JP2004335166A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of making the temperature of each generating cell more uniform and improving power generating efficiency as a whole. <P>SOLUTION: The solid oxide fuel cell is provided with a fuel cell stack 3, a case 2 containing the fuel cell stack, and an exhaust means leading exhaust gas exhausted inside the case from the fuel cell stack outside the case. The exhaust means is provided with a first exhaust tube 22a exhausting the exhaust gas from a top part of the case, a second exhaust tube 22b exhausting the exhaust gas from a bottom part of the case, and an exhaust flow volume adjustment valve adjusting exhaust flow volumes of the first and the second exhaust tubes. The fuel cell stack has a first to third temperature sensors 30a, 30b, 30c set each for detecting temperatures at its top part, center part and lower end part, and a controller is provided at a given position of the cell for controlling the exhaust flow volume adjustment valve based on detection signals of these sensors. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell).
[0002]
[Prior art]
A solid oxide fuel cell with a stacked power generation cell in which a solid electrolyte layer composed of an oxide ion conductor is sandwiched between an air electrode layer and a fuel electrode layer has been developed as a third-generation fuel cell for power generation. I'm advancing. In the power generation cell, oxygen (air) as an oxidant gas is supplied to the air electrode side, and fuel gas (H ₂ , CH _4, etc.) is supplied to the fuel electrode side. Both the air electrode and the fuel electrode are porous so that oxygen and fuel gas can reach the interface with the solid electrolyte.
[0003]
Oxygen supplied to the air electrode side passes through pores in the air electrode layer and reaches near the interface with the solid electrolyte layer, where electrons are received from the air electrode and converted into oxide ions (O ²⁻ ). Ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode. The oxide ions that have reached the vicinity of the interface with the fuel electrode react with the fuel gas at this portion to generate a reaction product (H ₂ O or the like), and emit electrons to the fuel electrode. The electrons can be extracted to the outside as an electromotive force.
[0004]
Incidentally, the electrode reaction when hydrogen is used as the fuel is as follows.
Air electrode: 1/2 O ₂ + 2e ⁻ → O ^2-
Fuel electrode: _H ² + ^{O 2-} → H ₂ O + 2e ⁻
The whole: H ₂ + 1 / 2O ₂ → H ₂ O
[0005]
The solid electrolyte layer is a gas impermeable dense structure because it functions as a partition for preventing direct contact between fuel gas and air, as well as a moving medium for oxide ions. This solid electrolyte layer must be composed of a material that has high oxide ion conductivity, is chemically stable under the conditions from the oxidizing atmosphere on the air electrode side to the reducing atmosphere on the fuel electrode side, and is resistant to thermal shock. As a material satisfying such requirements, stabilized zirconia (YSZ) to which yttria is added is generally used.
[0006]
On the other hand, both the air electrode (cathode) layer and the fuel electrode (anode) layer, which are electrodes, need to be made of a material having high electron conductivity. Since the air electrode material must be chemically stable in a high-temperature oxidizing atmosphere of at least about 700 ° C., a metal is not suitable, and a perovskite-type oxide material having electron conductivity, specifically LaMnO 2 ₃ or LaCoO ₃ , or a solid solution in which part of La is replaced with Sr, Ca, or the like is generally used. The fuel electrode material is generally a metal such as Ni or Co, or a cermet such as Ni-YSZ or Co-YSZ.
[0007]
Solid oxide fuel cells include a high-temperature operation type that operates at a high temperature of about 1000 ° C. and a low-temperature operation type that operates at a low temperature of about 700 ° C. A low-temperature-operating solid oxide fuel cell is, for example, a thin-film stabilized zirconia (YSZ) to which yttria as an electrolyte is added is thinned to about 10 μm, thereby lowering the resistance of the electrolyte so that the fuel cell can be used at low temperatures. Use a solid electrolyte layer modified to generate electricity.
[0008]
In a high-temperature solid oxide fuel cell, a ceramic having electronic conductivity such as lanthanum chromite (LaCrO ₃ ) is used as a separator. In a low-temperature operating solid oxide fuel cell, a metal such as stainless steel is used. Materials can be used.
