JP5336159B2 - Flat plate type solid oxide fuel cell module and operation method thereof - Google Patents

Description

  The present invention relates to a flat plate type solid oxide fuel cell module having an electrolyte layer made of a flat plate type solid oxide and an operation method thereof.

  A flat solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell, hereinafter also referred to as a flat SOFC) has higher power generation efficiency and higher operating temperature (700 to 1000 ° C) than other fuel cells. It has an advantage that high-temperature heat can be used (see, for example, Patent Document 1).

  FIG. 9 shows a conventional flat SOFC. 1 is a power generation unit including one flat solid oxide fuel cell, 4 is a flat SOFC stack formed by stacking a plurality of, for example, eight power generation units 1 and electrically connecting them in series (hereinafter referred to as a power generation unit). 5 and 6 are metal plates for sandwiching the upper and lower surfaces of the cell stack 4, 7 is a stack container for storing the cell stack 4, and 8 is a load mechanism for pressurizing and sealing the cell stack 4. The flat plate type SOFC module 10 is configured, and power is generated by supplying fuel gas and oxidant gas to the cell stack 4.

  The load mechanism 8 includes a stack load rod 11 provided through the upper surface of the stack container 7 and a load device 12 that presses the stack load rod 11 against the upper metal plate 5. The degree of adhesion is increased (full of gaps at room temperature) to reduce power transmission loss at the connection.

  Such a flat plate SOFC module 10 starts power generation after the anode is reduced after the temperature is raised to a temperature (800 to 1000 ° C.) assuming a steady operation. Once the reduced single cell is kept in the reducing atmosphere on the anode side, it is not oxidized again. In other words, the reduction work is required only when the temperature is first raised. When the anode is reduced, the thickness of the anode decreases and the single cell becomes thinner. For this reason, in the initial reduction, the height of the cell stack, which is the power generation portion, becomes lower due to the thinning of the cell itself, the collapse of the soft current collecting member, the melting of the sealing material (glass), and the like. The load mechanism 8 can apply a constant load to the cell stack 4 even if the height of the cell stack 4 changes if the force pushing the stack load rod 11 of the load device 12 is made constant.

  As another load mechanism, a method using a ceramic spring or a weight is also known. However, when a ceramic spring is used, when the height of the cell stack 4 is lowered, the load applied to the cell stack 4 is reduced and the power generation efficiency is lowered.

  When a load is applied to the cell stack 4 by the weight, a constant load can always be applied, but the load applied by the strength of the table on which the cell stack 4 is placed is limited. Considering that if the space where the cell stack 4 is installed becomes too large, the heat dissipation loss becomes too large. When a load is applied with a weight, the limit is about 30 kgf. Further, when a weight is used, there arises a problem that the weight of the flat plate-type SOFC module increases by the weight.

  On the other hand, when the above-described load mechanism 8 is used, a load of 100 kgf or more can be easily applied by using a hydraulic pump or the like as the load device 12.

  As described above, the load mechanism 8 using the stack load rod 11 and the load device 12 can apply a constant load even when the height of the cell stack 4 is lowered by the initial reduction, and can apply a large load. It is excellent in that it can.

JP 2006-339035 A

  However, the load mechanism 8 using the stack load rod 11 and the load device 12 has the following problems. That is, it is necessary to provide the stack container 7 with a hole through which the stack load rod 11 slidably passes. If such a hole is provided, the airtightness and heat insulation inside the container are reduced. The output characteristics will also deteriorate. Further, since the load is not applied when the load device 12 is stopped, it is difficult to take out the cell stack 4 which has been once heated and reduced and replace it with another container or transport it.

  Therefore, as a result of diligent study on the load, the present inventors have provided a connection mechanism including two metal plates sandwiching the upper and lower surfaces of the cell stack and a connection member for connecting these metal plates, and at the time of reduction action Applies a load by the conventional load mechanism 8, and thereafter removes the conventional load mechanism 8 and applies a load by the connecting mechanism, that is, the load mechanism is not provided with the load mechanism at the time of power generation. It was found that it can be moved to another stack container and operated, and a good power output can be obtained.

