JPH0722059A - Flat solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To decrease a temperature difference between a center cell and end cells so as to enhance cell life by causing fuel gas to exchange heat with a cell stack as it circulates through a supply line. CONSTITUTION:Fuel gas supply side buffers 14a-14d are connected to respective internal manifold supply holes 9a-9d and fuel gas discharge side buffers 15a-15d are connected to respective internal manifold discharge holes 10a-10d. Fuel gas discharge holes 16a-16d for discharging fuel gas out of a cell are formed within the respective buffers 15a-15d. The fuel gas rises within a cell stack via a fuel gas preheating pipe 7 at the center of the cell stack, absorbing the heat of the cell and reaching a higher temperature. Heat at the center of a cell plane is absorbed by a gas preheating portion 6, so the fuel gas exchanges heat with the stack as it circulates through the preheating portion 6 serving as a fuel gas supply line. Thereby the temperature difference between the center portion and the peripheral portion of the cell plane is decreased, the fuel gas is efficiently heated, and cell life can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate type solid electrolyte fuel cell, and more particularly to improvement of a fuel gas supply structure.

[0002]

2. Description of the Related Art A fuel cell directly converts chemical energy of a supplied gas into electric energy, so that high power generation efficiency can be expected. Especially solid oxide fuel cell (SOFC)
Has attracted attention as a third generation fuel cell next to the phosphoric acid fuel cell (PAFC) and the molten carbonate fuel cell (MCFC).

In general, SOFC is mainly used as an electrolyte (ZrO ₂ ) as it is called a completely solidified fuel cell.
_Since zirconium oxide (stabilized zirconia) in which a divalent or trivalent metal oxide such as _0.9 (Y ₂ O ₃ ) _0.1 is dissolved is used, there is an advantage that there is no problem of electrolyte (liquid) loss. Further, the charge carriers of these electrolytes are oxygen ions, but the conductivity of these oxygen ions is extremely low at room temperature,
Since the SOFC is normally operated at a high temperature of about 1000 ° C., high-quality exhaust heat can be obtained. When the use of waste heat is included, the energy efficiency can be improved compared to the PAFC and MCFC. More choices,
It also has the advantage that it can be operated at a high current density.

Conventionally, the development of the SOFC was preceded by the cylindrical type, but now, the development of the flat type SOFC, which is expected to increase the power generation efficiency per volume, is in the limelight. Further, in recent years, there has been an increasing demand for higher capacity flat plate SOFCs, and as a result, cells have been made larger (larger area).

[0005]

By the way, conventionally, the fuel gas was heated to a predetermined temperature by an external preheater or the like and then supplied into the battery to generate electric power. It became necessary to supply fuel gas. Therefore, it is necessary to increase the capacity and increase the size of the external preheater and the like, which causes an increase in cost.

Further, as the area of the cell becomes larger, the amount of heat generated during power generation increases, which increases the temperature difference in the cell plane,
There is also a problem that cell deterioration is accelerated. In view of the above problems, it is an object of the present invention to provide a very excellent flat plate solid electrolyte fuel cell that suppresses an increase in cost, suppresses a temperature difference between cell planes, and has an improved cell life.

[0007]

The present invention is characterized by the following in order to solve the above problems. In a flat plate type solid electrolyte fuel cell in which a cell formed by stacking a fuel electrode and an oxidizer electrode on both surfaces of an electrolyte plate and a separator is laminated to form a cell stack, a stack is formed near the center of the cell stack. A feature is that a fuel gas supply passage that penetrates in the stacking direction is formed and the fuel gas exchanges heat with the cell stack while flowing through the fuel gas supply passage. The fuel gas supply passage has an internal / external double structure, and the fuel gas flows in a state of being folded back from one of the inner supply passage and the outer supply passage to the other.

