JPH088110B2 - Molten carbonate fuel cell electrolyte replenishing method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing and replenishing electrolytes in a fuel cell, and particularly to a molten carbonate fuel having an electrolyte replenishing method and a replenishing function suitable for maintaining stable cell performance for a long period of time. Regarding batteries.

[0002]

2. Description of the Related Art In a fuel cell, a pair of electrodes are arranged on both sides of an electrolyte plate, and a separator having a flow passage for an oxidant gas and a fuel gas is arranged outside the electrodes to form a unit cell. are doing. In order to increase the capacity of a fuel cell for electric power, a large stacked cell with a large electrode area and a large number of unit cells is used as a standard stack. A power plant will be built. One of the biggest problems in the operation of a fuel cell power plant is the movement of the electrolyte inside the unit cell or the whole laminated cell,
There is a problem that the electrolyte becomes insufficient due to the wear of the electrolyte due to the corrosion of the separator and the like, the evaporation of the electrolyte itself, and the scattering to the outside of the battery, and the battery performance gradually decreases.
As methods for coping with such problems, various methods have been proposed so far for storing an electrolyte inside a battery and replenishing the electrolyte from the outside.

Inventions relating to a method of storing an electrolyte inside a battery include, for example, JP-A-53-30747, JP-A-56-54770, and JP-A-58-100368.
No. 58-138268, 58-165.
258, JP-A-58-165262, JP-A-58-
There are various publications such as 166653. Examples of the invention relating to the method of replenishing the electrolyte from the outside of the battery include, for example, JP-A-57-55071, JP-A-57-197756, JP-A-58-42179, and JP-A-58-61574.
JP-A-58-61575, JP-A-58-144760
No. 58-158870 and 58-161.
There are various publications such as 267.

[0004]

Various inventions relating to a method for storing an electrolyte inside a battery have been disclosed as described above. The electrolyte storage portion is a wet seal portion, an electrode substrate portion, or a reaction gas flow passage portion. The electrolyte storage capacity is also limited because it is a limited area such as the above, and it is desirable to make the thickness of the unit battery as thin as possible. The durability time required for the battery body of a fuel cell power plant is generally said to be about 40,000 hours, and it is difficult to maintain stable battery performance for a long period of time. In addition, since the electrolyte storage unit is in communication with the electrodes, which are the battery constituent members, and the electrolyte plate, the storage electrolyte is also melted into a liquid state during the operation of the power generation plant, which causes the electrode to become too wet with the electrolyte. On the contrary, there is a possibility that the battery may not fully exhibit its performance.

Although various inventions relating to a method for replenishing an electrolyte from the outside of the battery have been disclosed as described above, it is somewhat difficult to say that the definitive version of the electrolyte replenishing method actually applicable to the battery body on a practical basis is used. There are many things I have to say. An object of the present invention is to solve the problems of the prior art, prevent deterioration of battery performance due to lack of electrolyte, and maintain molten battery performance suitable for a long period of time. An object of the present invention is to provide an electrolyte replenishing method and apparatus for a salt fuel cell, and a power generation plant including the same.

[0006]

In order to achieve the above object, in the present invention, a pair of electrodes consisting of a fuel electrode and an oxidant electrode is provided.
Place the electrolyte plate that holds the electrolyte between the
Provided with fuel gas and oxidant gas flow paths outside these electrodes
It is a laminated body of unit batteries in which a separator is placed,
And a method for replenishing an electrolyte of a molten carbonate fuel cell using a mixture of alkali metal carbonates or a eutectic salt as an electrolyte , which has a melting point higher than that of the electrolyte and has a composition of
Different alkali metal carbonates alone or as a mixture of two or more
In a container for accommodating the battery in the state of solid phase or solid-liquid mixed crystal phase
Of the alkali metal carbonate in the solid phase or the solid-liquid mixed crystal phase is melted at the time of replenishing the electrolyte.
The electrolyte is mixed and supplied to the battery as an electrolyte having a predetermined composition . In the supply method, it
The separated and stored alkali metal carbonates, alone or in a mixture of two or more, contain at least one or more alkaline earth metal compounds such as carbonates, hydroxides or oxides. May be.

