JP2012221791A - Olid oxide fuel cell device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell device capable of continuing operation with high power generation efficiency while maintaining excellent power generation capacity by preventing the degradation in power generation performance during operation.SOLUTION: A control means provided in a solid oxide fuel cell device starts power generation operation after a start mode operation before power generation is executed, and detects the lapsed time tr from the power generation start time then. When the lapsed time tr is compared with a predetermined value t1, and tr is larger than t1, the control means assumes that a fuel battery cell is in an oxide excessive state, and in that case, during executing the start mode operation, refresh control is executed by supplying fuel gas to a fuel electrode layer so that the fuel battery cell has a prescribed reduction promoting condition.

Description

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

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

  Specifically, the SOFC generally includes a plurality of tubular fuel cells each having a solid electrolyte layer sandwiched between a fuel electrode layer that is an inner electrode layer and an air electrode layer that is an outer electrode layer. The fuel cell and the oxidant gas (air, oxygen, etc.) are operated by flowing from one end side to the other end side of the fuel cell. From the outside of the SOFC, a gas to be reformed (city gas, etc.), which is a raw material gas, is supplied, and the gas to be reformed is introduced into a reformer containing a reforming catalyst, and reformed into a hydrogen-rich fuel gas. After being refined, it is configured to be supplied to the fuel cell assembly.

  In addition, the SOFC includes a plurality of processes for reforming the fuel gas in the reformer in the start-up process, that is, a partial oxidation reforming (POX) reaction process, an auto thermal reforming (ATR). The reaction process and the steam reforming (SR) reaction process are followed to shift to the power generation process. 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.

  Here, in the fuel cell device, in general, the power generation performance tends to decrease due to the oxidation of the electrode by the air remaining around the fuel cell. With regard to such an event, for example, Patent Document 1 discloses that when the reducing gas (hydrogen gas) supplied to the fuel electrode layer of the fuel cell is small, the oxidant gas is supplied from the outside of the fuel cell to the fuel electrode. It is described that oxygen ions diffuse into the fuel electrode layer unless oxygen ions that penetrate the layer and pass through the solid electrolyte layer are combined with the fuel gas. According to Patent Document 1, the oxygen gas and oxygen ions in the air that have entered the fuel electrode layer in this manner oxidize the fuel electrode layer containing metal, and as a result, the oxide formed in the fuel electrode layer. It has been pointed out that since the electrode reaction is suppressed by this, the power generation performance of the fuel cell deteriorates.

JP 2007-31288 A

  By the way, at the time of SOFC power generation, a reducing gas such as hydrogen gas that is a fuel gas is supplied to the fuel electrode layer, so that the reducing gas diffuses into the fuel electrode layer, so Even if the fuel electrode layer is oxidized by the mechanism described in (1), it is estimated that if the normal power generation operation is continued, the fuel electrode layer is continuously reduced and the decrease in power generation performance is suppressed. However, when the present inventors have examined and evaluated the operation characteristics of SOFC in detail, even if the operation of SOFC is continued properly, the power generation performance gradually and inevitably decreases gradually. It was confirmed that.

  On the other hand, in order to suppress the formation of such oxides in the fuel electrode layer of the SOFC, an amount of fuel gas that is a condition that the fuel electrode layer is always strongly reduced during the operation of the SOFC is constantly increased. It is considered effective to supply to However, in that case, the power generation efficiency of the SOFC is lowered, and there is a problem from the viewpoint of economy.

  Therefore, the present invention has been made in view of such circumstances and knowledge, and can effectively prevent a decrease in power generation performance during operation, thereby enabling operation with high power generation efficiency while maintaining excellent power generation capacity. It is an object of the present invention to provide a solid oxide fuel cell device capable of continuing the above.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, during the operation of the SOFC, it is only the very surface on the fuel gas flow path side that is reduced in the oxidized fuel electrode layer. In the vicinity of the interface between the solid electrolyte layer and the fuel electrode layer through which oxygen ions pass, the fuel electrode layer is easily reduced without being reduced, and therefore the power generation performance gradually decreases. Also, in the case of SOFC in which fuel gas is supplied from one end side to the other end side of the fuel cell, the solid electrolyte layer and the fuel electrode are disposed on the downstream side (the other end side) where the concentration of the fuel gas is relatively low. The inventors have found that the degree of oxidation of the fuel electrode layer in the vicinity of the interface with the layer is remarkable, and have completed the present invention.

  In other words, a solid oxide fuel cell (SOFC) device according to the present invention generates power using a fuel gas and an oxidant gas, and reforms a raw material gas containing hydrocarbons to produce a fuel gas containing hydrogen gas. A fuel electrode layer supplied with fuel gas, an air electrode layer supplied with oxidant gas, and a solid electrolyte layer provided between the fuel electrode layer and the air electrode layer. And fuel cell in which fuel gas flows from one end side to the other end side, fuel gas supply means for supplying fuel gas to the fuel electrode layer, and oxidant gas supply for supplying oxidant gas to the air electrode layer Means, a control means for monitoring and controlling the operating state of the SOFC device, and an oxidation estimation means for estimating whether or not the fuel cell is in an excessive oxide state. The control means comprises an oxidation estimation means. Causes the fuel cell to become over-oxidized If it is presumed that, and executes a refresh control for supplying fuel gas to the fuel electrode layer so as to have a predetermined reduction accelerated conditions.

  Here, “excess oxide state” means that the other end side (near side) of both ends of the fuel cell extending in a predetermined direction passes through the solid electrolyte layer from the air electrode layer side during power generation. The oxide of the fuel electrode layer in the vicinity of the interface between the solid electrolyte layer and the fuel electrode layer, which is generated by an oxidation reaction between oxygen ions that have reached the fuel electrode layer and the metal contained in the fuel electrode layer, It means a state where a predetermined amount is reached. In addition, the “predetermined reduction promotion condition” means that the oxide in the fuel electrode layer is more easily reduced than when the fuel battery cell is not in an excessive oxide state (in a non-excess excessive state) ( Reaction) conditions.

  In the SOFC device configured as described above, the state of the fuel cell is monitored by the oxidation estimation unit and the control unit while the power generation efficiency is normally high, and the fuel cell is in an excessive oxide state. If it is estimated that there is a hydrogen gas-rich (rich in reducing property) fuel gas (fuel electrode layer) obtained by reforming the raw material gas so that the oxide is in a reduction promoting condition that is relatively easy to reduce. By supplying a predetermined amount of the fuel electrode in the sense for the purpose of reducing the oxide of the fuel to the fuel electrode layer, the fuel electrode layer and thus the fuel cell is refreshed (initial state or a state close thereto) Recovery).

  Therefore, until the fuel cell is in an excessive oxide state, the power generation efficiency of the SOFC device can be increased while suppressing the supply of fuel gas that does not contribute to power generation as much as possible, while the fuel cell is in an excessive oxide state. In this case, by performing the refresh control, the oxide in the fuel electrode layer of the fuel cell can be sufficiently reduced, and the power generation performance can be recovered to a high initial state of operation.

  Further, the control means may lower the fuel gas utilization rate when the refresh control is being executed than the fuel gas utilization rate when the refresh control is not being executed. The “fuel gas utilization rate” indicates the proportion of fuel gas that contributes to power generation in the fuel gas supplied to the fuel cells.

  In this way, reducing hydrogen contained in the fuel gas on the other end side (closer) of the fuel cell than in the case where the utilization rate of the fuel gas is not changed from the time of normal power generation when the refresh control is executed. Since the gas concentration is increased, the oxide produced at and near the interface between the fuel electrode layer and the solid electrolyte layer is more effectively reduced, thereby reliably and quickly restoring the power generation performance of the fuel cell. It becomes possible.

