JP6064297B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell that generates variable generated power according to demand power.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, attaches electrodes on both sides thereof, and supplies fuel gas on one side, The fuel cell operates at a relatively high temperature by supplying an oxidant (air, oxygen, etc.) to the other side.

  Japanese Patent No. 4474688 (Patent Document 1) describes a solid oxide fuel cell. In this fuel cell, the temperature monitoring band is set between the upper limit temperature and the lower limit temperature at which the fuel cell module can properly generate power, and the temperature inside the fuel cell module is controlled to fall within this band. It is carried out. Specifically, in this fuel cell, when the temperature in the fuel cell module becomes higher than the upper limit temperature, the fuel supply amount set in advance according to the power generation amount is decreased by a predetermined amount, and the lower limit temperature is set. When the temperature is lower than that, the fuel supply amount is increased by a predetermined amount to maintain the temperature in the fuel cell module within an appropriate range.

  In general, since the fuel cell module has a very large heat capacity, the internal temperature change is extremely slow, and there is a time lag of several tens of minutes to several hours until the result of temperature control is actually detected as a temperature change. . For example, when the correction for increasing the fuel supply amount is performed to increase the temperature in the fuel cell module, the temperature in the fuel cell module actually starts to increase as a result. A few hours later. For this reason, when feedback control is performed with the target temperature set at an optimum point for the temperature in the fuel cell module, overshoot and undershoot are repeated with respect to the target temperature. As a result, the temperature is unstable and fluctuates.

  In the fuel cell described in Japanese Patent No. 4474688, in consideration of such characteristics of the fuel cell module, control is performed so that the temperature in the fuel cell module falls within a temperature range having a certain width. Yes. By performing such temperature control, a unique problem in temperature control of a solid oxide fuel cell, which has a very large heat capacity and is difficult to perform feedback control, is solved.

Japanese Patent No. 4474688

  However, as in the fuel cell described in Japanese Patent No. 4474688, the temperature in the fuel cell module is not converged to an optimal target temperature, but is controlled so as to fall within a certain temperature range. When it does, there is a problem that fuel is consumed more than necessary and the power generation efficiency is lowered. That is, in this fuel cell, when the temperature in the fuel cell module becomes higher than the upper limit temperature of the set temperature band for some reason, the fuel supply amount is changed by the temperature control, and the temperature in the fuel cell module becomes a predetermined temperature. It is returned to the temperature range. Thus, after being lowered to a predetermined temperature band, the temperature in the fuel cell module often changes for a long time near the upper limit temperature of the temperature band. The predetermined temperature band is set by providing an allowable temperature margin above and below the temperature optimum for the operation of the fuel cell module. Therefore, if the temperature in the fuel cell module is operated near the upper limit temperature of a predetermined temperature range, the operation is performed at a temperature higher than the optimum temperature, and unnecessary fuel is required to maintain this high temperature. Results in wasted.

  Further, in the fuel cell described in Japanese Patent No. 4474688, when the temperature band for converging the temperature in the fuel cell module is set narrow, it passes through the set temperature band due to overshoot or undershoot of temperature control. As a result, the control becomes unstable. That is, when temperature control is performed so as to lower the temperature that is higher than the set temperature range, the temperature in the fuel cell module passes the upper limit temperature and the lower limit temperature due to the undershoot of the control, and exceeds the lower limit temperature. Will drop to a lower temperature. That is, when the temperature band is narrow, the temperature becomes unstable as in the case where feedback control is performed with a target temperature at one point as a target. In this way, when the set temperature band is wide, unnecessary fuel is consumed, and when the set temperature band is narrow, the temperature control becomes unstable. The present invention has been made to solve such problems.

  Accordingly, an object of the present invention is to provide a solid oxide fuel cell capable of stably controlling the temperature in the fuel cell module while suppressing waste of fuel.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates variable generated power according to demand power, a fuel cell module including a fuel cell stack, and the fuel cell. Fuel supply means for supplying fuel to the module, power generation oxidant gas supply means for supplying power generation oxidant gas to the fuel cell module, temperature detection means for detecting the temperature in the fuel cell module, and fuel supply means And a control means for controlling the temperature in the fuel cell module based on the detected temperature detected by the temperature detecting means while controlling the oxidant gas supply means for power generation to generate electric power according to the demand power, When the detected temperature deviates from the preset first temperature band, the control means has a detected temperature within the second temperature band preset inside the first temperature band. As described above, the first temperature control means for controlling the temperature in the fuel cell module, and once the detected temperature enters the second temperature band, the temperature in the fuel cell module is controlled to maintain the detected temperature. Control by the first temperature control means is switched to the control by the second temperature control means when the detected temperature enters the second temperature band, and the second temperature control means When the detected temperature deviates from the first temperature band, the control by is switched to the control by the first temperature control means , and the second temperature band is set as a predetermined target temperature having substantially no width. The first temperature control means controls the temperature in the fuel cell module until the detected temperature reaches the target temperature when the detected temperature deviates from the preset first temperature band. The middle value of the temperature range It is characterized in that it is set to a low temperature.

