JPH02253564A - Molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To stabilize flow rate even when pressure is applied to gas to make temperature distribution in a unit cell uniform by installing a partition in the passage of fuel gas or oxidizing gas formed in a separator so as to be capable of its U-shaped turning and by forming both passages in the same direction. CONSTITUTION:Oxidizing gas goes in a passage 12b formed in a cathode side separator 12 from an inlet P1 and goes out through a passage 12c by making U-shaped turn so as to come in contact with a cathode 5b to an outlet P2. Fuel gas goes in a passage 11b formed in an anode side separator 11 from an inlet Q1 and goes out through a passage 12 by making U-shaped turn so as to come in contact with an anode 5a to an outlet Q2. The cross section of the passage is about half that of conventional one and its length is double that of conventional one. Gas flow rate is increased even when pressure is applied to reaction gas and cell output is also increased. By installing parallel flow part in a unit cell, temperature distribution in the plane direction is made small and uniform.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to molten carbonate fuel cells.

(Prior Art) Fuel cells are conventionally known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell usually includes a pair of electrodes, a fuel electrode (hereinafter referred to as anode) and an oxidizer electrode (hereinafter referred to as cathode), with an electrolyte layer in between, and a fuel gas is supplied to the anode. Oxidizing gas is supplied to each cathode, and electrical energy is extracted from between the electrodes by utilizing the electrochemical reaction that occurs at this time.As long as the fuel gas and oxidizing gas are supplied,
Electrical energy can be extracted with high conversion efficiency.

Although there are various types of such fuel cells, molten carbonate fuel cells are expected to be put into practical use next to phosphoric acid fuel cells using an aqueous phosphoric acid solution as an electrolyte. This molten carbonate fuel cell consists of a pair of electrodes, an anode and a cathode, sandwiching an electrolyte layer holding molten carbonate as an electrolyte. In comparison, battery reactions occur more easily, power generation efficiency is higher, and expensive precious metal catalysts are not required.

By the way, in order to construct a high-output power generation plant using such a molten carbonate fuel cell, the fuel cell body is constructed by stacking multiple unit cells in series, and the summed output of each unit cell is I have to try to get it.

FIG. 9 shows an example of the configuration of a conventional molten carbonate fuel cell. That is, each unit battery 3 has a pair of porous electrode plates 5a, 5.
b, an electrolyte layer 2 made of an alkali carbonate interposed therebetween, and a separator 4. Further, the separator 4 is formed with gas passages 6a and 6b for supplying fuel gas or oxidant gas to the picture electrode.

A fuel cell main body 1 is constructed by stacking a plurality of unit cells 3 configured in this manner, and manifolds 8a to 8d having functions of distributing and collecting reactive gases are arranged on four sides of the fuel cell main body 1. While supplying an oxidizing gas from an oxidizing gas population P1 provided in one of the manifolds 8,
Fuel gas is supplied from the fuel gas population Q+ provided in the adjacent manifold, and both reaction gases are electrochemically reacted in the fuel cell main body 1 to obtain a DC output. Oxidizing gas outlet P2
and is configured to be discharged to the outside from a fuel gas outlet Q2. That is, the fuel gas enters the manifold 8a provided with the fuel gas population QI, passes through the gas flow path 6a,
A manifold 8C in which a fuel gas outlet Q2 is provided while the length of one side of the unit cell 3 is in contact with the anode 5a.
is discharged to. On the other hand, the oxidizing gas is oxidizing gas inlet P1
enters the manifold 8d in which the
2 is discharged to the manifold 8b provided with the following.

(Problems to be Solved by the Invention) However, in the conventional molten carbonate fuel cell having the configuration as described above, there were problems to be solved as described below. That is, when flowing fuel gas and oxidant gas at 650° C., which is the operating temperature of a molten carbonate fuel cell, the flow rate when both gases pass through the gas flow paths 6a and 6b is determined by the flow rate and volume. Since the pressures of the fuel gas and oxidant gas are constant, the pressures of the fuel gas and oxidizing gas are smaller when the pressures are pressurized than when they are at normal pressures.

