JPH08321318A - Electrolyte refilling device of fused carbonate type fuel cell - Google Patents

Abstract

PURPOSE: To supply and refill carbonate at the same time to a wide range of electrolyte matrix in a simple structure, and besides, to supply and refill carbonate after layering of a fuel cell. CONSTITUTION: A stack 15 is constituted by layering cells and separators so that the end face of the margin of electrolyte matrix may be exposed to atmosphere outside the stack, and its stack 15 is accommodated in a carbonate bath 22. Carbonate is accommodated in advance in the carbonate bath 22, or the carbonate is supplied from the carbonate supply and discharge pipe 23 at the time of supply of carbonate, and when the supply of carbonate is completed, the carbonate remaining in the carbonate bath is discharged from the carbonate supply and discharge pipe 23. Hereby, the carbonate penetrates and is supplied to electrolyte matrix from the exposed section of electrolyte matrix, and further it is supplied to an anode electrode and a cathode electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte replenishing device for a molten carbonate fuel cell using molten carbonate as an electrolyte.

[0002]

2. Description of the Related Art Generally, a molten carbonate fuel cell is one in which a fuel supplies gas and an oxidant gas to a pair of electrodes sandwiching an electrolyte layer to cause a cell reaction. A plurality of layers are laminated with a separator serving as a path interposed therebetween. A eutectic salt of Li2CO3 (lithium carbonate) and K2CO3 (potassium carbonate) is used as the electrolyte, and the eutectic carbonate is impregnated in the electrolyte matrix.

A unit cell composed of a pair of electrodes sandwiching an electrolyte matrix and one separator each stacked are called a unit cell. FIG. 6 shows a single cell of a molten carbonate fuel cell and a single cell in which one separator is stacked.

The unit cell 1 is constructed by sandwiching an electrolyte matrix 2 between an anode electrode 3 and a cathode electrode 4, and the separator 5 is constructed by sandwiching an interconnector 6 between an anode edge plate 7 and a cathode edge plate 8. Separator 5
An anode current collector plate 9 and a cathode current collector plate 10 that secure a gas flow path inside and electrically connect adjacent cells to each other.
Are provided, and the fuel gas 11 and the oxidant gas 12 are respectively supplied. When the gas flows in the separator, the fuel gas 11 is generated on the surface of the anode electrode 3 by the oxidizing gas 1
2 causes a cell reaction on the surface of the cathode electrode 4, and a carbonate ion (CO
3 2-) is exchanged and electric output is obtained outside the battery.

FIG. 6 shows one unit cell 1 and one separator 5
A single cell obtained by stacking the individual cells is shown, but the battery stack is configured by repeatedly stacking the single cells. At this time, the interconnector 6 includes the anode edge plate 7 and the cathode edge plate 8
It is integrated with.

The fuel gas 11 and the oxidant gas 12 supplied to the unit cell 1 are supplied and discharged by separate manifolds provided around the unit cell 1. In FIG. 6, the manifold is an internal manifold type molten carbonate fuel cell in which the manifold 5 is provided inside the separator 5, and the anode edge plate 7 and the cathode edge plate 8 face each other across the unit cell 1.
Are connected by an electrically insulating manifold ring 13.

FIG. 7 is a sectional view taken along line AA of FIG. FIG. 7 shows a stack of two unit cells 1. As can be seen from FIG. 7, the anode current collector plate 9 and the cathode current collector plate 10 are composed of a portion that contacts the anode electrode 3 and the cathode electrode 4, and a protruding portion that forms a gas flow path. In general, the portion that contacts the electrode is called a current collector plate, and the protruding portion is called a current collector support. However, in the present invention, a combination of these is called a current collector plate. In the figure, 11A is a fuel gas flow channel, and 12A is an oxidant gas flow channel.

Further, the electrolyte matrix 2 is constructed to be slightly larger than the anode current collector plate 9 and the cathode current collector plate 10, and the separator 5 is so arranged that the end face of the periphery of the electrolyte matrix 2 is exposed to the atmosphere outside the stack. It is attached by being sandwiched between the anode edge plate 7 and the cathode edge plate 8. The contact surface of this portion is wetted by the molten carbonate, and the gas inside and outside the separator 5 is sealed, which is called a wet seal 14.

