JPH0650646B2 - Molten carbonate fuel cell stack - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molten carbonate fuel cell stack.

[Conventional technology]

FIG. 6 shows a conventional example of a molten carbonate fuel cell stack. As shown in the figure, the basic unit of the fuel cell is an electrolyte plate 1, an anode 2 and a cathode 3 sandwiching the electrolyte plate 1, and a separator 5 having a gas flow path 4 for supplying gas to each of the electrodes 2 and 3. Etc.

Conventional header plate 6 is located at the top of the stack,
One header plate 6 has both an anode header 7 and a cathode header 8, and both the anode gas and the cathode gas flow from the upper and lower ends toward the center,
Gas is supplied to each cell. Note that Japanese Patent Application Laid-Open Nos. 58-115772 and 58-164168 are related to this.

[Problems to be solved by the invention]

The maximum voltage per cell of a molten carbonate fuel cell is 1.
It is about 1V, and several hundreds of cells must be stacked in order to realize large-capacity power generation for electric power in the future, but conventionally, the number of stacked cells is small and the above-mentioned structure has no problem.

However, if the conventional structure is used for high stacking, the number of cells to which one header has to supply gas increases, and the distribution of gas to each cell becomes uneven. Therefore, the number of cells sandwiched between headers may not be changed, and a large number of modules having upper and lower headers may be stacked to support high stacking. However, this increases the number of pipes connected to the header, resulting in an extremely complicated structure.

Besides this. In the case of high stacking, stack productivity and cell cooling characteristics during operation become new problems, and there is a demand for development of stacks corresponding to these.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a molten carbonate fuel cell stack having a simple structure, capable of uniformly distributing gas, and having excellent productivity. It is intended.

[Means for solving problems]

For the above purpose, the header plate is composed of an anode header plate and a cathode header plate, and a group of cells supplying anode gas by the anode header plates are stacked above and below a single cathode header plate inserted at approximately the center of the cell stack. Then, the cathode gas is supplied from one cathode header plate to the plurality of stacked cell groups.

[Action]

The intended purpose is achieved by providing the above-mentioned means, which will be described below. The above means is based on the result of studying the gas flow rate of the molten carbonate fuel cell and the relationship between the gas flow rate and the gas distribution. The mass balance of the molten carbonate fuel cell system is, for example, ERP EM-1670, FEL Cell Power Plant Integrated Systems Eva Aration (EPRI EM-1670, Fuel Cell Power Plant I).
Although it is introduced in many documents such as Integrated Systems Evaluation), the common feature is that the flow rate of the cathode gas is 5 to 6 times higher than the flow rate of the anode inlet gas. This is because, in order to maximize system efficiency, a flow rate of about 1.2 times the amount of gas required for the reaction is passed on the anode side, while air containing oxygen at twice the required amount is passed on the cathode side. Is.

Next, the distribution of the flow to each cell will be described. The flow in the fuel cell can be evaluated as a model in which a plurality of branch pipes (corresponding to the gas flow path of each cell) are connected to a mother pipe (corresponding to a manifold) as shown in FIG. FIG. 7 shows how much flow rate flows in each cell when 1.25 times the gas amount necessary for the reaction is flown on the anode side, and the flow rate ratio of each cell is taken on the vertical axis. The cell number is plotted on the horizontal axis. As is clear from the figure, in the case of the number of stacks N in (a) in the figure, the distribution amount is larger as it is closer to the gas inlet side (smaller cell number), and the distribution amount becomes smaller as the distance from the gas inlet increases, The flow rate ratio to each cell exceeds 1.0,
It is shown that the required amount is distributed to each cell.
On the other hand, in the case where the number of stacked layers in (b) is 2N, the drift ratio becomes large, and as a result, the flow rate ratio becomes 1.0 in the cells exceeding the cell number N
, Which indicates that the required amount is not being supplied.

On the other hand, in FIG. 8, the flow rate ratio of each cell is plotted on the vertical axis and the cell number is plotted on the horizontal axis, and the cathode side is evaluated. As is clear from the figure, it has been found that the cathode side can supply a gas of a required flow rate or more to each cell even if the number of stacked layers is 2N. This is because the oxygen amount is twice as much as the required amount on the cathode side, and the total flow rate of the cathode gas is large, resulting in a large pressure loss at the inlet and outlet parts, and the distribution of the gas supply amount to each cell. Because it became flat.