[0008]

According to the above construction, the fuel gas supply passage is formed in the vicinity of the central portion of the cell stack where the heat generation of the cell is hard to be taken and the temperature is higher than the peripheral portion. While flowing through, the heat of the cell is taken away and the temperature becomes high. Therefore, the high-temperature fuel gas can be sufficiently supplied to each cell, and even if the supply amount of the fuel gas increases as the size of the cell increases, the increased amount is supplied to the external preheater or the like as in the conventional case. You don't have to depend on it. As a result, there is no need to increase the capacity or increase the size of the external preheater or the like, so that it is possible to suppress an increase in cost.

Further, since the heat of the central portion of the cell plane is taken by the fuel gas flowing in the fuel gas passage, the temperature difference between the central portion and the peripheral portion of the cell plane is suppressed, and as a result, cell deterioration is suppressed. be able to. Further, according to the above configuration, the fuel gas flows in the cell stack so as to face each other in the stacking direction, so that the temperature difference in the stacking direction in the cell stack is canceled by each other, and the central cell and the end portion of the cell stack are The temperature difference from the side cell is alleviated, and the battery life is also improved.

[0010]

【Example】

[Embodiment] FIG. 1 is a schematic view showing a schematic structure of a flat plate type solid electrolyte fuel cell (10 cell stack) according to an embodiment of the present invention. This cell stack 1 includes a bipolar plate 2 and a cell 3 which will be described later. Are alternately stacked and sandwiched between the fuel gas buffer plate 4 and the gas connector plate 5. A fuel gas preheating portion 6 penetrating in the stacking direction is formed in the center of the cell stack 1, and a fuel gas preheating tube 7 made of insulating ceramics such as alumina extends in the stacking direction in the fuel gas preheating portion 6. It is installed and has a double structure. For airtightness between the cells 3 and the bipolar plates 2 or between the cells 3, a sealant (not shown) made of a non-conductive high viscosity melt such as Pyrex glass was used.

FIG. 2 is a plan view of the bipolar plate 2, which is made of a heat-resistant alloy such as Inconel 600 having a size of 250 mm × 250 mm, and the fuel gas preheating portion 6 is formed in the central portion. Further, ribs 8a to 8d are formed on one surface of the plate 2 as shown in the drawing, and the ribs 8a to 8d are formed.
The oxidant gas flow path is divided into four regions by. Although not shown, ribs having substantially the same shape as the ribs 8a to 8d are also formed on the opposite surface of the plate 2, and the ribs divide the fuel gas passage into four regions. Here, the oxidant gas and the fuel gas are arranged to flow in the cell so as to face each other, and the fuel gas having a high temperature after contributing to the cell reaction flows inside the cell stack 1 so that the fuel gas flows inside the cell stack 1. Manifold supply holes 9a-9d and internal manifold discharge holes 10a-10d are provided, respectively. Incidentally, 11a to 11d in the drawing respectively show internal manifold holes for supplying the oxidizing gas.

FIG. 3 is a plan view of the cell 3, which has substantially the same size as the bipolar plate 2 (250 mm × 250 mm).
Is. This cell 3 has internal manifold holes 9a-9
Electrolyte plate (size 100 mm × 150 mm, thickness 0.2 mm) 12a on which d, 10a to 10d and 11a to 11d are formed
.. to 12d on both sides thereof are combined with four unit cells 3a to 3d formed by arranging fuel electrodes 13a to 13d and an oxidizer electrode (not shown), and the internal manifold holes formed in each of the electrolyte plates 12a to 12d are described above. The fuel gas preheating portion 6 was formed in the central portion while corresponding to that of the bipolar plate 2. In this way, the small single cells 3a to 3d (size 10
If a large cell 3 (size 250 mm x 250 mm) is configured by combining a plurality of 0 mm x 150 mm), a large area of the cell 3 is realized without increasing the size of the electrolyte plates 12a to 12d, which are fragile and easily broken. There is an advantage that you can.