The stack is clamped from above and below by a clamping device, so that the electrical contact between the unit cell 1 and the separator 5 can be kept good, and the wet seal 14 can keep good gas seal. This tightening device usually comprises a tightening plate provided above and below the stack, and a stretchable tightening bellows interposed between the upper and lower tightening plates.

Next, the electrolyte matrix 2 is one in which carbonate is filled in the interstices of the skeleton having a porous structure composed of metal oxide particles. The carbonate is a solid at room temperature, but becomes a molten state at a temperature of 650 degrees, which is the power generation operating temperature. The anode electrode 3 and the cathode electrode 4 are porous bodies of metal or metal oxide, and the carbonate also partially fills the pore gaps between the anode electrode 3 and the cathode electrode 4.

During operation of this molten carbonate fuel cell,
The fuel gas 11 and the oxidant gas 12 supplied to the anode electrode 3 and the cathode electrode 4, respectively, generate an electrochemical reaction at the interface between the molten carbonate and the anode electrode 3 and the cathode electrode 4 to generate electricity. For stable power generation of such a molten carbonate fuel cell, it is necessary that the anode electrode 3, the cathode electrode 4 and the electrolyte in the electrolyte matrix 2 be constantly maintained in an appropriate amount during power generation.

Usually, this electrolyte is filled in a gas flow path for supplying an oxidant or a fuel gas at the time of assembling a fuel cell, or is incorporated in the form of a carbonate sheet, so that the carbonate of the carbonate is generated during the temperature rising process of the fuel cell. It is impregnated into the anode electrode 3, the cathode electrode 4 and the electrolyte matrix 2 at a melting temperature or higher. The molten carbonate is retained in the electrolyte matrix 2 by its surface tension and the interfacial tension between the skeleton particles of the electrolyte matrix 2 and the molten carbonate. In the fuel cell impregnated with the electrolyte, an appropriate amount of the electrolyte is distributed in a balanced manner to each of the anode electrode 3, the cathode electrode 4 and the electrolyte matrix 2 at the power generation temperature.

[0013]

However, when a carbonate sheet is sandwiched between the unit cells 1, the stack height of the fuel cell shrinks at the cell reaction portion when the carbonate melts, If the stacking height of the manifold portion does not follow the contraction, gas leakage from the wet seal 14 and poor electrical contact with the battery reaction portion may occur.

Further, when the gas channel is filled with carbonate, the gas cannot flow into the gas channel until the cell 1 is impregnated with the carbonate. In particular, when the anode current collector support is filled with a carbonate, the fuel gas cannot flow when the temperature of the fuel cell is raised, so the anode gas is generated by the oxidant gas 12 passing through the cell 1 not impregnated with the carbonate. There was a risk that the electrode 3 would be oxidized and deteriorated.

Further, for the time being, in a molten carbonate fuel cell aiming at a life of 40,000 hours, it is necessary for the carbonate to be stably retained in the electrolyte matrix 2 for a long period of time, but the carbonate is not Then you lose for three main reasons.

First, since the molten carbonate is in a liquid state during the power generation operation, the surface of the separator 5 or the like is gradually changed due to changes in the microstructure of both the anode electrode 3 and the cathode electrode 4 and the electrolyte matrix 2. leak.

Secondly, the molten carbonate is highly corrosive, corrodes the material of the metallic separator 5, and is consumed due to the corrosion.

Thirdly, the carbonate is volatilized in the fuel gas 11 or the oxidant gas 12 and discharged together with the gas.

In order to suppress the loss of carbonate due to these reasons, the development of an electrolyte matrix 2 having an excellent carbonate retaining power, the development of a material for the separator 5 which is not easily corroded by the carbonate, or the local formation of the unit cell 1 The development of driving technology that suppresses the temperature rise of the concrete and prevents the volatilization of carbonates is being carried out.

The carbonate is first preferentially lost from both the anode electrode 3 and the cathode electrode 4 having a pore size larger than that of the skeleton of the electrolyte matrix 2. When the amount of carbonate in the anode electrode 3 and the cathode electrode 4 is insufficient, the three-phase interface where carbonate and gas coexist on these electrode surfaces, that is, the area of the surface where the cell reaction occurs is reduced, and the internal resistance of the fuel cell is reduced. Will increase. Furthermore, the loss of carbonates has progressed,
When the carbonate in the electrolyte matrix 2 is insufficient, pores are generated in the electrolyte matrix 2 and the internal resistance of the fuel cell increases. Further, the fuel gas 11 and the oxidant gas 12 are directly mixed and burned, the gas is wastefully lost, and the electrolyte matrix 2 is heated due to the temperature rise due to the combustion.
Will accelerate the deterioration of.

