JP2022054696A - Solid oxide fuel cell - Google Patents

Abstract

To provide a solid oxide fuel cell with low radiation loss, capable of keeping the inside of a storage housing at a high temperature.SOLUTION: A solid oxide fuel cell includes a reformer 11, a cell stack CS and a combustion part 14 in an internal space S of a storage housing 1. The storage housing 1 has a multilayer structure part M where a plurality of wall materials w are arranged in layers at intervals from each other so that a plurality of spaces separated by the wall materials w are provided. At the multilayer structure part M, exhaust gas containing flue gas generated in the combustion part 14 and air supplied to the cell stack CS and the combustion part 14 flow in the plurality of spaces separately, so that heat exchange between the exhaust gas and the air is performed through the wall materials w. The solid oxide fuel cell is formed such that heat insulation effects by an external heat insulating material Hout provided on the outer face of the multilayer structure part M of the storage housing 1 become higher in a region where temperatures of the multilayer structure part M are higher.SELECTED DRAWING: Figure 2

Description

The present invention includes a storage housing, an internal heat insulating material provided on the inner surface of the storage housing, and an external heat insulating material provided on the outer surface of the storage housing, and an internal space inside the internal heat insulating material of the storage housing. In addition, a reformer that steam reforms raw fuel to generate fuel gas, a cell stack having a plurality of fuel cell cells that generate power using the fuel gas generated by the reformer, and a cell stack that is discharged from the cell stack. The present invention relates to a solid oxide fuel cell including a combustion unit that burns off-gas and applies the heat of combustion to the reformer.

Conventionally, a solid oxide fuel cell (SOFC (Solid Oxide Fuel Cell)) having a solid oxide cell stack using a solid electrolyte as a film for conducting oxide ions has been known. One of the main uses of such solid oxide fuel cells is a home-use cogeneration system. A cogeneration system using solid oxide fuel cells can generate electricity with high power generation efficiency comparable to that of large thermal power plants while meeting the demand for hot water supply and heating for household use.

In this solid oxide fuel cell, the cell stack is configured by stacking a plurality of fuel cell cells, and a fuel electrode for oxidizing fuel gas is provided on one side of the solid electrolyte in each fuel cell, and the others. An oxygen electrode for reducing oxygen in the air (oxidizing agent gas) is provided on the surface side. The operating temperature of the fuel cell of this solid oxide fuel cell is as high as about 600 ° C to about 800 ° C, and under such high temperatures, hydrogen, carbon monoxide, and hydrocarbons in the fuel gas (reformed fuel gas) Power is generated by an electrochemical reaction between hydrogen and oxygen in the air.

FIG. 12 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2007-59377) includes a storage housing, an internal heat insulating material provided on the inner surface of the storage housing, and an external heat insulating material provided on the outer surface of the storage housing. In the internal space inside the internal heat insulating material of the storage housing, a reformer that steam-reforms raw fuel to generate fuel gas, and a plurality of reformers that generate power using the fuel gas generated by the reformer. A cell stack having a fuel cell and a combustion unit that burns off gas discharged from the cell stack and gives the combustion heat to the reformer have been proposed.

Japanese Unexamined Patent Publication No. 2007-59377

Since the cell stack of a solid oxide fuel cell operates at a high temperature of about 600 ° C to about 800 ° C, it is necessary to keep the inside of the storage housing as high as possible. Therefore, it is necessary to surround the cell stack with a heat insulating material to suppress the amount of heat radiated from the cell stack, and to surround the storage housing with a heat insulating material. In addition, it is possible to preheat the air supplied to the inside of the storage housing by exchanging heat between the exhaust gas including the combustion exhaust gas generated in the combustion part and the air supplied to the cell stack and the combustion part. Will be. For example, in the configuration shown in FIG. 11 of Patent Document 1, the storage housing has a plurality of spaces separated by the wall materials by arranging a plurality of wall materials in layers at intervals from each other. It has a multi-layered structure portion, and in the multi-layered structure portion, the exhaust gas including the combustion exhaust gas generated in the combustion portion and the air supplied to the cell stack and the combustion portion are separately provided in the plurality of spaces. By flowing, heat exchange between the exhaust gas and the air is performed through the wall material.

As described above, some measures have been taken to keep the temperature inside the storage housing high, but further measures are required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a solid oxide fuel cell capable of keeping the inside of a storage housing at a high temperature and having a small heat dissipation loss.

The characteristic configuration of the solid oxide fuel cell according to the present invention for achieving the above object is provided on the storage housing, the internal heat insulating material provided on the inner surface of the storage housing, and the outer surface of the storage housing. Equipped with external insulation,
In the internal space inside the internal heat insulating material of the storage housing, a reformer that steam-reforms raw fuel to generate fuel gas and a fuel gas generated by the reformer are used to generate power. A solid oxide fuel cell including a cell stack having a plurality of fuel cell cells and a combustion unit that burns off gas discharged from the cell stack and applies the combustion heat to the reformer.
The storage housing has a multi-layered structure portion having a plurality of spaces separated by the wall materials by arranging the plurality of wall materials in a layered manner at intervals from each other.
In the multi-layered structure portion, the exhaust gas including the combustion exhaust gas generated in the combustion portion and the air supplied to the cell stack and the combustion portion flow separately into the plurality of spaces to obtain the exhaust gas. It is configured so that heat exchange with the air is performed through the wall material.
The heat insulating effect of the external heat insulating material provided on the outer surface of the multi-layered structure portion of the storage housing is formed so that the higher the temperature of the multi-layered structure portion, the higher the heat insulating effect.
Here, the thickness of the external heat insulating material provided on the outer surface of the multilayer structure portion of the storage housing from the outer surface of the multilayer structure portion is formed to be thicker in a region where the temperature of the multilayer structure portion is higher. May be good.

