JP2004335163A - Solid oxide type fuel cell and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable solid oxide type fuel cell capable of being efficiently preheated in a short time while preventing damage of a power generation cell and oxidation/ separation phenomena of a fuel electrode layer; and to provide its operation method. <P>SOLUTION: This solid oxide type fuel cell 1 is so structured that a fuel cell stack 3 composed by alternately stacking the power generation cells 7 and separators 10 is stored in a power generation reaction chamber 20; and a reacting gas is supplied into the cell stack 3 in operating it to generate a power generation reaction. The fuel cell is characterized by that a gas preheating chamber 30 equipped with a gas burner 21 is formed under the reaction chamber 20; and a preheating oxidizer gas passage 28 for introducing preheating air into the cell stack 3 in preheating it and a preheating fuel gas passage 27 for introducing a preheating gas are arranged in the preheating chamber 30. In addition, the fuel cell is characterized by disposing reform catalyst in the gas passage 27. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell, and more particularly, to a preheating structure and a preheating method for a solid oxide fuel cell.
[0002]
[Prior art]
A solid electrolyte fuel cell having a stacked power generation cell with a solid electrolyte layer composed of an oxide ion conductor sandwiched between an air electrode layer and a fuel electrode layer has been developed as a third-generation fuel cell for power generation. In. In the power generation cell, oxygen (air) as an oxidant gas is supplied to the air electrode side, and fuel gas (H ₂ , CO, etc.) is supplied to the fuel electrode side. Both the air electrode and the fuel electrode are porous so that the 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, CO _2, etc.), and emit electrons to the fuel electrode.
[0004]
The electrode reaction when hydrogen is used as the fuel is as follows.
Air electrode: 1/2 O ₂ + 2e ⁻ → O ²⁻
The fuel ^{_{electrode: H 2 + O 2- → H}} 2 O + 2e -
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]
The solid oxide fuel cell includes 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 operation type solid electrolyte fuel cell generates power as a fuel cell even at a low temperature, for example, by reducing the thickness of stabilized zirconia (YSZ) to which electrolyte yttria is added to about 10 μm to lower the electrolyte resistance. Use a solid electrolyte layer that has been modified to:
[0008]
In a high-temperature solid electrolyte fuel cell, for example, a ceramic having electronic conductivity such as lanthanum chromite (LaCrO ₃ ) is used as a separator. Can be used.
[0009]
Further, 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 in which the shape of the metal separator can be easily applied is suitable.
[0010]
The stack of the plate-stacked 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. It has a gas passage and an oxidant gas 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]
By the way, when operating the above-mentioned solid oxide fuel cell, it is necessary to start the operation after preheating the power generation cell to the above-mentioned power generation reaction temperature (see Patent Document 1). A method of increasing the temperature by a heater arranged on the outer periphery and a method of introducing a gas heated from the outside to the periphery of the fuel cell stack are adopted. In each of these methods, the power generation cell is heated from the outer peripheral portion.
[0013]
[Patent Document]
JP-A-6-124721
[Problems to be solved by the invention]
However, when preheating the power generation cells, unless the temperature is raised while maintaining the uniformity of the entire fuel cell stack, a temperature distribution is generated in the power generation cells and thermal stress is generated, which may lead to breakage of the power generation cells. For this reason, in the method of heating the power generation cell from the outer peripheral portion, it is difficult to maintain the uniform temperature, so that the temperature must be gradually increased over a very long time, and the standby time until the start of operation increases. There's a problem. Also, in the temperature lowering operation at the time of operation shutdown, if the temperature is lowered at once from the operating temperature, problems such as breakage of the power generation cell occur as in the case of temperature increase, so the process of gradually lowering the temperature while heating appropriately. Has passed.
[0015]
In addition, conventionally, since Ni is mainly used as a material of the fuel electrode layer, Ni of the fuel electrode layer is reduced by repeatedly performing a temperature raising operation at the time of starting and a temperature decreasing operation at the time of operation stop. There is a problem in that it is oxidized and peels off at the interface with the electrolyte layer due to sintering shrinkage due to reduction during power generation. Such a separation phenomenon of the fuel electrode layer loses the electrode activity, thereby deteriorating the power generation characteristics and significantly lowering the durability. For this reason, conventionally, in order to prevent oxidation of the Ni in the fuel electrode layer at the time of preheating, measures such introduced N ₂ or the like from an inert gas cylinder, raising the temperature while maintaining the reducing atmosphere of the fuel electrode side Has been taken.
