JP5741803B2 - Solid oxide fuel cell device - Google Patents

Description

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

Conventionally, a solid oxide fuel cell device (SOFC) is in the start-up process, the fuel as engineering that inquire reforming in the reformer, i.e., water vapor reforming reaction process (SR process) through, the process proceeds to power step (For example, refer patent document 1).

In SOFC, by executing this process, it is possible to raise the temperature of the fuel cell module housing chamber disposed a reformer and a fuel cell stack, etc. to operating temperature. The operating temperature of the SOFC is 600 to 800 ° C. After the temperature of the fuel cell stack is raised to this temperature in the startup process, the power generation process is started.

JP 2004-319420 A

  However, when shifting from the start-up process to the power generation process, much of the fuel that was consumed exclusively to raise the temperature of the fuel cell stack or the like in the start-up process is consumed to generate electric power. Become. For this reason, at the time of transition from the start-up process to the power generation process, there is a problem that the operation state of the fuel cell module changes greatly, and the operation state tends to become unstable, such as a rapid temperature drop of the fuel cell stack. In particular, during the transition from the start-up process to the power generation process, the operating state changes greatly, so various control parameters referred to by the control unit to control the fuel cell module are likely to fluctuate, and this fluctuation causes an error in the control parameters. This also causes a problem that the control becomes unstable.

  Accordingly, an object of the present invention is to provide a solid oxide fuel cell that can smoothly transition from a startup process to a power generation process.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell device that generates electric power by reacting a fuel with an oxidant gas for power generation, and includes a plurality of solid oxide fuel cell cells. The fuel cell module provided, SR1 which is a reforming reaction for generating steam reforming, and reforming which generates hydrogen by generating SR2 which is a reforming reaction for steam reforming a smaller amount of fuel than SR1 , A fuel supply means for feeding fuel reformed by the reformer to the solid oxide fuel cell by supplying fuel to the reformer, and steam for reforming to the reformer and steam supply means, and generating oxidant gas supply means for supplying oxidant gas for power generation to the solid oxide fuel cell, a temperature detecting means for measuring the temperature of the fuel cell module, the fuel supply means, the water vapor The power supply means and the oxidant gas supply means for power generation can be controlled to generate the reforming reaction in the order of SR1 and SR2 in the reformer in the predetermined temperature band, and to take out the power from the fuel cell module. Control means configured to start a power generation process for extracting power from the fuel cell module after completing the start-up process while performing a start-up process of raising the temperature of the solid oxide fuel cell to a power generation start temperature. The control means maintains the fuel supply amount constant in SR2 during the start-up process, and is determined in advance even when the solid oxide fuel cell has reached the power generation start temperature. running time or SR2, the initial value of the predetermined control parameters used in the power generation process, measured by the temperature detecting means, during the transition time to electrical generation that is predetermined Kicking is characterized by calculating on the basis of transition temperature.

In the thus constructed present invention, the control means, fuel supply means, the water vapor supply means respectively controlled by the fuel, the water vapor is supplied to the reformer, in the reformer during the startup process , SR1, SR2 are sequentially generated to generate hydrogen. After the start-up process, the temperature of the solid oxide fuel cell provided in the fuel cell module rises to the power generation start temperature, and then a power generation process for extracting power from the fuel cell module is started. The control means maintains the fuel supply amount constant in SR2 during the starting process, and executes SR2 for a predetermined power generation transition time or more even when the solid oxide fuel cell reaches the power generation start temperature. The control means calculates an initial value of a predetermined control parameter in the power generation process based on the transition of the control parameter during the SR2.