According to the above-mentioned characteristic configuration, since the high-temperature exhaust gas and the low-temperature air exchange heat in the multilayer structure portion, the temperature of the exhaust gas decreases due to the heat exchange with the air as it flows from the upstream side to the downstream side. As a result, the temperature of the multilayer structure portion is higher in the portion corresponding to the upstream side of the exhaust gas than in the portion corresponding to the downstream side. The heat insulating effect of the external heat insulating material provided on the outer surface of the multi-layered structure portion of the storage housing is formed so that the higher the temperature of the multi-layered structure portion, the higher the heat insulating effect. For example, the thickness of the external heat insulating material provided on the outer surface of the multilayer structure portion of the storage housing from the outer surface of the multilayer structure portion is formed to be thicker in a region where the temperature of the multilayer structure portion is higher. That is, heat dissipation from the high temperature region of the multilayer structure portion to the outside is effectively suppressed. As a result, the temperature drop of the internal space of the storage housing inside the multilayer structure portion is suppressed.
Therefore, the inside of the storage housing can be kept at a high temperature, and a solid oxide fuel cell having a small heat dissipation loss can be provided.

Another characteristic configuration of the solid oxide fuel cell according to the present invention is that the exhaust gas flows in the inner space and the air flows in the outer space in the multilayer structure portion.

According to the above-mentioned feature configuration, since the high temperature exhaust gas flows in the inner space in the multi-layered structure portion, the storage housing inside the multi-layered structure portion is larger than the case where the low temperature air flows in the same space. The temperature drop in the internal space of the is suppressed.

Yet another characteristic configuration of the solid oxide fuel cell according to the present invention is that the direction in which the exhaust gas flows and the direction in which the air flows face each other in the multilayer structure portion.

According to the above-mentioned characteristic configuration, in the multilayer structure portion, heat exchange between the exhaust gas and the air can be effectively performed while a large temperature difference between the exhaust gas and the air is secured.

Yet another characteristic configuration of the solid oxide fuel cell according to the present invention is that the heat insulating effect of the internal heat insulating material provided on the inner surface of the multi-layered structure portion of the storage housing is a region where the temperature of the multi-layered structure portion is high. It is formed so as to be as low as possible.
Here, the thickness of the internal heat insulating material provided on the inner surface of the multilayer structure portion of the storage housing from the inner surface of the multilayer structure portion is formed thinner as the temperature of the multilayer structure portion is higher. May be good.

According to the above characteristic configuration, the higher the temperature of the multilayer structure portion, the higher the heat insulating effect of the external heat insulating material is formed and the lower the heat insulating effect of the internal heat insulating material is formed. The heat insulating effect of the heat insulating material is formed low, and the heat insulating effect of the internal heat insulating material is formed high. For example, the higher the temperature of the multilayer structure portion, the thicker the external heat insulating material and the thinner the internal heat insulating material, and the lower the temperature of the multi-layered structure portion, the thinner the external heat insulating material and the internal heat insulating material. It is formed thick. As a result, the total thickness of the external heat insulating material and the internal heat insulating material provided on both sides of the multilayer structure portion can be made constant in the entire multilayer structure portion.

It is a figure which shows a plurality of devices installed in the internal space of a storage housing. It is a figure which shows the vertical cross section of a solid oxide fuel cell. It is a figure which shows the vertical cross section of a solid oxide fuel cell. It is a figure which shows the model of the computer simulation. It is a figure which shows the model of the computer simulation. It is a figure which shows the example of the multilayer structure part of another structure.

The solid oxide fuel cell according to the embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a plurality of devices installed in the internal space S of the storage housing 1. FIG. 2 is a diagram showing a vertical cross section of a solid oxide fuel cell. FIG. 3 is a diagram showing a vertical cross section of a solid oxide fuel cell.

The solid oxide fuel cell of the present embodiment includes a storage housing 1. The storage housing 1 is composed of a front structure 2, a back structure 3, a right side structure 4, a left side structure 5, a top surface structure 6, and a bottom surface structure 7. In the illustrated example, the front structure 2 and the back structure 3 face each other in the Z-axis direction. The right side structure 4 and the left side structure 5 face each other in the X-axis direction. The top structure 6 and the bottom structure 7 face each other in the Y-axis direction.

The solid oxide fuel cell is composed of a reformer 11 and a reformer 11 that generate fuel gas by steam reforming raw fuel in the internal space S inside the internal heat insulating material Hin of the storage housing 1. A cell stack CS having a plurality of fuel cell cells that generate power using the generated fuel gas, and a combustion unit 14 that burns the off gas discharged from the cell stack CS and gives the combustion heat to the reformer 11. Be prepared. In the internal space S, the reformer 11 and the combustion unit 14 are provided above the cell stack CS. A current take-out unit 20 is connected to the cell stack CS, and the current take-out unit 20 is pulled out from a portion of the bottom structure 7 of the storage housing 1 to the outside of the storage housing 1.

Inside the storage housing 1, a partition plate 8 for partitioning the internal space S into the upper internal space S1 and the lower internal space S2 is provided. The partition plate 8 has a ventilation hole 8a that allows gas to flow between the upper internal space S1 and the lower internal space S2. A cell stack CS and a heat exchange unit 16 are provided in the lower internal space S2. The reformer 11 and the combustion unit 14 are provided in the upper internal space S1.

The right side structure 4 has a first right side member 4a, a second right side member 4b, and a third right side member 4c in order from the outside to the inside of the storage housing 1. The first right side member 4a, the second right side member 4b, and the third right side member 4c are all plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, an oxidant gas (air) flows in the space between the first right side member 4a and the second right side member 4b, and in the space between the second right side member 4b and the third right side member 4c. Exhaust gas including combustion exhaust gas flows. As described above, the storage housing 1 has a multilayer structure portion M having a plurality of spaces separated by the wall material w by arranging the plurality of wall materials w in a layered manner at intervals from each other.