  In the present invention configured as described above, the fuel and the power generation oxidant gas are supplied from the fuel supply unit and the power generation oxidant gas supply unit to the fuel cell module including the fuel cell stack. The control means controls the fuel supply means and the power generation oxidant gas supply means to generate electric power according to the demand power, and based on the detected temperature detected by the temperature detection means, Control the temperature. The control means has first temperature control means and second temperature control means. When the detected temperature deviates from the first temperature band, the first temperature control means is configured to change the temperature in the fuel cell module so that the detected temperature enters the second temperature band set inside the first temperature band. To control. The second temperature control means controls the temperature in the fuel cell module so as to maintain the detected temperature once the detected temperature enters the second temperature band. The control by the first temperature control means is switched to the control by the second temperature control means when the detected temperature falls within the second temperature band. The control by the second temperature control means When the temperature is out of the temperature band, the control is switched to the control by the first temperature control means.

  In general, a fuel cell module of a solid oxide fuel cell has a large heat capacity and a very slow temperature change. Therefore, when temperature control is performed to converge to a certain temperature, overshoot and undershoot are repeated, and the fuel cell The temperature inside the module tends to become unstable. In order to solve this problem, it is known that the temperature in the fuel cell module is not converged to a certain temperature, but control is performed so that the temperature falls within a predetermined temperature range. Yes. However, when the control is performed so that the temperature in the fuel cell module falls within the predetermined temperature band, the time for the temperature to change near the upper limit value in the temperature band becomes longer. The inventor has found the problem of being wasted. That is, if the temperature is maintained near the upper limit value of the temperature band set higher than the optimum temperature in the fuel cell module, fuel for maintaining the temperature higher than necessary is wasted.

According to the present invention configured as described above, when the detected temperature deviates from the first temperature band, the first temperature control means falls within the second temperature band set inside the first temperature band. Control so that the detected temperature enters. As a result, the temperature in the fuel cell module is once pulled back to the second temperature band that is narrower than the first temperature band, so that the temperature in the fuel cell module is long in the vicinity of the upper limit value of the first temperature band. It is less likely to change, and waste of fuel can be suppressed. Further, the second temperature control means performs control to maintain the detected temperature once the detected temperature enters the second temperature band. For this reason, it is possible to avoid excessive overshoot and undershoot due to control aimed at convergence of the temperature in the second temperature band, and to stabilize the temperature. In addition, in spite of the control by the second temperature control means, when the temperature in the fuel cell module deviates from the first temperature band, the control is switched to the control by the first temperature control means, so that the temperature can be surely changed. It is possible to return to the temperature range of 2.
Further, according to the present invention configured as described above, when the detected temperature deviates from the first temperature band, the first temperature control means controls until the detected temperature reaches the target temperature. Control by the second temperature control means can be started from the temperature.
Further, according to the present invention configured as described above, the target temperature is set to a temperature lower than the intermediate value of the first temperature band, so that the operation of the fuel cell module is caused by the secular change of the fuel cell module. Even when the temperature rises, the temperature in the fuel cell module is unlikely to deviate from the first temperature band, and stable temperature control can be performed over a long period of time.

  In the present invention, preferably, the first temperature control means controls the temperature in the fuel cell module based on at least a deviation between the detected temperature and the target temperature, and the second temperature control means substantially detects the temperature. The temperature in the fuel cell module is controlled based only on the rate of change of temperature per hour.

  According to the present invention configured as described above, the first temperature control means performs the temperature control based on the deviation from the target temperature, so that the operation amount can be increased as the temperature is separated from the target temperature, and the temperature is reduced. The target temperature can be reliably reached. Further, since the second temperature control means substantially controls the temperature based only on the rate of change of the detected temperature per time, it is possible to prevent the operation amount from becoming excessive and the control from becoming unstable. it can.

  According to the solid oxide fuel cell of the present invention, the temperature in the fuel cell module can be stably controlled while suppressing waste of fuel.

