JP2008251493A - Fuel cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell module excellent in preheat and heat absorption. <P>SOLUTION: The fuel cell module is equipped with two or more stacks 2 formed by stacking unit cells; a reformer 4 reforming fuel gas to be supplied to the stacks 2; a fuel preheater 3 preheating fuel gas supplied to the reformer 4; and a heat exchanger 14 preheating air supplied to the stacks 2, two or more stacks 2 are arranged on almost the circumference of a circle, and the reformer 4 and the fuel preheater 3 are arranged on the inside of the circumference of the circle, and the heat exchanger 14 is arranged on the outside of the circumference of the circle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell module in which heat generated from a stack is used to preheat fuel gas and air, and in particular, in addition to improving stack performance by equalizing gas supply and reducing temperature gradient, The present invention relates to a fuel cell module that enables high performance and low cost through effective use.

  Various types of fuel cells having different types depending on the type of electrolyte have been developed. One of them is a solid oxide fuel cell (SOFC) characterized by operating at a high temperature of about 1000 ° C. is there. A solid oxide fuel cell has a flat type stack by stacking a large number of flat type single cells each comprising a solid electrolyte plate and electrode layers laminated on each surface of the solid electrolyte plate via a gas separator. It is formed. Then, by supplying air and fuel gas to the stack, an electrochemical reaction occurs in the cell and electric energy is generated. Electric energy generated in the stack is collected and taken out to the outside through the output terminal.

In such an SOFC, since the cell is formed using ceramics, the operating temperature is high, and it is necessary to feed the supplied fuel gas and air in a preheated state. This is because if the fuel gas or air having a low temperature is supplied into the stack operating at a high temperature, the ceramics may be damaged. Therefore, conventionally, a heat exchanger is provided in front of the stack, and fuel gas and air are supplied to the pipe through the heat exchanger so that the fuel gas and air are supplied into the stack in a preheated state. . Further, in this heat exchange action, the fuel gas and air absorb the heat generated in the module, thereby achieving a cooling effect.
JP-A-6-52881 JP 2005-78859 A

  However, the conventional fuel cell module configured using a plurality of stacks has the following problems. For example, depending on the preheating and heat absorption structure using a heat exchanger, heat generated by power generation may be trapped inside the module, which may adversely affect the stack and the like. That is, depending on the positional relationship between the heat exchanger and the plurality of stacks, some stacks may not be cooled in a well-balanced manner. In such a case, a temperature gradient is generated in the ceramic cells constituting the stack, and the cells may be destroyed by thermal stress caused by the temperature difference.

  In addition, depending on the piping structure for supplying preheated fuel gas and air, it is possible to distinguish between upstream and downstream in the arrangement of each stack, and in the downstream stack, the fuel used for power generation of the stack located upstream Will be supplied. As a result, the concentration of the fuel gas becomes lower in the stack on the downstream side, and the performance varies among the plurality of stacks. Since the fuel cell module configured by a plurality of stacks is operated in accordance with a low performance module, the performance of the entire module is lowered.

  Therefore, an object of the present invention is to provide a fuel cell module excellent in preheating and heat absorption in order to solve such problems.

  The fuel cell module of the present invention includes a plurality of stacks configured by stacking single cells, a reformer that reforms fuel gas supplied to the stack, and a fuel that preheats the fuel gas sent to the reformer. A preheater and a heat exchanger for preheating air supplied to the stack, wherein the plurality of stacks are arranged on a substantially circumference, and the reformer and the fuel preheater are arranged on the circumference. It is arranged inside, and the heat exchanger is arranged outside the circumference.

In the fuel cell module of the present invention, the plurality of stacks are arranged at equal intervals on the same circumference, the fuel preheater is provided in the cylindrical reformer, and is arranged at the center position of the circumference. It is preferable that
In the fuel cell module of the present invention, a gas chamber for storing the fuel gas sent out from the reformer is arranged inside a circumference where the stack is arranged, and a plurality of gas supplies extending radially from the gas chamber Preferably, the tube is connected to the stack.
In the fuel cell module of the present invention, the gas chamber is disposed at the center of the circumference with the stack disposed therein, and is connected to the stack by the gas supply pipe having an approximately equal length from the gas chamber. It is preferable.

The fuel cell module of the present invention is an air pipe spirally piped outside the stack where the heat exchanger is arranged substantially on the circumference, and is connected to an air supply pipe connected to each stack. It is preferable that
The fuel cell module of the present invention constitutes an airtight internal space that covers the stack, the fuel preheater, and the reformer, and the exhaust gas space formed in the ceiling through an exhaust gas space that is a double wall. It is preferable to have a container for exhausting combustion gas generated in the space, and the air pipe is spirally piped around the container.

