JPS636754A - Initial startup method of molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To prevent generation of cracks in an electrolyte plate by temporarily assembling a cell so that an electrolyte plate is made free between gas separating plates, melting carbonate in the electrolyte plates, then assembling the cell by applying a specified fastening force to the electrolyte plates. CONSTITUTION:An anode 2 and a cathode 3 are arranged on each side of an electrolyte plate 1, and they are fastened from both sides with gas separating plates 4 to form a molten carbonate fuel cell. In starting initial operation, a cell is temporarily assembled so that the electrolyte plate 1 is made free by arranging a spacer 6 in the periphery of the electrolyte plate 1, and the temperature of the cell is increased to melt carbonate retained in the electrolyte plate 1. Then, the spacer 6 is removed with this state kept, and the cell is assembled by applying a specified fastening force to the electrolyte plate. Reaction gasses are supplied to operate the cell. Generation of cracks in the electrolyte plate caused by temperature increase is prevented, and initial operation is safely started.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for starting up a molten carbonate fuel cell.

[Prior art and its problems]

First, FIG. 3 shows the general structure of a molten carbonate fuel cell. In the figure, 1 is an electrolyte plate with a paste structure made by mixing and solidifying ceramic powder such as lithium aluminate and electrolyte carbonate powder such as lithium carbonate or calcium carbonate. The anode electrode is made as a porous sintered plate of nickel or nickel, cobalt, and chromium alloy. Cathode electrode 3
, and a gas component M temporary 4 made of stainless steel are arranged, and a corrugated current collector plate is interposed between each electrode 2, 3 and the gas component Mj54 to constitute a single cell. 'By the way, in order to initially operate such a molten carbonate fuel cell, first, the cell assembly shown in FIG. Generally, a method is adopted in which the temperature is raised to the temperature at which the carbonate melts, and then the battery is further raised to the operating temperature, and then fuel and reactant gas of the oxidizer are supplied to the anode and cathode sides to start operation. However, in the conventional initial operation start-up method described above, the temporary electrolyte often cracks during the temperature rising process. Moreover, when such a situation occurs, so-called cross leakage of reaction gas occurs in which the fuel gas and oxidizing gas are mixed together through the cracks in the electrolyte plate 1, and depending on the degree of gas mixing, the battery voltage may drop, and furthermore, combustion may occur. There is a risk of this developing into a serious malfunction such as an explosion. According to the inventor's investigation into the cause of the electrolyte plate cracking described above through various experiments and considerations, the cause is the electrolyte plate 1. Due to the difference in temperature expansion coefficient due to the difference in the materials of the electrodes 2, 3 and the gas separation plate 4, and the volume expansion when the carbonate retained in the electrolyte changes from the solid phase to the liquid phase, the battery assembly It has been found that when the temperature is increased in a tightened state, strain is applied to the temporary electrolyte 1 due to the above-mentioned temperature expansion coefficient difference and volumetric expansion due to melting of the carbonate, causing cracks to occur.

[Purpose of the invention]

This invention has been made in view of the above points, and provides an initial operation start-up for a molten carbonate fuel cell that enables operation to be established by preventing the electrolyte from cracking during the temperature rise process at the start of initial operation. The purpose is to provide a method.

[Key points of the invention]

In order to achieve the above object, the present invention includes a temporary assembly process in which the battery is assembled by inserting the electrolyte plate freely between the gas separation plates without applying any clamping pressure as a preparatory step for starting the initial operation; A heating step in which the cell temperature is raised from room temperature in the assembled state to melt the carbonate temporarily held in the electrolyte, and a main assembly step in which the battery assembly is tightened at a predetermined tightening pressure while the temperature remains elevated are sequentially carried out. After that, the reactant gas is supplied to establish operation. In the above-mentioned temporary assembly process, the electrolyte plate is held in a free state between the gas separation plates by, for example, interposing a spacer thicker than the thickness of the electrolyte plate in the circumferential area of the electrolyte plate, and In this assembly process, the spacer is removed and the battery assembly is tightened. In other words, in the process of the experiment and discussion to investigate the cause of cracking of the electrolyte tentative mentioned above, if the electrolyte tentative is in a free state without being mechanically restrained, the gas separation plate. It has been found that cracks do not occur during the temperature rising process because it is not affected by the difference in temperature expansion between it and other materials. Therefore, as in the startup method described above, by leaving the electrolyte plate in a free state without applying any clamping force during the heating process until the carbonate becomes molten, cracking of the electrolyte plate can be reliably prevented. . Note that once the carbonate is in a molten state, even if the battery assembly is tightened in the main assembly process and the temperature is raised to a higher operating temperature, there is no risk that the electrolyte will crack.

