low power generation band. In order to maintain the temperature of 2, the fuel utilization rate is lowered. For this reason, when the power generation process is operated in the high power generation band, there is little room for further increasing the fuel utilization rate, and it is difficult to consume the amount of heat accumulated in the heat insulating material 7. According to the solid oxide fuel cell 1 of the present embodiment, in the case of excessive temperature rise, the power generation process is started with the generated power below the intermediate band regardless of the demand power, so that the fuel utilization rate is increased. Thus, the amount of heat accumulated in the heat insulating material 7 is quickly consumed, and the excessive temperature rise can be quickly resolved.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, the integration starts with 0.7, which is larger than the intermediate value 0.5 between the heat storage maximum value 1 and the heat storage minimum value 0, as an initial value. Therefore, the heat amount accumulated in the heat insulating material 7 until the integration is started in SR2 can be reflected in the estimated value of the heat storage amount.

  Further, according to the solid oxide fuel cell 1 of the present embodiment, when the reformer 20 exceeds the SR2 forced transition temperature, it is forcibly shifted to SR2 (FIG. 11, steps S4 to S6). It is possible to wait for the temperature rise of the fuel cell unit 16 while executing SR2 in which the fuel supply amount is reduced as compared with SR1, and it is possible to prevent an excessive temperature rise of the reformer 20.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, weak power is generated during the execution of SR2 (FIG. 11, step S9), so that the operating state during the startup process can be approximated to the power generation process. It is possible to shift to the power generation process more smoothly.

Next, a solid oxide fuel cell according to a second embodiment of the present invention will be described with reference to FIGS.
The solid oxide fuel cell of the present embodiment differs from the first embodiment described above in the high efficiency control (step S15 in FIG. 11) executed by the control unit 110 in the power generation process. Accordingly, here, only the portions of the second embodiment of the present invention that are different from the first embodiment will be described, and descriptions of similar configurations, operations, and effects will be omitted.

  In the first embodiment described above, the fuel supply amount is determined based on the basic fuel supply table according to the demand power, and the determined fuel supply amount is decreased based on the heat amount accumulated in the heat insulating material 7. The fuel usage rate was changed. On the other hand, in the solid oxide fuel cell according to the second embodiment, the process of determining the fuel supply amount by the basic fuel supply table and changing the fuel supply amount based on the estimated heat storage amount is not executed, and the fuel supply amount is It is directly calculated based on the detected temperature Td and the like. However, in the present embodiment, the fuel supply amount that is directly determined based on the detected temperature Td and the like is the amount of heat accumulated in the heat insulating material 7 and the like, and in a state where the heat storage amount is large, Since the fuel utilization rate is improved by using heat storage, it can be said that the technical idea similar to that of the first embodiment is realized.

  FIG. 19 is a graph schematically showing the relationship between the change in demand power, the fuel supply amount, and the current actually taken from the fuel cell module 2. FIG. 20 is a graph showing an example of the relationship between the power generation air supply amount, the water supply amount, the fuel supply amount, and the current actually taken from the fuel cell module 2.

  As shown in FIG. 19, the fuel cell module 2 is controlled so as to be able to generate electric power according to the demand electric power shown in the uppermost stage of FIG. Based on the demand power, the control unit 110 sets a fuel supply current value If, which is a target current to be generated by the fuel cell module 2, as shown in the second graph of FIG. Although the fuel supply current value If is set so as to substantially follow the change in demand power, the response speed of the fuel cell module 2 is extremely slow with respect to the change in demand power. It is set so as to follow the demand power gently without following the change. In addition, when the demand power exceeds the maximum rated power of the solid oxide fuel cell, the fuel supply current value If follows the current value corresponding to the maximum rated power and is set to a current value higher than that. There is no.

  As shown in the third graph of FIG. 19, the control unit 110 controls the fuel flow rate adjustment unit 38, which is a fuel supply unit, so as to generate a fuel supply amount at a flow rate that can generate power corresponding to the fuel supply current value If. Fr is supplied to the fuel cell module 2. If the fuel utilization rate, which is the ratio of the fuel actually used for power generation with respect to the fuel supply amount, is constant, the fuel supply current value If and the fuel supply amount Fr are proportional. The graph of FIG. 19 is drawn on the assumption that the fuel supply current value If and the fuel supply amount Fr are proportional, but as will be described later, the fuel utilization rate is actually not constant in this embodiment as well.

  Further, as shown in the lowermost graph in FIG. 19, the control unit 110 outputs a signal that instructs the inverter 54 about the extractable current Iinv that is a current value that can be extracted from the fuel cell module 2. The inverter 54 extracts current (electric power) from the fuel cell module 2 within the range of the extractable current Iinv according to the demand power that changes suddenly every moment. The portion where the demand power exceeds the extractable current Iinv is supplied from the grid power. Here, as shown in FIG. 19, when the current tends to increase, the extractable current Iinv instructed by the control unit 110 to the inverter 54 changes so as to be delayed by a predetermined time with respect to the change in the fuel supply amount Fr. Is set. For example, at time t10 in FIG. 19, after the fuel supply current value If and the fuel supply amount Fr start to increase, an increase in the extractable current Iinv is started with a delay. Also at time t12, after the fuel supply current value If and the fuel supply amount Fr increase, the increase of the extractable current Iinv is started with a delay. As described above, after the fuel supply amount Fr is increased, the timing at which the electric power actually extracted from the fuel cell module 2 is increased is delayed so that the fuel supplied to the fuel cell module 2 passes through the reformer 20 and the like. A time delay until the fuel cell stack 14 is reached and a time delay until the actual power generation reaction becomes possible after the fuel reaches the battery cell stack 14 are dealt with. This reliably prevents the fuel battery cell unit 16 from being depleted of fuel and damaging the fuel battery cell unit 16.

  FIG. 20 shows in more detail the relationship between the power supply air supply amount, the water supply amount, and the fuel supply amount and the extractable current Iinv. Note that the graphs of the power supply air supply amount, the water supply amount, and the fuel supply amount shown in FIG. 20 are all converted into current values corresponding to the respective supply amounts. That is, if the supplied power generation air, water, and fuel are all set to supply amounts that are used for power generation, the graphs of the respective supply amounts overlap the graph of the extractable current Iinv. It has been converted. Therefore, the amount of deviation of each supply amount graph with respect to the extractable current Iinv corresponds to the surplus of each supply amount. The remaining fuel that is not used for power generation is burned in the combustion chamber 18 that is a combustion section above the fuel cell stack 14 and is used for heating in the fuel cell module 2.

  As shown in FIG. 20, the power supply air supply amount, the water supply amount, and the fuel supply amount always exceed the extractable current Iinv, and the current exceeding the current that can be generated by each supply amount is greater than the fuel cell module 2. The fuel cell unit 16 is prevented from being damaged by fuel exhaustion, air exhaustion, and the like. Further, the water supply amount is set to a supply amount capable of steam reforming all of the supplied fuel with respect to the fuel supply amount supplied exceeding the extractable current Iinv. That is, the amount of water supplied is the ratio of the amount of water vapor necessary for steam reforming and the amount of carbon contained in the fuel, so that all of the supplied fuel is steam reformed. It is set in consideration. This prevents carbon deposition in the reformer. Further, in the region A and region C of FIG. 20 in which the extractable current Iinv tends to increase with the increase in demand power, a margin such as the fuel supply amount is larger than the region B in which the extractable current Iinv is flat. Is set large (low fuel utilization). In addition, when the generated power is increased, the fuel supply amount supplied to the fuel cell module 2 is increased by a power extraction delay means (not shown) built in the control unit 110, and then the fuel cell is delayed. The generated power output from the module 2 is increased. That is, after the fuel supply amount is changed according to the change in demand power, the power actually output from the fuel cell module 2 is changed with a delay. Furthermore, when the extractable current Iinv is suddenly reduced according to the reduction in demand power (the initial period of the region C and the region D), each supply amount decreases with a predetermined time delay from the decrease of the extractable current Iinv. Is done. Therefore, a very large amount of residual fuel is generated during a predetermined time after the extractable current Iinv suddenly decreases. Such a rapid decrease in the extractable current Iinv is performed in order to prevent a reverse current flow when the demand power rapidly decreases. Thus, when the generated power is increased and when the generated power is decreased, more residual fuel is generated than when the generated power is constant, and this residual fuel is used for heating the fuel cell module 2. Will be. For this reason, the fuel cell module 2 is strongly heated not only when the fuel cell module 2 is operated for a long time with high generated power but also when the generated power is frequently increased or decreased, and a large amount of heat is accumulated in the heat insulating material 7. Is done.