  Furthermore, a combustion unit that burns the fuel gas that has passed through the fuel cell and heats the fuel cell by the combustion heat is provided, and the refresh control is not executed when the control means is executing the refresh control. It is also preferable to reduce the utilization rate of the fuel gas as compared to the time and increase the flow rate of the fuel gas passing through the fuel cells to increase the combustion heat.

  With this configuration, the flow rate of reducing hydrogen gas at the other end side (near side) of the fuel cell increases, so that the oxide generated at and near the interface of the fuel electrode layer with the solid electrolyte layer further increases. Effectively reduced. Further, although the residual fuel gas flowing out from the other end of the fuel cell without being used for power generation in the fuel cell increases, the combustion heat due to the combustion of the remaining fuel gas also increases, and the fuel cell further increases. Since the temperature is raised by heating, the reduction reaction of the oxide in the fuel electrode layer is promoted, and as a result, the power generation performance of the fuel cell can be recovered more reliably and quickly.

  At this time, the control means makes the temperature of the fuel cell when the refresh control is executed higher than a temperature predetermined according to the generated power when the refresh control is not executed. Even preferable.

  In general, in the SOFC, the power generation performance of a fuel cell tends to depend on its temperature (in other words, the temperature of the fuel cell and the extracted power have a positive correlation). By raising the temperature of the fuel cell above the temperature set according to the generated power regardless of the generated power when refresh control is not executed, the reduction reaction of the oxide in the fuel electrode layer is further promoted. As a result, the power generation performance of the fuel cell can be recovered more reliably and quickly.

  In this case, further, the control means sets the temperature of the fuel cell when the refresh control is being executed to be higher than the temperature predetermined according to the upper limit of the generated power when the refresh control is not being executed. Such control is also preferable.

  If the temperature of the fuel cell at the time of performing the refresh control is controlled in this way, the reduction reaction of the oxide in the fuel electrode layer is more reliably promoted than in the normal power generation operation. Performance can be recovered even more reliably and quickly.

  Furthermore, it is also preferable that the control means suppresses power generation in the fuel battery cell when the refresh control is executed as compared with a case where the fuel battery cell is not in an excessive oxide state.

  By suppressing power generation in this manner, the amount of oxygen ions newly supplied to the fuel electrode layer of the fuel cell is reduced, so that the fuel can be reduced during the refresh control for reducing the fuel electrode layer. Formation of new oxides in the extreme layer is effectively suppressed. As a result, there is an advantage that the power generation performance of the fuel cell can be recovered particularly quickly.

  Furthermore, the control means is configured to execute a start-up mode operation in which the fuel cell is heated to a temperature capable of generating power, and the fuel cell is estimated to be in an excessive oxide state by the oxidation estimation means. It is useful that the refresh control described above is executed during the first start-up mode operation.

  With such a control means, after it is estimated that the fuel cell is in an excessive oxide state, the refresh control is executed at the next start mode operation without performing the refresh control immediately. Up to this point, it is possible to continue power generation with low power generation efficiency, thereby avoiding an unexpected power generation stop and reducing inconvenience in practical use (operation) of the SOFC device. In addition, prior to power generation, the power generation performance (capability) of the fuel cell can be recovered during the start-up mode operation, so that efficient power generation can be realized.

  Alternatively, the supply amount of the fuel gas supplied to the fuel electrode layer in the start-up mode operation in which the refresh control is executed is greater than the supply amount of the fuel gas supplied to the fuel electrode layer in the start-up mode operation in which the refresh control is not executed. You may perform control which enlarges.

  By doing so, in normal start-up mode operation in which refresh control is not performed, refresh control is performed while supplying a sufficient amount of fuel gas necessary for heating the fuel cells to suppress an increase in the amount of fuel gas used. In the start-up mode operation, the reducing power of the fuel electrode layer oxide can be increased by increasing the supply amount of the fuel gas to the fuel cell, thereby improving the economy and reducing the fuel electrode layer oxide. The power generation performance is easily recovered by reliably reducing the power generation performance.

  At this time, in the start-up mode operation, the partial oxidation reforming reaction (POX) process, the autothermal reforming reaction (ATR) process, and the steam reforming reaction (SR) process are executed and the refresh control is executed. The control means is configured to make the execution time of the steam reforming reaction (SR) process in the mode operation longer than the execution time of the steam reforming reaction (SR) process in the normal start-up mode operation without executing the refresh control. Is also suitable. Details of each process will be described later.

  In this case, as is apparent from the stoichiometry from each reaction formula described later, the yield of hydrogen gas obtained with respect to the supply amount of the raw material gas to the reformer is the highest among the above three steps. By performing a high steam reforming reaction (SR) process for a relatively long time in the start-up mode operation in which refresh control is performed, the amount of hydrogen gas supplied to the fuel electrode layer of the fuel cell can be further increased, and the efficiency The power generation performance can be effectively recovered by reducing the oxide of the fuel electrode layer well and reliably.

  More specifically, the oxidation estimating means determines that the fuel cell has excessive oxide when the accumulated power generation time after the start of operation or the accumulated power generation time after the executed refresh control reaches a predetermined value set in advance. It is useful to presume that it is a state.

  According to the knowledge of the present inventors, in SOFC, as the cumulative power generation time (cumulative value of power generation time) increases, the cumulative supply amount of oxygen ions (cumulative value of supply amount) to the fuel electrode layer of the fuel cell. It is presumed that a large amount of oxide is generated due to the increase in size. Therefore, when the cumulative power generation time after the start of operation or the cumulative power generation time after the executed refresh control reaches the predetermined value set in advance by the oxidation estimating means, the fuel cell is in an excessive oxide state. Therefore, the estimation accuracy (accuracy) can be sufficiently and extremely easily increased, and the power generation performance of the fuel cell can be recovered in a timely and more effective manner.

  At this time, it is also preferable to configure the oxidation estimating means so as to change a predetermined value used for the estimation in accordance with the cumulative number of executions of the refresh control after the start of operation (accumulated value of the number of executions). Specifically, for example, when the number of executions of the refresh control is relatively large, the excessive oxide state of the fuel cell is estimated and the refresh control is performed compared to the case where the number of executions of the refresh control is relatively small. An example is given in which the predetermined value of the accumulated power generation time for determining the transition is reduced.

  According to the further knowledge of the present inventors, when the fuel cell is used for a long time and the accumulated power generation time becomes long, the interface between the fuel electrode layer and the solid electrolyte layer and the vicinity thereof are not reduced by the execution of the refresh control. There is a tendency for the oxide remaining in the substrate to increase. Accordingly, by making the predetermined value of the accumulated power generation time for estimating the transition to the refresh control by estimating the excessive oxide state of the fuel battery cell according to the accumulated number of executions of the refresh control after the start of operation, In response to the increase in the remaining oxide, it becomes possible to more accurately estimate whether or not the fuel cell is in an excessive oxide state, and the power generation performance of the fuel cell is more appropriately and effectively Can be recovered.

  Further, the oxidation estimating means indicates that the fuel cell is in an excessive oxide state when the total power generation amount after the start of operation or the total power generation amount after the refresh control executed last time reaches a predetermined value set in advance. It is preferable even if it is estimated.