In order to achieve the above object, the present invention provides:
An electrolyte is kept between a pair of electrodes consisting of a fuel electrode and an oxidizer electrode.
Place the electrolyte plate you have on the outside of each electrode.
A separator with flow paths for fuel gas and oxidant gas
In a molten carbonate fuel cell, which is a laminated body of unit cells and has a mixture of alkali metal carbonates or a eutectic salt as an electrolyte, the melting point is higher than the melting point of the electrolyte.
And alkali metal carbonates having different compositions , either alone or 2
A storage unit for separating and storing a mixture of one or more kinds in a solid phase or a solid-liquid mixed crystal phase in a container for accommodating the battery is provided.
In a fixed case, a communication part is provided between the separately provided storage parts, and one or both of the storage parts is provided with a heating mechanism, and one of the storage parts is provided with an electrolyte supply hole or an electrolyte supply passage.
The electrolyte plates and / or the electrodes of the unit cell stack are communicated with each other via the channels . Further, in the present invention, an electric charge is applied between a pair of electrodes composed of a fuel electrode and an oxidizer electrode.
Place the electrolyte plate that holds the disintegration, and
Separator equipped with fuel gas and oxidant gas flow channels outside
A stack of unit cells formed by placing over data, and Al
Melting with Potassium Metal Carbonate Mixture or Eutectic Salt as Electrolyte
In front of the carbonate fuel cell stack body, a steam reformer or
Is the melting point of the electrolyte in a molten carbonate fuel cell power plant equipped with a fuel production device such as a coal gasifier .
A storage part of an alkali metal carbonate having a higher melting point and a different composition is placed in a predetermined place in the container for storing the battery.
The storage parts are provided separately, and a communication part is provided between the storage parts, and one of the storage parts is provided with an electrolyte replenishment hole and an electrolyte replenishment communication hole.
The fuel production apparatus (hereinafter referred to as "fuel processor") is connected to the electrolyte plate and / or the electrode of the unit cell stack through a passage.
The hot gas generated from the service "hereinafter) is introduced into at least one of the reservoir portion, a mechanism for heating the stored at least one of an alkali metal carbonate to a temperature above the melting point,
One melt of the alkali metal carbonate is merged with the other alkali metal carbonate stored in the adjacent storage unit through the communication unit, melted and mixed to prepare an electrolyte having a predetermined composition.
The electrolyte is supplied from the storage portion through the electrolyte supply hole to the electrolyte plate and / or the electrode of the unit battery laminate from the electrolyte passage .

That is, the present invention separates and stores the alkali metal carbonate in the solid phase or the solid-liquid mixed crystal phase, mixes it when replenishing the electrolyte, and replenishes it to the battery stack as the liquid phase. The point of the present invention is that in a molten carbonate fuel cell using a mixture of alkali metal carbonates or a eutectic salt as an electrolyte, one or more alkali metal carbonates having a melting point higher than that of the electrolyte are used. The mixture is separated and stored in the solid phase or solid-liquid mixed crystal phase, and the battery performance is deteriorated due to lack of electrolyte. The purpose of the present invention is to obtain a molten carbonate fuel cell capable of maintaining stable cell performance for a long period of time by converting a metal carbonate into a liquid phase state, mixing it and supplying it to a cell stack.

A feature of the present invention is that an alkali metal carbonate having a melting point higher than that of the electrolyte, or a mixture of two or more kinds thereof, is separated and stored in a solid phase or a solid-liquid mixed crystal phase. As a result, the operating temperature of the battery stack can be maintained below the temperature at which the alkali metal carbonate alone or a mixture of two or more thereof is completely melted. It is possible to keep the alkali metal carbonate alone or a mixture of two or more kinds in the state of solid phase or solid-liquid mixed crystal phase, which causes the electrode to get too wet with the electrolyte, and on the contrary, sufficiently develops the battery performance. There is nothing to prevent.

[0010]

The present invention will be described in more detail. By heating one or both of the separated and stored alkali metal carbonates or a mixture of two or more thereof, the melting of the alkali metal carbonates proceeds, When one melt of the separated alkali metal carbonate comes into contact with the other alkali metal carbonate, the melting point is lowered, and the melting proceeds through the state of a solid-liquid mixed crystal phase. Are mixed homogeneously to form an electrolyte having a predetermined composition, and are completely replenished to the battery stack in a liquid phase. The storage part of the alkali metal carbonate is not limited to the limited parts such as the wet seal part, the electrode substrate part or the reaction gas flow passage part disclosed in the prior art, and a plurality of unit batteries are laminated. A gas header portion provided at both (upper and lower) ends of a battery block or a battery stack, and an alkali metal carbonate storage portion provided outside the battery block or battery stack via an electrolyte replenishing passage portion. Good.

