JPH0927329A - Molten carbonate fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molten carbonate fuel cell with simple cooling structure, small in size, high in cooling effect, with excellent power generating performance by using an oxidizing agent gas in common as a cooling gas. SOLUTION: A stacked cell 1 is constituted by stacking a plurality of unit cells each comprising an electrolyte plate 12, an anode and a cathode arranged on each side of the electrolyte plate 12, and a separator 13 for forming a gas flow path for each of a fuel gas 6 and an oxidizing gas 3 on the outside of each electrode. The fuel gas 6 which is supplied from a supply pipe 7 through a lower header 2, passed through a fuel gas flow path within the unit cell, then exhausted from an exhaust pipe 8, and the oxidizing gas 3 which is supplied from a supply pipe 4 through an upper header 21, passed through a cooling gas flow path 11 formed by passing through the electrolyte plate 12, both electrodes, and the separator 13, then exhausted from an exhaust pipe 5 through an oxidizing gas flow path within the unit cell are electrochemically reacted to generate electric power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated fuel cell, and more particularly to a cooling structure for a molten carbonate fuel cell in which a plurality of unit cells are laminated.

[0002]

2. Description of the Related Art As a conventional cooling structure for a laminated fuel cell, for example, there is one disclosed in Japanese Utility Model Publication No. 27503/1990. The cooling structure of the phosphoric acid fuel cell described in this is such that a cooling plate is laminated in the laminated cell in the same manner as the stack,
A cooling medium pipe is externally attached to the cooling plate to supply and discharge the cooling medium.

[0003]

In the above prior art, the operating temperature is higher than that of the phosphoric acid type such as the molten carbonate type,
There is a problem in that the number of cooling plates must be increased for a fuel cell that needs to cool the entire stacked cell, which increases the stack height and increases the size of the entire cell. Further, since the piping for the cooling medium is attached from the outside, there is a problem that the piping system is increased in the structure of the laminated battery and the piping system becomes more complicated when the number of cooling plates is increased. In addition, such a complicated piping system has a problem that the stack height changes due to thermal expansion of the piping system due to temperature or expansion of the laminated battery due to heat or contraction due to surface pressure load.
A solution to this is not described in the above-mentioned disclosed technique, and if a structure that eliminates the above influence is provided, the structure of the laminated battery becomes more complicated.

Therefore, an object of the present invention is to provide a molten carbonate fuel cell which has a simple and compact cooling structure, has a high cooling effect and is excellent in power generation performance.

[0005]

The above object is to provide an electrolyte plate for holding a molten carbonate, an anode electrode and a cathode electrode sandwiching the electrolyte plate from both sides, a fuel gas and an anode electrode outside the anode electrode and the cathode electrode. In a molten carbonate fuel cell in which a plurality of unit cells each composed of a separator forming each gas flow path for flowing an oxidant gas are stacked, the electrolyte plate, the anode electrode, the cathode electrode, and the Penetrating the separator, providing a cooling gas passage for flowing a cooling gas for cooling the unit battery, connecting the cooling gas passage and the oxidizing gas passage, the oxidizing gas It is achieved by flowing the cooling gas flow path to the oxidant gas flow path.

[0006]

With the above structure, the oxidant gas is also used as the cooling gas flowing through the cooling gas passage provided in the laminated battery so as to penetrate in the stack height direction. The temperature distribution in the laminated battery can be made uniform without providing a means for supplying and discharging gas, and both the compact battery structure and the improved battery performance can be achieved. In addition, since the cooling gas flow path is provided in the highest temperature part in the laminated battery and the highest temperature part is preferentially cooled, the difference in temperature between the highest and lowest is small and especially the highest temperature is low, improving only the power generation performance. Not
The thermal deterioration of the battery constituent materials is prevented and the reliability is improved. Then, since the oxidant gas flow paths of the unit cells are adjacent to each other back to back and the flow directions of the oxidant gas are opposite flows,
Due to the temperature interaction between the unit cells increased by the reaction heat, the temperature distribution in the entire battery becomes more uniform, which leads to a more compact battery structure and improved battery performance.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a laminated structure of a molten carbonate fuel cell according to one embodiment of the present invention. As shown in the figure, the laminated battery 1 is externally attached to the lower end of the laminated battery 1.
There is a lower header 2 having a plenum for supplying and exhausting gas to and from the laminated battery 1. In the lower header 2, an air supply pipe 4 and an exhaust pipe 5 for the oxidant gas 3,
Air supply pipe 7 and exhaust pipe 8 for fuel gas 6 and cooling gas 9
And the exhaust pipe 10 are attached. The cooling gas flow path 1 for the cooling gas 9 is provided in the upper direction of the lower header 2.
1, an electrolyte plate 12, a separator 13, and an anode electrode and a cathode electrode (not shown) are stacked, and the exhaust pipe 10 penetrates through the electrolyte plate 12, both electrodes and the separator 13 and the lower header 2. A cooling gas flow passage 11 for allowing the cooling gas 9 to flow therethrough is formed to form a molten carbonate fuel cell.

