KR20050006651A - Molten carbonate fuel cell with simplified central distribution separator - Google Patents

Abstract

PURPOSE: A molten carbonate salt fuel cell is provided, to inhibit the generation of a high temperature part by reducing the pressure generated by the flow of gas by shortening the length of channel of an oxidant gas, and to improve the reliance of a fuel cell by simplifying the structure of a separator and a stack. CONSTITUTION: The molten carbonate salt fuel cell comprises a laminate of a plurality of unit cells(8) comprising a pair of air porous electrode plates(9a, 9b), a pair of fuel porous electrode plates(11a, 11b), and an electrolyte plate(10) located between a pair of air porous electrode plates(9a, 9b) and a pair of fuel porous electrode plates(11a, 11b), with interposing a separator(3), wherein the separator comprises a fuel electrode-side mask plate(4a) at the upper part and an air electrode-side mask plate(4b) at the lower part with a center of a center plate(6) to allow an oxidant gas to react with a fuel gas by passing through a channel. Inner manifolds(12a, 12b, 12c) are connected with oxidant gas introduction and discharge manifolds(14a, 14b, 14c) to allow the oxidant gas to be introduced through an inner manifold(12a) formed at the central part of the separator so as to react by passing the channel and to be discharged through the manifolds(14b, 14c) located at both sides. The fuel gas is introduced through an inner manifold(13a) formed at one side part of the separator to react by passing the channel and is discharged through fuel gas introduction and discharge manifolds(15a, 15b) located at opposite side part.

Description

Molten carbonate fuel cell with simplified central distribution separator}

The present invention relates to a molten carbonate fuel cell having a central distribution type separator. More specifically, an internal manifold for introducing an oxidant gas having a much higher flow rate is provided at the center of the separator plate, and internal manifolds for discharging gas after reaction are provided on both sides of the separator plate, thereby providing an oxidant gas flow path. By shortening the length, the pressure generated by the gas flow is reduced to enable the supply of a large amount of oxidant gas to suppress the occurrence of high temperature parts, and the fuel gas is supplied through the internal manifold installed on one side of the separation plate to the opposite side. The present invention relates to a molten carbonate fuel cell using a centrally distributed separator that can be discharged through an installed internal manifold to simplify the structure of the separator and the stack, thereby improving the reliability and economy of the fuel cell.

In recent years, the development of high efficiency and environmentally friendly fuel cells has been spotlighted as a new electric energy source. This fuel cell has a characteristic of continuously generating power by supplying fuel, and mainly uses hydrogen as a fuel and oxygen in the air as an oxidant to generate water through oxidation of hydrogen and reduction of oxygen. It is a system.

In particular, the molten carbonate fuel cell is a system that generates electricity at a relatively high temperature because an electrolyte made of carbonate melts at a high temperature to cause an electrode reaction, and does not require an expensive noble metal catalyst for oxidation of hydrogen and reduction of oxygen, such as carbon monoxide. It is easy to use the poisonous gas, and it has the characteristic that coal gas can be used as a fuel, and it has the characteristic that it can use high temperature waste heat and high efficiency.

The molten carbonate type fuel cell uses a porous electrode having a large surface area to facilitate the electrode reaction, and the molten carbonate impregnated in the ceramic porous body between the two electrodes is mainly composed of hydrogen and an oxidant composed of oxygen and carbon dioxide. It prevents direct contact with and serves as a passage through which carbonate (CO ₃ ^2- ) generated from the cathode moves to the anode.

H ₂ + CO ₃ ^2- → H ₂ O + CO ₂ + 2e- (Fuel pole)

1 / 2O ₂ + CO ₂ + 2e- → CO ₃ ^2- (air electrode)

Most fuel cells operate at high fuel utilization conditions to improve efficiency, while molten carbonate fuel cells operate at low oxidant utilization conditions for stack cooling during power generation. In addition, since oxygen in the air is used as the oxidant, the flow rate of the oxidant gas is several times higher than that of the fuel gas.

As with all fuel cells, the molten carbonate type fuel cell has a low theoretical electromotive force of about 1 V, which is not suitable for practical use. These unit cells are connected in series, and the voltage is increased to form a power generation system having an appropriate capacity. That is, a unit cell composed of a pair of porous electrode plates (fuel electrode and air electrode) and an electrolyte plate impregnated with alkali carbonate therebetween is laminated via a conductive separator plate. At this time, the separator serves to provide an electrical connection between each unit cell and to provide a flow path of fuel gas to the anode and a flow path of oxidant gas to the cathode.