The main alkali metal carbonates applicable to the present invention are lithium carbonate (Li ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ) and potassium carbonate (K ₂ CO ₃ ).
The alkali metal carbonate alone or a mixture of two or more kinds is stored separately in a predetermined storage unit. A communication part is provided between the predetermined separately provided storage parts, and one of the storage parts is connected to a portion to which electrolyte should be replenished. One or both of the separated and stored alkali metal carbonates or a mixture of two or more thereof are heated and melted, and one melt of the alkali metal carbonates passes through the communicating portion and the other alkali metal carbonates. The melting point decreases due to merging and contact, and the melting proceeds through the state of a solid-liquid mixed crystal phase, both alkali metal carbonates are mixed homogeneously, and an electrolyte of a predetermined composition is formed, and the state of completely liquid phase Is replenished to the part of the battery stack where the electrolyte should be replenished.

The electrolyte applied to the present invention is typically one having a predetermined mixed composition of alkali metal carbonates. In the present invention, the alkali metal carbonates separated and stored are used alone or in combination of two or more. It is also possible to include an alkaline earth metal compound in one or both of the mixtures.
The content is 25 mol% or less of the alkali metal carbonate, preferably 5 to 10 mol%. The alkaline earth metal is not particularly limited, and magnesium (M
g), calcium (Ca), strontium (Sr), barium (Ba) and the like, and as the alkaline earth metal compound, carbonates, hydroxides or oxides and mixtures thereof are desirable.

In the present invention, the heat source for heating and melting one or both of the alkali metal carbonates stored separately and a mixture of two or more thereof is not particularly limited, but for example, an electric heater. Is contained in one or both of the storage parts, and one or both of the storage parts is heated and melted at the time of replenishing the electrolyte so that the alkali metal carbonate in the solid phase or the solid-liquid mixed crystal phase is in the liquid phase state. Can be converted to, mixed and supplied to the battery stack. Further, a high temperature gas is supplied to one or both of the storage units, and one or both of the storage units is heated and melted by its sensible heat to obtain the alkali metal carbonate in the solid phase or solid-liquid mixed crystal phase state. It can be converted into a liquid phase state, mixed, and supplied to the battery stack. As the high temperature gas, various combustion gases and combustion exhaust gas are generally used. However, in the fuel cell power plant according to the present invention, a steam reformer using natural gas (NG), liquefied petroleum gas (LPG) or the like as a raw fuel or coal using coal as a raw fuel is provided in the preceding stage of the fuel cell stack body. Since a fuel processor such as a gasification furnace is provided,
Using the reformed gas from the reformer or the fuel exhaust gas or the coal gasification gas from the coal gasification furnace as the high temperature gas,
It is possible to construct a molten carbonate fuel cell power generation system characterized by heating the storage part of the alkali metal carbonate by the sensible heat.

An aspect of the system will be described below.
In a fuel cell power generation plant having a steam reformer as a fuel processor in the preceding stage of a battery stack body in which a plurality of battery blocks formed by stacking a plurality of unit cells are stacked, each of gas headers arranged in the battery block In the upper header of, for example, Li ₂ CO ₃ and K ₂ CO
A predetermined amount of ₃ is stored separately. During steady operation of the fuel cell power plant, the temperature of the alkali metal carbonate storage part is maintained at a temperature equal to or lower than its melting point. A battery performance detector for detecting the power generation performance of the battery block, and a detection signal of the battery performance detector for heating an alkali metal carbonate storage unit disposed in an upper header of the battery block. A heating command device for operating the alkali metal carbonate storage unit is provided.

Although the power generation performance of the battery block decreases as the fuel cell power plant operates for a long time, the battery performance detector detects an arbitrarily set index value representing the battery performance. In step, the detection signal of the battery performance detector is transmitted to the alkali metal carbonate storage unit heating command device. Then, the command device is activated to heat the storage part of the alkali metal carbonate. Specifically, the reformed gas or combustion exhaust gas from the steam reformer is higher than that during steady operation, and at least the melting point of one of the alkali metal carbonates stored in the storage section. The temperature of the alkali metal carbonate is adjusted to a higher temperature and supplied to the storage part of the alkali metal carbonate of the battery block, and the sensible heat of the storage part of the alkali metal carbonate heats the storage part of the alkali metal carbonate. The alkali metal carbonate in the solid phase or the solid-liquid mixed crystal phase can be melted, converted into the liquid phase, mixed and supplied to the battery stack.