In the molten carbonate fuel cell having such a structure, the operating temperature during power generation is usually about 650 ° C., and the fuel gas 6 and the oxidant gas 3 also flow in at a temperature close thereto. Then, an electrochemical reaction occurs in the battery to generate power. The reaction heat at this time raises the temperature inside the battery. The temperature rise is not uniform depending on the gas flow, and the temperature distribution in the battery becomes non-uniform. If the temperature distribution inside the battery is not uniform and the temperature difference between the maximum temperature and the minimum temperature becomes large, especially if the maximum temperature becomes high, not only the power generation performance will decrease, but also the thermal deterioration of the battery components will lead to a significant increase in reliability. It becomes a problem. Therefore, in order to reduce the temperature difference and the like in the battery, a cooling gas flow path 11 is provided in the highest temperature part, and the cooling gas 9 is caused to flow therethrough to cool the highest temperature part so that the temperature distribution in the battery is made uniform. It will be transformed. The dimensions and arrangement of the cooling gas flow channel 11 are determined as appropriate by previously obtaining an optimum value by a simulation test or desk analysis.

The gas flow in the battery will be described. The fuel gas 6 supplied from the outside of the cell flows into the lower header 2 from the air supply pipe 7, and is distributed from the lower header 2 to the unit cells through the fuel gas internal supply manifold 14. Then, an electrochemical reaction is performed in the unit cell, and the fuel gas 6 and the like remaining in the reaction is returned to the lower header 2 through the internal discharge manifold 18 for the fuel gas and is discharged from the exhaust pipe 8 to the outside of the cell. Further, the oxidant gas 3 flows into the lower header 2 from the air supply pipe 4, and is distributed to the unit cells via the internal supply manifold 15 for the oxidant gas, and the oxidant gas 3 remaining in the reaction is oxidized. After passing through the internal discharge manifold 19 for the agent gas, it returns to the lower header 2 and is discharged from the exhaust pipe 5 to the outside of the battery. Further, the cooling gas 9 is
A cooling gas passage 11 provided in each unit battery flows from an upper header not shown in FIG. 1, flows into the lower header 2, and then is discharged from the exhaust pipe 10 to the outside of the battery.

Here, the arrangement of the cooling gas passage 11 will be described. FIG. 7 shows the temperature distribution in the cell of the conventional molten carbonate fuel cell. Such temperature distribution can be examined in advance based on the power generation test result of the simulated battery and the calculation result of the desktop analysis. The cooling gas flow path 11 is provided at a position which is the highest temperature part of the temperature distribution shown in FIG. 7, for example, in the highest temperature part of the unit battery as shown in FIG. is there. As a result, the highest temperature part inside the battery is preferentially and intensively cooled, and each part of the battery is also cooled, so that the maximum temperature is reduced and the temperature distribution is made uniform.

As described above, according to this embodiment, the temperature of the highest temperature part of the laminated battery can be lowered, the temperature distribution in the battery can be improved, and the battery performance and the reliability can be improved. Furthermore, even if the laminated battery is thermally displaced in the stacking height direction due to reaction heat, the cooling gas flow channel 11 of the present embodiment is thermally displaced integrally with the laminated battery, and thus is not easily affected by heat. It can be said that the reliability in this respect is improved.

FIG. 2 is a view showing a laminated structure of a molten carbonate fuel cell of another embodiment. A cooling gas passage 11 for cooling the unit battery is provided by penetrating the electrolyte plate 12, both electrodes and the separator 13, and the cooling gas passage 11 and the oxidizing gas passage are connected to each other to form an oxidizing gas. 3 is a configuration in which the cooling gas passage 11 is made to flow to the oxidizing gas passage so that the oxidizing gas 3 used for the electrochemical reaction is also used as the cooling gas 9. As shown in the figure, the oxidant gas 3 supplied from the air supply pipe 4 to the upper header 21 flows through the cooling gas flow passage 11 in the battery to cool the highest temperature part, and then the oxidant gas 3 of the lower header 2 is cooled. Flows into the plenum. Then, via the internal supply manifold 15 for the oxidant gas, the oxidant gas 3 that is supplied as the original reaction gas, that is, the oxidant gas 3 and is used in the electrochemical reaction into each unit cell is used for internal discharge. It returns to the lower header 2 again via the manifold 19, and is discharged from the exhaust pipe 5 to the outside of the battery.