[0009]
In addition, three types of structures of a solid oxide fuel cell, a cylindrical type, a monolith type, and a flat plate type, have been proposed. Among these structures, a low-temperature-operating solid oxide fuel cell can use a metal separator, and therefore, a flat plate-type structure that can easily impart a shape to the metal separator is suitable.
[0010]
A stack of a flat plate type solid oxide fuel cell has a structure in which power generation cells, current collectors, and separators are alternately stacked. A pair of separators sandwich the power generation cell from both sides, one of which is in contact with the air electrode via the air electrode current collector, and the other is in contact with the fuel electrode via the fuel electrode current collector. A sponge-like porous material such as a Ni-based alloy can be used for the fuel electrode current collector, and a similar sponge-like porous material such as an Ag-based alloy can be used for the air electrode current collector. Can be. The sponge-like porous body has a current collecting function, a gas permeating function, a uniform gas diffusing function, a cushioning function, a thermal expansion difference absorbing function, and the like, and is therefore suitable as a multifunctional current collector material.
[0011]
The separator has a function of electrically connecting the power generation cells and supplying gas to the power generation cells. The fuel is introduced from the outer peripheral surface of the separator and discharged from the surface of the separator facing the fuel electrode layer. The separator has a passage and an oxidant passage for introducing air as an oxidant gas from the outer peripheral surface of the separator and discharging the air from the surface of the separator facing the air electrode layer.
[0012]
[Problems to be solved by the invention]
By the way, in the flat plate type solid oxide fuel cell, a temperature difference is likely to occur in the stacking direction of the power generation cells due to a difference in a heat radiation state of Joule heat generated by the power generation reaction, and FIG. As shown, the temperature at the center of the fuel cell stack tends to be the highest, and the temperature at the upper and lower ends tends to be lower. In addition, a temperature difference occurs between the upper and lower ends depending on the exhaust direction of the high-temperature gas generated by the power generation reaction.
[0013]
On the other hand, in the solid oxide fuel cell, since the power generation cells are in a state of being connected in series, the power generation performance is reduced by the power generation cell having the lowest temperature (that is, the power generation cell having a low current). As described above, if a temperature difference occurs in the stacking direction of the power generation cells as described above, there is a problem that the power generation efficiency is reduced as a whole.
[0014]
Therefore, in order to solve the above problem, for example, a method of improving the power generation performance by raising the temperature of the fuel cell stack as a whole and raising the temperature at both ends of the stack having a lower relative temperature is also considered. However, in the case of this method, the temperature of the central portion of the stack having a high relative temperature also rises and exceeds the temperature suitable for the power generation reaction, and on the contrary, the power generation efficiency may be reduced.
[0015]
The present invention has been made in view of such circumstances, and it is possible to further uniform the temperature of each power generation cell as compared with the conventional one, thereby improving the power generation efficiency as a whole. It is an object of the present invention to provide a solid oxide fuel cell capable of performing the following.
[0016]
[Means for Solving the Problems]
The invention according to claim 1 provides a fuel cell stack in which power generation cells and separators are alternately stacked, a housing for housing the fuel cell stack, and an inside of the fuel cell stack from outside the housing. A solid oxide including a fuel gas supply unit and an oxidant gas supply unit that respectively supply a fuel gas and an oxidant gas; and an exhaust unit that guides exhaust gas discharged from the fuel cell stack into the housing to the outside of the housing. In the fuel cell, the exhaust means includes a first exhaust pipe for exhausting the exhaust gas from the upper part of the housing to the outside of the housing, and a second exhaust pipe for exhausting the exhaust gas from the lower part of the housing to the outside of the housing. An exhaust pipe, and an exhaust flow rate adjusting valve for adjusting an exhaust flow rate of the first exhaust pipe and the second exhaust pipe. In the fuel cell stack, the temperatures of the upper end, the center, and the lower end are detected. First to third temperature sensors are respectively installed, and the first to third temperature sensors are provided with first and third temperature sensors for controlling the exhaust flow rate adjusting valve based on detection signals of the first to third temperature sensors. The control means is connected.