Here, the unit cells 3a to 3d were manufactured as follows. First, electrolyte plates 12a to 12 made of ₃ mol% Y ₂ O ₃ partially stabilized zirconia (PSZ).
A slurry of nickel oxide and 8 mol% Y ₂ O ₃ -stabilized zirconia (YSZ) was applied to one surface of d by a screen printing method, and then baked to burn the fuel electrodes 13a to 13d.
Was formed. On the other hand, the other surface to lanthanum strontium manganate of the electrolyte plate 12 a to 12 d (La _0.9
A slurry of Sr _0.1 MnO ₃ ) and YSZ was applied by a screen printing method and then baked to form an oxidizer electrode (not shown).

FIG. 4 is a perspective view of the gas connector plate 5 provided at the lower end of the cell stack 1. The fuel gas supply side buffers 14a to 14d are connected to the internal manifold supply holes 9a to 9d to discharge the fuel gas. Side buffer 1
5a to 15d are internal manifold discharge holes 10a to 10d.
It is connected to d. Further, in the fuel gas discharge side buffers 15a to 15d, fuel gas discharge holes 16a to 16d for discharging the fuel gas to the outside of the cell are formed.

Hereinafter, a method of preheating fuel gas in the flat plate type solid oxide fuel cell having the above-mentioned structure will be specifically described with reference to FIGS. First, the fuel gas heated to a constant temperature by an external preheater (not shown) outside the cell is used as a fuel gas preheating pipe 7 at the center of the cell stack 1.
The inside of the battery stack 1 is raised via the. Here, in the central portion of the battery stack 1 in which the fuel gas preheating pipe 7 is provided, the heat of the cells is hard to be deprived and the temperature is higher than the peripheral portion,
While the fuel gas flows through the fuel gas preheating pipe 7, the fuel gas deprives the cells of heat generation and becomes higher in temperature. Further, the heat generated in the central portion of the cell plane is taken by the fuel gas preheating section 6, so that the temperature difference between the central portion and the peripheral portion of the cell plane is suppressed.

Next, the heated fuel gas enters the fuel gas buffer plate 4, heats the end cells 3 on the upper end side of the cell stack 1, and then, in the fuel gas preheating section 6 (that is,
Lower the fuel gas preheating tube 7) to the cell stack 1
It is supplied to the fuel gas supply side buffers 14a to 14d provided on the gas connector plate 5 at the lowermost end, and heats the end cells 3 on the lower end side of the cell stack 1. Here, since the flow direction of the fuel gas is opposite between the inner peripheral side and the outer peripheral side of the fuel gas preheating pipe 7, it is possible to suppress the temperature difference in the stacking direction of the cell stack 1. In addition, the fuel gas buffer plate 4 and the fuel gas supply side buffers 14a to 14d
Since the fuel gas is temporarily stored therein, the end cells 3 on the upper end side of the battery stack 1 and the end cells 3 on the lower end side of the battery stack 1 are heated, and the center side cells and the end side cells of the battery stack 1 are heated. It is also possible to suppress the temperature difference between and.

Subsequently, the fuel gas is distributed to the unit cells 3a to 3d while ascending in the cell stack 1 through the internal manifold supply holes 9a to 9d. Then, the high temperature fuel gas after contributing to the cell reaction descends in the cell stack 1 through the internal manifold discharge holes 10a to 10d and enters the fuel gas discharge side buffers 15a to 15d of the gas connector plate 5, Fuel gas discharge hole 16a
It is discharged to the outside of the battery through ~ 16d. In this case, since the fuel gas discharge side is provided on the central portion side of the cell stack 1, heat can be efficiently applied to the fuel gas preheating portion 6 in the central portion. As a result, this fuel gas preheating unit 6
Also, the fuel gas flowing in the fuel gas preheating pipe 7 can be efficiently heated.

The battery stack thus constructed is hereinafter referred to as (A) stack. [Comparative Example] FIG. 5 shows a conventional flat plate solid oxide fuel cell (1
0 is a perspective view showing a zero cell stack),
A cell 33 having a fuel electrode 32 and an oxidizer electrode (not shown) arranged on both sides (size 200 mm × 200 mm) in the same manner as in Example 1 and a bipolar plate 34 are laminated, The gas was preheated only by an external preheater (not shown) provided outside the battery.