Therefore, apart from the above-mentioned development, an attempt has been made to replenish the lost amount of carbonate. For example, Japanese Utility Model Laid-Open No. 62-127670 proposes a fuel cell having a structure in which an electrolyte supply path penetrating the stack is provided and the electrolyte is poured from the upper part of the stack. The electrolyte supply passage is provided so as to penetrate the electrolyte matrix and the edge plate at the wet seal portion so that the electrolyte poured into the electrolyte supply passage is absorbed by the electrolyte matrix. Further, a groove is provided on the surface of each separator in the wet seal portion, an electrolyte is supplied to the groove from an electrolyte supply path that penetrates the electrolyte matrix and the edge plate, and the electrolyte is absorbed from the groove to the electrolyte matrix. ing. However, with such a structure, a space for providing the electrolyte supply passage and the groove is required, and the structure is complicated, so that the supply place of the electrolyte is limited.

It is an object of the present invention to have a simple structure so that carbonate can be supplied and replenished simultaneously to a wide range of the electrolyte matrix, and the carbonate can be replenished and supplied even after stacking fuel cells. To obtain an electrolyte replenishing device for a carbonate fuel cell.

[0023]

According to the invention of claim 1, there is provided a carbonate bath for accommodating a stack constituted by stacking a unit cell and a separator and temporarily storing a carbonate to be supplied to the electrolyte matrix. And a carbonate supply / discharge pipe for supplying and discharging the carbonate stored in the carbonate bath.

According to a second aspect of the present invention, in the first aspect of the invention, a carbonate supply container for storing the carbonate supplied to the carbonate bath, a carbonate bath, a carbonate supply / discharge pipe, and a carbonate supply container. Is additionally provided.

According to a third aspect of the present invention, in the second aspect of the present invention, a supply means for supplying carbonate from the carbonate supply container to the carbonate bath is provided.

The invention of claim 4 is the first to third aspects of the invention.
In the invention, the carbonate bath is divided and provided for each unit of the stack.

According to the invention of claim 5, in the invention of claim 4, the carbonate bath provided for each unit is connected to a cascade by a connecting pipe, and the carbonate bath from the carbonate supply container is connected to the carbonate bath of the uppermost unit. The salt supply pipe is connected, and the carbonate discharge pipe to the carbonate supply container is connected to the carbonate bath of the lowermost unit.

[0028]

According to the first aspect of the invention, the stack is constructed by stacking the unit cells and the separator so that the end faces of the periphery of the electrolyte matrix are exposed to the atmosphere outside the stack.
Store the stack in a carbonate bath. The carbonate bath may contain carbonate in advance, or the carbonate may be supplied from the carbonate supply / discharge pipe when the carbonate is replenished, and when the carbonate supply is completed, the carbonate bath may be supplied from the carbonate supply / discharge pipe. The residual carbonate is discharged. Thereby, the carbonate permeates from the exposed portion of the electrolyte matrix and is supplied to the electrolyte matrix, and further supplied to the anode electrode and the cathode electrode.

According to the invention of claim 2, in addition to the operation of the invention of claim 1, the carbonate stored in the carbonate supply container is heated by the heater to be in a liquid state, and the carbonate is supplied through the carbonate supply / discharge pipe. Supply to salt tub. When the carbonate supply is completed, the carbonate remaining in the carbonate bath is returned to the carbonate supply container via the carbonate supply / discharge pipe.

In the third aspect of the invention, in addition to the function of the second aspect of the invention, when the carbonate is supplied from the carbonate supply container to the carbonate bath, the carbonate is supplied while being adjusted by the supply means.

In the invention of claim 4, in addition to the effects of the inventions of claims 3 to 3, the carbonate is supplied to the carbonate bath provided separately for each unit of the stack. Therefore, carbonate can be replenished in a short time.

According to the invention of claim 5, in addition to the effect of the invention of claim 4, the carbonate bath provided for each unit is connected to the cascade by a connecting pipe, and carbonate is supplied to the carbonate bath of the uppermost unit. The carbonate from the carbonate supply container is supplied through the pipe, and then the carbonate is sequentially supplied to the carbonate bath of the lowermost unit through the connecting pipe. Return the carbonate from the carbonate bath of the unit to the carbonate supply container via the carbonate discharge pipe.

