JPH01246767A - Fuel cell - Google Patents

Abstract

PURPOSE:To provide uniform temp. distribution of a stack and enhance the output characteristic by forming refrigerant passages for a cooling plate in such a construction as intruding through one edge of a four edge polygon and exhausting through the other three edges. CONSTITUTION:The refrigerant intruding a cooling plate 11 for fuel cell stack in the direction shown by the arrow is exhausted in three directions along refrigerant passages furnished radially. Thereby the refrigerant after passing the refrigerant passages to get high temp through heat exchange passes the three edges and raises the temp. of the ends. This decreases the difference between the center of the temp. distribution in the stack and the end part to lead to enhancement of the output characteristic.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel cell that generates electricity using hydrogen-rich reformed gas obtained by reforming hydrocarbon raw materials such as natural gas and methanol; Especially regarding its cooling structure.

[Conventional technology]

As is well known, a fuel cell consists of a stack consisting of a large number of single cells stacked together, each consisting of an electrolyte layer and a pair of electrodes, a fuel electrode and an air electrode, facing each other with the electrolyte layer in between. This is a battery that generates electricity through an electrochemical reaction by supplying the above-mentioned hydrogen-rich reformed gas to the fuel electrode side and supplying air or oxygen as an oxidizing agent to the air electrode side.

By the way, the higher the operating temperature of this type of fuel cell, the higher the
Although high output characteristics can be obtained, on the other hand, the operating temperature cannot be made too high due to the corrosion resistance of the battery components, including the fuel cell itself.Generally, the operating temperature is limited to 200℃ or less. In order to enable practical power generation within this operating temperature range, noble metals such as platinum are usually added to the electrodes to promote electrochemical reactions at the fuel and air electrodes. A catalyst is added.

Hydrogen, the fuel for phosphoric acid fuel cells, is usually produced by reforming hydrocarbon-based raw materials such as natural gas or alcohol-based raw materials such as methanol. The hydrogen-rich reformed gas obtained by this reforming is composed of hydrogen, carbon dioxide, and other trace components, including carbon monoxide as the trace component, which is toxic and reduces the activity of the electrode catalyst. (poisoning effect on catalyst). This poisoning effect is the first
As shown in the graph of Figure 0, this effect becomes particularly strong when the temperature of the fuel cell is low or when the concentration of -carbon oxide is high.

Therefore, given the upper limit of 200°C, it is desirable to keep the battery temperature as high as possible.
'On the other hand, since fuel cells generate heat due to electrochemical reactions during operation, forced cooling is required to remove the generated heat from the system in order to keep the battery below the above-mentioned operating temperature. In this case, one cooling method is to supply excess air as a reaction gas and exhaust the heat generated inside the battery to the outside of the system together with the excess air. The disadvantage is that the amount of escape is large. For this purpose, a cooling passage is formed to exclusively supply a cooling medium such as water or air to a cooling plate or a separate plate arranged in the stack independently of the reaction gas passage.
A water-cooling method or an air-cooling method is often used in which a cooling medium is introduced from one open end of the cooling passage and discharged from the other open end to cool the fuel cell.

FIG. 7 is a sectional view illustrating a conventional example in which cooling plates 7 are arranged for each of a plurality of single cells l in a stack. The unit cell 1 includes a matrix la, a fuel electrode 1b, an air electrode 1c,
It is composed of a ribbed separator 2 for the fuel electrode and a ribbed separator 4 for the air electrode. Separator with lip for fuel electrode 2
A fuel gas passage 3 is provided in the fuel electrode 1, and the fuel gas is supplied to the fuel electrode 1.
b. Similarly, an air passage 5 is provided in the ribbed separator 4 for the air electrode, and air is supplied as an oxidizing gas to the air electrode 1c, thereby generating electricity within the unit cell.

FIG. 8 is a perspective view showing a conventional cooling plate 7, in which the cooling medium passage 6 is provided in a straight line from one side of a quadrilateral to the opposite side,
The cooling medium passes linearly through the cooling plate 7 from one inlet to the other outlet.

