JP3539562B2 - Solid oxide fuel cell stack - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell stack, and more particularly, to an internal reforming solid oxide fuel characterized by a stack structure that effectively utilizes heat generated from the solid oxide fuel cell. It relates to a battery stack.
[0002]
[Prior art]
In a solid oxide fuel cell having an oxide as an electrolyte, a solid oxide fuel cell having sufficient ionic conductivity to affect the efficiency is provided, and radiant heat from the solid oxide fuel cell is provided. The operating temperature is high. In addition, power is generated by a reaction opposite to the electrolysis of water, so that the reaction is exothermic. Therefore, in a solid oxide fuel cell, abundant ripening energy is excessive when generating power. It is effective to convert this high-temperature heat into electric energy for high-efficiency energy conversion efficiency, and a combined system combining a pressurized solid oxide type and a gas turbine has been devised. In addition, a cogeneration system with high efficiency by directly using heat energy has been considered.
[0003]
On the other hand, hydrocarbon fuels other than hydrogen are promising as fuels for fuel cells. When a hydrocarbon gas is applied to a fuel cell, a reformer that converts the hydrocarbon gas into hydrogen by a catalytic reaction, which is an endothermic reaction called steam reforming by heating water, and supplies the hydrogen to the fuel cell is usually required. . However, since a solid oxide fuel cell operates at a high temperature, so-called internal reforming (endothermic reaction) is possible. In addition to steam reforming, a method called partial oxidation (exothermic reaction) using no steam has been considered.
[0004]
When a solid oxide stack is used indoors, the surface temperature of the device must be reduced to about room temperature despite the temperature inside the device near 1000 ° C. Therefore, heat is confined by simply consuming thermal energy using a heat insulating material having a large volume.
[0005]
[Problems to be solved by the invention]
As described in the previous section, the solid oxide fuel cell stack is capable of performing internal reforming and effectively using heat energy, but has the following problems.
[0006]
First, in a system that uses a gas turbine together, it is necessary to pressurize the gas, which costs a lot, and the temperature range of the exhaust gas is limited in order to increase the efficiency of the gas turbine. Has become.
[0007]
Further, in a cogeneration system that directly uses heat energy, the total energy conversion efficiency of communication equipment having a low heat energy demand ratio is low. This is an internal reforming mechanism in a solid oxide fuel cell using hydrocarbons as fuel. However, since the same cell as that used for the power generation unit is used at present, an exothermic reaction and an endothermic reaction are mixed. Therefore, it is difficult to control the temperature distribution of the cell, and it is difficult to increase the reliability due to thermal stress on the cell. In addition, it is difficult to control the high-temperature steam in the internal reforming type in which the steam is added, the cost is high, and the efficiency is reduced due to the decrease in the open circuit voltage.
[0008]
On the other hand, in internal trade utilizing partial oxidation, the advantages of not using steam and utilizing the heat of the power generation unit (Japanese Patent Laid-Open No. 2000-268832) are cited as advantages. Is not shown.
[0009]
When a solid oxide fuel cell is used indoors, since the operating temperature is as high as 1000 ° C., it is necessary to surround the device accommodating the cell with a large-sized heat insulating material and air-cool or water-cool the surface of the device. Therefore, miniaturization is difficult, and in addition, thermal energy is simply discarded. That is, the energy conversion efficiency is reduced.
[0010]
An object of the present invention is to provide a solid oxide fuel cell stack that has excellent overall energy conversion efficiency and can be downsized.
[0011]
[Means for Solving the Problems]
The solid oxide fuel cell stack according to the present invention has a solid oxide fuel cell and a reforming unit for reforming a fuel gas in a stack container. The reforming unit is arranged at a position to receive heat radiation from ,
The reforming unit is disposed at a peripheral portion of the solid oxide fuel cell,
The reforming unit includes a solid oxide fuel cell (hereinafter, referred to as a “partial oxidation cell”) that performs fuel reforming by partial oxidation,
The partial oxidation cell is arranged at an outer peripheral portion in the stack container .
[0016]
[Action]
The present invention has been made in view of the above problems.
In the present invention, a solid oxide fuel cell and a reforming unit for reforming fuel gas are provided in the stack container, and the reforming unit is located at a position to receive heat radiation from the solid oxide fuel cell. A reforming section is arranged.