1 is an overall configuration diagram showing a fuel cell device according to an embodiment of the present invention. It is front sectional drawing which shows the fuel cell module of the fuel cell apparatus by one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a fuel cell device by one embodiment of the present invention. It is a perspective view which shows the fuel cell stack of the fuel cell apparatus by one Embodiment of this invention. 1 is a block diagram showing a fuel cell device according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the stop of the fuel cell apparatus by one Embodiment of this invention. It is the graph which showed typically the relation of the change of demand electric power, the amount of fuel supply, and the current actually taken out from a fuel cell module. It is a figure which shows the fuel supply quantity with respect to a fuel supply electric current value. It is a figure which shows the air supply amount for electric power generation with respect to a fuel supply electric current value. It is a flowchart of the temperature control in one Embodiment of this invention. It is a time chart which shows an example of the temperature control in one Embodiment of this 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 7. A fuel cell assembly 12 that performs a power generation reaction with fuel and oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Next, with reference to FIG. 9 thru | or FIG. 13, control of the solid oxide fuel cell 1 by embodiment of this invention is demonstrated.
FIG. 9 is a graph schematically showing the relationship between the change in power demand, the amount of fuel supplied, and the current actually taken from the fuel cell module.

  As shown in FIG. 9, the fuel cell module 2 is controlled so as to be able to generate power corresponding to the demand power shown in the uppermost stage of FIG. The control unit 110 serving as a control unit sets a fuel supply current value If, which is a target current to be generated by the fuel cell module 2, based on the demand power as shown in the second graph of FIG. Although the fuel supply current value If is set so as to substantially follow the change in demand power, the response speed of the fuel cell module 2 is extremely slow with respect to the change in demand power. It is set so as to follow the demand power gently without following the change. In addition, when the demand power exceeds the rated generated power of the solid oxide fuel cell, the fuel supply current value If follows the current value corresponding to the rated generated power and is set to a current value higher than that. There is no.

  As shown in the third graph of FIG. 9, the control unit 110 controls the fuel flow rate adjustment unit 38, which is a fuel supply unit, so that the fuel supply amount at a flow rate that can generate electric power corresponding to the fuel supply current value If. Fr is supplied to the fuel cell module 2. If the fuel utilization rate, which is the ratio of the fuel actually used for power generation with respect to the fuel supply amount, is constant, the fuel supply current value If and the fuel supply amount Fr are proportional. In the graph of FIG. 9, the fuel supply current value If and the fuel supply amount Fr are drawn as being proportional to each other, but actually, the fuel utilization rate is changed according to the operating state.

  Further, as shown in the lowermost graph in FIG. 9, the control unit 110 outputs a signal that instructs the inverter 54 about the extractable current Iinv that is a current value that can be extracted from the fuel cell module 2. The inverter 54 extracts current (electric power) from the fuel cell module 2 within the range of the extractable current Iinv according to the demand power that changes suddenly every moment. The portion where the demand power exceeds the extractable current Iinv is supplied from the grid power, and this is the purchased power. Here, as shown in FIG. 9, when the current tends to increase, the extractable current Iinv instructed by the control unit 110 to the inverter 54 changes so as to be delayed by a predetermined time with respect to the change in the fuel supply amount Fr. Is set. For example, at time t10 in FIG. 9, after the fuel supply current value If and the fuel supply amount Fr start to increase, the increase of the extractable current Iinv is started with a delay. Also at time t12, after the fuel supply current value If and the fuel supply amount Fr increase, the increase of the extractable current Iinv is started with a delay. In this way, after increasing the fuel supply amount Fr, the timing for actually increasing the electric power extracted from the fuel cell module 2 is delayed.

  As a result, the fuel supplied to the fuel cell module 2 is reformed in the reformer 20, and then the reformed fuel flows into the manifold 66 that is a dispersion chamber, and each fuel constituting the fuel cell stack 14. A time delay until the battery cell unit 16 is distributed is dealt with. Further, it takes time until the actual power generation reaction becomes possible after the fuel is distributed to each fuel cell unit 16, and the timing for increasing the electric power is set in consideration of this time. This reliably prevents the fuel battery cell unit 16 from being depleted of fuel and damaging the fuel battery cell unit 16. FIG. 9 shows macroscopically and schematically the timing of the increase in the fuel supply amount Fr and the increase in the extractable current Iinv.

  Further, as described above, the remaining fuel that is supplied to each fuel cell unit 16 and is not used for power generation flows out from the upper end of each fuel cell unit 16 and is burned there by power generation air. . This combustion heat heats the reformer 20 disposed above the fuel cell stack 14 and heats the inside of the fuel cell module 2. Moreover, the heat insulating material 7 which is a heat storage material is arrange | positioned inside the fuel cell module 2, and the dissipation to the external air of the heat in the fuel cell module 2 is suppressed. Since the heat insulating material 7 has a very large heat capacity, a large amount of heat generated inside during operation of the fuel cell module 2 is accumulated in the heat insulating material 7.

