JPH08306381A - Lamination type fuel cell - Google Patents

Abstract

PURPOSE: To use a lamination type fuel cell which can be safely used for a long period by preventing damage generated by lack of hydrogen inside a unit cell. CONSTITUTION: A flow regulation means 21 is provided on a fuel gas supply manifold 16 installed on a side surface of a fuel cell lamination body 12 in which unit cells are laminated, and the flow of fuel gas is adjusted in such a way that flow through the closer side to an oxidizer gas discharge manifold 16 is larger than flow through the closer side to an oxidizer gas supply manifold 15. Lack of hydrogen generated at a place upstream of oxidizer gas and downstream of fuel gas is eliminated, thereby damaging can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacked fuel cell in which unit cells are stacked and a reaction gas is flowed from the side surface to generate electric power by an electrochemical reaction. Regarding the structure.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view showing the basic structure of a fuel cell stack conventionally used in this type of stacked fuel cell. The unit cell 8 is configured by sandwiching a matrix 1 holding an electrolyte between a fuel electrode 2 and an oxidant electrode 5. The fuel electrode 2 is provided with a fuel catalyst layer 3 on a surface of a gas permeable electrode base material made of porous carbon, which faces the matrix 1, and a fuel for flowing a fuel gas, which is one of reaction gases, on the opposite surface. The gas flow groove 4 is provided. Similarly, the oxidant electrode 5 is provided with an oxidant catalyst layer 6 on a surface of the electrode base material facing the matrix 1, and an oxidant gas flow groove for flowing an oxidant gas which is another reaction gas on the opposite surface. Equipped with 7. When the unit cell 8 is formed, the unit cells 8 are stacked such that the flow direction of the fuel gas flow groove 4 and the flow direction of the oxidant gas flow groove 7 are orthogonal to each other. The fuel cell stack is formed by inserting the separator 9 into a plurality of layers of the single cells 8 configured in this way, and stacking them with the cooling plate 10 interposed therebetween. The cooling plate 10 plays a role of removing the heat generated by power generation and adjusting the operating temperature by flowing the refrigerant through the buried refrigerant flow pipe 11.

FIG. 7 is a vertical cross-sectional view schematically showing the basic structure of a conventional laminated fuel cell using the above fuel cell laminated body. This figure is a cross-sectional view as seen from the oxidant gas flow side, and one side of the fuel cell stack 12 formed by stacking the unit cells 8 and the cooling plate 10 on the fuel gas flow side has the fuel gas. A supply manifold 13 and a fuel gas discharge manifold 14 are incorporated in the other side, and an oxidant gas supply manifold and an oxidant (not shown) are provided on a side surface of the oxidant gas flow side perpendicular to the plane of the drawing. A laminated fuel cell is constructed by incorporating a gas exhaust manifold.
The fuel gas supplied from the fuel gas inlet 17 is dispersed inside the fuel gas supply manifold 13 and flows through the fuel gas flow groove of each of the stacked unit cells 8 and then to the fuel gas discharge manifold 14. Collected and discharged from the fuel gas outlet 18. Similarly, the oxidant gas is dispersed inside the oxidant gas supply manifold and flows in the oxidant gas flow groove of the single cell 8 in a direction orthogonal to the fuel gas, so that the oxidant gas is discharged from the oxidant gas discharge manifold. It is discharged from the gas outlet to the outside.

[0004]

In the stacked fuel cell having the above-mentioned structure, hydrogen in the fuel gas flowing through the fuel gas flow groove and hydrogen in the oxidant gas flowing through the oxidant gas flow groove are formed. Oxygen contributes to the electrochemical reaction of the single cell to generate direct current power, and hydrogen and oxygen are consumed. Normally, hydrogen in fuel gas is used at a high utilization rate of about 80%, so the hydrogen concentration in the fuel gas at the outlet side of the fuel gas of a single cell is significantly lower than that at the inlet side. Similarly, the oxygen concentration in the oxidant gas also greatly differs between the inlet side and the outlet side of the oxidant gas.