[0033]

EXAMPLES Examples of the present invention will be described. FIG. 1 is an explanatory diagram showing a first embodiment of the present invention. In the first embodiment, a stack 15 configured such that the end surface of the periphery of the electrolyte matrix is exposed to the atmosphere outside the stack is housed in a carbonate bath 22, and carbonate is supplied to the carbonate bath 22. It is designed to replenish the carbonate.

FIG. 1 schematically shows a state in which a molten carbonate fuel cell stack is housed in a molten salt bath 22. The stack 15 is formed by stacking a plurality of single cells, an upper current terminal plate 16 is provided on the upper portion of the stack 15, and a lower current terminal plate 17 is provided on the lower portion of the stack 15. That is, the unit cells that are electrically connected in series can output electric output to the outside by the upper current terminal plate 16 and the lower current terminal plate 17. On the upper part of the upper current terminal plate 16 and the lower part of the lower current terminal plate 17, an electric insulating material 18 having both electric insulation and heat insulation is provided. Then, the stack 15 and the electric insulating material 18 are housed between the tightening plates 20 with the tightening rods 19 keeping an interval. In this case, the stack 15 is tightened by pressing the expandable tightening bellows 21 from the top with gas sealed inside. The tightening rod 19, the tightening plate 20, and the tightening bellows 21 are collectively referred to as a tightening device, which is generally used in a molten carbonate fuel cell.

In the carbonate bath 22, the carbonate supply / discharge pipe 2
3, so that the molten carbonate can be supplied and discharged from the outside, the circumference of the carbonate bath 22 is covered with a heat insulating material 24, and the carbonate bath 22 can be maintained at a temperature equal to or higher than the melting temperature of the carbonate. ing. As described above, the present invention includes the carbonate bath 22 for housing the stack 15, and the stack 15 is assembled so that the electrolyte matrix 2 can absorb the molten carbonate. That is,
The stack 15 is assembled so that the end surface of the electrolyte matrix 2 is exposed at the end edge of the stack 15. Then, the stack 15 is stored in the carbonate bath 22, and in that state, the molten carbonate is filled in the carbonate bath 22. Then, the molten carbonate is absorbed from the end surface of the electrolyte matrix 2, permeates to the inside of the electrolyte matrix 2 with the passage of time, and spreads evenly over the whole. further,
Since the molten carbonate is also absorbed by the anode electrode 3 and the cathode electrode 4 which sandwich the electrolyte matrix 2 from both sides, the carbonate can be appropriately supplied to the unit cell 1.

Next, the procedure for supplying carbonate to the stack 15 will be described. First, the stack 15 stacked without being filled with carbonate is housed in the carbonate bath 22 and tightened with a tightening device to assemble a fuel cell. The carbonate bath 22 is filled with powdered carbonate, the carbonate bath 22 is covered with a heat insulating material 24, and a high temperature gas is flown through the fuel gas passage and the oxidant gas passage to raise the temperature of the entire stack 15. .

When the temperature of the stack 15 reaches the melting temperature of the carbonate, the carbonate powder in the carbonate bath 22 starts melting, and absorption of the molten carbonate starts from the end surface of the electrolyte matrix 2 around the periphery of the stack 15. To be done. The stack 15 is maintained at the melting temperature until the voltage of the stack 15 reaches a predetermined voltage, and when the predetermined voltage is reached, it is determined that an appropriate amount of carbonate has been supplied to each cell 1, and the molten carbonate is carbonated. The salt bath 22 is promptly discharged to end the carbonate supply.

Since the apparent volume of the powdered carbonate filled in the carbonate bath 22 is reduced when the carbonate bath 22 is dissolved, in consideration of this, the powder is filled higher than the height of the stack 15. Also,
The molten carbonate also flows into the gaps of the stack 15 which are difficult to fill with powder, so the filling is made higher than the height of the stack in consideration of the drop in the carbonate liquid level. Thereby, the cell 1 can be filled with the carbonate without filling the stack 15 with the carbonate in advance.

