JPS6178066A - Method for manufacturing electrolytic tiles of fused carbonate fuel cell - Google Patents

Abstract

PURPOSE:To facilitate assembling work and large-sized construction of fused carbonate fuel cell (MCFC) and to improve economization and cell output perfor mance by impregnating electrolytic matter in a sheet in a process of rising temperature of cell structure. CONSTITUTION:A cell structure is assembled with a predetermined sheet type matter. An alumina pot 21 containing electrolytic matter therein is placed in a hole made by machining on the peripheral portion of a holding plate. And alumina pipe 22 connected to the pot 21 is adjacent to the sheet type matter. The cell structure is inserted in an electric furnace 23 and heated up to an operating temperature of 650 deg.C. Near approx. 490 deg.C, the electrolytic compound becomes molten and impregnation into a thin hole portion from which wood pulp is pulled out starts. Around 500 deg.C, the electrolyte is completely impregnated in the thin hole portion of the sheet type matter and electrolytic tile is made and completed as MCFC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] This invention relates to a method for producing electrolyte tiles for molten carbonate fuel ponds.

[Prior art and its problems]

Molten carbonate fuel cells (hereinafter referred to as MCFCs) are manufactured using electrode plates, electrolyte tiles, and various cell components having the required shapes and characteristics manufactured in each process.
It consists of one piece as shown in the figure. In Fig. 3, 1 is an electrolyte tile, and 2 and 3 are electrodes made of porous nickel or nickel alloy.

The cathode electrode of No. 3 is a porous plate of nickel oxide. Further, t in FIG. 3 is a cell frame, and an insulating plate 6 is inserted between this and the holding plate 5, and the electrolyte tile 1 and the electrodes 2 and 3 are tightened with bolts 7 and nuts 8. It has become. Then, after charging this into an electric furnace and raising the temperature to 650°C, by supplying fuel and oxidizer from the gas chamber 10 arranged on the anode side and the cathode measuring electrode, electricity is applied to both 1jL electrodes. Energy is generated. This electrical energy is transmitted to the cell frame 4 via the collector 9, and can be taken out to the outer frame through the IL flow extraction line 11.

An electrolyte tile with the above structure uses an alkali metal carbonate as the electrolyte and operates at high temperatures (5000-800°C).
In CFC, the electrochemical reaction is as follows:
The ionic conduction proceeds as shown in Equation 21, and the ionic conduction is carried out by carbonate ions (C
OI).

7/-do: H! +CO, -+H, 0+COx +2e
...(f) Cathode: l/20x +CO* +2
e −+ COs −f2) This cell has a high operating temperature of 500°C or higher, so the reaction rate is fast, and unlike room-temperature fuel cells, it does not require an expensive platinum metal catalyst. Features include the ability to obtain high current density even with fuel.

However, due to the high operating temperature and the use of highly corrosive alkali metal carbonates.

■For electrodes, the electrochemical properties deteriorate due to the growth and corrosion of the nickel particles that make up the electrodes. ■For electrolyte tiles, damage occurs during assembly, and the electrolyte retention ability of the lithium aluminate holding material decreases, resulting in damage due to heat cycles. ,
■Progressing corrosion is a problem for battery constituent materials such as cell frames and collectors.

By the way, in the configuration of an MCFC, the electrolyte tile plays a particularly important role, and if defects such as holes or cracks occur in the electrolyte tile during battery operation, mixing of fuel and air, or crossover, will occur, which will reduce the battery output. This can be a fatal cause of loss of performance. For this reason I'vl
CFC electrolyte tiles are required to have the following properties.

(1) High mechanical strength (2) No defects such as clutter even after heat cycling (3) Excellent heat resistance (4) Stable retention of electrolyte (5) Ionic conductivity In addition, since electrolyte tiles account for a large proportion of the manufacturing cost of M CF C, efforts are being made to develop materials with excellent economic efficiency and simple manufacturing processes.

An MCFC electrolyte tile consists of a holding material for holding an electrolyte melt and an alkali metal carbonate as an electrolyte. As a retaining material, lithium aluminate, which is synthesized by a carbonate mixing method using alumina and lithium carbonate as raw materials, has been found to be optimal and is most commonly used.

