JP5787049B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell.

  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, supplies fuel gas on one side, and supplies the other This is a fuel cell that operates at a relatively high temperature by supplying an oxidizing agent (air, oxygen, etc.) to the side.

  In this SOFC, water vapor or carbon dioxide is generated by the reaction between oxygen ions that have passed through the oxide ion conductive solid electrolyte and fuel, and electric energy and thermal energy are generated. Electric energy is taken out of the SOFC and used for various electrical applications. On the other hand, thermal energy is used to raise the temperature of fuel, SOFC, oxidant and the like.

  It is known that fuel cells are deteriorated by long-term use. Along with the deterioration of the fuel cell, a decrease in the generated voltage value and a local increase in temperature due to a partial increase in electrical resistance appear as phenomena. One of the causes of deterioration of the fuel cell is considered to be a reduction in an effective area (area) of a current generation portion in the fuel cell. Thereby, when the effective area decreases, the power generation voltage value of the fuel cell decreases. If current is similarly drawn from the fuel cell in this state, the drawn current per unit area becomes excessive, and the burden on the fuel cell increases. Thereby, deterioration of the fuel cell is further promoted.

  The fuel cell described in Japanese Patent Application Laid-Open No. 2004-265671 (Patent Document 1) is configured to decrease the upper limit current value of the current drawn from the fuel cell in accordance with the decrease in the generated voltage value. In the fuel cell of patent document 1, since the burden of a fuel cell is reduced by the restriction | limiting of the upper limit electric current value according to the fall of a generated voltage value, deterioration of a fuel cell can be suppressed.

JP 2004-265671 A

  However, the fuel cell of Patent Document 1 can extend the useful life by suppressing deterioration of the fuel cell, but there is room for improvement from the viewpoint of maximizing the power supply capacity of the fuel cell. .

  Accordingly, an object of the present invention is to provide a solid oxide fuel cell capable of extending the useful life of the fuel cell while maximizing the power supply capability of the fuel cell.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates power by supplying fuel and an oxidant gas to a plurality of solid oxide fuel cells. A fuel cell module, fuel supply means for supplying fuel to the fuel cell module, oxidant gas supply means for supplying oxidant gas to the fuel cell module, and voltage value detection for detecting a power generation voltage value by the fuel cell module Means, a current value detecting means for detecting an output current value by the fuel cell module, and a control means for controlling the amount of fuel supplied from the fuel supply means, the control means having a smaller power generation voltage value. Set the upper limit current value to a small value and execute current limit control to control the output power of the fuel cell module so that the output current value does not exceed the upper limit current value. The means determines the deterioration of the fuel cell module, and based on the deterioration determination, executes a deterioration countermeasure that controls the fuel supply means so as to recover the power generation voltage value decreased due to the deterioration and corrects the increase in the fuel supply amount. Based on the deterioration determination, the control means changes the upper limit current value for each power generation voltage value used in the current limit control to a value smaller than the upper limit current value used at the time of deterioration determination. The deterioration suppression control is executed, and the control means is configured to execute the deterioration suppression control a plurality of times within the product life of the solid oxide fuel cell. However, it is characterized in that the reduction correction amount of the upper limit current value is set to be smaller than the deterioration suppression control in the second half .

In the present invention configured as described above, the smaller the generated voltage value, the smaller the upper limit current value is set, and the current is controlled so that the output current value from the fuel cell module does not exceed the set upper limit current value. Limit control is performed. Thereby, since extraction of an excessive current can be restricted according to deterioration of the fuel cell module, durability of the fuel cell can be improved.
Further, in the present invention, when the progress of deterioration increases, the power generation voltage value is recovered by the deterioration corresponding control, so that the state is restored to the use state at the upper limit current value of the large limit value, in other words, the current that leads to the suppression of the maximum output. It is possible to avoid taking restrictions easily. As a result, the power supply performance of the fuel cell can be used to the maximum for a long period.
As described above, in the present invention, the current limit control using the upper limit current value and the deterioration countermeasure control by the fuel increase correction can be performed by one control. Therefore, the power supply of the fuel battery cell can be performed with a simple control configuration. It is possible to greatly improve the durability of the fuel cell while using the maximum performance.

According to the present invention, the upper limit value of the output current value is further limited by the deterioration suppression control, with the upper limit current value being changed to a smaller value in accordance with the progress of deterioration. Accordingly, excessive current extraction from the fuel cell module can be restricted according to the progress of deterioration, and the progress of deterioration of the fuel cell can be suppressed to further improve the durability of the fuel cell. Further, the deterioration of the fuel cell progresses as the operating time of the solid oxide fuel cell elapses. Therefore, in the present invention, the amount of decrease correction from the upper limit current value is set smaller in the deterioration suppression control executed in the first half when the progress of deterioration is lighter than the deterioration suppression control executed in the second half when the progress of deterioration is large. doing. As a result, in the present invention, it is possible to accurately achieve both extension of the durability of the fuel cell and maintenance of the power generation performance with simple control in accordance with the degree of progress of deterioration of the fuel cell.

In the present invention, it is preferable that the control unit performs the current limit control without executing the deterioration handling control until the predetermined deterioration degree is detected by the deterioration determination, and the predetermined deterioration degree is detected. In addition, deterioration countermeasure control is executed.
According to the present invention configured as described above, the current limiting control and the degradation countermeasure control can be executed based on the degradation degree that is the same control parameter, so that the control becomes easy. In addition, since the deterioration countermeasure control is executed when the degree of deterioration increases, the excessive load on the fuel cell is reduced by suppressing the frequency of fuel increase correction that accompanies the temperature rise of the fuel cell. However, the progress of deterioration of the fuel cell can be suppressed, and the durability of the fuel cell can be further improved.

In the present invention, preferably, the control means sets the upper limit current value in each power generation voltage value to the upper limit current value set when the use of the solid oxide fuel cell is started in accordance with the execution of the deterioration countermeasure control. It returns to a certain reference upper limit current value or a current value smaller than this reference upper limit current value.
According to the present invention configured as described above, the upper limit current value can be returned to the reference upper limit current value when the power generation voltage value is recovered by the deterioration countermeasure control. However, depending on the degree of deterioration, restrictive correction is applied so that the upper limit current value is returned to a current value smaller than the reference upper limit current value. Thus, in the present invention, by simple control, the burden on the fuel cell is further reduced and the service life is extended while maximizing the power supply performance of the fuel cell according to the degree of deterioration. Can do.

