JP5779371B2 - Fuel cell and operation method thereof - Google Patents

Description

  The present invention relates to a fuel cell having a combustor that catalytically combusts exhaust gas from a fuel cell stack, and more particularly, to a structure and method for operation at start-up of a fuel cell.

  In recent years, fuel cells that directly convert chemical energy into electrical energy have attracted attention as high-efficiency and clean power generation devices, and in particular, solid oxide electrolyte fuel cells (SOFC) are excellent in power generation efficiency. Expansion to applications is expected.

  In general, SOFC has a high temperature of 600 ° C. to 800 ° C. at the time of power generation, and it is necessary to raise the temperature of the fuel cell stack before reaching the power generation possible temperature of 600 ° C. to 700 ° C. at the time of startup. As a configuration for increasing the temperature at the time of starting the SOFC, it has been proposed to provide a heating burner on the bottom surface of the fuel cell stack (see, for example, Patent Document 1).

JP 2004-335163 A

  In the fuel cell configured as described above, the stack is heated from the inside by the air heated by the burner, and the fuel cell stack is heated from the outer periphery by the burner combustion gas. By suppressing the temperature difference between the two, the power generation cell can be efficiently heated while preventing the power generation cell from cracking. However, in this method, it is considered that delicate temperature control of air and combustion gas entering the battery stack is difficult, and there is a high possibility that a large temperature gradient occurs in the power generation cell and cell cracking occurs. This tendency is more remarkable when there are a plurality of fuel cell stacks. Moreover, since a large-sized burner is provided for increasing the temperature, the hot module is increased in size.

  In order to solve the above-described problems, the object of the present invention is to prevent cracking of the power generation cell by providing a heating structure that uniformly raises the temperature of the entire fuel cell stack during startup while avoiding an increase in the size of the entire fuel cell. It is to provide a highly reliable fuel cell.

  In order to achieve the above-described object, a fuel cell according to the present invention includes a fuel cell stack formed by stacking a plurality of power generation cells that generate electricity by reacting fuel and air, and exhaust fuel discharged from the fuel cell stack. The reformed fuel is generated by steam reforming the combustor for generating heat by burning the exhaust air and the fuel introduced from the outside and the fuel introduced from the outside using the heat generated in the combustor. A reformer for supplying quality fuel to the fuel cell stack, an air preheater for heating air introduced from the outside by heat generated in the combustor and supplying the fuel cell stack, and the air preheater The temperature of the air supplied to the fuel cell stack is adjusted by adjusting the flow ratio between the flow rate of the air heated by the air and the flow rate of the air that is directly introduced into the fuel cell stack by bypassing the air preheater. Gosuru and a air temperature control mechanism.

  According to this configuration, even when the temperature of the fuel cell stack is increased at the time of starting the fuel cell, the fuel cell stack can be heated from the inside using the air preheater, and the air temperature control mechanism is provided. The temperature of the air introduced into the fuel cell stack can be controlled. In particular, when the temperature is raised at the start of the fuel cell, the temperature can be controlled to a desired rate. Therefore, damage to the power generation cell due to rapid heating is avoided, so that the reliability of the fuel cell is improved. Furthermore, since no additional heat source device is required, an increase in the size of the entire fuel cell is suppressed.

The fuel cell according to an embodiment of the present invention preferably further includes a reducing gas introduction path that is connected to the reformer and introduces a reducing gas into the reformer. According to this configuration, reducing gas such as H ₂ and CO is fueled via the reducing gas introduction path and the reformer when the fuel cell that cannot introduce the fuel such as city gas into the reformer is started. Since it can be introduced into the battery stack, it is possible to prevent oxidation of the reforming catalyst in the reformer and the power generation cell fuel electrode at the start-up, and the performance of the fuel cell is prevented from deteriorating. Further, since the reducing gas can be further introduced into the combustor and used for the catalytic combustion reaction, it is possible to efficiently raise the temperature.

  In the fuel cell according to an embodiment of the present invention, it is preferable that the air preheater is disposed to face at least a part of a side surface of the fuel cell stack. According to this configuration, the fuel cell stack is not only heated from the inside by the air from the air preheater, but also from the outside by the radiant heat of the air preheater, so that the entire fuel cell stack is heated more uniformly. Is done.

