JP5601945B2 - Starting method of solid oxide fuel cell - Google Patents

Description

  The present invention relates to a method for starting a solid oxide fuel cell.

A solid oxide fuel cell (SOFC) supplies a fuel gas to a fuel electrode and a fluid containing an oxidant to an air electrode, and is contained in the fuel and the oxidant gas contained in the fuel gas. Electric power is generated by causing a chemical reaction with oxygen to be generated through a solid electrolyte (for example, Patent Document 1). In general, natural gas, LPG, petroleum, methanol, coal gasification gas, or the like is used as the fuel gas, and air is used as the oxidant gas.
Since SOFC generally includes a solid electrolyte that exhibits high oxygen ion permeability at high temperatures, the operating temperature is about 900 ° C to 1000 ° C.

  As a method for starting a SOFC in which a power generation cell including a fuel electrode, an air electrode, and a fixed electrolyte is disposed in a power generation chamber, air heated outside the power generation chamber is supplied to the power generation chamber, and the generated heat is used to operate the operating temperature. The method of raising the temperature is taken.

JP 2004-119298 A

  In the SOFC as described above, both ends of a cell tube in which a power generation cell is formed on the outer surface are usually supported by metal members. The air supplied into the power generation chamber passes through this metal member. However, if the metal member becomes too high in temperature, the metal is oxidized and the life is shortened. Therefore, the temperature of the air supplied into the power generation chamber is limited to about 600 ° C. On the other hand, since the power generation cell generates power at about 900 ° C., it is necessary to raise the temperature of the air supplied into the power generation chamber from 600 ° C. to 900 ° C. In order to raise the temperature of the air to 900 ° C., the self-heating of the power generation cell itself is used.

  The electric resistance of the solid electrolyte depends on the temperature, and is several tens of ohms when the temperature is higher than 600 ° C., and several hundreds Ω when the temperature is 600 ° C. or lower. For this reason, since the resistance of the battery is large at a low temperature, a sufficient power generation load cannot be obtained, and therefore a sufficient amount of heat generation required for temperature rise cannot be ensured. Therefore, since it takes 2 to 4 days to start up the solid oxide fuel cell in the current technology that takes a long time to raise the temperature to the operating temperature using only self-power generation, a combination of SOFC and gas turbine is required. In the combined cycle, the start / stop response is not good.

  In order to shorten the heating time of the power generation cell, conventionally, a method of heating the power generation chamber from the outside using a high-temperature heat source such as an electric heater has been used. However, such a method requires a separate high-temperature heat source, which increases the cost.

  In Patent Document 1, a combustion catalyst layer is disposed in an air introduction pipe that guides air into a bottomed cylindrical fuel cell, and a fuel gas for temperature increase is burned in each fuel cell. However, since an air introduction tube is inserted and disposed in each fuel cell, and a catalyst layer is formed on the fuel cell air electrode, the configuration of the fuel cell is complicated and its manufacture becomes difficult. It was. Further, Patent Document 1 does not describe the concentration of the fuel gas for raising temperature, and the fuel gas supplied to the air introduction pipe may burn at the metal portion, and the metal member may also rise in temperature. .

  The present invention has been made in view of such circumstances, and is a solid oxide fuel cell that can raise the temperature of a power generation cell to an operating temperature more quickly at a low cost without a complicated configuration. The purpose is to provide an activation method.

  In order to solve the above problems, the present invention comprises a power generation chamber in which a power generation cell including a fuel electrode, a solid electrolyte, and an air electrode having oxidation catalyst performance are arranged in order, and at least a part of which is made of a metal member. And an oxidant supply path for supplying a fluid containing an oxidant to the air electrode side in the power generation chamber, and a heat insulator that separates the power generation chamber and the oxidant supply path in a breathable manner. Supplying a fluid containing the oxidant preheated via the oxidant supply path to the air electrode side of the power generation chamber of the solid oxide fuel cell; and a temperature at which the air electrode is capable of catalytic combustion. And a step of adding a fluid containing a flammable fuel having a flammable limit concentration or less to the fluid containing the oxidant.