[0016]
The present invention has been made in view of the above problems, and is a suitable solid oxide fuel that can efficiently perform preheating in a short time while preventing breakage of a power generation cell and oxidation of a fuel electrode. It is an object to provide a battery and a method for operating the battery.
[0017]
[Means for Solving the Problems]
That is, according to the present invention, a fuel cell stack formed by alternately stacking power generation cells and separators is housed in a power generation reaction chamber, and a reaction gas is supplied into the fuel cell stack during operation. A gas preheating chamber provided with a burner at a lower portion of the power generation reaction chamber, wherein a gas for preheating is supplied to the fuel cell stack when the temperature rises. A gas passage for preheating for introducing the gas is provided.
In the above configuration, the heating gas is introduced into the separator through the gas passage for preheating, and the heating gas exchanges heat while flowing through the inside of the separator to heat the separator from the inside. As the heating gas supplied to the air electrode side, air used as an oxidizing gas in a fuel cell reaction can be used. An inert gas or a reducing gas can be used on the fuel electrode side.
[0018]
According to a second aspect of the present invention, there is provided the solid oxide fuel cell according to the first aspect, wherein a preheating gas is introduced into the gas preheating chamber to introduce a preheating gas to the fuel cell stack when the temperature is raised. A fuel gas passage is provided, and a reforming catalyst is provided in the preheating fuel gas passage.
In the above configuration, the mixed gas of the hydrocarbon gas and the steam introduced into the fuel gas passage for preheating comes into contact with the reforming catalyst in the pipe to perform the reforming reaction of the hydrocarbon gas, and the reformed gas (H ₂ , CO, CO ₂ ). This reforming reaction is an endothermic reaction, and the heat required for the reforming reaction can use the combustion heat of the burner.
[0019]
According to a third aspect of the present invention, in the solid oxide fuel cell according to any one of the first and second aspects, the burner burns on a partition wall between the power generation reaction chamber and the gas preheating chamber. It is characterized by having a ventilation path for introducing gas into the power generation reaction chamber.
In the above configuration, at the time of temperature rise, hot air (combustion gas) generated by the burner combustion operation is introduced into the power generation reaction chamber through the ventilation path, and heats the fuel cell stack from the outside in the process of ascending the power generation reaction chamber.
[0020]
According to a fourth aspect of the present invention, in the solid oxide fuel cell according to the third aspect, a plurality of the ventilation paths are provided around the fuel cell stack.
In the above configuration, the fuel gas stack is uniformly heated over the entire area by the combustion gas introduced from the ventilation path.
[0021]
According to a fifth aspect of the present invention, there is provided the method for operating a solid oxide fuel cell according to any one of the first to fourth aspects, wherein the combustion operation of the burner is performed during preheating. Start and heat the preheating air in the preheating oxidant gas passage, supply it to the oxidant electrode layer of the power generation cell through the separator, and supply the mixed gas of steam and hydrocarbon gas to the preheating fuel gas passage. Introducing and generating a gas containing hydrogen less than the lower explosion limit by a reforming reaction and supplying the gas to the fuel electrode layer of the power generation cell through the separator, thereby heating the power generation cell from the inside and burning the burner It is characterized in that the power generation cell is externally heated by gas.
In the above operation method, the power generation cell can be heated from the outside and the inside in parallel when the temperature is raised, so that the temperature difference between the outer peripheral portion and the inside of the fuel cell stack is kept small while the temperature of the power generation cell is raised. Can be promoted. Therefore, it is possible to efficiently raise the temperature of the power generation cell in a short time while preventing the power generation cell from cracking. Further, during the heating, the reducing atmosphere is maintained by the hydrogen supplied to the fuel electrode layer side, so that the oxidation of Ni in the fuel electrode layer can be prevented.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the internal configuration of a solid oxide fuel cell of the present invention, FIG. 2 shows the configuration of a heat exchange pipe, and FIG. 3 shows the schematic configuration of a main part of a fuel cell stack.
[0023]
In FIG. 1, reference numeral 1 denotes a solid oxide fuel cell, reference numeral 2 denotes a housing provided with a heat insulating material 26 therein, and reference numeral 3 denotes a fuel cell stack disposed inside the housing 2 with the stacking direction being vertical. . As shown in FIG. 3, the fuel cell stack 3 includes a power generation cell 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 cell layer outside the fuel electrode layer 5. A structure in which a fuel electrode current collector 8, an air electrode current collector (oxidant electrode current collector) 9 outside the air electrode layer 6, and a separator 10 outside each current collector 8, 9 are sequentially stacked. Have.