  Therefore, as described with reference to FIG. 9, when the fuel supply amount Fr is increased and then the extractable current Iinv is increased with a predetermined time delay, the fuel supplied during this time is used for power generation. Instead, it is burned at the upper end of each fuel cell unit 16 and used for heating in the fuel cell module 2. Further, the combustion heat generated in this way is accumulated in the heat insulating material 7 in the fuel cell module 2. Thus, when the generated power is frequently changed and the fuel supply amount is repeatedly increased and decreased, the remaining fuel that remains without being used for power generation increases, which heats the inside of the fuel cell module 2, so that the fuel cell module 2 The temperature inside increases.

Next, temperature control of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described with reference to FIGS. 10 to 13.
FIG. 10 is a diagram illustrating the fuel supply amount with respect to the fuel supply current value, and FIG. 11 is a diagram illustrating the power generation air supply amount with respect to the fuel supply current value.

  As described above, the control unit 110 (FIG. 6) sets the fuel supply current value If, which is a target current to be generated by the fuel cell module 2, based on the demand power P. FIG. 10 is a graph showing the fuel supply amount set in advance for the fuel supply current value If set in this way. Thus, the amount of fuel supplied to the fuel cell module 2 is set in advance according to the power to be generated by the fuel cell module 2. Note that the amount of fuel consumed to generate electric power (current) increases in proportion to the increase in electric power. On the other hand, in order to generate electric power by the fuel cell module 2, it is necessary to maintain the inside of the fuel cell module 2 at an appropriate temperature, and fuel is also consumed for maintaining this temperature. That is, the remaining fuel that is not used for power generation in each fuel cell unit 16 flows out from the upper end of each fuel cell unit 16, burns there, and is used for heating in the fuel cell module 2.

  On the other hand, each fuel cell unit 16 generates power generation heat when generating electric power (current). For this reason, when the power generated by the fuel cell stack 14 is large, the inside of the fuel cell module 2 is strongly heated by the generated heat, and when the generated power is small, the heating by the generated heat is also reduced. In order to compensate for this decrease in generated heat, the fuel supply amount is set in this embodiment as shown in FIG. That is, in the region where the fuel supply current value If is large, the fuel supply amount is large, and the fuel supply current value If decreases and the fuel supply amount also decreases. However, as the fuel supply current value If decreases, the fuel supply amount increases. The amount of decrease is decreasing. For this reason, when the generated power is small, the fuel utilization rate, which is the ratio of the fuel used for power generation out of the supplied fuel, becomes low. By setting the fuel utilization rate low, the remaining fuel that is not used for power generation increases, and the residual fuel is combusted to heat the inside of the fuel cell module 2 to compensate for the decrease in generated heat.

  FIG. 11 is a graph showing a power generation air supply amount that is preset according to the fuel supply current value If. As shown in FIG. 11, as with the fuel supply amount, the power generation air supply amount is large in the region where the fuel supply current value If is large, the fuel supply current value If decreases, and the power generation air is reduced. Although the supply amount is also reduced, the reduction amount of the power generation air supply amount is set to decrease as the fuel supply current value If decreases. The control unit 110 controls the power generation air flow rate adjustment unit 45 which is a power generation oxidant gas supply means, and supplies the fuel cell module 2 with the amount of power generation air determined based on FIG.

Next, with reference to FIG. 12 and FIG. 13, the temperature control of the solid oxide fuel cell 1 according to the embodiment of the present invention will be specifically described.
FIG. 12 is a flowchart of temperature control in the present embodiment. FIG. 13 is a time chart showing an example of temperature control in the present embodiment, and shows a temperature change in the fuel cell module 2 with respect to time.

  As described above, in the solid oxide fuel cell 1 of the present embodiment, the control unit 110 determines the fuel supply amount using FIG. 10 based on the fuel supply current value If. The first temperature control unit 110a and the second temperature control unit 110b (FIG. 6) built in the control unit 110 increase or decrease the fuel supply amount by correcting the fuel supply amount determined in FIG. Control is performed so that the temperature in the module 2 is maintained in a predetermined temperature range.