The left side structure 5 has a first left side member 5a, a second left side member 5b, and a third left side member 5c in order from the outside to the inside of the storage housing 1. The first left side member 5a, the second left side member 5b, and the third left side member 5c are all plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, the oxidant gas flows in the space between the first left side member 5a and the second left side member 5b, and the combustion exhaust gas flows in the space between the second left side member 5b and the third left side member 5c. Exhaust gas including flows.

The front structure 2 has a first front member 2a, a second front member 2b, and a third front member 2c in order from the outside to the inside of the storage housing 1. The first front member 2a, the second front member 2b, and the third front member 2c are all plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, the oxidant gas flows in the space between the first front member 2a and the second front member 2b, and the combustion exhaust gas flows in the space between the second front member 2b and the third front member 2c. Exhaust gas including flows.

The back structure 3 has a first back member 3a, a second back member 3b, and a third back member 3c in order from the outside to the inside of the storage housing 1. The first back surface member 3a, the second back surface member 3b, and the third back surface member 3c are all plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, the oxidant gas flows in the space between the first back surface member 3a and the second back surface member 3b, and the combustion exhaust gas flows in the space between the second back surface member 3b and the third back surface member 3c. Exhaust gas including flows.

The top surface structure 6 has a first top surface member 6a and a second top surface member 6b in order from the outside to the inside of the storage housing 1. The first top surface member 6a and the second top surface member 6b are both plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, the oxidant gas flows in the space between the first top surface member 6a and the second top surface member 6b.

The bottom surface structure 7 has a first bottom surface member 7a, a second bottom surface member 7b, and a third bottom surface member 7c in order from the outside to the inside of the storage housing 1. The first bottom surface member 7a, the second bottom surface member 7b, and the third bottom surface member 7c are all plate-shaped members (wall material w), and are arranged at intervals from each other. As will be described later, the oxidant gas flows in the space between the first bottom surface member 7a and the second bottom surface member 7b, and the combustion exhaust gas flows in the space between the second bottom surface member 7b and the third bottom surface member 7c. Exhaust gas including flows.

The solid oxide fuel cell includes an internal heat insulating material Hin provided on the inner surface of the storage housing 1 and an external heat insulating material Hout provided on the outer surface of the storage housing 1. For example, as shown in FIGS. 2 and 3, the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 of the storage housing 1 are not upright in the vertical direction but are inclined. It is provided. Then, an external heat insulating material Hout and an internal heat insulating material Hin are provided on the inclined portion.

The internal heat insulating material Hin has an internal front heat insulating material H1, an internal back heat insulating material H2, an internal right side heat insulating material H3, an internal left side heat insulating material H4, an internal upper heat insulating material H5, and an internal bottom side heat insulating material H6. Specifically, the internal upper heat insulating material H5 is provided in the upper internal space S1 above the partition plate 8. Then, the reformer 11 and the combustion unit 14 are installed in the space surrounded by the inner upper heat insulating material H5. In the lower internal space S2 below the partition plate 8, an internal front heat insulating material H1, an internal back heat insulating material H2, an internal right side heat insulating material H3, an internal left side heat insulating material H4, and an internal bottom side heat insulating material H6 are provided. Then, a cell stack CS or the like is installed in a space surrounded by the internal front heat insulating material H1, the internal back heat insulating material H2, the internal right side heat insulating material H3, the internal left side heat insulating material H4, and the internal bottom side heat insulating material H6.

The external heat insulating material Hout has an external front heat insulating material H7, an external back heat insulating material H8, an external right side heat insulating material H9, an external left side heat insulating material H10, an external upper heat insulating material H11, and an external lower heat insulating material H12. Specifically, the external front heat insulating material H7 is provided facing the outside of the front structure 2 of the storage housing 1, and the external back heat insulating material H8 faces the outside of the back structure 3 of the storage housing 1. The external right heat insulating material H9 is provided facing the outside of the right side structure 4 of the storage housing 1, and the external left side heat insulating material H10 is provided facing the outside of the left side structure 5 of the storage housing 1. The outer upper heat insulating material H11 is provided facing the outside of the top surface structure 6 of the storage housing 1, and the outer lower heat insulating material H12 is provided facing the outside of the bottom surface structure 7 of the storage housing 1. ..

The air supply pipe 18 and the exhaust pipe 19 are connected to the bottom structure 7 of the storage housing 1.
The oxidant gas (air) introduced into the storage housing 1 through the air supply pipe 18 first reaches the space between the first bottom surface member 7a and the second bottom surface member 7b. In the storage housing 1 of the present embodiment, the space between the first bottom surface member 7a and the second bottom surface member 7b is the space between the first front surface member 2a and the second front surface member 2b, and the first back surface. The space between the member 3a and the second back surface member 3b, the space between the first right side member 4a and the second right side member 4b, and the space between the first left side member 5a and the second left side member 5b. It is connected to all of the space. Further, the space between the first top surface member 6a and the second top surface member 6b is also the space between the first front surface member 2a and the second front surface member 2b, and the first back surface member 3a and the second back surface. Connected to all of the space between the member 3b, the space between the first right side member 4a and the second right side member 4b, and the space between the first left side member 5a and the second left side member 5b. There is.

As a result, the oxidant gas introduced into the space between the first bottom surface member 7a and the second bottom surface member 7b passes through the space between the first front surface member 2a and the second front surface member 2b. It reaches the space between the first top surface member 6a and the second top surface member 6b. The oxidant gas introduced into the space between the first bottom surface member 7a and the second bottom surface member 7b passes through the space between the first back surface member 3a and the second back surface member 3b, and is the first top surface. It reaches the space between the member 6a and the second top surface member 6b. The oxidant gas introduced into the space between the first bottom surface member 7a and the second bottom surface member 7b passes through the space between the first right side member 4a and the second right side member 4b, and is the first top surface. It reaches the space between the member 6a and the second top surface member 6b. The oxidant gas introduced into the space between the first bottom surface member 7a and the second bottom surface member 7b passes through the space between the first left side member 5a and the second left side member 5b, and is the first top surface. It reaches the space between the member 6a and the second top surface member 6b.