  In the solid oxide fuel cell of this embodiment, after operating for a long time with high generated power, not only the heat storage is used when the generated power decreases, but also the amount of heat that is being accumulated due to the increase or decrease of the generated power, etc. Are used sequentially depending on the situation.

Next, a procedure for determining the power generation air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td will be described with reference to FIGS.
FIG. 21 is a flowchart showing a procedure for determining the power supply air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td. FIG. 22 is a graph showing an appropriate temperature of the fuel cell stack 14 with respect to the generated current. FIG. 23 is a graph showing the fuel utilization rate determined according to the integrated value. FIG. 24 is a graph showing a range of values of fuel utilization rates that can be determined for each generated current. FIG. 25 is a graph showing the air utilization rate determined according to the integrated value. FIG. 26 is a graph showing a range of air utilization values that can be determined for each generated current. FIG. 27 is a graph for determining the water supply amount with respect to the determined air utilization rate. FIG. 28 is a graph showing an appropriate generated voltage of the fuel cell module 2 with respect to the generated current.

  As indicated by a one-dot chain line in FIG. 22, in this embodiment, an appropriate temperature Ts (I) of the fuel cell stack 14 is defined for the current to be generated by the fuel cell module 2. The control unit 110 controls the fuel supply amount and the like so that the temperature of the fuel cell stack 14 approaches the appropriate temperature Ts (I). That is, the control unit 110 roughly indicates that when the temperature of the fuel cell stack 14 is higher than the generated current (when the temperature of the fuel cell stack 14 is above the one-dot chain line in FIG. 22). The fuel utilization rate is increased, the amount of heat accumulated in the heat insulating material 7 and the like is actively consumed, and the temperature in the fuel cell module 2 is lowered. On the other hand, when the temperature of the fuel cell stack 14 is lower than the generated current, the fuel utilization rate is reduced so that the temperature in the fuel cell module 2 does not decrease. Specifically, the fuel utilization rate is not determined based on the simple detected temperature Td, but is calculated by adding the addition / subtraction values determined based on the detected temperature Td and the like to reflect the heat storage. The fuel utilization rate and the like are determined based on this amount. An estimated value of the heat storage amount by integrating the addition and subtraction values is calculated by the heat storage amount estimation means 110b built in the control unit.

  The flowchart shown in FIG. 21 determines the power generation air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td and the like detected by the power generation chamber temperature sensor 142 that is a temperature detection means. It is executed at the time interval.

First, in step S31 of FIG. 21, the first addition / subtraction value M1 is calculated based on the detected temperature Td and FIG. First, when the detected temperature Td is within a predetermined temperature range (between two solid lines in FIG. 22) with respect to the appropriate temperature Ts (I) of the fuel cell stack 14, the first addition / subtraction value M1. Is set to zero.
That is, the detected temperature Td is
Ts (I) −Te ≦ Td ≦ Ts (I) + Te
Is within the range, the first addition / subtraction value M1 = 0. Here, Te is the first addition / subtraction value threshold temperature. In the present embodiment, the first addition / subtraction value threshold temperature Te is 3 ° C.

Further, the detected temperature Td is lower than the appropriate temperature Ts (I),
Td <Ts (I) −Te (4)
Is within the range (below the lower solid line in FIG. 22), the first addition / subtraction value M1 is
M1 = Ki × (Td− (Ts (I) −Te)) (5)
Calculated by At this time, the first addition / subtraction value M1 is a negative value (subtraction value). Ki is a predetermined proportionality constant.

Further, the detected temperature Td is higher than the appropriate temperature Ts (I),
Td> Ts (I) + Te (6)
Is within the range (above the upper solid line in FIG. 22), the first addition / subtraction value M1 is
M1 = Ki × (Td− (Ts (I) + Te)) (7)
Calculated by At this time, the first addition / subtraction value M1 is a positive value (addition value). As described above, the first addition / subtraction value M1 is determined based on the generated current in addition to the detected temperature Td, and the heat storage amount is estimated by integrating the value. That is, the appropriate temperature Ts (I) is set to be different depending on the generated current (electric power), and the value of (Ts (I) + Te) determined based on the appropriate temperature Ts (I) and (Ts Based on the value of (I) −Te), the first addition / subtraction value M1 is determined as a positive or negative value.

  If the detected temperature Td exceeds (Ts (I) + Te), the first addition / subtraction value M1 becomes a positive value, and the fuel supply amount is changed to increase the fuel utilization rate as will be described later. In the document, the temperature (Ts (I) + Te) for each generated power is referred to as the fuel utilization rate change temperature. Moreover, after the fuel utilization rate change temperature (Ts (I) + Te) is exceeded, after shifting to the high efficiency control in which the fuel utilization rate is increased, the target temperature range in which the amount of heat accumulated from the high efficiency control is not consumed. As will be described later, the timing for returning to control is when the integrated value N1id such as the first addition / subtraction value M1 has decreased to zero. For this reason, even after the detected temperature Td falls below the fuel utilization rate changing temperature (Ts (I) + Te), the integrated value N1id is maintained at a value larger than 0 for a while, and high efficiency control is performed. Therefore, the target temperature range control return temperature for returning from the high efficiency control to the target temperature range control is lower than the fuel utilization rate changing temperature.

  Next, in step S32 of FIG. 21, a second addition / subtraction value M2 is calculated based on the latest detected temperature Td and the detected temperature Tdb detected one minute ago. First, when the absolute value of the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is less than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is set to zero. In the present embodiment, the second addition / subtraction value threshold temperature is 1 ° C.

When the change temperature difference that is the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is equal to or higher than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is:
M2 = Kd × (Td−Tdb) (8)
Calculated by The second addition / subtraction value M2 becomes a positive value (addition value) when the detected temperature Td tends to increase, and becomes a negative value (subtraction value) when the detected temperature Td tends to decrease. Kd is a predetermined proportional constant. Therefore, when the detected temperature Td is increasing, the second addition / subtraction value M2, which is the quick response estimated value, is greatly increased in the region where the change temperature difference (Td−Tdb) is large compared to the region where the change temperature difference is small. Is done. On the other hand, when the detected temperature is low, the second addition / subtraction value M2 is greatly reduced in the region where the absolute value of the change temperature difference (Td−Tdb) is large than in the region where the absolute value of the change temperature difference is small. Is done.

  In the present embodiment, the proportionality constant Kd is a constant value, but as a modification, different proportionality constants Kd can be used depending on whether the change temperature difference is positive or negative. For example, the proportionality constant Kd can be set large when the change temperature difference is negative. As a result, when the detected temperature is lowered, the estimated quick response value is changed more rapidly with respect to the change temperature difference than when the detected temperature is increased. Alternatively, as a modification, the proportionality constant Kd can be set larger in the region where the absolute value of the change temperature difference is large than in the small region. As a result, in the region where the absolute value of the change temperature difference is large, the estimated quick response value is changed more rapidly than the region where the absolute value of the change temperature difference is small. Further, the change of the proportional constant Kd based on the sign of the change temperature difference can be combined with the change of the proportional constant Kd based on the magnitude of the absolute value of the change temperature difference.

  Next, in step S33 of FIG. 21, the first addition / subtraction value M1 calculated in step S31 and the second addition / subtraction value M2 calculated in step S32 are integrated into the first integration value N1id. In the first integrated value N1id, the available heat storage amount accumulated in the heat insulating material 7 and the like is reflected by the first addition / subtraction value M1, and the latest change in the detected temperature Td is reflected by the second addition / subtraction value M2. . That is, the first integrated value N1id can be used as an estimated value of the available heat storage amount accumulated in the heat insulating material 7 or the like. Further, the integration is performed every time the flowchart of FIG. 21 is executed continuously after the operation of the solid oxide fuel cell is started, and the first addition value N1id and the first addition / subtraction value M1 are added to the previously calculated first integration value N1id. The 2 addition / subtraction value M2 is added or subtracted and updated to a new first integrated value N1id. The first integrated value N1id is limited to take a value between 0 and 4, and when the first integrated value N1id reaches 4, the value is held at 4 until the next subtraction is performed. When the first integrated value N1id decreases to 0, the value is held at 0 until the next addition is performed.