  FIG. 12 is a flowchart of temperature control executed by the first temperature control means 110a and the second temperature control means 110b, and is repeatedly executed at predetermined time intervals during the power generation operation of the solid oxide fuel cell 1. . In the present embodiment, a lower limit temperature Ta = 723 ° C. and an upper limit temperature Tb = 737 ° C. are set as the first temperature zone W in which the temperature in the fuel cell module 2 should be maintained. As a target temperature, T0 = 728 ° C. is set. Preferably, the first temperature band W is set such that the target temperature T0 at which the fuel cell module 2 operates optimally is lower than the intermediate value of the first temperature band W. In general, the operating temperature of the fuel cell module 2 tends to increase due to aging, deterioration of the fuel cell stack 14, and the like. Even if the operating temperature of the fuel cell module 2 rises by setting the first temperature band W so that the target temperature T0 is lower than the intermediate value of the first temperature band W, the fuel It becomes difficult for the temperature of the battery module 2 to deviate from the first temperature zone W, and temperature control can be stabilized.

  When the temperature in the fuel cell module 2 deviates from the first temperature zone W, the first temperature control means 110a supplies the fuel supply amount so as to reach the target temperature T0 set inside the first temperature zone W. Is corrected and the first temperature control is executed. The second temperature control means 110b corrects the fuel supply amount so that the temperature in the fuel cell module 2 is maintained after the temperature in the fuel cell module 2 reaches the target temperature T0, and performs the second temperature control. Execute.

  First, in step S1 of FIG. 12, the temperature in the fuel cell module 2 is detected by the power generation chamber temperature sensor 142 which is a temperature detecting means. Next, in step S <b> 2, it is determined whether or not the detected temperature T detected by the power generation chamber temperature sensor 142 is within a first temperature band W that is not less than the lower limit temperature Ta and not more than the upper limit temperature Tb. When the detected temperature T is within the first temperature band W, the process proceeds to step S3, and when the detected temperature T is outside the first temperature band W, the process proceeds to step S5. In the example shown in FIG. 13, since the detected temperature T is within the first temperature band W at time t0, the process proceeds to step S3.

  Next, in step S3, it is determined whether or not the first temperature control flag F is 1. The first temperature control flag F is a flag indicating whether or not the first temperature control is being executed. F = 1 is set during the execution of the first temperature control, and F is set during the execution of the second temperature control. = 0 is set. Details of the first temperature control will be described later. When the first temperature control flag F is 1, the process proceeds to step S6, and when the first temperature control flag F is 0, the process proceeds to step S4. In the example shown in FIG. 13, since the first temperature control flag F = 0 at time t0, the process proceeds to step S4.

  Next, in step S4, the second temperature control by the second temperature control means 110b is executed. In the second temperature control, the fuel supply amount is corrected so that the temperature in the fuel cell module 2 is maintained. Specifically, the temperature T in the fuel cell module 2 at the time t0 is subtracted from the temperature TP in the fuel cell module 2 a predetermined time before the time t0, and the value is multiplied by the feedback gain K1 for differential control. Thus, the fuel correction amount Q1 is calculated. The fuel cell module 2 is controlled based on the fuel supply amount corrected by the fuel correction amount Q1, and one process of the flowchart of FIG. 12 is completed.

  For example, when the temperature at time t0 is higher than the temperature before a predetermined time, the value (TP-T) becomes a negative value, and the fuel correction amount Q1 is obtained by multiplying this value by the gain K1. Calculated as a negative value. Thus, in the present embodiment, the second temperature control unit 110b executes the second temperature control based only on the rate of change of the detected temperature T per time. The second temperature control means 110b corrects the fuel supply amount determined using FIG. 10 by the fuel correction amount Q1 based on the fuel supply current value If. As a result, the fuel supply amount preset in FIG. 10 is reduced by the fuel correction amount Q1, so that the remaining fuel that is not used for power generation is reduced, and the combustion heat of the remaining fuel is reduced, thereby reducing the fuel cell. The temperature in the module 2 tends to decrease. Conversely, when the temperature at time t0 is lower than the temperature before the predetermined time, the fuel correction amount Q1 is calculated as a positive value, and the fuel supply amount determined using FIG. 10 is increased. Is done. Thereby, the residual fuel increases and the temperature in the fuel cell module 2 tends to rise.

  As described above, the second temperature control by the second temperature control means 110b acts to maintain the temperature in the fuel cell module 2 at the previous temperature. In the present embodiment, the temperature one minute before is used as the temperature TP before a predetermined time. Further, in the present embodiment, even when the fuel supply amount determined using FIG. 10 is corrected to decrease, the fuel used for power generation is not short, that is, the fuel utilization rate is The correction amount is limited so that the fuel utilization rate falls within an appropriate value range so as not to exceed 1.