  In general, in a solid oxide fuel cell, the operation state tends to become unstable when shifting from the start-up process to the power generation process, and there is a risk that the fuel cell module will undergo a rapid temperature drop. According to the present invention, in SR2 during the starting process, the fuel supply amount is maintained constant, and SR2 is maintained for a predetermined power generation transition time or longer. Furthermore, the initial value of the predetermined control parameter in the power generation process is calculated based on the transition of the control parameter during the SR2. For this reason, the initial value of the control parameter at the start of the power generation process, which is likely to be unstable in the operating state, can be adjusted during the SR2 period when the operating state is very stable, thereby suppressing the risk of unstable control. can do. In addition, since the SR2 period for adjusting the initial value of the control parameter is maintained at least for the power generation transition time, the initial value calculated based on the transition of the control parameter during this period is highly reliable and the control is unstable. Can be further reduced. Furthermore, the SR2 period in which the initial values of the control parameters are adjusted is close to the operating conditions in the power generation process because the fuel supply amount is reduced compared to SR1. Therefore, the initial value of the control parameter calculated based on the transition of the SR2 period is in good agreement with the control parameter in the power generation process, and it is possible to shift to the power generation process more smoothly.

  In the present invention, preferably, when the temperature of the reformer exceeds a predetermined SR2 transition reformer temperature and the temperature of the solid oxide fuel cell exceeds a predetermined SR2 transition cell temperature, the control means SR1 When the reformer temperature exceeds the predetermined SR2 forced transition temperature, the solid oxide fuel cell temperature reaches SR2 before the temperature reaches the SR2 transition cell temperature. To migrate.

  According to the present invention configured as described above, when the reformer exceeds the SR2 forced transition temperature, the reformer is forcibly shifted to SR2. Therefore, the reformer is maintained by maintaining the SR2 period longer than the power generation transition time. It is possible to suppress an excessive increase in temperature. Moreover, it can suppress that an error generate | occur | produces in the initial value of the calculated control parameter, when temperature rises excessively.

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

In the present invention, preferably, the control means calculates an initial value of the control parameter by a moving average of the temperature during the power generation transition time .
According to the present invention configured as described above, since the moving average of the control parameter is calculated during the SR2 period in which the fuel supply amount is maintained constant, the noise mixed in the control parameter and the influence of disturbances can be reduced. It can be effectively removed and a reliable initial value can be obtained.

  In the present invention, preferably, it further includes a heat storage material for accumulating heat generated in the fuel cell module, and the control means integrates the temperature of the fuel cell module during the SR2 period to obtain the initial value of the control parameter. Estimate the amount of heat stored in the heat storage material.

  According to the present invention configured as described above, since the heat storage amount accumulated in the heat storage material is estimated as the initial value of the control parameter, it is possible to effectively use the heat storage in the power generation process. Moreover, since the heat storage amount with high reliability can be estimated, the risk of temperature drop due to the use of heat storage can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the solid oxide fuel cell which can transfer to a power generation process smoothly from a starting process can be provided.

1 is an overall configuration diagram showing a fuel cell device according to an embodiment of the present invention. It is front sectional drawing which shows the fuel cell module of the fuel cell apparatus by one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a fuel cell device by one embodiment of the present invention. It is a perspective view which shows the fuel cell stack of the fuel cell apparatus by one Embodiment of this invention. 1 is a block diagram showing a fuel cell device according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the stop of the fuel cell apparatus by one Embodiment of this invention. It is an operation | movement table of the starting process procedure of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of starting in case the fuel cell apparatus by one Embodiment of this invention is restarted. It is a graph which shows the relationship between the output electric current and fuel supply amount in the solid oxide fuel cell of 1st Embodiment of this invention. It is a graph which shows the relationship between the output electric current in the solid oxide fuel cell of 1st Embodiment of this invention, and the calorie | heat amount which generate | occur | produces with the supplied fuel. It is a heat storage amount estimation table used in order to estimate the heat amount stored in the heat insulating material in the solid oxide fuel cell according to the first embodiment of the present invention. 14 is a graph of the heat storage amount estimation table of FIG.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Next, the estimation of the amount of heat and the amount of stored heat supplied to the fuel cell module will be described with reference to FIGS.
FIG. 11 is a graph showing the relationship between the output current and the fuel supply amount in the solid oxide fuel cell 1 of the present embodiment. FIG. 12 is a graph showing the relationship between the output current in the solid oxide fuel cell 1 and the amount of heat generated by the supplied fuel.