[0024]
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.
[0025]
Further, on the side of the fuel cell stack 3, a fuel manifold 13 for supplying a fuel gas to the fuel gas passage 17 (see FIG. 3) of each separator 10 through the connection pipe 11, and an oxidizing gas passage 18 of each separator 10 An oxidant manifold 14 for supplying air as an oxidant gas through a connection pipe 12 (see FIG. 3) is provided extending in the stacking direction of the power generation cells 7.
[0026]
A fuel gas supply pipe 15 for supplying an external fuel gas required for power generation reaction during operation is provided substantially at the center of the fuel manifold 13, and a power generation reaction pipe is provided substantially at the center of the oxidant manifold 14. An oxidizing gas supply pipe 16 for supplying an external oxidizing gas (air) required for the air supply is connected.
[0027]
Further, the solid oxide fuel cell 1 has a sealless structure in which a gas leakage prevention seal is not provided on an outer peripheral portion of the power generation cell 7, and during operation, as shown in FIG. Fuel gas and oxidizing gas (air) discharged from a substantially central portion of the separator 10 toward the power generation cell 7 through the agent gas passage 18 are diffused in the outer peripheral direction of the power generation cell 7 while the fuel electrode layer 5 and the air electrode layer The power generation reaction is caused by being spread over the entire surface of the power generation cell 6 with a good distribution, and the residual gas not consumed by the power generation reaction is freely released from the outer peripheral portion of the power generation cell 7. Further, the housing 2 is provided with an exhaust pipe (exhaust hole) 19 for discharging excess gas released into the power generation reaction chamber 20 formed therein to the outside of the housing 2.
[0028]
By the way, in the solid oxide fuel cell 1 of the present embodiment, the temperature rise at the start of operation and the stop of operation are performed through the partition 25 formed by attaching the heat insulating material 26 to the lower part of the power generation reaction chamber 20 described above. A gas preheating chamber 30 is provided for efficiently preheating the fuel cell stack 3 when the temperature falls, and a burner 21 is installed inside a heat insulating material 26.
The burner 21 is configured to supply fuel gas from the outside of the gas preheating chamber 30 through a burner combustion gas supply pipe 22 piped to the burner 21 when the temperature is raised. The combustion operation in the burner 21 is performed together with the air supplied from the plurality of intake holes 23 provided.
[0029]
During the combustion operation, a preheating fuel gas pipe 27 and a preheating oxidizing gas pipe 28 which are heat exchange pipes at the time of preheating are arranged in proximity to the flame formed by the burner 21. As shown in FIG. 2, each of the preheating fuel gas pipe 27 and the preheating oxidizing gas pipe 28 is formed of a spirally formed metal pipe, and these pipes are arranged on a plane. The pipe structure 31 for heat exchange having high heat exchange efficiency is constituted by being combined in a nested state, and a steam reforming catalyst (not shown) (not shown) is provided inside the fuel gas pipe 27 for preheating inside the pipe body. , Ni, Ru, Pt, Rh, Ce, Ir, etc.).
[0030]
The fuel gas pipe for preheating 27 has an outer end piped to the outside of the housing 2, and a central end inserted through a ventilation hole 25 a provided in an upper partition wall 25 in a thickness direction to generate a power generation reaction chamber. The end is connected to the fuel gas supply pipe 15 in the power generation reaction chamber 20. On the other hand, the oxidizing gas pipe for preheating 28 has an outer end piped to the outside of the housing 2 and a central end inserted into the ventilation hole 25 a of the upper partition wall 25 to enter the power generation reaction chamber 20. It is guided and connected to the oxidizing gas supply pipe 16 in the power generation reaction chamber 20.
A transparent viewing window 29 is provided at the side of the gas preheating chamber 30 so that the combustion state of the burner 21, that is, the state of the flame can be monitored from the outside.
Further, in the configuration of the gas preheating chamber 30 described above, the number of the burners 21 is not limited to one, and a plurality of the burners 21 may be installed. A plurality are arranged in a ring shape so as to surround the fuel cell stack 3 so that the fuel cell stack 3 can be efficiently guided to the 20 side.
[0031]
Next, a preheating operation at the start of operation by the preheating mechanism having the above configuration will be described.
