JPS6318306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cell that generates electric power by electrochemically reacting a fuel and an oxidizing agent, and relates to a fuel cell power generation device that has a simple structure and provides a suitable temperature distribution.

A fuel cell is known as a device that generates electric power by electrochemically reacting a fuel and an oxidizing agent.
The basic configuration of a fuel cell is shown in Figure 1. A cathode (oxidizer electrode) 2 and an anode (fuel electrode) 3 are arranged facing each other with an electrolyte 1 in between, and air containing oxygen is supplied to the surface of the cathode 2 opposite to the electrolyte, while Hydrogen gas, which is a fuel, is supplied to the surface of the anode 3 opposite to the electrolyte.

Both the anode 3 and the cathode 2 are porous bodies made of conductive materials, and there is an interface between the electrolyte and the fuel gas inside them, and the reaction proceeds at this interface.

At the anode 3, hydrogen gas becomes hydrogen ions.
Electrons flow to the cathode 2 through an external load 4,
It combines with hydrogen ions that have passed through the electrolyte and oxygen in the air to form water.

Anode H ₂ →2H ⁺ +2e ^- (1) Cathode 2H ⁺ +1/2O ₂ +2e ^- →H ₂ O (2) H ₂ +1/2O ₂ →H ₂ O (3) In the end, hydrogen in the fuel and oxygen in the air This is a reaction in which water becomes water.

This reaction that progresses inside the fuel cell is an exothermic reaction, and in order to maintain the inside of the cell at a predetermined temperature, it is necessary to constantly remove the reaction heat. Figure 2 shows a molten carbonate electrolyte fuel cell (hereinafter referred to as a molten carbonate electrolyte fuel cell, commonly referred to as a second generation fuel cell) that uses molten carbonate as the electrolyte.
This figure shows the relationship between battery temperature and battery output using a MOF (abbreviated as MOF) as an example. Batteries have a lower temperature limit _T1 , and below this temperature the output drops rapidly due to the physical properties of the electrolyte. Also, the upper limit temperature is determined mainly by the usage limit conditions of battery components.
There are _T2 . Therefore, in order to obtain good performance from the battery, it is necessary to control the battery temperature within a relatively narrow temperature range ΔT. In the case of MOF, ΔT is said to be about 100°C or less at most.

As described above, it is necessary to remove the reaction heat generated within the battery and maintain it within a predetermined temperature range, so various cooling methods have been proposed.

FIG. 3 shows the configuration of a conventional cooling system called the DIGAS cooling system. A group battery (stack) 6 is constructed by stacking unit batteries (cells) 5 each consisting of a cathode, an electrolyte, and an anode. A cooling section 7 is provided within the stack. Air 8 introduced from the outside passes through a heat exchanger 9 and joins the cooled recirculating gas 10, then enters the inlet manifold 12 as an oxidizing gas 11 and is supplied to the cell 5 and the cooler 7. The gas passing through the cell and the cooling section exits to the outlet manifold 13.
After being collected, a portion is recycled through the heat exchanger 9 and the rest is exhausted to the outside as waste gas 14.

The conventional cooling system configured as described above had the following drawbacks.

Figure 4 shows the relationship between the ratio k of the total flow rate of the oxidant gas passing through the cooling section to the total flow rate passing through the cell, and the temperature difference ΔT _CELL in the flow direction of the cell. The inlet temperature is Ti.

In the case of the conventional method shown in FIG. 3, the oxidizing gas 11 is supplied to the cell 5 and the cooling section 7 at the same time, so the cooling section inlet gas temperature Ti is the same as the cell inlet temperature.
As shown in Figure 2, in order to obtain good performance from the battery, the gas temperature Ti at the inlet of the cooling section cannot be lowered much lower than the battery minimum temperature T ₁ , and must be at the same level as T ₁ , for example 600°C. I have no choice but to.

In this case, in order to keep the cell temperature difference ΔT _CELL within a predetermined temperature difference ΔT, for example within 100° C., the cooling section flow rate must be approximately 15 times the cell flow rate, as shown in FIG.

This is a major drawback of conventionally proposed cooling methods. In other words, in order to obtain good performance from the battery, it is necessary to flow approximately 15 times as much oxidant gas into the cooling section as the oxidant flow rate required by the cell, which increases the size of the cooling section and reduces the amount of oxidant gas required for circulation. The capacity of auxiliary equipment such as compressors and heat exchangers was large, making it difficult to put it to practical use.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a fuel cell power generation device that has a simple structure and can provide a suitable temperature distribution.

For this reason, in the present invention, in a fuel cell that generates electric power by electrochemically reacting a fuel and an oxidizer, either one or both of the fuel and the oxidizer is passed through the cooling section of the cell, and then each It is designed to be introduced into the cathode and anode.

The present invention will be explained below based on Examples.

FIG. 5 shows an example of the configuration of a fuel cell power generation device to which the present invention is applied. The oxidant gas 11A is introduced into the cooling section 7A through the cooling gas manifold 15. The gas 16 that has passed through the cooling section is supplied to each cell 5A from the cell inlet manifold 17,
After passing through the cell, it is collected in the outlet gas manifold 18 and exhausted as waste gas 14A.

The fuel cell power generation device configured in this manner exhibits the following effects. That is, as shown in FIG. 5, since the oxidant gas is introduced into the cell 5A after passing through the cooling section 7A, the cooling section inlet temperature Ti
It is not necessary to lower the battery's lower limit temperature T to about ₁ , and it can be lowered to a large extent, for example, to about 400°C. It can be seen that the required flow rate of the oxidant gas in the cooling section at this time may be approximately the same as the cell flow rate, as shown in FIG.

In this way, in the fuel cell power generation device to which the present invention is applied, the cooling section gas flow rate can be made equal to the cell flow rate at about 1/15 of the conventional one, so the cooling section dimensions can be made much wider than in the conventional example. It becomes possible to make it smaller, and it becomes possible to have a significantly simpler configuration, such as eliminating the need for a compressor required for circulation.

Although the above description has taken the case of a molten carbonate electrolyte fuel cell as an example, it goes without saying that the application of the present invention is not limited to this type.

Furthermore, in the above description, the oxidant gas was used as an example of the cooling gas, but the fuel gas may be used as the cooling gas, or both may be used as the cooling gas.

Further, in the above description, an example is given in which a cooling section is provided for every few cells, but the location where the cooling section is provided is not limited.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the principle of a fuel cell, Figure 2 is a diagram showing the relationship between fuel cell output and cell temperature, and Figure 3 is a diagram showing the relationship between fuel cell output and cell temperature.
The figure is a schematic diagram showing an example of a conventional configuration of a fuel cell power generation device, FIG. 4 is a diagram showing the relationship between the ratio of the cooling section flow rate to the cell flow rate and the cell temperature difference, and FIG. 5 is a fuel cell power generation system to which the present invention is applied. It is a schematic diagram showing an example of the configuration of the device. 5,5A...Cell, 7,7A...Cooling part, 6,
6A...Stack, 11,11A...Oxidizer gas.

Claims (1)

[Claims] 1 A group battery in which unit cells consisting of a cathode, an electrolyte, and an anode are stacked, a cooling section provided between the stacked unit cells in the group battery, and either or both of a fuel gas and an oxidizing gas introduced into the cooling section. 1. A fuel cell power generation device comprising: a gas introduction means for supplying gas to the unit cells; and a gas supply means for supplying the gas that has passed through the cooling section to the unit cells.