  First, as shown by the solid line in FIG. 11, the solid oxide fuel cell 1 of the present embodiment is configured so that the output can be varied at 700 W (output current 7 A) or less, which is the rated output power, according to the demand power. Has been. The fuel supply amount (L / min) required to output the required power is set as a basic fuel supply table indicated by a solid line in FIG. The control unit 110 serving as the control means determines the fuel supply amount based on the basic fuel supply table in accordance with the demand power detected by the power state detection sensor 126 serving as the demand power detection means, and supplies the fuel based on this. It is configured to control the fuel flow rate adjusting unit 38 as a means.

  The amount of fuel required for power generation is proportional to the output power (output current), but as shown by the solid line in FIG. 11, the fuel supply amount set in the basic fuel supply table is not proportional to the output current. This is because if the fuel supply amount is reduced in proportion to the output power, the fuel cell unit 16 in the fuel cell module 2 cannot be maintained at a temperature at which power can be generated. For this reason, in the present embodiment, the basic fuel supply table is set to a fuel utilization rate of about 70% when the generated power is near the output current 7A, and is set to about 50% when the generated power is about 2A. Is set. In this way, the fuel utilization rate in the small power generation region is reduced, the fuel not used for power generation is burned and used to heat the reformer 20, etc., thereby suppressing the temperature drop of the fuel cell unit 16 In addition, the inside of the fuel cell module 2 is maintained at a temperature capable of generating power.

  However, since the fuel that does not contribute to power generation is increased by reducing the fuel utilization rate, the energy efficiency of the solid oxide fuel cell 1 in the small power generation region is reduced. In the solid oxide fuel cell 1 of the present embodiment, the fuel table changing means 110c (FIG. 6) built in the control unit 110 sets the fuel supply amount set in the basic fuel supply table according to a predetermined condition. By changing / correcting, the fuel supply amount is decreased as shown by an example in the broken line in FIG. 11, and the fuel utilization rate in the small power generation region is increased. Thereby, the energy efficiency of the solid oxide fuel cell 1 is improved.

  FIG. 12 is a graph schematically showing the relationship between the output current and the amount of heat of the supplied fuel when the fuel is supplied based on the basic fuel supply table in the solid oxide fuel cell 1 of the present embodiment. is there. As shown by the one-dot chain line in FIG. 12, the amount of heat necessary to make the fuel cell module 2 thermally independent and operate stably increases monotonically with an increase in output current. The graph shown by the solid line in FIG. 12 shows the amount of heat when fuel is supplied according to the basic fuel supply table. In the present embodiment, in a region lower than the output current 5A corresponding to the medium generated power, the required amount of heat indicated by the alternate long and short dash line and the amount of heat supplied based on the basic fuel supply table indicated by the solid line substantially coincide.

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

  This heat storage temperature Th is set to a temperature corresponding to 500 W (output current 5 A) that is larger than 350 W, which is the median value of 0 W to 700 W that is the generated power range. In the region where the output current is 5 A or less, the amount of heat supplied based on the basic fuel supply table is substantially the same as the minimum amount of heat necessary for heat self-sustainment (the amount of heat of the basic fuel supply table is slightly larger). Is set. For this reason, as shown by an example of the broken line in FIG. 12, when the fuel supply amount by the basic fuel supply table is corrected and the fuel supply amount is reduced, the heat amount necessary for thermal independence is insufficient.

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

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

Next, with reference to FIG.13 and FIG.14, estimation of the heat storage amount accumulate | stored in the heat insulating material 7 grade | etc., Is demonstrated concretely.
FIG. 13 is a heat storage amount estimation table used for estimating the amount of heat accumulated in the heat insulating material 7. FIG. 14 is a graph of the heat storage amount estimation table.

