JP2019053864A - Solid oxide fuel cell unit - Google Patents

Abstract

To provide a solid oxide fuel that can ensure excellent operation stability by simplifying the structure, facilitating manufacturing, reducing costs, and performing temperature control of the solid oxide fuel cell uniformly and with high precision.SOLUTION: An enclosure member (20) includes an inner layer side heat resistant enclosure member (21), outer layer side low heat insulation enclosure members (22, 22', 22''), and outer layer high heat insulation enclosure members (23, 23', 23''). The inner layer side heat resistant enclosure member (21) is located in substantially the entire area (10U, 10L, 10M) in the fuel gas flow direction of a SOFC (10). The outer layer side low heat insulation enclosure members (22, 22', 22'') are located on the outer layer side of the inner layer side heat resistant enclosure member (21) and in the middle portion (10M) in the fuel gas flow direction. The outer layer high heat insulation enclosure members (23, 23', 23'') are located on the outer layer side of the inner layer side heat resistant enclosure member (21) and at least one of the ends (10U, 10 L) in the fuel gas flow direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a solid oxide fuel cell unit.

  In recent years, development of a solid oxide fuel cell (SOFC) has been promoted. SOFC is a power generation mechanism in which oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, where the oxide ions react with hydrogen or carbon monoxide to generate electrical energy. . The SOFC has the characteristics that the power generation operating temperature is the highest (for example, 900 ° C. to 1000 ° C.) and the power generation efficiency is the highest among the currently known fuel cell configurations.

  Patent Document 1 discloses a fuel cell module having a fuel cell stack and a fuel cell case that houses the fuel cell stack and has a multilayer structure for suppressing heat dissipation from the fuel cell stack to the outside. Yes. The fuel cell case includes a first gas passage layer through which a first gas (air) having a temperature lower than that of the fuel cell stack flows, and a first gas (air) provided inside the first gas passage layer. And a second gas flow path layer through which a second gas (exhaust gas exhausted from the fuel cell stack) having a higher temperature than) flows. Then, the second gas flow path is provided at a portion where the high thermal conductivity member provided on the flow path wall on the fuel cell stack side of the first gas flow path layer is close to the center part (high temperature part) of the fuel cell stack. The layer passes through the layer and is in contact with the channel wall on the fuel cell stack side of the second gas channel layer.

  Patent Document 2 discloses a fuel cell system in which temperature is controlled by cooling the fuel cell stack by supplying air to the air flow path of the fuel cell stack with a fan or supplying water with a nozzle.

  In Patent Document 3, a plurality of fuel cells are cooled by increasing a supply amount of a gas to be reformed to an external reformer to generate a local endothermic state in a peripheral portion of the external reformer. A solid oxide fuel cell device that performs temperature control is disclosed.

JP 2010-49969 A JP 2007-323993 A JP 2013-8456 A

  However, Patent Documents 1 to 3 have the following technical problems.

  In Patent Document 1, since it is necessary to precisely process the flow path walls of the first gas flow path layer and the second gas flow path layer and embed high thermal conductivity members in these, the structure becomes complicated and the manufacturing process is difficult. It will be difficult and costly.

  In Patent Document 2, since the internal temperature of the fuel cell stack becomes non-uniform (for example, a temperature difference occurs between one end, the other end, and the center in the stacking direction of the fuel cell stack or the flow path direction) Will be disturbed. Moreover, the cooling effect is insufficient only by supplying air to the air flow path of the fuel cell stack with a fan or water with a nozzle.

  Patent Document 3 has a problem that a cooling effect is not sufficient only by generating a local endothermic state in the peripheral portion of the external reformer, and the temperature of the plurality of fuel cells is difficult to decrease. Moreover, since the internal temperature of a some fuel cell becomes non-uniform | heterogenous, operation | movement stability will be inhibited.

  The present invention has been made in view of such points, and by simplifying the structure, facilitating production, and reducing costs, and performing temperature control of the solid oxide fuel cell uniformly and with high accuracy. One object of the present invention is to provide a solid oxide fuel cell unit capable of ensuring excellent operational stability.