In the present invention, preferably, in the second half, the deterioration suppression control is set such that the decrease correction amount in the high-voltage-side generated voltage value is larger than the decrease correction amount in the low-voltage-side generated voltage value.
According to the present invention configured as described above, in the second half when the progress of deterioration is large, when the deterioration further progresses, the reduction range of the upper limit current value with respect to the generated voltage value on the high voltage side is made larger than that on the low voltage side. Thus, since the upper limit current value on the high voltage side is more greatly limited, the load of the fuel cell can be further reduced and further deterioration can be suppressed.

In the present invention, preferably, the control means is configured to execute the deterioration countermeasure control a plurality of times within the product life of the solid oxide fuel cell, and the fuel supply amount in the deterioration countermeasure control executed in the second half. Is set to be larger than the fuel supply amount increase correction amount in the deterioration countermeasure control executed in the first half.
As the operating time of the solid oxide fuel cell elapses, the deterioration of the fuel cell progresses. Therefore, in the present invention, the increase correction amount in the deterioration handling control executed in the second half is set larger than the increase correction amount in the deterioration handling control executed in the first half. As a result, according to the present invention, it is possible to use the power supply performance of the fuel battery cell to the maximum while suppressing the deterioration and ensuring the power generation performance in accordance with the progress of the deterioration of the fuel battery cell.

In the present invention, it is preferable that the control unit does not execute the deterioration countermeasure control until the deterioration suppression control is executed a predetermined number of times.
According to the present invention configured as described above, when the deterioration of the fuel cell module has not progressed significantly, the deterioration suppression control is executed without executing the deterioration countermeasure control, thereby suppressing the progress of the deterioration. As a result, it is possible to extend the durable years of the fuel cell without placing a burden on the fuel cell due to the increase in fuel and without causing a decrease in the fuel utilization rate due to the increase in fuel.

In the present invention, preferably, the control means executes the current limiting control without executing the deterioration handling control and the deterioration suppression control until the first deterioration degree is detected based on the deterioration determination, When the degree of deterioration is detected, the deterioration handling control is executed. After that, when the second degree of deterioration larger than the first degree of deterioration is detected, the deterioration suppression control is executed. .
According to the present invention configured as described above, the progress of the deterioration is suppressed only by the current limiting control until the deterioration progresses to some extent. When the voltage value is recovered and further deterioration proceeds in this state, further deterioration is suppressed by changing the upper limit value to a smaller value by the deterioration suppression control. As a result, by controlling the progress of deterioration according to the degree of progress of deterioration, it is possible to suppress a decrease in fuel utilization rate and to maximize the power supply performance of the fuel battery cell while The durability can be extended.

In the present invention, it is preferable that the control unit executes the deterioration countermeasure control when the third deterioration degree larger than the second deterioration degree is detected after the second deterioration degree is detected. Without current limit control.
According to the present invention configured as described above, when the deterioration has progressed to a considerable extent, the current limit control is executed without applying a burden due to the increase in fuel of the deterioration countermeasure control, so that the life of the fuel cell unit can be increased. Can be extended.

In the present invention, preferably, after the third deterioration degree is detected, the control unit further executes the deterioration suppression control based on the deterioration determination, but does not execute the deterioration countermeasure control.
According to the present invention configured as described above, after the third deterioration degree is detected, the deterioration suppression control is executed without executing the deterioration countermeasure control, so that the durability of the fuel cell can be increased. Can be extended.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates power by supplying fuel and an oxidant gas to a plurality of solid oxide fuel cells. A fuel cell module, fuel supply means for supplying fuel to the fuel cell module, oxidant gas supply means for supplying oxidant gas to the fuel cell module, and voltage value detection for detecting a power generation voltage value by the fuel cell module Means, a current value detection means for detecting an output current value by the fuel cell module, and a control means for controlling the amount of fuel supplied from the fuel supply means. The control means has an upper limit as the generated voltage value is smaller. Set the current value to a small value and execute current limit control to control the output power of the fuel cell module so that the output current value does not exceed the upper limit current value. Performs the deterioration determination of the fuel cell module, on the basis of the deterioration determination, changes the upper limit current value for each generated voltage value used in the current limit control, to a value smaller than the upper limit current value that was used during the deterioration determination The deterioration suppression control is executed, and the control means is configured to execute the deterioration suppression control a plurality of times within the product life of the solid oxide fuel cell. It is characterized in that the reduction correction amount of the upper limit current value is set to be smaller than the deterioration suppression control in the second half .

In the present invention configured as described above, the smaller the generated voltage value, the smaller the upper limit current value is set, and the current is controlled so that the output current value from the fuel cell module does not exceed the set upper limit current value. Limit control is performed. Thereby, since extraction of an excessive current can be restricted according to deterioration of the fuel cell module, durability of the fuel cell can be improved.
Further, in the present invention, the upper limit value of the output current value is further limited by the deterioration suppression control as the upper limit current value is changed to a smaller value in accordance with the progress of the deterioration. Accordingly, excessive current extraction from the fuel cell module can be restricted according to the progress of deterioration, and the progress of deterioration of the fuel cell can be suppressed to further improve the durability of the fuel cell.
As described above, in the present invention, by performing the current limit control using the upper limit current value and the deterioration suppressing control for restricting the upper limit current value itself, the durability of the fuel cell can be greatly improved. Is possible.
Further, the deterioration of the fuel cell progresses as the operating time of the solid oxide fuel cell elapses. Therefore, in the present invention, the amount of decrease correction from the upper limit current value is set smaller in the deterioration suppression control executed in the first half when the progress of deterioration is lighter than the deterioration suppression control executed in the second half when the progress of deterioration is large. doing. As a result, in the present invention, it is possible to accurately achieve both extension of the durability of the fuel cell and maintenance of the power generation performance with simple control in accordance with the degree of progress of deterioration of the fuel cell.

  According to the solid oxide fuel cell of the present invention, the useful life of the fuel cell can be extended while maximizing the power supply capability of the fuel cell.