  In step S33, in addition to the first integrated value N1id, the value of the second integrated value N2id is also calculated. As will be described later, the second integrated value N2id is calculated in the same manner as the first integrated value N1id until the fuel cell module 2 is deteriorated, and takes the same value as the first integrated value N1id.

As described above, in the present embodiment, the integrated value is calculated by integrating the sum of the first addition / subtraction value M1 and the second addition / subtraction value M2 to the first integration value N1id. That is,
N1id = N1id + M1 + M2 (9)
Thus, the first integrated value N1id is calculated. Here, as a modification, the integrated value may be calculated by integrating the product of the first addition / subtraction value M1 and the second addition / subtraction value M2. That is, in this modification, the first integrated value N1id is
N1id = N1id + Km × M1 × M2 (10)
Is calculated by Here, Km is a variable coefficient that is changed according to a predetermined condition. In this modified example, when the absolute value of the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is less than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is 1. Is done.

Further, in step S34 of FIG. 21, the fuel utilization rate is determined using the graphs of FIGS. 23 and 24 based on the calculated first integrated value N1id.
FIG. 23 is a graph showing a set value of the fuel utilization rate Uf with respect to the calculated first integrated value N1id. As shown in FIG. 23, when the first integrated value N1id is 0, the fuel usage rate Uf is set to the minimum fuel usage rate Ufmin, which is the minimum value. Further, as the first integrated value N1id increases, the fuel utilization rate Uf also increases, and becomes the maximum fuel utilization rate Ufmax that is the maximum value at the first integrated value N1id = 1. During this time, the fuel utilization rate Uf has a small slope in the region where the first integrated value N1id is small, and the slope increases as the first integrated value N1id approaches 1. That is, in the region where the estimated heat storage amount is large, the fuel utilization rate Uf is significantly changed with respect to the change in the estimated heat storage amount, compared to the region where the estimated heat storage amount is small. In other words, the fuel supply amount is decreased so that the fuel utilization rate Uf is significantly increased as the estimated heat storage amount is larger. Further, when the first integrated value N1id is larger than 1, the fuel usage rate Uf is fixed to the maximum fuel usage rate Ufmax. Specific values of the minimum fuel utilization rate Ufmin and the maximum fuel utilization rate Ufmax are determined by the graph shown in FIG. 24 based on the generated current. Thus, when it is estimated that the amount of heat that can be used is accumulated in the heat insulating material 7 and the like, the fuel utilization rate is higher for the same generated power than in the case where the amount of available heat is not accumulated. The fuel supply is reduced to be higher.

  FIG. 24 is a graph showing the range of values that the fuel utilization rate Uf can take for each generated current, and shows the maximum value and the minimum value of the fuel utilization rate Uf for each generated current. As shown in FIG. 24, the minimum fuel utilization rate Ufmin for each generated current is set to increase as the generated current increases. That is, the fuel utilization rate is set high when the generated power is large, and the fuel utilization rate is set low when the generated power is small. This straight line of the minimum fuel utilization rate Ufmin corresponds to the basic fuel supply table in FIG. 13 of the first embodiment, and when it is set to the fuel utilization rate on this straight line, it accumulates in the heat insulating material 7 and the like. The fuel cell module 2 can be thermally independent without using the amount of heat generated.

  On the other hand, the maximum fuel utilization rate Ufmax is set so as to change in a polygonal line with respect to each generated current. Here, the range of values that the fuel utilization rate Uf can take for each generated current (the difference between the maximum fuel utilization rate Ufmax and the minimum fuel utilization rate Ufmin) is the narrowest at the maximum generated current, and as the generated current decreases. Become wider. This is because, in the vicinity of the maximum generated current, the minimum fuel utilization rate Ufmin that can be thermally independent is high, and there is little room for increasing the fuel utilization rate Uf (reducing the fuel supply amount) even when using heat storage. Furthermore, since the minimum fuel utilization rate Ufmin that can be thermally self-sustained decreases as the generated current decreases, there is room for reducing the amount of fuel supplied by using heat storage, and when there is a large amount of heat storage, fuel use The rate Uf can be significantly increased. For this reason, in the region where the generated power is small, the fuel utilization rate is changed in a wider range than in the region where the generated power is large.

  Further, in a region where the generated current is very small and is less than or equal to the predetermined utilization rate suppressed power generation amount IU, the range of possible values of the fuel utilization rate Uf is set to be narrower as the generated power is reduced. This is because in the region where the generated current is small, the minimum fuel utilization rate Ufmin that can be thermally independent is low, and there is much room for improvement. However, in the region where the generated current is small, the temperature in the fuel cell module 2 is low. Therefore, if the fuel utilization rate Uf is significantly improved in this state and the amount of heat accumulated in the heat insulating material 7 or the like is consumed rapidly, There is a risk of causing an excessive temperature drop in the battery module 2. For this reason, in the area | region below the utilization factor suppression electric power generation amount IU in which an electric power generation current is very small, the change amount which raises the fuel utilization factor Uf is significantly suppressed, so that generated electric power becomes small. That is, the amount of change to decrease the fuel supply amount decreases as the power generation amount of the fuel cell module 2 decreases. This avoids the risk of a sudden temperature drop and makes it possible to use the accumulated heat for a long time.

  In the present embodiment, the fuel supply amount is reduced so that the fuel utilization rate Uf becomes higher than the minimum fuel utilization rate Ufmin by the fuel supply amount changing means 110a built in the control unit 110. Although this fuel supply amount changing means 110a does not change the basic fuel supply table, it operates to change the fuel supply rate as a base to increase the fuel utilization rate, so that the fuel table change in the first embodiment is performed. It is the structure corresponding to a means.

  In step S34 of FIG. 21, specific values of the minimum fuel utilization rate Ufmin and the maximum fuel utilization rate Ufmax are determined based on the generated current using the graph of FIG. Next, the determined minimum fuel utilization rate Ufmin and maximum fuel utilization rate Ufmax are applied to the graph of FIG. 23, and the fuel utilization rate Uf is determined based on the first integrated value N1id calculated in step S33.

Next, in step S35 of FIG. 21, the air utilization rate is determined using the graphs of FIGS. 25 and 26 based on the second integrated value N2id.
FIG. 25 is a graph showing a set value of the air utilization rate Ua with respect to the calculated second integrated value N2id. As shown in FIG. 25, when the second integrated value N2id is 0 to 1, the air utilization rate Ua is set to the maximum air utilization rate Uamax that is the maximum value. Further, as the second integrated value N2id increases beyond 1, the air utilization rate Ua decreases, and becomes the minimum air utilization rate Uamin that is the minimum value at the second integrated value N2id = 4. Thus, since the increased amount of air due to the reduction in the air utilization rate Ua acts as a cooling fluid, the setting of the air utilization rate Ua shown in FIG. 25 acts as a forced cooling means. Specific values of the minimum air utilization rate Uamin and the maximum air utilization rate Uamax are determined by the graph shown in FIG. 26 based on the generated current.