An introduced oxidant gas flow pipe 15 is connected to the second top surface member 6b, and the oxidant gas flowing in the space between the first top surface member 6a and the second top surface member 6b flows through the introduced oxidant gas. It is configured to flow into the tube 15. The introduced oxidant gas flow pipe 15 is installed in the internal space S of the storage housing 1 and functions to guide the oxidant gas to the inside of the cell stack CS. That is, the introduced oxidant gas flow pipe 15 is a cell stack in which the oxidant gas flowing in the space between the first top surface member 6a and the second top surface member 6b is installed in the internal space S of the storage housing 1. Lead to CS.

A water supply pipe 9 and a raw fuel gas supply pipe 10 are connected to the storage housing 1. The water supply pipe 9 and the raw fuel gas supply pipe 10 are connected to the reformer 11 installed in the upper internal space S1 to supply water and raw fuel gas to the reformer 11. In the reformer 11, the water supplied from the water supply pipe 9 is vaporized and the raw fuel gas is steam reformed to generate a fuel gas containing hydrogen as a main component. As will be described later, the combustion heat generated in the combustion unit 14 below the reformer 11 is transmitted to the reformer 11.

The introduced fuel gas flow pipe 12 is installed in the internal space S of the storage housing 1, and guides the fuel gas generated by the reformer 11 to the inside of the cell stack CS. In a plurality of solid oxide fuel cell cells possessed by the cell stack CS, power generation is performed by an electrochemical reaction between the supplied fuel gas and the oxidant gas. The discharged fuel gas, which is the fuel gas after being used in the electrochemical reaction, is discharged from the inside of the cell stack CS, and passes through the discharged fuel gas flow pipe 13 installed in the internal space S of the storage housing 1 to the combustion unit. Guided to 14. Further, the discharged oxidant gas, which is the oxidant gas after being used in the electrochemical reaction, is discharged from the inside of the cell stack CS and then installed in the internal space S of the storage housing 1. It flows through the distribution pipe 17.

The solid oxide fuel cell has a heat exchange unit 16 configured to exchange heat between the oxidant gas flowing through the introduced oxidant gas flow pipe 15 and the exhaust oxidant gas flowing through the exhaust oxidant gas flow pipe 17. To prepare for. The oxidant gas after heat exchange in the heat exchange unit 16 is supplied to the inside of the cell stack CS and used for the electrochemical reaction.

In the heat exchange unit 16, the oxidant gas and the discharged oxidant gas flow from the upper side to the lower side, and the oxidant gas flowing through the introduced oxidant gas flow pipe 15 and the oxidant gas discharged from the exhaust oxidant gas flow pipe 17. Exchanges heat with. As described above, the temperature of the oxidant gas supplied to the inside of the cell stack CS by the heat exchange in the heat exchange unit 16 is close to the temperature inside the cell stack CS (the temperature of the discharged oxidant gas), and is higher than that. Also becomes low temperature. As a result, heat can be taken out from the inside of the cell stack CS by the oxidant gas supplied to the inside of the cell stack CS.

Further, if the temperature of the oxidant gas supplied to the cell stack CS is too low, the temperature near the inlet of the oxidant gas of the cell stack CS decreases and the internal resistance increases. Then, while power generation does not proceed near the inlet of the oxidant gas of the cell stack CS, power generation becomes active in a portion where the internal resistance is low. In this way, the area where power generation is actively performed and the part where power generation is not active in the cell stack CS are generated, so that the area effectively used for power generation in the cell stack CS is reduced and the current density is biased. It leads to the occurrence and the decrease of the cell voltage. In addition, since the temperature of the fuel cell in the portion where the power generation reaction is performed rises particularly, it is disadvantageous in terms of durability.
However, in the solid oxide fuel cell of the present embodiment, the temperature of the oxidant gas supplied to the inside of the cell stack CS by heat exchange in the heat exchange unit 16 is the temperature inside the cell stack CS (emission oxidant). Since it is close to the temperature of the gas), the occurrence of such a problem can be avoided.

The exhausted oxidant gas after heat exchange in the heat exchange unit 16 flows out to the internal space S around the cell stack CS on the lower side of the cell stack CS. For example, although not shown, the exhaust oxidant gas flow pipe 17 is opened to the internal space S near the lower end of the heat exchange unit 16, and the exhaust oxidant gas is discharged from there toward the internal space S. That is, the exhaust oxidant gas flow pipe 17 is configured to guide the exhaust oxidant gas discharged from the inside of the cell stack CS to the lower side around the cell stack CS. As a result, the discharged oxidant gas discharged from the inside of the cell stack CS after being used in the electrochemical reaction is released into the internal space S around the cell stack CS on the lower side of the cell stack CS, and is discharged from the cell stack CS. After flowing around from the lower side to the upper side of the cell stack CS, it will be used for burning the exhaust fuel gas in the combustion unit 14.

The cell stack CS has a rectangular parallelepiped shape, and is installed in the internal space S of the storage housing 1 in a state where the stacking direction of the plurality of solid oxide fuel cell cells is along the horizontal direction. Specifically, the cell stack CS is configured by stacking a plurality of solid oxide fuel cells in the Z-axis direction. The cell stack CS has a rectangular parallelepiped shape in which the length in the Z-axis direction is shorter than the length in the X-axis direction and the length in the Y-axis direction. Further, the storage housing 1 also has a rectangular parallelepiped shape in which the length in the Z-axis direction is shorter than the length in the X-axis direction and the length in the Y-axis direction. By adopting such a configuration, the length (thickness) of the cell stack CS in the horizontal direction is determined according to the number of stacked solid oxide fuel cell cells. That is, the cell stack CS can be made thinner, and the storage housing 1 for storing the cell stack CS can also be made thinner.