  In the SOFC, as the total power generation amount increases, the cumulative supply amount of oxygen ions to the fuel electrode layer of the fuel cell also increases. In this case as well, a large amount of oxide is generated in the fuel electrode layer. Presumed to be. Therefore, when the total power generation after the start of operation or the total power generation after the refresh control executed last time reaches a predetermined value set in advance by the oxidation estimating means, the fuel cell is in an excessive oxide state. Even if it is estimated, the estimation accuracy (accuracy) can be increased sufficiently and very easily, and the power generation performance of the fuel cell can be recovered in a timely and more effective manner.

  In addition, the oxidation estimating means, when the output voltage when taking out the electric power from the fuel cell at the time of power generation is smaller than the reference value preset according to the value of the taken out electric power, in other words, the fuel When the decrease (drop) in the output voltage from the battery cell becomes larger than a predetermined amount, it may be estimated that the fuel battery cell is in an excessive oxide state.

  When power is extracted from the fuel cell, the output voltage of the cell decreases (decreases) according to the extracted power value. According to the further knowledge of the present inventors, the oxide generated in the fuel electrode layer Is relatively small, the voltage drop at that time is smaller than that of a relatively large amount of oxide generated in the fuel electrode layer, and the output voltage tends to stay in a relatively high range. Therefore, when the output voltage from the fuel cell is smaller than a reference value set in advance according to the power value at that time, if it is estimated that the fuel cell is in an excessive oxide state, its estimation accuracy (accuracy) ) Can be further improved, and the power generation performance of the fuel cell can be recovered in a timely and more effective manner.

  According to the present invention, when the fuel cell of the SOFC device is estimated to be in an excessive oxide state by the oxidation estimation means for estimating whether the fuel cell is in an excessive oxide state, The control means for monitoring and controlling the fuel cell performs refresh control for supplying the fuel gas to the fuel electrode layer of the fuel cell so as to satisfy a predetermined reduction promotion condition, whereby the interface between the fuel electrode layer and the solid electrolyte layer Since the oxide existing in the vicinity thereof is sufficiently reduced, it is possible to effectively prevent a decrease in power generation performance during operation of the SOFC device, thereby maintaining high power generation efficiency and high power generation efficiency. It becomes possible to continue the power generation operation of the SOFC device.

It is a whole lineblock diagram showing the SOFC device by one embodiment of the present invention. 1 is a perspective view showing a fuel cell module in a state where a housing of an SOFC device according to an embodiment of the present invention is removed. FIG. 3 is a cross-sectional view of the fuel cell module of the SOFC device according to the embodiment of the present invention when viewed from the direction A in FIG. 2. FIG. 3 is a cross-sectional view of the fuel cell module of the SOFC device according to the embodiment of the present invention as viewed from the direction B of FIG. It is a front view which shows the fuel cell unit of the SOFC apparatus by one Embodiment of this invention. FIG. 3 is a perspective view of the fuel cell module showing a state where a casing covering the fuel cell assembly is removed from the fuel cell module shown in FIG. 2. It is a perspective view which shows the evaporative mixer in the fuel cell module shown in FIG. It is the schematic plan view which looked at the heat exchanger of the fuel cell module of the SOFC apparatus by one Embodiment of this invention from upper direction. It is a block diagram which shows the structure of the SOFC apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of starting of the SOFC apparatus by one Embodiment of this invention. It is a flowchart which shows an example of the process sequence which performs refresh control in the SOFC apparatus by one Embodiment of this invention. (A) And (B) is a time chart which shows the operation | movement at the time of starting of the SOFC apparatus by one Embodiment of this invention, (A) is operation | movement in starting mode driving | operation, (B) is in refresh control. It is a figure which shows operation | movement typically. It is a graph which shows an example of the relationship between the output electric current by the presence or absence of refresh control, and fuel gas flow volume in the SOFC apparatus by one Embodiment of this invention. It is a graph which shows an example of the relationship between the output current by the presence or absence of refresh control, and stack temperature in the SOFC apparatus by one Embodiment of this invention. It is a graph which shows another example of the relationship between the output current by the presence or absence of refresh control, and fuel gas flow volume in the SOFC apparatus by one Embodiment of this invention. (A) And (B) is a time chart which shows the other example of the process sequence which performs refresh control in the SOFC apparatus by one Embodiment of this invention. It is an example of the microscope picture which expands and shows the cross section of the site | part containing the interface of the inner side electrode layer (fuel electrode layer) of a fuel cell, and a solid electrolyte layer.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in the drawings are denoted by the same reference numerals as much as possible, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention only to the embodiments. The present invention can be variously modified without departing from the gist thereof. Is possible.

  FIG. 1 is an overall configuration diagram showing a preferred embodiment of a solid oxide fuel cell (SOFC) apparatus according to the present invention. The SOFC device 1 includes a fuel cell module 2 and an auxiliary machine unit 4 (auxiliary machine). The fuel cell module 2 includes a housing 6. Inside the housing 6, a sealed space 8 is formed surrounded by a heat insulating material (not shown). A fuel cell assembly 12 that performs a power generation reaction with fuel gas and air that is an oxidant gas is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8.

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

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

  Above the combustion chamber 18 is disposed a reformer 20 for reforming the raw material gas to generate a fuel gas, and the reformer 20 can be reformed by the combustion heat of the combustion gas described above. Heat to a suitable temperature. Further, a heat exchanger 22 for heating an oxidant gas (air) introduced from the outside by the heat of the combustion gas is disposed above the reformer 20.

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

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

  The fuel cell module 2 is connected with a hot water production apparatus 50 to which exhaust gas is supplied. The hot water production apparatus 50 is supplied with tap water from a water supply source 24, and the tap water is exhaust gas. The water becomes warm water due to the heat of the water and is supplied to a hot water storage tank of an external water heater (not shown), for example. Further, 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 includes an inverter 54 that is a power extraction unit (power conversion unit) for taking out the electric power generated by the fuel cell module 2 and supplying the electric power to the outside, and the generated electric power as an auxiliary device. A switching device 55 for switching to send to the unit 4 or the inverter 54 is connected. The switch 55 also has a function of a DC-DC converter for converting the generated power into the drive voltage (DC) of each device of the auxiliary unit 4.

  Subsequently, the internal structure of the fuel cell module 2 of the SOFC device 1 will be described with reference to FIGS. 2 to 4, 6, and 7. FIG. 2 is a perspective view showing the fuel cell module 2 with the housing 6 of the SOFC device 1 removed. In FIG. 2, in each fuel cell stack 14 constituting the fuel cell module 2, the direction in which eight fuel cell units 16 are arranged is the x-axis direction. The direction in which the fuel cell unit 16 is erected and extends is the y-axis direction, and the direction orthogonal to the x-axis and the y-axis is the z-axis direction. The x-axis, y-axis, and z-axis described in FIG. 3 and subsequent figures are based on the x-axis, y-axis, and z-axis in FIG.

  3 is a cross-sectional view of the fuel cell module 2 of the SOFC device 1 as viewed from the direction A of FIG. 2, and FIG. 4 is a cross-sectional view of the fuel cell module 2 of the SOFC device 1 as viewed from the direction B of FIG. is there. 6 is a perspective view showing the fuel cell module 2 with the casing covering the fuel cell assembly 12 removed from the fuel cell module 2 shown in FIG. 2, and FIG. 7 shows the fuel shown in FIG. 4 is a perspective view showing an evaporating mixer 58 in the battery module 2. FIG.

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

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

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

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

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

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

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

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

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

  Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 5 is a front view (partial sectional view) showing the fuel cell unit 16 of the SOFC device 1. As shown in the figure, 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 that extends in the vertical direction, and has a cylindrical inner electrode layer 90 (fuel electrode layer) that defines a fuel gas flow path 88 inside (inside), and a cylindrical outer electrode layer. 92 (air electrode layer) and an oxide electrolyte type electrolyte layer 94 provided between the inner electrode layer 90 and the outer electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and functions as a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and functions as a (+) electrode.