[0017]
Therefore, heat from the solid oxide fuel cell propagates to the reforming section by thermal radiation. The propagated heat is used for reforming the fuel gas in the reforming section (for example, constituted by a partial oxidation cell), and the reforming of the fuel gas is efficiently performed. That is, the heat energy loss is extremely small. As described above, the heat energy loss can be extremely reduced, so that the overall energy conversion efficiency is excellent. In addition, since the reforming section takes in heat energy and functions as a heat insulating material, it is not necessary to surround the apparatus with a large-sized heat insulating material, and the size can be reduced.
[0018]
Further, in another solid oxide fuel cell stack of the present invention, a solid oxide fuel cell is provided in the stack container, and a thermoelectric conversion element is provided at a position receiving radiant heat from the solid oxide fuel cell. Because of the arrangement, heat in the solid oxide fuel cell propagates to the thermoelectric conversion element by thermal radiation. The propagated heat is converted into a current by the thermoelectric conversion element, and the current can be taken out as appropriate. That is, heat energy can be effectively used as electric energy. Therefore, it has an overall excellent energy conversion efficiency.
[0019]
In addition, since the layer of the thermoelectric conversion element takes in heat energy and functions as a heat insulating material, it is not necessary to surround the device with a large-sized heat insulating material, thereby enabling downsizing.
[0020]
The reason will be described in more detail below.
In a reforming section arranged at a position (for example, around the solid oxide fuel cell) receiving heat radiation from the solid oxide fuel cell, a normal pressure fuel gas (for example, hydrocarbon gas) is supplied. Can supply. Therefore, since there is no need for pressurization, the cost of the pressurization system is not increased. Further, between the partial oxidation cell and the solid oxide fuel cell, the fuel gas is separated from the gas reformed in the reforming section, and the reformed gas is separated from the solid oxide fuel cell. Even if a gas separation shielding plate is provided for inducing heat, heat energy generated by the exothermic reaction in the solid oxide fuel cell is taken in through the gas shielding plate, and there is no need to restrict the temperature of gas exhaust from the battery.
[0021]
In addition, since the radiation is dominant in the high temperature region in which the solid oxide fuel cell operates, even if the convection is prevented, the heat easily propagates. If the reforming unit is composed of partial oxidation cells, the excess heat energy in the solid oxide fuel cell is converted to electricity in the partial oxidation cell to generate energy. Also applicable to In addition, unlike steam reforming, there is no need for steam equipment or control. In addition, since the open circuit voltage does not decrease in the partial oxidation, the efficiency of energy conversion can be increased.
[0022]
In order to lower the surface temperature of the fuel cell stack device without using a heat insulating material, it is effective to convert thermal energy into electric energy and lower the temperature. When a partial oxidation cell is used in the reforming section, the partial oxidation cell takes in thermal energy from the outside in the form of an increase in entropy, and its standard entropy change is large enough to sufficiently substitute for a heat insulating material.
[0023]
Also, instead of the partial oxidation cell, heat energy can be effectively converted to electricity by mounting components that convert heat to electricity, such as a Pb-Te thermoelectric semiconductor or a GaSb solar cell having an absorption band near infrared rays, on the inner wall of the device. By doing so, the capacity of the heat insulating material can be reduced.
[0024]
As described above, when a partial oxidation cell or a thermoelectric element is used as a heat insulating material, various problems of miniaturization, high efficiency, and fuel reforming can be solved.
[0025]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0026]
(Example 1)
1 and 2 show a solid oxide fuel cell stack according to Example 1. FIG.
FIG. 1 is a cross-sectional view of a solid oxide fuel cell stack according to Example 1 as viewed from above. Reference numeral 1 denotes a solid oxide fuel cell having an air electrode or a fuel electrode disposed outside. The solid oxide fuel cell 1 in this example has a hollow cylindrical shape.
[0027]
Reference numeral 2 denotes a gas separation shield plate (heat radiation plate) that guides the hydrocarbon gas from the outer peripheral portion to the inside and also induces heat of the fuel cell reaction section by heat radiation. 3 is a partial oxidation cell. In this example, a hollow cylindrical solid oxide fuel cell of the same type as the solid oxide fuel cell 1 was used as a partial oxidation cell. In the present example, a plurality of partial oxidation cells 3 are circumferentially arranged outside the heat radiation plate 2.
[0028]
4 is an outer wall which forms a stack container. In this example, a thin heat insulating material (not shown) is included therein. This thin insulation is much smaller in volume than conventional insulation.