In the fuel cell module of the present invention, a flow rate several times the theoretical reaction amount is sent to the heat exchanger, and the supply amount of air is changed in response to a change in the supply amount of fuel gas to the stack. Preferably there is.
In the fuel cell module of the present invention, it is preferable that the plurality of stacks are provided with a load plate applied from above over two or more stacks and provided with a bellows for applying a load to the load plate.
In the fuel cell module of the present invention, it is preferable that the current extraction terminals connected to the plurality of stacks are protruded outside from the internal space of the container and connected outside the container.

Therefore, according to the fuel cell module of the present invention, the plurality of stacks are arranged on the circumference and the heat exchanger is arranged on each of the inner side and the outer side. It can be effectively used for preheating air.
Further, according to the fuel cell module of the present invention, the fuel gas is uniformly supplied to the plurality of stacks by using a gas chamber or the like, and the structure of the plurality of stacks is made uniform by pressing with the bellows. By doing so, the performance difference of each stack is eliminated and the performance of the entire module is improved. And cost can be held down by using a load plate and pressing two or more stacks with one bellows.

Next, an embodiment of a fuel cell module according to the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing the internal structure of the fuel cell module, and FIG. 2 is a plan view of the main part thereof.
The fuel cell module 1 has a stack 2 in which a large number of flat single cells are stacked via gas separators, and six such stacks 2 are arranged on the same circumference. In the present embodiment, by supplying fuel gas and air to the six stacks 2, electric energy is extracted for each stack 2 by an electrochemical reaction in the cell.

  Each stack 2 is provided with a positive-side current extraction terminal 21 and a negative-side current extraction terminal 22, which are connected in series. In the present embodiment, six stacks 2 are arranged for the purpose of generating 5 kilowatts of power. Although an output of about 1 kilowatt can be expected per stack 2, the fuel cell module 1 uses a blower or the like for supplying air as will be described later. Six stacks 2 are provided. Note that the number and specifications of the stacks 2 shown in this embodiment are merely examples.

  The six stacks 2 are arranged at equal intervals on the same circumference, and a fuel preheater 3 and a reformer 4 are arranged at the center position. The fuel preheater 3 is provided in the donut-shaped reformer 4 and is configured such that fuel gas is fed from below. That is, the fuel preheater 3, the reformer 4, and the stack 2 are fixed on the base plate 5, and a fuel gas pipe 11 piped under the base plate 5 is connected to the fuel preheater 3. The fuel preheater 3 has a flow path formed therein, and the fuel gas flowing so as to rise there receives heat from the heated preheater body.

  The fuel preheater 3 and the reformer 4 are connected to each other at the upper part so that the preheated fuel gas flows in the reformer 4 around the fuel preheater 3 from top to bottom. . A reforming catalyst is placed in the reformer 4, and a reformed gas (such as hydrogen) can be obtained from a fuel gas (such as natural gas) by a reforming reaction. In the present embodiment, the heat generated from the stack 2 arranged on the same circumference is exchanged by flowing the fuel gas through the fuel preheater 3 and the reformer 4 arranged at the center position. Has been.

  That is, in order to efficiently use the heat generated in the plurality of stacks 2, the heat radiated from the plurality of stacks 2 arranged on the same circumference is absorbed by the fuel preheater 3 and the reformer 4 arranged in the center. It has a structure to do. The stack 2 during operation generates heat up to about 800 ° C., the reforming reaction is performed at about 600 ° C., and the preheating by the fuel preheater 3 may be less than that. Therefore, since the fuel preheater 3 is provided in the reformer 4 and the reforming reaction is also an endothermic reaction, the heat exchange between the stack 2 and the reformer 4 is further promoted by such a structure and arrangement. It is configured as follows.

  In the reformer 4, a discharge pipe 12 that discharges the reformed reformed gas passes through the base plate 5 and is connected to the lower gas chamber 6. In this embodiment, the reformed gas reformed via the reformer 4 is not directly supplied to each stack 2 but is once stored in the gas chamber 6 and then sent to each stack 2. . Therefore, the gas chamber 6 is disposed immediately below the reformer 4 and is connected by a discharge pipe 12. Here, FIG. 3 is a plan view conceptually showing the piping structure of the fuel cell module 1.