1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a front sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention. FIG. 3 is a sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to one embodiment of the present invention. 1 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of operation stop of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the driving | operation of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a graph which shows an example of the relationship between the required electric power generation amount input into a control part, and the fuel supply amount required in order to produce | generate a required electric power generation amount. It is a graph which shows an example of the time change of the fuel supply amount with respect to the change of the required power generation amount. It is a graph which shows the output operation point of the fuel cell module by one Embodiment of this invention. 4 is a graph illustrating a current limiting line according to an embodiment of the present invention. It is a processing flow of degradation control by one embodiment of the present invention. It is a processing flow of deterioration control by other embodiments of the present invention.

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

  The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed inside the housing 6 via a heat insulating material (not shown, but the heat insulating material is not an essential component and may not be necessary). Is formed. In addition, you may make it not provide a heat insulating material. A fuel cell assembly 12 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

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

  Next, the auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as tap water and uses the filter to obtain pure water, and a water flow rate that adjusts the flow rate of the water supplied from the water storage tank. An adjustment unit 28 (such as a “water pump” driven by a motor) is provided. 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 air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the flow rate of air, and a power generation air flow rate adjusting unit. 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The power state detection sensor 126 is a plurality of sensors for detecting the current and voltage of the fuel cell module 2, the inverter 54, and the distribution board (not shown).
The power generation air flow rate detection sensor 128 is for detecting the flow rate of power generation air supplied to the power generation chamber 10.
The reforming air flow sensor 130 is for detecting the flow rate of the reforming air supplied to the reformer 20.
The fuel flow sensor 132 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

The water flow rate sensor 134 is for detecting the flow rate of pure water (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 FIG. 3, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14 to thereby detect the fuel cell stack. 14 (ie, the fuel cell 84 itself) is estimated.
The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20.
The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Next, the operation of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described with reference to FIGS.
First, the normal operation of the solid oxide fuel cell 1 will be described with reference to FIGS. FIG. 9 is a time chart showing the operation at the time of operation of the solid oxide fuel cell of the present embodiment. FIG. 10 is a graph showing an example of the relationship between the required power generation amount input to the control unit 110 and the fuel supply amount necessary to generate the required power generation amount. FIG. 11 is a graph illustrating an example of a temporal change in the fuel supply amount with respect to a change in the required power generation amount. FIG. 12 is a graph showing output operating points of the fuel cell module according to the present embodiment.

  In FIG. 9, the solid oxide fuel cell 1 performs a load following operation so as to output electric power corresponding to the required power generation amount from the inverter 54 (FIG. 6). That is, as shown in FIG. 6, the control unit 110 serving as the control unit performs the fuel flow adjustment unit 38 serving as the fuel supply unit and the power generation air serving as the oxidant gas supply unit according to the required power generation amount from the inverter 54. Signals are sent to the flow rate adjusting unit 45 and the water flow rate adjusting unit 28 serving as water supply means, and fuel, air, and water at the required flow rates are supplied to the fuel cell module 2. As a result, as shown in FIG. 9, the output power of the solid oxide fuel cell 1 changes so as to follow the required power generation amount from the inverter 54.

  The control unit 110 determines the fuel supply amount according to the graph shown as an example in FIG. 10 according to the required power generation amount from the inverter 54. Then, the controller 110 controls the fuel flow rate adjustment unit 38 so that the determined fuel supply amount is supplied to the fuel cell module 2. After the use of the solid oxide fuel cell 1 is started, the control unit 110 determines the fuel supply amount relative to the required power generation amount according to the curve F0 that defines the basic fuel supply amount. As shown in FIG. 10, the fuel supply amount is determined so as to increase monotonously with an increase in the required power generation amount. However, the fuel supply amount is set to a substantially constant value when the required power generation amount is less than about 200 W.

  When the required power generation amount is changed, the fuel supply amount is increased or decreased as shown in FIG. As shown in FIG. 11, when the required power generation amount is changed from 500 W to 700 W at time t10, the required fuel supply amount is changed from the supply amount corresponding to the power output of 500 W to the supply amount corresponding to 700 W. The Accordingly, the control unit 110 controls the fuel flow rate adjustment unit 38 so that the fuel supply amount increases to a supply amount corresponding to 700 W.

Similarly, when the required power generation amount is changed from 700 W to 500 W at time t11, the control unit 110 controls the fuel flow rate adjustment unit 38 so that the fuel supply amount decreases to the supply amount corresponding to 500 W.
10 and 11 relate to the fuel supply amount, the air supply amount and the water supply amount are similarly changed according to the required power generation amount.

FIG. 12 shows the output characteristics of the fuel cell module 2. The output power of the fuel cell module 2 is represented by an output operating point specified by an output voltage value (generated voltage value) and an output current value (drawn current value).
In a state where there is no deterioration, the output operating point of the fuel cell module 2 moves on the curve P1 in FIG. That is, when the control unit 110 determines the fuel supply amount with respect to the required power generation amount based on the curve F0 (FIG. 10), the output power specified at the operating point on the curve P1 (FIG. 12) is determined in a state where there is no deterioration. It can be supplied to the inverter 54.

For example, when the required power generation amount is between 590 W and 700 W, the operating point moves on the curve P1 between an intersection with the curve Q1 (operating point R1) and an intersection with the curve Q3 (operating point R2). When the required power generation amount is 700 W (rated power), the control unit 110 determines the power specified by the operating point R1 (about 116 V, about 6.7 A) intersecting the curve Q1 (conversion efficiency 90%) as a fuel cell module. The inverter 54 can be controlled so as to output from 2.
Note that the curves Q1, Q2, and Q3 in FIG. 12 are curves with output powers of 700 W, 630 W, and 590 W (conversion efficiency of 90%, respectively).

On the other hand, if the fuel cell module 2 deteriorates, the required power generation amount cannot be obtained even if the fuel is supplied at the fuel supply amount determined based on the curve F0. That is, at the time of deterioration, the relationship between the required power generation amount and the fuel supply amount is virtually shifted upward in FIG.
Curves P2 and P3 in FIG. 12 show the output of the fuel cell module 2 in the deteriorated state. When the fuel cell module 2 is operated under the same operating conditions (fuel supply amount, air flow rate, water flow rate, etc.) in the deteriorated state, the generated voltage value is reduced as compared with a state in which the fuel cell module 2 is not deteriorated. Therefore, in FIG. 12, the curves P2 and P3 are located below the curve P1. Further, the curve P3 shows a state in which the deterioration has progressed more than the curve P2. When the deterioration further proceeds than the curve P3, the operating point moves to a curve (not shown) located below the curve P3.