  In the fuel cell according to an embodiment of the present invention, the combustor is a catalytic combustor that burns the exhaust fuel and exhaust air with a catalyst, and causes a catalytic combustion reaction by the catalyst inside or outside the combustor. There may be provided a catalyst heater for heating to a temperature required for this. Alternatively, a combustible gas introduction path for introducing a combustible gas into the air preheater may be connected, and a combustible gas igniter for combusting the combustible gas may be provided in the air preheater. . According to these configurations, it is possible to raise the temperature of the fuel cell stack without adding a large-scale heat source device such as a start burner.

  In the fuel cell according to an embodiment of the present invention, it is preferable that the combustor and at least one of the reformer and the air preheater are integrally formed. According to this configuration, the fuel cell can be made compact by suppressing heat loss in heat supply from the combustor to the reformer or the air preheater.

  In the fuel cell according to an embodiment of the present invention, the fuel cell stack is formed by stacking a plurality of flat rectangular parallelepiped power generation cells, and the reformer, the air preheater, and the combustor include the fuel cell. It is preferable to form a square tube-shaped stack surrounding unit that surrounds the outer periphery of the stack. According to this configuration, it is possible to raise the temperature of the fuel cell stack more uniformly and efficiently using not only the air preheater but also the radiant heat from the reformer.

  Further, the fuel cell operating method according to the present invention includes a flow rate of air flowing into the fuel cell stack after being heated by the air preheater by the air temperature control mechanism, and directly bypassing the air preheater. Controlling the temperature of the air introduced into the fuel cell stack by adjusting the flow rate ratio with the flow rate of the air introduced into the fuel cell stack. According to this configuration, it is possible to heat the fuel cell stack from the inside using the air preheater even at the temperature rise at the time of starting the fuel cell, and furthermore, by providing the air temperature control mechanism, The temperature of the air introduced into the fuel cell stack can be controlled. In particular, when the temperature is raised at the start of the fuel cell, the temperature can be controlled to a desired rate. Therefore, damage to the power generation cell due to rapid heating is avoided, so that the reliability of the fuel cell is improved. Furthermore, since a large heat source device is not required, an increase in the size of the fuel cell is suppressed.

  The fuel cell operating method according to an embodiment of the present invention further includes connecting a reducing gas introduction path for introducing a reducing gas into the reformer to the reformer, and at the time of starting the fuel cell. And introducing the reducing gas into the reformer. According to this configuration, the reducing gas can be introduced into the fuel cell stack via the reducing gas introduction path and the reformer. Therefore, the reforming catalyst and the power generation cell fuel electrode in the reformer at the time of temperature rise. Oxidation of the fuel cell prevents the fuel cell performance from deteriorating. Further, since the reducing gas can be further introduced into the combustor and used for the catalytic combustion reaction, it is possible to efficiently raise the temperature.

  The method for operating a fuel cell according to an embodiment of the present invention further includes heating the air preheater by causing the catalyst combustion reaction by heating the catalyst by the catalyst heater when the fuel cell is started up. And heating the fuel cell stack by heating the air using this heat. According to this configuration, the use of the combustion catalyst of the catalytic combustor eliminates the need for a large-scale heating device such as a startup burner for increasing the temperature at startup. Therefore, it is possible to raise the temperature of the fuel cell stack uniformly while further suppressing the increase in size of the entire fuel cell.

  As described above, according to the fuel cell and the operation method thereof according to the present invention, by providing a heating structure that uniformly heats the entire fuel cell stack at the time of startup, the fuel cell can be prevented from being enlarged. Reliability is improved.

1 is a perspective view showing a fuel cell according to a first embodiment of the present invention. It is the longitudinal cross-sectional view seen from the II-II direction of FIG. It is a block diagram which shows the structure of the fuel cell of FIG. It is a cross-sectional view showing the fuel cell of FIG. It is sectional drawing which shows the fuel cell which provided the external catalyst heater as a modification of the fuel cell of FIG. It is a block diagram which shows the fuel cell which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the fuel cell which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments.

  FIG. 1 is a perspective view showing a fuel cell 1 according to the first embodiment of the present invention. The fuel cell 1 is used as a power generator, and includes a fuel cell stack 3, a reformer 5, an air preheater 7, a combustor 9, and an air temperature control mechanism 11 as main components.