The heat exchange unit 16 is provided so as to face one side surface having a short horizontal length among the four sides of the cell stack CS installed in the internal space S of the storage housing 1. Considering a structure in which the cell stack CS and the heat exchange unit 16 are installed in combination in the internal space S of the storage housing 1, the heat exchange unit 16 is located in the horizontal direction among the four sides of the cell stack CS. It is provided relative to one side surface having a short length, that is, adjacent to the cell stack CS along a direction having a long horizontal length. In the illustrated example, the heat exchange unit 16 is installed in a state of being aligned with the cell stack CS along the X-axis direction. That is, the thinnest portion of the structure in which the cell stack CS and the heat exchange unit 16 are installed in combination in the internal space S of the storage housing 1 is equivalent to the thinnest portion of the cell stack CS. As a result, the storage housing 1 for accommodating the cell stack CS and the heat exchange unit 16 can be made thinner.

The heat exchange unit 16 and the cell stack CS are arranged at a distance from each other. Then, the released oxidant gas can flow in the space between the heat exchange unit 16 and the cell stack CS.

The introduced oxidant gas flow pipe 15 is fixed to the second top surface member 6b as a top surface plate-like member constituting the top surface side of the storage housing 1 and extends vertically downward. Then, the introduced oxidant gas flow pipe 15 is connected to the cell stack CS via the heat exchange unit 16 on the way. That is, the cell stack CS is transferred from the second top surface member 6b of the storage housing 1 via the introduced oxidant gas flow pipe 15 and the heat exchange unit 16 fixed to the second top surface member 6b of the storage housing 1. It is installed in a suspended form. That is, it is preferable in that it is less necessary to specially provide a structure such as a support column for supporting the cell stack CS inside the storage housing 1.

In the lower internal space S2 of the storage housing 1, the internal front heat insulating material H1 is provided in contact with the third front member 2c, and the internal back heat insulating material H2 is in contact with the third back member 3c. The internal right side heat insulating material H3 is provided in a state of being in contact with the third right side member 4c, and the internal left side heat insulating material H4 is provided in a state of being in contact with the third left side member 5c. The inner bottom side heat insulating material H6 is provided in a state of being in contact with the third bottom surface member 7c. Then, in the lower internal space S2, the cell stack CS is placed in a space surrounded by the internal front heat insulating material H1, the internal back heat insulating material H2, the internal right heat insulating material H3, the internal left heat insulating material H4, and the internal bottom side heat insulating material H6. The heat exchange unit 16, the introduced oxidant gas flow pipe 15, the exhausted oxidant gas flow pipe 17, the introduced fuel gas flow pipe 12, and the discharged fuel gas flow pipe 13 are arranged. By adopting such a configuration, it becomes easy to maintain the temperature of the cell stack CS at a desired temperature.

Specifically, as shown in FIG. 3, the introduced oxidant gas flow pipe 15, the discharged oxidant gas flow pipe 17, the introduced fuel gas flow pipe 12, and the discharged fuel gas flow pipe 13 are connected to the front side of the cell stack CS. Has been done. Further, as shown in FIG. 3, a first recess H1a and a second recess H1b are formed in the internal front heat insulating material H1. Then, at the portion of the first recess H1a, the exhaust fuel gas flow pipe 13 is connected to the front side of the cell stack CS, and the exhaust oxidant gas flow pipe 17 is connected to the front side of the cell stack CS. Further, at the portion of the second recess H1b, the introduced fuel gas flow pipe 12 is connected to the front side of the cell stack CS, and the introduced oxidant gas flow pipe 15 is connected to the front side of the cell stack CS.

In the upper internal space S1 of the storage housing 1, an internal upper heat insulating material H5 is provided. The inner upper heat insulating material H5 is provided so as to cover the upper portion and the side portion (front side portion and back side side portion) of the reformer 11 and the combustion portion 14. Further, in the upper internal space S1, the third front member 2c is provided with a front exhaust port 2d, the third back member 3c is provided with a rear exhaust port 3d, and the third right member 4c has a right exhaust port 4d. The third left side member 5c is provided with a left side exhaust port 5d.

In the combustion unit 14, the fuel component contained in the exhaust fuel gas supplied through the exhaust fuel gas flow pipe 13 flows into the upper internal space S1 through the ventilation hole 8a formed in the partition plate 8 and flows into the combustion unit. It is burned using oxygen contained in the exhaust oxidant gas supplied through the ventilation portion 14a of 14.

Exhaust gas including combustion exhaust gas generated in the combustion unit 14 flows out to the space between the second right side member 4b and the third right side member 4c through the right side exhaust port 4d formed in the third right side member 4c. , It flows out into the space between the second left side member 5b and the third left side member 5c through the left side exhaust port 5d formed in the third left side member 5c. Further, the exhaust gas including the combustion exhaust gas generated in the combustion unit 14 flows into the space between the internal upper heat insulating material H5 and the second top surface member 6b, and from that space, the front surface formed on the third front surface member 2c. It flows out to the space between the second front member 2b and the third front member 2c through the exhaust port 2d, and passes through the back exhaust port 3d formed in the third back member 3c to the second back member 3b and the second. 3 Outflows into the space between the back member 3c.

Then, the exhaust gas including the exhaust gas flowing downward in the space between the second front member 2b and the third front member 2c, and the combustion flowing downward in the space between the second back member 3b and the third back member 3c. Exhaust gas including exhaust gas, exhaust gas including combustion exhaust gas flowing downward in the space between the second right side member 4b and the third right side member 4c, the space between the second left side member 5b and the third left side member 5c. The exhaust gas including the combustion exhaust gas flowing downward reaches the exhaust pipe 19 via the space between the second bottom surface member 7b and the third bottom surface member 7c, and is discharged from the storage housing 1. As described above, in the storage housing 1, the oxidant gas introduced into the internal space S exchanges heat with the exhaust gas including the combustion exhaust gas discharged from the internal space S, that is, is introduced into the internal space S. It is configured to preheat the oxidant gas.