  Since the inner electrode terminal 86 attached to the upper end side and the lower end side of the fuel cell unit 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. It is formed of at least one of a mixture and a mixture of Ni and lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 94 includes, 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, and lanthanum doped with at least one selected from S and Mg. It is formed from at least one kind of gallate.

  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 lanthanum cobaltite doped with at least one selected from Cu, silver, and the like.

Here, FIG. 17 is an example of a micrograph showing an enlarged cross section of a portion including the interface between the inner electrode layer 90 (fuel electrode layer) and the electrolyte layer 94 of the fuel cell 84. In the figure, the inner electrode layer 90 is a support (Ni / YSZ) in which a mixture of Ni and Gd-doped ceria (Ni / GDC) is a mixture of Ni and yttria-stabilized zirconia (Ni / YSZ). It is formed on the lower region part). As shown in FIG. 17, the inner electrode layer 90 and the electrolyte layer 94 (for example, lanthanum gallate, La _1-x Sr _x Ga _{1 -y} Mg _y O ₃ : LSGM) are continuously laminated. Each have a plurality of voids at different densities. Therefore, although it is difficult to strictly define the boundary between the inner electrode layer 90 and the electrolyte layer 94 as an “interface”, the range indicated by the region B in FIG. 17 is “the solid electrolyte layer and the fuel electrode layer” in this specification. The interface and the vicinity of the interface.

  Further, according to the analysis and evaluation by the present inventors, as the operation of the SOFC device 1 proceeds, the Ni contained in the inner electrode layer 90 in the region B which is the interface between the electrolyte layer 94 and the inner electrode layer 90 and in the vicinity of the interface. It was confirmed that Ni oxide was generated by oxidizing (distributed in a granular form), and the Ni oxide remained as it was without being reduced to Ni even if the conventional normal operation was continued.

  Next, the control unit, device, sensor, and timer attached to the SOFC device 1 will be described with reference to FIG. FIG. 9 is a block diagram showing the configuration of the SOFC apparatus 1. As shown in the figure, the SOFC device 1 includes a control unit 110 (control means) for monitoring and controlling the operating state of the SOFC device 1. The control unit 110 includes an operation device 112 having operation buttons such as “ON” and “OFF” for operation by the user, and a display for displaying various data such as a power generation output value (wattage). A device 114 and a notification device 116 that issues a warning (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

  Signals from various sensors described below are input to the control unit 110. The combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4. The CO detection sensor 122 determines whether or not CO in the exhaust gas originally discharged to the outside through the combustion gas discharge chamber 80 or the like has leaked to an external housing (not shown) that covers the fuel cell module 2 and the accessory unit 4. It is for detecting. 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), and is configured to detect an open circuit voltage. 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 rate sensor 130 is for detecting the flow rate of reforming air supplied to the reformer 20, and the fuel flow rate sensor 132 is the flow rate of fuel gas supplied to the reformer 20. It is for detecting.

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

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

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

  The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20. As shown in FIGS. 3 and 4, the reformer temperature sensor 148 is provided in the vicinity of each of the inlet side and the outlet side of the reformer 20. The outside air temperature sensor 150 is for detecting the temperature of the outside air when the SOFC device 1 is installed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

  Furthermore, the timer 160 is an appropriate time measuring unit that measures the accumulated power generation time after the start of operation of the SOFC device 1 and the accumulated power generation time after refresh control described later.

  Signals from these sensors and timer 160 are sent to the control unit 110. The control unit 110 sends a control signal to each of the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, and the power generation air flow rate adjustment unit 45 based on the data based on these signals. Each flow rate in these units is controlled. The control unit 110 also sends a control signal to the inverter 54 to control the amount of power supply.

  Further, an operation at the time of startup in the SOFC device 1 will be described with reference to FIG. FIG. 10 is a time chart showing the operation at the time of startup of the SOFC device 1.

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

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

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

At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction (POX) represented by This equation exemplifies the reforming reaction of methane gas (CH ₄ ) mainly contained in the raw material gas, and the reforming reaction may include oxidation of other hydrocarbon gas (the following formula ( The same applies to 2) and formula (3)).
CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (1)

  Since this partial oxidation reforming reaction (POX) is an exothermic reaction, the startability is good. The fuel gas heated by the exothermic reaction is supplied to the lower part of the fuel cell stack 14 through the fuel supply pipe 64. Thereby, the fuel cell stack 14 is heated from below. Since the combustion chamber 18 is also heated by burning the fuel gas and air, the fuel cell stack 14 is also heated from above. As a result, the fuel cell stack 14 is configured to be able to raise the temperature substantially evenly in the vertical direction. Even if the partial oxidation reforming reaction (POX) proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

After the start of the partial oxidation reforming reaction (POX), based on the temperature of the reformer 20 detected by the reformer temperature sensor 148 and the temperature of the fuel cell stack 14 detected by the power generation chamber temperature sensor 142, By the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, and the reforming air flow rate adjustment unit 44, supply of the gas in which the fuel gas, the reforming air, and the water vapor are mixed in advance to the reformer 20 is started. . At this time, in the reformer 20, the autothermal reforming reaction (ATR) represented by the formula (2) in which the partial oxidation reforming reaction (POX) described above and the steam reforming reaction (SR) described later are used together. ) Goes on.
CH ₄ +1/4 O ₂ + 1 / 2H ₂ O → CO + 5 / 2H ₂ (2)

  Since this autothermal reforming reaction (ATR) can be internally balanced (an equilibrium state is generated), the reaction proceeds in a thermally independent state in the reformer 20. That is, when there is a lot of oxygen (air), heat generation by the partial oxidation reforming reaction (POX) is dominant, and when there is a lot of 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. In addition, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction (ATR) is in progress.

  After the start of the autothermal reforming reaction (ATR), based on the temperature of the reformer 20 detected by the reformer temperature sensor 148 and the temperature of the fuel cell stack 14 detected by the power generation chamber temperature sensor 142, The supply of reforming air by the reforming air flow rate 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 steam, and the steam reforming reaction (SR) represented by the equation (3) proceeds in the reformer 20. .
CH ₄ + H ₂ O → CO + 3H ₂ (3)

  Since this 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 inside of the power generation chamber 10 has been heated to a sufficiently high temperature. There is no invitation. Even if the steam reforming reaction (SR) proceeds, the combustion reaction continues in the combustion chamber 18.

  In this manner, 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) By proceeding sequentially, the temperature in the power generation chamber 10 gradually increases (start-up mode operation, start-up process). As shown in FIG. 10, in the startup process, the temperature rise in the power generation chamber 10 and the open circuit voltage OCV of the fuel cell stack 14 are in a correlation. After the above startup process is completed, the electric power generated by the fuel cell module 2 is taken out to the inverter 54 and the auxiliary machine unit 4 via the switch 55 (that is, power generation is started). Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises. In addition, the time measurement process by the timer 160 is started when the start-up process is completed, or when the power is taken out from the fuel cell module 2 and power generation is started.

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

  Further, in the start-up process (start-up mode operation) shown in FIG. 10, a partial oxidation reforming reaction (POX) process, an autothermal reforming reaction (ATR) process, and a steam reforming reaction (SR) process are each performed in a single manner. However, it is also suitable as a process in which each of them is subdivided. An example will be described in which the POX process is subdivided into a POX1 process and a POX2 process, the ATR process is subdivided into an ATR1 process and an ATR2 process, and the SR process is subdivided into an SR1 process and an SR2 process.