  In one aspect, the solid oxide fuel cell unit of the present embodiment is a solid oxide fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel gas flow of the solid oxide fuel cell. A solid oxide fuel cell unit that surrounds a side surface in the direction, wherein the surrounding member is an inner layer side heat-resistant surrounding member located in substantially the entire region in the fuel gas flow direction, and the inner layer side heat-resistant enclosure. An outer layer-side low heat insulating enclosure member located on the outer layer side of the member and in the middle of the fuel gas flow direction; and an outer layer side of the inner layer heat-resistant enclosure member and located at at least one end in the fuel gas flow direction And an outer layer side high thermal insulation surrounding member.

  According to the present invention, the structure is simplified, the manufacture is facilitated, the cost is reduced, and the temperature control of the solid oxide fuel cell is performed uniformly and with high accuracy to ensure excellent operational stability. A solid oxide fuel cell unit can be provided.

It is a schematic block diagram which shows the solid oxide fuel cell unit of this embodiment. It is a conceptual diagram which shows the temperature distribution of the fuel gas flow direction at the time of SOFC power generation. It is sectional drawing which shows the structure of the surrounding member by 1st Embodiment. It is sectional drawing which shows the structure of the surrounding member by 2nd Embodiment. It is sectional drawing which shows the structure of the surrounding member by 3rd Embodiment.

<< Schematic configuration of solid oxide fuel cell unit 1 >>
FIG. 1 is a schematic configuration diagram showing a solid oxide fuel cell unit (SOFC unit) 1 of the present embodiment. In the following description, the upper, lower, left, and right directions are based on the arrow direction indicated in the drawing.

  The SOFC unit 1 has a solid oxide fuel cell (SOFC) 10. The SOFC 10 has a cell stack in which a plurality of cells are stacked or assembled. Each cell has a basic configuration in which an electrolyte is sandwiched between an air electrode and a fuel electrode, and a separator is interposed between the cells. Each cell of the cell stack is electrically connected in series. The SOFC 10 is a power generation mechanism in which oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions react with hydrogen or carbon monoxide at the fuel electrode to generate electrical energy. .

  The SOFC 10 (cell stack) of the present embodiment can have a cylindrical shape that is long in the vertical direction and short in the horizontal direction, but the shape of the SOFC 10 (cell stack) is not limited to this, and various design changes are possible. (It can also be a polygonal prism shape such as a triangular prism or a quadrangular prism, or a cell stack in which a large number of flat cells are stacked).

  The SOFC 10 has an oxidant gas channel (cathode gas channel) 11 and a fuel gas channel (anode gas channel) 12. In FIG. 1, the oxidant gas flow path 11 and the fuel gas flow path 12 inside the SOFC 10 are drawn as a single line for reasons of drawing convenience. The gas flow path 12 is a separate flow path, and there are a plurality of gas flow paths. An oxidant gas taken in from the air blower 13 and heated by the heat exchanger (heating mechanism) 14 is supplied to the inlet of the oxidant gas flow path 11, and from the outlet of the oxidant gas flow path 11, Oxidant gas exhaust gas is discharged. A fuel gas taken in from a fuel gas supply device (not shown) and heated by a heat exchanger (heating mechanism) is supplied to the inlet portion of the fuel gas passage 12, and from the outlet portion of the fuel gas passage 12 The exhaust gas of the fuel gas is discharged. The oxidant gas supplied to the oxidant gas flow path 11 and the fuel gas supplied to the fuel gas flow path 12 cause an electrochemical reaction to generate a direct current (SOFC 10 generates power).

  In FIG. 1, the oxidant gas flow path 11 and the fuel gas flow path 12 of the SOFC 10 extend in the vertical direction, and the oxidant gas flows from the lower side to the upper side of the oxidant gas flow path 11. The fuel gas flows from the upper side to the lower side of the path 12. Therefore, in this embodiment, the vertical direction in FIG. 1 corresponds to the “oxidant gas flow direction” and the “fuel gas flow direction” of the SOFC 10. However, the “oxidant gas flow direction” and the “fuel gas flow direction” of the SOFC 10 are not necessarily limited to a direction extending in a straight line, but mean directions when viewed macroscopically. That is, the oxidant gas channel 11 and the fuel gas channel 12 do not extend in a straight line in the vertical direction, but, for example, extend in the vertical direction with a portion bent in the horizontal direction. Even in this case, the vertical direction corresponds to the “oxidant gas flow direction” and the “fuel gas flow direction” of the SOFC 10.