[0029]
FIG. 2 is a cross-sectional view of the fuel cell stack of FIG. 1 as viewed from the side. The outermost part of the fuel cell 1 is a fuel electrode. Reference numeral 5 denotes a fuel gas (hydrocarbon gas), which is reformed in the partial oxidation cell 3. Reference numeral 6 denotes a fuel chamber, which is filled with a hydrocarbon gas, a reformed hydrogen gas, and carbon monoxide. Reference numeral 7 denotes a cell holder that separates the fuel chamber and the oxidant chamber 8.
[0030]
When the cell was operated by introducing hydrocarbon gas into the above fuel cell stack, the room temperature was almost maintained on the device surface.
[0031]
(Example 2)
FIG. 3 is a cross-sectional view of the solid oxide fuel cell stack according to Example 2 as viewed from the side.
[0032]
In this example, the outermost part of the solid oxide fuel cell 1 in FIG. 1 is an air electrode. The hydrocarbon gas is supplied from the ten fuel supply pipes to the inside of the partial oxidation cell 3 arranged on the outer peripheral portion in the stack container, and the fuel gas is reformed in the partial oxidation cell 3. The reformed fuel gas is introduced from the partial oxidation cell 3 into the fuel chamber 6, fills the fuel chamber 6, and is supplied to the solid oxide fuel cell 1 using pressure. Reference numeral 9 denotes an oxidizing agent such as oxygen gas.
[0033]
Also in this example, the partial oxidation cell 3 used was a hollow cylindrical solid oxide fuel cell of the same type as the solid oxide fuel cell 1.
[0034]
When the cell was operated by introducing hydrocarbon gas into the above fuel cell stack, the room temperature was almost maintained on the device surface.
[0035]
( Comparative Example 1 )
4 and 5 show a solid oxide fuel cell stack cell according to Comparative Example 1. FIG. 4 is a plan sectional view, and FIG. 5 is a front sectional view.
In this example, the solid oxide fuel cells 1 are arranged in a stack container, and a heat radiation plate 22 is provided between the outer wall 4 and the solid oxide fuel cells 1.
Further, the layer 11 of the thermoelectric conversion element was disposed at a position to receive radiant heat from the solid oxide fuel cell 1. In the present example, it is arranged around the solid oxide fuel cell 1 and outside the heat radiation plate 22.
[0036]
A plurality of thermoelectric elements 11 may be stacked in the same radial direction as necessary. Further, a heat insulating material may be inserted between the thermoelectric conversion element 11 and the outer wall 4.
[0037]
In this example, a plurality of thermoelectric conversion elements 11 are stacked in the same radial direction, and the number of stacked thermoelectric conversion elements 11 is changed in the vertical direction. As described above, by changing the number of stacked thermoelectric conversion elements 11 in the vertical direction, the heat distribution in the vertical direction could be reduced.
[0038]
When the above fuel cell stack cell was operated, almost room temperature was maintained on the device surface.
【The invention's effect】
As described above, the present invention efficiently reduces the size and energy consumption of a solid oxide fuel cell by stacking solid oxide fuel cells by efficiently taking in the heat generated by the cells by arranging the cells in the solid oxide fuel cell stack. Effective in improving conversion efficiency.
[Brief description of the drawings]
FIG. 1 is a plan sectional view of an internal reforming solidified fuel cell stack according to a first embodiment.
FIG. 2 is a front sectional view of the internal reforming solidified fuel cell stack according to the first embodiment.
FIG. 3 is a front sectional view of an internal reforming solidified fuel cell stack according to a second embodiment.
FIG. 4 is a plan sectional view of an internal reforming solidified fuel cell stack in Comparative Example 1 .
5 is a front sectional view of an internal reforming solidified fuel cell stack in Comparative Example 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Gas separation heat radiation plate 3 Reforming part (partial oxidation cell)
4 outer wall (stack container)
5. Fuel gas (hydrocarbon gas)
Reference Signs List 6 fuel chamber 7 cell holder 8 oxidant chamber 9 oxidant 10 fuel supply pipe 11 thermoelectric conversion element 22 heat radiation plate

Claims (1)

In the stack container, there is a solid oxide fuel cell, and a reforming unit for reforming the fuel gas, wherein the reforming unit is located at a position to receive heat radiation from the solid oxide fuel cell. Is placed ,
The reforming unit is disposed at a peripheral portion of the solid oxide fuel cell,
The reforming unit includes a solid oxide fuel cell (hereinafter, referred to as a “partial oxidation cell”) that performs fuel reforming by partial oxidation,
The solid oxide fuel cell stack , wherein the partial oxidation cell is disposed on an outer peripheral portion in the stack container .

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