JPS60241674A - Fused carbonate type fuel cell - Google Patents

Abstract

PURPOSE:To reform fuel gas efficiently in a fuel cell through simple structure by making many grooves in both faces of a porous member and filling with catalist to provide a branch gas flow reforming board and forming a bipolar partition board. CONSTITUTION:A fused carbonate type fuel cell is formed by providing a pair of bipolar partition boards 21 on both faces of unit cell 1 composed of an electrolytic layer 5 sandwitched by an oxidizing agent electrode 3 and a fuel electrode 4 then laminating plural sets of unit cells 1. The partition board 21 is formed by providing sidewall members 7a, 7b and a branch gas flow reforming board 22 at one side of partition board body 6 while sidewall members 8a, 8b and an oxidizing agent gas flow path 9b at the other side where the branch gas flow reforming board 22 is formed by making many V-grooves in both faces of porous member while crossing perpendicularly with passing direction of fuel gas P and filling with catalyst 25. Consequently, contact between the fuel gas and the catalyst 25 can be improved through simple structure resulting in efficient reforming of fuel gas in the cell.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to an internal reforming type molten carbonate fuel cell in which fuel gas reforming means is provided inside the fuel cell main body, and particularly relates to a molten carbonate fuel cell having a fuel gas reforming means provided inside the fuel cell main body. This invention relates to a molten carbonate fuel cell that can improve quality and efficiency.

[Technical background of the invention and its problems]

A fuel cell uses a gas that is easily oxidized, such as hydrogen, and
DC power is obtained by reacting an oxidizing gas such as oxygen through an electrochemical reaction process in an appropriate electrolyte, and depending on the electrolyte used, there are phosphoric acid type, molten carbonate type, and solid electrolyte type. It is broadly divided into

Among these fuel cells, the above-mentioned molten carbonate type fuel cells are designed to operate at a temperature of about 650°C.
Its main parts are generally constructed as shown in FIG.

That is, the fuel cell main body X is constructed by stacking a plurality of unit cells 1 with bipolar separators 2 interposed therebetween, which will be described later.

The unit cell 1 is constructed by providing a flat electrolyte layer 5 between a pair of gas diffusion electrode plates made of a nickel alloy porous material, that is, an oxidizer electrode 3 and a fuel electrode 4. The electrolyte layer 5 is one in which a carbonate electrolyte such as lithium carbonate or potassium carbonate is held by a ceramic holding material made of lithium aluminate or the like.

The bipolar separator 2 has a separator body 6 made of stainless steel 1.
side wall member 7a made of stainless steel in order to form gas flow paths in directions perpendicular to each other on both sides of the side wall member 7a;

7b, 8a, and 8b are brazed in parallel to both sides of each surface. And these side wall members 7a, 7
b.

The groove formed by 8a, 8b and the 60th surface of the separator body is connected to the gas flow path (fuel gas P flow path and oxidant gas Q).
flow path). In addition, each of these gas flow paths has
Stainless steel corrugated plates 9a and 9b are fitted in order to substantially divide the gas flowing there. Further, on each end face of the side wall members 7a, 7b, 8a, 8b,
Steps are provided to fit the gas diffusion electrode plates 3 and 4, respectively, and the gas diffusion electrode plates 3 and 4 are fitted into the step portions.
4 is fitted into the side wall member 7a.

7b, sj 8b and the electrolyte layer 5 are wet-sealed to prevent leakage of the gas guided to the gas supply section. In addition, the above-mentioned wet seal has an electrolyte of, for example, Li2COa/2CO3,62/
In the case of a two-element eutectic composition with a molar ratio of 38, this is done by melting the electrolyte at 488°C when the battery operating temperature Ill is raised to 650°C.

Incidentally, in a molten carbonate fuel cell having such a structure, hydrocarbons such as methane, ethane, and propane, or alcohols such as methanol and ethanol are used as the fuel gas supplied to the fuel electrode 4. However, even if these gases are supplied as they are to the fuel electrode 4, the reaction rate is slow and it is difficult to obtain practically sufficient power. Therefore, when using these gases, it is necessary to reform them into a hydrogen-rich gas using a reformer before supplying them to the fuel cell.

Conventionally, such a reformer was installed outside the fuel cell main body. However, in order to carry out the reforming reaction,
Since sufficient thermal energy is required, if the reformer is installed outside the fuel cell body in this way, the means for supplying the thermal energy necessary for the reforming reaction must be installed outside the fuel cell. Become. Therefore, recently, an internal reforming type fuel cell has been proposed in which a reformer is installed inside the fuel cell body, with the aim of effectively utilizing the thermal energy inside the fuel cell and simplifying the system. ing.

This internal reforming type molten carbonate fuel cell has a rectangular wave type separator 11, as shown in FIG.
The upper and lower parts of the separator 11 are separated, and the fuel gas P is placed in the upper recess of the separator 11.
This separator plate 1 is filled with a catalyst 12 for reforming.
A groove 14, which serves as a flow path for the fuel gas P, is formed in the surface of the fuel electrode 13 which is adjacent to the fuel electrode 1 at the upper part of the figure and is in contact with the separator plate 11 in a direction perpendicular to the filling zone of the catalyst 12.