  In the time chart illustrated in FIG. 13, the temperature in the fuel cell module 2 increases after time t0, and exceeds the upper limit temperature Tb at time t1. Such a temperature rise occurs, for example, due to an increase in surplus fuel due to an increase in fuel supply amount prior to an increase in generated power due to frequent fluctuations in demand power. As described above, the second temperature control by the second temperature control unit 110b is performed to maintain the temperature at the previous temperature also between the times t0 and t1, but depending on the operating conditions of the fuel cell module 2, etc. May deviate greatly from the temperature at the start of the second temperature control. Even in such a case, in the second temperature control, the fuel correction amount Q1 does not increase according to the deviation from the temperature at the start of the second temperature control, so overshoot and undershoot due to control occur. Hateful. Further, in the present embodiment, since the feedback gain K1 for differential control is set to a relatively small value, unstable fluctuations in temperature due to overcompensation are avoided.

  When the temperature in the fuel cell module 2 exceeds the upper limit temperature Tb at time t1 in FIG. 13, step S5 is executed after step S2 in the flowchart in FIG. In step S5, the first temperature control flag F is set to 1. That is, when the temperature in the fuel cell module 2 is out of the first temperature band W in the state where the second temperature control by the second temperature control unit 110b is being executed, the temperature control is performed by the first temperature control unit 110a. It is switched to the first temperature control.

  Next, in step S6, the fuel correction amount Q1 is calculated by the first temperature control means 110a. Specifically, the fuel correction amount Q1 is calculated by subtracting the temperature T in the fuel cell module 2 at the time t1 from the target temperature T0 and multiplying the value by the feedback gain K0 for proportional control. Therefore, when the temperature T is higher than the target temperature T0, (T0-T) becomes a negative value, and the negative fuel correction amount Q1 is calculated by multiplying this value by the gain K0. As a result, the fuel supply amount determined using FIG. 10 is corrected to decrease by the fuel correction amount Q1.

  Subsequently, in step S7, it is determined whether or not the temperature T in the fuel cell module 2 has returned to the target temperature T0. When the temperature T returns to the target temperature T0, the process proceeds to step S8, and when the temperature T does not return to the target temperature T0, the one-time process of the flowchart of FIG. 12 ends.

  In the example shown in FIG. 13, the first temperature control is executed after exceeding the upper limit temperature Tb at time t1, but thereafter, the temperature T in the fuel cell module 2 rises until time t2. Therefore, after time t1, in the flowchart shown in FIG. 12, the process of steps S1, S2, S5, S6, S7, and return is repeatedly executed. Further, since the difference between the temperature T in the fuel cell module 2 and the target temperature T0 also increases between the times t1 and t2, the fuel correction amount Q1 also increases in the negative direction in proportion to these differences. That is, between the times t1 and t2, the fuel supply amount is gradually corrected to be reduced. As described above, in the first temperature control, the fuel supply amount is greatly corrected as the temperature T in the fuel cell module 2 deviates greatly from the target temperature T0. Therefore, the temperature T in the fuel cell module 2 is reliably set to the target. It can be returned toward the temperature T0. Next, after time t2, the temperature T in the fuel cell module 2 starts to decrease, so that the fuel supply amount reduction correction width is reduced.

  Furthermore, when the temperature T in the fuel cell module 2 returns to the first temperature zone W at time t3, step S3 is executed following step S2 in the flowchart shown in FIG. At time t3, since the first temperature control flag F = 1, step S6 is executed after step S3. Therefore, after time t3, in the flowchart shown in FIG. 12, the process of steps S1, S2, S3, S6, S7, and return is repeatedly executed, and the first temperature control is continued. Thus, the first temperature control by the first temperature control means 110a is started when the temperature T in the fuel cell module 2 deviates from the first temperature band W, but the temperature T is in the first temperature band W. It will continue after returning to.

  Even after the temperature T returns to the first temperature zone W at time t3 in FIG. 13, while the temperature T is changing between the upper limit temperature Tb and the target temperature T0, the first temperature control unit 110a performs the first operation. 1 Temperature control is continued. Next, when the temperature T reaches the target temperature T0 (T = T0) at time t4, step S8 is executed following step S7 in the flowchart shown in FIG. In step S8, the first temperature control flag F is changed to zero. After the first temperature control flag F is changed to 0 at time t4, the process of steps S1, S2, S3, S4, and return is repeatedly executed in the flowchart shown in FIG. That is, the temperature control is switched from the first temperature control by the first temperature control means 110a to the second temperature control by the second temperature control means 110b.