FIG. 8 shows the distribution of the hydrogen concentration in the fuel gas in the plane of the single cell. The hydrogen concentration in the plane is displayed by setting the hydrogen concentration at the inlet (the right end face in the figure) to 10. ing. Further, FIG. 9 shows the distribution of oxygen concentration in the oxidant gas in the plane of the single cell, where the oxygen concentration at the inlet (upper end face in the figure) is set to 10 and the hydrogen concentration in the plane is displayed. It is a thing. In both figures, the concentration distribution of hydrogen or oxygen, assuming that the current density generated by a single cell is uniform in the plane, is shown by the dotted line, and the concentration distribution under conventional actual operating conditions is shown by the solid line. are doing.

If the current density is uniform in the plane, the consumption of hydrogen or oxygen is also uniform in the plane, so that the concentration of hydrogen or oxygen decreases linearly with distance as shown by the dotted lines in FIGS. Will be done. However, in practice,
A reaction occurs depending on the concentrations of hydrogen and oxygen to generate a current density distribution, and hydrogen and oxygen are consumed. Therefore, the amount consumed in the upstream side of the fuel gas and the upstream side of the oxidant gas is Will increase. That is, the amount of consumption is highest in the portion near the fuel gas inlet and the oxidant gas inlet, and is the smallest in the portion near the fuel gas outlet and the oxidant gas outlet. Since the hydrogen concentration in the fuel gas is high in the near part, a large amount of oxygen in the oxidant gas is also consumed, and the oxygen concentration in the oxidant gas is high in the part near the fuel gas outlet and the oxidant gas inlet. Since a large amount of hydrogen is also consumed, it has a concentration distribution as shown by the solid lines in FIGS.

As described above, in the conventional laminated fuel cell,
Since the hydrogen concentration becomes relatively low compared to the oxygen concentration in the portions near the fuel gas outlet and the oxidant gas inlet of the single cell, it is easy to change depending on, for example, a sudden load increase or a change in the fuel gas supply amount. In addition, there is a danger that the fuel electrode will be deficient in hydrogen, and the permeation of excess oxygen will corrode and damage the fuel electrode, resulting in the inability to generate electricity.

Further, normally, the main component of the fuel gas is hydrogen which contributes to the electrochemical reaction with carbon dioxide, but since hydrogen is extremely lighter than carbon dioxide, as shown in FIG. When the supplied fuel gas is split in the fuel gas supply manifold 13, the hydrogen concentration of the fuel gas flowing to the upper unit cell 8 becomes higher, and the hydrogen concentration of the fuel gas flowing to the lower unit cell 8 becomes lower. Become. On the other hand, in air usually used as an oxidant gas, the specific gravity of oxygen that contributes to the electrochemical reaction is almost the same as the specific gravity of nitrogen, which is the main constituent element, and the concentration change does not occur in the upper part and the lower part. Absent. Therefore, in the unit cell below the fuel cell stack, the hydrogen concentration is relatively low and the hydrogen is deficient, and there is a risk that the fuel electrode is likely to be corroded or damaged.

The present invention has been made in consideration of such problems, and an object thereof is to prevent the occurrence of damage due to lack of hydrogen inside a single cell and to provide a laminated fuel cell which can be safely used for a long period of time. To provide.

[0010]

In order to achieve the above-mentioned object, in the present invention, every time a plurality of single cells are laminated, a matrix holding an electrolyte is sandwiched between an oxidant electrode and a fuel electrode. A fuel cell stack formed by inserting cooling plates and stacking them in a substantially vertical direction, a manifold for supplying an oxidant gas, a manifold for discharging an oxidant gas, and a manifold for supplying a fuel gas, which are arranged on the side surfaces thereof. In a laminated fuel cell including a fuel gas discharge manifold, at least one of the four manifolds described above is provided with a flow rate adjusting unit for adjusting a gas flow rate distribution.