  The present invention has been made on the basis of the above-described conventional problems and knowledge. The object of the present invention is a flat solid oxide fuel cell module having a small and stable power output and high installation stability, and its operation. It is to provide a method.

In order to achieve the above object, a flat plate type solid oxide fuel cell module according to the present invention includes a cell stack using a flat plate type solid oxide fuel cell, and two metals sandwiching the upper and lower surfaces of the cell stack. and a coupling mechanism comprising a plate and a connecting member for connecting the metal plates to each other, the connecting member is greater than the thermal expansion coefficient of the thermal expansion coefficient of the cell stack, one end of the two metal plates The other end side is inserted into a locking hole formed in the other of the two metal plates, and the locking portion is formed by a locking portion formed by plastic deformation due to a load applied during the reduction action. It is locked in the hole.

Further, according to the present invention, in the above invention, the locking hole formed in the other metal plate is a non-through hole, and the tip portion is formed wider than the opening edge.

  In the present invention, the other end of the connecting member is formed hollow.

  Further, according to the present invention, in the above invention, the coupling mechanism functions as a load mechanism for the cell stack during power generation.

Further, an operation method of the flat solid oxide fuel cell module according to the present invention includes a cell stack using the flat solid oxide fuel cell, and two metal plates sandwiching the upper and lower surfaces of the cell stack. , The thermal expansion coefficient is larger than the thermal expansion coefficient of the cell stack, one end is fixed to one of the two metal plates, and the other end side is formed in the other of the two metal plates. The flat stack type solid oxide fuel cell module having a connecting mechanism including a connecting member for connecting the two metal plates to each other, the cell stack at a temperature higher than a power generation temperature perform a reducing action while applying a load to, Tsu by the other end portion of the coupling member in the load with the the height of the cell stack is lowered to a locking portion formed by plastically deformed by initial reduction The It comprises a first step of engaging the other end of the connecting member in the locking hole, and a second step of generating at the generator temperature while applying a load to the cell stack only by the coupling mechanism Is.

  In the present invention, when a load is applied to the connecting member by the load mechanism during the reducing action, the other end of the connecting member is plastically deformed and is locked in the locking hole of the metal plate. In addition, since reduction is performed at a temperature higher than the power generation temperature, and then power generation is performed by lowering the temperature to the power generation temperature, the connecting member contracts and becomes shorter than the cell stack, resulting in thermal stress. Thereby, the cell stack between the metal plates is pressed by the two metal plates. In other words, the connecting mechanism composed of the metal plate and the connecting member functions as a load mechanism for the cell stack due to the difference between the temperature during the reducing action, the temperature difference during power generation, and the thermal expansion coefficient after the reducing action. Make the mechanism unnecessary. For this reason, after the reducing action, the power generation performance can be improved by taking out the module from the module container provided with the load mechanism and storing the fuel cell in the module container not provided with the load mechanism. That is, if the load mechanism is not provided, the number of holes through which the stack load rod for applying a load to the cell stack is reduced, so that the heat insulation and airtightness of the container are increased, and the power generation performance is improved. In addition, since the conventional load mechanism is not required, the installation stability can be improved by reducing the weight and size and the center of gravity, and it can be easily moved and transported.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a schematic configuration diagram at the time of reduction showing an embodiment of a flat solid oxide fuel cell module according to the present invention, and FIG. FIG. 3B is a cross-sectional view of a main part showing a state immediately after the operation, FIG. 3B is a cross-sectional view showing a state in which the end of the connecting member is plastically deformed, FIG. FIG. 5 is an exploded perspective view of the power generation unit, FIG. 6 is a side view of the fuel cell support type single cell, and FIG. 7 is a constant load from initial reduction to initial energization. FIG. 8 is a diagram showing that it is not necessary to control the load on the cell stack after the initial energization. Note that the same members and parts as those shown in FIG.