Next, the procedure for replenishing the carbonates lost during the power generation operation will be described. The carbonate bath 22 is filled with nitrogen gas, and the stack 15 is heated to about 640 ° C. in a nitrogen gas atmosphere.
Up to. Then, a predetermined amount of fuel gas composed of 80% hydrogen and 20% carbon dioxide gas was supplied to the anode gas flow channel, and a predetermined amount of oxidant gas composed of 70% air and 30% carbon dioxide gas was supplied to the cathode gas flow channel. , Connect the fuel cell externally from the current terminal board to continue power generation.

In this case, the battery voltage during power generation gradually decreases with the lapse of time due to the loss of carbonate, so when the battery voltage falls below a predetermined voltage, it is determined that the carbonate is lost and power generation is interrupted. Then, open the fuel cell,
The carbonate bath 22 is quickly filled with molten carbonate. In this state, the temperature of the stack 15 remains at about 650 ° C. at the time of power generation, and the carbonate filled in the carbonate bath 22 is supplied to the entire unit cell 1 through the electrolyte matrix 2. When replenishing the carbonate, the open circuit voltage is monitored, and when the open circuit voltage exceeds a predetermined value, it is determined that the replenishment of the carbonate is completed, and the carbonate is quickly discharged from the carbonate bath 22. Then, the power generation is restarted after waiting for the battery voltage to stabilize. By supplementing with this carbonate, the battery performance can be restored to about 98% of the initial battery performance.

According to this first embodiment, the stack 15
The conventional shape can be used as it is. That is, it is not necessary to change the structure of the stack 15, and the carbonate can be quickly supplied and replenished to the unit cell 1 from a wide range of the electrolyte matrix 2.

Next, a second embodiment of the present invention will be described.
FIG. 2 is an explanatory view showing the second embodiment of the present invention. The second embodiment is different from the first embodiment in that the carbonate bath 22
Supply container 25 for storing carbonate supplied to
Further, a carbonate bath 22, a carbonate supply / discharge pipe 23, and a heater 26 for heating the carbonate supply container 22 are additionally provided. That is, the carbonate stored in the carbonate supply container 25 is heated by the heater 26 into a liquid state and supplied to the carbonate bath 22 through the carbonate supply / discharge pipe 23. When the supply of carbonate is completed, the carbonate remaining in the carbonate bath 22 is returned to the carbonate supply container 25 via the carbonate supply / discharge pipe 23.

FIG. 2 schematically shows a molten carbonate fuel cell provided with a carbonate supply container 25. Like the stack 15 shown in FIG. 1, the stack 15 is tightened by a tightening device and covered with the heat insulating material 24, but they are omitted from the drawing for simplification of description. Although not shown in FIG. 2, the carbonate bath 22 for accommodating the stack 15 is arranged so that its bottom portion is clamped together with the stack 15 by a clamping device as shown in FIG. In addition, the molten carbonate 2
A carbonate supply container 25 for storing molten carbonate 27 is connected via a carbonate supply / discharge pipe 23 for supplying / discharging 7. A heater 26 for heating is provided in the carbonate bath 22, the carbonate supply / discharge pipe 23, and the carbonate supply container 25 so that the carbonate can be maintained at a temperature equal to or higher than the melting temperature.

In FIG. 2, the molten carbonate 27 is a carbonate bath 2
2 and the carbonate supply container 25 are both half-filled, the carbonate supply container 25 can be moved up and down, and depending on the vertical position of the carbonate supply container 25,
The carbonate liquid level in the carbonate bath 22 is adjusted. That is, by raising the carbonate supply container 25 from the position shown in FIG. 2, the molten carbonate 27 in the carbonate supply container 25 is removed from the carbonate bath 22.
The molten carbonate 27 in the carbonate supply container 25 can be returned to the carbonate supply container 25 by lowering the position of the carbonate container 25. Further, the carbonate supply / discharge pipe 23 is made to be bendable.

Next, the procedure for supplying the molten carbonate 27 in the second embodiment will be described. When the battery voltage falls below a predetermined voltage, it is determined that the carbonate inside the battery has been lost, power generation is interrupted, and carbonate replenishment is started. First, the carbonate supply container 25 is moved to a position lower than the bottom of the carbonate bath 22, and the carbonate powder is filled in the carbonate supply container 25. Then, the heater 26 is energized to melt the carbonate in the carbonate supply container 25 and the carbonate supply / discharge pipe 23, and then the carbonate supply container 25 is quickly moved upward,
The molten carbonate 27 is sent to the carbonate bath 22. This allows
Molten carbonate 27 is supplied to the entire unit cell 1 from the end surface of the electrolyte matrix 2 exposed around the stack 15.
When the molten carbonate 27 is replenished, the open circuit voltage is monitored, and when the open circuit voltage exceeds a predetermined value, it is determined that the replenishment of the molten carbonate 27 has been completed, and the replenishment is ended. That is, the position of the carbonate supply container 25 is lowered and the molten carbonate 27 is quickly discharged from the carbonate bath 22.