In order to adjust the temperature of the reformed gas or fuel exhaust gas from the steam reformer, the feed amount of raw fuel such as NG or LPG supplied to the steam reformer is reduced,
It can be achieved by adjusting the amount of air supplied to the heating furnace of the steam reformer, adjusting the amount of air, or supplying a predetermined amount of auxiliary fuel to the heating furnace. Further, the heater is operated in accordance with a command from the alkali metal carbonate storage unit heating command device, and the reformed gas or combustion exhaust gas from the steam reformer supplied to the battery block in the steady operation state is in the steady operation. It is also possible to adjust the temperature to a higher temperature and at least higher than the melting point of one of the carbonates of the alkali metal carbonates stored in the storage section. The index value indicating the battery performance detected by the battery performance detector includes, for example, the battery voltage of the battery block, the open circuit voltage, the internal resistance, and N _{2 in} the fuel gas for detecting the gas cross of the reaction gas. Examples of the concentration include the O ₂ concentration and the H ₂ concentration in the oxidizing gas.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these. Example 1 FIG. 1 shows that an electrolyte plate 3-1 holding an electrolyte is arranged between a pair of electrodes consisting of a fuel electrode 1-1 and an oxidizer electrode 2-1 and fuel gas is provided outside each electrode. And a unit cell stack 5 formed by stacking n unit cells in which a separator 4-1 having an oxidant gas flow path is disposed, a molten carbonate fuel cell having electrolyte storage and replenishment functions. Is one example showing. An upper end plate 6, a lower end plate 7, a lower gas header 8 and a lower gas header 9 of a unit battery stack 5 formed by stacking n unit batteries are integrated with each other through sealing materials 10 and 11. As shown in FIG. 2 showing the AA cross section of FIG. 1, the gas headers 8 and 9 are respectively the fuel gas supply unit 12 and the fuel gas discharge unit 1.
3 has an oxidant gas supply unit 14 and an oxidant gas discharge unit 15, and the fuel gas is a fuel gas supply pipe 16 shown in FIG.
After passing the fuel electrodes 1-1 to 1-n of each unit cell through the fuel gas supply hole 17 provided in the fuel gas supply unit 12, the fuel gas discharge hole 18 provided in the fuel gas discharge unit 13 is provided. And is discharged from the fuel gas discharge pipe 19.

Although the oxidant gas supply pipe and the exhaust pipe are omitted in FIG. 1, the oxidant gas is provided in the oxidant gas supply unit 14 from the oxidant gas supply pipe, like the fuel gas. After flowing the oxidant gas electrodes 2-1 to 2-n of each unit battery from the oxidant gas supply hole 20, the oxidant gas discharge pipe is passed through the oxidant gas discharge hole 21 provided in the oxidant gas discharge part 15. More discharged. In this embodiment shown in FIGS. 1 and 2,
An electrolyte storage and replenishment mechanism is provided in a hollow portion in the upper gas header 8 disposed above the unit cell stack 5 in which fuel gas and oxidant gas do not flow. That is,
One of the alkali metal carbonates having a melting point higher than that of the electrolyte held by the electrolyte plate 3 and in a solid phase or solid-liquid mixed crystal phase, or a mixture of two or more kinds, is stored in one electrolyte storage section 22. The other alkali metal carbonates having different compositions are stored alone or in a mixture of two or more kinds in the other electrolyte storage section 23.