First, the principle of the present invention will be described.
The present invention is based on the facts found from the following series of experimental results.
FIG. 7 shows a case where a load of 120 kgf is applied to the cell stack 4 by the load mechanism 8 using the stack load rod 11 and the load device 12 during the initial reduction in the conventional flat plate type SOFC module 10 shown in FIG. It is a figure which shows the current density-voltage characteristic at the time of stopping 12 and not applying a load. Here, the number of power generation units 1 stacked is one.

  As is apparent from FIG. 7, the load applied to the power generation part during the initial energization from the initial reduction affects the output characteristics. That is, it is necessary to apply a load sufficient to bring out the power generation characteristics from the initial reduction to the initial energization while controlling the magnitude thereof.

FIG. 8 shows a change in voltage when the load is decreased after the initial reduction to the initial energization while applying a load of 120 kgf. Here, the number of power generation units 1 stacked is one. The load was changed by changing the force pushing the stack load rod 11 in the load device 12. Further, when changing the load, the current density (0.28 Acm ⁻² ) was kept constant.

  As is apparent from FIG. 8, the power generation characteristics are not affected by the load after the initial energization. That is, if a constant load is applied from the initial reduction to the initial energization, it can be said that it is not necessary to control the load thereafter. However, it is desirable to continue to apply a load during subsequent power generation in preparation for a case where external vibration is applied during power generation. In addition, since various members are deformed by thermal expansion when the temperature is raised and lowered, and a force that shifts the position of the members is applied, it is desirable to continue to apply a load even when the temperature is raised and lowered. And when moving the installation place at room temperature, it is desirable to continue to apply a load in preparation for vibration.

In summary,
(1) From initial reduction to initial energization, it is necessary to continue to apply a load sufficient to bring out the power generation characteristics while controlling the magnitude of the load.
(2) Although it is desirable to continue applying a load to the power generation part even after the initial energization, it is not necessary to control the magnitude.

Hereinafter, a flat solid oxide fuel cell module according to the present invention will be described in detail.
In FIG. 1, a flat plate SOFC module 20 according to the present invention includes a flat plate cell stack 4 formed by stacking a plurality of power generation units 1 and electrically connecting them in series. Although it is substantially the same as the conventional flat plate type SOFC module 10 shown in FIG. 2, the difference in the load method during the reduction action and the subsequent rated power generation, the two metal plates 5 and 6 and the connecting member 21 after the reduction action. This is different from the conventional apparatus in that the connecting mechanism 22 composed of That is, the flat plate SOFC module 20 needs to start power generation after reducing the anode after raising the temperature to a temperature that assumes a steady operation as described above. For this reason, as shown in FIG. 1, during the reduction action, a decrease in the degree of adhesion between the single cells 2 (FIGS. 5 and 6) due to a reduction in the thickness of the anode due to the reduction action, power transmission loss, etc. are prevented Therefore, a load necessary for the cell stack 4 is applied by the load mechanism 8. As the load mechanism 8, the stack load rod 11 and the load device 12 are used. However, any load mechanism may be used as long as it can apply a necessary load.

  Initial energization from initial reduction is performed at a temperature higher than the steady power generation temperature. For example, if the steady power generation temperature is 800 ° C., the initial reduction is performed at about 820 to 850 ° C.

  5 and 6, the power generation unit 1 includes a single cell 2, a separator set 3, a cell holder 14, and the like.

  The unit cell 2 includes an electrolyte layer 15 made of a flat solid oxide, and an air electrode 16 and a fuel electrode 17 formed on the front and back surfaces of the electrolyte layer 15 to form a fuel electrode support type single cell. ing.

  The separator set 3 is configured by stacking, for example, four metal separators 3A to 3D and a cell holder 14 each having a groove 18 and a hole 19 each having a predetermined shape, and these separators 3A to 3D The cell holder 14 accommodates the single cell 2, the gas path for supplying and discharging the oxidant gas to the air electrode 16, the gas path for supplying and discharging the fuel gas to the fuel electrode 17, and electricity from the single cell 2. A path (both not shown) is formed.