With such a configuration, the fuel gas P comes into contact with the catalyst 12 while flowing through the groove 14 and is reformed.

Since the reforming reaction of the fuel gas by this catalyst is carried out at 650° C., which is the normal operating temperature of the fuel cell, the reforming reaction proceeds at a sufficiently fast rate. As a result, hydrogen-rich fuel gas can be generated inside the fuel cell main body Y, and the above-mentioned effects can be achieved.

However, in the molten carbonate fuel cell configured in this way, the fuel gas P flowing through the groove 14 and the catalyst 1
Since there is only a small contact with 2, there was a drawback that the reforming efficiency of the fuel gas was poor.

Therefore, the fuel gas may not be completely reformed, and some unreformed fuel gas may reach the gas discharge side. Moreover, if the fuel cell body has such a structure,
In addition to requiring groove processing in the fuel electrode 13, there were other problems such as difficulty in separating the fuel gas P and the oxidant gas Q at the end face of the separator 11.

[Purpose of the invention]

The present invention was made based on such problems,
The purpose is to provide a molten carbonate fuel cell using an internal reforming method, which can efficiently reform fuel gas and has a simple configuration. There is a particular thing.

[Summary of the invention]

The present invention provides a gas distribution plate formed of a porous material provided adjacent to a fuel electrode and dividing fuel gas introduced from the outside and guiding it to the fuel electrode, and a gas distribution plate embedded inside the gas distribution plate. The present invention is characterized by comprising a catalyst layer for reforming the fuel gas flowing through the inside of the gas distribution plate.

〔Effect of the invention〕

According to the present invention, since the catalyst layer is buried inside the gas distribution plate that divides the fuel gas, the catalyst layer is located exactly at the position where the gas flow is blocked. When the catalyst layer is present at such a position, it is possible to significantly increase the contact area between the catalyst layer and the fuel gas compared to the conventional method. Moreover, since the fuel gas is made turbulent by the catalyst layer, the reforming efficiency of the fuel gas can be greatly increased.

Furthermore, the present invention has a very simple structure, in which a gas distribution plate made of a porous material with a catalyst layer embedded therein is provided adjacent to the fuel electrode. Therefore, since there is no need to perform any special processing on the fuel electrode, separator, etc., it is possible to provide an internal reforming type molten carbonate fuel cell without complicating the structure.

Note that if the gas distribution plate is made of an electron conductive material, it can also have a current collecting function for each unit battery, and
If the gas distribution plate has a predetermined mechanical strength, it can also function as a support for each unit cell.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained based on illustrated embodiments.

In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals. Therefore, a detailed explanation of the overlapping parts will be omitted.

Embodiment 1 FIG. 3 is a diagram showing the main structure of a molten carbonate fuel cell according to a first embodiment, that is, the fuel cell main body Z.

This fuel cell body 2 differs from the conventional fuel cell body X shown in FIG. 1 in the configuration of the bipolar separator 21. The bipolar separator 21 according to this embodiment includes side wall members 7a, 7
A new gas flow reforming plate 2 is installed in place of the corrugated plate 9a that was conventionally fitted into the groove formed by b and the upper surface of the separator body 6 in the figure.
2 are fitted together.

As shown in FIG. 4, this gas distribution reforming plate 22 includes a plurality of grooves 24 extending in a direction perpendicular to the flow direction of the fuel gas P on both sides of a gas distribution plate 23 made of a porous material. are formed alternately, and these V grooves 24 are filled with a catalyst 25.

In this embodiment, the gas distribution plate 23 is made of a nickel porous body (porosity 90%) with a thickness of 2m+.
A piece cut out to a size of 180 m was used. and,
On both sides of this gas flow distribution plate 23, five holes are alternately arranged at a depth of 1.
The V-grooves 24 of the shoe are formed, and these V-grooves 24 are filled with alumina.
Magnesia supported nickel catalyst 25 (specific surface area 32Td
/g) and ethanol was filled. After volatilizing the ethanol, the obtained gas distribution reforming plate 22 was assembled into the fuel cell main body Z shown in FIG. The fuel cell main body 2 is composed of three layers of unit cells 1, and the corrugated plate 9b provided in the oxidant gas flow path of the fuel cell main body Z is made of stainless steel.

A reactant gas manifold, an end plate, a tightening bar, etc. (not shown) were attached to the fuel cell main body 2 thus obtained to assemble a fuel cell.

Then, this fuel cell was placed in a Matsufuru furnace and heated to 650°C.
It was operated at a temperature of In this operation experiment, as the fuel gas P and the oxidizing gas Q supplied to the fuel cell, ■Fuel gas...methane (CH4), water (H20):S
,/C-2,5 Oxidizer scum...70Air/CO2 ■Fuel gas...methanol (CH30H) + water (H2
0); s/c=2.5 Oxidizing gas: Two types of 70A ir/CO2 were used.

Example 2 Only the gas distribution plate 23 of Example 1 was made of stainless steel 316.
A similar experiment was conducted using a porous foam L (porosity: 92%).