  FIG. 26 is a graph showing the range of values that the air utilization rate Ua can take for each generated current, and shows the maximum value and the minimum value of the fuel utilization rate Ua for each generated current. As shown in FIG. 26, the maximum air utilization rate Uamax for each generated current is set to be slightly increased as the generated current increases. On the other hand, the minimum air utilization rate Uamin decreases as the generated current increases. Reducing the air utilization rate Ua below the maximum air utilization rate Uamax (increasing the air supply amount) introduces more air into the fuel cell module 2 than is necessary for power generation. The temperature in the fuel cell module 2 is lowered. Therefore, when the temperature in the fuel cell module 2 rises excessively and the temperature needs to be lowered, the air utilization rate Ua is lowered. In this embodiment, when the minimum air utilization rate Uamin is decreased (the air supply amount is increased) as the generation current is increased, the air supply amount corresponding to the minimum air utilization rate Uamin is generated for power generation at a predetermined generation current. The maximum air supply amount of the air flow rate adjustment unit 45 will be exceeded. For this reason, in the region where the minimum air utilization rate Uamin is equal to or greater than the predetermined generated current indicated by the broken line in FIG. 26, the air utilization rate Ua set by the graph of FIG. 25 may not be realized. In this case, the actually supplied air supply amount is fixed to the maximum air supply amount of the power generation air flow rate adjustment unit 45 regardless of the set air utilization rate Ua. Along with this, the minimum air utilization rate Ua actually realized increases above a predetermined generated current. Further, when a power generation air flow rate adjustment unit having a large maximum air supply amount is used, the minimum air utilization rate Uamin in the portion indicated by the broken line in FIG. 26 can also be realized. The air utilization rate Ua defined by reaching the maximum air supply amount of the power generation air flow rate adjustment unit 45 is referred to as a limit minimum air utilization rate ULamin.

  In step S35 of FIG. 21, the specific values of the minimum air utilization rate Uamin and the maximum air utilization rate Uamax are determined based on the generated current using the graph of FIG. Next, the determined minimum air utilization rate Uamin and maximum air utilization rate Uamax are applied to the graph of FIG. 25, and the air utilization rate Ua is determined based on the second integrated value N2id calculated in step S33.

Next, in step S36 of FIG. 21, based on the air utilization rate Ua determined in step S35, S / C which is the ratio of the water vapor amount and the carbon amount is determined using FIG.
FIG. 27 is a graph in which the horizontal axis represents the air utilization rate Ua and the vertical axis represents the ratio S / C between the supplied water and the carbon contained in the fuel.

  First, in the region of the generation current (between Uamax and ULamin in FIG. 27) where the air utilization rate Ua set in step S35 is not defined by the maximum air supply amount of the power generation air flow rate adjustment unit 45, the amount of water vapor and carbon The value of the quantity ratio S / C is fixed at 2.5. The ratio of the amount of water vapor to the amount of carbon S / C = 1 means that the total amount of carbon contained in the supplied fuel is chemically steam-reformed by the supplied water (steam). means. Therefore, the ratio S / C = 2.5 of the amount of steam and the amount of carbon is 2.5 times the amount of steam (water) that is 2.5 times the minimum amount of steam that is chemically necessary for steam reforming the fuel. Means the state. Actually, carbon precipitation occurs in the reformer 20 at the amount of steam at which S / C = 1, so that the amount of steam at which S / C = 2.5 is for steam reforming the fuel. Appropriate amount.

  Next, in the region of the power generation current in which the air utilization rate Ua set in step S35 is limited by the maximum air supply amount of the power generation air flow rate adjustment unit 45, the water vapor amount and the carbon amount using the graph of FIG. The ratio S / C is determined. In FIG. 27, the horizontal axis represents the air utilization rate Ua, the air utilization rate Ua is larger, and the closer to the maximum air utilization rate Uamax, the smaller the air supply amount. On the other hand, when the air utilization rate Ua is lowered and approaches the minimum air utilization rate Uamin (broken line in FIG. 26), the air supply amount reaches the limit, and the air utilization rate Ua becomes the limit minimum air utilization rate ULamin. As shown in FIG. 27, when the air utilization rate Ua is larger than the limit minimum air utilization rate ULamin (the air supply amount is small), the ratio S / C = 2.5 of the water vapor amount and the carbon amount is set. . Further, when the air utilization rate Ua determined in step S35 is smaller than the limit minimum air utilization rate ULamin (the air supply amount is large) (between Uamin and ULamin in FIG. 27), the air utilization rate Ua decreases. The ratio S / C between the water vapor amount and the carbon amount is increased, and S / C = 3.5 is set at the minimum air utilization rate Uamin. That is, when the air utilization rate Ua determined in step S35 cannot be realized by the limit minimum air utilization rate ULamin (when the air utilization rate Ua is determined within the hatched range in FIG. 26), the water vapor amount and carbon Increase the quantity ratio S / C and increase the water supply. Thereby, the temperature of the reformed fuel gas flowing out from the reformer 20 is lowered, and the temperature in the fuel cell module 2 tends to be lowered. In this way, when the water supply amount is increased after the air supply rate Ua is decreased and the air supply amount is increased, the increased amount of water (water vapor) acts as a cooling fluid. The water supply setting shown acts as a forced cooling means.

  In step S37, specific fuel supply is performed based on the fuel utilization rate Uf, air utilization rate Ua, the ratio S / C of water vapor amount and carbon amount determined in steps S34, S35, and S36, and the generated current. Determine the volume, air supply, and water supply. That is, the actual fuel supply amount is calculated by dividing the fuel supply amount when the total amount is used for power generation by the determined fuel utilization rate Uf, and the total amount is used for power generation. The actual air supply amount is calculated by dividing the air supply amount by the determined air utilization rate Ua. Further, the water supply amount is calculated based on the calculated fuel supply amount and the ratio S / C of the water vapor amount and the carbon amount determined in step S36.

  Next, in step S38, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38, the power generation air flow rate adjustment unit 45, and the water flow rate adjustment unit 28 serving as water supply means, and the amount of fuel calculated in step S37. , Air and water are supplied, and one process of the flowchart of FIG. 21 is completed.

  Next, a time interval for executing the flowchart of FIG. 21 will be described. In the present embodiment, when the output current is large, the flowchart of FIG. 21 is executed every 0.5 seconds. As the output current decreases, it is doubled for 1 second, 4 times for 2 seconds, and 8 times. It is executed every 4 seconds. Thus, when the first and second addition / subtraction values are constant values, the change in the first or second integrated value per time becomes gentler as the output current is smaller. That is, the heat storage amount estimation unit 110b changes the estimated value of the heat storage amount rapidly with respect to time as the output current (generated power) increases. Thereby, the estimation of the heat storage amount by the integrated value well reflects the actual heat storage amount.

  Next, a procedure for determining the fuel supply amount, the air supply amount, and the water supply amount when the fuel cell module 2 is deteriorated will be described with reference to FIG. FIG. 28 is a diagram showing a generated voltage with respect to a generated current by the fuel cell module 2. In general, since an internal resistance exists in the fuel cell stack 14, the voltage decreases as the current output from the fuel cell module 2 increases as shown in FIG. The alternate long and short dash line shown in FIG. 28 indicates the relationship between the generated current and the generated voltage when the fuel cell module 2 is not deteriorated. On the other hand, when the fuel cell module 2 deteriorates, the internal resistance of the fuel cell stack 14 increases, so that the generated voltage for the same generated current decreases.

  In the solid oxide fuel cell according to the present embodiment, when the generated voltage drops by 10% or more with respect to the initial generated voltage and the generated voltage enters a region below the solid line in FIG. The fuel supply amount, air supply amount, and water supply amount are determined by the processing.

  That is, when the generated voltage is in the region below the solid line in FIG. 28, the integration of the first integrated value N1id is stopped and only the integration of the second integrated value N2id is continued in step S33 of FIG. . Accordingly, the value of the first integrated value N1id used when referring to the graph of FIG. 23 for determining the fuel utilization rate Uf is fixed to a constant value. As a result, the fuel utilization rate Uf is fixed until the generated voltage deviates from the region below the solid line in FIG. Thus, after the fuel cell module 2 has deteriorated, changes to increase the fuel utilization rate Uf are less than before the fuel cell module 2 deteriorates. On the other hand, the value of the second integrated value N2id used when referring to the graph of FIG. 26 for determining the air utilization rate Ua is increased or decreased as before, and the increase or decrease in the air utilization rate Ua is continued. Thus, the fuel utilization rate Uf is changed based on the deterioration of the fuel cell module 2 in addition to the first and second integrated values and the demand power corresponding to the estimated heat storage amount.

