JPH01167958A - Internally reforming type molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To lengthen the life of a cell by making a reforming catalyst face the oxidizing agent electrode of an adjacent unit fuel cell through a separator and arranging no oxidizing agent passage between the reforming catalyst and the oxidizing agent electrode. CONSTITUTION:When fuel containing hydrocarbon and steam are supplied to a fuel passage 13, fuel reforming reaction arises by a reforming catalyst 14 to produce hydrogen, carbon monoxide, and carbon dioxide. The amount of heat necessary for reforming reaction is supplied to the reforming catalyst 14 from an oxidizing agent electrode 12, in which exothermic reaction arises, through an electrolyte matrix 16 and a fuel electrode 11, and at the same time from the oxidizing agent electrode 12 of an adjacent unit fuel cell. Since an oxidizing agent passage 15 does not exist between the reforming catalyst 14 and the oxidizing agent electrode 12 of the adjacent unit fuel cell, the reforming catalyst 14 locates in the nearest place to the oxidizing agent electrode 12 of the adjacent unit fuel cell, and heat is effectively transferred to the reforming catalyst 14 from the oxidizing agent electrode 12. The temperature drop of the reforming catalyst caused by endothermic reforming reaction is prevented and the condensation of electrolyte vapor on the reforming catalyst is retarded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internally reforming molten carbonate fuel cell that generates power while reforming a fuel containing, for example, hydrocarbons inside the cell.

[Prior Art] An example of a conventional internal reforming molten carbonate fuel cell is shown in FIG. In FIG. 4, 1 is an electrolyte matrix made of porous ceramic whose voids are impregnated with carbonate, 2 is a fuel electrode made of porous nickel, etc.
3 is an oxidizer electrode made of porous nickel oxide or the like. The fuel electrode 2 and the oxidizer electrode 3 are arranged to face each other with an electrolyte 71 and a sock 1 interposed therebetween.

A flat separator 8 separates the fuel and the oxidizer, and a fuel passage 4 is formed between the separator 8 and the fuel electrode 2. A spacer 5 is arranged in the fuel passage 4 to form a space. A reforming catalyst 9 is disposed in at least a portion of this fuel passage 4.

An oxidant passage 6 is formed between the separator 8 and the oxidant electrode 3, and a spacer 7 is disposed within the oxidant passage 6. The spacers 5, 7 and the separator 8 often also serve as current collector plates. As described above, an internal reforming molten carbonate fuel cell is constructed.

In the internal reforming molten carbonate fuel cell having the above configuration, when fuel such as hydrocarbon and steam are supplied to the fuel passage 4, the hydrocarbon reacts with the steam due to the catalytic reaction of the reforming catalyst 9, and the hydrogen , - reformed to carbon oxide and carbon dioxide. In the case of hydrocarbons or methane, this reaction is represented by the following equation:

C114+H20→3H2+GO(1)11□0+C
O→ H2+ (:0□ (2) The generated hydrogen and carbon monoxide diffuse into the electrolyte matrix 1 through the pores of the porous fuel electrode 2. On the other hand, air and carbon dioxide are present in the oxidant passage 6. is supplied and diffuses into the electrolyte matrix 1 through the pores of the porous oxidizer electrode 3. Inside the fuel electrode 2, (:l), the electrochemical reaction of equation (4) occurs, and the oxidizer electrode 3 An electrochemical reaction according to formula (5) occurs inside the fuel cell, and a voltage is therefore generated between the fuel electrode 2 and the oxidizer electrode 3, which is extracted as electric power to the outside.

H2+CO3”−-+H20+CO2+2e (3)
GO+CO3'-→2(:02 + 2e
(4) 37202+CO2+2e-+CO-+''-(5
) The above electrochemical reaction is an irreversible reaction and is an exothermic reaction as a whole. The reforming reaction that occurs in the reforming catalyst 9 is an endothermic reaction, and the amount of heat required to sustain the reforming reaction is
This is covered by the amount of heat generated during the above battery reaction. In this way, by combining exothermic and endothermic reactions in the battery, heat utilization can be carried out efficiently, and the chemical equilibrium of the reforming reaction is improved because the generated hydrogen and carbon monoxide are immediately consumed by the electrochemical reaction. This is a characteristic of internally reforming molten carbonate fuel cells, which move toward producing more hydrogen and carbon monoxide, and therefore have higher power generation efficiency.