  As schematically shown in FIG. 2, which is a longitudinal sectional view seen from the II-II direction in FIG. 1, the fuel cell 1 is installed in a sealed high temperature chamber 13 surrounded by a heat insulating member described later. The fuel cell stack 3 is configured by laminating a plurality of flat rectangular parallelepiped power generation cells 15 that generate power by reacting fuel and air with a separator 17 in a direction X orthogonal to the main surface. Each power generation cell 15 is configured as a solid oxide fuel cell (SOFC) in which an electrolyte made of an ion conductive ceramic is interposed between a fuel electrode (anode) and an air electrode (cathode). As shown in FIG. 1, a stack adapter 19 is attached to the bottom of the fuel cell stack 3. In the stack adapter 19, gas flow paths for air, fuel, and exhaust fuel connected to the fuel cell stack 3 are provided. During power generation of the fuel cell 1, air and fuel are supplied to the fuel cell stack 3 through the air supply pipe 21 and the fuel supply pipe 23, and the fuel supplied to the fuel cell stack 3 passes through the exhaust fuel pipe 25. The exhausted fuel EF is discharged, and part or all of it is introduced into the combustor 9. The air supplied to the fuel cell stack 3 is discharged from the air electrode of the fuel cell stack 3 to the high temperature chamber 13 as exhaust air EA and introduced into the combustor 9.

During power generation of the fuel cell 1, fuel F containing water vapor is introduced into the reformer 5 from the outside through a fuel introduction pipe 27 that forms a fuel introduction passage. RF, such as H ₂ and CO, is generated. As the fuel F, methane, city gas, biogas, or the like can be used. Therefore, as shown in FIG. 2, the reformer 5 is filled with alumina balls carrying nickel, ruthenium or the like as the reforming catalyst 29. As the reforming catalyst 29, various metal particles generally used as a steam reforming catalyst can be used.

When the fuel cell 1 is started, as shown in FIG. 3, a reducing gas RG such as H ₂ or CO is introduced into the reformer 5 through a reducing gas introduction pipe 31. The reducing gas RG introduced into the reformer 5 at the time of temperature rise is sent to the stack adapter 19 through the fuel supply pipe 23, and then supplied to the power generation cell fuel electrode of the fuel cell stack 3, and further the exhausted fuel. It is supplied to the combustor 9 through the pipe 25.

  As described above, by supplying the reducing gas RG through the reducing gas introduction pipe 31 at the time of startup, the reforming catalyst 29 (FIG. 2) in the reformer 5 and the fuel electrode in the fuel cell stack 3 are supplied. It is possible to prevent nickel used for the oxidation from being oxidized. Thereby, the fall of the electric power generation characteristic and long-term reliability of the fuel cell 1 is suppressed.

  The air preheater 7 heats the air A introduced from the outside by the air blower 35 mainly by the heat generated in the combustor 9. More specifically, as shown in FIG. 4, the air preheater 7 includes an air chamber 37 into which air A from the outside is introduced, and a combustion gas chamber 39 provided adjacent to the air chamber 37. Have. High-temperature combustion gas BG from the combustor 9 is introduced into the combustion gas chamber 39, and the air A introduced into the air chamber 37 is heated by the heat of the combustion gas BG that has flowed into the combustion gas chamber 39.

  The air temperature control mechanism 11 shown in FIG. 3 controls the temperature of the air supplied to the fuel cell stack 3 by adjusting the flow rate of the air introduced into the air preheater 7. Specifically, the air temperature control mechanism 11 has two directions via an air introduction path 43 that introduces air from the air blower 35 and a three-way valve 45 that is activated by an electric motor at the downstream end of the air introduction path 43. And an air preheater side introduction path 47 and an air preheater bypass circuit 49 that are branched and connected to each other. The air preheater side introduction path 47 communicates with the stack adapter 19 via the air preheater 7 provided in the middle, while the air preheater bypass 49 is directly connected to the stack adapter without passing through the air preheater 7. 19 communicates. The air A introduced from the air blower 35 is combined with the high-temperature air HA heated by the air preheater 7 and the unheated low-temperature air LA that has passed through the air preheater detour circuit 49 to become the heated air PHA. After being sent to the stack adapter 19 via the air supply pipe 21, it is supplied to the air electrode of the power generation cell 15 of the fuel cell stack 3.