The battery stack thus constructed is hereinafter referred to as (X) stack. [Experiment 1] The relationship between the current density and the in-plane temperature difference of the cell was investigated using the (A) stack of the present invention and the (X) stack of the comparative example. The results are shown in FIG.
In the experiment, when the fuel gas and the oxidant gas were supplied at a constant flow rate and the cell temperature was controlled at 1000 ° C in the vicinity of the stack, the central portion of the bipolar plate in contact with the lower surface side of the sixth cell from the bottom of the cell stack. The condition is that the temperature difference between the vicinity and the peripheral portion is measured.

As is apparent from FIG. 6, (X) of the comparative example.
In the stack, the temperature difference in the cell plane significantly increases as the current density increases, whereas in the stack (A) of the present invention, the temperature difference is suppressed to half or less as compared with the stack (X) of the comparative example. It is recognized that In this case, the effective electrode area of the (A) stack of the present invention is much larger than that of the (X) stack of the comparative example, and the calorific value is large. It is clear that the temperature difference of 1 is effectively suppressed.

This is because in the stack (A) of the present invention, the heat generation of the cells is effectively utilized for preheating the fuel gas in the fuel gas preheating section provided in the central portion, so that the temperature difference between the central portion and the peripheral portion is small. It is considered that this is because the (X) stack of the comparative example is less likely to radiate heat at the central portion, while being suppressed.
In the unloaded state, the temperature of the central portion is lower than that of the peripheral portion, so that the (A) stack of the present invention has a larger cell surface temperature difference than the (X) stack of the comparative example. In actual use, the gas flow rate is reduced when there is no load, so this temperature difference is alleviated. [Experiment 2] The relationship between the current density and the temperature difference in the stacking direction of the battery stack was examined using the (A) stack of the present invention and the (X) stack of the comparative example. The results are shown in FIG. 7. . In the experiment, the temperature in the vicinity of the center of the bipolar plate was measured, and the temperature difference between the maximum temperature and the minimum temperature in the battery stack was examined, and the other conditions were the same as those in the experiment 1.

As is apparent from FIG. 7, (X) of the comparative example.
In the stack, the temperature difference is large even when there is no load, and the temperature difference in the stack rises as the current density increases, whereas in the stack (A) of the present invention, the temperature difference in the stack increases regardless of the increase in the current density. It can be seen that the temperature difference is approximately constant. This is because, in the stack (A) of the present invention, the flow of the fuel gas is opposite between the inner peripheral side and the outer peripheral side of the fuel gas preheating tube, so that the temperature difference in the stacking direction in the cell stack is canceled by each other, In addition to suppressing the temperature difference between the cells on the center side and the cells on the end side of the stack, the fuel gas buffer plate 4 and the gas connector plate 5 provided at the uppermost and lowermost ends of the battery stack temporarily receive fuel. It is considered that this is because the gas is stored, so that the temperature of the end-side cells of the battery stack rises and the temperature difference from the central portion in the stacking direction is suppressed. [Other Matters] In the above embodiment, the inside of the fuel gas preheating section 6 has a double structure by the fuel gas preheating pipe 7, but the present invention is not limited to this and has a single or triple structure. It is also possible. However, the double structure is preferable because the temperature difference in the stacking direction can be suppressed by causing the fuel gas to flow in the stacking direction so as to face each other. Although a heat-resistant alloy such as Inconel 600 is used as the material of the bipolar plate 2, it is of course possible to use conductive ceramics such as lanthanum chromite. Furthermore, although the reaction gas is supplied by the internal manifold system, it is of course possible to supply it by the external manifold system.