[0017]
According to a second aspect of the present invention, the first control means detects that the temperature of the upper portion of the fuel cell stack has decreased based on the detection signal of the first temperature sensor. In this case, the exhaust gas flow control valve is controlled to increase the amount of exhaust gas from the first exhaust pipe, while the temperature of the lower part of the fuel cell stack decreases based on the detection signal of the third temperature sensor. When it is detected that the exhaust gas flows from the second exhaust pipe, the exhaust gas flow control valve is controlled to increase the amount of exhaust gas from the second exhaust pipe.
[0018]
According to a third aspect of the present invention, in the solid oxide fuel cell according to the first or second aspect, the oxidant gas supply means includes an oxidant gas supply passage connected to an oxidant passage of each separator via a connection pipe. An oxidant manifold for supplying the oxidant gas, an oxidant gas preheating tube capable of inducing an oxidant gas to the oxidant gas manifold, and preheating the oxidant gas in the process, and a cooling oxidant gas to the oxidant gas preheating tube. And a cooling gas flow rate adjusting valve capable of adjusting the flow rate of the cooling oxidant gas flowing through the cooling pipe, and a fourth temperature sensor for detecting a temperature in the oxidant manifold. Second control means for controlling the cooling gas flow rate adjusting valve based on the detection signal from the sensor and the detection signals from the first to third temperature sensors is connected to the fourth temperature sensor. The one in which the features.
[0019]
According to a fourth aspect of the present invention, the second control means according to the third aspect of the invention controls the temperature inside the fuel cell stack based on a detection signal from the first to third temperature sensors to generate a power generation reaction. When it is detected that the temperature is lower than the lower limit of the predetermined temperature range, the cooling gas flow control valve is controlled based on the detection signal from the fourth temperature sensor, and the cooling oxidant from the cooling pipe is controlled. While detecting that the temperature inside the fuel cell stack is higher than the upper limit of the predetermined temperature range while reducing the gas supply flow rate, the cooling gas is detected based on a detection signal from the fourth temperature sensor. The flow control valve is controlled to increase the supply flow rate of the cooling oxidant gas from the cooling pipe.
[0020]
According to the first aspect of the present invention, the first to third temperature sensors for detecting the temperatures of the upper end, the center, and the lower end of the fuel cell stack, and the exhaust flow rate adjusting valve based on the detection signals of these temperature sensors. And the first control means for controlling the temperature of the fuel cell stack, it is possible to arbitrarily adjust the flow rate of the gas exhausted from the upper and lower portions of the housing while monitoring the temperatures of the upper end portion, the central portion, and the lower end portion of the fuel cell stack. Therefore, the temperature of the fuel cell stack can be easily controlled.
[0021]
That is, when the temperature of the upper part of the fuel cell stack is detected to be low based on the detection signal of the first temperature sensor, the exhaust flow control valve is controlled. Controlling the exhaust flow control valve when it detects that the temperature at the lower part of the fuel cell stack has decreased based on the detection signal of the third temperature sensor while increasing the exhaust amount from the first exhaust pipe. If control is performed to increase the amount of exhaust from the second exhaust pipe, the temperature difference between the upper part and the lower part of the fuel cell stack can be eliminated. Further, when it is detected based on the detection signals of the first to third temperature sensors that the temperature of the central portion of the fuel cell stack is rising, the exhaust gas flow control valve is controlled to control the first exhaust pipe and the second exhaust pipe. If control is performed to increase both the displacements from the two exhaust pipes, it is possible to reduce the variation in the temperature in the fuel cell stack in the stacking direction (vertical direction) of the power generation cells. Therefore, the temperature of each power generation cell can be made more uniform as compared with the conventional power generation cell, whereby the power generation efficiency as a whole can be improved.
[0022]
According to the third aspect of the present invention, the fourth temperature sensor for detecting the temperature in the oxidant manifold and the cooling gas flow control valve are controlled based on the detection signals from the first to fourth temperature sensors. And the second control means for monitoring the temperature of the upper end, the center, and the lower end of the fuel cell stack, and the temperature in the oxidant manifold. The temperature of the supplied oxidizing gas can be adjusted arbitrarily.