As described above, in each of the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 of the storage housing 1, a plurality of wall materials w are arranged in layers at intervals from each other. It has a multi-layered structure portion M having a plurality of spaces separated by a wall material w. Then, in the multilayer structure portion M, the exhaust gas including the combustion exhaust gas generated in the combustion unit 14 and the air supplied to the cell stack CS and the combustion unit 14 flow separately in a plurality of spaces, so that the exhaust gas is exhausted. It is configured so that heat exchange between air and air is performed via the wall material w. Further, in the multilayer structure portion M, the exhaust gas flows in the space inside (on the side of the internal heat insulating material Hin), and the air flows in the space on the outside (on the side of the external heat insulating material Hout). In the multilayer structure portion M, the direction in which the exhaust gas flows and the direction in which the air flows face each other.

In the case of the front structure 2, the first front member 2a, the second front member 2b, and the third front member 2c correspond to the multilayer structure portion M. In the case of the back structure 3, the first back member 3a, the second back member 3b, and the third back member 3c correspond to the multilayer structure portion M. In the case of the right side structure 4, the first right side member 4a, the second right side member 4b, and the third right side member 4c correspond to the multilayer structure portion M. In the case of the left side structure 5, the first left side member 5a, the second left side member 5b, and the third left side member 5c correspond to the multilayer structure portion M.

In the present embodiment, in the multilayer structure portion M provided in each of the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 of the storage housing 1, the temperature is high from above to below. Exhaust gas flows. Therefore, in each multilayer structure portion M, the temperature in the upper part is higher than that in the lower part. The heat insulating effect of the external heat insulating material Hout provided on the outer surface of the multi-layered structure portion M of the storage housing 1 is formed so that the higher the temperature of the multi-layered structure portion M, the higher the heat insulating effect. For example, in the case of the present embodiment, the external heat insulating material Hout having a uniform thermal conductivity is used from the outer surface of the multi-layered structure portion M of the external heat insulating material Hout provided on the outer surface of the multi-layered structure portion M of the storage housing 1. (That is, the thickness in the normal direction) is formed to be thicker in the region where the temperature of the multilayer structure portion M is higher. In the case of the present embodiment, the external heat insulating material Hout provided on the outer surface of the multilayer structure portion M is formed to be thicker at the upper side than at the lower side. That is, since the multilayer structure portion in the high temperature region is covered with the thick external heat insulating material Hout, heat dissipation from the multilayer structure portion M in the high temperature region is effectively suppressed.

In addition, the heat insulating effect of the internal heat insulating material Hin provided on the inner surface of the multi-layered structure portion M of the storage housing 1 is formed so that the higher the temperature of the multi-layered structure portion M, the lower the heat insulating effect. For example, in the case of the present embodiment, the internal heat insulating material Hin having a uniform thermal conductivity is used from the inner surface of the multi-layered structure portion M of the internal heat insulating material Hin provided on the inner surface of the multi-layered structure portion M of the storage housing 1. The thickness (thickness in the normal direction) of the multilayer structure portion M is formed thinner as the temperature of the multilayer structure portion M is higher. That is, in the present embodiment, the higher the temperature of the multilayer structure portion M, the thicker the external heat insulating material Hout is formed and the thinner the internal heat insulating material Hin, and the lower the temperature of the multilayer structure portion M, the thicker the external heat insulating material. The Hout is formed thin and the internal heat insulating material Hin is formed thick.

As described above, the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 constituting the multilayer structure portion M of the storage housing 1 are not upright in the vertical direction but are inclined. It is provided. In the solid oxide fuel cell of the present embodiment, the thickness of the multilayer structure portion M, the thickness of the external heat insulating material Hout from the outer surface of the multilayer structure portion M, and the internal heat insulation from the inner surface of the multilayer structure portion M. The sum with the thickness of the material Hin is constant. That is, the thicknesses of the external heat insulating material Hout and the internal heat insulating material Hin vary depending on the temperature of the multilayer structure portion M, but the thickness of the multi-layered structure portion M, the external heat insulating material Hout, and the internal heat insulating material Hin is the whole. Looking at it, the total thickness is constant in the vertical vertical direction in the figure.
The inclination angles of the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 constituting the multilayer structure portion M of the storage housing 1 described above can be appropriately designed.

Next, a computer simulation performed to confirm the effects of the external heat insulating material Hout and the internal heat insulating material Hin used in the solid oxide fuel cell of the present embodiment will be described with reference to FIG.

FIG. 4A is a diagram showing a model of an embodiment, and FIG. 4B is a diagram showing a model of a comparative example. These models have a structure in which the storage housing 1 is sandwiched between the internal heat insulating material Hin and the external heat insulating material Hout from both sides thereof.

In the model of the embodiment, the higher the temperature of the multilayer structure portion M, the thicker the external heat insulating material Hout is formed and the thinner the internal heat insulating material Hin, and the lower the temperature of the multilayer structure portion M, the thicker the external heat insulating material Hout. Is formed thin and the internal heat insulating material Hin is formed thick. Specifically, as shown in FIG. 4A, L1t = 22.4 mm, L1b = 46.4 mm, L2t = 40.8 mm, and L2b = 16.8 mm. That is, in the model of the example, the total thickness of the internal heat insulating material Hin and the external heat insulating material Hout was set to 63.2 mm.

In the comparative example, the thicknesses of the external heat insulating material Hout and the internal heat insulating material Hin do not change and are kept constant between the region where the temperature of the multilayer structure portion M is high and the region where the temperature is low. Specifically, as shown in FIG. 4B, the thickness of the internal heat insulating material Hin was fixed at 40 mm, and the thickness of the external heat insulating material Hout was fixed at 30 mm. That is, in the model of the comparative example, the total thickness of the internal heat insulating material Hin and the external heat insulating material Hout was set to 70 mm.