[Problems with the Prior Art] When the cell reaction is divided into the fuel electrode side and the oxidizer electrode side, an endothermic reaction occurs in the former, and an exothermic reaction occurs in the latter. Therefore, it is important to efficiently transfer the heat generated at the oxidizer electrode to the reforming catalyst in order to carry out reforming efficiently.

In a conventional internal reforming molten carbonate fuel cell, there is an oxidant passage 6 between the separator 8 and the oxidizer electrode 3, but the oxidant passage 6 contains air and carbon dioxide as its main components. Since the oxidizing agent flows through the oxidizing agent passage 6, the structure is such that heat is difficult to move through the oxidizing agent passage 6. In other words, the heat supplied from the oxidant electrode 3 of the adjacent cell to replenish the endothermic amount of the reforming catalyst 9 is absorbed by the reforming catalyst 9 because the oxidant passage 6 exists between the reforming catalyst 9 and the oxidant electrode 3. It is not effectively supplied to the catalyst 9. Therefore, the temperature of the reforming catalyst 9 tends to drop, and therefore, the electrolyte vapor evaporated from the electrolyte matrix 1 moves to the reforming catalyst 9 and condenses on the catalyst, reducing the activity of the catalyst, thereby reducing the battery life. There are some issues with performance deterioration.

Therefore, in order to solve the above problems,
In the fuel cell described in No. 4505.

A fuel passageway is provided that is in thermal communication with the heat generating surface between the fuel cells or is isolated from the electrolyte, and a reforming catalyst is disposed in the passageway to prevent contact between the reforming catalyst and the electrolyte. . However, in the technology described in F, the reforming catalyst and the fuel electrode are separated, so the hydrogen produced by the reforming catalyst is not consumed in the electrochemical reaction on the spot. Therefore, since the chemical equilibrium of the reforming reaction does not shift toward producing a large amount of hydrogen and carbon monoxide as in the above-mentioned internal reforming battery, there is a limit to increasing the power generation efficiency.

The present invention efficiently transfers heat generated on the oxidizer electrode side to the reforming catalyst side, thereby preventing a drop in temperature on the reforming catalyst side, and reducing the possibility of electrolyte vapor condensing on the reforming catalyst. The purpose of the present invention is to provide an internally reforming molten carbonate fuel cell that can extend the life of the cell.

[Means for Solving the Problems] The present invention proposed as a means for solving the above problems is as follows.

A fuel electrode and an oxidizer electrode face each other with an electrolyte matrix in between, and the other side of the fuel electrode has a fuel passage filled with at least a part of a reforming catalyst, and the other side of the oxidizer electrode has an oxidizer passage. In a fuel cell configured in a multilayer structure by stacking four EL fuel cells, the reforming catalyst faces the oxidizer electrode of an adjacent unit fuel cell via a separator, and the reforming catalyst and An internally reforming molten carbonate fuel cell characterized in that there is no oxidant passageway between the oxidizer electrode and the oxidizer electrode.

[Operation] In the above fuel cell, when fuel containing hydrocarbons and steam are supplied into the fuel passage, the hydrocarbons react with the steam by the reforming catalyst and are reformed into hydrogen, carbon oxide, and carbon dioxide. Ru. The heat for this purpose is covered by the amount transferred from the oxidant electrode of the adjacent unit cell via the separator, and the amount transferred from the oxidant electrode of the same unit cell via the electrolyte matrix and the fuel electrode.

The hydrogen and carbon monoxide thus produced diffuse into the pores of the porous fuel electrode towards the electrolyte matrix. On the other hand, air and carbon dioxide are supplied to the oxidizer passageway, and diffuse through the pores of the porous oxidizer electrode toward the electrolyte matrix to cause electrochemical reactions inside the electrode and inside the oxidizer electrode. A reaction occurs, and as a result, a voltage is generated between the fuel electrode and the oxidizer electrode, which can be extracted externally as electric power.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which lO is a separator formed in parallel continuous uneven shapes, 11 is a fuel electrode aligned with the lower surface of the separator 10, and 12 is a separator. With the oxidizer electrode aligned to the top surface of 10,
The separator IO is sandwiched between a fuel electrode 11 and an oxidizer electrode 12 of an adjacent unit fuel cell.