Further, the above-mentioned flow rate adjusting means is attached to at least one of the manifold for supplying the fuel gas and the manifold for discharging the fuel gas, and the oxidizing gas is supplied from a side surface adjacent to the manifold for supplying the oxidizing gas. It is formed so that the flow path resistance increases continuously or intermittently in the horizontal direction toward the side surface close to the discharge manifold.

Furthermore, the above-mentioned flow rate adjusting means is attached to at least one of the manifold for fuel gas supply and the manifold for fuel gas discharge, and continuously from the lower part to the upper part in the vertical direction. Alternatively, the flow path resistance is intermittently increased.

[0013]

As described above, if at least any one of the four manifolds arranged on the side surface of the fuel cell stack is provided with the flow rate adjusting means for adjusting the gas flow rate distribution, hydrogen is provided. It is possible to adjust the flow rate distribution so that a large amount of fuel gas is supplied to the parts with high hydrogen consumption and low hydrogen concentration, and a small amount of fuel gas is supplied to the parts with high hydrogen concentration and low hydrogen consumption. It is possible to supply a large amount of oxidant gas to the part that consumes a large amount of hydrogen or a high hydrogen concentration, and to supply a small amount of oxidant gas to a part that has a low hydrogen concentration or a small amount of hydrogen consumption. Since the flow rate distribution can be adjusted, it is possible to avoid the occurrence of a hydrogen deficient portion inside the single cell.

In particular, the above-mentioned flow rate adjusting means is attached to at least one of the manifold for supplying the fuel gas and the manifold for discharging the fuel gas, and the oxidizing gas is supplied from the side surface close to the manifold for supplying the oxidizing gas. The flow rate of the fuel gas is inversely proportional to the flow path resistance if the flow path resistance is formed to increase continuously or intermittently in the horizontal direction toward the side surface close to the exhaust manifold. Thus, the amount increases in the horizontal direction from the side surface adjacent to the oxidant gas discharge manifold to the side surface adjacent to the oxidant gas supply manifold. Therefore, a large amount of fuel gas is supplied to a portion that consumes a large amount of hydrogen or a portion that has a low hydrogen concentration, and a large amount of hydrogen is supplied. It will be avoided.

Furthermore, the above-mentioned flow rate adjusting means is attached to at least one of the manifold for supplying the fuel gas and the manifold for discharging the fuel gas, and as the vertical direction goes from the lower part to the upper part, it is continuously connected. If it is formed such that the flow path resistance increases intermittently or intermittently, the flow rate of the fuel gas increases as the flow rate decreases from the upper portion to the lower portion. Therefore, the flow rate of the fuel gas in the lower part where the hydrogen concentration has decreased due to the difference in specific gravity increases, and it is possible to avoid a decrease in the hydrogen supply amount.Therefore, there is a shortage of hydrogen in the lower unit cell, which has been a problem with conventional equipment. Will be avoided.

[0016]

1 is a cross-sectional view of a first embodiment of a laminated fuel cell of the present invention. A fuel supply manifold 13 having a fuel gas inlet 17 and a fuel gas outlet 18 on one of opposite sides of a rectangular fuel cell stack 12 formed by stacking unit cells and cooling plates. An exhaust gas manifold 14 is incorporated, and an oxidant gas supply manifold 15 having an oxidant gas inlet 19 and an oxidant gas exhaust manifold 16 having an oxidant gas outlet 20 are provided on the other opposite side surfaces. Incorporated, the fuel gas and the oxidant gas flow through the fuel cell stack 12 at right angles to each other. Among them, inside the fuel supply manifold 13, as schematically shown in the figure, there is provided a flow rate adjusting means 21 formed by arranging dispersed flow path resistors having triangular cross sections having different sizes. ing. The flow rate adjusting means 21 is configured so that the fluid resistance increases from left to right in the figure, that is, from the side close to the oxidant gas supply manifold 15 to the side close to the oxidant gas discharge manifold 16. Therefore, the fuel gas supplied from the fuel gas inlet 17 flows in a larger amount on the side closer to the oxidant gas supply manifold 15 than on the side closer to the oxidant gas discharge manifold 16.