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

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

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

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

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

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

  At this time, the cell stack temperature is measured by a power generation chamber temperature sensor 142 disposed in the power generation chamber 10. Although the temperature in the power generation chamber 10 and the cell stack temperature are not strictly the same, the temperature detected by the power generation chamber temperature sensor 142 reflects the cell stack temperature, and the power generation disposed in the power generation chamber 10 The room temperature sensor 142 can grasp the cell stack temperature. In this specification, the “cell stack temperature” means a temperature measured by an arbitrary sensor that indicates a value reflecting the cell stack temperature.

  Further, when the reformer temperature is 600 ° C. or higher and the cell stack temperature is 400 ° C. or higher (ATR2 transition condition), the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 to decrease the fuel gas supply amount. . Further, the control unit 110 sends a signal to the reforming air flow rate adjustment unit 44 to reduce the reforming air supply amount and sends a signal to the water flow rate adjustment unit 28 to increase the water supply amount (ATR2). Process start). Accordingly, the fuel gas supply amount is changed to 4.0 (L / min), the reforming air supply amount is changed to 4.0 (L / min), and the water supply amount is set to 3.0 (cc / min). ). As the reforming air supply amount is reduced and the water supply amount is increased in this way, the proportion of the partial oxidation reforming reaction (POX) that is an exothermic reaction is reduced in the reformer 20. The ratio of the steam reforming reaction (SR), which is an endothermic reaction, increases. As a result, an increase 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 follows the reformer temperature. Since the temperature is increased, the temperature difference between the two is reduced, and both are stably heated.

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

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

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

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

  When the reformer temperature is 650 ° C. or higher and the stack temperature is 700 ° C. or higher after the predetermined power generation transition period has elapsed (power generation process transition condition), the fuel cell module 2 passes through the switch 55. Electric power is output to the inverter 54 and the auxiliary unit 4, and the power generation process is started to start power generation (power generation process start). Also in this case, the time measurement process by the timer 160 is started when the start-up process is completed or when power is taken out from the fuel cell module 2 and power generation is started.

  When the operation of the SOFC device 1 that has started power generation in this way is continued, oxygen gas or oxygen ions derived from air flow into and diffuse into the inner electrode layer 90 that is the fuel electrode layer in the fuel cell 84, and then diffuse into the inner electrode layer 90. Oxides of metals such as Ni contained therein generate oxides. In particular, the oxide generated at the interface between the electrolyte layer 94 and the inner electrode layer 90 and in the vicinity thereof (region B shown in FIG. 5) is difficult to be reduced by the fuel gas inserted during normal power generation operation. Oxidation of the electrode layer 90 proceeds gradually. At this time, the degree of oxidation of the inner electrode layer 90 in the vicinity of the interface between the electrolyte layer 94 and the inner electrode layer 90 is significant on the downstream side (the other end side) of the fuel gas passage 88 where the concentration of hydrogen gas is relatively low. It becomes. Therefore, when the SOFC device 1 is in operation, refresh control for performing a reduction process on the inner electrode layer 90 including the oxidized portion is executed.

  Here, FIG. 11 is a flowchart showing an example of a processing procedure for performing such refresh control in the SOFC apparatus 1. First, power generation is started through the first start-up process (start-up mode operation) before power generation as described above, and as described above, time measurement by the timer 160 is started based on the control signal from the control unit 110. Based on the measurement signal of the timer 160, an elapsed time tr from the start of power generation is detected (step S1). More specifically, for example, when the power state detection sensor 126 (see FIG. 9) detects the current and voltage of the inverter 54, the control unit 110 turns on the timer 160 based on the detection signal, and The time may be counted, or among the continuous timing signals sent from the timer 160, those sent when the power state detection sensor 126 detects the current and voltage of the inverter 54 are counted. The time may be measured based on the count value. That is, the elapsed time tr corresponds to the accumulated power generation time after starting the operation of the SOFC device 1 (the time during which power is taken out from the fuel cell 84).

  On the other hand, prior to the operation of the SOFC device 1, for example, when the SOFC device 1 is operated under various power generation operation conditions using an SOFC testing machine configured in the same manner as the SOFC device 1, the output from the fuel cell 84. The elapsed operation time at the time when the power or the output voltage significantly decreases from an appropriate value (for example, a design specification value) in steady operation is measured. Then, based on the measured value, the fuel cell 84 is in an excessive oxide state, and accordingly, a reference time for determining that the refresh control needs to be executed is set in advance. For example, if a significant decrease in the output power or output voltage from the fuel cell 84 occurs in one year after the start of operation, a predetermined value t1 for estimating that the fuel cell 84 is in an excessive oxide state is set. One year may be set, or the predetermined value t1 may be set as half a year, taking into account the likelihood. The control unit 110 can store a plurality of predetermined values t1 thus determined (associated) with various operating conditions together with the operating conditions.

  Such a test operation may be replaced by an acceleration test or the like as necessary, or may be performed by simulation or in combination with simulation. Moreover, you may use predetermined value t1 in the driving | running condition in which the grade of the oxidation in the inner side electrode layer 90 of the fuel cell 84 becomes the largest among the driving | running conditions assumed.

  When the SOFC device 1 is in operation, the control unit 110 performs a comparison operation between the elapsed time tr measured by the timer 160 and an appropriate predetermined value t1, and when tr> t1 (step S2: YES), It is presumed that the fuel cell 84 is in an excessive oxide state, and the control shifts to refresh control of the fuel cell 84. On the other hand, when tr ≦ t1 (step S2: NO), it is estimated that the fuel cell 84 is not in the excessive oxide state (in the non-oxide excess state), and the refresh control of the fuel cell 84 is performed. Return to normal power generation operation processing without shifting. As described above, in the present embodiment, the controller 110, the timer 160, and the power state detection sensor 126 constitute an oxidation estimation unit, or the control unit 110 may function as an oxidation estimation unit.

  In addition, the comparison calculation in this step S2 is performed at a frequency of once / day during power generation of the SOFC device 1 or at night when power generation is stopped, or at a shorter interval, for example. It may be performed at an interval longer than that, and furthermore, the interval of the comparison operation may or may not be constant.

  Next, in this embodiment, instead of immediately executing the refresh control, the control unit 110 once determines whether or not the startup process shown in FIG. 10, that is, the startup mode operation is performed (step S3). The SOFC device 1 is usually operated while repeating power generation and power generation suspension (for example, a home SOFC), and a startup process is performed when power generation is resumed from a suspended state. At this time, when it is determined that the start mode operation is being performed (step S3: YES), refresh control of the fuel cell 84 is executed in the start mode operation (step S4). On the other hand, when it is determined that the start mode operation is not being performed (step S3: NO), the process returns to the normal power generation operation process without executing the refresh control. As described above, in the present embodiment, the refresh control is executed during the first start-up mode operation after the fuel cell 84 is estimated to be in the excessive oxide state.

  In this refresh control, a normal power generation operation is performed during operation of the SOFC device 1, so that the interface between the inner electrode layer 90 and the electrolyte layer 94 in the inner electrode layer 90 of the fuel cell 84 and its A predetermined amount of fuel gas is supplied to the inner electrode layer 90 so that the oxide formed in the nearby region B (see FIG. 17) can be sufficiently reduced. Note that more specific processing in the refresh control that causes such a reduction promotion condition will be described later.