  In the present embodiment, the detected temperature T in the fuel cell module 2 changes very slowly with respect to the detection resolution. Therefore, when the temperature T reaches the target temperature T0, the temperature T = the target temperature T0. The conditions are always satisfied. On the other hand, if the resolution of the detected temperature T is very fine, even if the temperature T reaches the target temperature T0, the condition of temperature T = target temperature T0 may not be satisfied. For example, in a state where the detected temperature T tends to decrease, when a temperature higher than the target temperature T0 is detected and the flowchart shown in FIG. 12 is executed next, the target temperature T0 is passed over the target temperature T0. A temperature T lower than T0 may be detected. In this way, when the resolution of the detected temperature T is set finely, it is determined that the detected temperature T has reached the target temperature T0 when the detected temperature T changes across the target temperature T0. The present invention can also be configured to switch the temperature control from the first temperature control to the second temperature control.

  After the temperature T reaches the target temperature T0 at time t4 in FIG. 13, the second temperature control by the second temperature control unit 110b is continued until the temperature T deviates from the first temperature band W. Further, when the detected temperature T is lowered to a temperature lower than the lower limit temperature Ta, the temperature control is similarly performed from the second temperature control by the second temperature control means 110b to the first temperature by the first temperature control means 110a. Switch to control. In this case, the fuel correction amount Q1 calculated by multiplying by the feedback gain K0 for proportional control becomes a positive value, and the fuel supply amount determined using FIG. 10 is increased and corrected by the fuel correction amount Q1. The Thereby, the temperature T in the fuel cell module 2 tends to rise, and the temperature T is returned to the first temperature zone W. Further, the first temperature control by the first temperature control means 110a is continued even after the temperature T is returned to the first temperature band W, and when the temperature T reaches the target temperature T0, the second temperature control means 110b performs. Switch to the second temperature control.

  According to the solid oxide fuel cell 1 of the embodiment of the present invention, the first temperature control means 110a detects the detected temperature T when the detected temperature T deviates from the first temperature band W (time t1 in FIG. 13). Control is performed so as to reach the target temperature T0 set inside the first temperature band W (step S6 in FIG. 12, times t1 to t4 in FIG. 13). As a result, the temperature in the fuel cell module 2 once reaches the target temperature T0 in the first temperature band W (time t4 in FIG. 13), so that the temperature in the fuel cell module 2 is in the first temperature band. It is less likely to change for a long time near the upper limit value Tb of W, and fuel waste can be suppressed. The second temperature control unit 110b performs control to maintain the detected temperature T once the detected temperature T reaches the target temperature T0 (step S4 in FIG. 12, time t4 in FIG. 13). For this reason, it is possible to avoid excessive overshoot and undershoot due to control aimed at convergence of the temperature to the target temperature T0, and to stabilize the temperature. In addition, when the temperature in the fuel cell module 2 deviates from the first temperature band W regardless of the control by the second temperature control means 110b, the control is switched to the control by the first temperature control means 110a (FIG. 12). Therefore, the temperature can be reliably returned to the target temperature T0.

  Further, according to the solid oxide fuel cell 1 of the present embodiment, when the detected temperature T deviates from the first temperature band W, the first temperature control unit 110a causes the detected temperature T to reach the target temperature T0. (Until time t4 in FIG. 13), the control by the second temperature control means 110b can be started from the target temperature T0 set to the optimum operating temperature of the fuel cell module.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, the first temperature control means 110a performs temperature control based on the deviation from the target temperature T0 (step S6 in FIG. 12), so that the temperature T is the target. The fuel correction amount Q1, which is the operation amount, can be increased as the distance from the temperature T0 increases, and the temperature T can be reliably reached the target temperature T0. Further, since the second temperature control unit 110b performs temperature control based only on (TP-T) corresponding to the rate of change of the detected temperature per time, the operation amount becomes excessive and the control becomes unstable. Can be prevented.

  Further, according to the solid oxide fuel cell 1 of the present embodiment, the target temperature T0 is set to a temperature lower than the intermediate value of the first temperature band W. Even when the operating temperature of the fuel cell module 2 rises, the temperature in the fuel cell module 2 is unlikely to deviate from the first temperature band W, and stable temperature control can be performed for a long time.

  As mentioned above, although preferable embodiment of this invention was described, a various change can be added to embodiment mentioned above. In particular, in the above-described embodiment, the first temperature control by the first temperature control unit 110a has been executed until reaching the predetermined target temperature T0 that has substantially no width. The present invention can also be configured such that the first temperature control is continued until the temperature range is entered. In the modified example configured as described above, a narrower second temperature band W2 including the target temperature T0 is set inside the first temperature band W. When the detected temperature T deviates from the preset first temperature band W, the first temperature control means 110a is configured so that the detected temperature T enters the preset second temperature band W2. Control the temperature inside. The control by the first temperature control means 110a is switched to the control by the second temperature control means 110b when the detected temperature T enters the second temperature band W2, and the control by the second temperature control means 110b is controlled by the detected temperature. When T deviates from the first temperature band W1, the control is switched to the control by the first temperature control means 110a. According to the modified example configured as described above, switching from the first temperature control to the second temperature control can be reliably performed.