[Problem to be solved by the invention]

However, the conventional fuel cell having a cooling plate as described above has the following problems.

The low-temperature cooling medium supplied from the medium passage entrance absorbs heat from the stack, and its temperature gradually increases. As a result, as shown in the in-plane temperature distribution diagram of the cooling plate in Fig. 9, the temperature in the area near the cooling medium inlet side along the flow direction of the cooling medium is low;
On the contrary, the temperature distribution shows a temperature distribution where the temperature is higher in the area near the exit side.
It shows the temperature distribution of each part when cooling is kept within 00°C.

The temperature distribution of the cooling plate 7 in the direction perpendicular to the cooling medium passage 6 is as follows.
As shown in the figure, the temperature is lower at both ends than in the center. This is because there are fuel supply manifolds on both ends, which absorb heat from the stack, and furthermore, there is a large amount of heat radiated from the manifolds to the outside. In order to prevent the temperature at both ends from dropping, conventional methods include l) covering the sides of the manifold with an insulating material;
) Countermeasures have been taken, such as blocking the passages at both ends of the cooling plate 7 in a direction perpendicular to the cooling medium passage 6 to prevent passage of the cooling medium. However, countermeasure 1) requires a large amount of insulation material, which increases the external dimensions of the fuel cell stack, and 2)
The disadvantage of this measure is that it is difficult to control the temperature when the amount of heat generated by the fuel cell changes.

In addition, when starting a fuel cell from a cold state, for example around 40°C, it is necessary to heat the stack to around 140°C in order to reduce the aforementioned poisoning effect of carbon monoxide on the catalyst. The heat medium is passed through the cooling medium passage 6.
This can be achieved by supplying The temperature distribution of the fuel cell stack at this time is also high at the center and low at both ends.
The problem with conventional cooling plates placed in fuel cell stacks, which shows the same tendency as during operation, is that the in-plane temperature distribution is lower at the ends than at the center. was there.

In view of this point, the present invention changes the structure of the cooling medium passage of the cooling plate to improve the temperature distribution of the fuel cell stack so that the difference between the center and the ends does not become large, and the temperature distribution is The purpose of the present invention is to suppress the poisoning effect of carbon oxide on an electrode catalyst as low as possible, thereby maintaining high output characteristics of a fuel cell.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a plurality of unit cells each having a reaction gas passage for supplying fuel reforming gas and oxidizer air are stacked and stacked. In a fuel cell in which a cooling plate is arranged, the cooling plate is provided with a cooling medium passage that exclusively flows a cooling medium to the stack, and the cooling plate supplies the cooling medium from one of its four sides. , the cooling medium is discharged from the other three sides via cooling medium passages formed in the cooling plate.

[Effect]

According to the configuration of the present invention, the structure of the cooling medium passage of the cooling plate used in the fuel cell stack is formed so that the cooling medium enters from the entrance on one side of the quadrilateral and is discharged from the other three sides. Therefore, the cooling medium that has become high in temperature due to heat exchange at the center of the stack exits in three directions, which prevents the temperature at the ends from lowering compared to the center.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a perspective view of a cooling plate 11 for a fuel cell stack showing an embodiment of the present invention, in which cooling medium enters from the direction of the arrow and is discharged from three directions along cooling medium passages provided radially. It has become so.

FIG. 2 is a perspective view of a cooling plate 12 showing a different embodiment of the present invention.
The cooling medium enters from the direction of the arrow and is discharged from three directions, one straight and one left and right.

FIG. 3 shows a cooling plate 1 showing a further different embodiment of the present invention.
In the perspective view of 3, the cooling medium enters from the direction of the arrow and goes straight, and after being sufficiently heated, it separates into the front, right, and left, so it separates into the right and left. The cooling medium used to prevent the temperature of the cooling plate at the end from decreasing.

Figure 4 shows the in-plane temperature distribution of the cooling plates 11 and 12. The cooling medium, which has become high in temperature due to heat exchange through the cooling medium passage, passes through the edges of the three sides, so the temperature at the edges is lower than in the past. Indicates a raised state.