When the flow velocity in the gas flow path decreases in this way, the Reynolds number also decreases, the turbulence of the gas due to the gas flow decreases, and the diffusivity of the reaction gas into the electrode deteriorates. the result,
The drawback was that the battery output decreased.

Therefore, reducing the cross-sectional area of the gas channels 6a and 6b has been considered, but since there is a limit to the processing dimensions, it has not been possible to prevent the gas flow rate from decreasing due to an increase in gas pressure.

Furthermore, since the fuel gas flow path 6a and the oxidant gas flow path 6b are provided perpendicularly to each other, there is a large temperature difference within the unit cell 3, and the reaction conditions are not uniform, resulting in a disadvantage that the cell performance deteriorates. there were.

The present invention was proposed to eliminate the above-mentioned drawbacks, and its purpose is to obtain a stable flow rate even when the reaction gas is pressurized, and to equalize the temperature within the unit cell. The purpose of the present invention is to provide a highly reliable molten carbonate fuel cell that can perform the following steps.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a unit cell comprising a pair of electrodes, a fuel electrode and an oxidizer electrode, sandwiching an electrolyte layer containing a molten carbonate as an electrolyte. A molten carbonate formed by laminating a plurality of layers through separators that constitute part of a reaction gas flow path to constitute a stacked battery, and supplying a fuel gas to the fuel electrode and an oxidizing agent gas to the oxidizing agent electrode. In a type fuel cell, a partition plate is provided in at least one of the fuel gas flow path or the oxidant gas flow path formed in the separator to divide the gas flow path into two, and the reactant gas flowing inside the partition plate can make a U-turn. The present invention is characterized in that the fuel gas flow path and the oxidant gas flow path are formed in the same direction.

(Function) According to the molten carbonate fuel cell of the present invention, a partition plate is disposed in at least one of the fuel gas flow path and the oxidant gas flow path formed in the separator to divide the gas flow path into two. Therefore, the cross-sectional area of the gas flow path is about half that of the conventional one, and the flow rate of the reaction gas flowing inside can be increased.

Furthermore, by forming the fuel gas flow path and the oxidant gas flow path in the same direction, the flow of the fuel gas and the oxidant gas in both gas flow paths can be made into parallel flows or counterflows,
The temperature within the unit battery can be made uniform.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIG. Note that the same members as those of the conventional type shown in FIG. 9 are given the same reference numerals, and explanations thereof will be omitted.

In this embodiment, as shown in FIG.
An anode 5a and a cathode 5b, which are a pair of porous electrodes, are arranged on both sides of the electrode, and an anode-side separator 11 and a cathode-side separator 12, each of which has a gas flow path for supplying a reaction gas to the picture electrode, are placed between each electrode. 5a and 5b. Also, these separators 11.1
2, each has a partition plate 11a* in the center thereof.
128 is provided, and this partition plate 11 a + 1
Two gas flow paths 11b and lie with 2 B in between, respectively.
and 12b, 12c are formed. Note that the gas channels 11b and 11c formed in the anode side separator 11
and a gas flow path 1 formed in the cathode side separator 12.
2b and 12c are arranged parallel to each other. In addition, in this embodiment, the fuel gas inlet portion Q1
and the oxidizing gas inlet portion P1 are provided on opposite sides, and the directions of gas flows in the opposing gas flow paths are the same.

In the molten carbonate fuel cell of this embodiment having such a configuration, the oxidant gas inlet P! The oxidant gas supplied from the cathode side separator 12 passes through one gas flow path 12b formed in the cathode side separator 12, comes out to the opposite side while contacting the cathode 5b, makes a U-turn there, and passes through the other gas flow path 12c.
The oxygen-containing gas is discharged through the oxygen-containing gas outlet P2. on the other hand,
The fuel gas supplied from the fuel gas population Q1 passes through one gas flow path 11b formed in the anode-side separator 11, comes out to the other side while contacting the anode 5a, makes a U-turn there, and enters the other gas flow. The oxidizing gas is discharged through the passage 11C to the oxidant gas outlet Q2.