The estimation of the heat storage amount is executed by the heat storage amount estimation means 110a (FIG. 6) built in the control unit 110. The heat storage amount estimation means 110a starts estimation of the heat storage amount after time t ₂₉ (FIG. 10) when the fuel supply amount, the water supply amount, and the power generation air supply amount respectively reach predetermined flow rates in the “SR2” process. To do. That is, the heat storage amount estimation unit 110a determines the addition / subtraction value with reference to the heat storage amount estimation table shown in FIG. 13 based on the detected temperature Td of the power generation chamber temperature sensor 142 which is a temperature detection unit. The addition / subtraction values are determined at predetermined time intervals, and are sequentially integrated to calculate the integrated value Ni. In this embodiment, integration is performed once every 0.5 sec.

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

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

  As shown in FIG. 13, for example, when the detected temperature Td is 645 ° C., the addition / subtraction value is determined to be 1/50000. The determined addition / subtraction value is added to the integrated value Ni. Therefore, when the detected temperature Td is constant at 645 ° C., the value of 1/50000 is integrated once every 0.5 sec, and the integrated value Ni increases.

  As shown in FIGS. 13 and 14, in this embodiment, the integration is performed when the detected temperature Td is higher than 635 ° C., which is the changed reference temperature Tcr, and is subtracted when the detected temperature Td is lower. . That is, when the detected temperature Td is higher than the changed reference temperature Tcr, the amount of heat that can be used for improving the fuel utilization rate is accumulated in the heat insulating material 7 or the like, and when it is lower than the changed reference temperature Tcr, the heat insulating material 7 is used. The integrated value Ni is calculated assuming that the heat accumulated in etc. is taken away. In other words, the integrated value Ni corresponds to the time integration of the temperature deviation of the detected temperature Td with respect to the change reference temperature Tcr, and the heat storage amount is estimated based on the integrated value Ni.

  Further, as shown in FIGS. 13 and 14, when the detected temperature Td is lower than 580 ° C., the addition / subtraction value is determined to be 20/50000, and this value is subtracted from the integrated value Ni by the heat storage amount estimation means 110a. When the detected temperature Td is not less than 580 ° C. and less than 620 ° C., 10/50000 × (620−Td) / (620−580) is subtracted from the integrated value Ni. When the detected temperature Td is 620 ° C. or higher and lower than 630 ° C., 1 / 50,000 is subtracted from the integrated value Ni.

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

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

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

When the detected temperature Td is 632 ° C. or higher and lower than 638 ° C., the added value is set to 0 (no addition / subtraction is performed) regardless of the tendency of the detected temperature Td.
In the above-described embodiment, the addition / subtraction value is determined based on the detection temperature Td of the power generation chamber temperature sensor 142. However, the addition / subtraction value is determined based on the detection temperature of the reformer temperature sensor 148, and the amount of stored heat. Can also be estimated. In this case, the reformer temperature sensor 148 functions as temperature detection means.

Next, control of the fuel cell module 2 at the start of the power generation process will be described.
The heat storage amount estimation means 110a starts the addition of the addition / subtraction value determined as described above from the start of the SR2 process (time t _{29 in} FIG. 10) and performs the integration over at least a predetermined power generation transition time. After that, the process proceeds to the power generation process. In addition, the controller 110 determines that the excessive temperature rise determination unit 110b has caused an excessive temperature increase during the startup process, and if the amount of heat available in the heat insulating material 7 is accumulated, The power generation process is started with high-efficiency operation in which the amount of fuel supply is reduced compared to the case where there is no fuel supply. In the present embodiment, the excessive temperature rise determination unit 110b is configured to forcibly shift to the SR2 process when the reformer temperature exceeds the SR2 forced transition temperature during the startup process, or the reformer temperature is forcibly shifted to power generation. If it is forced to shift to the power generation process by exceeding the temperature, it is determined that there has been an excessive temperature rise. In addition, when the integrated value Ni calculated by the heat storage amount estimation unit 110a is not 0, it is determined that the heat amount usable in the heat insulating material 7 is accumulated.