FIG. 5 shows the in-plane temperature distribution of the cooling plate 13, and shows a state in which the temperature at the ends has further increased because the cooling medium flows to the ends after passing through the central high temperature section.

FIG. 6 is a perspective view showing an assembled cross section of a fuel cell stack incorporating the cooling plate 11 according to the present invention, and even if cooling plate 11 is replaced with 12 or 13, the same structure can be obtained. can.

The fuel reformed gas enters the fuel reformed gas inlet manifold 8a, which is divided at the location where the cooling plate 11 is arranged, from the inlet header 10a, passes through each unit cell 1 in the stack, and passes through the fuel reformed gas outlet. It is discharged into the manifold 8b and guided to the outside by the outlet header 10b.

The oxidant gas and the air that serves as the cooling medium are shared by a common manifold 9.
A is supplied to each cell 1 and cooling plate 11 in the stack, but the air that becomes the oxidizing gas passes through each car battery in the stack and undergoes an electrochemical reaction with the reformed fuel gas in each cell. After generating electricity, it is collected in the oxidant gas discharge manifold 9b. On the other hand, the air that has entered the cooling plate passes through the cooling plate passages as a cooling medium, exchanges heat, and is discharged in three directions. At this time, as mentioned above, by disposing the cooling plates 11, 12 or 13 according to the embodiment of the present invention, the temperature difference between the center part of the cooling plate and the outer edge part does not become large, and furthermore, the temperature difference in the surface direction of the fuel cell stack is It is possible to reduce the height difference in temperature distribution.

〔Effect of the invention〕

According to this invention, a cooling passage is formed in a cooling plate provided in a fuel cell stack so that a cooling medium is supplied from one side of the cooling plate and discharged from the remaining three sides, thereby improving the temperature distribution inside the stack. This results in a decrease in the low surface area, which reduces the possibility of poisoning of the electrode catalyst by carbon monoxide contained in the reformed fuel gas in fuel cells that use forced cooling to keep the operating temperature of the fuel cell at about 200°C. It is possible to improve the output characteristics of the fuel cell while keeping the influence low.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a cooling plate disposed in a fuel cell stack for explaining the present invention in detail, and FIG. 2 is a perspective view of the same cooling plate for explaining different embodiments of the present invention. FIG. 3 is a perspective view of the same cooling plate for explaining still another embodiment of the present invention, and FIG.
Figure 5 is an in-plane temperature distribution diagram when the cooling plate explained in Figure 3 is placed in the stack. Figure 6 is an in-plane temperature distribution diagram when the cooling plate explained in Figure 3 is placed in the stack. A perspective view showing an assembled cross section of a fuel cell stack incorporating a cooling plate according to the present invention, and FIG. 7 is a sectional view illustrating the placement of a conventional cooling plate 7 in a fuel cell stack. , Fig. 8 is a perspective view showing a conventional cooling plate, Fig. 9 is an in-plane temperature distribution diagram of the conventional cooling plate shown in Fig. 8, and Fig. 10 shows carbon monoxide poisoning the electrode catalyst of a fuel cell. FIG. 1°·° single cell, 8a... manifold for fuel reformed gas inlet, 8b... manifold for fuel reformed gas outlet,
9a... Common manifold, 9b... Oxidizing gas discharge manifold, loa... Inlet header, 10
b...Exit header, 7, IL 12.13.
...Cooling plate. 152 Kido No. 3 Seki No. 4 Figure? Kugikuzu 5 Mouth No. 6 Illustration Furnace 758 Illustration Ai 1 Beating Body ￥39 Illustration New Battery 5th Stitch → L10 Diagram

Claims (1)

[Claims] 1) A stack is formed by stacking a plurality of single cells each having a reaction gas passage for supplying fuel reforming gas and oxidizer air, and a cooling medium passage is provided to exclusively flow a cooling medium to the stack. In a fuel cell equipped with a cooling plate, the cooling plate supplies a cooling medium from one of its four sides, and supplies the cooling medium from the other three sides through a cooling medium passage formed in the cooling plate. A fuel cell configured to emit.