  The SOFC unit 1 has an enclosing member 20 that surrounds the side surface of the fuel gas flow direction of the SOFC 10 (the direction from the top to the bottom, hereinafter simply referred to as the vertical direction). A specific configuration of the surrounding member 20 will be described in detail in first to third embodiments described later.

  The SOFC unit 1 includes an upper end header member 30 that covers the upper end surface of the SOFC 10 and a lower end header member 40 that covers the lower end surface of the SOFC 10. The upper end header member 30 and the lower end header member 40 are provided with piping structures for constituting the oxidant gas passage 11 and the fuel gas passage 12 extending from the SOFC 10.

  The SOFC unit 1 has an upper end side lid member 50 and a lower end side lid member 60. The upper end side lid member 50 has an inverted U-shape that covers the upper end surface of the surrounding member 20 and the side surfaces and upper end surface of the upper end side header member 30. The lower end side lid member 60 has a U-shape that covers the lower end surface of the surrounding member 20, and the side surface and lower end surface of the lower end side header member 40. The upper end side lid member 50 and the lower end side lid member 60 are provided with a piping structure for constituting the oxidant gas passage 11 and the fuel gas passage 12 extending from the SOFC 10.

  The SOFC unit 1 has an airtight housing 70 that houses a combined body of the SOFC 10, the surrounding member 20, the upper end side header member 30, the lower end side header member 40, the upper end side lid member 50, and the lower end side lid member 60 in an airtight state. ing.

≪Temperature distribution in fuel gas flow direction during SOFC10 power generation≫
During power generation of the SOFC 10, the temperature of the SOFC 10 varies depending on the position in the fuel gas flow direction (vertical direction). In FIG. 2, in order to facilitate understanding of the invention, the temperature range of the SOFC 10 is divided into 3 parts of a base end part (upper end part) 10U, a front end part (lower end part) 10L and an intermediate part 10M in the fuel gas flow direction (vertical direction). It is divided into two. As apparent from FIG. 2, during power generation of the SOFC 10, the intermediate portion 10M of the SOFC 10 has the highest temperature (for example, about 800 to 1000 ° C.), and the base end portion (upper end portion) 10U of the SOFC 10 has the second highest temperature (for example, 700 to The end portion (lower end portion) 10L of the SOFC 10 has the lowest temperature (for example, about 600 to 800 ° C.). In the present embodiment, the envelope member 20 of the SOFC unit 1 is devised to ensure excellent operational stability by performing temperature control in the fuel gas flow direction (vertical direction) of the SOFC 10 uniformly and with high accuracy. Yes. Hereinafter, a specific configuration of the surrounding member 20 will be described in detail with reference to the first to third embodiments.

<< First Embodiment >>
FIG. 3 is a cross-sectional view showing the configuration of the surrounding member 20 according to the first embodiment.

  The enveloping member 20 has an inner layer side heat-resistant enclosing member 21 located in the innermost layer of the SOFC 10 in substantially the entire fuel gas flow direction (vertical direction) (substantially the entire region extending from the base end 10U, the distal end 10L, and the intermediate portion 10M). have. The inner layer side heat-resistant surrounding member 21 can be made of a material having both heat resistance and low heat insulation properties, for example, a polycrystalline alumina short fiber having a maximum use temperature exceeding 1000 ° C.

  The surrounding member 20 has an outer layer side low heat insulating surrounding member 22 located on the outer layer side of the inner layer side heat resistant surrounding member 21 and in the middle portion (intermediate portion 10M) in the fuel gas flow direction (vertical direction) of the SOFC 10. . The outer layer side low thermal insulation surrounding member 22 is formed, for example, by continuously laminating ceramic fibers and forming them into a blanket shape by needle punching, or by adding an inorganic binder or an organic binder to bulk fibers into a plate shape. It can be constructed from a molded one.

  The surrounding member 20 is located on the outer layer side of the inner layer side heat-resistant surrounding member 21 and on the outer layer side height located at one end (base end portion 10U) and the other end portion (leading end portion 10L) of the SOFC 10 in the fuel gas flow direction (vertical direction). A heat insulating surrounding member 23 is provided. The outer layer side high heat insulating surrounding member 23 can be made of a fiber material containing silica nanoparticles having ultra-low thermal conductivity as a main component.