  The cell stack 4 formed by stacking a plurality of power generation units 1 composed of such single cells 2 and separator sets 3 and electrically connecting them in series has the load mechanism 8 attached after the coupling mechanism 22 is attached. The module container 7 (corresponding to the conventional stack container 7 shown in FIG. 9; the same applies hereinafter) is accommodated (FIG. 1), and after the initial reduction, it is taken out from the module container 7 and shown in FIG. Is housed in a module container 25 that does not include

  The corners of the two metal plates 5 and 6 that sandwich the upper and lower surfaces of the cell stack 4 are connected by four connecting members 21. A predetermined load is applied to the upper metal plate 5 by the stack load rod 11 of the load mechanism 8 during the reduction action. The lower metal plate 6 is installed on the heat insulating plate 23 and receives the load applied to the cell stack 4.

  The connecting member 21 is manufactured in a solid round bar shape with a metal material having a thermal expansion coefficient larger than the thermal expansion coefficient (average thermal expansion coefficient) of the cell stack 4, and the upper end 21 a is welded to the upper metal plate 5, a nut or the like. The lower end 21b is merely inserted into the locking hole 24 formed of a non-through hole formed in the upper surface of the lower metal plate 6 and is not fixed. The lower end portion 21b inserted into the locking hole 24 of the connecting member 21 may have any shape as long as the shape is plastically deformed when a required load is applied by the load mechanism 8. In FIG. 2, it is formed in a hollow (cylindrical) shape as shown in FIG. The locking hole 24 has a hole diameter slightly larger than the outer diameter of the connecting member 21 on the edge side of the opening 24a, and has a hole diameter larger than the opening 24a at the tip (inner back) 24b. When the thickness of the anode is reduced by the initial reduction and the height of the cell stack 4 is lowered, the connecting member 21 is gradually crushed at the lower end 21 b by the load applied to the metal plate 5 by the load mechanism 8. Therefore, when the lower portion of the lower end portion 21b inserted into the distal end portion 24b of the locking hole 24 is greatly plastically deformed in the direction perpendicular to the axis as shown in FIG. Formed and locked in the locking hole 24.

  Further, since the connecting member 21 is shortened when the lower end portion 21 b is crushed, the upper metal plate 5 is pressed against the upper surface of the cell stack 4. Further, since the power generation temperature during power generation is lower than the temperature during reduction as described above, the connecting member 21 will contract by a length corresponding to the temperature difference during reduction and the difference in thermal expansion coefficient from the cell stack 4. Is generated and presses the metal plate 5, whereby the coupling mechanism 22 functions as a load mechanism for the cell stack 4. Therefore, at the time of rated power generation after the initial reduction, if the anode side is kept in the reducing atmosphere, it will not be oxidized again. In other words, since no reduction work is required, the cell stack 4 is taken out of the module container 7 together with the connection mechanism 22 and is installed in another module container 25 that does not have an external load mechanism as shown in FIG. Power generation can be performed at a power generation temperature of.

  Thus, since the flat plate type SOFC module 20 according to the present invention causes the coupling mechanism 22 to function as a load mechanism during rated power generation, the module is taken out from the module container 7 shown in FIG. 1 and shown in FIG. Thus, it can be installed in another module container 25 that does not include the conventional load mechanism 8, thereby solving the conventional problem that gas and heat leak from the module container 7 and the performance of the flat SOFC deteriorates. And a good power output can be obtained. That is, if the module container 25 does not include the load mechanism 8, it is not necessary to provide a hole through which the stack load rod 11 penetrates. Therefore, the heat insulation and air tightness of the module container 25 are improved, and the power generation performance can be improved. .

  Further, if the conventional load mechanism 8 is not required at the time of power generation, the size and weight can be reduced, and the installation stability can be improved by lowering the center of gravity.

  In the above-described embodiment, the upper end 21 a side of the connecting member 21 is fixed to the upper metal plate 5, and the lower end portion 21 b side is formed in a cylindrical shape so as to be formed in the lower metal plate 6. The locking portion 21c is formed by being inserted into 24 and plastically deformed by applying a load, and is configured to be locked in the locking hole 24. However, the present invention is not limited to this, and the upper metal plate 5 is A locking hole may be formed, and the upper end side of the connecting member 21 may be formed into a shape that can be easily plastically deformed, inserted into the locking hole, and plastically deformed by applying a load to form a locking portion.