Such a stacked fuel cell requires a manifold having a function of distributing and recovering reactant gas. The gas required for the reaction is supplied through an inlet manifold, and then passes through an air electrode and a fuel electrode reaction. Will be discharged. In the periphery of each unit cell, a wet seal portion made of molten carbonate is formed to prevent mixing of the gas inside the battery and the outside gas. This wet seal prevents leakage between manifolds.

However, in the fuel cell, part of the energy of the fuel is converted into electrical energy, and the rest is usually converted into heat. Therefore, in the case of the laminated fuel cell, the amount of heat generation varies depending on the degree of stacking, but as the number of stacks increases, the amount of heat generated increases and a high temperature portion is generated at the outlet portion of the gas. These high temperatures adversely affect the electrodes, electrolytes and separators that are fuel cell components. In other words, changes in the porous structure due to the high temperature of the porous electrode, evaporation of the liquid electrolyte, increase of corrosion of the metal separator, electrolyte consumption and deformation of the separator, and leakage of fuel gas due to this cause the fuel cell body. It can greatly shorten the service life.

In order to suppress the occurrence of such a high temperature part, a method of supplying an excessive amount of oxidant gas, which has a much higher flow rate and air as a main component, is mainly used. However, excess air supply in a given flow path will provide resistance to gas movement in the flow path, causing an increase in pressure. In the molten carbonate fuel cell, fuel and oxidant gas are segregated in the form of a wet seal by an electrolyte impregnated with a porous ceramic. However, when an excessive amount of oxidant is supplied to suppress the high temperature part, excessive pressure rise occurs in the flow path, and a wet seal is broken, which may cause leakage of fuel gas and greatly limit the life of the fuel cell body.

For example, Japanese Patent Laid-Open Nos. 62-202,465 and 61-248,364 use internal and external manifolds in the fuel cell body, and the introduction and discharge of fuel gas uses internal manifolds, and the amount of gas is large. The oxidant gas mainly used for cooling has a long oxidant gas flow path because it uses an external manifold. In these systems, a large amount of oxidant gas must be used to suppress a high temperature part during power generation, and thus, the pressure generated causes inevitable destruction of the wet seal and subsequent fuel gas leakage. In addition, Korean Patent Publication No. 2003-32310 distributes fuel gas and oxidant gas centrally so that the effect of suppressing the hot portion is excellent, but the separation plate structure and the stack structure are complicated, which makes it uneconomical.

Accordingly, an object of the present invention is to provide a molten carbonate fuel cell having a high temperature part suppression effect of a fuel cell body and a centrally distributed separator having a simplified separation plate and stack structure, which the prior art does not have.

The present invention also suppresses the occurrence of high temperature parts that greatly affect the life of the molten carbonate fuel cell, and also has a molten carbonate having a centrally distributed separator that can solve the inefficiency of the fuel cell due to the use of a complicated separator. The purpose is to provide a fuel cell.

1 is an exploded perspective view for illustrating a schematic configuration of a molten carbonate fuel cell corresponding to an embodiment according to the present invention;

FIG. 2 is a partially cutaway perspective view of the separator in the fuel cell of FIG. 1;

3 is a plan view of the separator of FIG. 2,

4A is a cross-sectional view of the fuel cell taken along the line A-A of FIG.

4B is a cross-sectional view of the fuel cell taken along line B-B of FIG. 3.

<Description of the symbols for the main parts of the drawings>

1: fuel cell body, 2a, 2b: end plate,

3: separator plate, 4a: anode mask plate,

4b: air electrode mask plate, 5a, 5b: anode corrugated plate,

7a, 7b: air cathode corrugated plate, 6: center plate,

8: unit cell, 9a, 9b: air electrode porous electrode plate,

11a, 11b: fuel electrode porous electrode plate, 10: electrolyte plate,

12a: oxidant gas introduced internal manifold,

12b, 12c: oxidant gas discharge internal manifold,

13a: internal manifold for fuel gas introduction,

13b: fuel gas exhaust internal manifold,

14a: oxidant gas introduction manifold,

14b, 14c: oxidant gas exhaust manifold,

15a: fuel gas introduction manifold, 15b: fuel gas discharge manifold,

O: oxidant gas, R: fuel gas.