As described above, the flow rate conditions under which the molten carbonate fuel cell is efficiently operated differ in the number of stacks by which the gas can be uniformly distributed on the anode side and the cathode side. The number is about 2N on the cathode side, where N is on the anode side. Therefore, the gas header plate is divided into the anode side and the cathode side, and the cathode gas is supplied from one cathode header plate to a plurality of unit cell groups to which the anode gas is supplied from one anode header plate. I did.

〔Example〕

Hereinafter, the present invention will be described based on the illustrated embodiments. An embodiment of the present invention is shown in FIGS. Since the same parts as those of the conventional one are designated by the same reference numerals, the description thereof will be omitted. In this embodiment, the header plate is composed of an anode header plate 9 and a cathode header plate 10, and a cell group 11 for supplying anode gas by the anode header plate 9 above and below one cathode header plate 10 thus constructed. Were stacked, and the cathode gas from one cathode header plate 10 was supplied to the plurality of stacked cell groups 11. By doing so, it is possible to obtain a molten carbonate fuel cell stack having a simple structure, capable of uniformly dispersing gas, and having excellent productivity.

That is, the fuel cell stack was composed of one cathode header plate 10, two anode header plates 9, upper and lower end plates 12, and cells 11a laminated between them. The cathode header plate 10 includes a cathode inlet / outlet tube base 13a, 13b, and cathode inlet / outlet headers 8a, 8
b, cathode inlet / outlet manifolds 14a, 14b are formed. Further, a cathode gas flow channel 4a and an anode gas flow channel are formed on the upper and lower surfaces of the cathode header plate 10, respectively.

On the other hand, the anode header plate 9 includes the anode inlet / outlet nozzle stubs 15a and 15b and the anode inlet / outlet headers 7a and 7b.
b, anode inlet / outlet manifolds 16a, 16b, anode gas flow passage 4b, cathode gas flow passage 4a, cathode inlet manifold 14a, cathode outlet manifold 14b.
Is formed.

By doing so, the cathode gas flows from the cathode inlet nozzle 13a to the cathode inlet header 8a, and is divided into upper and lower portions to flow into each cell 11a through the cathode inlet manifold 14a. Some gas passes through the cathode inlet manifold 14a of the anode header plate 9 and flows into each cell 11a above the anode header plate 9. After the reaction, it flows out from each cell 11a to the cathode outlet manifold 14b, and flows through this to the cathode outlet header 8
b, and flows out from the cathode outlet tube base 13b.

The anode gas also flows in the order of the anode inlet nozzle 15a, the anode inlet manifold 16a, each cell 11a, the anode outlet manifold 16b, and the anode outlet nozzle 15b. But,
Since the cathode header plate 10 is not provided with the anode manifold, the anode gas does not flow through the cathode header plate 10 and the upper and lower modules are independent systems.

Further, the anode header plate 9 is located in the center of the cell group 11, and the number of cells of the cell group 11 on one side of the anode header plate 9 is set so that the required gas amount can be distributed to all the cells 11a under the flow rate condition of this stack. .

The upper and lower end portions of the module are upper and lower end plates 12, and the gas flow paths are formed on only one side. To further stack the cells 11a, the modules shown in FIG. 1 described above may be stacked.

The table below shows the results of comparing the number of header plates and the number of inlet / outlet pipes when the present embodiment is applied to the number of cells of 4N with the conventional example.

As is clear from the table, in the case of this embodiment, the number of header plates and the number of pipes can be significantly reduced while ensuring gas distribution to each cell as compared with the conventional example. The structure can be simplified. The anode pipe and the cathode pipe shown in the table are pipes connected to the anode inlet / outlet tube base and the cathode inlet / outlet tube base, respectively.

As described above, according to the present embodiment, it is possible to obtain a highly stackable stack having excellent productivity with a simple structure having a small number of header plates and gas pipes while ensuring gas distribution to each cell. it can.