  According to the above invention, since the combustible fuel gas is supplied to the air electrode side at a combustible limit concentration or less, the combustible fuel gas can be prevented from self-igniting, and the temperature rise can be made efficient. it can. The combustible fuel gas is catalytically combusted by an oxidation catalyst contained in the air electrode. Catalytic combustion is a flameless combustion method in which complete oxidation of a lean fuel having a concentration lower than the flammability limit, which is difficult with ordinary flame combustion, proceeds stably at a relatively low temperature by utilizing a catalytic oxidation reaction on the catalyst surface. Accordingly, since the combustible fuel gas burns only on the surface of the air electrode, it is possible to raise the temperature of only the power generation cell while keeping the metal member constituting the oxidant supply path below the heat resistant temperature. Thereby, the temperature rising time of the power generation cell can be shortened without using an external high-temperature heat source such as an electric heater. Moreover, since the catalyst is contained in the air electrode, it is not necessary to add a new configuration to the power generation cell, and the reliability can be improved.

1 aspect of the said invention WHEREIN: It is preferable that the said combustible fuel gas is gas or hydrogen which has methane as a main component, and the said combustible limit concentration is 3 volume% or less.
By doing so, the temperature of the power generation cell can be raised more safely.

In one aspect of the invention described above, the air electrode is composed of a material obtained by mixing the La _1-x Sr _x conductive perovskite oxide represented by MnO ₃ and zirconia-based electrolyte materials, the catalytic combustion temperature capable Is preferably 400 ° C. or higher.
By setting it as the said structure, Mn contained in an air electrode acts as an oxidation catalyst, and combustible fuel gas can be catalytically burned at 400 degreeC or more. Since the fluid containing the oxidizing agent is heated in advance before supply and then passes through the metal member, the temperature should not be too high.

In one aspect of the invention, after the temperature in the power generation chamber reaches 750 ° C. or higher, starting the load increase and power generation in the power generation cell, and starting power generation in the power generation cell, And a step of stopping the supply of the combustible fuel gas to the air electrode side.
If the load is increased or the power generation cell generates power when the power generation cell is at a low temperature, the performance deterioration may be accelerated. According to the above aspect, by combusting the combustible fuel gas, it is not necessary to generate power in a high resistance region where the temperature of the power generation cell is low and to raise the temperature by self-heating. Thereby, the life of the power generation cell can be extended by setting the temperature at which the power generation cell starts power generation to some extent higher than the self-power generation possible temperature. Furthermore, when the power generation cell self-heats, the load increases and the temperature rise can be accelerated. Therefore, the start-up time of the SOFC can be greatly shortened by controlling the catalytic combustion and the self-heating.

In the invention, the combustible fuel gas is supplied to the fuel electrode side of the power generation chamber at an earlier stage than the air electrode side, and the combustible fuel gas discharged from the fuel electrode side of the power generation chamber is supplied. A step of circulating and supplying the fuel electrode again; and a step of supplying a part of the circulating combustible fuel gas to the air electrode side of the power generation chamber when the air electrode is at a temperature at which catalytic combustion is possible. And.
By doing so, the amount of combustible fuel gas used can be suppressed.

  According to the present invention, a combustible fuel gas having a flammable limit concentration or less is supplied to an air electrode having oxidation catalyst performance together with a fluid containing an oxidant, so that the configuration is not complicated, the cost is low, and the speed is increased. The power generation cell can be raised to the operating temperature. Furthermore, the combined use with the self-heating of the power generation cell can greatly reduce the startup time of the SOFC.