According to the second embodiment, in addition to the effect of the first embodiment, the molten carbonate 27 liquidized by the heater 26 is supplied to the carbonate bath 22, so that the molten carbonate 27
Can be quickly replenished to the unit cell 1. This replenishment method can also be applied to the case where carbonate is supplied before the start of power generation operation of the fuel cell.

FIG. 3 shows an explanatory view of the third embodiment of the present invention. The third embodiment is different from the second embodiment shown in FIG. 2 in that a supply means for supplying the molten carbonate 27 from the carbonate supply container 25 to the carbonate bath 22 is additionally provided. Is. As the supply means, the molten carbonate 27 is supplied from the carbonate supply container 25 to the carbonate bath 22 by the gas pressure from the gas supply pipe 28.

That is, as shown in FIG. 3, the carbonate supply container 25 is fixed at a position lower than the bottom of the carbonate bath 22. When the molten carbonate 27 is supplied from the carbonate supply container 25 to the carbonate bath 22, the gas supply pipe 28
More pressurized gas is supplied to pressurize the inside of the carbonate supply container 25 to pump the molten carbonate 27. When it is desired to return the molten carbonate 27 from the carbonate bath 22 to the carbonate supply container 25, the gas pressure in the carbonate supply container 25 is lowered.

According to the third embodiment, in addition to the second embodiment, the carbonate supply container 25 remains fixed and the carbonate bath 2 is used.
Since the molten carbonate 27 can be supplied to 2, the operation becomes simple. Further, this replenishing method has a simple structure because the molten carbonate 27 is replenished and supplied by gas pressure, and since there is no driving part, the reliability is high for a long period of time.

Next, FIG. 4 shows a fourth embodiment of the present invention. The fourth embodiment is different from the first to third embodiments in that the carbonate bath 22 is provided in the unit 2 of the stack 15.
It is provided separately for every 9. Carbonate is supplied to a unit carbonate bath 30 provided separately for each unit 29 of the stack 15.

That is, the stack 15 is divided into a plurality of units 29, and unit carbonate baths 30 are provided therein. The method for supplying and replenishing the carbonate is the same as in the first to third embodiments, but in the case of the fourth embodiment, the carbonate is supplied to the individual unit carbonate baths 30 in a shorter time. Since it can be filled, the time of immersion in the unit carbonate baths 30 of the upper and lower single cells in the unit 29 can be made more uniform. Therefore, it is possible to reduce the solid difference in the carbonate supplement amount, that is, the difference in the carbonate supplement amount for each single cell.

FIG. 5 shows a fifth embodiment of the present invention. The fifth embodiment differs from the fourth embodiment in that a unit carbonate bath 30 provided for each unit 29 is connected to a cascade by a connecting pipe 31, and a carbonate is added to the unit carbonate bath 30a of the uppermost unit 29a. The carbonate supply pipe 23A from the supply container 25 is connected, and the carbonate discharge pipe 23B to the carbonate supply container is connected to the unit carbonate bath 30c of the lowermost unit 29c. And unit 29
The unit carbonate bath 30 provided for each unit is connected to the cascade by the connection pipe 31, and the carbonate from the carbonate supply container 25 is supplied to the unit carbonate bath 30a of the uppermost unit 29a via the carbonate supply pipe 23A. Connection pipe 31
Carbon dioxide is sequentially supplied to the unit carbonate bath 30c of the lowermost unit 29c via a and 31b, and when the carbonate replenishment is completed, the carbonate discharge pipe from the carbonate bath 30c of the lowermost unit 29c. The carbonate is returned to the carbonate supply container 25 via 23B.

That is, in this fifth embodiment, the unit carbonate baths 30 which are vertically adjacent to each other are connected to each other by the connecting pipe 3.
1, and carbonates are sequentially supplied from the uppermost unit carbonate bath 30a to the lowermost unit carbonate bath 30c. In this way, the unit carbonate bath 30
The amount of carbonate supplied to the whole can be made smaller than the amount of carbonate supplied to the undivided carbonate bath 22, which is effective for storing carbonate.

