JP2804769B2 - Internal reforming fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an internal reforming fuel cell, and more particularly, to an internal reforming fuel cell that realizes an internal reforming function and achieves high performance and long life of an internal reforming catalyst. The present invention relates to a reformed fuel cell.

[Conventional technology]

FIG. 6 is a longitudinal sectional view showing a part of the configuration of a conventional internal reforming fuel cell disclosed in, for example, Japanese Patent Publication No. 59-24504.

In the drawing, reference numeral (1) denotes an electrolyte layer, (2) denotes a fuel gas electrode adjacent to the electrolyte layer (1), and (3) denotes an oxidizing gas opposed to the fuel gas electrode (2) via the electrolyte layer (1). The electrode, (4a) is a fuel gas side current collector supporting the fuel gas electrode (2) and passing generated current, and (4b) is an oxidation supporting the oxidized gas electrode (3) and passing generated current. The gas-side current collector, (5a) and (5b) are fuel gas flow path forming materials for forming a fuel gas flow path and an oxidizing gas flow path, respectively, and an oxidizing gas flow path forming material, and (6) is a fuel. A fuel gas flow path provided to face the gas electrode (2);
A separator plate for separating the oxidizing gas channel provided opposite to the oxidizing gas electrode (3), and (7) is a reforming catalyst provided in the fuel gas channel.

Here, a unit cell is constituted by the electrolyte layer (1), the fuel gas electrode (2), and the oxidizing gas electrode (3), and the internal reforming fuel cell includes the unit cell, the fuel gas side current collector (4a) And a oxidizing gas side current collector (4b), a fuel gas flow path forming material (5a), and an oxidizing gas flow path forming material (5b), which are stacked on each other with a separator plate (6) interposed therebetween. The figure shows the main part. In the drawing, arrow A indicates the flow direction of the oxidizing gas, and arrow B indicates the flow direction of the fuel gas.

 Next, the operation will be described.

Fuel gas mainly containing hydrocarbons or alcohols / steam is supplied in the direction of arrow B, and oxidizing gas mainly containing oxygen and carbon dioxide is supplied in the direction of arrow A. It is introduced into the flow path and the oxidizing gas flow path.

Hydrocarbon in the fuel gas is reformed by the action of the reforming catalyst (7) into a fuel gas containing hydrogen and carbon monoxide as main components as shown in the following formulas (1), (2) and (3). You.

This reaction is an endothermic reaction as a whole, and directly uses heat energy produced as a by-product in the fuel cell.

CH ₄ + H ₂ O → CO + 3H ₂ + 49.3kcal / mol… (1) CO + H ₂ O → CO ₂ + H ₂ −9.8 kcal / mol (3) According to the reactions shown in equations (1), (2) and (3), hydrogen and carbon monoxide generated in the fuel gas flow path The fuel gas passes through the hole of the gas-side current collector plate (4a), reaches the fuel gas electrode (2), and reacts as shown in the following equations (4) and (5).

CO + H ₂ O → H ₂ + CO ₂ (5) On the other hand, oxygen and carbon dioxide in the oxidizing gas supplied by the arrow A pass through the hole of the oxidizing gas side current collector (4b), and (6)
The reaction shown in the equation occurs.

Through these chemical and electrochemical reactions, the chemical energy of the fuel gas is converted into electrical energy and by-product thermal energy.

As mentioned earlier, most of this by-product thermal energy is used for the reaction heat of hydrocarbon decomposition in the gas flow path, resulting in a large improvement in thermal efficiency, which is a feature of the internal reforming method. It has become one of.

Here, the reforming catalyst (7) is, for example, a carrier having nickel or magnesia as a main component, on which nickel having activity as a catalyst is supported. Generally, such a reforming catalyst (7) is composed of an electrolyte. , And its activity as a catalyst is greatly reduced by being contaminated by the electrolyte.

This is because the electrolyte in the electrolyte layer (1) usually moves in the form of vapor or droplets to the fuel gas flow path and contaminates the reforming catalyst (7), thereby reducing the activity of the reforming catalyst (7). is there.

As means for preventing such a decrease in the activity of the reforming catalyst (7) due to the electrolyte, a device provided with an electrolyte removing substance for removing an electrolyte component from the fuel gas between the reforming catalyst and the fuel gas electrode has been invented. ing.

FIG. 7 is a longitudinal sectional view showing a part of the configuration of an internal reforming fuel cell provided with an electrolyte removing substance (8) disclosed in Japanese Patent Application Laid-Open No. 62-186471.

The electrolyte removing substance (8) is, for example, in the form of particles and is disposed in a space in contact with the fuel gas side current collector plate (4a) in the fuel gas flow path formed by the fuel gas side flow path forming material (5a). I have. Further, a reforming catalyst (7) is disposed in a space in contact with the separator plate (6) in the fuel gas flow path.

In this embodiment, the electrolyte component contained in the fuel gas is removed by a chemical reaction with the electrolyte removing substance (8),
It is possible to prevent the reforming catalyst (7) from being contaminated by the electrolyte component and to stably maintain the catalytic activity of the reforming catalyst (7) for a long period of time.