[0023]
That is, as in the invention according to claim 4, based on the detection signals from the first to third temperature sensors, the temperature inside the fuel cell stack falls below the lower limit T1 of the predetermined temperature range suitable for the power generation reaction. When it is detected that the cooling gas flow control valve is controlled based on the detection signal from the fourth temperature sensor to decrease the supply flow rate of the cooling oxidant gas from the cooling pipe, When it is detected that the temperature exceeds the upper limit T2 of the predetermined temperature range, the cooling gas flow control valve is controlled based on the detection signal from the fourth temperature sensor to control the cooling oxidant gas from the cooling pipe. If the control for increasing the supply flow rate of the fuel cell is performed, the temperature of the entire fuel cell stack can be maintained within a temperature range suitable for the power generation reaction. It is possible to avoid the deterioration of.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of the present invention. In the drawing, reference numeral 1 denotes a fuel cell (also referred to as a fuel cell module), 2 denotes a housing, and 3 denotes a vertical stacking direction. Fuel cell stack. The fuel cell stack 3 includes a power generation cell (power generation unit) 7 in which a fuel electrode layer 5 and an air electrode layer (oxidant electrode layer) 6 are arranged on both surfaces of a solid electrolyte layer 4, and a fuel electrode outside the fuel electrode layer 5. A current collector 8, an air electrode current collector (oxidant electrode current collector) 9 outside the air electrode layer 6, and separators outside the current collectors 8 and 9 (the uppermost and lowermost layers are ends. (Which are plates 10a and 10b) in this order.
[0025]
Here, the solid electrolyte layer 4 is made of stabilized zirconia (YSZ) to which yttria is added, and the fuel electrode layer 5 is made of a metal such as Ni or Co or a cermet such as Ni-YSZ or Co-YSZ. The electrode layer 6 is made of LaMnO ₃ , LaCoO _3, etc., the fuel electrode current collector 8 is made of a sponge-like porous sintered metal plate such as a Ni-based alloy, and the air electrode current collector 9 is made of an Ag-based alloy. The separator 10 is made of stainless steel or the like.
[0026]
Further, on the side of the fuel cell stack 3, a fuel manifold 13 for supplying a fuel gas through a connection pipe 11 to a fuel passage (not shown) of each separator 10 and an oxidizing agent passage (not shown) of each separator 10 are provided. An oxidant manifold 14 for supplying air as an oxidant gas through the connection pipe 12 is provided extending in the stacking direction of the power generation cells 7. Further, on the outer peripheral side of the manifolds 13 and 14, a fuel gas preheating pipe 15, an oxidizing gas preheating pipe 16 connected to each of the manifolds 13 and 14, and a preheating pipe 15 and 16 for preheating the fuel cell stack 3. A heater 20 is provided. The heater 20 and the preheating tubes 15 and 16 are housed inside the casing 2 of the fuel cell 1, and each of the preheating tubes 15 and 16 in the casing 2 is provided with an external fuel gas supply pipe 17 and an oxidizing agent. Gas supply pipes 18 are respectively connected.
[0027]
Further, a cooling pipe 27 for introducing a cooling oxidizing gas (air at room temperature) is connected to the oxidizing gas preheating pipe 16, and the cooling pipe 27 is used for adjusting a flow rate of the cooling oxidizing gas. A cooling gas flow control valve 28 is provided. The oxidizing gas is supplied from outside the housing 2 to the inside of the fuel cell stack 3 by the oxidizing gas preheating pipe 16, the cooling pipe 27, the cooling gas flow control valve 28, the oxidizing manifold 14, the oxidizing gas supply pipe 18, and the like. The fuel gas preheating pipe 15, the fuel manifold 13, the fuel gas supply pipe 17 and the like constitute a fuel gas supply means for supplying a fuel gas into the fuel cell stack 3. ing.