[0023]

According to the present invention described above, since the fuel gas supply passage is formed in the vicinity of the central portion of the cell stack, in which the heat generation of the cell is hardly taken away and the temperature is higher than the peripheral portion, the fuel gas is the above-mentioned fuel gas. While flowing in the supply passage, the heat of the cell is taken away and the temperature becomes high. Therefore, the high-temperature fuel gas can be sufficiently supplied to each cell, and even if the supply amount of the fuel gas increases as the size of the cell increases, the increased amount is supplied to the external preheater or the like as in the conventional case. You don't have to depend on it. As a result, it is not necessary to increase the capacity or increase the size of the external preheater or the like, so that an excellent effect of suppressing an increase in cost can be achieved.

Further, since the heat of the central portion of the cell plane is taken by the fuel gas flowing in the fuel gas passage, the temperature difference between the central portion and the peripheral portion of the cell plane is suppressed, and as a result, cell deterioration is suppressed. be able to. Further, according to the above configuration, the fuel gas flows in the cell stack so as to face each other in the stacking direction, so that the temperature difference in the stacking direction in the cell stack is canceled by each other, and the central cell and the end portion of the cell stack are The temperature difference from the side cell is alleviated, and the battery life is also improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a flat plate type solid electrolyte fuel cell (10 cell stack) according to an embodiment of the present invention.

FIG. 2 is a plan view of a bipolar plate.

FIG. 3 is a plan view of a cell.

FIG. 4 is a perspective view of a gas connector plate.

FIG. 5 is a perspective view showing a conventional flat plate solid oxide fuel cell (10 cell stack).

FIG. 6 is a stack of the present invention (A) and a comparative example (X).
It is a graph which shows the relationship of current density and cell surface temperature difference 1 when using a stack.

FIG. 7 (A) stack of the present invention and (X) of a comparative example.
6 is a graph showing the relationship between the current density and the temperature difference in the stacking direction of the battery stack when using a stack.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery stack 2 Separator 3a-3d Cell 6 Fuel gas supply passage 12a-12d Electrolyte plate 13a-13d Fuel electrode

[Procedure amendment]

[Submission date] September 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Next, this heated fuel gas enters the fuel gas buffer plate 4 and heats up with the upper end of the cell stack 1.
After the replacement, the fuel gas preheating section 6 (that is, the outer peripheral side of the fuel gas preheating tube 7) descends and is supplied to the fuel gas supply side buffers 14a to 14d provided on the gas connector plate 5 at the lowermost end of the cell stack 1. , Heat is applied to the end cells 3 on the lower end side of the battery stack 1. Here, the fuel gas preheating pipe 7
Since the flow direction of the fuel gas is opposite between the inner peripheral side and the outer peripheral side, the temperature difference in the stacking direction of the cell stack 1 can be suppressed. In addition, since the fuel gas is temporarily stored in the fuel gas buffer plate 4 and the fuel gas supply side buffers 14a to 14d, the end cell 3 on the upper end side of the battery stack 1 and the end cell on the lower end side of the battery stack 1 Three and ten
The heat is exchanged so that the temperature distribution in the battery stack 1 can be made uniform.
Be promoted.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukinori Akiyama 2-18 Keihan Hondori, Moriguchi City Sanyo Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-18 Keihan Hondori, Moriguchi Sanyo Electric Co., Ltd. Within

Claims (2)

[Claims] 1. A flat solid electrolyte fuel cell in which a cell stack is formed by stacking a cell having a fuel electrode and an oxidizer electrode on both sides of an electrolyte plate, and a separator, wherein a central portion of the cell stack is provided. A flat plate type solid electrolyte characterized in that a fuel gas supply passage penetrating the stack in the stacking direction is formed in the vicinity, and the fuel gas exchanges heat with the cell stack while flowing through the fuel gas supply passage. Fuel cell. 2. The fuel gas supply passage has an internal / external double structure, and the fuel gas flows in a state of returning from one of the inner supply passage and the outer supply passage to the other. Flat-plate solid oxide fuel cell.