For example, in a state where deterioration corresponding to the curve P2 occurs, the control unit 110 determines the fuel supply amount relative to the required power generation amount on the curve P2 (FIG. 12) based on the curve F0 (FIG. 10). Only the output power based on the generated voltage value and the drawn current value determined at the operating point can be supplied to the inverter 54.
Therefore, when the required power generation amount is between 590 W and 700 W, the operating point moves on the curve P2 between the intersection with the curve Q1 (operating point R3) and the intersection with the curve Q3 (operating point R4). For example, when the required power generation amount is 700 W, the control unit 110 causes the inverter to output from the fuel cell module 2 at an operating point R3 (about 105 V, about 7.6 A) that intersects the curve Q1 (conversion efficiency 90%). 54 is controlled. The operating point R3 has a smaller voltage value and a larger current value than the operating point R1. That is, as the deterioration progresses, the drawn current for outputting the same power has a larger current value.
In FIG. 12, the intersection of the curve P3 and the curve Q1 is indicated by an operating point R5, and the intersection of the curve P3 and the curve Q3 is indicated by an operating point R6.

  In the present embodiment, the control unit 110 supplies the fuel supply amount based on the curve F0. However, the control unit 110 supplies the fuel supply amount based on the deterioration countermeasure control described later, rather than the fuel supply amount based on the reference curve F0. Correct the increase. A curve F1 in FIG. 10 shows a correction curve in which the amount of increase is corrected by 3% with respect to the reference value (curve F0). Similarly, the curve F2 is further corrected by 3% more than the curve F1. Between the adjacent curves F2, F3, F4, F5, F6, F7,..., The increase is corrected by 5%. The control unit 110 stores the curves F1, F2, F3, F4, F5, F6, F7,.

  Next, the deterioration control process of the solid oxide fuel cell 1 will be described with reference to FIGS. 13 and 14. FIG. 13 is obtained by adding a current limiting line in the solid oxide fuel cell of this embodiment to FIG. FIG. 14 is a processing flow of deterioration control.

  In the fuel cell module 2, as shown in FIG. 12, the output operating point moves on the curves P1, P2, P3,... According to the progress of deterioration and the required power generation amount. As described above, the power generation voltage value decreases as the deterioration progresses, so the output current must be increased to secure the required power generation amount. However, if the output current becomes excessively large, the burden on the fuel cell unit 16 increases, and internal deterioration of the fuel cell unit 16 proceeds.

Therefore, in this embodiment, as shown in FIG. 13, current limiting lines L1 to L5 are provided. The control unit 110 stores these current limit lines L1 to L5 in a memory. These current limit lines L1 to L5 define an upper limit current value that is a maximum value of a current that can be drawn at each power generation voltage value. As will be described later, the control unit 110 uses one of the current limit lines depending on the degree of progress of deterioration.
The current limit line L1 defines a reference upper limit current value for each generated voltage value. The reference upper limit current value is a reference upper limit current value set when the solid oxide fuel cell 1 is manufactured, and is set when the use is started.
In addition, the current limit lines L2 to L5 respectively define upper limit current values corresponding to the degree of deterioration in each generated voltage value.

In the present embodiment, the control unit 110 performs current limit control. That is, as can be seen from FIG. 13, the control unit 110 sets the upper limit current value to a smaller value as the generated voltage value is smaller above a predetermined voltage by the current limit lines L1 to L5. Then, the control unit 110 receives the detected current value of the output current extracted from the fuel cell module 2 from the power state detection sensor 126 which is a current value detecting unit, and the received detected current value is a current limit currently used. The inverter 54 is controlled so as not to exceed the upper limit current value defined by the line. The control unit 110 always executes this current limiting control when the solid oxide fuel cell 1 is in operation.
In the present embodiment, the interval between the current limit lines L1 to L5 is set wide for easy understanding, but the interval between these current limit lines can be set narrower. Further, in the present embodiment, five current limit lines are set, but an arbitrary number of one or more may be set.

The current limit line L1 intersects the curve P1 at an operating point R7 on the curve P1, and this operating point R7 is an operating point corresponding to an output power larger than the rated power (700 W). Therefore, when the fuel cell module 2 is operating at the operating point on the curve P1, the extracted current is not limited in operation below the rated power.
On the other hand, the current limit line L1 intersects the curve P2 at an operating point R3 on the curve P2, and this operating point R3 is an operating point corresponding to the rated power (700 W). Therefore, when the fuel cell module 2 is operating at the operating point on the curve P2, it is limited by the current limit line L1 at the operating point R3 only during rated operation. At this time, the extraction current is limited to about 7.6 A.

  Further, the current limit line L1 intersects the curve P3 at the operating point R8 on the curve P3, and this operating point R8 is an operating point corresponding to the output power of 630W. Therefore, when the fuel cell module 2 is operating at the operating point on the curve P3, the extraction current is limited when a power generation amount of 630 W or more is required. Therefore, in the deterioration state corresponding to the curve P3, it is not possible to output power larger than 630 W, and at this time, the maximum value of the extraction current is limited to about 7A.

Moreover, in this embodiment, it is comprised so that degradation may be detected when a generated voltage value becomes a threshold voltage value (for example, 100V) or less, and the current limiting line L1 has a generated voltage value not more than a threshold voltage value. Then, the output current value is set to a constant value (7A).
As described above, the current limit line L1 (and L2 to L5) is set so that the upper limit value of the extraction current decreases as the deterioration progresses and the generated voltage value decreases. Thereby, it is possible to prevent an excessive current from flowing in the fuel cell unit 16 due to the deterioration, and to suppress further deterioration.