The present invention is made by stacking a plurality of unit cells in which an electrolyte plate is disposed between a pair of cathode porous electrode plates and a pair of anode porous electrode plates via a separator plate, and the separator plate comprises an oxidant and a fuel gas. A molten carbonate type fuel cell composed of a mask plate on the anode side and a cathode mask plate on the lower side centering on the center plate so as to react through the flow path. The oxidant gas introduction and discharge manifolds are respectively connected to the internal manifolds so that the oxidant gas is introduced through the flow path and reacted through the flow paths and then discharged through the internal manifolds located at both sides thereof. Fuel gas is introduced through an internal manifold located on one side of the After the reaction, the fuel gas introduction and discharge manifolds are connected to each other so that they can be discharged to the internal manifold on the other side.

In particular, the molten carbonate fuel cell of the present invention is characterized in that the cross-sectional area of the internal manifolds on both sides is smaller than that of the central internal manifold.

In the present invention, the oxidant gas is supplied through an internal manifold located at the center of the fuel cell main body to supply the oxidant gas, which has a relatively high flow rate, which can suppress the occurrence of the high temperature part. It is discharged through the inner manifold installed on the side, the fuel gas with a relatively small flow rate is supplied from the inner manifold at one end to pass through the anode and is discharged through the inner manifold located at the opposite end .

This invention will be described in more detail with reference to the accompanying drawings.

According to the present invention, a high temperature portion is formed by heat generated during generation of a molten carbonate fuel cell, and the leakage of fuel gas is caused by the structural change of the porous electrode, the evaporation of the liquid electrolyte, and the corrosion and deformation of the metallic separator plate. In order to reduce the performance and life of the fuel cell, the internal manifold for the introduction of the oxidant gas with a much higher flow rate is installed in the center of the separator plate, and the inside for the discharge of the gas after reaction on both sides of the separator plate. By installing a manifold, the passage length of the oxidant gas is shortened to reduce the pressure generated by the gas flow to enable the supply of a large amount of oxidant gas, to suppress the occurrence of high temperature parts, and the fuel gas is provided on one side of the separator plate. Supplied through the installed internal manifold and discharged through the installed internal manifold on the opposite side, As the power plant due sikimeuro simplify tank is to improve the reliability and economic efficiency of the fuel cell.

1 is an exploded perspective view for illustrating a schematic configuration of a molten carbonate fuel cell corresponding to an embodiment according to the present invention, and FIG. 2 is a partially cutaway perspective view of a separator in the fuel cell of FIG. 1. 3 is a plan view of the separator of FIG. 2, FIG. 4A is a cross-sectional view of the fuel cell taken along line AA of FIG. 3, and FIG. 4B is a cross-sectional view of the fuel cell taken along line BB of FIG. 3.

In Fig. 1, reference numeral 1 denotes a fuel cell body having a lamination structure in its entirety. The fuel cell body 1 has a structure in which a plurality of unit cells 8 are stacked via a separator plate 3 between the upper end plate 2a and the lower end plate 2b.

The unit cell 8 includes an electrolytic plate 10 between a pair of cathode porous electrode plates 9a and 9b made of nickel-based alloy and a pair of anode porous electrode plates 11a and 11b made of nickel-based alloy. It is located and composed. The air electrodes 9a and 9b and the fuel electrodes 11a and 11b are divided at predetermined intervals D. The electrolyte plate 10 is impregnated with a ceramic carrier such as lithium aluminate such as a molten salt electrolyte prepared by mixing lithium carbonate, potassium carbonate or the like.

As can be seen in FIG. 2, the separator plate 3 has anode pleat plates 5a and 5b and cathode pleats which allow gas to pass between the anode side mask plate 4a and the cathode side mask plate 4b. Plates 7a and 7b are positioned with center plate 6 interposed therebetween. The cathode and anode mask plates are portions in direct contact with the electrolyte plate 10 and are portions in which the fuel cell is exposed to the corrosive molten carbonate electrolyte during normal operation. In order to prevent corrosion of this portion, the mask plate is subjected to corrosion resistant surface treatment, for example, aluminum surface treatment, on a portion of the stainless steel (STS 316, etc.) directly contacting the electrolyte plate 10.

The cathode corrugated plates 7a and 7b use stainless steel (STS 316, for example), and the anode corrugated plates 5a and 5b use nickel coated on stainless steel corrugated plate (STS 316, for example). . In addition, the separator 3 is provided with an internal manifold for distributing oxidant gas and fuel gas. The center plate 6 and the cathode mask plate 4b are joined to the internal manifolds 12a, 12b, and 12c for the oxidant gas so that only the oxidant gas which is the cathode gas passes therethrough. In contrast, the center plate 6 and the anode mask plate 4a are joined to the internal manifolds 13a and 13b for fuel gas, so that only the fuel gas can pass therethrough. The center plate 6 and the anode mask plates 4a and 4b are joined at the periphery of the separator plate so that gas leakage does not occur.