  The gas chamber 6 is arranged at the center of the stacks 2 arranged on the same circumference, and is connected to each of the six stacks 2 by six gas supply pipes 13 extending radially from the center position. The stack 2 has a flow path through which fuel gas and air flow. If an error occurs between the stacks, the pressure loss of the reformed gas flowing therethrough varies. In such a case, if the reformed gas is directly fed from the reformer 4 to the six stacks 2, it becomes difficult for the reformed gas to flow through the stack 2 having a large pressure loss, resulting in a difference in performance between the stacks. . Therefore, in this embodiment, by providing the gas chamber 6 having a larger capacity than the flow path of the stack 2 and lowering the supply pressure to the stack 2, the reformed gas can be evenly distributed even if there is a difference in pressure loss. It is made to flow.

  Next, the air supplied to the stack 2 is also preheated, and the air is configured to flow outside the stack 2 arranged on the same circumference. That is, the fuel gas cools the inside of the stack 2 by exchanging heat through the fuel preheater 3 and the reformer 4 provided at the central position, but the air flows outside the circumference and exchanges heat. Thus, the outside of the stack 2 is cooled. Specifically, the container 7 is fixed on the base plate 5 so as to surround the stack 2, the fuel preheater 3, and the reformer 4, and an air pipe 14 through which air flows is wound around the container 7. Here, FIG. 4 is a diagram conceptually showing the structure of the container 7.

  The container 7 is a cylindrical casing formed by a double-structured wall 31, and the stack 2, the fuel preheater 3 and the reformer 4 are arranged inside to form an airtight space. An exhaust port 32 is formed in the ceiling, and the double wall 31 is formed with an exhaust gas space 33 in which combustion gas burned in the container 7 enters from the exhaust port 32 and flows along the wall 31. About 80% of the fuel supplied to the stack 2 is used for power generation, but the rest of the fuel is discharged without being used. In addition, since part of the supplied air is also discharged from the stack 2, the fuel gas and air discharged together are mixed and burned in the atmosphere in the high-temperature container 7. The exhaust gas space 33 is a structure for discharging the combustion gas in the container 7, and the combustion gas pushed out by the pressure in the container 7 is exhausted from the exhaust pipe 34.

  Therefore, the high-temperature exhaust gas burned flows into the exhaust gas space 33, and the high-temperature heat generated from the stack 2 is also radiated outward, so that the container 7 is heated. Therefore, a spiral air pipe 14 is provided around the container 7 so as to flow from top to bottom, and the air flowing through the air pipe 14 is preheated by heat exchange to cool the outside of the stack 2. . The air pipe 14 penetrates the base plate 5 so that preheated air is sent from the lower side of each stack 2.

  Under the base plate 5, as shown in FIG. 3, an arcuate air supply pipe 15 is provided so as to pass under each stack 2, and is connected directly to each stack 2. The air pipe 14 is connected to the arcuate air supply pipe 15 at the center position. Therefore, the air supply to each stack 2 is different in distance from the air pipe 14 depending on the connection position with the air supply pipe 15 unlike the fuel gas. However, in the case of air, since a flow rate of 2 to 3 times the theoretical reaction amount is flowed into the stack 2, even if a pressure loss difference occurs, the performance between the stacks is not affected.

  Also, supplying a large flow of air is effective for adjusting the temperature in the container 7 because the cooling effect is enhanced. In the solid oxide fuel cell, since the flat plate-type cells constituting the stack 2 are ceramics, the cells may be damaged by thermal stress when a temperature gradient occurs. For this reason, in the case of performing an endothermic action on the inside and the outside of the stack 2 arranged on the same circumference, it is necessary to balance both. In this regard, in the present embodiment, a balance with the inside is achieved by flowing a large amount of air to the outside. Furthermore, if the power generation capacity changes depending on the amount of power used, the fuel gas supply will also vary. To change the heat absorption balance between the inside and the outside.

  Next, in the solid oxide fuel cell, the stack 2 is configured by stacking a large number of flat plate type single cells. However, since the cells are formed of ceramics, they are stacked only by overlapping. The adhesion between the cell and the separator is not good. If the adhesion is not good, the contact resistance is increased and the performance of the stack 2 is lowered. Therefore, in the present embodiment, a configuration is adopted in which the cells are brought into close contact with each other by being pressed against the stack 2 from above.