[0032]
At the time of preheating at the start of operation, first, an external fuel gas such as methane gas or hydrocarbon gas is supplied to the burner 21 from the burner combustion gas supply pipe 22 of the gas preheating chamber 30. The burner 21 starts the combustion operation with the mixed gas of the combustion gas and the combustion air supplied from the intake port 23, and the flame causes the spiral preheating fuel gas pipe 27 and the spiral preheating fuel gas pipe 27 arranged near and above the burner 21. The heat exchange piping structure 31 is heated by the preheating oxidant gas pipe 28. By the way, in the preheating operation of the embodiment, while monitoring the flame formed by the burner 21 from the viewing window 29, the preheating is gradually started with a simmering fire at the start of the preheating, and then the heating power is increased to increase the temperature to a predetermined temperature. I do.
[0033]
At the time of preheating, preheating air is supplied from the outside to the preheating oxidizing gas pipe 28. The preheating air is exchanged with heat while passing through the spiral gas pipe 28, and the heated air is Guided to the power generation reaction chamber 20 by the preheating oxidizing gas pipe 28, the oxidizing gas is supplied from the oxidizing gas supply pipe 16 to each separator 10 through the oxidizing manifold 14, a large number of connection pipes 12, and the like. The air is discharged to the air electrode side through the oxidant gas passage 18 inside, and diffuses and moves in the air electrode current collector 9 to reach the air electrode layer 6. Such a gas flow passage is as shown in FIG. 3, and the heated air exchanges heat with the metal separator 10 in the process of passing through the oxidizing gas passage 18 of the separator 10 to heat the separator 10 from the inside.
[0034]
In parallel with this, at the time of preheating, a mixed gas of steam and methane gas or a hydrocarbon gas (a fuel gas for a fuel cell is used) is supplied to the preheating fuel gas pipe 27. A steam reforming reaction of a hydrocarbon gas or a methane gas takes place in contact with the reforming catalyst in the spiral pipe to generate a reformed gas (H ₂ , CO, CO ₂ ). This reforming reaction is an endothermic reaction, and the heat required for the reforming reaction can use the combustion heat of the burner 21.
Here, the hydrogen obtained by the reforming reaction is less than the explosion limit for safety and the like, and the amount of hydrogen in the reformed gas is about 3% or less. Therefore, the amount of fuel gas supplied to the preheating fuel gas pipe 27 during preheating is extremely small.
[0035]
The reformed gas generated by this reforming reaction is guided to the power generation reaction chamber 20 through the fuel gas pipe 27 for preheating, and from the fuel gas supply pipe 15 to each separator 10 through the fuel manifold 13, a large number of connection pipes 11 and the like. The fuel gas is introduced and discharged from the separator side to the fuel electrode side through the internal fuel gas passage 17, and diffuses and moves in the fuel electrode current collector 8 to reach the fuel electrode layer 5. The heated reformed gas exchanges heat with the metallic separator 10 in the process of passing through the fuel gas passage 17 to heat the separator 10 from the inside, and the fuel electrode, in the same manner as the above-described effect of the heated air. By introducing hydrogen to the side, the fuel electrode layer 5 can be brought into a reducing atmosphere during temperature rise, and as a result, oxidation of Ni, which is the material of the fuel electrode layer 5, is prevented. Therefore, the hydrogen obtained by the reforming reaction in the preheating fuel gas pipe 27 is not used as a fuel gas for power generation unlike the conventionally known internal reforming.
[0036]
Further, as described above, while the preheating is performed from the inside of the power generation cell, the combustion gas generated from the burner 21 enters the power generation reaction chamber 20 through the upper ventilation hole 25a, and the inside of the reaction chamber. In the process of flowing upward, it comes into contact with the outer peripheral portion of the power generation cell, and the power generation cell 7 is also heated from the outer peripheral portion. As described above, since the plurality of vent holes 25a are arranged around the fuel cell stack 3, the entire outer peripheral portion of the fuel cell stack 3 can be uniformly heated from below to above. This combustion gas is sucked upward by a blower or the like (not shown) and exhausted to the outside through the upper exhaust hole 19.
[0037]
When the temperature of the fuel cell stack 3 is raised to the temperature at which power generation reaction is possible, the supply of fuel gas is cut off, the combustion operation of the burner 21 is stopped, and the fuel gas is supplied to the preheating fuel gas pipe 27 and the preheating oxidizing gas pipe 28. The supply of the heating gas and air is also stopped. After the temperature rise, the fuel gas is supplied from the fuel gas supply pipe 15, the air is supplied from the oxidant gas supply pipe 16, and the operation (power generation) of the fuel cell is started.
