JP5585931B2 - 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 power according to required power.

In recent years, as a next-generation energy, a fuel cell device provided with a fuel cell that can generate electric power using fuel (hydrogen gas) and air and auxiliary equipment for operating the fuel cell Various proposals have been made.
Japanese Unexamined Patent Publication No. 7-307163 (Patent Document 1) describes a fuel cell power generator. This fuel cell is configured such that the electric power to be generated is changed according to the load.

  Here, a power supply system using a fuel cell will be described with reference to FIG. FIG. 11 shows an example of a conventional system for supplying power to a house using a fuel cell. In this system, the power consumed in the house 200 is covered by the fuel cell 202 and the system power 204. Normally, the maximum power consumption consumed in a house is larger than the maximum rated power that can be generated by the fuel cell 202. Therefore, even in the house 200 that uses the fuel cell 202, the shortage is compensated for by the grid power 204. Is supplied with power from the fuel cell 202 and the system power 204. Furthermore, in order to prevent the power generated by the fuel cell 202 from flowing backward to the grid power 204, generally, even when the power consumption in the house is lower than the maximum rated power of the fuel cell 202, Is supplied from the system power 204.

  The system power 204 is supplied by reducing the voltage of the power sent from the transmission line via the current transformer 206. The fuel cell 202 acquires a monitor signal of the power consumed by the house 200 from the current transformer 206, and changes the power generated by the fuel cell 202 based on the monitor signal. That is, the fuel cell 202 determines a command current Ii that indicates the current to be supplied by the fuel cell 202 based on the monitor signal acquired from the current transformer 206, and generates the command current Ii so that the command current Ii can be generated. The supply amount and the like are controlled. Further, the command current Ii is set to a value corresponding to the maximum rated power of the fuel cell 202 regardless of the power consumption of the house 200.

  Since the fuel cell module 208 built in the fuel cell 202 is generally very slow in response, it is difficult to change the generated power following the change in power consumption in the house 200. For this reason, the signal of the command current Ii instructing the amount of power generation to the fuel cell module 208 is determined by applying the filter 210 to the monitor signal so as to change very slowly compared to the change in power consumption.

  The fuel cell 202 supplies an amount of fuel corresponding to the command current Ii to the fuel cell module 208 so that the fuel cell module 208 has a capability of generating a current of the command current Ii. On the other hand, the inverter 212 takes out the direct current Ic from the fuel cell module 208, converts it into alternating current, and supplies it to the house 200. Further, the current Ic that the inverter 212 takes out from the fuel cell module 208 is always set to be equal to or less than the value of the command current Ii so as not to exceed the power generation capability of the fuel cell module 208. When a current exceeding the power generation capacity corresponding to the fuel supply amount determined based on the command current Ii is taken out from the fuel cell module 208, fuel depletion occurs in the fuel cell in the fuel cell module 208. There is a risk of significantly shortening the life or destroying the fuel cell.

  On the other hand, since the electric power consumed in the house 200 fluctuates rapidly, the electric power consumed in the house 200 becomes lower than the electric power corresponding to the command current Ii that changes slowly when the electric power consumption rapidly decreases. In such a state, the fuel Ic is supplied in accordance with the command current Ii, and the current Ic that the inverter 212 extracts from the fuel cell module 208 even though the fuel cell module 208 has a capability of generating a sufficient current. Is much smaller than the command current Ii.

  In the fuel cell power generator described in Japanese Patent Application Laid-Open No. 7-307163, a delay setter is provided in consideration of a time delay until the supplied fuel reaches the fuel cell through the reformer or the like, and a fuel cell The timing for extracting current from the module is delayed, thereby preventing fuel depletion.

JP-A-7-307163

  However, in the fuel cell power generation device described in Japanese Patent Application Laid-Open No. 7-307163, although problems such as fuel exhaustion can be avoided, when the consumed power is drastically reduced, the fuel cell power supply is supplied to the fuel cell module. The fuel that is used is excessive with respect to the current that is taken out, and there is a problem that the power generation efficiency of the entire fuel cell is lowered.

  Accordingly, an object of the present invention is to provide a solid oxide fuel cell capable of obtaining good power generation efficiency while avoiding problems such as fuel exhaustion.