Next, the operation of the solid oxide fuel cell realized by the flowchart of FIG. 21 will be described.
First, when the value of the first integrated value N1id calculated in step S33 is 0, the fuel utilization rate Uf determined in step S34 is the minimum fuel utilization rate Ufmin (maximum fuel supply amount) in the generated current. Set to As a result, even when the value of the first integrated value N1id is 0 and the amount of heat accumulated in the heat insulating material 7 or the like is small, sufficient fuel is supplied so that the fuel cell module 2 can be thermally independent. When the value of the second integrated value N2id calculated in step S33 is 0 as in the case of the first integrated value N1id, the air utilization rate Ua determined in step S35 is the maximum air in the generated current. The utilization rate Uafmax (air supply amount minimum) is set. For this reason, the effect | action which cools the fuel cell stack 14 with the air for electric power generation introduced into the fuel cell module 2 is minimized, and the temperature of the fuel cell stack 14 can be made to rise.

  Next, when the detected temperature Td is higher than the appropriate temperature Ts (I) and the fuel cell module 2 is operated in a state of Td> Ts (I) + Te, the value of the first addition / subtraction value M1 becomes a positive value, The value of 1 integrated value N1id becomes larger than 0. Accordingly, in FIG. 23, a fuel utilization rate Uf higher than the minimum fuel utilization rate Ufmin is set, the fuel supply amount is decreased, and the amount of remaining fuel that is not used for power generation is decreased. The fuel utilization rate Uf is significantly increased by the fuel supply amount changing unit 110a as the value of the first integrated value N1id corresponding to the estimated heat storage amount increases. By increasing the fuel utilization rate Uf, the fuel supply amount is made smaller than the supply amount capable of self-sustaining heat, and high-efficiency control using the heat amount accumulated in the heat insulating material 7 or the like is executed. Since the amount of residual fuel is reduced and the amount of heat accumulated in the heat insulating material 7 or the like is used, the fuel supply amount changing means 110a suppresses the temperature rise in the fuel cell module 2 while continuing power generation. When the operation is continued in the state of Td> Ts (I) + Te, the integration of the positive first addition / subtraction value M1 is repeated, and the value of the first integration value N1id also increases. When the first integrated value N1id reaches 1, the fuel usage rate Uf is set to the maximum fuel usage rate Uafmax (fuel supply amount minimum). Thus, the fuel supplied to the fuel cell module 2 is determined based on the past history of the detected temperature Td reflecting the amount of heat accumulated in the heat insulating material 7 and the like.

  Even when the first integrated value N1id further increases and exceeds 1, as shown in FIG. 23, the fuel utilization rate Uf is maintained at the maximum fuel utilization rate Uafmax (minimum fuel supply amount). On the other hand, since the value of the second integrated value N2id that takes the same value as the first integrated value N1id (when the fuel cell module 2 is not deteriorated) also exceeds 1, the air utilization rate Ua decreases based on FIG. (Air supply amount increased). Thereby, the inside of the fuel cell module 2 tends to be cooled due to an increase in supplied air.

  On the other hand, when the detected temperature Td is lower than the appropriate temperature Ts (I) and the fuel cell module 2 is operated in a state where Td <Ts (I) −Te, the value of the first addition / subtraction value M1 is a negative value. Thus, the value of the first integrated value N1id is decreased. Thus, the fuel utilization rate Uf is maintained (first integrated value N1id> 1) or decreased (first integrated value N1id ≦ 1). Further, the air utilization rate Ua is increased (second integrated value N2id> 1) or maintained (second integrated value N2id ≦ 1). Thereby, the temperature in the fuel cell module 2 can be increased.

  The above is the operation of the solid oxide fuel cell focusing only on the first addition / subtraction value M1 calculated based on the history of the detected temperature Td. The first integrated value N1id and the second integrated value N2id are It is also affected by the addition / subtraction value M2. The fuel cell module 2, particularly the fuel cell stack 14, has a very large heat capacity, and the change in the detected temperature Td is extremely slow. For this reason, once the detected temperature Td starts to increase, it is difficult to suppress the temperature increase in a short time, and when the detected temperature Td starts to decrease, this is returned to the upward trend. Takes a long time. For this reason, when the detected temperature Td tends to increase or decrease, it is necessary to react quickly to correct the first and second integrated values.

  That is, when the latest detected temperature Td is higher than the detected temperature Tdb one minute ago by the second addition / subtraction value threshold temperature, the second addition / subtraction value M2 becomes a positive value, and the first and second integrated values increase. Is done. Thereby, it can reflect in the 1st, 2nd integrated value that the detected temperature Td entered into the upward tendency. Similarly, when the latest detected temperature Td is lower than the detected temperature Tdb one minute ago by the second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is a negative value, and the first and second integrated values are Will be reduced. In other words, the second addition / subtraction value M2, which is a rapid response estimated value, is calculated based on the change temperature difference that is the difference between the latest detected temperature Td detected by the power generation chamber temperature sensor 142 and the past detected temperature Tdb. Therefore, when the detected temperature Td is drastically reduced, the amount of change that increases the fuel utilization rate Uf is greatly suppressed, and the generated power is reduced by the utilization rate-suppressed power generation amount, compared with the case where the detected temperature Td is gradually decreasing. Since the maximum fuel utilization rate Ufmax is also set low in the region below IU, the amount of change is more greatly suppressed. Thereby, it can reflect in the 1st, 2nd integrated value that detected temperature Td entered into the fall tendency. Thus, in the present embodiment, the difference based on the integrated value of the first addition / subtraction value M1 determined based on the detected temperature Td and the difference between the newly detected detected temperature Td and the detected temperature Tdb detected in the past. The amount of heat storage is estimated based on the value. That is, in the present embodiment, the integrated value of the first addition / subtraction value M1, which is a basic estimated value calculated based on the history of the detected temperature Td, and the detected temperature Td in a period shorter than the history of calculating the basic estimated value. Based on the second addition / subtraction value M2, which is a quick response estimated value calculated based on the rate of change, the heat storage amount estimation unit 110b estimates the heat storage amount. Thus, in this embodiment, the heat storage amount is estimated based on the sum of the basic estimated value and the quick response estimated value.

  Note that the temperature change of the fuel cell module 2 is extremely slow compared to 1 minute, which is the interval at which the detected temperatures Td and Tdb are detected, so the second addition / subtraction value M2 is often zero. For this reason, the first and second integrated values are mainly governed by the first addition / subtraction value M1, and when the detected temperature Td increases or decreases, the second addition / subtraction value M2 becomes the first and second integration values. Acts to correct the value of. Thus, in addition to the detected temperature history, the most recent change in the detected temperature Td is added to the estimated value of the heat storage amount by the second addition / subtraction value M2. For this reason, when the most recent change in detected temperature Td is large (change greater than or equal to the second addition / subtraction value threshold temperature), since the second addition / subtraction value M2 has a value, the estimated value of the heat storage amount is corrected, and the fuel utilization rate Uf is significantly changed.

Next, the limitation on the variable range of the generated power will be described with reference to FIGS.
As described above, in the solid oxide fuel cell according to the present embodiment, the amount of heat accumulated in the heat insulating material 7 and the like is used to increase the fuel utilization rate, and the fuel is obtained by actively utilizing the heat storage. The temperature in the battery module 2 is controlled to an appropriate temperature. On the other hand, as described with reference to FIGS. 19 and 20, when the power generated by the fuel cell module 2 is frequently increased or decreased according to the demand power, the temperature in the fuel cell module 2 may excessively increase. . Such an excessive temperature rise can be suppressed by increasing the fuel utilization rate and positively using the amount of heat accumulated in the heat insulating material 7 or the like. However, as described with reference to FIG. 24, in the region where the power to be generated is large, the set minimum fuel utilization rate Ufmin is a large value, so there is little room for increasing the fuel utilization rate and using the heat storage. . Therefore, when the generated power is large, it is difficult to effectively reduce the excessively increased temperature in the fuel cell module 2 even if the fuel utilization rate is increased and heat storage is used. For this reason, in this embodiment, when the excessive temperature rise in the fuel cell module 2 occurs, the variable range in which the generated power follows the demand power is limited to be low. As a result, the fuel cell module 2 is operated with a small amount of generated power, so that room for using heat storage is increased, and the temperature in the fuel cell module 2 can be effectively reduced. Moreover, the temperature rise by the frequent increase / decrease in generated electric power is suppressed by narrowing the variable range which makes generated electric power track demand electric power.