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

  In high-efficiency operation, power generation is performed with a fuel smaller than the fuel supply amount set by the basic fuel supply table shown in FIG. 12, and the fuel utilization rate is improved. That is, in high-efficiency operation, a reduction correction that reduces the fuel supply amount determined by the basic fuel supply table in accordance with the demand power is executed. The correction amount for decreasing the fuel supply amount is determined according to the estimated heat amount, and the greater the integrated value Ni, the more significant reduction correction is performed. By this reduction correction, the amount of heat of the supplied fuel is less than the amount of heat necessary for the fuel cell module 2 to become self-sustaining, but the insufficient amount of heat is supplemented by the heat accumulated in the heat insulating material 7 and the like. By utilizing the heat accumulated in the heat insulating material 7 and the like, the overall energy efficiency of the solid oxide fuel cell 1 is improved and the temperature of the heat insulating material 7 and the like is lowered. The condition is resolved.

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

  Further, the control unit 110 controls the fuel cell module 2 so as to change the generated power within a predetermined power range according to the demand power. Regardless, the power generation process is started with the generated power below the intermediate band in the power range. In the SR2 process during the start-up process, the fuel supply amount is maintained at 2.3 (L / min), but this fuel supply amount corresponds to the generated power of about 500 W, which is an intermediate band within the power range. Is. When starting the power generation process with high-efficiency operation, the control unit 110 suppresses the generated power to the generated power in the intermediate band or less regardless of the demand power so that the fuel supply amount is reduced as compared with the SR2 process. In the present specification, the generated power in the intermediate band refers to generated power of about 20% to 70% of the rated output power.

  As shown in FIG. 11, in the high power generation band in the power range, the fuel utilization rate is high even in the basic fuel supply table, and there is little room for reducing fuel other than the portion used for power generation. For this reason, even if the fuel supply amount is corrected to decrease, the amount of heat accumulated in the heat insulating material 7 is not consumed much. Further, in the high power generation band, since the operating temperature of the fuel cell module 2 is high (FIG. 12), it is an operation state in which the amount of heat accumulated in the heat insulating material 7 is difficult to use. Therefore, when starting the power generation process with high efficiency operation, the control unit 110 suppresses the generated power to be equal to or lower than the intermediate band regardless of the demand power. With the generated power below the intermediate band, the fuel utilization rate in the basic fuel supply table is low, and the operating temperature of the fuel cell module 2 is relatively low. For this reason, the fuel supply amount can be corrected to be greatly reduced by high-efficiency operation, and the amount of heat stored in the heat insulating material 7 is easily consumed, so that the excessively high temperature state is quickly eliminated.

In general, in the solid oxide fuel cell 1, the operating state tends to become unstable when shifting from the startup process to the power generation process, and there is a risk that the fuel cell module 2 will undergo a rapid temperature drop. According to the solid oxide fuel cell 1 of the embodiment of the present invention, in the SR2 during the start-up process, the fuel supply amount is kept constant, and the SR2 is maintained for 2 minutes or more which is the power generation transition time (FIG. 10 t _{29 to} t ₃₀ ). Furthermore, the initial value of the heat storage amount when starting the power generation process is calculated based on the sum of the addition / subtraction values during the SR2 period. As described above, since the initial value is calculated based on the transition of the control parameter during the SR2, the initial value of the control parameter at the start of the power generation process in which the operation state is likely to become unstable is very stable in the operation state. Can be arranged during the SR2 period, and the risk of unstable control can be suppressed. In addition, since the SR2 period for adjusting the initial value of the control parameter is maintained at least for the power generation transition time, the initial value calculated based on the transition of the control parameter during this period is highly reliable and the control is unstable. Can be further reduced. Furthermore, the SR2 period in which the initial values of the control parameters are adjusted is close to the operating conditions in the power generation process because the fuel supply amount is reduced as compared with SR1. Therefore, the initial value of the control parameter calculated based on the transition of the SR2 period is in good agreement with the control parameter in the power generation process, and it is possible to shift to the power generation process more smoothly.