  Thus, the outer layer side low heat insulation surrounding member 22 and the outer layer side high heat insulation surrounding member 23 are comprised from the separate member from which heat insulation performance differs. The heat insulating performance is mainly determined by the thermal conductivity and thickness of the surrounding member.

  The words “low thermal insulation” and “high thermal insulation” of the outer layer side low thermal insulation surrounding member 22 and the outer layer side high thermal insulation surrounding member 23 are used on a relative basis, not on an absolute basis. In other words, the parameter for evaluating the heat insulation performance of a member does not satisfy a specific standard, but “low heat insulation”, on the contrary, it does not mean “high heat insulation” because it satisfies a specific standard. When the heat insulating performance of the side low heat insulating surrounding member 22 and the outer layer side high heat insulating surrounding member 23 are compared, the former means lower than the latter (the latter is higher than the former).

  According to the surrounding member 20 configured as described above, the inner layer side heat-resistant surrounding member 21 is provided over substantially the entire side surface of the fuel gas flow direction (vertical direction) of the SOFC 10, so that the SOFC 10 can generate power at the time of power generation. It is possible to prevent the SOFC unit 1 from being damaged by heat.

  Further, since the outer layer side low thermal insulation surrounding member 22 is provided corresponding to (adjacent to) the intermediate portion 10M of the SOFC 10 that is the highest temperature, the heat from the intermediate portion 10M during the power generation of the SOFC 10 is dissipated to the side. Easier (heat dissipation increases). On the other hand, since the outer layer side high thermal insulation surrounding member 23 is provided corresponding to (adjacent to) the base end portion 10U and the front end portion 10L of the SOFC 10 which is relatively low in temperature, the base end portion 10U and the front end during power generation of the SOFC 10 It becomes difficult for the heat from the portion 10L to radiate to the side (the amount of heat radiated decreases). As a result, it is possible to ensure excellent operational stability by performing temperature control in the fuel gas flow direction (vertical direction) of the SOFC 10 uniformly and with high accuracy. That is, the cell reaction region in which high output can be obtained can be expanded to improve the power generation efficiency, and the SOFC 10 can be thermally independent (the SOFC 10 can be stably operated without providing a separate heating unit). The solid line L in FIG. 3 represents the temperature distribution in the fuel gas flow direction (vertical direction) of the SOFC 10 in the SOFC unit 1 of the first embodiment, and the broken line H in FIG. 3 represents the SOFC in the conventional SOFC unit. Represents the temperature distribution in the fuel gas flow direction (vertical direction). The solid line L in FIG. 3 indicates that there is less variation in the temperature distribution in the fuel gas flow direction (vertical direction) than the broken line H in FIG.

  Furthermore, since it is only provided on the side of the fuel gas flow direction (vertical direction) of the SOFC 10 on the surrounding member 20 (the inner layer side heat resistant surrounding member 21, the outer layer side low heat insulating surrounding member 22, the outer layer side high heat insulating surrounding member 23), The structure of the SOFC unit 1 can be simplified, the manufacturing can be facilitated, and the cost can be reduced.

<< Second Embodiment >>
FIG. 4 is a cross-sectional view showing a configuration of the surrounding member 20 according to the second embodiment. In the second embodiment, the outer layer side low heat insulating surrounding member 22 ′ and the outer layer side high heat insulating surrounding member 23 ′ are made of the same material, and the heat insulating performance is varied depending on the thickness thereof. More specifically, the thickness of the outer layer side low heat insulating surrounding member 22 ′ is set smaller than the thickness of the outer layer side high heat insulating surrounding member 23 ′. With the configuration of the second embodiment, the amount of heat released from the intermediate portion 10M of the SOFC 10 increases and the temperature of the intermediate portion 10M of the SOFC 10 decreases. As a result, the temperature distribution in the SOFC unit 1 is smaller in the second embodiment than in the prior art. The solid line L in FIG. 4 represents the temperature distribution in the fuel gas flow direction (vertical direction) of the SOFC 10 in the SOFC unit 1 of the second embodiment, and the broken line H in FIG. 4 represents the SOFC fuel in the conventional SOFC unit. It represents the temperature distribution in the gas flow direction (vertical direction). A solid line L in FIG. 4 indicates that there is less variation in temperature distribution in the fuel gas flow direction (vertical direction) than the broken line H in FIG.