As shown in FIG. 2, in this embodiment, the electrolyte storage sections 22 and 23 are each divided into four sections.
A communication part 24 is provided between the electrolyte storage part 22 and the electrolyte storage part 23 which are separately provided as described above, and the other electrolyte storage part 23 has a predetermined composition of the unit cell stack 5. Electrolyte replenishing holes 25 that communicate with the parts to be replenished with the electrolyte are respectively provided. Here, the composition and storage amount of the alkali metal carbonate stored alone or a mixture of two or more kinds in the electrolyte storage sections 22 and 23 will be described. The electrolyte retained on the electrolyte plate 3 is a eutectic composition of Li ₂ CO ₃ and K ₂ CO ₃ (62: 3).
(8, molar ratio), and the number of stacked unit cells was 50 cells. The electrolyte plate 3 arranged in each unit battery is 1.0 m square and has a thickness of 1.5 mm. 1.69 of Li ₂ CO ₃ is stored in the electrolyte storage unit 22 divided into four parts.
1 kg of K ₂ CO ₃ was stored in each of the other four divided electrolyte storage sections 23. The melting point of Li ₂ CO ₃ is 726 ° C., and K ₂ CO ₃
Has a melting point of 899 ° C.
The electrolyte storage unit 2 is operated during steady operation at a temperature of 0 ° C.
2 and 23 stored Li ₂ CO ₃ , K ₂ CO ₃
Exists in the solid state.

When the battery performance deteriorates due to the lack of electrolyte and the index value indicating the battery performance is reached, the melting point of the alkali metal carbonate stored in the electrolyte storage unit 22 and / or 23 is stored. Heat to above. In this embodiment,
Electric heater 2 built in the bottom of the electrolyte storage unit 22
6 operates the electrolyte reservoir 22 is heated to above the melting point of Li ₂ CO ₃ which is stored in the reservoir section, Li ₂ CO ₃
To a liquid state. The melted Li ₂ CO ₃ merges with the K ₂ CO ₃ stored in the other electrolyte storage section 23 through the communication section 24 and comes into contact with the K ₂ CO ₃ to lower the melting point, and the melting thereof passes through a solid-liquid mixed crystal phase state. As they proceed, both alkali metal carbonates mix with each other to form a predetermined electrolyte composition. The molten electrolyte thus formed reaches the electrolyte plate 3 arranged in each unit battery from the electrolyte replenishment passage 27 through the electrolyte replenishment hole 25 provided in the electrolyte storage section 23, and permeates into the pores. , Impregnated. It is also possible to divide the electric heater 26 built in the bottom portion of the electrolyte storage unit 22 and replenish the electrolyte in four steps for each section.

Example 2 In FIG. 3, an electrolyte plate 3-1 holding an electrolyte is arranged between a pair of electrodes consisting of a fuel electrode 1-1 and an oxidizer electrode 2-1 and the outside of each electrode is arranged. Current collector 28-
1, 28-1 'and a unit cell stack 5 formed by stacking a plurality of unit cells in each of which a separator 4-1 provided with fuel gas and oxidant gas flow paths is disposed,
FIG. 3 is a schematic view of a multi-block laminated battery stack in which two blocks are laminated via an intermediate gas header 29, which is one example showing a molten carbonate fuel cell having electrolyte storage and replenishment functions. A fuel gas supply pipe 16 and a fuel gas discharge pipe are respectively provided in the upper gas header 8 disposed above the upper unit cell stack 5-1 and the lower gas header 9 disposed below the lower unit battery stack 5-2. 19, the fuel gas is supplied from the fuel gas supply pipes 16 of the upper gas header 8 and the lower gas header 9 to the unit cells of the upper unit cell stack 5-1 and the lower unit cell stack 5-2. It is supplied and discharged from the respective fuel gas discharge pipes 19 of the upper gas header 8 and the lower gas header 9.

On the other hand, the intermediate gas header 29 is provided with an oxidant gas supply pipe 30 (not shown in FIG. 3) and an oxidant gas discharge pipe 31, respectively. It is supplied to each unit cell of the unit cell stack 5-1 and the lower unit cell stack 5-2, and is discharged from the oxidant gas discharge pipe 31. In the present embodiment, the electrolyte replenishment to the upper unit cell stack 5-1 is performed from the upper gas header 8, and the electrolyte replenishment to the lower unit cell stack 5-2 is performed from the intermediate gas header 29. 1
It is possible to carry out by the method similar to.