  A bellows 25 is used as a pressing means for pressing the stack 2. The bellows 25 is disposed between the stack 2 and the ceiling of the container 7 and presses the stack 2 with the supplied air pressure. However, since it is costly to provide the bellows 25 in each of the six stacks 2, a plate is placed on the stack 2, and the load from the bellows 25 is transmitted through the plate. In such a case, if there is a slight error in the height of the stack 2, it is difficult to apply an equal load to all the six pieces even if they are to be pressed by one plate.

  Therefore, in the present embodiment, as shown in FIG. 5, a home base type load plate 26 corresponding to the three stacks 2 is applied via an insulating plate 27 (see FIG. 1), and the bellows 25 is formed thereon. It is arranged so as to almost hit the center of gravity. In addition to this configuration, as shown in FIG. 6, an insulating load bar 29 is fixed to each apex portion of the triangular load plate 28, and two stacks 2 are directly pressed by the load bar 29. Alternatively, the entire stack 2 may be pressed by the load plate 28 indirectly. In this case, all the stacks 2 can be pressed by one bellows 25 while being divided into two stacks 2.

  As described above, the bellows 25 is used as the pressing means in order to keep the pressing load of the stack 2 constant. Therefore, in this embodiment, although not shown in detail, the fluid circuit that manages the pressure of the air supplied to the bellows 25 is provided, and the stack 2 is pressed down with a set load value. On the other hand, as the pressing means, a spring or the like can be used in addition to the bellows. However, in a spring, the spring constant changes at high temperatures, making it difficult to adjust the pressing pressure, and it is difficult to generate a target load. Then, if the load changes, the manner of contact with the cell also changes, affecting the performance of the stack 2, and if the load is large, the cell is damaged.

  Next, the fuel cell module 1 is configured such that the current extraction terminals 21 and 22 of each stack 2 are alternately connected in series so as to obtain a predetermined power. The current extraction terminals 21 and 22 are connected to the base plate 5. It is configured to penetrate and connect outside the container 7. This is because the inside of the container 7 has a high temperature of about 800 ° C., so that the materials that can be used for the connection member are limited in the main body. In addition, by connecting outside the container 7, even if a failure occurs in one of the plurality of stacks 2, switching is easy, and the operation can be continued except for the failure.

  Furthermore, as shown in FIG. 1, the fuel cell module 1 has a base plate 5 mounted on a mount 35 and a space for piping the pipes below. Further, the whole is covered with a housing 36, and a heat insulating material is put between the container 7. In FIG. 1, the base plate 5 is configured to be released, but is closed with a lower lid containing a heat insulating material so as not to cool the preheated fuel gas and air.

In the fuel cell module 1 of the present embodiment configured as described above, it is necessary to generate combustion gas using a start burner at the time of start-up, and to raise the temperature to a temperature at which fuel cell power generation can be started. The operation is performed by the heat generated by.
During operation, fuel gas and air are sent to the stack 2, and fuel is supplied to the fuel electrode side and air is supplied to the air electrode side across the solid electrolyte, respectively, and electric power is taken out by an electrochemical reaction. At that time, the stack 2 generates heat as power is generated, and the fuel gas and air discharged from the stack 2 are mixed and burned in the container 7.

  The heat and combustion gas released from the stack 2 heats the fuel preheater 3 and the reformer 4 at the center, and the wall 31 of the outer container 7 radiates heat and combustion gas through the exhaust gas space 33. Heated by passing. Under such circumstances, the fuel gas fed from the fuel gas pipe 11 rises in the heated fuel preheater 3 and is preheated, flows into the reformer through the upper communication channel, and is converted into hydrogen by the reforming reaction. Reformed. Thereafter, the reformed gas is once stored in the gas chamber 6 having a large capacity, and sent to the six stacks 2 through the gas supply pipes 13 extending radially. On the other hand, the air sent to the air pipe 14 is preheated by flowing along the wall 31 of the heated container 7 and sent from the air supply pipe 15 to each stack 2.

  Therefore, in the present embodiment, the fuel preheater 3 and the reformer 4 are arranged at the center position where the plurality of stacks 2 are arranged in a circle, the exhaust gas space 33 and the air pipe 14 are arranged outside, and the inside and outside Since the heat exchanger is arranged in each of the above, the heat generated from the stack 2 can be effectively used for preheating fuel gas and air. Further, since the stack 2 is cooled in a well-balanced manner by endothermic reactions from both the inner side and the outer side, it has an effect of preventing the occurrence of thermal stress and avoiding cell damage. In particular, since the supply amount of air can be adjusted, cell damage due to thermal stress can be further avoided by balancing the heat absorption between the inside and the outside of the stack 2.