Further, when the control unit 110 detects deterioration of the fuel cell module 2 based on a decrease in the generated voltage value, the current limit lines L2 and L3 are replaced with the current limit line L1 by deterioration suppression control described later. These are used sequentially, and each defines an upper limit value of the extraction current.
When the current limit line L1 is changed to L2, the upper limit value of the extraction current is corrected to decrease by about 0.2 A in the non-deterioration state corresponding to the curve P1, for example, and about 0. 0 in the deterioration state corresponding to the curve P3. It is corrected to decrease by 3A, and is corrected to decrease by about 0.3A at the generated voltage value 110V. When the current limit line L2 is changed to L3, the upper limit value of the extraction current is corrected to be decreased by about 0.4 A in the non-deterioration state corresponding to the curve P1, and about 0. 0 in the deterioration state corresponding to the curve P3. It is corrected to decrease by 7A, and is corrected to decrease by about 0.9A at the generated voltage value 110V.

  Thus, in this embodiment, as can be seen by comparing the change from the current limit line L1 to L2 with the change from the current limit line L2 to L3, the change before the change in the deterioration suppression control that is executed a plurality of times. The decrease correction amount of the current value from the upper limit current value to the changed upper limit current value is the first half before the second half of the decrease correction amount in the deterioration suppression control (for example, L2 to L3) executed in the second half. The decrease correction amount in the deterioration suppression control (for example, L1 to L2) executed in the period is set to be smaller. In other words, the present embodiment is configured to reliably suppress further deterioration by increasing the decrease correction amount as the deterioration progresses.

The current limit lines L4 and L5 are sequentially used in place of the current limit line L3 when the deterioration has progressed to a considerable extent, and each defines an upper limit value of the extraction current.
When the current limit line L3 is changed to the current limit line L4, for example, the upper limit value of the extraction current is corrected to be decreased by about 1 A in the deterioration state corresponding to the curve P1, and about 0. 0 in the deterioration state corresponding to the curve P3. It is corrected to decrease by 9A. Further, the power generation voltage value 110V is corrected to decrease by about 1.8A, and the power generation voltage value 105V is corrected to decrease by about 1.6A.
When the current limit line L4 is changed to the current limit line L5, the upper limit value of the extraction current is corrected to decrease by about 1 A in the deterioration state corresponding to the curves P1 and P3. Further, the power generation voltage value 110V is corrected to decrease by about 2.0A, and the power generation voltage value 105V is corrected to decrease by about 2.0A.

  In this embodiment, when the deterioration progresses to a considerable extent, the current limit line L3 is changed to the current limit line L4. At this time, the reduction correction of the upper limit value of the extraction current with respect to the generated voltage value on the high voltage side is performed. The amount is set larger than the decrease correction amount for the generated voltage value on the low voltage side. As a result, the maximum value among the upper limit values of the extraction current for each generated voltage value can be limited to a smaller value, and the useful life of the fuel cell module 2 can be extended.

  In the present embodiment, as will be described below with reference to the flowchart of FIG. 14, the control unit 110 changes the current limit line and corrects the increase in the fuel supply amount according to the progress of deterioration. It is configured. This increase correction of the fuel supply amount is for recovering the power generation voltage value that has decreased due to deterioration. Specifically, the control unit 110 shows the relationship between the fuel supply amount and the required power generation amount in FIG. The curve F0 is sequentially changed to curves F1, F2, F3,.

Next, with reference to FIG. 14, a processing flow of deterioration control according to the embodiment of the present invention will be described. The deterioration control process shown in FIG. 14 is repeated after the operation of the solid oxide fuel cell 1 is started until the product is exhausted and discarded. The control unit 110 is configured to repeat this deterioration control process every predetermined time (for example, every hour).
Note that at the start of use of the solid oxide fuel cell 1, L1 (reference upper limit current value) is set as the limiting current line, the number of deterioration determinations and the number of deterioration responses to be described later are set to zero, and the control unit 110 performs these operations. Is stored in the memory.

First, the control unit 110 performs deterioration determination control (steps S1 and S2) for the power generation function of the fuel cell module 2. Specifically, the control unit 110 receives the power generation voltage value of the fuel cell module 2 from the power state detection sensor 126 that is a voltage value detection unit, and whether or not the power generation voltage value is smaller than a threshold voltage value (for example, 100 V). Is determined (step S1).
If the generated voltage value is equal to or greater than the threshold voltage value (step S1; No), the deterioration is within the allowable range at the time of execution of this process, and therefore the control unit 110 ends the process without incrementing the deterioration determination number. To do.
On the other hand, when the generated voltage value is smaller than the threshold voltage value (step S1; Yes), since the deterioration exceeding the allowable range at the time of executing this process is detected, the control unit 110 increments the deterioration determination number by one. The process proceeds to step S2.

In this embodiment, the deterioration determination control (step S1) is performed by comparing the threshold voltage value and the generated voltage value. However, any method may be adopted as long as deterioration can be determined based on the generated voltage value. May be.
For example, in the present embodiment, in the deterioration determination control, the process is simplified by setting the threshold voltage value to a fixed value regardless of the degree of progress of deterioration of the fuel cell module 2, but depending on the degree of progress of deterioration. The threshold voltage value may be changed. For example, when the current limit lines L1, L3, L3,... Are used, 100V, 102V, 104,.

Further, as another deterioration determination control, based on the data representing the relationship between the generated voltage value and the extracted current value shown in FIG. 13, from the output operation point defined by the actual generated voltage value and the extracted current value, You may comprise so that deterioration determination may be performed. In this case, the deterioration determination can be performed according to the voltage drop amount from the curve P1. For example, the operating point of the curve P1 having the same current value as the current value of the measured output operating point is specified, and the voltage value at this operating point is compared with the generated voltage value at the measured output operating point to reduce the voltage. The amount can be calculated. Degradation can be detected when the voltage drop amount is larger than a predetermined threshold value.
Furthermore, as deterioration determination control, the temperature in the fuel cell module 2 may be measured by the power generation temperature sensor 142 or the like, and deterioration of the fuel cell module 2 may be determined based on this temperature.

In step S2, control unit 110 determines whether or not the deterioration determination number is 2 (step S2).
When the number of deterioration determinations is not 2 (step S2; No), there is a possibility of erroneous detection of deterioration, so the control unit 110 ends the process without resetting the number of deterioration determinations to zero.
On the other hand, when the number of deterioration determinations is 2 (step S2; Yes), since substantial deterioration is detected (the number of deterioration detections is 2), the number of deterioration determinations is reset to zero, and the process proceeds to step S3. Transition. When the use of the solid oxide fuel cell 1 is started, the number of deterioration determinations is zero. Therefore, when the generated voltage value falls below the threshold voltage value twice, the process proceeds to step S3. In the present embodiment, when the deterioration exceeding the allowable range is detected twice, it is determined that the deterioration is the deterioration, so that erroneous detection of the deterioration can be prevented. The second deterioration is detected when several years (for example, 10 years) have passed since the start of use of the solid oxide fuel cell 1.