Compared with the structure in which the cooling gas 9 is separately supplied and discharged to cool the highest temperature portion, the structure of this embodiment does not require the supply and discharge means for the cooling gas, so that the battery structure is simplified. effective. In particular, since the oxidant gas 3 supplied to the battery is heated while passing through the cooling gas flow path 11, there is also an effect that it is simpler than the conventional structure having the oxidant gas heating means separately.

FIG. 3 is a diagram showing a partial structure of a molten carbonate fuel cell of another embodiment. As shown in the figure, the heat transfer fins 31 are provided in the cooling gas passage 11. The heat of the highest temperature part in the battery is transferred to the heat transfer fins 31, and the cooling gas 9 touches the heat transfer fins 31, so that the heat transfer with the cooling gas 9 is good and the cooling effect of the highest temperature part is large. Become. As a result, cooling can be performed with a small flow rate of the cooling gas 9, which leads to downsizing of the entire battery and reduction of the battery cost.

FIG. 4 is a diagram showing a partial structure of a molten carbonate fuel cell of still another embodiment. In the laminated structure of the present embodiment, the oxidant gas flow paths face each other so that the flow directions of the oxidant gas 3 flowing through one oxidant gas flow path and the other oxidant gas flow path adjacent to each other back to back face each other. It is a configuration arranged. That is, as shown in the figure, in one gas flow direction, the oxidant gas 3a flows from the air supply pipe 4a to the lower header 2
Flowing in, returning to the lower header 2 through the inside of the battery, and being discharged from the exhaust pipe 5a, in the other gas flow direction, the oxidant gas 3b flows from the air supply pipe 4b into the lower header 2 and then from the exhaust pipe 5b. It is the direction of discharge. Further explanation will be given with reference to the following figure.

FIG. 5 is a diagram showing a gas flow of the oxidant gas 3 flowing in the separator 13 of FIG. 4 in a counter flow. FIG. 5A is a diagram showing a gas flow on the separator 13 on the cathode A electrode surface side, and FIG.
It is the figure which showed the gas flow on the separator 13 by the side of an electrode. The cathode A electrode surface side and the cathode B electrode surface side are adjacent to each other back to back. A cooling gas passage 11 is provided in the center of the separator 13 and the like.

The gas flow of the oxidant gas 3 is, for example, as shown in FIG.
On the cathode A electrode surface side of (a), the oxidant gas 3a is
The gas flows from the one internal supply manifold 15a at the outer peripheral portion of the separator 13 into the battery, becomes a gas flow 41 as indicated by an arrow in the figure, and flows to the one internal exhaust manifold 19a at the outer peripheral portion.

On the cathode B electrode surface side in FIG. 5B, the oxidant gas 3b flows from the other internal supply manifold 15b to the other internal discharge manifold 19b in the direction indicated by the arrow in the figure. Flows. That is, the gas flow between the A electrode surface side and the B electrode surface side has a reverse flow relationship with the separator 13 as the back, in other words, the A electrode surface side and the B electrode surface side.
The oxidant gas flow paths on the electrode surface side are arranged so as to be a counter flow. As described above, by disposing the internal supply manifold 15 and the internal discharge manifold 19 for the oxidant gas so that the gas flow directions of the oxidant gas 3 are opposite to each other inside the laminated battery, The temperature difference between the maximum temperature and the minimum temperature can be reduced as compared with the unidirectional flow. This will be described with reference to the following figure.

FIG. 6 is a diagram showing an example of temperature distribution on the cathode electrode surface of FIG. The relationship between the distance from the inlet of the internal supply manifold 15 and the temperature of the cathode electrode surface is shown. The curve shown by the solid line in the figure shows the relationship in the case of the counter flow of the present embodiment, and the curve shown by the alternate long and short dash line in the figure shows the relationship in the case of the conventional one-way flow. The curve (a) shown by the broken line in the figure is the temperature distribution on the cathode A electrode surface, and the curve (b) is that on the cathode B electrode surface. However, these curves are
This is a case where the cooling gas passage 11 is not provided.

As shown in the curve (a) of the cathode A electrode surface,
The temperature change was 550 ° C at the inlet and around 720 ° C at the outlet. Since the gas flow is in the opposite direction on the adjacent cathode B electrode surface,
The curve (b), which is the opposite of the curve (a), shows the temperature change. Therefore, in the entire battery, both temperatures interact with each other, resulting in the temperature of the countercurrent curve shown by the solid line,
It is 620 ℃ at the inlet and 720 ℃ at the outlet. In this case, the temperature difference between the maximum temperature and the minimum temperature is about 100 ° C.