[0028]
The casing 2 also includes a first exhaust pipe 22a that takes in exhaust gas discharged from the fuel cell stack 3 into the casing 2 through an upper opening 23a on the inner periphery of the casing and exhausts the exhaust gas to the outside of the casing. A second exhaust pipe 22b that takes in air from the lower opening 23b and exhausts the air to the outside of the housing is provided. The first exhaust pipe 22a and the second exhaust pipe 22b are provided with exhaust flow rate adjusting valves (not shown) capable of adjusting the respective exhaust flow rates. The exhaust flow rate adjustment valve may be provided in each of the first exhaust pipe 22a and the second exhaust pipe 22b, or may be provided only in the first exhaust pipe 22a. That is, in the first exhaust pipe 22a, the above exhaust gas in the housing 2 can be efficiently exhausted by using the rising airflow formed by the temperature increase in the housing 2, so that the first exhaust As long as the exhaust flow rate of the pipe 22a is adjusted, the exhaust flow rate of the second exhaust pipe 22b can be adjusted as a result. For this reason, it is possible to omit the exhaust flow rate adjustment valve for the second exhaust pipe 22b. The first exhaust pipe 22a, the second exhaust pipe 22b, the exhaust flow rate adjusting valve, and the like constitute an exhaust unit that guides the exhaust gas to the outside of the housing 2.
[0029]
Further, the fuel cell 1 has a sealless structure in which a gas leakage prevention seal is not intentionally provided on the outer peripheral portion of the power generation cell 7, so that the fuel supplied from the substantially central portion of the separator 10 toward the power generation cell 7 during operation is provided. The gas and the oxidizing gas (air) are spread in a good distribution over the entire surface of the fuel electrode layer 5 and the air electrode layer 6 while diffusing in the outer peripheral direction of the power generation cell 7 to generate a power generation reaction and consume the power generation reaction. The remaining gas that has not been removed is freely discharged from the outer peripheral portion of the power generation cell 7 to the outside. In other words, the fuel gas and the oxidizing gas flow so as to diffuse from the substantially central portion of the power generation cell 7 toward the outer periphery, reach the interface with the solid electrolyte layer 4 and cause an electrochemical reaction, and are not used for power generation. The surplus gas is discharged to the outside from the outer peripheral portion of the power generation cell 7 as it is.
[0030]
Further, the fuel cell stack 3 is provided with first to third temperature sensors 30a, 30b, 30c for detecting the temperatures at the upper end, the center, and the lower end, respectively. That is, the first temperature sensor 30a is provided on the end plate 10a located at the upper end of the fuel cell stack 3, and the third temperature sensor 30c is provided on the end plate 10b located at the lower end. The second temperature sensors 30b are respectively attached. Further, the oxidant manifold 14 is provided with a fourth temperature sensor 30d for detecting the internal temperature.
[0031]
The detection signals from the temperature sensors 30a, 30b, 30c, 30d are output to a controller (not shown). The controller includes a CPU, a RAM, a storage device, an input device, and the like. The storage device stores temperature data obtained from each of the temperature sensors 30a, 30b, 30c, and 30d, and various types of determination used for a temperature control process described later. A storage area for storing data and the like is provided. This controller constitutes the first control means and the second control means according to the present invention, and controls the exhaust flow rate control valve based on detection signals from the first to third temperature sensors 30a, 30b, 30c. At the same time, the cooling gas flow control valve 28 is controlled based on detection signals from the first to fourth temperature sensors 30a, 30b, 30c, 30d.
[0032]
Next, an embodiment of a temperature control method for a solid oxide fuel cell having the above-described configuration will be described.
First, in a first step, detection signals from each of the temperature sensors 30a, 30b, 30c are input based on an instruction input from an input device or based on an interrupt signal or the like generated at predetermined time intervals. Based on the signal, a temperature difference between each part (upper end, center, lower end) of the fuel cell stack 3 is derived by calculation, and the calculation result is set to a predetermined allowable range of the temperature difference (for example, within ± 25 ° C.). ) Is determined.