  When the execution of the refresh control of the fuel cell 84 is completed, the control unit 110 resets the elapsed time tr (step S5) and returns to the normal power generation operation process. Here, the reset elapsed time tr is measured again by the timer 160 when the next start mode operation is completed and then the power generation operation is started and power generation is started (Step S1 after the power generation operation is resumed). ). Therefore, the elapsed time tr is the accumulated power generation time of the SOFC device 1 after executing the refresh control of the fuel cell 84. Thus, in step S2 after restarting the power generation operation, the previous refresh control is executed. It is estimated that the fuel cell 84 is in an excessive oxide state when the elapsed time tr, which is the accumulated power generation time later, exceeds the predetermined value t1.

  According to the SOFC device 1 according to the present invention configured as described above, the state of the fuel cell 84 is changed by the control unit 110 which is the oxidation estimation unit and the control unit while generating power in a state where the power generation efficiency is high normally. Monitor and supply a predetermined amount of fuel gas (hydrogen gas rich and highly reducible) to the inner electrode layer 90 when the fuel cell 84 is estimated to be in an excessive oxide state, thereby causing reduction promotion conditions As a result, not only the surface layer of the inner electrode layer 90 but also the oxide generated at the interface with the electrolyte layer 94 and the vicinity thereof can be sufficiently reduced by the reducing power of the hydrogen gas in the fuel gas.

  As a result, the inner electrode layer 90 and thus the fuel cell 84 can be sufficiently refreshed, so that the supply of fuel gas that does not contribute to power generation is suppressed as much as possible until the fuel cell 84 is in an excessive oxide state. The power generation efficiency can be increased, and the power generation performance of the fuel battery cell 84 can be recovered to a high initial operation state by executing the refresh control when the fuel battery cell 84 is in an excessive oxide state. Accordingly, it is possible to achieve continuous operation with high power generation efficiency while effectively preventing a decrease in power generation performance during operation and maintaining excellent power generation capacity.

  Further, the controller 110 causes the elapsed time tr (cumulative power generation time) after the start of the operation of the SOFC device 1 or the elapsed time tr in the power generation operation after the refresh control, and whether the fuel cell 84 is in an excessive oxide state. Since this estimation is performed based on a comparison result with a predetermined value t1 that is a preset reference time for estimating whether or not, it is possible to sufficiently and extremely easily increase the estimation accuracy (accuracy) Thereby, the power generation performance of the fuel cell 84 can be recovered in a timely and effective manner.

  Furthermore, since refresh control of the fuel cell 84 is executed during the first start-up mode operation after the fuel cell 84 is estimated to be in an excessive oxide state by the control unit 110, the time when such estimation is made. Thus, even during normal power generation operation, it is possible to continue power generation with low power generation efficiency until the next start-up mode operation. Therefore, since it is not necessary to stop or stop power generation for refresh control, it is possible to avoid inadvertent power generation stop and suppress inconveniences in actual use of the SOFC device 1 such as a reduction in operating rate. In addition, prior to power generation, the power generation performance of the fuel cell 84 can be effectively recovered during the start-up mode operation, so that more efficient power generation can be realized.

  Here, FIGS. 12A and 12B are time charts showing the operation at the time of startup of the SOFC device 1, and FIG. 12A shows that the fuel cell 84 is not in an excessive oxide state (non-existing state). FIG. 12B is a diagram schematically showing an operation in a normal start-up mode operation that is executed when it is estimated that the fuel cell 84 is in an excessive oxide state. FIG. It is a figure which shows typically the operation | movement in an example of the starting mode driving | operation in the refresh control performed when it estimates. 12A is basically equivalent to the operation in the time chart shown in FIG. 10, and the operation shown in FIG. 12B is controlled by the control unit 110 under the steam reforming reaction (SR). ) The operation time of the process is the same as the operation of the time chart shown in FIG. 12A except that the execution time of the process is longer than the execution time of the process in the operation shown in FIG. Specifically, for example, in the start-up mode operation shown in FIG. 12B, the implementation time of the steam reforming reaction (SR) step is extended by 30 minutes compared to the start-up mode operation shown in FIG.

  By doing so, the hydrogen gas yield by the steam reforming reaction (SR) is the highest among the three reaction steps that occur in the start-up mode operation, so the supply of hydrogen gas to the inner electrode layer 90 of the fuel cell 84 is performed. The amount can be further increased, whereby the recovery of the power generation performance of the fuel cell 84 can be realized extremely effectively.

  The control operation shown in FIGS. 12A and 12B is an example of a procedure for executing the refresh control in the start-up mode operation. Further, referring to FIGS. 13 to 15, the refresh control is performed during the power generation operation. An example of the procedure to be executed will be described.

  FIG. 13 is a graph showing an example of the relationship between the output current and the fuel gas flow rate depending on whether or not the refresh control is performed in the SOFC device 1. In the figure, a curve indicated by a broken line represents a fuel supply table (basic fuel supply table) when the fuel cell 84 is not in an excessive oxide state (in a non-oxide excess state). In normal power generation operation, fuel gas is supplied in accordance with a predetermined basic fuel supply table. On the other hand, a curve indicated by a solid line represents a fuel supply table (refresh control fuel supply table) when the fuel cell 84 is in an excessive oxide state, and the control unit 110 is predetermined in the refresh control. The fuel gas is supplied in accordance with the fuel supply table during the refresh control.

  That is, when the refresh control of the fuel cell 84 is executed, the fuel gas flow rate for obtaining the same output current is increased and the utilization rate of the fuel gas is decreased as compared with the normal power generation operation. As a result, the concentration of hydrogen gas contained in the fuel gas on the other end side (near side) of the fuel cell 84 can be significantly increased, so that the reduction of the oxide of the inner electrode layer 90 is promoted, and the fuel cell 84 The power generation performance can be recovered more reliably and more quickly.

  In addition, in the example shown in FIG. 13, if additional follow-up operation is performed along the basic fuel supply table, it is possible to output a generated current of a maximum of 7 A originally, but operation along the fuel supply table during refresh control. When performing the above, control is performed so that only a generated current of 4 A is output at the maximum. That is, when refresh control is executed, power generation is suppressed as compared with normal power generation operation. Therefore, the amount of oxygen ions newly supplied to the inner electrode layer 90 of the fuel cell 84 is reduced, and the inner electrode layer 90 is reduced. It is possible to suppress the generation of new oxides in, thereby improving the recovery speed of the power generation performance of the fuel cell 84.

  FIG. 14 is a graph showing an example of the relationship between the output current and the stack temperature depending on whether or not the refresh control is performed in the SOFC device 1. In the figure, the shaded portion surrounded by the curve indicated by the broken line represents the stack temperature range (basic temperature band) when the fuel cell 84 is not in the excessive oxide state (in the non-oxide excess state). In the normal power generation operation, the control unit 110 supplies the fuel gas so that the stack temperature is maintained within a predetermined range of the basic temperature range. On the other hand, the shaded portion surrounded by the curve indicated by the solid line represents the stack temperature range (refresh control temperature range) when the fuel cell 84 is in the excessive oxide state. When the control is executed, the fuel gas is supplied so that the stack temperature is maintained at a value within a predetermined temperature range of the refresh control.

  In this way, in the refresh control of the fuel cell 84, the temperature of the fuel cell 84 is further increased to obtain an equivalent output current as compared with the normal power generation operation, thereby oxidizing the inner electrode layer 90. The reduction reaction of the product can be further promoted, and as a result, the power generation performance of the fuel cell 84 can be recovered more reliably and quickly.