  The temperature rise in the fuel cell module 2 due to frequent increase / decrease in demand power described with reference to FIGS. 19 and 20 also occurs in the solid oxide fuel cell according to the first embodiment of the present invention described above. Therefore, the limitation of the variable range of the generated power described below with reference to FIGS. 29 to 32 can also be implemented in combination with the above-described first embodiment of the present invention.

  FIG. 29 is a flowchart showing a procedure for limiting the range of power generated by the fuel cell module in the present embodiment. FIG. 30 is a map showing current limitations on the generated current and the detected temperature Td. FIG. 31 is a time chart showing an example of the operation in the present embodiment. FIG. 32 is a graph showing an example of the relationship between the temperature in the fuel cell module and the maximum power that can be generated.

  First, as shown by the solid line in FIG. 30, in the solid oxide fuel cell of this embodiment, an appropriate temperature in the fuel cell module 2 is set for each generated current. This appropriate temperature corresponds to the alternate long and short dash line in FIG. In addition, as shown in FIG. 30, a current maintaining region is set in a region where the temperature is higher than the appropriate temperature. The minimum temperature of the current maintaining region is set to be different depending on the power generated by the fuel cell module 2, and the minimum temperature of the current maintaining region is set higher as the generated power is larger. Further, the minimum temperature of the current maintenance region for each generated power is set such that the difference from the appropriate temperature of the fuel cell module 2 increases as the generated power decreases. When the operating state of the fuel cell module 2 enters this current maintenance region, an increase in output current from the fuel cell module 2 is prohibited. Furthermore, a current reduction region is set in a region where the temperature is higher than the current maintaining region. When the operating state enters this current reduction region, the output current from the fuel cell module 2 is forcibly reduced. An air cooling region is set in a region where the temperature is higher than the current lowering region. When the operating state enters this air cooling region, the supply amount of power generation air is set to the maximum flow rate that can be supplied by the power generation air flow rate adjustment unit 45. An operation stop region is set in a region where the temperature is higher than the air cooling region. When the operation state enters this operation stop region, the power generation by the fuel cell module 2 is stopped to prevent a failure of the solid oxide fuel cell.

  Further, when the detected temperature Td rises rapidly, the temperature that defines the current maintaining region is lowered as shown by a one-dot chain line in FIG. In this case, the temperature defining the current reduction region is lowered as shown by a two-dot chain line in FIG. As a result, when the detected temperature Td rises rapidly, current limitation is performed at an early stage to reliably suppress an excessive temperature rise.

Next, a procedure for limiting the current generated by the fuel cell module will be described with reference to FIG.
First, in step S41 of FIG. 29, the detected temperature Td is read. Next, in step S42, the detected temperature Td read in step S41 is compared with the detected temperature Td before a predetermined time. If the difference between the detected temperature Td read in step S41 and the detected temperature Td before a predetermined time is equal to or lower than a predetermined threshold temperature, the process proceeds to step S43.

  In step S43, a basic characteristic indicated by a solid line in FIG. 30 is selected as a map for determining the temperature region. On the other hand, if the difference between the latest detected temperature Td and the detected temperature Td before the predetermined time is larger than the predetermined threshold temperature, the process proceeds to step S44. In step S44, as a map for determining the temperature region, FIG. The rapid temperature rise characteristics indicated by the alternate long and short dashed lines are selected.

  Next, in step S45, it is determined whether or not the detected temperature Td is within the operation stop region. In the present embodiment, when the detected temperature Td is equal to or higher than the operation stop threshold temperature of 780 ° C., it is determined that the operation is in the operation stop region. If it is determined that the detected temperature Td is within the operation stop region, the process proceeds to step S46. In step S46, power generation by the fuel cell module 2 is stopped and the solid oxide fuel cell system is urgently stopped.

  On the other hand, if it is determined in step S45 that the detected temperature Td is not within the operation stop region, the process proceeds to step S47. In step S47, it is determined whether or not the detected temperature Td is within the air cooling region. In the present embodiment, when the detected temperature Td is equal to or higher than the forced cooling threshold temperature of 750 ° C., it is determined that the air is in the air cooling region. If it is determined that the detected temperature Td is within the air cooling region, the process proceeds to step S48.

  In step S <b> 48, the generated current is fixed to 1 A, which is the minimum current, and this current is not output to the inverter 54 but is consumed by the auxiliary unit 4. The air supply amount is set to the maximum flow rate that can be supplied by the power generation air flow rate adjustment unit 45. Further, the supply amount of water is also increased, the ratio of the water vapor amount to the carbon amount S / C = 4 is set, and one process of the flowchart of FIG. 29 is completed.

  On the other hand, if it is determined in step S47 that the detected temperature Td is not within the air cooling region, the process proceeds to step S49. In step S49, it is determined whether or not the detected temperature Td and the generated current are within the current decrease region. If they are within the current decrease region, the process proceeds to step S50.

  In step S50, the current generated by the fuel cell module 2 is forcibly reduced to 4A or less. That is, the upper limit value of the electric power generated by the fuel cell module 2 is reduced to a temperature rise suppression power (400 W) higher than a half of 700 W which is the maximum rated power. Thereafter, when the demand power decreases, the upper limit value of the generated power (current) is decreased following the demand power, and even if the demand power increases, the generated current is maintained without increasing. Thereby, the one-time process of the flowchart of FIG. 29 is completed. Such limitation of the generated current is continued until the detected temperature Td and the generated current are out of the current decrease region.

  On the other hand, if it is determined in step S49 that the detected temperature Td and the generated current are not within the current decrease region, the process proceeds to step S51. In step S51, it is determined whether or not the detected temperature Td and the generated current are within the current maintenance region. If they are within the current maintenance region, the process proceeds to step S52.

  In step S52, an increase in the generated current is prohibited, and thereafter, even if the demand power increases, the generated current is maintained without increasing. In addition, when the demand power decreases, the upper limit value of the generated current (electric power) is decreased following the decrease in the demand power, and even if the demand power increases, the upper limit value of the generated current (electric power) is increased. Maintained without. Such limitation of the generated current is continued until the detected temperature Td and the generated current are out of the current maintaining region and the excessive temperature rise of the fuel cell module 2 is resolved. Thereby, the one-time process of the flowchart of FIG. 29 is completed.

  In the present embodiment, for each generated current, when the detected temperature Td exceeds the minimum temperature of the current maintenance region, the regulation of the generated power is started. Therefore, in this specification, the minimum of the current maintenance region for each generated current The temperature is referred to as a generated power regulation temperature (FIG. 30). In this embodiment, the generated power regulation temperature is set to be higher than the fuel utilization rate change temperature (Ts (I) + Te) (FIG. 22) at which the change to increase the fuel utilization rate is started.

  On the other hand, when it is determined in step S51 that the detected temperature Td and the generated current are not within the current maintaining region, the process proceeds to step S53. In step S53, the generated current is not limited, and control using heat storage is performed.

Next, an example of generated current limitation will be described with reference to FIG.
The time chart shown in FIG. 31 is a diagram schematically showing changes in detected temperature Td, target current, generated current, fuel supply amount, fuel utilization rate, and air supply amount in order from the top. Here, the target current is a current obtained from demand power and generated voltage.

First, at time t20 in FIG. 31, the generated current is about 6A, and the detected temperature Td is in a state slightly lower than the appropriate temperature in the generated current about 6A (corresponding to t20 in FIG. 30).
Next, at times t20 to t21, since the demand power repeatedly fluctuates greatly in a short time, the target current also greatly increases and decreases, and the generated current also increases and decreases to follow this. On the other hand, as described with reference to FIG. 20, the fuel supply amount is maintained for a predetermined time after the generation current is reduced and is increased prior to the increase in the generation current. And excess fuel is generated. Since this surplus fuel is used for heating in the fuel cell module 2, the detected temperature Td tends to increase from time t20 to t21.