It is a schematic diagram explaining the structure of the solid oxide fuel cell which concerns on 1st Embodiment. It is a schematic diagram explaining the structure of a power generation cell. It is the figure which measured the temperature of the power generation chamber inside at the time of supplying combustible fuel gas. It is a schematic diagram explaining the structure of the solid oxide fuel cell which concerns on 2nd Embodiment. It is a figure which shows a starting profile.

The present invention relates to a method for starting a solid oxide fuel cell, in which a combustible fuel gas having a flammability limit concentration or less is supplied to an air electrode containing an oxidation catalyst, whereby the air electrode is catalytically combusted, and a cell tube is formed. This is a starting method for raising the temperature. Furthermore, this is a start-up method that efficiently raises the temperature of the cell tube in the power generation unit to a temperature at which steady power generation operation can be performed by using a combination of temperature rise by catalytic combustion and self-heating by power generation of the power generation cell.
Hereinafter, an embodiment of a method for starting a solid oxide fuel cell according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic diagram illustrating the configuration of a solid oxide fuel cell according to this embodiment.
The solid oxide fuel cell (SOFC) 1 according to the present embodiment includes at least a power generation chamber 10, a power generation cell 11, a fuel supply path 12, an oxidant supply path 13, a fuel discharge path 14, an oxidant discharge path 15, and heat insulation. A body 16 is provided.

The power generation chamber 10 includes a plurality of cell tubes 17 in which a plurality of power generation cells 11 are formed.
The fuel supply path 12 is provided so that a fluid (fuel gas) containing fuel is supplied through the cell tube 17. The oxidant supply path 13 is provided so that a fluid containing oxidant (air in this embodiment) is supplied to the outside of the cell tube 17. The fuel discharge path 14 is provided so that the fuel gas supplied into the power generation chamber 10 can be discharged from the power generation chamber 10 to the outside. The oxidant discharge path 15 is provided so that the air supplied into the power generation chamber 10 can be discharged from the power generation chamber 10 to the outside.

Both ends of the plurality of cell tubes 17 are supported by a pair of tube plates 18 made of a metal such as a steel type mixed with Cr. The tube sheet 18 is a part of the constituent members of the oxidant supply path 13 and the oxidant discharge path 15. In FIG. 1, the upper tube plate 18 serves as a partition wall between the oxidant discharge path 15 and the fuel supply path 12. By sealing the tube plate 18 and the cell tube 17, each gas leaks into each path. To prevent that. Similarly, the lower tube plate 18 serves as a partition wall between the oxidant supply path 13 and the fuel discharge path 14.
Between the pair of tube plates, the heat insulators 16 are arranged on the tube plate 18 side from both ends of the plurality of power generation cells 11 formed in the cell tube 17, respectively. The supply path 13 and the oxidant discharge path 15 are separated so as to allow ventilation. The heat insulator 16 is formed of a material having heat insulation properties.

  Further, in the SOFC system including the SOFC 1, a combustible fuel supply unit that supplies a combustible fuel gas into the oxidant supply path 13 in the middle of the oxidant supply path 13, and air that is supplied into the power generation chamber 10. A preheating heater for heating in advance is provided (not shown).

  As shown in FIG. 2, the power generation cell 11 has a configuration in which a fuel electrode 19, a solid electrolyte 20, and an air electrode 21 are sequentially formed on the outer surface of the cell tube 16. The plurality of power generation cells 11 formed on the outer surface of the cell tube 16 are electrically connected in series with an interconnector 22.

The fuel electrode 19 is composed of a composite material of Ni and a zirconia-based electrolyte material, and for example, Ni / YSZ is used.
The solid electrolyte 20 is electronically insulating, and is required to have gas tightness that does not allow gas to pass and high ion permeability at high temperatures. Therefore, YSZ is mainly used for the solid electrolyte 20.
The air electrode 21 is made of a material obtained by mixing a conductive perovskite oxide represented by La _1-x Sr _x MnO ₃ and a zirconia-based electrolyte material. Mn contained in the air electrode 21 acts as an oxidation catalyst.
The interconnector 22 is composed of a conductive perovskite oxide represented by M _1-x L _x TiO ₃ (M is an alkaline earth metal element, L is a lanthanoid element) such as SrTiO ₃ system, and is composed of fuel gas and air. It is a dense film so as not to mix.