FIG. 2 shows the flow of the fuel gas in the fuel supply manifold 13 of the laminated fuel cell of the first embodiment. (A) shows the change in the flow before and after the flow rate adjusting means 21. FIG. 3B is a schematic diagram showing a flow rate distribution diagram of FIG. The flow rate of the fuel gas supplied from the fuel gas inlet 17 varies depending on the flow path adjusting plate 21 having five types of triangular cross-section flow path resistors having different sizes, and at the inlet portion of the fuel cell stack ( It will have a flow rate distribution as in b).

FIG. 3 shows the hydrogen concentration distribution in the single cell plane during power generation operation in the laminated fuel cell of the first embodiment. Also in this figure, the hydrogen concentration at the inlet (the right end surface in the figure) is displayed as 10 as in FIG. As described with reference to FIG. 8, hydrogen is consumed more toward the oxidant gas inlet side (upper end in the figure) where the oxygen concentration is higher. However, in the stacked fuel cell of this configuration, as described above, the oxidant gas outlet is A large amount of fuel gas is supplied to the side closer to the oxidant gas inlet than to the side closer to, and the amount of supplied hydrogen is larger toward the side closer to the oxidant gas inlet, so the decrease in hydrogen concentration is alleviated, The hydrogen concentration distribution is even compared to the conventional example,
The occurrence of hydrogen deficiency in the portion near the fuel gas outlet and the oxidant gas inlet will be avoided. If the flow rate distribution of the fuel gas is configured as in this configuration, the hydrogen concentration on the side close to the oxidant gas outlet will decrease, but FIG. 4 shows the oxygen concentration distribution in the unit cell plane. As described above, since the oxygen concentration in the oxidant gas is decreasing on the oxidant gas outlet side,
There is no fear of hydrogen shortage.

FIG. 5 is a longitudinal sectional view of a second embodiment of the laminated fuel cell of the present invention. In this embodiment, the fuel gas supply manifold 13 provided on one of the side surfaces of the fuel cell stack 12 is provided with the flow rate adjusting means 21A configured so that the flow path resistance increases from the lower portion to the upper portion. It is characterized by being. Therefore, in this configuration,
A large amount of the fuel gas supplied from the fuel gas inlet 17 flows to the unit cells arranged on the lower side of the fuel cell stack 12, and a small amount flows to the unit cells arranged on the upper side. As described above, the specific gravity of hydrogen in the fuel gas is relatively small, so the fuel gas flowing in the upper part has a higher hydrogen concentration and the fuel gas flowing in the lower part has a lower hydrogen concentration, but the flow rate is adjusted as in this configuration. In this case, the hydrogen flow rate is prevented from decreasing even in the lower part, so that it is possible to avoid troubles caused by the hydrogen shortage.

In each of the above-described embodiments, the flow rate adjusting means is incorporated in the fuel gas supply manifold 13 to adjust the flow rate, but the flow rate is similarly adjusted by incorporating it in the fuel gas discharge manifold 14. , Hydrogen shortage is avoided. Further, the fuel gas supply manifold 1
3 or instead of being incorporated in the fuel gas discharge manifold 14 to adjust the flow rate of the fuel gas, flow rate adjusting means is incorporated in the oxidant gas supply manifold 15 or the oxidant gas discharge manifold 16 to adjust the flow rate of the oxidant gas. However, even if a large amount of oxidant gas is supplied to a portion of the fuel gas having a high hydrogen concentration and a small amount of oxidant gas is supplied to a portion of the fuel gas having a low hydrogen concentration, occurrence of a hydrogen deficient portion is avoided.