FIG. 4 shows the internal structure of the intermediate gas header 29. An electrolyte storage and replenishment mechanism is provided in the intermediate gas header 29 arranged above the lower unit cell stack 5-2. That is, one or a mixture of two or more of alkali metal or alkaline earth metal compounds having a melting point higher than that of the electrolyte retained on the electrolyte plate 3 and in a solid phase or solid-liquid mixed crystal phase is used. Of the other alkali metal or alkaline earth metal compound having a different composition, or a mixture of two or more thereof is stored in the other electrolyte storage part 23. FIG.
As shown in, the electrolyte storage sections 22 and 23 are each divided into four sections. A communication part 24 is provided between the electrolyte storage parts 22 and 23 separately provided as described above, and a predetermined part of the lower unit cell stack 5-2 is provided in the other electrolyte storage part 23. Electrolyte replenishment holes 25 are provided to communicate with the parts of the composition to be replenished with electrolyte.

In this embodiment, the standard composition of the electrolyte held on the electrolyte plate 3 is Li ₂ CO ₃ , K ₂ CO ₃ and S.
Mixture of rCO ₃ (58.9: 36.1: 5, molar ratio)
Therefore, the number of stacked unit cells of each of the upper unit battery stack 5-1 and the lower unit battery stack 5-2 was set to 25 cells. The electrolyte plate 3 arranged in each unit battery is 1.0 m square and has a thickness of 1.5 mm. In the electrolyte storage portion 22 divided into four, 0.8 of Li ₂ CO ₃ is stored.
0 kg of each is stored, and 0.92 kg of K ₂ CO ₃ and SrCO ₃ are stored in the other electrolyte storage section 23 divided into four.
0.135 kg of each was stored. The battery performance deteriorates due to the lack of the electrolyte, and Li stored in the electrolyte storage unit 22 at the stage when the index value representing the battery performance is reached.
₂ Heat above the melting point of CO ₃ (726 ° C.).

In the present embodiment, as shown in FIG. 4, from the oxidizing gas supply pipe 30, the first electrolyte storage portion 22, the upper opening of the first communication hole 24, the first electrolyte storage portion 23, An opening 33 cut out in the upper part of the partition wall 32 of the first electrolyte storage part 23 and the second electrolyte storage part 22, the second electrolyte storage part 22, the second communication hole 24, the second electrolyte storage part. 23
Also, the oxidant gas supplied from the oxidant gas supply hole 20 to each unit cell through the opening 35 cut out in the upper part of the partition wall 34 of the second electrolyte storage unit 23 and the oxidant gas supply unit 14 is supplied to Li ₂ Li ₂ CO ₃ is converted into a liquid phase state by heating and supplying it above the melting point of CO ₃ (726 ° C.).
The melted Li ₂ CO ₃ is stored in the other electrolyte storage section 23 through the communication section 24, and K ₂ CO ₃ and SrCO ₃ are stored.
By merging into and contacting the mixture of
The melting proceeds through a state of a solid-liquid mixed crystal phase, and Li ₂ CO
₃ , K ₂ CO ₃ and SrCO ₃ are mixed to give a predetermined electrolyte composition. The molten electrolyte thus formed reaches the electrolyte plate 3 arranged in each unit battery through the electrolyte replenishing hole 25 provided in the electrolyte storage unit 23, and permeates and is impregnated into the pores.

A similar electrolyte storage and replenishment mechanism is also provided in the upper gas header 3 disposed above the upper unit battery stack 5-1 and the upper unit battery stack 5- is formed in the same manner. 1 is supplied with electrolyte. In this embodiment, the electrolyte replenishment can be controlled and implemented in block units.
Even in the case of a large-capacity stack in which a plurality of tens of unit cell stacks 5 are stacked via the intermediate gas header 29, it is possible to replenish the electrolyte for each block or all blocks simultaneously.

Embodiment 3 FIG. 5 is a schematic view of a molten carbonate fuel power generation system using a steam reformer as a fuel processor.
Uses the structure shown in FIGS. 3 and 4. In a fuel cell power plant in which a steam reformer 37 is provided as a fuel processor before a cell stack 36 in which a plurality of unit cell stacks 5 shown in FIG. In the upper gas header 8 or the intermediate gas header 29 provided in the unit cell stack 5, for example, Li ₂ CO ₃ and K ₂ CO ₃ shown in Example 1 are used.
Are stored separately. During steady operation of the fuel cell power plant, the temperatures of the electrolyte storage units 22 and 23 shown in FIG. 4 are maintained at a temperature equal to or lower than the melting point of the stored alkali metal carbonate. The battery stack 36 is provided in the battery stack 36 and a battery performance detector 38 for detecting the power generation performance of the unit battery stack 5, and is provided in the upper gas header 8 or the intermediate gas header 29 of the unit battery stack 5 according to a detection signal of the battery performance detector 38. Electrolyte storage unit 22
And / or an electrolyte reservoir heating command device 39 operative to heat 23.