  Further, as in the example shown in FIG. 14, the temperature of the fuel cell 84 when the refresh control is executed is set to a predetermined upper limit temperature corresponding to the upper limit (7A) of the generated current in the normal power generation operation. Since the temperature is higher than (650 ° C.), the reduction reaction of the oxide in the inner electrode layer 90 can be more surely promoted than in the normal power generation operation, thereby further improving the power generation performance of the fuel cell 84. It becomes possible to recover reliably and quickly.

  Further, FIG. 15 is a graph showing another example of the relationship between the output current and the fuel gas flow rate depending on whether or not the refresh control is performed in the SOFC device 1. In the figure, a curve indicated by a broken line represents the same fuel supply table (basic fuel supply table) as in FIG. On the other hand, the two black circles indicate the output current and the flow rate of the fuel gas when the fuel cell 84 is in the excessive oxide state, and the control unit 110 keeps the power generation amount constant in the refresh control ( Output current = 0.5 A: during refresh control A), or control to stop power generation (output current = 0 A: during refresh control B).

  Among these, the power generation amount in the fuel cell 84 is made constant under the condition of the refresh control time A, so that the quantitative fluctuation of oxygen ions newly supplied to the inner electrode layer 90 of the fuel cell 84 is suppressed. In addition, since the power generation in the fuel cell 84 is stopped under the condition B during the refresh control, oxygen ions newly supplied to the inner electrode layer 90 of the fuel cell 84 can be significantly reduced. it can. Therefore, by performing such control, the power generation performance of the fuel cell 84 can be recovered more stably.

  At this time, the output current (0.5 A) at the time of refresh control A can also be supplied to the component equipment of the auxiliary unit 4 (see FIGS. 1 and 9) by operating the switch 55. In this case, It is desirable to stabilize the supply current to the auxiliary machine unit 4. Then, as the reduction (reaction) in the inner electrode layer 90 of the fuel cell 84 progresses, the power supply to the auxiliary unit 4 fluctuates, and the components of the auxiliary unit 4 are defective. It is possible to suppress the occurrence. Further, even during the refresh control A, it is not necessary to supply the output current at that time to the auxiliary unit 4, so that the constituent devices of the auxiliary unit 4 can be reliably protected and the occurrence of the malfunction can be prevented. Further, it can be prevented.

  This advantageous effect is also obtained when the control at the refresh control time B for stopping even the power supply to the auxiliary unit 4 is performed. In the control at the refresh control time B, the reaction in the fuel cell 84 is performed. The fuel gas more than the amount necessary for the heat self-sustainment is supplied to the inner electrode layer 90, thereby promoting the reduction reaction in the inner electrode layer 90.

  FIGS. 16A and 16B are time charts showing another example of a processing procedure for performing refresh control in the SOFC apparatus 1. In this example, first, when the start-up mode operation is performed, the open circuit voltage OCV in the open circuit state in which power is not taken out increases to about 160 V as the temperature of the fuel cell 84 rises. Then, when the temperature of the fuel cell 84 is raised to a temperature sufficient for power generation, the operation shifts to normal power generation operation.

It enters the power generation operation, the power generation (power from the fuel cell 84 is taken out: more specifically, as shown in FIG. 16 (B), for example, a current to output the I _t) When starting the, in FIG. 16 (A) As indicated by the solid line, the voltage decreases (drops) in accordance with the magnitude of the extracted power. As shown in solid line, the output voltage after drop, if not less than the lower limit voltage V _limit (see FIG. 16 (A)) is the voltage reference value is predetermined in accordance with the current I _t, the fuel It is presumed that the battery cell 84 is not in the oxide excess state (is in the non-oxide excess state).

Here, the present inventors show SOFC device 1 and the equivalent settings of the current I _t and the lower limit voltage V _limit that defines the result of the operation test using the apparatus having the configuration of (table) Example below.
・ When I _t = 7A, V _limit = 109V
・ When I _t = 6A, V _limit = 112V
・ When I _t = 5A, V _limit = 115V
・ When I _t = 4A, V _limit = 119V
・ When I _t = 3A, V _limit = 124V
・ When I _t = 2A, V _limit = 129V

On the other hand, as shown by the broken line in FIG. 16A, when the output voltage after the decrease is lower than the lower limit voltage V _limit , it is estimated that the fuel cell 84 is in an excessive oxide state. The refresh control is executed according to the procedure shown in FIGS. 12 (A) and 12 (B) to FIG. By doing so, it is possible to further improve the estimation accuracy (accuracy) of whether or not the fuel cell 84 is in an excessive oxide state, so that the recovery characteristic of the power generation performance of the fuel cell 84 can be further improved. .

  In addition, as above-mentioned, this invention is not limited to the specific example demonstrated in said embodiment, A various deformation | transformation is possible in the limit which does not change the summary. That is, those obtained by appropriately modifying the design of those specific examples by those skilled in the art are also included in the technical scope of the present invention as long as they have the features of the present invention. In other words, the elements included in the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, and can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as much as technically possible, and the combination of these is also included in the technical scope of the present invention as long as it includes the features of the present invention.

  For example, in the processing procedure shown in FIG. 11, after the refresh control is executed, the elapsed time tr is not reset (that is, step S5 is omitted), and the time measurement by the timer 160 is resumed by returning to the normal power generation operation. In step S1, the measurement time may be added to the elapsed time tr before execution of the refresh control. In this case, the elapsed time tr represents the total accumulated cumulative power generation time from the start of the first normal power generation operation in the SOFC device 1, and in step S2, based on the comparison result between the elapsed time tr and the predetermined value t1, It may be estimated whether or not the fuel cell 84 is in an excessive oxide state.

  Further, in the processing procedure of the figure, in order to estimate whether or not the fuel cell 84 is in an excessive oxide state, instead of the elapsed time tr and its predetermined value t1, the total power generation amount wr and its predetermined value w1. May be used. That is, in step S <b> 1, after performing the first start-up process (start-up mode operation) before power generation, the control unit 110 starts power generation from the start of power generation based on the current and voltage detection signals of the inverter 54 by the power state detection sensor 126. Is detected. Next, in step S2, the control unit 110 performs a comparison operation between the predetermined value w1 for the preset power generation amount and the measured total power generation amount wr, similarly to the predetermined value t1 for the power generation time, and wr> w1. (Step S2: YES), it is estimated that the fuel cell 84 is in an excessive oxide state, and steps S3 and S4 are performed to perform refresh control. When wr ≦ w1 is satisfied (step S2 : NO), it is estimated that the fuel cell 84 is not in the excessive oxide state (in the excessive non-oxide state), and the process returns to the normal power generation operation without performing the refresh control.

  Even by such a procedure, the estimation accuracy (accuracy) as to whether or not the fuel cell 84 is in an excessive oxide state can be sufficiently and extremely easily increased, so that the power generation performance of the fuel cell 84 can be improved. It can be recovered in a timely and effective manner.

  Further, in this case, the total power generation amount wr may be reset in step S5, or may not be reset by omitting step S5, as in the case of necessity of reset for the elapsed time tr. As in the former case, when step S5 is performed, the total power generation amount wr becomes an integrated value of the power generation amount of the SOFC device 1 after executing the refresh control of the fuel cell 84, and normal power generation operation is resumed. In the subsequent step S2, it is estimated that the fuel cell 84 is in an excessive oxide state when the total power generation amount wr after execution of the previous refresh control exceeds a predetermined value w1.

  Further, when the refresh control of the fuel cell 84 is executed in the start-up mode operation, the steam reforming reaction (SR) as shown in FIG. Even if control is performed such that the supply amount of the fuel gas supplied to the inner electrode layer 90 is larger than the supply amount of the fuel gas supplied to the inner electrode layer 90 in the normal start-up mode operation in which the refresh control is not executed. Good.