Next, a method for starting the SOFC having the above configuration will be described.
When the SOFC 1 is started, air (combustion gas) heated by a preheating heater, a start-up combustor, or the like is supplied into the power generation chamber 10 via the oxidant supply path 13. When the air electrode 21 reaches a predetermined temperature that functions as a catalyst, combustible fuel gas is supplied into the power generation chamber 10 through the oxidant supply path 13 together with air. Here, the temperature at which the air electrode 21 of the present embodiment starts to function as a catalyst is 400 ° C. or higher.
In the present embodiment, since the air electrode 21 is formed on the outer surface of the power generation cell 16, when the temperature of the power generation chamber 10 reaches 400 ° C. or more, the combustible fuel gas and the oxidant supply path are supplied together with the air. 13 can be supplied into the power generation chamber 10 via the
Therefore, when the temperature of the air supplied into the power generation chamber 10 becomes at least 400 ° C. or more, the combustible fuel gas may be supplied into the power generation chamber 10 through the oxidant supply path 13 together with the air. it can. At this time, since the air supplied into the power generation chamber 10 passes through the oxidant supply path 13 having a metal member, the temperature needs to be 600 ° C. or lower.

  The combustible fuel gas is supplied to the power generation chamber 10 in a state where the combustible fuel gas is mixed with air at a concentration equal to or lower than the combustible limit concentration of the combustible fuel gas. In this embodiment, combustible fuel gas is supplied at 3 volume% or less with respect to the supply amount of air. As the combustible fuel gas, a gas mainly composed of methane such as city gas, hydrogen, or the like can be used.

  In the power generation chamber 10 into which the air and the combustible fuel gas have flowed, the combustible fuel gas is catalytically burned on the air electrode 21 due to the catalytic action of Mn contained in the air electrode 21 to generate combustion heat. This combustion heat raises the temperature of the power generation cell 11. By controlling the mixed concentration of air and combustible fuel gas, the amount of heat generated by catalytic combustion of the combustible fuel gas can be changed to control the temperature rise.

On the other hand, when SOFC 1 is activated, N ₂ and H ₂ , or a city gas reformed gas (CO ₂ , methane, CO, water vapor) containing water vapor or the like is used as a reducing gas in the cell tube 16 and a fuel supply path. 12 is supplied.
Air flowing into the power generation chamber 10 through the oxidant supply path 13, unburned combustible fuel gas, and combustion gas generated by catalytic combustion are sequentially discharged outside the power generation chamber 10 through the oxidant discharge path 15. Is done. The reducing gas that has flowed into the cell tube 16 through the fuel supply path 12 is sequentially discharged to the outside of the power generation chamber 10 through the fuel discharge path.

After the power generation cell 11 becomes high temperature due to the catalytic combustion described above, the reducing gas that has been introduced into the power generation chamber 10 (in the cell tube 16) via the fuel supply path 12 is switched to the fuel gas necessary for power generation. Thereby, the power generation cell 11 starts power generation. Moreover, the load increase of SOFC1 is started with the start of electric power generation of the power generation cell 11.
The fuel gas necessary for power generation is started to be input after the power generation cell 11 becomes high temperature when the power generation cell 11 is generated at a low temperature, that is, when the solid electrolyte 20 is in a high resistance state. This is because the electrode constituent material deteriorates due to a change in structure, which causes a decrease in performance of the power generation cell 11. For this reason, it is preferable that the timing for supplying the fuel gas is when the temperature in the power generation chamber 10 is 750 ° C. or higher.
When fuel gas such as city gas is supplied into the power generation chamber 10 (in the cell tube 16) under conditions necessary for power generation, the power generation cell 11 starts power generation. At this time, the power generation cell 11 is heated by heat generated by power generation (self-generated heat generation) and combustion heat by catalytic combustion.