Although the power generation performance of the unit cell stack 5 decreases as the fuel cell power plant operates for a long time, the cell performance detector 38 arbitrarily sets an index value indicating the battery performance. For example, when the upper limit setting value of the internal resistance of the unit battery stack 5 is detected, the detection signal of the battery performance detector 38 is transmitted to the electrolyte storage unit heating command device 39. Then, the command device 39 is activated and the electrolyte storage unit 2
2 and / or 23 are heated. Specifically, the reformed gas or combustion exhaust gas from the steam reformer 37 is higher than that during steady operation, and at least the electrolyte storage units 22 and 23.
Is adjusted to a temperature higher than the melting point of one of the alkali metal carbonates stored in the unit battery stack 5 and supplied to the electrolyte storage unit 22 and / or 23 of the unit battery stack 5, and the sensible heat causes By heating the storage sections 22 and / or 23, the alkali metal carbonate in the solid phase or solid-liquid mixed crystal phase state stored in the storage sections 22 and / or 23 is melted and converted into a liquid phase state. Then, they can be mixed and supplied to the unit battery stack 5. In order to adjust the temperature of the reformed gas or the combustion exhaust gas from the steam reformer 37, the feed amount adjustment valve 40 of the raw fuel (NG) supplied to the steam reformer 37 is adjusted, or the steam By adjusting the supply amount adjustment valve 42 of the air supplied to the heating furnace 41 of the reformer 37, or by adjusting the supply amount adjustment valve 43 of the auxiliary fuel supplied to the heating furnace 41 as needed. To be achieved.

[0029]

According to the present invention, since the alkali metal carbonate having a melting point higher than that of the electrolyte is stored separately, the alkali metal carbonate is solid phase or solid-liquid mixed crystal phase during steady operation. It does not hinder the development of battery performance by inducing excessive wetting of the electrode by the excess electrolyte, and also suppresses the progress of corrosion due to the storage carbonate in the electrolyte storage section. Therefore, the reliability of the member and the unit battery stack is improved. Further, as shown in the examples, it is possible to store a relatively large amount of electrolyte in a region having a relatively large space such as a gas header, and it is also possible to maintain stable battery performance for a long period of time. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a unit battery laminate showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a schematic view of a two-block laminated battery stack.

FIG. 4 is a sectional view showing an internal structure of an intermediate gas header showing an embodiment of the present invention.

FIG. 5 is a schematic diagram of a molten carbonate fuel cell power generation system using a steam reformer as a fuel processor according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel electrode, 2 ... Oxidizer electrode, 3 ... Electrolyte plate, 4 ... Separator, 5 ... Unit battery laminated body, 6 ... Top plate, 7 ... Bottom plate,
8 ... upper gas header, 9 ... lower gas header, 10, 11
... sealing material, 12 ... fuel gas supply part, 13 ... fuel gas discharge part, 14 ... oxidant gas supply part, 15 ... oxidant gas discharge part, 16 ... fuel gas supply pipe, 17 ... fuel gas supply hole, 1
8 ... Fuel gas discharge hole, 19 ... Fuel gas discharge pipe, 20 ... Oxidizing gas supply hole, 21 ... Oxidizing gas discharge hole, 22, 23
... electrolyte storage part, 24 ... communication hole, 25 ... electrolyte supply hole,
26 ... Electric heater, 27 ... Electrolyte supply passage, 28 ... Current collector, 29 ... Intermediate gas header, 30 ... Oxidizing gas supply pipe, 31 ... Oxidizing gas discharge pipe, 32, 34 ... Partition wall, 33, 35 ... Opening part, 36 ... Battery stack, 37 ...
Steam reformer, 38 ... Battery performance detector, 39 ... Electrolyte storage unit heating command device, 40 ... Raw fuel supply amount adjusting valve, 41 ...
Heating furnace, 42 ... Air supply amount adjusting valve, 43 ... Auxiliary fuel supply amount adjusting valve, 44 ... Inverter, 45 ... Steam separator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Iwamoto 4026 Kuji-machi, Hitachi City, Ibaraki Prefecture Hitate Works, Ltd.Hitachi Research Laboratories (72) Satoshi Kuroe 4026 Kuji-cho, Hitachi City, Ibaraki Hitate Works Co., Ltd. Hitachi Research Laboratory (72) Inventor Shigenori Mitsushima 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitate Manufacturing Co., Ltd.Hitachi Research Laboratory (72) Inventor Shigeoki Nishimura 4026 Kuji Town, Hitachi City, Ibaraki Hitachi Research Institute, Ltd. In-house (56) Reference JP-A-64-3969 (JP, A)