  By doing so, in the normal start-up mode operation, the fuel cell 84 is supplied with a sufficient amount of fuel gas to heat the fuel cell 84 to suppress an increase in the amount of fuel gas used, and in the start-up mode operation in which refresh control is performed, Since the oxide of the inner electrode layer 90 can be sufficiently reduced by increasing the amount of fuel gas supplied to the fuel cell 84, the power generation performance can be reliably and sufficiently recovered, and the economy and operability can be improved. It is possible to achieve both.

  As described above, according to the SOFC device of the present invention, it is possible to prevent a decrease in power generation performance during the operation, thereby continuing the power generation operation with high power generation efficiency while maintaining excellent power generation capacity. Therefore, it can be widely and effectively used for SOFC that can be used in various applications, equipment, devices, systems, equipment, and the like equipped with the SOFC, and their production and use.

  1: solid oxide fuel cell (SOFC) device, 2: fuel cell module, 4: auxiliary unit (auxiliary), 6: housing, 8: sealed space, 10: power generation chamber, 12: fuel cell assembly 12a: upper surface, 12b: lower surface, 12c: long side surface, 12d: short side surface, 14: fuel cell stack, 16: fuel cell unit, 18: combustion chamber, 20: reformer, 22: heat exchange 24: water supply source, 26: pure water tank, 28: water flow rate adjustment unit, 30: fuel supply source, 32: gas shutoff valve, 36: desulfurizer, 38: fuel flow rate adjustment unit, 40: air supply source 42: solenoid valve, 44: reforming air flow rate adjustment unit, 45: power generation air flow rate adjustment unit, 46: first heater, 48: second heater, 50: hot water production apparatus, 52: control box, 54: Inverter, 55: off 56: casing, 58: evaporative mixer, 60: reformed gas supply pipe, 62: water supply pipe, 64: fuel supply pipe, 66: manifold, 66a: lower end side, 68: fuel gas tank, 70: combustion Gas piping, 72: Air flow passage for power generation, 72a: Outlet port, 74: Air introduction pipe for power generation, 74a: Inlet, 76: Air supply passage for power generation, 78: Air outlet, 80: Combustion gas discharge chamber, 82 : Combustion gas discharge pipe, 83: ignition device, 84: fuel cell, 86: inner electrode terminal, 88: fuel gas flow path, 90: inner electrode layer (fuel electrode layer), 90a: upper part, 90b: outer peripheral surface, 90c: upper end surface, 92: outer electrode layer (air electrode layer), 94: electrolyte layer (solid electrolyte layer), 96: sealing material, 98: fuel gas flow path, 110: control unit (control means), 112: operation Device, 114: display device, 116: report Apparatus: 120: combustible gas detection sensor, 122: detection sensor, 124: hot water storage state detection sensor, 126: power state detection sensor (control means), 128: air flow rate detection sensor for power generation, 130: air flow rate sensor for reforming, 132: Fuel flow sensor, 134: Water flow sensor, 136: Water level sensor, 138: Pressure sensor, 140: Exhaust temperature sensor, 142: Power generation chamber temperature sensor, 144: Combustion chamber temperature sensor, 146: Exhaust gas chamber temperature sensor, 148: reformer temperature sensor, 150: outside air temperature sensor, 160: timer (control means).

Claims (13)

A solid oxide fuel cell device that generates power with fuel gas and oxidant gas,
A reformer for reforming a raw material gas containing hydrocarbons to produce the fuel gas containing hydrogen gas;
A fuel electrode layer supplied with the fuel gas, an air electrode layer supplied with the oxidant gas, and a solid electrolyte layer provided between the fuel electrode layer and the air electrode layer, and A fuel cell in which the fuel gas flows from one end side to the other end side;
Fuel gas supply means for supplying the fuel gas to the fuel electrode layer;
Oxidant gas supply means for supplying the oxidant gas to the air electrode layer;
Control means for monitoring and controlling the operating state of the solid oxide fuel cell device;
Oxidation estimation means for estimating whether or not the fuel cell is in an excessive oxide state;
With
The control means is a refresh control for supplying the fuel gas to the fuel electrode layer so as to satisfy a predetermined reduction promotion condition when the fuel cell is estimated to be in an excessive oxide state by the oxidation estimating means. Is to perform
Solid oxide fuel cell device. The control means is configured to lower the utilization rate of the fuel gas when the refresh control is being performed than the utilization rate of the fuel gas when the refresh control is not being performed.
The solid oxide fuel cell device according to claim 1. Combusting the fuel gas that has passed through the fuel cell, and comprising a combustion section that heats the fuel cell with the combustion heat,
The control means reduces the fuel gas utilization rate when the refresh control is being executed and increases the flow rate of the fuel gas passing through the fuel cell than when the refresh control is not being executed. To increase the heat of combustion,
The solid oxide fuel cell device according to claim 2. The control means makes the temperature of the fuel cell when the refresh control is executed higher than a temperature predetermined according to the generated electric power when the refresh control is not executed. is there,
The solid oxide fuel cell device according to claim 3. The control means is configured to make the temperature of the fuel cell when the refresh control is being executed higher than a predetermined temperature according to the upper limit of the generated power when the refresh control is not being executed. is there,
The solid oxide fuel cell device according to claim 4. The control means suppresses power generation in the fuel battery cell when the refresh control is executed as compared with a case where the fuel battery cell is not in an excessive oxide state.
The solid oxide fuel cell device according to claim 5. The control means performs a start-up mode operation in which the fuel cell is heated to a temperature capable of generating power, and the first time after the fuel cell is estimated to be in an excessive oxide state by the oxidation estimation means. The refresh control is executed during start-up mode operation.
The solid oxide fuel cell device according to claim 3. The control means supplies the supply amount of the fuel gas supplied to the fuel electrode layer in the start-up mode operation for executing the refresh control to the fuel electrode layer in the start-up mode operation that does not execute the refresh control. Is larger than the fuel gas supply,
The solid oxide fuel cell device according to claim 7. The control means performs the partial oxidation reforming reaction step, the autothermal reforming reaction step, and the steam reforming reaction step in the start-up mode operation, and performs the refresh control in the start-up mode operation. The execution time of the steam reforming reaction step is longer than the execution time of the steam reforming reaction step in the start-up mode operation that does not execute the refresh control.
The solid oxide fuel cell device according to claim 8. The oxidation estimating means causes the fuel cell to be in an excessive oxide state when the accumulated power generation time after the start of operation or the previously generated cumulative power generation time after the refresh control reaches a predetermined value set in advance. It is presumed that there is
The solid oxide fuel cell device according to claim 3. The oxidation estimation means estimates that the fuel cell is in an excessive oxide state when the accumulated power generation time after the previously executed refresh control reaches a predetermined value set in advance, and starts operation. The predetermined value is changed according to the cumulative number of executions of subsequent refresh control.
The solid oxide fuel cell device according to claim 10. The oxidation estimating means determines whether the fuel cell is an oxide based on whether the total power generation after the start of operation or the total power generation after the refresh control executed last time has reached a predetermined value. It is to estimate whether there is an excessive state,
The solid oxide fuel cell device according to claim 3. The oxidation estimation unit is configured to oxidize the fuel cell when the output voltage when the power is extracted from the fuel cell during power generation is smaller than a reference value set in advance according to the value of the extracted power. It is estimated to be in an overload state.
The solid oxide fuel cell device according to claim 3.