3, the oxidant gas introduced into the unit cell through the central oxidant gas introduction manifold 12a is discharged through the discharge manifolds 12b and 12c after participating in the electrochemical reaction required for power generation at the electrode part. Will be. The fuel gas introduced through the fuel gas introduction manifold 13a on one side of the separator plate is discharged through the fuel gas discharge manifold 13b on the opposite side across the separator plate.

In addition, in the end plate 2a positioned above the fuel cell body 1 , the cathode mask plate 4b and the corrugated plates 7a and 7b are provided on the bottom surface thereof. In addition, an anode mask plate 4a and a corrugation plate 5a, 5b are provided on the upper end surface at the lower end plate 2b. An oxidant gas connected to the oxidant gas introduction manifold 14a for introducing the oxidant gas into the oxidant gas introduction internal manifold 12a and the oxidant gas discharge internal manifolds 12b and 12c is provided at the center of the lower end plate 2b. The discharge manifolds 14b and 14c are provided, the fuel gas introduction manifold 15a is connected to the fuel gas introduction internal manifold 13a which introduces fuel gas, and the fuel gas discharge internal manifold 13b. The fuel gas discharge manifold 15b connected to is provided.

When the fuel cell is raised to a predetermined operating temperature, the electrolyte melts, and a wet seal is formed between the anode mask plate 4a, the cathode mask plate 4b, and the electrolyte plate to form the fuel gas R and the oxidant gas. (O) does not come into contact. In this state, an electrochemical reaction occurs at the anode and the cathode, and the fuel cell generates electrical energy.

The oxidant gas O supplied through the oxidant gas introduction manifold 14a is vertically distributed from the oxidant gas introduction internal manifold 12a to each unit cell as shown in the cross-sectional views of the fuel cell body of FIGS. 4A and 4B. Each of the distributed gases moves in a horizontal direction to perform a reaction required for power generation, and then moves downward through the oxidant gas discharge internal manifolds 12b and 12c at both ends, and then the oxidant gas discharge manifold 14b, Through 14c). The fuel gas supplied through the fuel gas introduction manifold 15a is supplied to the fuel gas introduction internal manifold 13a at one edge of the separation plate as shown in FIG. 4 to perform an electrode reaction necessary for power generation, and then to the opposite fuel gas. It is discharged through the discharge internal manifold 13b and the fuel gas discharge manifold 15b.

The molten carbonate fuel cell of the present invention supplies a large amount of oxidant gas by supplying an oxidant gas having a much higher flow rate than the fuel gas flowing across the stack to an internal manifold located at the center of the stack. And the occurrence of a high temperature portion in the stack is suppressed by the low inlet gas temperature in the center portion.

As described above, according to the present invention, the generation of the high temperature part in the fuel cell is suppressed to have durability as a power generation system, and due to the simplified separator and stack structure, there is an effect of increasing reliability and economy.

Claims (2)

The unit cell 8 constituted by the electrolyte plate 10 positioned between the pair of cathode porous electrode plates 9a and 9b and the pair of anode porous electrode plates 11a and 11b is used to mediate the separator plate 3. The separation plate 3 is formed on the fuel electrode side mask plate 4a and the lower part of the center plate 6 so that the oxidant and fuel gas can react while passing through the flow path. In the molten carbonate fuel cell constituted by the cathode side mask plate 4b, The oxidant gas is introduced through the internal manifold 12a at the center of the separator 3 and reacts through the flow path so as to be discharged through the internal manifolds 12b and 12c located at both sides. An oxidant gas inlet and outlet manifolds 14a, 14b, and 14c are connected to the inner manifolds 12a, 12b, and 12c, respectively, and are disposed on one side of the separation plate 3, respectively. The fuel gas introduction and discharge manifolds 15a and 15b are connected to each other so that the fuel gas is introduced through 13a) and reacted through the flow path and then discharged to the internal manifold 13b on the other side. Molten carbonate fuel cell having a central distribution type separator, characterized in that. 2. The molten carbonate fuel cell having a central distribution separator as claimed in claim 1, wherein the cross-sectional areas of the inner manifolds 13a and 13b on both sides are smaller than the inner manifold 12a on the center. .