3 and 4 show another embodiment of the present invention. In this embodiment, the cathode header plate 10a is
The gas passages were not provided on both sides, and the separator 5a was directly attached to both sides, and only the cathode manifold 17 was provided on the directly attached separator 5a. By doing so, the cathode header plate 10
a is a cathode manifold on a separator 5a which is not provided with gas passages on both sides thereof and is directly attached to both ends thereof.
Since only 17 is provided, it is safer and easier to work than the above case.

That is, the upper and lower surfaces 18a of the cathode header plate 10a,
18b has no gas flow path and is smooth, with a recess in the center
19 was set up. Further, no gas flow rate was formed on the separator surface 20 in contact with the cathode header plate 10a, and only the cathode manifold 17 of the manifold was provided on the separator 5a.

By doing so, the gas flowing into the cathode inlet header 8a flows from the cathode inlet manifold 14a to the cathode manifold 17 of the separator 5a. Cathode header plate 10a and separator 5 in contact therewith
The seal between a and a is made at the metal contact surfaces of both. The tightening pressure of the fuel cell is several kg / cm ² a, which is lower than the necessary tightening pressure for metal contact, but since the recess 19 is provided in the center of the cathode header plate 10, the tightening load is not applied to the seal 21. I will concentrate. It should be noted that although a packing should be used at a place where a gas seal is usually required, the contact portion between the cathode header plate 10a and the separator 5a is also required to have electrical conductivity, and therefore metal contact is used.

According to this embodiment, the following effects can be obtained. That is, since only the cathode gas (air) flows to the portion where the gas seal is required on the contact surface between the cathode header plate 10a and the separator 5a, for example, the seal 21
Even if there is a slight leak from the part, only air will flow out, and the anode gas (hydrogen) will not go out of the stack, so the safety is high. In addition, in the manufacturing process, the upper and lower cell groups can be separately manufactured in large quantities, and in the final assembly step, the two cell groups and the cathode header plate 10a can be overlapped to complete the module, and small elements can be assembled. Can be manufactured in a simple manner. Therefore, it is excellent in mass productivity. If some cells in the stack become unusable due to some reason, it is possible to remove one set on the anode side including the cells and install a new one. In particular, since the surface of the seal 21 is in contact with metal, the work is easy. That is, it is excellent in maintainability.

FIG. 5 shows still another embodiment of the present invention.
In this embodiment, the number of cells of the cell group 11A located between the cathode header plate 10 and the anode header plate 9 is N, and the cell group above the anode header plate 9 is N.
The number of 11B cells was set to N / 2. By doing so, the cell group 11B on the upper side of the anode header plate 9 becomes 1/2 of the number of cells of the cell group 11A between the cathode header plate 10 and the anode header plate 9, which is smaller than that in the above case. Can be better cooled.

That is, when stacking a plurality of modules 22, the header plates 9 and 10 of either the anode or the cathode can be arranged at equal intervals in the entire stack, and the reaction heat of the cell can be more averaged by the cathode and the anode than in the above case. Can be removed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a molten carbonate fuel cell stack having a simple structure, capable of uniformly distributing gas, and having excellent productivity.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a molten carbonate fuel cell stack of the present invention, FIG. 2 is an exploded perspective view of a header plate of the same embodiment, and FIG. 3 is a molten carbonate fuel cell of the present invention. FIG. 4 is an exploded perspective view around the cathode header plate of another embodiment of the fuel cell stack, FIG. 4 is a vertical sectional side view showing a contact state between the cathode header plate and the separator of another embodiment, and FIG. A front view of still another embodiment of the molten carbonate fuel cell stack, FIG. 6 is an exploded perspective view of a conventional molten carbonate fuel cell stack, and FIG. 7 is a flow rate ratio and cell number of each cell on the anode side. And FIG. 8 is a characteristic diagram showing the relationship between the flow rate ratio of each cell on the cathode side and the cell number. 1 ... Electrolyte plate, 2 ... Anode, 3 ... Cathode, 4
... Gas flow path, 4a ... Cathode gas flow path, 4b ... Anode gas flow path, 5, 5a ... Separator, 7a ... Anode inlet header (anode header), 7b ... Anode outlet header (anode header) , 8a ... Cathode inlet header (cathode header), 8b ... Cathode outlet header (cathode header), 9 ... Anode header plate, 10, 10a ... Cathode header plate, 11, 11A, 11B ... Cell group, 14a ...... Cathode inlet manifold, 14b …… Cathode outlet manifold, 16a …… Anode inlet manifold, 16b …… Anode outlet manifold, 17 …… Cathode manifold.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naruyoshi Kobayashi 502 Kintatecho, Tsuchiura City, Ibaraki Prefecture Inside the Institute of Mechanical Research, Hiritsu Manufacturing Co., Ltd. (56) Reference JP-A-60-241659 (JP, A) JP-A Sho 58-169778 (JP, A)