Reference numeral 13 denotes a fuel passage formed by the separator 10 and the fuel electrode 11, and a reforming catalyst 1 is installed in this fuel passage 13.
4 is filled. Note that the reforming catalyst 14 may be filled in the entirety of the fuel passage 13 or may be in a part thereof.

15 is an oxidant passage formed between the separator lO and the oxidizer electrode 12.

Reference numeral 16 denotes a ``liquid solution matrix'' C sandwiched between the fuel electrode 11 and the oxidizer electrode 12.

Next, its effect will be explained. When fuel containing hydrocarbons and steam are supplied to the fuel passage 13, a reforming reaction of the fuel occurs by the reforming catalyst 14, and hydrogen, carbon oxide, and carbon dioxide are produced. At this time, the amount of heat required for the reforming reaction is 1. The oxidizing agent that causes the exothermic reaction is passed from the electrode 12 to the reforming catalyst 1 through the electrolyte matrix 16 and the fuel electrode 11.
At the same time, it is also supplied from the oxidizer electrode 12 of the adjacent unit fuel cell arranged through the separator IO. Conventionally, the oxidizer type 8i1 of adjacent unit fuel cells
Since the oxidant passage 15 existed between the oxidant electrode 12 of the adjacent unit fuel cell and the reforming catalyst 14,
In the present invention, there is no oxidant passage 15 or TF between the reforming catalyst 14 and the oxidant electrode 12 of the adjacent unit fuel cell, and the heat transfer to the reforming catalyst 14 and the adjacent unit e)
The oxidizer I pole 12 of the i-th fuel cell becomes the closest structure, and the heat of the reforming catalyst 141 can be effectively transferred from the oxidizer electrode 12 of the adjacent unit fuel fE cell. Therefore, it is difficult for the temperature of the reforming catalyst to decrease due to the endothermic effect of the reforming reaction.
This can suppress condensation of electrolyte vapor in the reforming catalyst.

In the present invention, an oxidizer electrode current collector plate may be arranged between the separator 10 and the oxidizer electrode 12, and as shown in FIG. 2, the separator IO has ribs IQ' on both sides.
A structure with . Also, as shown in Figure 3, separator 1
A fuel passage spacer 10a may be disposed facing each other between 0 and the fuel electrode 11, and a reforming catalyst holding mesh 10b may be disposed between them.
It can take the form of Although FIG. 1 shows an example in which the fuel and oxidizer flow in parallel, a structure in which they flow orthogonally may also be used.

[Effects of the Invention] As described above, in the present invention, the heat generated from the oxidizer electrode of the adjacent unit fuel cell is effectively supplied to the reforming catalyst, so that the temperature drop of the reforming catalyst is reduced, and the reforming catalyst is effectively supplied to the reforming catalyst. This makes condensation of electrolyte vapor in the catalyst layer less likely to occur. Therefore, it is possible to reduce the amount of electrolyte attached to the reforming catalyst,
Therefore, it is possible to provide an internally reforming molten carbonate fuel cell with a long life.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of an embodiment of an internal reforming type molten carbonate fuel cell according to the present invention, Figs. FIG. 2 is an explanatory diagram of a molten carbonate fuel cell. 10... Separator 11... Fuel electrode 12... Oxidizer electrode 13... Fuel passage 14... Reforming catalyst 15... ... Oxidizer passage 16 ... Electrolyte matrix Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] 1. A fuel electrode and an oxidizer electrode face each other with an electrolyte matrix in between, and a fuel passage, at least a part of which is filled with a reforming catalyst, is provided on the other surface of the fuel electrode. In a fuel cell configured in multiple layers by stacking unit fuel cells each having an oxidizer passage on the other side, a reforming catalyst faces an oxidizer electrode of an adjacent unit fuel cell via a separator, An internal reforming molten carbonate fuel cell characterized in that there is no oxidant passage between the reforming catalyst and the oxidizer electrode. 2. The internal reforming molten carbonate fuel cell according to claim 1, wherein a current collector plate for the oxidizer electrode is disposed between the separator and the oxidizer electrode.