[0033]
As a result of the determination, if the value falls within the allowable range, the process proceeds to the next second step. If the value does not fall within the allowable range, the exhaust flow rate adjustment valve is controlled to control the first exhaust pipe 22a and the second exhaust port. The exhaust flow rate of the second exhaust pipe 22b is adjusted. Specifically, when detecting that the temperature of the upper part of the fuel cell stack 3 has decreased based on the detection signal of the first temperature sensor 30a, the exhaust gas flow control valve is controlled to control the first exhaust pipe. While detecting that the temperature of the lower part of the fuel cell stack 3 is decreasing based on the detection signal of the third temperature sensor 30c while increasing the exhaust gas from the fuel cell 22a, the exhaust gas flow control valve is controlled. Then, control is performed to increase the amount of exhaust from the second exhaust pipe 22b. When it is detected that the temperature at the center of the fuel cell stack 3 has risen based on the detection signals of the temperature sensors 30a, 30b and 30c, the exhaust gas flow control valve is controlled to Control is performed to increase both the amount of exhaust from the exhaust pipe 22a and the second exhaust pipe 22b.
[0034]
After a certain period of time, the detection signals from the temperature sensors 30a, 30b, and 30c are input again, and based on these detection signals, it is determined whether or not the temperature difference between the parts of the fuel cell stack 3 falls within the allowable range. It is determined, and as a result of the determination, if the value does not fall within the allowable range, the control in the first step described above is repeated, and if the value falls within the allowable range, the process proceeds to the second step.
[0035]
In the second step, detection signals from the first to third temperature sensors 30a, 30b, 30c are input, and based on these detection signals, the temperature of each part (upper end, center, lower end) of the fuel cell stack 3 is determined. However, as shown in FIG. 2, it is determined whether the temperature falls within a predetermined temperature range (for example, 700 to 750 ° C.) suitable for the power generation reaction.
[0036]
If the result of the determination is that the temperature falls within the predetermined temperature range, the temperature control process ends. On the other hand, when the temperature does not fall within the predetermined temperature range, the supply flow rate of the cooling oxidant gas is monitored while monitoring the temperatures of the upper end, the center, and the lower end of the fuel cell stack 3 and the temperature in the oxidant manifold 14. That is, the temperature of the oxidizing gas supplied to the fuel cell stack 3 is adjusted. Specifically, based on detection signals from the first to third temperature sensors 30a, 30b, 30c, the temperature of any part of the fuel cell stack 3 is lower than the lower limit T1 of the predetermined temperature range. When detecting that, the opening degree of the cooling gas flow control valve 28 is adjusted based on the detection signal from the fourth temperature sensor 30d, and the cooling oxidizing gas supplied from the cooling pipe 27 to the oxidizing gas preheating pipe 16 is cooled. Control is performed to reduce the flow rate. Conversely, when it is detected that the temperature of any part of the fuel cell stack 3 exceeds the upper limit T2 of the predetermined temperature range, the detection signal from the fourth temperature sensor 30d is output. The opening degree of the cooling gas flow control valve 28 is adjusted based on the control to increase the flow rate of the cooling oxidizing gas supplied from the cooling pipe 27 to the oxidizing gas preheating pipe 16.
[0037]
After a certain period of time, the detection signals from the temperature sensors 30a, 30b, and 30c are input again, and based on these detection signals, whether the temperature of each part of the fuel cell stack 3 falls within the above-mentioned predetermined temperature range is determined. If the result of this determination is that the temperature does not fall within the predetermined temperature range, the control in the second step described above is repeated, and if the temperature falls within the predetermined temperature range, the temperature control process ends. .
[0038]
As described above, according to the present embodiment, the first to third temperature sensors 30a, 30b, and 30c for detecting the temperatures of the upper end, the center, and the lower end of the fuel cell stack 3, and the temperature sensors 30a, 30b , A controller (first control means) for controlling the exhaust gas flow control valve based on the detection signal of the fuel cell stack 3, the temperature of the upper end, the center, and the lower end of the fuel cell stack 3 is monitored, The flow rate of the gas exhausted from the upper and lower portions of the body 2 can be arbitrarily adjusted, and the temperature of the fuel cell stack 3 can be easily controlled.