  The flow rate ratio of the high-temperature air HA heated by the air preheater 7 and the flow rate of the low-temperature air LA bypassing the air preheater 7 by adjusting the opening degree of the three-way valve 45 of the air temperature control mechanism 11 configured as described above. By adjusting this, it becomes possible to control the temperature of the heated air PHA supplied to the fuel cell stack 3 via the stack adapter 19. In the present embodiment, the three-way valve 45 is used as a mechanism for adjusting the flow rate ratio between the air flow rate passing through the air preheater side introduction path 47 and the air flow rate passing through the air preheater bypass 49, but the air preheater Any mechanism may be used as long as the flow rate ratio to the introduction path 47 and the air preheater bypass 49 can be adjusted.

  As shown in FIG. 1, at the time of start-up, the reducing gas RG discharged from the fuel electrode of the fuel cell stack 3 is introduced into the combustor 9 through the exhaust fuel pipe 25 that forms the exhaust fuel flow path. At the time of power generation, part or all of the exhaust fuel F discharged from the fuel electrode of the fuel cell stack 3 is introduced into the combustor 9 via the exhaust fuel pipe 25 that forms the exhaust fuel passage. At the end of the combustor 9 is provided an air introduction part 9a provided with punching metal, and at the time of temperature rise, the temperature rise air PHA discharged from the air electrode of the fuel cell stack 3 to the high temperature chamber 13 is introduced into the air. The exhaust air EA introduced into the combustor 9 via the part 9a and discharged from the air electrode of the fuel cell stack 3 to the high temperature chamber 13 during power generation is introduced into the combustor 9 via the air introduction part 9a. . The combustor 9 combusts the introduced reducing gas RG (at start-up) or exhaust fuel EF (at power generation) and heated air PHA (at start-up) or exhaust air EA (at power generation) to produce a high-temperature combustion gas. BG is generated. The combustion gas BG is discharged to the outside through the combustion gas chamber 39 of the air preheater 7 connected to the downstream end of the combustor 9.

  The combustor 9 of the present embodiment is a catalytic combustor that burns reducing gas RG (at startup) or exhaust fuel EF (at power generation) and heated air PHA (at startup) or exhaust air EA (at power generation) with a catalyst. As shown in FIG. 2, an alumina ball carrying palladium, platinum, or the like is filled therein as the combustion catalyst 51, as shown in FIG. Heat generated by the combustion in the combustor 9 is supplied into the fuel cell 1 and used for the reforming reaction in the reformer 5 and the heating of air in the air preheater 7 as described above.

  The combustor 9 includes an internal catalyst heater 53 for heating the combustion catalyst 51 when the fuel cell 1 is started. More specifically, as shown in FIG. 1, the internal catalyst heater 53 is upstream in the flow direction of the reducing gas RG and the preheated heated air PHA in the combustor 9, that is, the downstream portion of the air introduction portion 9a. It is provided in the vicinity. In the present embodiment, a heating wire heater is used as the internal catalyst heater 53, and the heating wire heater is connected to an external power source (not shown). However, the internal catalyst heater 53 can be accommodated in the combustor 9 and can heat the combustion catalyst 51 to a temperature required to cause a combustion reaction of the reducing gas RG and the heated air PHA. If it exists, it can be used without being limited to the heating wire heater. In this embodiment, the temperature required to cause the combustion reaction of the reducing gas RG and the heated air PHA is about 250 ° C.

  Thus, by providing the internal catalyst heater 53 in the combustor 9 and using the combustion catalyst 51 of the combustor 9, a large-scale heating device such as a start burner is provided for raising the temperature at start-up. Therefore, the enlargement of the entire fuel cell 1 can be suppressed.

  Hereinafter, the overall structure of the fuel cell 1 will be described. In the fuel cell 1, the air preheater 7 is formed integrally with the combustor 9, and the reformer 5 is formed integrally with the combustor 9 and the air preheater 7. That is, as shown in FIG. 1, the reformer 5, the air preheater 7 and the combustor 9 are integrated by being accommodated in a single unit housing 61 (FIG. 2). The stack surrounding unit 63 is formed. In the inner peripheral portion 63A of the stack surrounding unit 63, the reformer 5 occupies the position of one side in the plan view shown in FIG. 4, and the air chamber 37 of the air preheater 7 occupies the other three positions. On the other hand, in the outer peripheral portion 63B of the stack surrounding unit 63, the outer peripheral portion of the reformer 5 is formed by the combustor 9, and the outer peripheral portion of the air chamber 37 of the air preheater 7 is the combustion gas. It is formed as a combustion gas chamber 39 that forms a flow path.