In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates variable power according to required power, a fuel cell module that generates power using supplied fuel, and a fuel cell module An inverter that extracts current and converts it into alternating current, a fuel supply means that supplies fuel to the fuel cell module, a command current setting means that sets a command current in response to a change in the required power, and a change in the required power Inverter control that responds to the required power with higher followability than the command current and determines the actual power generation current so that the value is equal to or less than the command current and controls the inverter so that the actual power generation current is taken out from the fuel cell module and means, based on the actual generated current, so that the difference of the command current and the actual generated current is reduced to a predetermined deviation current, corrects the command current in the decreasing direction A decree current correcting means, the corrected command current capable of generating a fuel to be supplied to the fuel cell module is characterized by having a fuel control means for controlling the fuel supply means.

  In the present invention configured as described above, the command current setting means sets the command current in response to a change in the required power. The inverter control means determines the actual power generation current so that it responds to the required power with higher followability than the command current with respect to the change in the required power and becomes a value equal to or less than the command current. The inverter is controlled so as to be taken out from the battery module. Further, the command current correction means corrects the command current in the decreasing direction so that the difference between the command current and the actual power generation current is reduced based on the actual power generation current. The fuel control means controls the fuel supply means so that fuel capable of generating the corrected command current is supplied to the fuel cell module. The fuel cell module generates power using the supplied fuel, and the inverter extracts current from the fuel cell module and converts it into alternating current.

  According to the present invention configured as described above, the command current setting means sets the command current in response to the change in the required power, and the response is the response of the actual generated current set by the inverter control means. It is lower than gender. As a result, the amount of fuel supplied to the fuel cell module does not change excessively according to the change in the required power, so the fuel cell module can be used when an unnecessary temperature drop or an increase in output is desired. The problem that the temperature rise of the module is delayed and sufficient power cannot be supplied and the problem that the fuel cell module runs out of fuel can be avoided. At the same time, the command current correction means corrects the command current in a decreasing direction based on the actual generated current having higher responsiveness than the command current. For this reason, the difference between the command current and the actual power generation current that is always set to a value equal to or less than the command current is reduced, unnecessary fuel consumption can be suppressed, energy saving can be achieved, and the solid oxide fuel cell Overall efficiency can be improved.

In the present invention, preferably, the command current correcting means increases the command current when the difference between the command current and the actual generated current becomes smaller than a predetermined deviation current.
According to the present invention configured as described above, the command current correcting means increases the command current when the difference between the command current and the actual generated current becomes smaller than the predetermined deviation current, so that the output power is increased again. In this case, it is possible to prevent the temperature rise of the fuel cell module from being delayed and the response to the increase in required power from being greatly delayed.

In the present invention, preferably, the command current correction means changes the predetermined deviation current according to the operating state of the fuel cell module.
According to the present invention configured as described above, since the value of the deviation current is changed according to the operation state of the fuel cell module, an appropriate deviation current can be set in various aspects of operation. As a result, energy consumption is reduced by reducing the deviation current, and when the required power rises, the fuel cell module follows the required power relatively quickly and suppresses system power consumption. It is possible to achieve both energy saving effects.

In the present invention, preferably, the command current correction means decreases the predetermined deviation current as the command current is smaller.
According to the present invention configured as described above, since the deviation current is reduced as the command current is reduced, the temperature of the fuel cell module is low, and the fuel is required to maintain the temperature. Further reduction in operating efficiency in the state can be prevented.

In the present invention, it is preferable that the command current correction unit increases the predetermined deviation current as the change in the required power is rapid.
According to the present invention configured as described above, since the deviation current increases when the change in the required power is abrupt, the temperature increase of the fuel cell module can be promoted during the increase of the required power. The battery module can follow the required power relatively quickly and suppress the consumption of system power.

  According to the solid oxide fuel cell of the present invention, power generation efficiency can be improved while avoiding problems such as fuel exhaustion.

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 a time chart which shows an example of an effect | action of the fuel cell apparatus by one Embodiment of this invention. It is a flowchart of the control performed by a control part. 1 shows an example of a conventional system for supplying power to a house using a fuel cell.

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

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

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant (air) ) And combusted to generate exhaust gas.
Further, a reformer 20 for reforming the fuel gas is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which a reforming reaction can be performed by the combustion heat of the residual gas. ing. Further, an air heat exchanger 22 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. The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the flow rate of air, and a power generation air flow rate adjusting unit. 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

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

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

  The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In 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 cross-sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolyte layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

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

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

  The electrolyte layer 94 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. A device 112, a display device 114 for displaying various data such as a power generation output value (wattage), and a notification device 116 for issuing an alarm (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

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

The power state detection sensor 126 is 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 (steam) supplied to the reformer 20.
The water level sensor 136 is for detecting the water level of the pure water tank 26.
The pressure sensor 138 is for detecting the pressure on the upstream side outside the reformer 20.
The exhaust temperature sensor 140 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  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, the operation of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a time chart showing an example of the operation of the solid oxide fuel cell 1 of the present embodiment. FIG. 10 is a flowchart of control executed by the control unit 110. The process shown in the flowchart of FIG. 10 is mainly executed by the command current setting unit 110a, the inverter control unit 110b, the command current correction unit 110c, and the fuel control unit 110d built in the control unit 110. Specifically, the command current setting unit 110a, the inverter control unit 110b, the command current correction unit 110c, and the fuel control unit 110d are based on a microprocessor built in the control unit 110, a memory, a program for operating these, and the like. Composed.