[0039]
That is, when it is detected based on the detection signal of the first temperature sensor 30a that the temperature of the upper part of the fuel cell stack 3 has decreased, the exhaust gas flow control valve is controlled to control the exhaust gas from the first exhaust pipe 22a. On the other hand, when it is detected that the temperature of the lower part of the fuel cell stack 3 is decreasing based on the detection signal of the third temperature sensor 30c, the exhaust gas flow control valve is controlled to control the second exhaust pipe. Since the control for increasing the displacement from the fuel cell 22b is performed, the temperature difference between the upper part and the lower part of the fuel cell stack 3 can be eliminated. When it is detected that the temperature at the center of the fuel cell stack 3 has risen based on the detection signals of the first to third temperature sensors 30a, 30b, 30c, the exhaust flow control valve is controlled. As a result, control is performed to increase both the amount of exhaust from the first exhaust pipe 22a and the amount of exhaust from the second exhaust pipe 22b, so that the temperature variation in the fuel cell stack 3 in the stacking direction (vertical direction) of the power generation cells 7 is reduced. can do.
[0040]
Therefore, the temperature of each power generation cell 7 can be made more uniform as compared with the conventional power generation cell, thereby making it possible to improve the power generation efficiency as a whole. When the temperature distribution of the fuel cell stack was actually measured, the temperature difference in the stack was 90 ° C. at the maximum in the conventional solid oxide fuel cell as shown in FIG. In the solid oxide fuel cell 1 of the present embodiment, as shown in FIG. 2, the temperature difference in the stack is only 40 ° C. at the maximum, and the variation width of the temperature of each power generation cell 7 is reduced to 従 来 or less of the conventional value. It was confirmed that it could be improved.
[0041]
Further, according to the present embodiment, the fourth temperature sensor 30d for detecting the temperature in the oxidant manifold 14, and the cooling gas based on the detection signals from the first to fourth temperature sensors 30a, 30b, 30c, 30d. By providing a controller (second control means) for controlling the flow control valve 28, the temperature of the upper end, the center, and the lower end of the fuel cell stack 3 and the temperature in the oxidant manifold 14 are monitored while monitoring the temperature. The supply flow rate of the cooling oxidizing gas, that is, the temperature of the oxidizing gas supplied to the fuel cell stack 3 can be arbitrarily adjusted.
[0042]
That is, based on the detection signals from the first to third temperature sensors 30a, 30b, 30c, it is detected that the temperature inside the fuel cell stack 3 is lower than the lower limit T1 of the predetermined temperature range suitable for the power generation reaction. In this case, the cooling gas flow rate adjusting valve 28 is controlled based on the detection signal from the fourth temperature sensor 30 d to reduce the supply flow rate of the cooling oxidant gas from the cooling pipe 27, while maintaining the temperature inside the fuel cell stack 3. However, when it is detected that the temperature exceeds the upper limit T2 of the predetermined temperature range, the cooling gas flow control valve 28 is controlled based on the detection signal from the fourth temperature sensor 30d, and the cooling oxidation from the cooling pipe 27 is performed. Since the control for increasing the supply flow rate of the agent gas is performed, the temperature of the entire fuel cell stack 3 can be maintained within a predetermined temperature range suitable for the power generation reaction. It is possible to avoid a decrease in power generation efficiency due departing from degrees range.
[0043]
In the present embodiment, the temperature sensors 30a, 30b, and 30c are exemplified as temperature sensors for detecting the temperatures of the upper end, the center, and the lower end of the fuel cell stack 3, and the internal temperature of the oxidant manifold 14 is measured. The temperature sensor 30d is exemplified as a temperature sensor for detecting the temperature, but the present invention is not limited to this, and the mounting position and quantity of each temperature sensor are determined according to the number of stacked power generation cells 7 and the cross-sectional area. It can be changed as appropriate. For example, a temperature sensor may be provided for all the separators 10, or a plurality of temperature sensors may be provided for each of the separators 10 and the oxidant manifold 14. Further, the number of the first exhaust pipe 22a and the second exhaust pipe 22b is not limited to one, and a plurality of each may be provided.
[0044]
【The invention's effect】
As described above, according to the present invention, the temperature of each power generation cell can be made more uniform, and the temperature of each power generation cell can be maintained within a desired temperature range suitable for a power generation reaction. Therefore, the power generation efficiency can be greatly improved as a whole.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one embodiment of a solid oxide fuel cell according to the present invention.