In this way, the gas flow path is connected to the partition plate 11a*12
Since it is partitioned by a, the cross-sectional area of the gas flow path is about half of the conventional one, and the length is about twice as long as it is U-turned.
The gas flow rate is higher than before.

As a result, the diffusion of the reaction gas into the electrode is improved,
Battery output also increases.

Furthermore, since the gas flow paths 11b and llc formed in the anode side separator 11 and the gas flow paths 12b and 12c formed in the cathode side separator 12 are formed parallel to each other, each reaction gas They become parallel flows with the same flow direction. Such parallel flow can reduce the temperature difference distribution in the planar direction within the unit cell, compared to the conventional cross flow.

In this way, according to this embodiment, by making a U-turn in the fuel gas and oxidant gas, the gas flow rate can be increased, so the cell output can be increased and the performance of the fuel cell can be improved. I can do it. Further, by providing a parallel flow section within the unit battery, it is possible to equalize the temperature within the unit battery.

Note that the present invention is not limited to the above-mentioned embodiment, and as shown in FIG. The direction of gas flow within the gas flow path is configured to be the same. Further, as shown in FIGS. 3 and 4, the fuel gas and the oxidizing gas may be configured to flow in opposite directions.

Furthermore, as shown in Figures 5 to 8, only one of the fuel gas or the oxidizing gas is made to make a U-turn, while the other is made to go straight, so that the fuel gas and the oxidizing gas flow in parallel or in opposite directions. It may be configured as follows. When the reaction gas is made to flow in one direction in this manner, it is not necessarily necessary to provide a partition plate in the gas flow path. Furthermore, in any of the cases shown in FIGS. 2 to 8, it is possible to increase the flow rate of the oxidizing gas and the fuel gas and to reduce the temperature difference within the unit cell.

[Effects of the Invention] As described above, according to the present invention, a partition plate is disposed in at least one of the fuel gas flow path and the oxidant gas flow path formed in the separator to divide the gas flow path into two. However, when the reaction gas is pressurized by a simple means of configuring the reaction gas flowing therein to make a U-turn, and forming the fuel gas flow path and the oxidant gas flow path in the same direction. It is possible to provide a highly reliable molten carbonate fuel cell that can obtain a stable flow rate even in the case of a unit cell, and also can equalize the temperature within the unit cell.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of a unit cell constituting a molten carbonate fuel cell of the present invention, FIGS. 2 to 8 are perspective views showing other embodiments of the present invention, and FIG. 9 FIG. 1 is a perspective view showing an example of a unit cell constituting a conventional molten carbonate fuel cell. DESCRIPTION OF SYMBOLS 1... Fuel cell main body, 2... Electrolyte layer, 3... Unit cell, 4... Separator, 5a... Anode, 5
b...Cathode, 5a, 5b...Gas flow path, 8...
・Manifold, 11...Anode side separator, l
la... partition plate, llb, llc... gas flow path,
12... Cathode side separator, 12a... Partition plate, 12b, 12C... Gas flow path.

Claims (1)

[Scope of Claims] A unit cell comprising a pair of electrodes, a fuel electrode and an oxidizer electrode, sandwiching an electrolyte layer containing molten carbonate as an electrolyte, is provided by a separator that forms part of a reaction gas flow path. In a molten carbonate fuel cell, in which a plurality of layers are stacked together to form a stacked battery, a fuel gas is supplied to the fuel electrode, and an oxidant gas is supplied to the oxidizer electrode, the fuel formed on the separator is A partition plate is disposed in at least one of the gas flow path or the oxidizing gas flow path to divide the gas flow path into two, and the reactant gas flowing inside the partition plate is configured to make a U-turn. A molten carbonate fuel cell characterized in that a channel and an oxidant gas flow channel are formed in the same direction.