  The reformer 5 and / or the air preheater 7 may be formed and arranged separately from the combustor 9, but the combustor 9 can be formed integrally as described above. The heat generated in is supplied to the reformer 5 and the air preheater 7 while suppressing heat dissipation loss.

  As shown in FIG. 2, the outer periphery 3 a of the fuel cell stack 3 is surrounded by a stack surrounding unit 63 with a predetermined spacing. In other words, the outer periphery 3 a of the fuel cell stack 3, that is, the four side surfaces of the fuel cell stack 3 having a substantially rectangular parallelepiped shape parallel to the stacking direction X of the power generation cells 15, Either the reformer 5 or the air preheater 7 forming the inner peripheral portion 63A is disposed. As shown in FIG. 1, the stack surrounding unit 63 is entirely composed of a fuel supply pipe 23 connecting the stack adapter 19 and the stack surrounding unit 63, piping such as an air supply pipe 21, and metal attached to the stack adapter 19. The fuel cell stack 3 is supported by a support member 65 made of a material.

  As described above, the reformer 5 and the air preheater 7 are arranged so as to face the fuel cell stack 3, so that the fuel cell 3 is introduced from the inside by the heated air introduced into the fuel cell stack 3 at the time of startup. In addition to being heated, the fuel cell stack 3 can be heated from the outside using the radiant heat from the reformer 5 and the air preheater 7 heated by the heat of the combustor 9. In particular, in the present embodiment, the central portion 60% or more of the four side surfaces (outer peripheral surfaces) of the fuel cell stack 3 in the stacking direction X is disposed so as to face the reformer 5 and the air preheater 7. Therefore, the fuel cell stack 3 can be heated extremely uniformly in the stacking direction (vertical direction) X. In order to uniformly heat the fuel cell stack 3, the combustor 9 may be disposed so as to directly face the fuel cell stack 3 instead of the reformer 5 or the air preheater 7.

  The stack surrounding unit 63 is formed, for example, by joining a partition plate 67 made of the same material by welding or the like inside a unit housing 61 formed of a metal plate having corrosion resistance such as stainless steel. Yes. That is, the combustor 9 and the reformer 5 share the unit housing 61 and are adjacent to each other through only one partition plate 67. Similarly, the combustor 9 and the air preheater 7 share the unit housing 61 and are adjacent to each other through only the partition plate. By having such a structure, it is possible to transfer heat from the combustor 9 to the reformer 5 and the air preheater 7 while minimizing heat loss. The material forming the stack surrounding unit 63 is not limited to stainless steel, and may be appropriately selected in consideration of mechanical strength, corrosion resistance, thermal conductivity, and the like. Further, the structure of the stack surrounding unit is not limited to the example shown in FIG. 2, and can be appropriately selected in consideration of mechanical strength and assemblability.

  As shown in FIG. 4, the fuel cell 1 is installed in a high temperature chamber 13 formed by a heat insulating member 69 that covers the outside with a sealed structure. As the heat insulating member 69, a general heat insulating material such as glass wool can be used.

  According to the fuel cell 1 according to the present embodiment, when the fuel cell 1 is started, the preheated air PHA and the reducing gas RG enter the combustor 9 and a combustion reaction is caused by the internal catalyst heater 53 at about 250 ° C. And the reducing gas RG starts to burn on the combustion catalyst. When combustion starts, combustion continues independently and continuously, so the internal catalyst heater 53 is stopped. The reformer 5 is heated by the generated combustion heat, and the high-temperature combustion gas BG exiting the combustor 9 enters the air preheater 7 and heats the air A. The high-temperature air HA heated by the air preheater 7 joins the low-temperature air LA that bypasses the air preheater 7 to become the heated air PHA, and then enters the fuel cell stack 3 to bring the fuel cell stack 3 from the inside. Heat. At that time, the flow rate ratio between the high temperature air HA and the low temperature air LA is controlled by the air temperature control mechanism 11 so that the temperature of the heated air PHA increases linearly with time. Further, the fuel cell stack 3 is heated from the outside by the radiant heat of the heated reformer 5 and air preheater 7. The fuel cell stack 3 is heated from the inside and the outside, and is heated to about 600 to 700 ° C. by controlling the amount of air, the amount of reducing gas, and the mixing ratio.