  Even after the power generation cell 11 starts power generation, the addition of the combustible fuel gas to the air supplied into the power generation chamber 10 through the oxidant supply path 13 is continued for a while. Immediately after the power generation cell 11 starts power generation, the self-generated heat generation amount of the power generation cell 11 is not sufficient to maintain the temperature in the power generation chamber 10 by itself. Accordingly, if the supply of the combustible fuel gas is stopped at this time, the temperature in the power generation chamber 10 is lowered.

  After the load increase of the SOFC 1 progresses and the calorific value of the self-generated heat of the power generation cell 11 becomes sufficient to maintain the temperature in the power generation chamber 10, the combustible fuel gas to the air supplied into the power generation chamber 10 Stop the addition. Here, the amount of the combustible fuel gas added is preferably gradually reduced so that it becomes zero when the power generation cell 11 reaches the temperature required at the rated load of the SOFC 1 (900 ° C. in this embodiment). . The calorific value for raising the temperature of the power generation cell 11 to a necessary temperature at the rated load of the SOFC 1 can be obtained by self-generated heat generation of the power generation cell 11. Therefore, by reducing the power generation cell 11 so that it becomes zero when the temperature reaches the required temperature at the rated load of the SOFC 1, it is possible to prevent the temperature increase of the power generation cell 11 and to suppress the deterioration of the SOFC 1. it can. Further, by gradually reducing the amount of the combustible fuel gas added, the period during which the power generation cell 11 is heated by self-generated heat and catalytic combustion can be lengthened, and the temperature is increased only by self-generated heat. Compared with the case where it is done, the time required to reach the required temperature at the rated load can be shortened.

  The start-up is completed when the SOFC 1 reaches the rated load. At this time, the temperature inside the power generation chamber in this embodiment is about 900 ° C.

  According to said structure, since the oxidation catalyst is contained in the air electrode 21, the power generation cell 11 and the cell tube 16 do not need an additional structure. Combustible fuel gas is added to the oxidant, and the temperature of the power generation cell can be raised by catalytic combustion by the action of the oxidation catalyst of the air electrode 21. This eliminates the need for a heating source such as an electric heater. The combustible fuel gas is selectively catalytically burned on the air electrode 21. Therefore, the temperature rise of the metal member constituting the oxidant supply path 13 can be suppressed. Thereby, oxidation of the metal member is also suppressed. Further, since the combustible fuel gas is selectively catalytically burned on the air electrode 21, the temperature of the power generation cell 11 can be increased efficiently and quickly.

  Since the temperature of the power generation cell 11 can be raised by catalytic combustion of combustible fuel gas, it is possible to supply air that has been conventionally supplied at about 600 ° C. at a temperature lower than that in the past. By setting the supplied air to 400 ° C. or higher in advance, the combustible fuel can be catalytically combusted. The temperature of the supplied air is preferably lower. By doing so, deterioration of the metal member can be suppressed.

  By supplying the combustible fuel gas at a combustible limit concentration or less, preferably 3 vol% or less, it is possible to prevent self-ignition and combustion in the absence of the oxidation catalyst (air electrode 21). As a result, the temperature of the power generation cell can be increased efficiently, and the startup time of the SOFC can be shortened.

  As described above, when power generation is started when the temperature of the power generation cell 11 is low, power is generated in a high resistance region, which causes a decrease in performance of the power generation cell 11 due to deterioration due to a structural change of the electrode constituent material. According to this embodiment, the temperature degradation of the power generation cell 11 can be suppressed by starting the power generation after the temperature of the power generation cell 11 is raised to an arbitrary temperature by catalytic combustion.