[Problems to be solved by the invention]

In a conventional internal reforming battery, an electrolyte removing substance is arranged in a space in contact with a fuel gas side current collector plate (4a) of a gas flow path, and a reforming catalyst is arranged in a space in contact with a separator plate (6). Since the reforming catalyst filling section (12) and the electrolyte removal substance filling section (13) are both open at the inlet and outlet of the fuel gas,
The fuel gas containing hydrocarbon steam as a main component, which has flowed into the electrolyte removing material filling section (13), is discharged out of the cell without being reformed, the hydrogen partial pressure in the cell is reduced, and the output voltage of the internal reforming cell is reduced. However, there is a problem that the temperature is reduced.

In addition, since the fuel gas supplied to the battery reaction at the fuel gas electrode flows to the electrolyte removing substance filling portion and hardly to the reforming catalyst filling portion, the reforming reaction is promoted by the battery reaction which is a feature of the internal reforming battery. There is a problem that it is not possible to realize high-efficiency power generation due to its small size. There was a problem. The conventional device has a problem to solve such a problem.

The present invention has been made to solve the above-described problems, and uses an electrolyte removing substance to prevent a reduction in the activity of a reforming catalyst due to an adverse effect of an electrolyte and to allow a fuel gas to escape from a cell without being reformed. It is an object of the present invention to obtain an internal reforming fuel cell having a fuel gas flow path so as not to be discharged.

[Means for solving the problem]

An internal reforming fuel cell according to the present invention is configured such that a fuel gas flow path is divided into a reforming catalyst filling section and electrolyte removing substance filling sections provided adjacently on both sides with the reforming catalyst filling section interposed therebetween. The filling portion is configured to be a portion separated from the fuel gas electrode, and the electrolyte removing substance filling portion is configured to be a portion opened to the fuel gas electrode, and the fuel gas is first flowed to the catalyst filling portion to cause a reforming reaction, Next, a pressure difference is generated between the flow paths to flow the reformed fuel gas to the fuel gas electrode to cause a cell reaction. Then, after the electrolyte component in the fuel gas is removed by the electrolyte removing substance, the next step is performed again. The fuel gas flow path is configured to flow to the catalyst filling section.

(Operation)

In the present invention, the fuel gas containing the electrolyte component subjected to the battery reaction flows to the next catalyst filling section after only the electrolyte component is removed by the electrolyte removing substance, so that the reforming catalyst is not adversely affected by the electrolyte. It operates stably for a long period of time, and promotes the progress of the reforming reaction by the battery reaction.

〔Example〕

Hereinafter, the present invention will be described with reference to the drawings showing one embodiment.

In FIG. 1, (1) is an electrolyte layer,
(2) fuel gas electrode, (3) oxidizing gas electrode, (4a)
Is the fuel gas side current collector, (4b) is the oxidizing gas side current collector, (5
a) is a fuel gas flow path forming material, (5b) is an oxidizing gas flow path forming material, (6) is a separator plate, and (7) is a reforming catalyst.

Next, reference numeral (8) denotes an electrolyte removing substance having a function of removing an electrolyte component in the fuel gas. Arrow A in the figure indicates the flow direction of the oxidizing gas as in the conventional example, and arrow B indicates the flow direction of the fuel gas.

In the conventional example, the fuel gas electrode (2) is located at the upper part and the oxidizing gas electrode (3) is located at the lower part. However, in this embodiment, the structure is reversed in order to prevent the electrolyte from adhering to the catalyst due to soaking up. I have.

Next, the embodiment shown in FIG.
Is shown.

This is a corrugated plate having a continuous concave and convex surface. The fuel gas inlet (P) closes the inlet of the concave-side flow path that opens to the fuel gas electrode, and the convex-side flow path isolated from the fuel gas electrode. It is configured to open the entrance of the road. A slit (9) is provided between the concave side flow path and the convex side flow path so that gas can flow.

 FIG. 3 shows the flow of the fuel gas in this embodiment.

The fuel gas enters the reforming catalyst filling section (12) of the convex side flow path at the fuel gas inlet (P), passes through the slit (9), and then passes through the electrolyte removing substance filling section (13) of the concave side flow path. Again flows to the next reforming catalyst filling section (12).

Next, the operation of the internal reforming fuel cell of this embodiment will be described.

The fuel gas containing hydrocarbons or alcohols as main components flows into the flow path of the catalyst filling section (12), and is operated by the reforming catalyst (7) to obtain the equations (1), (2), and (3). Accordingly, the gas is reformed into a gas containing hydrogen and carbon monoxide as main components.

The reforming catalyst (7) is separated from the fuel gas electrode by a flow path plate, and is not adversely affected by the electrolyte.

Next, since the outlet side of this flow path is closed, the reformed fuel gas generates a pressure difference, passes through the slit (9), and flows into the concave flow path opening to the fuel gas electrode. ,
The holes in the fuel gas side current collector (4a) are diffused and supplied to the fuel gas electrode (2).