FIG. 2 is a graph showing a temperature distribution of the fuel cell stack of FIG.
FIG. 3 is a graph showing a temperature distribution of a fuel cell stack provided in a conventional solid oxide fuel cell.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 solid oxide fuel cell 2 housing 3 fuel cell stack 7 power generation cell 10 separator 13 fuel manifold (fuel gas supply means)
14. Manifold for oxidant (oxidant gas supply means)
15 Fuel gas preheating tube (fuel gas supply means)
16 Oxidizing gas preheating tube (oxidizing gas supply means)
17 Fuel gas supply pipe (fuel gas supply means)
18 Oxidant gas supply pipe (oxidant gas supply means)
22a first exhaust pipe (exhaust means)
22b second exhaust pipe (exhaust means)
27 cooling pipe (oxidant gas supply means)
28 cooling gas flow control valves 30a, 30b, 30c, 30d (first to fourth temperature sensors)

Claims (4)

A fuel cell stack in which power generation cells and separators are alternately stacked, a housing for accommodating the fuel cell stack, and a fuel gas and an oxidizing gas from the outside of the housing to the inside of the fuel cell stack, respectively. A solid oxide fuel cell comprising: a fuel gas supply unit and an oxidant gas supply unit; and an exhaust unit that guides an exhaust gas discharged from the fuel cell stack into the housing to the outside of the housing.
A first exhaust pipe that exhausts the exhaust gas from the upper part of the housing to the outside of the housing, a second exhaust pipe that exhausts the exhaust gas from the lower part of the housing to the outside of the housing, An exhaust flow rate adjusting valve that adjusts an exhaust flow rate of the first exhaust pipe and the second exhaust pipe,
In the fuel cell stack, first to third temperature sensors for detecting the temperatures of the upper end portion, the center portion, and the lower end portion are provided, respectively. A solid oxide fuel cell, wherein first control means for controlling the exhaust flow control valve based on a detection signal of a third temperature sensor is connected. The first control means controls the exhaust gas flow control valve when detecting that the temperature of the upper part of the fuel cell stack has decreased based on the detection signal of the first temperature sensor. While increasing the amount of exhaust gas from the exhaust pipe, when detecting that the temperature of the lower part of the fuel cell stack has decreased based on the detection signal of the third temperature sensor, controlling the exhaust flow control valve. 3. The solid oxide fuel cell according to claim 2, wherein control is performed to increase the amount of exhaust from the second exhaust pipe. The oxidant gas supply means includes an oxidant manifold for supplying an oxidant gas to the oxidant passage of each separator through a connection pipe, and an oxidant gas introduced into the oxidant manifold. An oxidizing gas preheating tube capable of preheating gas, a cooling tube capable of supplying a cooling oxidizing gas to the oxidizing gas preheating tube, and a cooling gas flow rate capable of adjusting a flow rate of the cooling oxidizing gas flowing through the cooling tube An adjustment valve, and a fourth temperature sensor for detecting a temperature in the oxidant manifold,
Second control means for controlling the cooling gas flow control valve based on the detection signal from the fourth temperature sensor and the detection signals from the first to third temperature sensors is connected to the fourth temperature sensor. The solid oxide fuel cell according to claim 1, wherein: The second control means detects that the temperature inside the fuel cell stack is lower than a lower limit of a predetermined temperature range suitable for a power generation reaction, based on detection signals from the first to third temperature sensors. In this case, the cooling gas flow control valve is controlled based on the detection signal from the fourth temperature sensor to decrease the supply flow rate of the cooling oxidant gas from the cooling pipe, while controlling the temperature inside the fuel cell stack. When it is detected that the temperature exceeds the upper limit of the predetermined temperature range, the cooling gas flow control valve is controlled based on a detection signal from the fourth temperature sensor, and the cooling oxidant from the cooling pipe is controlled. The solid oxide fuel cell according to claim 3, wherein control is performed to increase a gas supply flow rate.

Images