Further, according to the solid oxide fuel cell 1 of the present embodiment, when the reformer 20 exceeds 700 ° C. which is the SR2 forced transition temperature, it is forcibly shifted to SR2 (time t in FIG. 10). ₂₈ ) By maintaining the SR2 period for the power generation transition time or more, the temperature of the reformer 20 can be prevented from rising excessively. Moreover, it can suppress that an error generate | occur | produces in the initial value of the calculated control parameter, when temperature rises excessively.

Further, the solid oxide fuel cell 1 of this embodiment, during execution of SR2 because thereby generating a weak power (t ₂₈ ~t ₃₀ in FIG. 10), approximates the operating state during the startup process for power generation step And can move to the power generation process more smoothly.

Further, the solid oxide fuel cell 1 of this embodiment, in SR2 period fuel supply amount is maintained constant each part of the temperature and the (t ₂₈ ~t ₃₀ in FIG. 10), control of the flow rate, etc. Since the moving average of the parameters is calculated, it is possible to effectively remove the noise mixed in the control parameters and the influence of disturbance and obtain a highly reliable initial value.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, since the heat storage amount accumulated in the heat insulating material 7 is estimated as the initial value of the control parameter, it is possible to effectively use the heat storage in the power generation process. It becomes possible. Moreover, since the heat storage amount with high reliability can be estimated, the risk of temperature drop due to the use of heat storage can be suppressed.

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

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

Claims (5)

A solid oxide fuel cell device that generates electric power by reacting a fuel and an oxidant gas for power generation,
A fuel cell module comprising a plurality of solid oxide fuel cells,
A reformer that generates hydrogen by generating SR1 that is a reforming reaction that generates steam reforming, and SR2 that is a reforming reaction that steam reforms a smaller amount of fuel than SR1;
Fuel supply means for supplying fuel to the reformer by feeding the fuel reformed by the reformer to the solid oxide fuel cell;
Steam supply means for supplying steam for reforming to the reformer;
Power generation oxidant gas supply means for supplying power generation oxidant gas to the solid oxide fuel cell;
Temperature detecting means for measuring the temperature in the fuel cell module;
The fuel supply means, the water vapor supply means, and the power generation oxidant gas supply means are controlled to perform the reforming reaction in the order of SR1 and SR2 in the reformer in a predetermined temperature band. The start-up step is performed to raise the temperature of the solid oxide fuel cell to a power generation start temperature at which power can be extracted from the fuel cell module. On the other hand, after the start-up step is completed, the power from the fuel cell module is And a control means configured to initiate a power generation process for removing
In the SR2 during the start-up process, the control means maintains the fuel supply amount constant, and the power generation transition that is determined in advance even when the solid oxide fuel cell reaches the power generation start temperature. Execute SR2 for more than the time, and calculate the initial value of the predetermined control parameter used in the power generation process based on the temperature transition during the predetermined power generation transition time measured by the temperature detection means A solid oxide fuel cell device.   When the temperature of the reformer exceeds a predetermined SR2 transition reformer temperature and the temperature of the solid oxide fuel cell exceeds a predetermined SR2 transition cell temperature, the control means performs the SR1 to SR2 On the other hand, when the temperature of the reformer exceeds a predetermined SR2 forced transition temperature, before the temperature of the solid oxide fuel cell reaches the SR2 transition cell temperature, The solid oxide fuel cell device according to claim 1, which is shifted to SR2.   3. The solid oxide fuel cell apparatus according to claim 2, wherein the control means causes the fuel cell module to generate predetermined weak power while the SR2 is generated during the start-up process. The solid oxide fuel cell device according to claim 1, wherein the control means calculates an initial value of the control parameter by a moving average of temperature during the power generation transition time .   Furthermore, it has a heat storage material for accumulating the heat generated in the fuel cell module, and the control means integrates the temperature of the fuel cell module during the SR2 period, whereby the heat storage material is used as an initial value of the control parameter. The solid oxide fuel cell device according to claim 1, wherein the heat storage amount of the material is estimated.

Images