In the above-mentioned first to fifth embodiments, the operation of the fuel cell is interrupted when the carbonate is replenished, but it is also possible to continue the power generation of the fuel cell.

[0055]

As described above, according to the present invention, since the carbonate can be supplied to the unit cell after the fuel cells are stacked, the stacking height of the cell reaction part and the manifold part due to the disappearance of the electrolyte sheet. It is possible to avoid the deviation of the fuel cell and the oxidation of the anode electrode due to the inability to supply gas when the temperature of the fuel cell is raised.

Further, by operating the fuel cell, the lost carbonate can be replenished to the unit cell. Since the molten carbonate covers the entire stack during the replenishment, the end surface of the electrolyte matrix serving as the carbonate supply port is widened, and the carbonate replenishment can be performed efficiently.
Also, since the volume of carbonate to fill the carbonate bath is large,
It becomes possible to replenish the carbonate uniformly in a short time.

Further, since the structure is simple and the conventional molten carbonate fuel cell can be used as it is only by providing a carbonate bath, it can be applied to any molten carbonate fuel cell. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a fourth embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a fifth embodiment of the present invention.

FIG. 6 is an exploded perspective view showing a unit cell of a molten carbonate fuel cell and a single cell in which one separator is stacked.

7 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single cell 2 Electrolyte matrix 3 Anode electrode 4 Cathode electrode 5 Separator 6 Interconnector 7 Anode edge plate 8 Cathode edge plate 9 Anode current collector plate 10 Cathode current collector plate 11 Fuel gas 11A Fuel gas flow channel 12 Oxidizing gas 12A Oxidizing agent Gas flow path 13 Manifold ring 14 Whit seal 15 Stack 16 Upper current terminal plate 17 Lower current terminal plate 18 Electrical insulating material 19 Tightening rod 20 Tightening plate 21 Tightening bellows 22 Carbonate bath 23 Carbonate supply and discharge pipe 23A Carbonate Supply pipe 23B Carbonate discharge pipe 24 Heat insulating material 25 Carbonate supply container 26 Heater 27 Molten carbonate 28 Gas supply pipe 29 Unit 30 Unit carbonate bath tub 31 Connection pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Seta 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Office (72) Inventor Setsuo Inuzuka 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa (2) Inventor Seigo Watanabe 2-4, Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Stock company, Toshiba Keihin office

Claims (5)

[Claims] 1. A flat cell unit formed by sandwiching an electrolyte matrix between an anode electrode and a cathode electrode, and a gas flow for introducing a fuel gas to the anode electrode of the unit cell and an oxidant gas to the cathode electrode. A stack is formed by alternately stacking separators that form a path and electrically connects adjacent unit cells to each other, and the electrolyte is so formed that the end face of the peripheral edge of the electrolyte matrix is exposed to the atmosphere outside the stack. In an electrolyte replenishing device for a molten carbonate fuel cell in which a matrix is mounted by sandwiching it between an anode edge plate and a cathode edge plate of the separator, for temporarily storing the carbonate to house the stack and supply and replenish the electrolyte matrix. Carbonate bath and a carbonate for supplying and discharging the carbonate stored in the carbonate bath An electrolyte replenishing device for a molten carbonate fuel cell, comprising a salt supply / discharge pipe. 2. A carbonate supply container for storing the carbonate to be supplied to the carbonate bath, a heater for heating the carbonate bath, the carbonate supply / discharge pipe, and the carbonate supply container. 3. The method according to claim 1, further comprising:
An electrolyte replenishing device for a molten carbonate fuel cell according to item 1. 3. An electrolyte replenishing device for a molten carbonate fuel cell according to claim 2, further comprising a supply means for supplying the carbonate from the carbonate supply container to the carbonate bath. . 4. The electrolyte replenishing device for a molten carbonate fuel cell according to claim 1, wherein the carbonate bath is provided separately for each unit of the stack. 5. A carbonate bath provided for each unit is connected to a cascade by connecting pipes, and a carbonate supply pipe from the carbonate supply container is connected to a carbonate bath of the uppermost unit, and a carbonate bath of the lowermost unit is connected. The electrolyte replenishing device for a molten carbonate fuel cell according to claim 4, wherein a carbonate discharge pipe to the carbonate supply container is connected to a carbonate bath of the unit.