  Further, since the fuel gas preheated through the reformer 4 is sent to each stack 2 by the gas supply pipes 13 of substantially equal length extending radially through the gas chamber 6, a plurality of stacks 2 are provided. Even if there is a pressure loss difference between the two, the fuel gas with substantially the same flow rate can be flowed. For this reason, it is possible to eliminate the difference in performance for all the stacks 2 or to reduce the difference, and to improve the performance of the entire module.

  Moreover, in this embodiment, the load by the bellows 25 is applied to each stack 2, and the contact resistance of a cell and a separator is reduced, and a performance fall is avoided. Therefore, the configuration of the plurality of stacks 2 is made uniform, and this also eliminates the performance difference and improves the performance of the entire module. In that case, the number of bellows 25 can be reduced by using the load plates 26 and 28, and the cost is suppressed. In the bellows 25, the stack 2 can be stably pressed with a predetermined load value by controlling the internal pressure.

  Furthermore, in the fuel cell module 1 of the present embodiment, the current extraction terminals 21 and 22 protrude from the base plate 5 and are connected outside the container 7, so that the selection of materials that can be used for the connection member is widened. Even if a failure occurs in one of the plurality of stacks 2, switching is easy, and the operation can be continued except for the failure.

  As mentioned above, although one embodiment was described about fuel cell module 1 concerning the present invention, the present invention is not limited to this but various changes are possible in the range which does not deviate from the meaning.

It is the conceptual diagram which showed the internal structure about one Embodiment of the fuel cell module. It is the top view which showed the principal part about one Embodiment of a fuel cell module. It is the top view which showed notionally the piping structure about one Embodiment of the fuel cell module. It is the figure which showed the structure of the container conceptually. It is the top view which showed the press state of the stack by the load plate in the case of two bellows. It is the top view which showed the pressing state of the stack by the load plate in the case of one bellows.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell module 2 Stack 3 Fuel preheater 4 Reformer 6 Gas chamber 7 Container 11 Fuel gas pipe 13 Gas supply pipe 14 Air pipe 15 Air supply pipe 25 Bellows 26 Load plate 33 Exhaust gas space

Claims (9)

A plurality of stacks configured by stacking single cells, a reformer for reforming fuel gas supplied to the stack, a fuel preheater for preheating fuel gas to be sent to the reformer, and supplying the stack In a fuel cell module having a heat exchanger for preheating air,
The plurality of stacks are arranged on a substantially circumference, the reformer and the fuel preheater are arranged inside the circumference, and the heat exchanger is arranged outside the circumference. A fuel cell module. The fuel cell module according to claim 1, wherein
The plurality of stacks are arranged at equal intervals on the same circumference, the fuel preheater is provided in the cylindrical reformer, and is arranged at the center position of the circumference. Fuel cell module. In the fuel cell module according to claim 1 or 2,
A gas chamber for storing fuel gas sent out from the reformer is disposed inside a circumference where the stack is disposed, and is connected to the stack by a plurality of gas supply pipes extending radially from the gas chamber. A fuel cell module characterized by being a thing. The fuel cell module according to claim 3, wherein
The gas chamber is disposed at a central position of a circumference where the stack is disposed, and is connected to the stack by the gas supply pipe having a substantially equal length from the gas chamber. Battery module. The fuel cell module according to any one of claims 1 to 4, wherein
The heat exchanger is an air pipe spirally piped outside the stack disposed substantially on the circumference, and is connected to an air supply pipe linked to each stack. Fuel cell module. The fuel cell module according to claim 5, wherein
An airtight internal space that covers the stack, the fuel preheater, and the reformer is configured, and the combustion gas generated in the internal space is exhausted from an exhaust port formed in the ceiling through an exhaust gas space that is a double wall. A fuel cell module, comprising: a container configured to be configured, wherein the air pipe is spirally piped around the container. The fuel cell module according to any one of claims 1 to 6,
A fuel cell characterized in that a flow rate several times the theoretical reaction amount is sent to the heat exchanger, and the supply amount of air is changed in response to a change in the supply amount of fuel gas to the stack. module. The fuel cell module according to any one of claims 1 to 7,
The fuel cell module, wherein the plurality of stacks are provided with a load plate applied from above over two or more stacks and provided with a bellows for applying a load to the load plate. The fuel cell module according to claim 6, wherein
The fuel cell module according to claim 1, wherein the current extraction terminals connected to the plurality of stacks protrude outward from the internal space of the container and are connected outside the container.

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