The heights of the internal heat insulating material Hin and the external heat insulating material Hout to be simulated are 250 mm as shown in FIG. The multilayer structure portion M is a plurality of spaces separated by the wall material w by arranging the wall materials w of three SUS plates each having a thickness of 1 mm in a layered manner with an interval of 1.5 mm from each other. Have. Exhaust gas flows in the space on the left side of the figure, and air flows in the space on the right side of the figure.

[Simulation setting conditions]
The exhaust gas flowing into one space of the multilayer structure portion M has an inlet temperature of 410 ° C., and has a composition of 5.1% CO ₂ , 22.1% H ₂ O, 65.2% nitrogen, and so on. Oxygen is 7.6%. The air flowing into the other space of the multilayer structure portion M has an inlet temperature of 100 ° C. and a composition of oxygen 21% and nitrogen 79%. These conditions are based on the assumption that the vehicle is operated as follows. That is, the raw fuel gas supplied to the reformer 11 is natural gas, S / C = 2.5 in steam reforming, the fuel utilization rate is 80%, and the air utilization rate is 45%. .. The DC output of the cell stack CS is 770 W, and the average cell voltage is 0.8 V.

The thermal conductivity of each member is as follows.
Internal heat insulating material Hin and external heat insulating material Hout: 0.033W / (m ・ K)
SUS plate which is the wall material w of the multi-layer structure part M: 26.4 W / (m · K)

The boundary conditions are as follows.
Surface of internal heat insulating material Hin (left side in the figure): 600 ° C isothermal condition Surface of external heat insulating material Hout (right side in the figure): Heat transfer coefficient 20 W / (m ² · K), external temperature 40 ° C
Upper and lower ends of the model: Insulation conditions except for exhaust gas and air flow paths

The simulation results at this time are shown in Table 1 below.
In the models of Examples and Comparative Examples, the exhaust gas outlet temperature and the air outlet temperature are almost the same. The heat dissipation amount Q-out from the external heat insulating material Hout is 132 W / m ^{2 in the model of the example and 131 W / m 2 in} the model of the comparative example. As described above, the total thickness (63.2 mm) of the internal heat insulating material Hin and the external heat insulating material Hout in the model of the example is the total thickness of the internal heat insulating material Hin and the external heat insulating material Hout in the model of the comparative example. It can be seen that the amount of heat radiated from the external heat insulating material Hout can be sufficiently suppressed even though it is thinner than (70 mm).

The surface of the internal heat insulating material Hin (left side in the figure) is set to an isothermal temperature of 600 ° C. (that is, the amount of heat input is determined so that the surface of the internal heat insulating material Hin is 600 ° C.), but the amount of heat input to the internal heat insulating material Hin is Q. -In is 226 W / m ^{2 in the model of the example, and 192 W / m 2 in} the model of the comparative example. This is because, in the model of the example, the thickness of the internal heat insulating material Hin is formed thinner in the region where the temperature of the multilayer structure portion M is higher (near the exhaust gas inlet of the model), and the thickness is the same as that of the model of the comparative example. Since it is thinner than the internal heat insulating material Hin, it is considered that heat easily enters the internal heat insulating material Hin.

As shown in FIG. 6, the heat input amount Q-in to the internal heat insulating material Hin is divided into upper and lower heat input amounts Q-high and lower heat input amount Q-low in each model of the example and the comparative example. When quantified, the values are as shown in Table 2 below. As can be seen from Table 2, there is almost no difference in the amount of heat input Q-low to the lower side of the internal heat insulating material Hin between the example (106 W / m ² ) and the comparative example (107 W / m ² ). That is, when considering the configuration of the solid oxide fuel cell of the present embodiment, the amount of heat transferred from the cell stack CS installed below the internal space S of the storage housing 1 to the lower side of the inner heat insulating material is It can be said that there is almost no difference between the model of the example and the model of the comparative example. Therefore, when the model of the example is used, it can be said that the problem of lowering the temperature of the cell stack CS and the problem of increasing the amount of heat dissipated from the cell stack CS do not occur as compared with the model of the comparative example.

As described above, in the solid oxide fuel cell of the present embodiment, the thickness of the external heat insulating material Hout provided on the outer surface of the multilayer structure portion M of the storage housing 1 from the outer surface of the multilayer structure portion M is set. The region where the temperature of the multilayer structure portion M is higher is formed thicker. As a result, as shown by the numerical value of "heat dissipation amount Q-out from the external heat insulating material Hout" in Table 2 above, heat is dissipated from the multilayer structure portion M to the outside, particularly from the region where the temperature of the multilayer structure portion M is high to the outside. Heat dissipation to is effectively suppressed. Therefore, the temperature drop of the internal space S of the storage housing 1 inside the multilayer structure portion M is suppressed. Further, the total thickness of the inner heat insulating material Hin and the outer heat insulating material Hout provided inside and outside the multilayer structure portion M can be reduced without increasing the amount of heat radiation, and the storage housing 1 can be made thinner.

<Another Embodiment>
<1>
In the above embodiment, the configuration of the solid oxide fuel cell has been described with reference to specific examples, but the configuration can be changed as appropriate.
For example, the installation location of each device (reformer 11, cell stack CS, combustion unit 14, etc.) in the internal space S of the storage housing 1 can be appropriately changed. In addition, the shape of each device can be changed as appropriate.

<2>
In the above embodiment, the thickness of the external heat insulating material Hout of the same type (that is, the same thermal conductivity) and the thickness of the internal heat insulating material Hin of the same type are continuously changed (that is, heat insulation by each heat insulating material). Although the case of continuously changing the effect) has been described, the present invention is not limited to such a case. For example, as illustrated in FIG. 6, by changing the thickness of the external heat insulating material Hout of the same type and the thickness of the internal heat insulating material Hin of the same type stepwise (stepwise), the heat insulating effect of the heat insulating material is obtained. May be changed step by step.