  Since the heat insulator 16 is disposed between the power generation chamber 10 and the oxidant supply path 13 and the oxidant discharge path 15, it is possible to prevent heat in the power generation chamber 10 from escaping to the outside. As a result, the temperature increase rate of the power generation cell 11 can be prevented from being lowered, and the fuel consumption at the time of starting the SOFC 1 can be reduced and the time required for starting can be shortened.

Note that this embodiment can also be applied at the time of restart at the time of load interruption of the SOFC 1.
When shutting off the load of the SOFC 1, combustible fuel gas is supplied together with air into the power generation chamber 10 via the oxidant supply path 13, and the temperature in the power generation chamber 10 is maintained at 750 ° C. or higher. By doing so, when restarting power generation, it is possible to shorten the temperature rise time to the rated state (900 ° C.).

(Verification of temperature change inside the power generation room by supplying flammable fuel gas)
Fuel electrode (Ni (64 mass%) + YSZ (Y ₂ O ₃ 10 mol% added ZrO ₂ , 24 mass%) + Al ₂ O ₃ (12 mass%)), solid electrolyte (Y ₂ O ₃ 10 mol% added ZrO ₂ ), A cell tube (calcium stable) in which a power generation cell composed of an air electrode (La _1-xy Sr _x Ca _y MnO ₃ ) and an interconnector (Sr _0.9 La _0.1 TiO ₃ ) is sequentially formed on the outer surface. SOFC was prepared using 48 zirconia).

Next, the startup procedure until the SOFC steady power generation is started will be described. First, externally heated air was supplied at 17.3 Nm ³ / h into the power generation chamber via the oxidant supply path. Further, N ₂ was supplied into the power generation chamber (in the cell tube) through the fuel supply path.

When the temperature in the power generation chamber (the temperature of the air heated outside) reached 300 ° C., the supply of fuel gas / water vapor into the power generation chamber (in the cell tube) via the fuel supply path was started. City gas was used as fuel gas. The supply flow rate of the fuel gas was 0.08 Nm ³ / h. The flow rate of water vapor was set to 0.3 Nm ³ / h. The fuel gas discharged from the fuel discharge path was recirculated at 4 Nm ³ / h.

  When the temperature in the power generation chamber (the temperature of the air heated outside) reached 300 ° C., the supply of combustible fuel gas was started. The combustible fuel gas was mixed with air at a rate of 3% by volume with respect to the amount of air supplied.

  The supply of combustible fuel gas was continued until the temperature inside the power generation chamber reached 700 ° C., and the temperature inside the power generation chamber inside the power generation chamber, the temperature of the supply air, and the hydrogen concentration at the oxidant discharge path outlet were measured. The temperature inside the power generation chamber was measured by measuring the surface temperature of the upper element, intermediate element, and lower element of the power generation cell. The measurement results are shown in FIG. In the figure, the horizontal axis represents time, the vertical axis (left) represents temperature, and the vertical axis (right) represents outlet hydrogen concentration.

  According to FIG. 3, the temperature inside the power generation chamber increased along with the temperature increase of the supply air. Further, when the temperature inside the power generation chamber reached 400 ° C. or higher, the temperature inside the power generation chamber rose earlier than the temperature rise of the supply air. On the other hand, the hydrogen concentration in the outlet air decreased as the temperature inside the power generation chamber increased. From the above results, it is considered that catalytic combustion of hydrogen started at around 400 ° C., and the temperature rising rate inside the power generation chamber was increased by the combustion heat. As a result, it is possible to shorten the time from the normal temperature to the rated state in about 24 hours, that is, about 1/3 of the conventional time.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described with reference to FIG.
The basic configuration of the SOFC 1 of this embodiment is the same as that of the first embodiment, but the supply source of combustible fuel gas is different.