  Further, at time t21, the detected temperature Td reaches the temperature of the current maintaining region at the generated current of about 6A (corresponding to t21 in FIG. 30 and steps S51 to S52 in FIG. 29). Thereby, step S52 of FIG. 29 is executed, and thereafter, the increase in generated current is prohibited and the generated current is maintained. For this reason, from time t21 to t22, the target current increases to about 7A, but the generated current is maintained at about 6A. By prohibiting the increase in the generated current, the upper limit value of the variable range of the generated power is reduced and the variable range is narrowed, so that the amount of residual fuel accompanying a change in the generated power is reduced. In this way, step S52 in FIG. 29, which reduces the amount of residual fuel while continuing power generation, acts as a temperature rise suppression means. Further, step S51 for determining whether or not to execute step S52 acting as a temperature rise suppression means acts as an excessive temperature rise estimation means for estimating the occurrence of an excessive temperature rise in the fuel cell module 2.

  Further, at times t21 to t22, since the detected temperature Td rises, the first addition / subtraction value M1 becomes a positive large value, and the value of the first integrated value N1id also increases significantly. As a result, the fuel supply amount is decreased so as to increase the fuel utilization rate Uf (FIG. 23). This increase in the fuel utilization rate Uf also acts as a temperature rise suppression means because it acts to reduce the amount of residual fuel and lower the temperature in the fuel cell module 2. At times t21 to t22, the fuel utilization rate Uf is increased and the amount of heat accumulated in the heat insulating material 7 and the like is actively consumed. However, since the heat capacity of the fuel cell module 2 is very large, the detected temperature Td continues to rise.

  Next, at time t22, the increased fuel utilization rate Uf reaches the maximum fuel utilization rate Ufmax (= 75%), which is the maximum fuel utilization rate at the generated current of about 6A (N1id = 1 in FIG. 23, FIG. 24). Since the fuel utilization rate Uf is increased to the maximum fuel utilization rate Ufmax at time t22, the fuel utilization rate Uf is maintained at the maximum fuel utilization rate Ufmax from time t22 to t23. On the other hand, since the detected temperature Td continues to rise from time t22 to t23, the value of the second integrated value N2id (the same value as the first integrated value N1id) also increases. Along with this, the air utilization rate Ua is reduced (N2id> 1 in FIG. 25), that is, the air supply amount is increased.

  Furthermore, at time t23, the detected temperature Td reaches the temperature of the current drop region at the generated current of about 6A (corresponding to steps S49 → S50 in FIG. 29). Accordingly, step S50 in FIG. 29 is executed, and the generated current is rapidly reduced from about 6A to 4A (t23 → t23 ′ in FIG. 30), and the upper limit value of the variable range of the generated power is further reduced. Is further narrowed. For this reason, the fuel utilization rate Uf is slightly reduced from the maximum fuel utilization rate Ufmax at the generated current of about 6A to the maximum fuel utilization rate Ufmax at the generated current 4A (FIGS. 24 and 31). At time t23, the fuel utilization rate Uf is reduced, but since the generated current is reduced to 4A, the absolute amount of fuel supply and the absolute amount of residual fuel are reduced. Since the fuel utilization rate Uf is maintained at the maximum fuel utilization rate Ufmax while the generated current is reduced, the consumption of the accumulated heat amount is further promoted. In this way, step S50 in FIG. 29, which reduces the amount of residual fuel while continuing power generation by reducing the generated current, also acts as temperature rise suppression means. However, the detected temperature Td still rises from time t23 to t24.

  Next, at time t24, the detected temperature Td reaches the temperature of the air cooling region (corresponding to steps S47 → S48 in FIG. 29, t24 in FIG. 30). Thus, step S48 of FIG. 29 is executed, and the air supply amount is increased to the maximum air supply amount of the power generation air flow rate adjustment unit 45. Further, the generated current gradually decreases from 4A to 1A. Thereafter, the generated current that has been reduced to 1 A, which is the temperature increase suppressing power generation amount, is kept constant until the detected temperature Td decreases to a temperature lower than the current maintaining region. Further, the generated current reduced to 1 A is not output to the inverter 54, and the entire amount is consumed by the auxiliary unit 4. As the generated current decreases, the fuel utilization rate Uf decreases from the maximum fuel utilization rate Ufmax at the generated current 4A to the maximum fuel utilization rate Ufmax (= 50%) at the generated current 1A (FIG. 24).

  As described above, after the temperature increase suppression for reducing the amount of residual fuel is executed in step S50 of FIG. 29, which is the temperature increase suppression means, the air supplied when the temperature increase needs to be further suppressed. Is increased. Since the increased amount of air increased beyond the supply amount necessary for power generation acts as a cooling fluid flowing into the fuel cell module 2, step S48 in FIG. 29 functions as a forced cooling means.

  On the other hand, if the detected temperature Td decreases without reaching the temperature in the air cooling region by executing step S50, which is a temperature rise suppression means for reducing the amount of residual fuel, the process proceeds to step S48, which is a forced cooling means. No cooling is performed. Therefore, whether or not the temperature rise suppression by the forced cooling means is executed is determined based on the temperature change in the fuel cell module 2 after the temperature rise suppression by the temperature rise suppression means is executed.

  After time t24, the detected temperature Td continues to increase, but starts decreasing at time t25 (t24 → t25 in FIG. 30). Thereafter, the detected temperature Td decreases, and at time t26, the detected temperature Td decreases to the upper limit temperature of the current decrease region (t25 → t26 in FIG. 30). Thereby, the reduction of the air supply amount is started.

  Next, at time t27, the temperature decreases to the upper limit temperature of the current maintaining region (t26 → t27 in FIG. 30). The detected temperature Td continues to further decrease, and at time t28, the detected temperature Td decreases to the lower limit temperature of the current maintaining region (t27 → t28 in FIG. 30).

  When the detected temperature Td goes out of the current maintaining region at time t28, the generated current starts to increase to follow the target current. Along with this, the fuel supply amount also increases. Further, the fuel utilization rate Uf increases while taking the maximum fuel utilization rate Ufmax corresponding to each generated current.

  In the above-described embodiment, the temperature rise is suppressed by lowering the upper limit value of the variable range of the generated power in accordance with the temperature in the fuel cell module 2. Temperature rise can also be suppressed by reducing the frequency. That is, when the temperature in the fuel cell module 2 rises, the rise in temperature can be suppressed by reducing the followability of increasing the generated power following the increase in demand power. When the followability to the increase in demand power is reduced, the generated power increases more slowly when the demand power increases. For this reason, when the demand power is frequently increased or decreased, the increase / decrease width of the generated power to follow this is reduced as a result, the frequency of increase / decrease is reduced, and the amount of residual fuel generated is also reduced. . Such a decrease in followability with respect to an increase in demand power continues until the excessive temperature rise in the fuel cell module 2 is resolved.

  Alternatively, it is possible to limit the frequency per hour for increasing the generated power following the increase in demand power. In this case, a limit is imposed on the number of times per predetermined time at which the generated power turns to an increasing trend, and if the number of times per predetermined time increases, the generated power will not follow the increase in demand power. To control.

  In the above-described embodiment, when the detected temperature Td reaches the temperature in the current reduction region, the upper limit value of the generated current is reduced to 4 A. However, as a modified example, the upper limit value of the generated power to be reduced is variable. You can also For example, the upper limit value of the generated power to be reduced can be set lower as the temperature in the fuel cell module 2 is higher.

Next, the relationship between the temperature in the fuel cell module 2 and the maximum power that can be generated will be described with reference to FIG.
As described above, there is a correlation between the generated power (current) of the fuel cell module 2 and the appropriate temperature in the fuel cell module 2, and in order to obtain large generated power, the temperature in the fuel cell module 2 is increased. There is a need to. However, in the temperature range in which the fuel cell module 2 is higher than the appropriate temperature for the generated power and exceeds about 700 ° C., the potential generated by each fuel cell unit 16 decreases due to the characteristics of the fuel cell stack 14. For this reason, when a large current is drawn from the fuel cell stack 14 in order to obtain a large amount of power, the temperature of the fuel cell stack 14 further rises and the generated potential decreases, so that the output power can be increased even if the current is increased. The phenomenon that does not increase occurs. Thus, as shown in FIG. 32, in the region where the temperature in the fuel cell module 2 is high, the maximum power that can be generated decreases as the temperature rises. In such a temperature range, if the maximum rated power is to be extracted from the fuel cell module 2, the current is increased to increase the extracted power, and this current rise further increases the temperature of the fuel cell module 2 and is extracted. The power will be reduced. If such a state continues, in order to obtain a predetermined rated power, a thermal runaway in which the temperature of the fuel cell module 2 rapidly rises is caused.