On the other hand, the one-way flow curve shown by the alternate long and short dash line in the figure is the same as the curve (a). Therefore the inlet part 550 ℃,
The outlet is 720 ° C, and the temperature difference is about 170 ° C. As a result, the counterflow of this embodiment can reduce the temperature difference by about 40% as compared with the unidirectional flow of the conventional example. However, even if the flow of the oxidant gas 3 is only counter flow, the temperature distribution can be improved as compared with the one-way flow, but the temperature difference between the maximum temperature and the minimum temperature is still about 100 ° C, and the temperature distribution It can be said that it is necessary to make it uniform.

Therefore, in the embodiment of FIG. 4 described above, in addition to the structure of the counter flow, as shown in FIG. 6, a cooling gas passage 11 is provided in the central portion of the battery, which is the highest temperature portion, and the temperature distribution The thing which aimed at homogenization is shown. Therefore, when the oxidant gas 3 is the counter flow, the temperature difference is smaller than that in the one-way flow as described above. Therefore, if the configuration of the counter flow and the installation of the cooling gas passage 11 are adopted together. It can be said that the temperature distribution of the entire battery can be made uniform with a smaller flow rate of the cooling gas 9, and the battery is more compact and the battery cost can be reduced. As described above, according to this example, it is possible to easily make the temperature distribution of the entire laminated cell uniform, and to obtain a fuel cell having excellent performance, life, and reliability.

[0023]

According to the present invention, the oxidizing gas is also used as the cooling gas and the laminated battery is cooled by the oxidizing gas to improve the temperature distribution in the battery, so that the battery structure is made compact and the battery performance is improved. There is an effect that both the improvement of is achieved. In particular, since the oxidant gas supplied to the battery is heated while passing through the cooling gas flow path, there is an effect that the structure becomes simpler than the conventional structure having the oxidant gas heating means separately.

Further, by concentratingly cooling the highest temperature portion of the battery, or by providing heat transfer fins in the cooling gas passage, or by making the flow of the oxidant gas countercurrent, This has the effects of preventing heat deterioration of the material, making the entire battery compact, and reducing the battery cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a laminated structure of a molten carbonate fuel cell according to an embodiment of the present invention.

FIG. 2 is a view showing a laminated structure of a molten carbonate fuel cell of another embodiment according to the present invention.

FIG. 3 is a view showing a partial structure of a molten carbonate fuel cell of another embodiment.

FIG. 4 is a view showing a laminated structure of a molten carbonate fuel cell of still another embodiment.

5 is a diagram showing a gas flow of an oxidant gas 3 flowing in a counter flow in the separator 13 of FIG.

6 is a diagram showing an example of temperature distribution on the cathode electrode surface of FIG.

FIG. 7 is a diagram showing a temperature distribution in a cell in a molten carbonate fuel cell of a conventional example.

[Explanation of symbols]

1: laminated battery, 2: lower header, 3: oxidant gas, 4,
7: air supply pipe, 5, 8, 10: exhaust pipe, 6: fuel gas,
9: cooling gas, 11: cooling gas flow path, 12: electrolyte plate, 13: separator, 21: upper header.

Claims (4)

[Claims] 1. An electrolyte plate for holding a molten carbonate, an anode electrode and a cathode electrode sandwiching the electrolyte plate from both sides, and a fuel gas and an oxidant gas which flow outside the anode electrode and the cathode electrode, respectively. In a molten carbonate fuel cell in which a plurality of unit cells each of which is composed of a separator forming a gas flow path are laminated, the unit penetrates through the electrolyte plate, the anode electrode, the cathode electrode, and the separator. Providing a cooling gas passage for flowing a cooling gas for cooling the battery, connecting the cooling gas passage and the oxidant gas passage,
A molten carbonate fuel cell, wherein the oxidant gas is caused to flow from a cooling gas channel to the oxidant gas channel. 2. The molten carbonate fuel cell according to claim 1, wherein the cooling gas passage is provided at the highest temperature portion of the unit cell. 3. The molten carbonate fuel cell according to claim 1, wherein heat transfer fins are provided in the cooling gas passage. 4. The flow direction of the oxidant gas flowing through one of the oxidant gas flow passages and the other of the oxidant gas flow passages that are adjacent to each other in a back-to-back manner according to claim 1 or 2. The molten carbonate fuel cell is characterized in that the oxidant gas flow paths are arranged opposite to each other.