Claims (4)

[Claims] 1. A cell group in which a plurality of unit cells each having an electrolyte plate sandwiched between an anode and a cathode are stacked with a separator interposed therebetween, and upper and lower ends thereof are closed by an upper end plate and a lower end plate, respectively, and a cell group of the cell group A cathode header plate inserted in a central position, a first anode header plate inserted in the cell group at a position between the upper end plate and the cathode header plate, and a position between the cathode header plate and the lower end plate. A molten carbonate fuel cell stack including a second anode header plate inserted into the cell group, wherein the separator has an anode inlet manifold and an anode outlet manifold on one opposing peripheral portion and the other opposing. A cathode inlet manifold and a cathode outlet manifold are provided in the periphery, and the anode facing manifold faces the anode. An anode gas flow passage that allows the anode gas to flow from the cathode inlet manifold to the anode outlet manifold, and a cathode gas flow passage that allows the cathode gas to flow from the cathode inlet manifold to the cathode outlet manifold on the side facing the cathode. The cathode header plate has a cathode inlet header for supplying cathode gas to the cathode inlet manifold of the separator, and a cathode outlet header for collecting cathode gas from the cathode outlet manifold of the separator, the first and second anodes The header plate includes an anode inlet header that supplies anode gas to the anode inlet manifold of the separator, an anode outlet header that collects anode gas from the separator anode outlet manifold, and A cathode inlet manifold for communicating the cathode inlet manifolds of the separators arranged with the node header plate interposed therebetween, and a cathode outlet manifold for communicating the cathode outlet manifolds of the separator arranged with the anode header plate sandwiched, The cathode gas supplied to the cathode inlet header of the cathode header plate flows from the cathode inlet manifold of the separator through the cathode gas flow channel and is supplied to each unit cell located between the upper end plate and the lower end plate, and then the separator. Through the cathode outlet manifold to the cathode outlet header, and the anode gas supplied to the anode inlet header of the first anode header plate is discharged from the anode inlet manifold of the separator. After being supplied to each unit cell located between the upper end plate and the cathode header plate through the node gas flow path, it passes through the anode outlet manifold of the separator to the anode outlet header of the first anode header plate. The anode gas that flows out and is supplied to the anode inlet header of the second anode header plate flows from the anode inlet manifold of the separator through the anode gas flow path and is located between the cathode header plate and the lower end plate. A molten carbonate fuel cell stack, characterized in that, after being supplied to the cells, it flows through the anode outlet manifold of the separator to the anode outlet header of the second anode header plate. 2. The first anode header plate is disposed in the center of the cell group located between the upper end plate and the cathode header plate, and the second anode header plate is the cathode header plate and the lower end. The molten carbonate fuel cell stack according to claim 1, wherein the molten carbonate fuel cell stack is arranged in a central portion of a cell group located between the plates. 3. The number of cells arranged between the upper end plate and the first anode header plate is about half the number of cells arranged between the first anode header plate and the cathode header plate. And the number of cells arranged between the lower end plate and the second anode header plate is half the number of cells arranged between the second anode header plate and the cathode header plate. The molten carbonate fuel cell stack according to claim 1. 4. The cathode header plate is not provided with a gas flow path, and a separator having a cathode inlet manifold and a cathode outlet manifold is directly attached to both surfaces of the cathode header plate. Alternatively, the molten carbonate fuel cell stack according to item 3.