In the present embodiment, in a region where the temperature in the fuel cell module 2 is higher than the appropriate temperature, thermal runaway can be prevented by maintaining or reducing the generated current even when demand power is increased. Yes.
According to the solid oxide fuel cell of the second embodiment of the present invention, when the temperature of the fuel cell unit 16 reaches the forced cooling threshold temperature (FIG. 30, 750 ° C.), the temperature in the fuel cell module is set. Since the forced cooling means for lowering (FIG. 29, steps S47 → S48) is provided, an excessive temperature rise in the fuel cell module 2 can be surely avoided.

  Further, according to the solid oxide fuel cell of the present embodiment, when the temperature of the fuel cell unit 16 reaches a predetermined operation stop threshold temperature (FIG. 30, 780 ° C.), the fuel cell module is stopped (FIG. 29, Steps S45 → S46), the risk of damaging the fuel cell module 2 can be avoided more reliably.

  As mentioned above, although preferable embodiment of this invention was described, a various change can be added to embodiment mentioned above. In particular, in the above-described embodiment, the heat capacity of the heat insulating material (heat storage material) is constant, but as a modification, the fuel cell module can be configured so that the heat capacity can be changed. In this case, the additional heat capacity member having a large heat capacity is arranged so as to be thermally connected to and disconnected from the fuel cell module. When the heat capacity is to be increased, the additional heat capacity member is thermally connected to the fuel cell module, and when the heat capacity is to be decreased, the additional heat capacity member is thermally disconnected. For example, when starting up the solid oxide fuel cell, the heat capacity is reduced by separating the additional heat capacity member, and the temperature of the fuel cell module is increased quickly. On the other hand, when the solid oxide fuel cell is expected to be operated for a long time with large generated power, the additional heat capacity member is connected so that the fuel cell module can accumulate a larger amount of surplus heat.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Fuel cell module 4 Auxiliary machine unit 7 Heat insulation material (heat storage material)
8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide fuel cell)
DESCRIPTION OF SYMBOLS 18 Combustion chamber 20 Reformer 22 Air heat exchanger 24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit (steam supply means)
30 Fuel supply source 38 Fuel flow rate adjustment unit (fuel supply means)
40 Air supply source 44 Reforming air flow rate adjusting unit (reforming oxidant gas supply means)
45 Air flow adjustment unit for power generation (oxidant gas supply means for power generation)
46 1st heater 48 2nd heater 50 Hot water production apparatus 52 Control box 54 Inverter 83 Ignition apparatus 84 Fuel cell 110 Control part (control means)
110a Heat storage amount estimation means 110b Over temperature rise determination means 110c Fuel table change means 112 Operation device 114 Display device 116 Alarm device 126 Power state detection sensor (demand power detection means)
132 Fuel flow sensor (fuel supply detection sensor)
138 Pressure sensor (reformer pressure sensor)
142 Power generation chamber temperature sensor (temperature detection means)
148 Reformer temperature sensor (temperature detection means)
150 Outside temperature sensor

Claims (5)

A solid oxide fuel cell that generates electric power by reacting a fuel and an oxidant gas for power generation,
A fuel cell module having a plurality of solid oxide fuel cells stored therein ;
Disposed within the fuel cell module, a heat storage material for storing heat generated in the fuel cell module,
By simultaneously generating POX, which is a reforming reaction for partially oxidizing and reforming fuel by chemically reacting the fuel with an oxidant gas, and steam reforming for chemically reacting the partial oxidation reforming and fuel with steam. ATR which is a reforming reaction for autothermal reforming of fuel, SR1 which is a reforming reaction for generating only the steam reforming, and SR2 which is a reforming reaction for steam reforming a smaller amount of fuel than SR1 A reformer disposed in the fuel cell module that generates hydrogen by generating
Fuel supply means for supplying fuel to the reformer by feeding the fuel reformed by the reformer to the solid oxide fuel cell;
A reforming oxidant gas supply means for supplying a reforming oxidant gas to the reformer;
Steam supply means for supplying steam for reforming to the reformer;
Power generation oxidant gas supply means for supplying power generation oxidant gas to the solid oxide fuel cell;
Temperature detecting means for detecting temperatures at a plurality of locations in the fuel cell module , at least one of which reflects the temperature of the reformer ;
By controlling the fuel supply means, the reforming oxidant gas supply means, the water vapor supply means, and the power generation oxidant gas supply means, the POX in the reformer in a predetermined temperature range. While the ATR, the SR1, and the SR2 are performed in the order, a start-up step is performed to raise the temperature of the solid oxide fuel cell to a power generation start temperature at which power can be taken out from the fuel cell module. in, after the completion of the above activation step, and a control unit configured to start power generation step of taking out the electric power from the fuel cell module,
The control means performs the next reforming reaction when any of the temperatures detected by the temperature detecting means becomes equal to or higher than a predetermined transition condition temperature set for each reforming reaction. Configured to produce ,
further,
And have you during the activation step, of the temperature of the plurality of positions, does not reach the temperature of the portion of the temperature transition condition, the temperature value reflecting the temperature of the reformer is higher than the temperature of the transition condition An excessive temperature rise determination means for determining that there is an excessive temperature rise when the set forced transition temperature is reached ;
By over time integrating the subtraction value which is determined based on the deviation between the detected temperature and a predetermined reference temperature detected by said temperature detecting means, the integrated reflecting the heat storage amount stored in the heat storage material A heat storage amount estimating means for calculating a value, estimating the surplus heat storage amount accumulated in the heat storage material based on the integrated value, and starting integration of the addition / subtraction value from the SR2 .
In the SR2 during the start-up process, the control means maintains the fuel supply amount constant, and the SR2 exceeds the predetermined power generation transition time even when the solid oxide fuel cell reaches the power generation start temperature. Is configured not to start the power generation process until
Further, the control means estimates that the heat storage material estimation means stores an excessive amount of heat that can be used in the heat storage material, and determines that the excessive temperature rise determination means is an excessive temperature increase. In this case, the power generation process is started by high-efficiency operation in which the fuel supply amount is reduced and the fuel utilization rate is increased as compared with the case where the temperature rise is not excessive after the SR2 is executed for the predetermined power generation transition time or longer. Solid oxide fuel cell.   The fuel cell module is configured to generate variable generated power in a predetermined power range according to demand power, and the fuel supply amount in the SR2 is a fuel supply amount corresponding to the generated power in the intermediate band of the power range When the temperature of the fuel cell module rises excessively during the start-up process, the control means starts the power generation process with the generated power below the intermediate band regardless of the power demand. The solid oxide fuel cell according to claim 1. The cumulative value for estimating the heat storage amount stored in the heat storage material, upon reaching to a Jo Tokoro of the maximum value is not performed in an increase in the integrated value, when it reaches the minimum value of Jo Tokoro is are integrated so as not to decrease the integrated value, at the time of integration start of addition and subtraction value in the SR2, it is predetermined such integration from an intermediate value of the maximum value and the minimum value is started 2. The solid oxide fuel cell according to claim 1, wherein a predetermined integrated value is used as an initial value, and addition / subtraction is started from the initial value . When the temperature of the reformer exceeds a predetermined SR2 transition reformer temperature and the temperature of the solid oxide fuel cell exceeds a predetermined SR2 transition cell temperature, the control means performs the SR1 to SR2 When the reformer temperature exceeds a predetermined SR2 forced transition temperature set higher than the SR2 transition reformer temperature , the solid oxide fuel cell is configured. The solid oxide fuel cell according to claim 1, wherein the cell temperature is shifted to SR2 before the cell temperature reaches the SR2 transition cell temperature.   2. The solid oxide fuel cell according to claim 1, wherein the control means causes the fuel cell module to generate predetermined weak power while the SR <b> 2 is generated during the start-up process.

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