Claims (5)

[Claims] 1. A pair of electrodes consisting of a fuel electrode and an oxidizer electrode
Place the electrolyte plate that holds the electrolyte between them,
Equipped with flow paths for fuel gas and oxidant gas outside the electrode
It is a unit battery stack consisting of separators.
In the method for replenishing the electrolyte of a molten carbonate fuel cell using a mixture of alkali metal carbonates or a eutectic salt as an electrolyte, the method has a melting point higher than that of the electrolyte and has a different composition.
Or a mixture of two or more of the alkali metal carbonates
In a container that houses the battery in a solid phase or solid-liquid mixed crystal phase
It is characterized in that the alkali metal carbonates of the solid phase or solid-liquid mixed crystal phase are melted and mixed by separately storing them at predetermined places and replenishing the batteries as electrolytes having a predetermined composition when replenishing the electrolyte. Method for replenishing electrolyte in molten carbonate fuel cell. Wherein the alkali metal carbonate stored in each separation of said claim 1 in which one or both alone or in combination is characterized by containing an alkaline earth metal compound serial mounting electrolyte replenishers method molten carbonate fuel cell. 3. The alkaline earth metal compound is a carbonate,
3. The electrolyte replenishing method for a molten carbonate fuel cell according to claim 2 , wherein the electrolyte is at least one kind of hydroxide or oxide. 4. A pair of electrodes consisting of a fuel electrode and an oxidant electrode
Place the electrolyte plate that holds the electrolyte between them,
Equipped with flow paths for fuel gas and oxidant gas outside the electrode
It is a unit battery stack consisting of separators.
In a molten carbonate fuel cell using a mixture of alkali metal carbonates or a eutectic salt as an electrolyte, the melting point of the electrolyte is
Alkali metal carbonates having a high melting point and different compositions are used alone or as a mixture of two or more kinds in a solid phase or a solid-liquid mixed crystal phase.
A storage unit for separately storing in a state is provided in a predetermined case in the container for accommodating the battery, a communication unit is provided between the storage units separately provided, and one or both of the storage units are heated. A mechanism is provided, and one of the reservoirs is provided with an electrolyte supply hole,
The electrolyte plate of the unit cell stack through the electrolyte supply passage and
And / or a molten carbonate fuel cell, which is in communication with an electrode . 5. A pair of electrodes comprising a fuel electrode and an oxidant electrode
Place the electrolyte plate that holds the electrolyte between them,
Equipped with flow paths for fuel gas and oxidant gas outside the electrode
A stack of unit cells formed by arranging a separator, or
A mixture of alkali metal carbonates or a eutectic salt as the electrolyte
Steam reforming upstream of a molten carbonate fuel cell stack body that
In quality reactor or a molten carbonate fuel cell power plant formed by providing a fuel production apparatus for coal gasification furnace or the like, the electrolyte
An alkaline metal carbonate having a melting point higher than the melting point and having a different composition is stored at a predetermined location in a container for accommodating the battery.
Separate from each other, and a communication part is provided between the storage parts, and one of the storage parts is provided with an electrolyte replenishing hole and an electrolyte replenishing hole.
The electrolyte plate and / or the electricity of the unit cell stack is connected via the supply passage.
A mechanism that is in communication with the pole and that introduces a high-temperature gas generated from the fuel production apparatus into at least one of the storage sections and heats at least one of the stored alkali metal carbonates to a temperature equal to or higher than the melting point; One melt of the alkali metal carbonate is merged with the other alkali metal carbonate stored in the adjacent storage unit through the communication unit, melted, mixed, and predetermined.
As an electrolyte of the composition from the reservoir through the electrolyte replenishment hole.
And from the electrolyte passage to the electrolyte plate of the unit battery stack and
A molten carbonate fuel cell power generation plant, characterized in that the electrode is replenished to the electrode .