Alternatively, if a plurality of types of heat insulating materials having different thermal conductivitys are used together, the thickness of the external heat insulating material Hout and the internal heat insulating material Hin can be made uniform without changing the thickness of the external heat insulating material Hout and the internal heat insulating material Hin. It is also possible to form a portion having a high heat insulating effect and a portion having a low heat insulating effect. For example, while keeping the thickness of the external heat insulating material Hout provided facing the multilayer structure portion M constant, the thermal conductivity is small (that is, the heat insulating effect is high) facing the region where the temperature of the multilayer structure portion M is high. An external heat insulating material Hout using a material is installed, and an external heat insulating material Hout using a material having a high thermal conductivity (that is, a low heat insulating effect) is installed facing a region where the temperature of the multilayer structure portion M is low. Can be done. Further, while keeping the thickness of the internal heat insulating material Hin provided facing the multilayer structure portion M constant, the heat conductivity is high (that is, the heat insulating effect is low) facing the region where the temperature of the multilayer structure portion M is high (that is, the heat insulating effect is low). Install the internal heat insulating material Hin using the material, and install the internal heat insulating material Hin using the material with low thermal conductivity (that is, high heat insulating effect) facing the region where the temperature of the multilayer structure portion M is low. Can be done.

<3>
In the above embodiment, the temperature of the multilayer structure portion M is set on each of the multilayer structure portions M of the front structure 2, the back structure 3, the right side structure 4, and the left side structure 5 constituting the four side surfaces of the storage housing 1. The external heat insulating material Hout is formed so that the heat insulating effect is higher in the region where the heat is higher, and the internal heat insulating material Hin is provided so that the heat insulating effect is lower in the region where the temperature of the multilayer structure portion M is higher. Although examples have been described, the present invention is not limited to such examples. For example, the external heat insulating material Hout and the internal heat insulating material Hin are provided on a total of two surfaces of the front structure 2 and the back structure 3 of the storage housing 1, and a total of two surfaces of the right side structure 4 and the left side structure 5. May be adopted.

<4>
The configurations disclosed in the above embodiment (including other embodiments, the same shall apply hereinafter) can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction, and are also disclosed herein. The embodiment is an example, and the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be used for a solid oxide fuel cell that can keep the inside of the storage housing at a high temperature and has a small heat dissipation loss.

1: Storage housing 2a: First front member (wall material w)
2b: Second front member (wall material w)
2c: Third front member (wall material w)
3a: First back member (wall material w)
3b: Second back member (wall material w)
3c: Third back member (wall material w)
4a: First right side member (wall material w)
4b: Second right member (wall material w)
4c: Third right member (wall material w)
5a: First left member (wall material w)
5b: Second left side member (wall material w)
5c: Third left member (wall material w)
11: Reformer 14: Combustion part CS: Cell stack H1: Internal front heat insulating material (internal heat insulating material Hin)
H2: Internal back insulation material (internal insulation material Hin)
H3: Internal right heat insulating material (internal heat insulating material Hin)
H4: Internal left heat insulating material (internal heat insulating material Hin)
H7: External front insulation material (external insulation material Hout)
H8: External back insulation material (external insulation material Hout)
H9: External right heat insulating material (external heat insulating material Hout)
H10: External left heat insulating material (external heat insulating material Hout)
Hin: Internal heat insulating material Hout: External heat insulating material M: Multilayer structure part S: Internal space w: Wall material

Claims (6)

A storage housing, an internal heat insulating material provided on the inner surface of the storage housing, and an external heat insulating material provided on the outer surface of the storage housing are provided.
In the internal space inside the internal heat insulating material of the storage housing, a reformer that steam-reforms raw fuel to generate fuel gas and a fuel gas generated by the reformer are used to generate power. A solid oxide fuel cell including a cell stack having a plurality of fuel cell cells and a combustion unit that burns off gas discharged from the cell stack and applies the combustion heat to the reformer.
The storage housing has a multi-layered structure portion having a plurality of spaces separated by the wall materials by arranging the plurality of wall materials in a layered manner at intervals from each other.
In the multi-layered structure portion, the exhaust gas including the combustion exhaust gas generated in the combustion portion and the air supplied to the cell stack and the combustion portion flow separately into the plurality of spaces to obtain the exhaust gas. It is configured so that heat exchange with the air is performed through the wall material.
A solid oxide fuel cell formed so that the heat insulating effect of the external heat insulating material provided on the outer surface of the multilayer structure portion of the storage housing becomes higher in a region where the temperature of the multilayer structure portion is higher. The thickness of the external heat insulating material provided on the outer surface of the multilayer structure portion of the storage housing from the outer surface of the multilayer structure portion is formed to be thicker in a region where the temperature of the multilayer structure portion is higher. The solid oxide fuel cell described in. The solid oxide fuel cell according to claim 1 or 2, wherein in the multilayer structure portion, the exhaust gas flows in the inner space and the air flows in the outer space. The solid oxide fuel cell according to any one of claims 1 to 3, wherein in the multilayer structure portion, the direction in which the exhaust gas flows and the direction in which the air flows face each other. Any one of claims 1 to 4, wherein the heat insulating effect of the internal heat insulating material provided on the inner surface of the multi-layered structure portion of the storage housing is formed so that the temperature of the multi-layered structure portion becomes lower as the temperature is higher. The solid oxide fuel cell according to the section. 5. The thickness of the internal heat insulating material provided on the inner surface of the multilayer structure portion of the storage housing from the inner surface of the multilayer structure portion is formed thinner as the temperature of the multilayer structure portion is higher. The solid oxide fuel cell described in.

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