  Further, in the present embodiment, the fuel electrode supporting unit cell 2 in which the fuel electrode has sufficient strength is shown. However, the fuel electrode and the air electrode are provided on the front and back surfaces of the flat solid electrolyte having sufficient strength. Alternatively, an electrolyte-supported single cell in which each is disposed, or an air electrode-supported single cell in which the air electrode has sufficient strength may be used.

It is a schematic block diagram at the time of reduction | restoration which shows one Embodiment of the flat type solid oxide fuel cell module which concerns on this invention. (A) is sectional drawing of the principal part which shows the state immediately after inserting the edge part of a connection member in the locking hole of a metal plate, (b) formed the locking part by plastically deforming the edge part of a connection member. It is sectional drawing of the principal part which shows a state. It is a schematic block diagram which shows the state at the time of rated electric power generation. It is sectional drawing which shows the state of the edge part of a connection member. It is a disassembled perspective view of a power generation unit. It is a side view of a fuel cell support type single cell. It is a figure which shows that a fixed load is required from initial reduction to initial energization. It is a figure which shows that it is not necessary to control the load to a stack after initial electricity supply. It is a schematic block diagram of the conventional flat plate type solid oxide fuel cell module provided with the load mechanism.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power generation unit, 2 ... Single cell, 3 ... Separator set, 3A-3D ... Separator, 4 ... Cell stack, 5, 6 ... Metal plate, 7 ... Module container, 8 ... Load mechanism, 10 ... Flat plate type SOFC module, DESCRIPTION OF SYMBOLS 11 ... Solid electrolyte, 12 ... Air electrode, 13 ... Fuel electrode, 20 ... Flat plate type SOFC module, 21 ... Connecting member, 21c ... Locking part, 22 ... Connecting mechanism, 24 ... Locking hole.

Claims (5)

A cell stack using a flat solid oxide fuel cell;
A coupling mechanism comprising two metal plates that sandwich the upper and lower surfaces of the cell stack and a coupling member that couples the metal plates to each other;
With
The connecting member has a thermal expansion coefficient larger than that of the cell stack, one end is fixed to one of the two metal plates, and the other end is formed on the other of the two metal plates. A flat-type solid oxide fuel cell module inserted into the locking hole and locked to the locking hole by a locking portion formed by plastic deformation caused by a load applied during the reduction action. The flat plate type solid oxide fuel cell module according to claim 1,
The locking hole formed in the other metal plate is a flat plate type solid oxide fuel cell module having a non-through hole and having a tip formed wider than the opening edge. The flat plate type solid oxide fuel cell module according to claim 1 or 2,
A flat plate solid oxide fuel cell module in which the other end of the connecting member is formed hollow. The flat plate type solid oxide fuel cell module according to any one of claims 1, 2, and 3,
The coupling mechanism is a flat-plate solid oxide fuel cell module that functions as a load mechanism for the cell stack during power generation. A cell stack using a flat solid oxide fuel cell;
Two metal plates sandwiching the upper and lower surfaces of the cell stack, a coefficient of thermal expansion larger than the coefficient of thermal expansion of the cell stack, one end fixed to one of the two metal plates, and the other end A connecting mechanism comprising a connecting member that is inserted into a locking hole formed on the other of the two metal plates and connects the two metal plates to each other;
A method for operating a flat plate type solid oxide fuel cell module comprising:
Higher than the power generation temperature temperature, subjected to reducing action while applying a load to the cell stack, that in association with the height of the cell stack is lowered to plastically deform the other end of the coupling member in the load by the initial reduction I by the engaging portion formed by a first step of engaging the other end of the connecting member in the locking hole,
A second step of generating power at the power generation temperature while applying a load to the cell stack only by the connection mechanism;
A method for operating a flat plate type solid oxide fuel cell module comprising:

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