The hydrogen / carbon monoxide supplied to the fuel gas electrode (2) is consumed in the fuel gas electrode (2) by an electrochemical / chemical reaction represented by the formulas (4) and (5), and is produced as electric energy. It produces heat energy and produces steam and carbon dioxide as reaction products.

The generated water vapor and carbon dioxide contain an electrolyte component, and if left as it is, the activity of the reforming catalyst downstream therefrom is reduced.

Therefore, in order to remove the electrolyte component, the flow path opening to the fuel gas electrode (2) is filled with the electrolyte removing substance (8). As the electrolyte removing substance (8), at least one or more of SiO ₂ , TiO ₂ , B ₂ O ₃ , Al ₂ O _3, etc., which are highly reactive with an alkali metal such as lithium, potassium or sodium as an electrolyte component Is used. The fuel gas from which the electrolyte components have been removed by the action of the electrolyte removing substance (8) flows into the next reforming catalyst filling section (12) as shown in the flow of the fuel gas in FIG. Hydrogen is reformed.

By repeating the above operation, the reforming catalyst can maintain the catalytic activity for a long time without being adversely affected by the electrolyte, and can promote the progress of the reforming reaction by the battery reaction.

In the above embodiment, the fuel gas flow path forming material is made corrugated with irregularities, and the inlet on the concave side and the outlet on the convex side are closed to generate a pressure difference between the flow paths. The method is not limited to the above method.

For example, as shown in FIG. 4, a partition plate (10) that is inclined in the direction of the flow path is provided on the convex side of the fuel gas flow path, and divided into two flow paths (14) and (15). The fluid flows into the flow path (14) of the first catalyst-filled portion, and the cross section of the flow path decreases as going downstream, and the pressure difference causes the flow path ( After moving to 16), the same effect can be obtained by flowing the flow through the flow path (15) of the second catalyst filling section whose cross section increases in the downstream direction.

In another embodiment, corrugated corrugated sheets as shown in FIG. 5 are displaced by half pitch to form a zigzag arrangement, and fuel gas is flowed from the catalyst-filling portion on the convex side to the electrolyte-removing-material filling portion on the concave side, The same effect can be obtained by flowing again to the next convex-surface-side catalyst filling section.

〔The invention's effect〕

As described above, according to the present invention, in the internal reforming fuel cell, the fuel gas flow path is divided into the reforming catalyst filling section and the electrolyte removal substance filling section, and the fuel gas is catalyzed by the pressure difference between the flow paths. After flowing from the filling section to the electrolyte removing substance filling section, it is configured to flow again to the next catalyst filling section to remove the electrolyte in the fuel gas, so that the reforming catalyst is not adversely affected by the electrolyte, The catalyst activity is maintained for a long period of time, and the progress of the reforming reaction by the cell reaction, which is a characteristic of the internal reforming cell, is promoted. Is obtained.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing the configuration of an internal reforming fuel cell according to one embodiment of the present invention, FIG. 2 is a layout view of the fuel gas flow path member of FIG. 1, and FIG. FIG. 4A and FIG. 5A are explanatory diagrams showing the flow of fuel gas during operation, and FIG. 4A is an explanatory diagram showing the flow of fuel gas according to two other embodiments of the present invention;
5B is a partial perspective view showing the fuel gas flow channel material of FIG. 5A, FIG. 6 is a partial perspective view showing the structure of a conventional internal reforming battery, and FIG. 7 is provided with a conventional electrolyte removing substance. FIG. 2 is a partial perspective view of the internal reforming fuel cell that has been used. (1) ... electrolyte layer, (2) ... fuel gas electrode, (3)
… Oxidizing gas electrode, (4a)… Fuel gas side current collector, (4
b) Oxidizing gas side current collector, (5a) ... fuel gas flow path forming material, (5b) ... oxidizing gas flow path forming material, (6) ... separator plate, (7) ... reforming Catalyst, (8) ... electrolyte removing substance, (9) ... slit, (12) ... reforming catalyst filling section, (13) ... electrolyte removing substance filling section. In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 8/00-8/24

Claims (1)

(57) [Claims] 1. A unit cell comprising a fuel gas electrode and an oxidizing gas electrode facing each other with an electrolyte layer interposed therebetween, and a fuel gas flow path provided opposite the fuel gas electrode and an oxidizing gas electrode facing the oxidizing gas electrode. In a fuel cell stack formed by alternately stacking separator plates separating an oxidizing gas flow path provided, the fuel gas flow path includes a plurality of adjacent reforming catalyst filling portions and an electrolyte removing material. And the fuel gas electrode, wherein the reforming catalyst filling portion is a portion separated from the fuel gas electrode, and the electrolyte removal substance filling portion is a portion opened to the fuel gas electrode. Flows from the reforming catalyst filling section to the electrolyte removal substance filling section, and then causes a pressure difference between the flow paths so as to flow again to the next reforming catalyst filling section. Internal reforming fuel cell.