In step S3, the control unit 110 determines whether or not the degradation correspondence number is zero (step S3).
When the number of degradation countermeasures is zero (step S3; Yes), that is, when substantial degradation is detected from the start of use (corresponding to detection of the first degradation degree as an example), the control unit 110 performs degradation countermeasure control. Is executed (step S4), and the process is terminated.

In the deterioration countermeasure control executed in step S4, the fuel supply amount is corrected by 3% and the deterioration countermeasure number is incremented by one. In the fuel supply amount increase correction in step S4, the control unit 110 changes the fuel supply amount from the curve F0 to the curve F1 in FIG. When the fuel supply amount is corrected to increase, the temperature in the power generation chamber 10 rises, so that the power generation voltage value is restored toward the power generation voltage value at the start of operation due to this temperature rise. Thereby, the upper limit current value limited by the current limit control using the current limit line 1 is recovered along with the recovery of the generated voltage value.
And by the recovery | restoration of the power generation voltage value which had fallen by deterioration, the output operation point of the fuel cell module 2 will recover | recover to the curve P1 or its vicinity, and a rated driving | operation (700W) can be ensured. For example, when the deterioration has progressed more than the deterioration state corresponding to the curve P2, the rated operation can be performed again.

  In addition, you may add deterioration determination control different from step S1 and S2 so that rated operation may be ensured until implementation of the first deterioration countermeasure control. Then, by this other deterioration determination control, when the deterioration is smaller than the deterioration determination control in steps S1 and S2 and the deterioration corresponding to the limit at which the rated operation can be performed is detected, the first deterioration countermeasure control is executed. By comprising so, the period which can ensure a rated operation can be extended.

On the other hand, when the number of deterioration correspondences is 1 or more (step S3; No), that is, when the fourth or more deterioration is detected from the start of use, is the control unit 110 set to L3 as the current limit line? It is determined whether or not (step S5).
When the current limit line L3 is not set (step S5; No), the control unit 110 determines whether L4 or L5 is set as the current current limit line (step S6).

When the current limit line L4 or L5 is not set (step S6; No), the current limit line used at that time is L1 or L2. In this case, the control unit 110 changes the current limit line to a more limited limit line as deterioration suppression control (step S7), and ends the process. Note that the degree of deterioration detected immediately before execution of step S7 corresponds to detection of the second degree of deterioration as an example. In step S7, specifically, if the current limit line is L1, the current limit line is changed to L2, and if it is L2, the current limit line is changed to L3.
As described above, in the present embodiment, further deterioration is achieved by changing the current limit line to a more limited one based on the detection of the deterioration in the processes of steps S1, S2, and S5 to S7. It is configured to suppress.
When the deterioration is detected by the deterioration determination control, the control unit 110 determines that the deterioration detected later has a higher degree of deterioration. Therefore, the control unit 110 determines that the degree of deterioration is larger when a more restrictive current limit line is used, and that the degree of deterioration is larger as the number of executions of the deterioration handling control is increased. judge.

On the other hand, when L3 is set as the current limit line in step S5 (step S3; Yes), the control unit 110 determines whether or not the degradation correspondence number is 1 or less (step S8). At the start of use of the solid oxide fuel cell 1, the number of degradation countermeasures is zero, and the number of degradation countermeasures is 1 when the first degradation countermeasure control is executed in step S4.
When the number of degradation correspondences is 1 (step S8; Yes), the control part 110 performs degradation correspondence control (step S9), and complete | finishes a process.
In the deterioration countermeasure control executed in step S9, the fuel supply amount is corrected by 3% and the deterioration countermeasure number is incremented by one. In addition, with the recovery of the power generation voltage value by the fuel increase correction, the current limit line is returned from the current limit line L3 to the current limit line L1 that defines the reference upper limit current value (corresponding to the first upper limit current value as an example). It is.

In the fuel supply amount increase correction in step S9, the control unit 110 changes the fuel supply amount to the curve F2 because the curve F1 of FIG. 10 is used.
From the start of operation until the deterioration response control in step S9 is executed, the power generation voltage value is recovered by the first deterioration response control (step S4), and the progress of deterioration is suppressed as further deterioration progresses. As much as possible, the current limit line is changed from L1 through L2 to L3 by deterioration suppression control (step S7).
In this state, since further deterioration is detected, the power generation voltage value of the fuel cell module 2 can be recovered by correcting the increase in the fuel supply amount by the second deterioration countermeasure control (step S9).

That is, if the current limit line L3 is changed to a current limit line that is more restrictive than L3, the output power from the fuel cell module 2 is further limited. Therefore, in the present embodiment, the fuel supply amount is corrected to be increased at a stage where a certain degree of deterioration has progressed, and the power generation voltage value is recovered.
The output operating point of the fuel cell module 2 recovers again to the vicinity of the curve P1 due to the recovery of the generated voltage value. Thereby, the output power from the fuel cell module 2 is recovered, and the control unit 110 can return the current limit line to L1. If the output operating point recovers to the curve P2 or higher, the rated power can be supplied again.

  Hereinafter, when the fuel supply amount is corrected and the curve F2 is used, steps S1 to S7 are further repeated, and when the current limit line is changed from L1 to L3 to L3, the process proceeds from step S5 to step S8. To do. At this time, since the number of degradation countermeasures is 2 (step S8; No), the process proceeds from step S8 to step S10 (degradation countermeasure control).