Lithium aluminate has three allotropes: γ-1α- and β, and γ or α is used from the viewpoint of melt retention and mechanical strength. As the electrolyte, a mixture of lithium carbonate and potassium carbonate having a eutectic composition among alkali metal carbonates is used. The eutectic composition of both is 47.5
% lithium carbonate - 52.5% potassium carbonate (weight ratio)
and its eutectic temperature is about 491°C. Further, the ratio (weight ratio) of the lithium aluminate holding material to the eutectic electrolyte is generally in the range of 5:5 to 4:6.

The methods of manufacturing electrolyte tiles for MCFC known so far are as follows.

fil A so-called paste method in which a mixed powder of γ-lithium aluminate and a eutectic electrolyte is pressure-molded at room temperature and sintered at around 5,000 ℃.

(2) Mixed powder of γ-lithium aluminate and eutectic composition electrolyte was heated in the temperature range of 4600 to 490°C.
．． Pressurize at a pressure of Oton/cj, and keep this pressurized state at 1
The so-called hot press method is held for 5 to 150 minutes.

(3) γ-lithium aluminate (adding a binder, molding at a pressure of 1 to 3.5 tonA, sintering, and using only a retaining material) A so-called mud that is impregnated with electrolyte melt after making IJ socks. IJ Knox method.

In the above-mentioned paste method, cranks are likely to occur in the molded product when the molding pressure is increased, and careful attention must be paid to the rate of temperature rise and fall to prevent cracks during sintering. There is a problem in that productivity is reduced by one hour because it takes one hour to raise and cool the temperature. Furthermore, the bulk density of the electrolyte tiles produced using this method is at most 85% of its theoretical value.
%, it has a weak mechanical strength and is prone to defects during the heat cycle of the fuel base oil.

The hot press method makes it easier to increase the bulk density of the electrolyte tile compared to the paste method.

It has the advantage of providing excellent mechanical strength. However, in order to increase the bulk density of the electrolyte tile, it is necessary to increase the pressing force.

For this purpose, a large press device is essential, which has the drawback of increasing equipment costs. In the hot press method as well, it is necessary to reduce the rate of temperature rise and fall as much as possible in order to avoid defects in the electrolyte tiles, so it is similar to the paste method (this has a drawback in terms of productivity).

The so-called matrix method includes the doctor blade method,
Examples include calendar method and electrophoresis method. These methods make it easier to produce large-area electrolyte tiles compared to the paste method and hot press method, but the manufacturing process is complicated and requires high temperature, which tends to increase manufacturing costs. It has the disadvantage of having extremely low mechanical strength and being easily damaged during handling. Furthermore, since the binder uses a large amount of organic materials that are harmful to the human body, safety and health measures are also required.

Therefore, kicPc constructed using the electrolyte tiles manufactured by the above method has insufficient battery output performance, the mechanical strength of the electrolyte tiles is poor, making it difficult to increase the area, and the manufacturing process is complicated, resulting in high costs. It has the problem of being expensive. In addition, M constructed using the electrolyte tiles of the above method
In CFC, when raising the temperature to an operating temperature of 650°C, the electrolyte tile is often damaged unless the temperature is 60'C or less per hour.

Another disadvantage of these electrolyte tiles is that they are susceptible to heat cycles.

[Purpose of the invention]

The object of this invention is to use a sheet-like material produced by a novel method as an electrolyte holding material to form a battery structure, and then impregnate the sheet-like material with an electrolyte during the process of heating the structure. The object of the present invention is to provide an MCFC that is easy to assemble and enlarge, and has excellent economic efficiency and battery output performance.

[Key points of the invention]

First, the circumstances that led the inventors to discover and complete the present invention will be explained.

Porous ceramic materials have traditionally been known as porous materials with continuous pores, such as unglazed pottery or sintered ceramic particles with a certain roughness, or porous materials with independent cells, such as foamed glass. It is being Also,
In recent years, there has been a spongy ceramic porous body such as Ceramic Foam, which is an open-pore type ceramic porous body that utilizes foaming of 7-ohm soft urethane and has a completely reversed volume ratio between the ceramic part and the pore part. It was intended to apply this method of making porous ceramics to the production of a matrix for holding electrolyte tiles. However, it has been found that it is difficult to manufacture the electrolyte tile holding material matrix using the method described above due to the following drawbacks.