«Third embodiment»
FIG. 5 is a cross-sectional view showing a configuration of the surrounding member 20 according to the third embodiment. In the third embodiment, the outer layer side low heat insulating enclosure member 22 ″ and the outer layer side high heat insulating enclosure member 23 ″ are made of different materials having different heat insulation performance, and the heat insulation performance is further varied depending on the thickness thereof. . More specifically, the thickness of the outer layer side low heat insulating surrounding member 22 ″ is set smaller than the thickness of the outer layer side high heat insulating surrounding member 23 ″. With the configuration of the third embodiment, the amount of heat released from the intermediate portion 10M of the SOFC 10 increases and the temperature of the intermediate portion 10M of the SOFC 10 decreases. As a result, the temperature distribution in the SOFC unit 1 is smaller in the third embodiment than in the prior art. The solid line L in FIG. 5 represents the temperature distribution in the fuel gas flow direction (vertical direction) of the SOFC 10 in the SOFC unit 1 of the third embodiment, and the broken line H in FIG. 5 represents the SOFC in the conventional SOFC unit. Represents the temperature distribution in the fuel gas flow direction (vertical direction). A solid line L in FIG. 5 indicates that variation in temperature distribution in the fuel gas flow direction (vertical direction) is less than that of the broken line H in FIG.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, function, and the like of the components illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In the above embodiment, the case where the outer layer side highly heat insulating surrounding member 23, 23 ′ or 23 ″ is provided corresponding to both ends (base end portion 10U and tip end portion 10L) of the SOFC 10 in the fuel gas flow direction is exemplified. However, the outer layer side highly heat insulating surrounding member 23, 23 ′ or 23 ″ may be provided corresponding to one end of the fuel gas flow direction of the SOFC 10.

  In the above embodiment, the case where two types of outer layer side heat insulating surrounding members, that is, the outer layer side low heat insulating surrounding member 22, 22 'or 22 "and the outer layer side high heat insulating surrounding member 23, 23' or 23" are provided. Although illustrated and demonstrated, you may provide three or more types of outer-layer side heat insulation surrounding members.

  The solid oxide fuel cell unit of the present invention is suitable for application to solid oxide fuel cell units for household, commercial, and other industrial fields.

1 Solid oxide fuel cell unit (SOFC unit)
10 Solid Oxide Fuel Cell (SOFC)
10U Base end (upper end)
10L Tip (lower end)
10M Intermediate part 11 Oxidant gas channel (cathode gas channel)
12 Fuel gas channel (Anode gas channel)
13 Air blower 14 Heat exchanger (heating mechanism)
20 Surrounding member 21 Inner layer side heat resistant surrounding member 22 22 '22 "Outer layer side low heat insulating surrounding member 23 23'23" Outer layer side high heat insulating surrounding member 30 Upper end side header member 40 Lower end side header member 50 Upper end side lid member 60 Lower end Side lid member 70 Airtight housing

Claims (4)

A solid oxide fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas;
An enclosing member surrounding a side surface of the solid oxide fuel cell in the fuel gas flow direction;
A solid oxide fuel cell unit comprising:
The surrounding member is
An inner layer side heat-resistant surrounding member located in substantially the entire region of the fuel gas flow direction;
An outer layer side low heat insulating enclosure member located on the outer layer side of the inner layer heat resistant enclosure member and in the middle of the fuel gas flow direction;
An outer layer side high thermal insulation surrounding member located on the outer layer side of the inner layer side heat resistant surrounding member and at least one end in the fuel gas flow direction;
A solid oxide fuel cell unit comprising:   2. The solid oxide fuel cell unit according to claim 1, wherein the outer layer side low heat insulating surrounding member and the outer layer side high heat insulating surrounding member are made of different materials having different heat insulating performances.   2. The solid oxide according to claim 1, wherein the outer layer side low heat insulating enclosure member and the outer layer side high heat insulating enclosure member are made of the same material and have different heat insulation performance depending on their thickness. Physical fuel cell unit.   The outer layer side low heat insulating enclosure member and the outer layer side high heat insulating enclosure member are made of different materials having different heat insulation performances, and the heat insulation performances are different depending on their thicknesses. The solid oxide fuel cell unit described in 1.

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