  First, the time chart shown in FIG. 9 represents the total demand power (required power) consumed by facilities such as houses in the first stage, and the power supplied by the solid oxide fuel cell 1 out of the total demand power, That is, the inverter output power output from the inverter 54 is represented in the second stage, the command current Ii is represented in the third stage, and the actual power generation current Ic that is the current drawn from the fuel cell module 2 to the inverter 54 is represented in the fourth stage. Represents.

  At times t0 to t1 in FIG. 9, the total demand power is generally increasing while including fine fluctuations, and accordingly, the inverter output power is gradually increasing. The power corresponding to the difference between the total demand power and the inverter output power at each time is supplied from the grid power. The total demand power consumed by the facility is input to the control unit 110 as a total demand power monitor signal Ms (FIG. 6). At times t0 to t1, the command current setting unit 110a increases the command current Ii so as to gently follow the increasing trend of the total demand power, and the inverter control unit 110b does not exceed the command current Ii. Thus, the actual power generation current Ic is gradually increased.

  Next, at time t1, the total demand power is rapidly decreasing for a short period. Accordingly, the inverter control means 110b sharply reduces the actual power generation current Ic extracted from the fuel cell module 2 to the inverter 54. The actual generated current Ic extracted by the inverter 54 is input to the control unit 110 as the actual generated current monitor signal Mic (FIG. 6). Further, the inverter output power output from the inverter 54 also changes in substantially the same manner as the actual power generation current Ic, but due to the action of a capacitor or the like built in the inverter 54, the fluctuation becomes slightly gentler than the actual power generation current Ic. Yes. After that, the inverter control unit 110b gradually increases the actual power generation current Ic following the increase in the total demand power (time t1 to t4). The followability of the actual generated current Ic with respect to the total demand power is set higher than the followability of the command current Ii with respect to the total demand power.

  On the other hand, the command current setting means 110a determines the command current Ii based on the total demand power. However, since the command current setting means 110a determines the command current Ii by largely smoothing the change in the total demand power, the short-term decrease in the total demand power at the time t1 is almost not in the setting of the command current Ii. There is no impact. For this reason, the command current Ii is set to increase monotonously (imaginary line in FIG. 9). In the conventional fuel cell, the value of the command current Ii determined in this way is used as it is, and the fuel supply amount to the fuel cell module 2 is determined based on this value.

  On the other hand, in the solid oxide fuel cell 1 of the present embodiment, the value of the command current Ii determined as described above is such that the difference between the command current Ii and the actual power generation current Ic is reduced. It is corrected in the decreasing direction by the command current correcting means 110c (broken line in FIG. 9). The fuel control means 110d determines the fuel supply amount based on the command current Ii corrected in this way, and controls the fuel flow rate adjustment unit 38 that is the fuel supply means.

Next, the operation of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described with reference to FIG.
First, in step S1, the total demand power is input to the command current setting means 110a as the total demand power monitor signal Ms. Next, in step S2, the command current setting means 110a determines the command current Ii based on the input total demand power. The command current setting means 110a determines the command current Ii so as to change very slowly by integration calculation of the total demand power input in the past. Further, the command current Ii is determined to be a value equal to or less than the maximum rated current of the fuel cell module 2.

  Next, in step S3, it is determined whether or not the power supplied from the grid power out of the total demand power is greater than or equal to a predetermined value. That is, the power output from the inverter 54 is set to be a value smaller than the total demand power by a predetermined power in order to prevent a reverse flow to the grid power. In step S3, it is determined whether or not a sufficient margin for the total demand power is secured. If the margin is not sufficient, the process proceeds to step S4.

  In step S4, it is determined whether or not the inverter output power does not exceed the total demand power due to a sudden drop in the total demand power or the like. If the inverter output power exceeds the total demand power, the process proceeds to step S5. In step S5, the inverter control means 110b reduces the actual power generation current Ic so as to avoid reverse power flow. Furthermore, in this case, since the power generated by the fuel cell module 2 is too large relative to the total demand power, the command current Ii is reduced to the actual power generation current Ic. On the other hand, if the inverter output power does not exceed the total demand power, the process proceeds to step S6, where the value of the command current Ii is maintained at the previous value.