  In the above-described embodiment, proportional control using only the feedback gain K0 for proportional control is executed in the first temperature control, and only the feedback gain K1 for differential control is used in the second temperature control. Although differential control has been executed, as a modification, other controls such as proportional control, differential control, and integral control can be mixed in each temperature control. In this case, in the first temperature control, proportional control, integral control, or the like is performed so that the temperature deviated from the first temperature band W1 reaches the target temperature T0 or enters the second temperature band W2. Each feedback gain is set so that the operation amount (fuel correction amount Q1) based on it becomes dominant. Further, in the second temperature control, an operation amount (fuel correction amount Q1) based on differential control or the like that controls to reach the target temperature T0 or maintain the detected temperature T that enters the second temperature band W2 is dominant. Each feedback gain is set so that By configuring the first and second temperature controls as in the present modification, it is possible to smoothly transition between the first and second temperature controls.

  Furthermore, in the above-described embodiment, the first temperature band W1 and the target temperature T0 are set to constant values regardless of the generated power of the fuel cell module 2, but as a modification, these values are converted into the generated power. The present invention can be configured differently. That is, the temperature range in which the fuel cell module 2 can operate for each generated power is set as the first temperature band W for each generated power, and the optimum operation of the fuel cell module 2 for each generated power is set. The temperature is set for each generated power as the target temperature T0. Further, the first temperature control unit 110a and the second temperature control unit 110b are operated based on the first temperature band W and the target temperature T0 that change according to the generated power. According to the modified example configured as described above, the fuel cell module 2 can be operated in a more appropriate temperature range according to the generated power.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Fuel cell module 4 Auxiliary machine unit 7 Heat insulation material (heat storage material)
8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide fuel cell)
18 Combustion chamber (combustion section)
20 Reformer 22 Heat exchanger for air 24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit (water supply means)
30 Fuel supply source 38 Fuel flow rate adjustment unit (fuel supply means)
40 Air supply source 44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit (power generation oxidizing gas supply means)
46 1st heater 48 2nd heater 50 Hot water production device 52 Control box 54 Inverter 66 Manifold (distribution chamber)
76 Air introduction pipe 76a Air outlet 83 Ignition device 84 Fuel cell 110 Control section (control means)
110a First temperature control means 110b Second temperature control means 112 Operating device 114 Display device 116 Alarm device 126 Power state detection sensor (buy power detection means)
132 Fuel flow sensor (fuel supply detection sensor)
138 Pressure sensor (reformer pressure sensor)
140 Exhaust temperature sensor 142 Power generation chamber temperature sensor (temperature detection means)
148 Reformer Temperature Sensor 150 Outside Temperature Sensor

Claims (2)

A solid oxide fuel cell that generates variable generation power according to demand power,
A fuel cell module having a fuel cell stack; and
Fuel supply means for supplying fuel to the fuel cell module;
Power generation oxidant gas supply means for supplying power generation oxidant gas to the fuel cell module;
Temperature detecting means for detecting the temperature in the fuel cell module;
The fuel supply unit and the oxidant gas supply unit for power generation are controlled to generate electric power according to the demand power, and based on the detected temperature detected by the temperature detection unit, the temperature in the fuel cell module Control means for controlling
When the detected temperature deviates from the preset first temperature band, the control means causes the fuel so that the detected temperature enters the second temperature band preset inside the first temperature band. A first temperature control means for controlling the temperature in the battery module; and a second temperature controller for controlling the temperature in the fuel cell module to maintain the detected temperature once the detected temperature enters the second temperature band. Temperature control means, and
The control by the first temperature control means is switched to the control by the second temperature control means when the detected temperature enters the second temperature band, and the control by the second temperature control means When deviating from the first temperature band, the control is switched to the control by the first temperature control means ,
The second temperature band is set as a predetermined target temperature having substantially no width, and the first temperature control means is configured to deviate from the first temperature band in which the detected temperature is set in advance. , Control the temperature in the fuel cell module until the detected temperature reaches the target temperature,
The solid oxide fuel cell , wherein the target temperature is set to a temperature lower than an intermediate value of the first temperature range . The first temperature control means controls the temperature in the fuel cell module based on at least a deviation between the detected temperature and the target temperature, and the second temperature control means substantially detects the time of the detected temperature. based only on the rate of change per a solid oxide fuel cell according to claim 1, wherein for controlling the temperature in the fuel cell module.

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