Example 3 A similar experiment was conducted in Example 1 except that only the catalyst 25 was replaced with a nickel catalyst supported on lithium aluminate.

Comparative Example The concave portion of the fuel type 1311 of the rectangular wave separator 11 shown in FIG. 2 was filled with an alumina-magnesia supported nickel catalyst, and the conventional fuel cell main body Y shown in the same figure was assembled, in the same manner as in Example 1. We conducted an experiment.

When we measured the cell voltage of each unit cell with respect to the current density in Examples 1 to 4 and the conventional example, we found that when methane was used as the fuel gas, the results were as shown in Figure 5. When methanol was used, the results shown in FIG. 6 were obtained.

As is clear from this figure, the cell characteristics (A, B, C, D) of the fuel cells of Examples 1 to 4 can be improved compared to the cell characteristics (E) of the fuel cell of the comparative example. It could be confirmed.

In addition, when the conversion efficiency of fuel gas reforming in each experiment was measured, the results shown in the table below were obtained.

As is clear from this table, it was confirmed that the fuel cells according to Examples 1 to 4 had better conversion efficiency in fuel gas reforming than the comparative example.

As described above, according to these embodiments, fuel gas reforming can be achieved with a simple improvement of simply replacing the corrugated plate provided in the fuel gas flow path of a fuel cell with a conventional structure with a gas distribution reforming plate. conversion efficiency can be increased. Furthermore, since the gas distribution plate 23 in these embodiments is made of a porous material of nickel or stainless steel, it has both a current collection function and a support function for each unit cell.

Note that the present invention is not limited to the above embodiments. For example, as shown in FIG. 7, the grooves 32 formed in the gas flow divider plate 31 may be rectangular or trapezoidal. It may be formed as follows. These grooves can be formed by various methods such as machining and press working. In addition to the above-mentioned catalysts, the catalysts filled in these grooves include, for example, a nickel or nickel alloy catalyst on a support made of alumina, calcia-alumina, alumina-zirconia, lithium zirconate, strontium titanate, lithium titanate, or boron nitride. You may use the one provided.

These catalysts are not particularly limited to those packed in the form of slurry.

Further, the gas flow reforming plate and the fuel electrode may be integrally configured, and the gas flow flow reforming plate may be made of a nickel alloy.

In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

Figure 1 is an exploded perspective view showing the main parts of a conventional thin metal plate type molten carbonate fuel cell, and Figure 2 shows the configuration of the main parts of a previously proposed internal reforming type molten carbonate fuel cell. FIG. 3 is an exploded perspective view showing the first to fourth parts of the present invention.
FIG. 4 is an exploded perspective view showing the configuration of the main parts of the internal reforming molten carbonate fuel cell according to the embodiment, FIG. 4 is a perspective view showing the gas distribution reforming plate in the fuel cell, FIG. 6
The figure is a characteristic diagram for explaining the cell characteristics of the fuel cells according to the first to fourth embodiments in comparison with a comparative example, and FIG. It is a perspective view showing a quality board. 1... Unit battery, 2.21... Bipolar separator, 3.
...Oxidizer electrode, 4, 13...Fuel electrode, 5...Electrolyte plate, 6...Separator body, 7a, 7b, 8a, 8
b-...Side wall member, 9a, 9b...Corrugated plate, 11...
・Separation plate, 12.25.33... Catalyst, 22... Gas distribution reforming plate, 23.31... Gas distribution plate, X, Y,
Z: Fuel cell body, P: Fuel gas, Q: Oxidizing gas. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 7 Figure 3 Figure 5

Claims (1)

[Scope of Claims] (1) An oxidizing agent electrode and a fuel electrode are provided on both sides of an electrolyte layer made of carbonate, an oxidizing agent gas is supplied to the oxidizing agent electrode, and a fuel gas is supplied to the fuel electrode; In a molten carbonate fuel cell in which an electromotive reaction is caused between both gases and the carbonate, the fuel gas provided adjacent to the fuel electrode and introduced from the outside is divided and guided to the fuel electrode. It is characterized by comprising a gas flow distribution plate made of porous corpus luteum, and a catalyst layer embedded inside the gas flow distribution plate to reform the fuel gas flowing through the gas flow distribution plate. Molten carbonate fuel cell. (2) The catalyst layer is formed by filling a plurality of grooves formed in the gas distribution plate with a catalyst in a direction perpendicular to the direction of introduction of the fuel gas introduced into the gas distribution plate. The molten carbonate fuel cell according to claim 1, characterized in that the catalyst layer comprises alumina, alumina-magnesia, calcia-alumina, alumina-zirconia, lithium aluminate, lithium zirconate, and strontium. The molten carbonate fuel cell according to claim 1, characterized in that the fuel cell is a nickel catalyst or a nickel alloy catalyst provided on a support made of titanate, lithium titanate, or boron nitride. 4) The molten carbonate fuel cell according to claim 1, wherein the gas distribution plate is made of stainless steel, nickel, or a nickel alloy. (5) The fuel electrode and the gas distribution plate The molten carbonate fuel cell according to claim 1, wherein the plate is integrally formed.