  On the other hand, if it is determined in step S3 that a sufficient margin is secured, the process proceeds to step S7. In step S7, it is determined whether or not the actual power generation current Ic is equal to or greater than the command current Ii. If the actual power generation current Ic is greater than or equal to the command current Ii, the inverter 54 is taking out more current than the power generation capacity of the fuel cell module 2, and thus the process proceeds to step S13 and the command current Ii is increased.

  If it is determined in step S7 that the actual power generation current Ic is not equal to or greater than the command current Ii, the process proceeds to step S8. In step S8, the deviation current ΔY (which is the difference between the command current Ii and the actual power generation current Ic). = Ii-Ic) is calculated. The actual power generation current Ic is input to the command current correction unit 110c as the actual power generation current monitor signal Mic.

  Next, in step S9, it is determined whether or not the value of the deviation current ΔY is equal to or greater than a predetermined deviation current upper limit value Y1. If the deviation current ΔY is greater than or equal to the deviation current upper limit value Y1, the process proceeds to step S10. When the deviation current ΔY is greater than or equal to the deviation current upper limit value Y1 (time t1 in FIG. 9), the power generation capability of the fuel cell module 2 is too large compared to the actual power generation current Ic actually extracted from the fuel cell module 2. Therefore, in step S10, the command current correction unit 110c decreases the command current Ii by a predetermined current amount Δa. The current amount Δa is set to a value that does not cause a rapid temperature drop of the fuel cell module 2 due to a decrease in the command current Ii. While the deviation current ΔY is equal to or greater than the deviation current upper limit value Y1, the process of step S10 is performed every time the flowchart shown in FIG. 10 is executed, and the reduction state of the command current Ii continues (time in FIG. 9). t1-t2).

  Next, when the deviation current ΔY becomes smaller than the deviation current upper limit Y1 due to the decrease in the command current Ii and / or the increase in the actual power generation current Ic, the process proceeds from step S9 to step S11. In step S11, it is determined whether or not the value of the deviation current ΔY is equal to or greater than a predetermined deviation current lower limit value Y2. If the deviation current ΔY is smaller than the deviation current upper limit value Y1 and greater than or equal to the deviation current lower limit value Y2, the process proceeds to step S12. In step S12, the value of the command current Ii is maintained at the previous value. In this way, the command current correcting unit 110c acts so that the difference between the command current Ii and the actual power generation current Ic is reduced, and the predetermined deviation current (deviation current) is not reduced until the difference becomes zero. It acts so as to remain over the lower limit Y2). While the deviation current ΔY is not less than the deviation current lower limit value Y2 and less than the deviation current upper limit value Y1, the process of step S12 is performed every time the flowchart shown in FIG. 10 is executed, and the value of the command current Ii is constant. (Time t2 to t3 in FIG. 9).

  Further, when the deviation current ΔY becomes smaller than the deviation current lower limit value Y2 due to the increase in the actual power generation current Ic, the process proceeds from step S11 to step S13. In step S13, since the deviation current ΔY has become too small, the command current Ii is increased by a predetermined current amount Δa (after time t3 in FIG. 9). This amount of current Δa is set to a value that does not cause a rapid temperature rise of the fuel cell module 2 due to an increase in the command current Ii.

Thus, in the solid oxide fuel cell 1 of the present embodiment, the command current setting unit 110a sets the command current Ii based on the total demand power, and the command current correction unit 110c is based on the actual power generation current Ic. The command current Ii is corrected so that the difference between the command current Ii and the actual generated current Ic is reduced. Further, the command current correcting unit 110c decreases the difference between the command current Ii and the actual generated current Ic, but increases the command current Ii when the difference becomes smaller than the deviation current lower limit value Y2.

  According to the solid oxide fuel cell 1 of the embodiment of the present invention, as shown in FIG. 9, the command current setting means 110a sets the command current Ii in response to a change in the total demand power. Is lower than the responsiveness of the actual generated current Ic set by the inverter control means 110b. As a result, the amount of fuel supplied to the fuel cell module 2 is not sensitively changed in accordance with the change in the total demand power, so that an unnecessary temperature drop of the fuel cell module 2 or an increase in output is desired. In addition, the problem that the temperature rise of the fuel cell module 2 is delayed and sufficient power cannot be supplied, and the problem that the fuel cell module 2 runs out of fuel can be avoided. At the same time, the command current correction unit 110c corrects the command current Ii in a decreasing direction based on the actual power generation current Ic that has higher responsiveness than the command current Ii. For this reason, the difference between the actual power generation current Ic, which is always set to a value equal to or less than the command current, and the command current Ii is reduced, unnecessary fuel consumption can be suppressed, energy saving can be realized, and solid electrolyte fuel The overall efficiency of the battery 1 can be improved.