  As described above, according to the fuel cell 1 according to the present embodiment, the fuel cell stack 3 can be heated from the inside using the air preheater 7 even when the temperature of the fuel cell 1 is started up. By providing the air temperature control mechanism 11, the temperature of the air introduced into the fuel cell stack 3 can be controlled. In particular, when the temperature is increased when the fuel cell 1 is started, the temperature can be controlled to a desired temperature increase rate. Therefore, damage to the power generation cell 15 due to rapid heating is avoided, so that the reliability of the fuel cell 1 is improved. Furthermore, since a large heat source device is not required, an increase in the size of the entire fuel cell 1 is suppressed.

  Instead of providing the internal catalyst heater 53 inside the combustor 9, or in addition to the internal catalyst heater 53, as a modification of the first embodiment, as shown in FIG. An external catalyst heater 71 can also be provided. Specifically, a heating wire heater is provided as an external catalyst heater 71 in a heater housing 73 that is disposed outside the combustor 9 and is filled with ceramic balls 51 such as alumina balls that come into contact with the combustor 9. The ceramic ball 51 is heated by energizing the heating wire heater, and the combustion catalyst 51 in contact with the external catalyst heater of the combustor 9 is preheated. Here, the ceramic balls 51 are taken as an example of the filler in the heater housing 73, but any filler that can increase the heat capacity of the heater housing 73 may be used.

  Further, instead of providing the internal catalyst heater 53 as a preheating method for the combustor 9, combustible gas CF is introduced into the combustion gas chamber 39 of the air preheater 7 as in the second embodiment shown in FIG. A combustible gas igniter 79 for combusting the combustible gas CF may be provided in the combustion gas chamber 39 by connecting the gas introduction path 77. In the case of this embodiment as well, it is not necessary to provide a large heating device such as a burner for preheating the combustor 9 at the time of start-up, and therefore the enlargement of the entire fuel cell 1 can be suppressed. As the combustible gas CF introduced into the combustion gas chamber 39 in the present embodiment, for example, a gas similar to the fuel of the fuel cell 1 such as methane or city gas can be used. Moreover, as the combustible gas igniter 79, for example, an ignition device such as a spark plug can be used. The combustion of the combustible gas CF heats the air preheater 7 and further the air A, thereby heating the stack. The air PHA exiting the stack preheats the combustor 9 to about 250 ° C.

  Further, as in the third embodiment shown in FIG. 7, a small pilot burner 81 is provided to burn the air blower 83 and the burner fuel BF to generate the hot gas HG, and the hot gas HG is sent into the hot chamber 13. A method of preheating the combustor 9 is also conceivable. In any method, as in the case of the first embodiment, when the reducing gas RG starts burning, the preheating of the combustor 9 is stopped.

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention. Therefore, such a thing is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel cell 3 Fuel cell stack 5 Reformer 7 Air preheater 9 Combustor 11 Air temperature control mechanism A Air HA High temperature air LA Low temperature air PHA Heated air EA Exhaust air F Fuel RF Reformed fuel EF Exhaust fuel RG Reducibility gas

Claims (10)