  In the SOFC system including the SOFC 1 of the present embodiment, the fuel supply path 12 and the fuel discharge path 14 are connected by a fuel recirculation path 23. The fuel recirculation path 23 includes a pump 24 and can circulate the fuel gas discharged from the power generation chamber 10 to the combustion supply path 12. The fuel recirculation path 23 is branched to a combustible fuel gas supply path 25 behind the pump 24 in the flow direction. The other end of the combustible fuel gas supply path 25 is connected to the oxidant supply path 13. A flow meter 26 is provided between the pump 24 and the branch portion of the combustible fuel gas supply path 25. In addition, a preheating heater 27 that preheats the air supplied into the power generation chamber 10 to a predetermined temperature and a combustible fuel supply unit 28 that supplies a combustible fuel gas into the oxidant supply path 13 in the middle of the oxidant supply path 13 are provided. The oxidant supply path 13 is disposed in the vicinity.

Next, a method for starting the SOFC 1 in the SOFC system configured as described above will be described.
When the SOFC 1 is activated, a reducing gas such as N ₂ or H _{2 is} supplied into the power generation chamber 10 (in the cell tube 16) via the fuel supply path 12. Further, the air heated by the preheating heater is supplied into the power generation chamber via the oxidant supply path 13. After the inside of the power generation chamber 10 reaches a predetermined temperature (for example, 300 ° C.), fuel gas and water vapor are supplied into the power generation chamber 10 through the fuel supply path 12. After the supplied air reaches a predetermined temperature (for example, an arbitrary temperature of 450 ° C. or higher and 550 ° C. or lower), combustible fuel gas is supplied into the power generation chamber 10 through the oxidant supply path 13 together with the air of the predetermined temperature. Supply.

As the combustible fuel gas, a recirculated fuel gas branched from the fuel recirculation path 23 is used. The combustible fuel gas is supplied at a concentration lower than the combustible limit concentration of the combustible fuel gas. In this embodiment, combustible fuel gas is supplied at 3 volume% or less with respect to the supply amount of air. The supply amount of the combustible fuel gas is appropriately adjusted based on the recirculation gas amount flowing through the fuel recirculation path 23 measured by the flow meter 26.
As the combustible fuel gas, a gas mainly composed of methane such as city gas, hydrogen, or the like can be used.

  In the power generation chamber 10 into which the air and the combustible fuel gas have flowed, the combustible fuel gas is catalytically burned on the air electrode 21 due to the catalytic action of Mn contained in the air electrode 21 to generate combustion heat. This combustion heat raises the temperature of the power generation cell 11. By controlling the mixed concentration of air and combustible fuel gas, the amount of heat generated by catalytic combustion of the combustible fuel gas can be changed to control the temperature rise.

  Air flowing into the power generation chamber 10 through the oxidant supply path 13, unburned combustible fuel gas, and combustion gas generated by catalytic combustion are sequentially discharged outside the power generation chamber 10 through the oxidant discharge path 15. Is done. The reducing gas flowing into the power generation chamber 10 through the fuel supply path 12 is sequentially discharged to the outside of the power generation chamber 10 through the fuel discharge path.

  Thereafter, similarly to the first embodiment, load increase and power generation of the power generation cell 11 are started, and supply of combustible fuel gas is stopped.

  According to said structure, while being able to acquire the effect similar to 1st Embodiment, the total amount of the combustible fuel gas to be used can be reduced.

(Example)
Fuel electrode (Ni (64 mass%) + YSZ (Y ₂ O ₃ 10 mol% added ZrO ₂ , 24 mass%) + Al ₂ O ₃ (12 mass%)), solid electrolyte (Y ₂ O ₃ 10 mol% added ZrO ₂ ), cathode _{(La 1-x-y Sr} x Ca y MnO 3), and the interconnector _{(Sr 0.9 La} 0.1 TiO ₃₎ with 48 and to produce a cartridge of SOFC.

In accordance with the profile shown in FIG. 5, the SOFC produced above is started. First, air heated outside is supplied at 17.3 Nm ³ / h into the power generation chamber through the oxidant supply path. Further, N ₂ is supplied into the power generation chamber (in the cell tube) through the fuel supply path.