In addition, according to the solid oxide fuel cell 1 of the present embodiment, the command current correction unit 110c has a deviation current remaining between the command current Ii and the actual power generation current Ic (steps S11 to S13 in FIG. 10). Since the difference between the command current Ii and the actual power generation current Ic is reduced (steps S9 and S10 in FIG. 10), the temperature rise of the fuel cell module 2 is delayed when the output power is increased again, and the response to the increase in the total demand power Can be prevented from being significantly delayed.

  In the embodiment of the present invention described above, the value of the deviation current lower limit value Y2 is constant. However, as a modification, the value of the deviation current lower limit value Y2 is changed according to the operating state of the fuel cell module 2. You can also Preferably, when the command current Ii is small, the deviation current lower limit value Y2 is set small. Preferably, the value of the deviation current lower limit value Y2 is set to be large in a state where the total demand power is changing rapidly.

  According to the modification of the embodiment of the present invention configured as described above, the value of the deviation current lower limit value Y2 is changed according to the operation state of the fuel cell module 2, and therefore the command current Ii in various aspects of operation. And the actual generated current Ic can have an appropriate deviation. As a result, an energy saving effect that reduces unnecessary fuel consumption by reducing the deviation between the command current Ii and the actual power generation current Ic, and when the total demand power increases, the fuel cell module 2 relatively quickly The energy saving effect that suppresses the consumption of the system power can be achieved at the same time.

  Further, according to the above-described modification, the deviation current lower limit value Y2 is reduced as the command current Ii is smaller. Therefore, the fuel utilization rate at which the temperature of the fuel cell module 2 is low and fuel is required to maintain the temperature. It is possible to prevent further reduction in operating efficiency in the low operating state.

  Furthermore, according to the above-described modification, the deviation current lower limit value Y2 becomes large when the change in the total demand power is abrupt, so that the temperature increase of the fuel cell module 2 is promoted in the increase phase of the total demand power. Thus, the fuel cell module 2 can follow the total demand power relatively quickly, and the consumption of the system power can be suppressed.

DESCRIPTION OF SYMBOLS 1 Solid oxide type fuel cell 2 Fuel cell module 4 Auxiliary unit 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 20 Reformer 22 Air heat exchanger 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 (reforming air supply means)
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 110a Command current setting means 110b Inverter control means 110c Command current correction means 110d Fuel control means 112 Operation device 114 Display Device 116 Alarm device 126 Power state detection sensor 132 Fuel flow rate sensor (fuel supply amount detection sensor)
138 Pressure sensor (reformer pressure sensor)
142 Power generation chamber temperature sensor (temperature detection means)
150 Outside temperature sensor 200 House 202 Fuel cell 204 System power 206 Current transformer 208 Fuel cell module 210 Filter 212 Inverter

Claims (5)

A solid oxide fuel cell that generates variable power according to required power,
A fuel cell module for generating electricity from the supplied fuel;
An inverter that extracts current from the fuel cell module and converts it into alternating current;
Fuel supply means for supplying fuel to the fuel cell module;
Command current setting means for setting a command current in response to a change in the required power;
The actual power generation current is determined so as to respond to the required power with higher followability than the command current with respect to the change in the required power, and to be a value equal to or less than the command current. Inverter control means for controlling the inverter so as to be removed from the module;
Command current correction means for correcting the command current in a decreasing direction so that a difference between the command current and the actual power generation current is reduced to a predetermined deviation current based on the actual power generation current;
Fuel control means for controlling the fuel supply means so that fuel capable of generating the corrected command current is supplied to the fuel cell module;
A solid oxide fuel cell comprising: The command current correction means, when the difference between the command current and the actual generated current is smaller than the predetermined deviation current, solid oxide fuel cell according to claim 1, wherein increasing the command current.   3. The solid oxide fuel cell according to claim 2, wherein the command current correcting means changes the predetermined deviation current according to an operating state of the fuel cell module.   4. The solid oxide fuel cell according to claim 3, wherein the command current correcting means decreases the predetermined deviation current as the command current is smaller.   4. The solid oxide fuel cell according to claim 3, wherein the command current correcting means increases the predetermined deviation current as the change in the required power is abrupt.

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