[1. Hardness as a ceramic porous body! : Insufficient micro-density.

(2) When the pores are filled with various inorganic substances or solutes, there may be defects in ion permeability and single ion conductivity.

(3) Even if the ion permeability and electron conductivity are satisfied, the pore diameter of the pores is large, so various inorganic substances and electrolytes tend to flow out from the pores.

On the other hand, the method for making a ceramic 7-piece is as follows:
Methods other than injection molding, extrusion molding, isostatic pressing, and paper-making methods may cause the surface to crack or warp, resulting in uniform properties when making large-area ceramic plates of 30 ctp or more. There is a risk that it is difficult to obtain something.

On the other hand, the paper-making method wet-mixes sinterable inorganic powder, wood pulp, and at least one type of organic fiber material selected from natural male and synthetic Q male, and after agglomeration, paper is made. A sheet-like product is obtained. This method can easily produce thin sheets with a large area compared to Ike's method, and/- The sheet is flexible and can be bent freely, making it easy to handle in a machine. . By baking the notebook-like material obtained by the papermaking method, the organic fiber material is burned out and a thin and large surface 2@
Porous ceramic bodies can be easily produced.

This porous material is strong when used as a seedling, has a low porosity, and has pores arranged like a labyrinth.

The present inventors focused on the characteristics and advantages of this paper method and previously applied for an invention in which it was applied to MCFC's 1'it solution tile as Japanese Patent Application No. 181485/1985.

The present invention is a further improvement of this invention, in which a sheet material formed by a papermaking method is incorporated into a battery as a holding material for an electrolyte tile, and then the organic fiber material is burned and scattered during the process of raising the temperature to the operating temperature. Workability is improved by impregnating the pores of this organic fiber material with an electrolyte melt to form an electrolyte tile.

This was an attempt to further improve positive outcomes.

[Embodiments of the invention]

The present invention will be explained in detail below. γ-lithium aluminate powder with a particle size of 20 μm or less is used as the electrolyte tile holding material, and in order to function as a reinforcing material and increase porosity,
Wood pulp is selected from various organic fibers, and the amount of wood pulp added is 3 to 15% based on the total weight of the sheet when dry.
% (weight ratio). This amount of addition was chosen to increase the porosity of the sheet material after the wood nokrug has been burned and scattered.
This is to set the concavity to 80 inches. The manufacturing method is as follows: First, 5 to 30 times the amount of water is added to the solid content of 3 to 15 inches of fiber and T-lithium aluminate powder, and the mixture is wet-mixed to create one aqueous slurry suitable for papermaking. Adjust,
A coagulant is added to agglomerate the product, which is then machined using a single trowel to form a sheet with a thickness of several inches.

This sheet-like material is used as a holding material for the electrolyte tile 1 shown in FIG. 3, and assembled into the battery structure shown in FIG. 1. 1st
In the figure, numeral 21 is an aluminium crucible containing electrolyte powder, and this aluminium crucible is installed in a hole drilled in the periphery of the holding plate. The alumina pipe 22 connected to the alumina crucible is in contact with the sheet-like material. This battery structure is charged into the electric furnace 23 shown in FIG. 1 and heated to an operating temperature of 650°C. Wood pulp starts to burn out around 450℃, and reaches 4800-490℃.
It will be completely burnt down and scattered. Then, at around 490° C., the electrolyte component becomes a melt, and the electrolyte begins to impregnate the pores through which the wood pulp has passed.

When the temperature reaches about 500°C, the pores of the sheet are completely impregnated with electrolyte, forming an electrolyte tile, and the MCF
Completed as C.

In addition, the electrolyte components necessary for impregnating the sheet material are prepared in an alumina crucible in the above example, but in addition to this, it is also possible to prepare a groove in the cell frame and fill this part with the required amount of electrolyte component. It is also possible to leave it as is.

Next, specific examples of the present invention will be described. In addition, all compositions are weight ratios.

<Example 1> Preparation of sample T-lithium atsubenate (average particle size 15 μm) 3
0 parts wood pulp 5 parts water
10
00 parts + Bl 15 parts of acid band aqueous solution as flocculant 30 parts Polyacrylamide-based bulky coagulant 0.2 parts aqueous solution 20 parts Manufactured by Sanyo Chemical Product name 30 parts of γ-lithium aluminate was added thereto and stirred for 1 minute to form an aqueous slurry. A sulfuric acid band (
Add 30 parts of a polyacrylamide polymer coagulant (Sunpoly N- Add 20 parts of 0.2% aqueous solution of 500) and stir for 1 minute to coagulate.