It is considered that the deterioration has progressed to some extent at the stage of performing step S10. Therefore, in step S10 executed after step S9, unlike in step S9, the correction amount of the fuel supply amount is set large. Thereby, in this embodiment, in the degradation response control executed a plurality of times, the degradation response control (for example, step S4) executed in the second half of the degradation response control (for example, steps S4 and S9) performed in the first half period. In S10 and S12), the fuel correction amount is set larger.
Specifically, in the degradation countermeasure control executed in step S10, the fuel supply amount is corrected by 5% and the degradation countermeasure number is incremented by one. Therefore, in step S10, the control unit 110 changes the fuel supply amount to the curve F3 when the curve F2 of FIG. 10 is used (deterioration correspondence number = 2), and the curve F3 is used. (Deterioration correspondence number = 3), the fuel supply amount is changed to the curve F4. When the curve F4 is used (deterioration correspondence number = 4), the fuel supply amount is changed to the curve F5, and the curve F5 Is used (deterioration response number = 5), the fuel supply amount is changed to the curve F6.
In the present embodiment, in steps S9 and S10, the fuel supply amount increase correction by the deterioration countermeasure control is performed six times in total, but this may be performed any number of times (once, twice,.・ ・) Can be changed to implement. In step S10, the correction amount of the fuel supply amount is constant, but the correction amount of the fuel supply amount may be gradually increased as the number of deterioration countermeasures increases.

However, since the deterioration has progressed to some extent, in step S10, unlike step S9, the current limit line is not the current limit line L1 that defines the reference upper limit current value, but the current limit line that defines a smaller current value. Returned to L2.
After the step S9 is performed, when the deterioration further progresses and the current limit line is changed from L1 to L3 through L2, and further large deterioration is detected, the upper limit current value is changed to the reference upper limit current value ( Simple control by adding correction to the suppression side so as to return to the current limit line L2 (corresponding to the second upper limit current value as an example) which is smaller than the first upper limit current value as an example) As a result, it is possible to further reduce the burden on the fuel cell and to extend the useful life.

  When the fuel supply amount is corrected to increase, the output operating point of the fuel cell module 2 recovers to the vicinity of the curve P1 or the curve P2 due to the recovery of the generated voltage value. However, if the current limit line L1 is used in this state, the extraction current value may be relatively high. Therefore, in this embodiment, when the deterioration has progressed to some extent, correction is performed on the suppression side, and the current limit line is returned to L2 instead of L1, thereby suppressing the taken-out current value, and the fuel cell module 2 This further reduces the burden on the company and suppresses further deterioration.

When the process proceeds from step S10 to step S11, the control unit 110 determines whether or not the degradation correspondence number is six (step S11).
When the degradation correspondence number is 5 or less (actually 3 to 5) (step S11; No), the control unit 110 ends the process.
Each time step S10 is repeated, the number of degradation correspondences increases, so steps S1 to S7, S8, S10, and S11 are repeated until the degradation correspondence number reaches six.
As a result, the fuel generation amount is corrected and the generated voltage value is recovered (step S10). In this state, whenever the deterioration is determined (steps S1 and S2), the current limit line is changed from L2 to L3 (step S10). S7). By repeating this, it is possible to extend the service life while maximally using the power supply capability of the fuel cell module 2.

On the other hand, when the number of degradation responses is 6 in step S11 (step S11; Yes), the control unit 110 performs final degradation response control and degradation suppression control (step S12), and ends the process.
Before executing step S12, the fuel increase correction of a total of 26% has been executed by the deterioration control (steps S9 and S10). Since the temperature in the power generation chamber 10 is increased according to the fuel increase correction, the final fuel increase correction is performed in step S12.

In step S12, as the final deterioration countermeasure control, the fuel supply amount is corrected by 5% and the deterioration countermeasure number is incremented by one.
In step S12, the current limit line is changed to L4 as deterioration suppression control. By setting the current limit line L4, the extraction current value is corrected to be greatly decreased on the high voltage side than on the low voltage side, so that the maximum value of the extraction current value is set lower.
By using the current limit line L4, the output power of the fuel cell module 2 is limited, but the useful life of the fuel cell module 2 can be extended.

Thereafter, when deterioration is detected in steps S1 and S2, step S6 is executed via step S3. In step S6, the control unit 110 determines whether the current current limit line is L4 or L5 (step S6).
Since the current limit line is L4 or L5 (step S6; Yes), the control unit 110 determines whether or not the generated voltage value is smaller than a second threshold voltage value (for example, 90 V) (step S13; deterioration). Judgment control).
When the generated voltage value is greater than or equal to the second threshold voltage value (step S13; No), the control unit 110 determines whether or not the generated voltage value is smaller than a third threshold voltage value (for example, 95V) ( Step S14; deterioration determination control). The third threshold voltage value is set between the first threshold voltage value (100V) and the second threshold voltage value (90V).

When the generated voltage value is equal to or greater than the third threshold voltage value (step S14; No), the control unit 110 ends the process and continues the operation of the fuel cell module 2 under the current operation conditions.
On the other hand, when the generated voltage value is smaller than the third threshold voltage value (step S14; Yes), the control unit 110 determines that a larger deterioration is in progress (equivalent to detection of the third deterioration degree as an example). ) As the final deterioration suppression control, the number of deterioration correspondences is incremented by 1, and as the final deterioration suppression control, the current limit line is set to L5 (step S15), and the process ends. Since the upper limit current value is further limited by using the current limit line L5, the deterioration of the fuel cell module 2 is further suppressed. In this case, deterioration countermeasure control is not executed.
In addition, after setting to the current limit line L5, when a predetermined deterioration level (for example, generated voltage value <93V, 92V, 91V,...) Is further detected, the deterioration suppression control is further executed. You may comprise so that it may change into a more restrictive current limiting line (L6, L7, L8, ...).

In step S13, when the generated voltage value is smaller than the second threshold voltage value (90V) (step S13; Yes), the fuel cell module 2 is at the use limit, and therefore the control unit 110 executes the abnormality handling process. (Step S16), and the process ends. In the abnormality handling process, for example, the operation of the solid oxide fuel cell 1 is stopped.
Thus, at the stage where the deterioration has progressed to a considerable extent, the fuel cell module 2 can be used by continuing the use in such a manner that the extraction current value is further limited and small output power is supplied without correcting the increase in the fuel supply amount. The service life of the can be extended. When the generated voltage value becomes smaller than the second threshold voltage value, it is assumed that the product life has been exhausted, and the abnormality handling process is performed.

  In this embodiment, after executing the first deterioration countermeasure control, the deterioration suppression control is executed a plurality of times, and then the deterioration correspondence control and the deterioration suppression control are repeated a plurality of times, and the deterioration correspondence control is executed in the final stage. However, the present invention is not limited to this, and the present invention can be configured to execute the combination of the deterioration handling control and the deterioration suppression control in any order.