When the temperature in the power generation chamber (the temperature of the air heated outside) reaches 300 ° C., supply of fuel gas / water vapor into the power generation chamber (in the cell tube) is started via the fuel supply path. The city gas is used as the fuel gas, and the supply flow rate of the fuel gas is 0.08 Nm ³ / h. The flow rate of water vapor is set to 0.3 Nm ³ / h. The fuel gas discharged from the fuel discharge path is recirculated at 4 Nm ³ / h.

  When the temperature in the power generation chamber (the temperature of the air heated outside) reaches 400 ° C., the supply of combustible fuel gas is started. The combustible fuel gas is mixed with air at a rate of 3% by volume with respect to the amount of air supplied.

  When the temperature in the power generation chamber (surface temperature of the power generation cell) reaches 750 ° C., the supply of combustible fuel gas is stopped. In addition, the supply of water vapor to the fuel supply path is stopped, and the supply amount of city gas is increased. Also, load increase is started.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 Solid oxide fuel cell (SOFC)
DESCRIPTION OF SYMBOLS 10 Power generation chamber 11 Power generation cell 12 Fuel supply path 13 Oxidant supply path 14 Fuel discharge path 15 Oxidant discharge path 16 Thermal insulator 17 Cell tube 18 Tube plate 19 Fuel electrode 20 Solid electrolyte 21 Air electrode 22 Interconnector 23 Fuel recirculation path 24 pump 25 combustible fuel supply path 26 flow meter 27 electric heater 28 combustible fuel supply section

Claims (5)

A power generation chamber in which a power generation cell including a fuel electrode, a solid electrolyte, and an air electrode having oxidation catalyst performance is disposed in order;
An oxidant supply path, at least part of which is made of a metal member, for supplying a fluid containing an oxidant to the air electrode side in the power generation chamber;
A heat insulator that separates the power generation chamber and the oxidant supply path so as to allow ventilation;
On the air electrode side in the power generation chamber of the solid oxide fuel cell comprising:
Supplying a fluid containing the oxidant preheated via the oxidant supply path;
Adding a fluid containing a flammable fuel having a flammable limit concentration or less to a fluid containing the oxidant when the air electrode has a temperature capable of catalytic combustion;
After the power generation chamber reaches a predetermined temperature by supplying the fluid containing the oxidant, the combustible fuel gas is supplied to the fuel electrode side of the power generation chamber at an earlier stage than the air electrode side, Circulating the combustible fuel gas discharged from the fuel electrode side of the power generation chamber and supplying the fuel electrode again to the fuel electrode;
Supplying a part of the flammable fuel gas that circulates to the air electrode side of the power generation chamber when the air electrode has a temperature capable of catalytic combustion ;
A method for starting a solid oxide fuel cell, comprising: The fluid containing the combustible fuel is a gas or hydrogen containing methane as a main component,
The start-up method for a solid oxide fuel cell according to claim 1, wherein the flammable limit concentration is 3% by volume or less. The air electrode is composed of a material obtained by mixing a conductive perovskite oxide represented by La _1-x Sr _x MnO ₃ and a zirconia-based electrolyte material,
The method for starting a solid oxide fuel cell according to claim 1 or 2, wherein the temperature at which the catalytic combustion is possible is 400 ° C or higher. After the temperature in the power generation chamber reaches 750 ° C. or higher, starting the load increase and power generation of the power generation cell;
Stopping the supply of the combustible fuel gas to the air electrode side in the power generation chamber after starting the power generation of the power generation cell;
A method for starting a solid oxide fuel cell according to any one of claims 1 to 3, comprising:   The temperature of the power generation chamber is maintained by supplying the combustible fuel gas together with the fluid containing the oxidant through the oxidant supply path when shutting off the power generation of the power generation cell. 5. A method for starting a solid oxide fuel cell as described in 4.

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