[0038]
According to the above operation method, the fuel cell stack 3 is heated from the outer peripheral portion by the combustion gas of the burner 21 introduced into the power generation reaction chamber 20 when the temperature is raised, and the preheating fuel gas pipe 27 and the preheating oxidizing gas are heated. Since the fuel cell stack 3 is also heated from the inside by the heating gas (reformed gas and air) introduced from the pipe 28, the temperature difference between the outer peripheral portion and the inside of the fuel cell stack 3 is kept small, and Temperature can be promoted. Thus, the temperature of the power generation cell 7 can be efficiently raised while preventing the power generation cell 7 from cracking. The preheating operation can be applied not only at the time of temperature rise at the start of operation but also at the time of temperature decrease at the time of operation stop.
[0039]
Further, by supplying a gas containing hydrogen generated by the reforming reaction in the preheating fuel gas pipe 27 to the fuel electrode layer 5, the fuel electrode layer 5 can be made to have a reducing atmosphere, and the fuel cell that is repeatedly performed In the temperature raising and lowering operations, the peeling phenomenon of the fuel electrode layer 5 due to the oxidation of Ni as the material of the fuel electrode layer 5 can be prevented, and stable power generation characteristics can be maintained.
[0040]
【The invention's effect】
As described above, according to the present invention, when the temperature is raised, the power generation cells are simultaneously heated from the outside and the inside, so that the temperature difference between the outer peripheral portion and the inside of the fuel cell stack is kept small while the power generation cells are raised. Can promote warmth. Therefore, the temperature of the power generation cell can be efficiently raised while preventing the power generation cell from cracking.
Also, during the temperature increase, hydrogen less than the explosion limit is supplied to the fuel electrode side, so that the fuel electrode layer is prevented from peeling off due to oxidation of Ni, which is a material of the fuel electrode layer, and the durability is improved. It is possible to maintain stable power generation characteristics even in repeated fuel cell heating and cooling operations.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an internal configuration of a solid oxide fuel cell according to the present invention.
FIG. 2 is a schematic configuration diagram of a main part of a fuel cell stack used for describing an embodiment of the present invention, showing a gas flow during operation.
FIG. 3 is a diagram showing a configuration of a heat exchange piping structure of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 3 Fuel cell stack 5 Fuel electrode layer 7 Power generation cell 10 Separator 20 Power generation reaction chamber 21 Burner 25 Partition 25a Ventilation passage (vent)
27 Fuel gas passage for preheating (fuel gas pipe for preheating)
28 Oxidizing gas passage for preheating (Oxidizing gas pipe for preheating)
30 gas preheating chamber

Claims (5)

A solid oxide fuel cell in which a fuel cell stack configured by alternately stacking power generation cells and separators is housed in a power generation reaction chamber, and a reaction gas is supplied into the fuel cell stack during operation to generate a power generation reaction. And
A gas preheating chamber provided with a burner is provided at a lower part of the power generation reaction chamber, and a preheating gas passage for introducing a preheating gas to the fuel cell stack at the time of heating and / or cooling is provided in the gas preheating chamber. A solid oxide fuel cell, comprising: In the gas preheating chamber, a preheating fuel gas passage for introducing a preheating gas to the fuel cell stack when the temperature is raised is disposed, and a reforming catalyst is disposed in the preheating fuel gas passage. The solid oxide fuel cell according to claim 1, wherein 3. The air conditioner according to claim 1, further comprising an air passage for introducing the combustion gas of the burner into the power generation reaction chamber in a partition wall between the power generation reaction chamber and the gas preheating chamber. 4. Solid oxide fuel cell. 4. The solid oxide fuel cell according to claim 3, wherein a plurality of the ventilation paths are provided around the fuel cell stack. 5. The method for operating a solid oxide fuel cell according to claim 1, wherein a combustion operation of said burner is started during preheating to preheat an oxidizing gas passage for preheating. Heat air and supply it to the oxidizer electrode layer of the power generation cell through the separator, and introduce a mixed gas of steam and hydrocarbon gas into the preheating fuel gas passage, and perform a reforming reaction to reduce the explosion below the lower limit. By generating a gas containing hydrogen and supplying the gas to the fuel electrode layer of the power generation cell through the separator, the power generation cell is heated from the inside, and the power generation cell is heated from the outside by the combustion gas of the burner. Operating method of a solid oxide fuel cell.

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