[0021]

As described above, according to the present invention, a fuel cell stack formed by inserting a cooling plate every time a plurality of single cells are stacked and stacking them in a substantially vertical direction, and a side surface thereof At least one of the above four manifolds in a stacked fuel cell provided with an oxidant gas supply manifold, an oxidant gas discharge manifold, a fuel gas supply manifold, and a fuel gas discharge manifold that are arranged. One of the manifolds will be equipped with a flow rate adjusting means for adjusting the gas flow rate distribution, especially in the horizontal direction from the side surface close to the oxidant gas supply manifold to the side surface close to the oxidant gas discharge manifold. The flow rate adjusting means formed so that the flow path resistance increases continuously or intermittently as Since it will be attached to at least one of the gas exhaust manifolds, damage due to hydrogen deficiency in the plane of the single cell can be avoided, and a laminated fuel cell that can be used safely for a long time can be obtained. Became.

Furthermore, a flow rate adjusting means formed so that the flow path resistance increases continuously or intermittently from the lower part to the upper part in the vertical direction is provided with a manifold for fuel gas supply and a fuel gas discharge. If it is attached to at least one of the manifolds, it is possible to avoid damage due to the occurrence of hydrogen deficiency due to fluctuations in hydrogen concentration in the fuel gas due to the difference in specific gravity, and it is possible to use it safely for a long time. Will be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a laminated fuel cell of the present invention.

FIG. 2 is a characteristic diagram of the flow of fuel gas in the fuel supply manifold 13 of the stacked fuel cell of the first embodiment,
(A) is a schematic diagram of the flow before and after the flow rate adjusting plate 21, (b)
Is the flow distribution map after passing through the flow adjustment plate 21

FIG. 3 is a hydrogen concentration distribution map within a single cell plane of the stacked fuel cell according to the first embodiment.

FIG. 4 is an oxygen concentration distribution in a single cell plane of the stacked fuel cell of the first embodiment.

FIG. 5 is a longitudinal sectional view of a second embodiment of the stacked fuel cell of the present invention.

FIG. 6 is a perspective view showing the basic structure of a fuel cell stack of this type of stacked fuel cell.

FIG. 7 is a vertical cross-sectional view schematically showing the basic structure of a conventional stacked fuel cell.

FIG. 8 is a hydrogen concentration distribution map in a single cell plane of a conventional stacked fuel cell.

FIG. 9: Oxygen concentration distribution in a single cell plane of a conventional stacked fuel cell

[Explanation of symbols]

 8 Single Cell 10 Cooling Plate 12 Fuel Cell Stack 13 Fuel Gas Supply Manifold 14 Fuel Gas Discharge Manifold 15 Oxidant Gas Supply Manifold 16 Oxidant Gas Discharge Manifold 17 Fuel Gas Inlet 18 Fuel Gas Outlet 19 Oxidant Gas Inlet 20 oxidant gas outlet 21 flow rate adjusting means 21A flow rate adjusting means

Claims (3)

[Claims] 1. A fuel cell which is formed by inserting a cooling plate every time a plurality of single cells, in which a matrix holding an electrolyte is sandwiched between an oxidant electrode and a fuel electrode, is stacked and stacked in a substantially vertical direction. In a laminated fuel cell including a laminated body and an oxidant gas supply manifold, a oxidant gas discharge manifold, a fuel gas supply manifold, and a fuel gas discharge manifold arranged on the side surface thereof,
A laminated fuel cell, wherein at least one of the four manifolds has a flow rate adjusting means for adjusting a gas flow rate distribution. 2. The flow rate adjusting means is attached to at least one of a manifold for supplying fuel gas and a manifold for discharging fuel gas, and the oxidizing gas is supplied from a side surface adjacent to the manifold for supplying oxidizing gas. The laminated fuel cell according to claim 1, wherein the laminated fuel cell is formed so that the flow path resistance increases continuously or intermittently in the horizontal direction toward the side surface close to the discharge manifold. 3. The flow rate adjusting means is attached to at least one of a manifold for supplying a fuel gas and a manifold for discharging a fuel gas, and continuously or vertically as it goes from the lower part to the upper part. The laminated fuel cell according to claim 1 or 2, wherein the laminated fuel cell is formed so that the flow path resistance increases intermittently.