A fuel cell stack formed by stacking a plurality of power generation cells that generate electricity by reacting fuel and air;
A combustor that generates heat by burning exhaust fuel and exhaust air discharged from the fuel cell stack;
A reformer that generates reformed fuel by steam reforming the fuel introduced from the outside using heat generated in the combustor, and supplies the reformed fuel to the fuel cell stack;
An air preheater that heats air introduced from the outside by heat generated by the combustor and supplies the air to the fuel cell stack;
The flow rate of the air heated by the air preheater and the flow rate of the air introduced directly into the fuel cell stack bypassing the air preheater are adjusted to be supplied to the fuel cell stack. An air temperature control mechanism for controlling the temperature of the air;
Equipped with a,
A fuel cell , wherein a combustible gas introduction path for introducing a combustible gas is connected to the air preheater, and a combustible gas igniter for combusting the combustible gas is provided in the air preheater . A fuel cell stack formed by stacking a plurality of power generation cells that generate electricity by reacting fuel and air;
A combustor that generates heat by burning exhaust fuel and exhaust air discharged from the fuel cell stack;
A reformer that generates reformed fuel by steam reforming the fuel introduced from the outside using heat generated in the combustor, and supplies the reformed fuel to the fuel cell stack;
An air preheater that heats air introduced from the outside by heat generated by the combustor and supplies the air to the fuel cell stack;
The flow rate of the air heated by the air preheater and the flow rate of the air introduced directly into the fuel cell stack bypassing the air preheater are adjusted to be supplied to the fuel cell stack. An air temperature control mechanism for controlling the temperature of the air;
With
The fuel cell stack is formed by stacking a plurality of flat rectangular parallelepiped power generation cells, and the reformer, the air preheater, and the combustor have a rectangular tube-shaped stack surrounding unit that surrounds the outer periphery of the battery stack. Forming a fuel cell. 3. The fuel cell according to claim 1 , further comprising a reducing gas introduction path that is connected to the reformer and introduces a reducing gas into the reformer. 4. The fuel cell according to claim 1 , wherein the air preheater is disposed to face at least a part of a side surface of the fuel cell stack. 5. The combustor according to any one of claims 1 to 4 , wherein the combustor is a catalytic combustor that burns the exhaust fuel and exhaust air by a catalyst, and causes a catalytic combustion reaction by the catalyst inside or outside the combustor. A fuel cell provided with a catalyst heater for heating to a temperature required for the above.   The fuel cell according to any one of claims 1 to 5, wherein the combustor and at least one of the reformer and the air preheater are integrally formed. A method of operating a fuel cell according to any one of claims 1 to 6 ,
A flow rate of air flowing into the fuel cell stack after being heated by the air preheater by the air temperature control mechanism, and a flow rate of air introduced directly into the fuel cell stack bypassing the air preheater. A method of operating a fuel cell, comprising controlling a temperature of air introduced into the fuel cell stack by adjusting a flow rate ratio. 8. The reformer according to claim 7 , further comprising a reducing gas introduction path for introducing a reducing gas into the reformer, and the reducing gas is supplied to the reformer when the fuel cell is started. A method for operating a fuel cell, comprising introducing the fuel cell into the inside. In claim 7 or 8 which refers to claim 5, when starting the fuel cell, heat is supplied to the air preheater by heating the catalyst by the catalyst heater to cause a catalytic combustion reaction. A method of operating a fuel cell, comprising preheating the fuel cell stack by heating the air using this heat. A fuel cell stack formed by stacking a plurality of power generation cells that generate electricity by reacting fuel and air;
A combustor that generates heat by burning exhaust fuel and exhaust air discharged from the fuel cell stack;
A reformer that generates reformed fuel by steam reforming the fuel introduced from the outside using heat generated in the combustor, and supplies the reformed fuel to the fuel cell stack;
An air preheater that heats air introduced from the outside by heat generated by the combustor and supplies the air to the fuel cell stack;
The flow rate of the air heated by the air preheater and the flow rate of the air introduced directly into the fuel cell stack bypassing the air preheater are adjusted to be supplied to the fuel cell stack. An air temperature control mechanism for controlling the temperature of the air;
With
A catalyst combustor in which the combustor burns the exhaust fuel and exhaust air with a catalyst, and the catalyst heats the catalyst to a temperature required to cause a catalytic combustion reaction by the catalyst inside or outside the combustor. A method of operating a fuel cell provided with a heater,
A flow rate of air flowing into the fuel cell stack after being heated by the air preheater by the air temperature control mechanism, and a flow rate of air introduced directly into the fuel cell stack bypassing the air preheater. Controlling the temperature of the air introduced into the fuel cell stack by adjusting the flow rate ratio;
At the time of starting the fuel cell, the catalyst is heated by the catalyst heater to cause a catalytic combustion reaction to supply heat to the air preheater, and the air is heated by using the heat. Preheating the fuel cell stack ;
After the catalytic combustion has started, stopping the catalyst heater;
A method for operating a fuel cell including:

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