The sample agglomerated in the above manner was made into a paper using a paper making machine.
Store with crn corner 2. Make into a sheet of Om.

A 50 m++ diameter piece was cut out from this material to be used as a holding material for an electrolyte tile, and then a porous nickel electrode plate with a diameter of 35 square meters was assembled into a battery structure as shown in FIG.

The alumina crucible in Figure 1 has a eutectic composition electrolyte (47,5
% lithium carbonate-52.5% potassium carbonate) powder and load this into an electric furnace.

After that, the temperature was increased at a rate of 120°C per hour, and the temperature was increased to 65°C.
The wood pulp was also impregnated with electrolyte when it was burnt and scattered during the process of raising the temperature to 0°C. The ratio of tile holding material and electrolyte in this case was 45:55. ~ ICFC fuel Ckl configured in the above process is Air + 30% CO2,
A single cell test was conducted by supplying a gas of H2+CO to the air electrode. The current-voltage curve obtained at this time is shown in Figure 2 f.
This is shown. This characteristic was equal to or better than that of an MCFC constructed from electrolyte tiles manufactured by a conventional method, demonstrating the effectiveness of the present invention. In addition, no defects were observed in the electrolyte tile in this single cell test or a separate heat cycle test, confirming that the MCFC of the present invention is excellent in terms of durability and life characteristics.

Example 2 Sample preparation γ-lithium aluminate (average particle size) 3
0 parts wood pulp 1 part water
1000 parts (uniform flocculant sulfate band 15% aqueous solution 20 parts polymer shell agent 0.2 polyhydric solution 30 parts Sanyo Chemical @
Product name: ``Sump'JN-500'' Composition as above (
8), (Using the equation, N CF C was constructed in the same manner as in Example 1. In this case as well, it was confirmed that the battery performance was equivalent to that in Example 1.

In addition, in this example, the operating temperature of the solder fCF'C is 65
Although the heating rate up to 0° C. was set at 120° C. per hour, results have also been obtained that as long as the heating rate is within the range of 200° C. per hour, no defects will occur in the electrolyte tile.

〔Effect of the invention〕

As described above, according to the present invention 1ζ, after assembling a battery using a sheet made of γ-lithium aluminate produced by a papermaking method and wood pulp as an electrolyte tile holding material, the temperature is raised to the operating temperature of MCF'C. In the process of forming continuous pores in the sheet material, these pores are impregnated with electrolyte melt to form electrolyte tiles, which prevents damage to the tiles and simplifies the assembly process. MC with excellent economy, durability, and battery performance.
Can provide FC. Further, according to the present invention, it is easy to increase the size of the MCPC, which greatly contributes to promoting the development of high-temperature fuel cells.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a fuel cell showing an embodiment of the present invention, Fig. 2 is a graph showing current-section pressure of a single cell test according to the present invention, and Fig. 3 is a side view showing a conventional fuel cell. It is a diagram. 1:i! Electrolyte tile 2 near node electrode, 3: cathode electrode, 4: cell frame, 5: holding plate, 6: insulating plate, 7: bolt, 8: nut, 9: current collector, lO: gas chamber,
11: 1 flow extraction line, 21 Ni aluminum crucible, 22 Ni aluminum nano ζ Eve, 23: 111 air furnace. 23't*Konazai 1's

Claims (1)

[Claims] In a molten carbonate fuel cell consisting of an air electrode, a fuel electrode, an electrolyte tile, and a cell frame, γ-lithium aluminate powder and at least one organic fiber selected from wood pulp, natural fiber, and synthetic fiber are used. After wet-mixing the fibrous materials to form an aqueous slurry, agglomerating the resulting sheet material, and assembling the obtained sheet into a battery structure as an electrolyte tile holding material, the above-mentioned organic A method for manufacturing an electrolyte tile for a molten carbonate fuel cell, which comprises burning and scattering fiber material and impregnating a sheet material with an electrolyte component consisting of lithium carbonate and potassium carbonate to form an electrolyte tile.