  In the solid oxide fuel cell 1 of the present embodiment, the fuel cell module is executed by combining the deterioration suppression control for changing the current limit line and the deterioration countermeasure control for recovering the generated voltage value based on the deterioration determination control. The power supply capacity can be used to the maximum while extending the service life of 2.

Next, FIG. 15 shows a processing flow of deterioration control according to another embodiment of the present invention.
In the embodiment of FIG. 14, when deterioration is detected in a state where the current limit line L1 is used, the first deterioration countermeasure control in step S4 is performed. For this reason, the fuel efficiency is lowered before the deterioration suppression control is executed by the fuel increase correction in the deterioration countermeasure control. Further, when the solid oxide fuel cell 1 has a small performance margin for executing the fuel increase correction by the deterioration countermeasure control, it is desirable to reduce the number of executions of the deterioration countermeasure control.

  Therefore, in another embodiment shown in FIG. 15, steps S3 and S4 in FIG. 14 are omitted. For this reason, in another embodiment, the first and second deterioration countermeasures are executed in step S9. Therefore, the deterioration countermeasure control is not executed until the deterioration suppression control by changing the limit line is executed a predetermined number of times. Other processing steps are the same as those in FIG.

DESCRIPTION OF SYMBOLS 1 Solid electrolyte type fuel cell 2 Fuel cell module 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide fuel cell)
18 Combustion chamber 20 Reformer 28 Water flow rate adjustment unit 38 Fuel flow rate adjustment unit (fuel supply means)
44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit (oxidant gas supply means)
54 inverter 84 fuel cell 110 control unit 126 power state detection sensor (voltage value detection means, current value detection means)

Claims (10)

A solid oxide fuel cell that generates power by supplying fuel and an oxidant gas to a plurality of solid oxide fuel cells,
A fuel cell module having the solid oxide fuel cell;
Fuel supply means for supplying fuel to the fuel cell module;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell module;
Voltage value detection means for detecting a power generation voltage value by the fuel cell module;
Current value detection means for detecting an output current value by the fuel cell module;
Control means for controlling the amount of fuel supplied from the fuel supply means,
The control means sets the upper limit current value to a smaller value as the power generation voltage value is smaller, and performs current limit control for controlling the output power of the fuel cell module so that the output current value does not exceed the upper limit current value. Run,
The control means performs deterioration determination of the fuel cell module and, based on the deterioration determination, controls the fuel supply means so as to recover the power generation voltage value decreased due to deterioration, and corrects the fuel supply amount to increase. Configured to perform response control,
Based on the deterioration determination, the control means changes the upper limit current value for each power generation voltage value used in the current limit control to a value smaller than the upper limit current value used at the time of the deterioration determination. the execution,
The control means is configured to execute the deterioration suppression control a plurality of times within the product life of the solid oxide fuel cell,
The solid electrolyte fuel cell is characterized in that the deterioration suppression control is set so that the deterioration correction control of the first half period is smaller in the decrease correction amount of the upper limit current value than the deterioration suppression control of the second half period .   The control means executes the current limiting control without executing the deterioration handling control until the predetermined deterioration degree is detected by the deterioration determination, and when the predetermined deterioration degree is detected, The solid oxide fuel cell according to claim 1, wherein the deterioration countermeasure control is executed.   In accordance with the execution of the deterioration countermeasure control, the control means sets the upper limit current value at each generated voltage value to a reference upper limit value that is an upper limit current value set when the use of the solid oxide fuel cell is started. 2. The solid oxide fuel cell according to claim 1, wherein the current value is returned to a current value or a current value smaller than the reference upper limit current value. The deterioration suppression control is set, wherein the decrease correction amount in the generated voltage value on the high voltage side is set to be larger than the decrease correction amount in the generated voltage value on the low voltage side in the second half. 2. The solid oxide fuel cell according to 1.   The control means is configured to execute the deterioration countermeasure control a plurality of times within the product life of the solid oxide fuel cell, and an increase correction amount of the fuel supply amount in the deterioration countermeasure control executed in the second half Is set larger than the fuel supply amount increase correction amount in the deterioration countermeasure control executed in the first half.   2. The solid oxide fuel cell according to claim 1, wherein the control unit does not execute the deterioration countermeasure control until the deterioration suppression control is executed a predetermined number of times.   The control means executes the current limiting control without executing the deterioration handling control and the deterioration suppression control until the first deterioration degree is detected based on the deterioration determination, When the deterioration level is detected, the deterioration handling control is executed. After that, when the second deterioration level larger than the first deterioration level is detected, the deterioration suppression control is performed. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is executed. The control means does not execute the deterioration handling control when a third deterioration level greater than the second deterioration degree is detected after the second deterioration degree is detected, 8. The solid oxide fuel cell according to claim 7 , wherein the current limiting control is performed. Wherein, the third after the deterioration degree has been detected, based on said deterioration determination, further executes the said degradation control, claim 8, characterized in that do not run the deterioration handling control A solid oxide fuel cell according to 1. A solid oxide fuel cell that generates power by supplying fuel and an oxidant gas to a plurality of solid oxide fuel cells,
A fuel cell module having the solid oxide fuel cell;
Fuel supply means for supplying fuel to the fuel cell module;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell module;
Voltage value detection means for detecting a power generation voltage value by the fuel cell module;
Current value detection means for detecting an output current value by the fuel cell module;
Control means for controlling the amount of fuel supplied from the fuel supply means,
The control means sets the upper limit current value to a smaller value as the power generation voltage value is smaller, and performs current limit control for controlling the output power of the fuel cell module so that the output current value does not exceed the upper limit current value. Run,
The control means performs a deterioration determination of the fuel cell module, and based on the deterioration determination, the upper limit current value for each power generation voltage value used in the current limit control is used as the upper limit current value used in the deterioration determination. Execute deterioration suppression control to change to a smaller value ,
The control means is configured to execute the deterioration suppression control a plurality of times within the product life of the solid oxide fuel cell,
The solid electrolyte fuel cell is characterized in that the deterioration suppression control is set so that the deterioration correction control of the first half period is smaller in the decrease correction amount of the upper limit current value than the deterioration suppression control of the second half period .

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