[Embodiments of the invention]

First, FIGS. 1 and 2 show the assembled state of a battery in the temporary assembly step in the method of the present invention. In the figures, the same members corresponding to FIG. 3 are given the same reference numerals. In other words, plate pressure 1
．． Slight notches 1a are formed in advance at four locations around the 5 mm temporary electrolyte plate 1, and a spacer 6 with a plate thickness of 148cm, which is 0.3cm thicker than the plate thickness of the electrolyte plate 1, is inserted into this notch 1a. and upper and lower gas separation vi together with electrolyte plate l
, 4. Therefore, in this temporarily assembled state, the electrolyte plate 1 is only placed s2 on the lower gas separation plate 4 and is in a free state without being restrained between it and the upper gas separation plate. Now, when starting the initial operation of a tri-fused carbonate fuel cell, as a preparatory step before starting operation, first, in the temporary assembly step, as shown in Figures 1 and 2, without applying any tightening force. Temporarily assemble the battery. In the subsequent temperature raising step, the cell temperature is raised from room temperature to 52Q° C. in the temporarily assembled state. When this heated cell temperature is reached, the carbonate held in the electrolyte plate 1 is completely molten.The process moves on to the 6th main assembly process, where the spacer 6 is removed from the battery assembly while the temperature is rising. The battery was assembled by applying a predetermined tightening pressure of 2 kg/cd, and the cell temperature was adjusted to the battery operating temperature (50°C).
increase to At this point, the pre-operation (faB) is ready, and then fuel and oxidant gas are supplied to the anode and cathode sides of the battery to establish initial operation. According to the actual operation of the battery, the open circuit voltage after operation was established was 1080 FV.There was no cross leakage of the reaction gas due to kneading, and therefore the electrolyte did not crack during the heating process. T11! It was confirmed that a healthy state in which the electrolytic
As mentioned earlier, cross-leakage of waste occurs through the temporary cracks in the electrolyte, and the reaction gases mix, and depending on the degree of force and force mixing, the open circuit voltage decreases from the above (1), and the gas If there is no cross leak at all, the open circuit voltage will show the above value, and thereby the temporary health of the electrolyte can be determined from the open circuit voltage. [Effects of the Invention] As described above, according to the present invention When starting the initial operation of the fuel cell 5, there is a temporary assembly process in which the battery is assembled by inserting the electrolyte in a free state between the gas separation plates without applying any clamping pressure as a preparatory process, and a preliminary assembly process in which the battery is assembled in a free state between the gas separation plates. A temperature raising step in which the cell temperature is raised from room temperature to melt the carbonate temporarily held in the electrolyte, and a main assembly step in which the battery assembly is tightened with a predetermined tightening pressure while the temperature remains elevated are sequentially performed. By supplying the reactive gas and starting operation later, it is possible to reliably prevent cracks from occurring in the electrolyte plate during the battery rising process, which in turn reduces the battery voltage due to cross leakage of the reactive gas. It is possible to safely start the initial operation by preventing troubles such as combustion and explosion caused by the mixture of reaction gases.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the pre-assembled state of the battery in the pre-assembly step of the method of the present invention, FIG. 2 is a plan development view of the temporary electrolyte and spacer in FIG. 1, and FIG. 3 is a molten carbonate fuel cell. FIG. 2 is a cross-sectional view showing the general structure of. In each figure, 1: tSif award plate, 1a: notch, 2 near-node electrodes. 3: cathode electrode, 4: gas separation plate, 5: waveform collection tvi
, 6 = spacer. 'fAdult Patent Attorney Yamaguchi Father-in-law 2nd figure

Claims (1)

[Claims] 1) Preparation for operation at the initial start of operation of a molten carbonate fuel cell comprising an anode electrode, a cathode electrode, and a gas separation plate arranged on both sides of an electrolyte plate holding carbonate. The steps include a temporary assembly process in which the battery is assembled by freely inserting the electrolyte plate between the gas separation plates without applying any tightening pressure, and a temporary assembly process in which the cell temperature is raised from room temperature in the temporarily assembled state to be held by the electrolyte plate. a heating step to melt the carbonate that is
A molten carbonate fuel cell characterized in that the main assembly process of tightening the battery assembly at a predetermined tightening pressure while in a heated state is performed in order, and then a reaction gas is supplied to establish operation. How to start up initial operation. 2) In the initial operation start-up method described in claim 1, a spacer thicker than the thickness of the electrolyte plate is juxtaposed around the electrolyte plate during the temporary assembly process, and is interposed between the gas separation plates. A method for starting initial operation of a molten carbonate fuel cell, comprising removing the spacer during an assembly process.