JPH0754708B2 - Molten carbonate fuel cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to the structure of a carbonate reservoir in a molten carbonate fuel cell.

[Prior Art] When the relationship between the carbonate reservoir and the electrolyte plate and the electrode plate in the conventional molten carbonate fuel cell is classified according to the joint relationship between them, the reservoir is as described in JP-A-62-234870. Of the structure in which both the electrolyte plate and the electrodes (anode, cathode) are in direct contact with each other, and as described in JP-A-63-318074 and JP-A-61-269861, only the electrolyte plate is contacted. However, the structure is not in contact with the electrodes.

On the other hand, the conventional examples are classified according to whether the inside of the reservoir is sealed or communicated with another gas atmosphere.
Those disclosed in JP 34870 and JP 63-318074 are sealed reservoirs, and those described in JP 61-269861 are gas atmospheres around the battery (usually nitrogen gas).
It is a reservoir in communication with.

Further, when classifying the conventional examples by the installation position of the reservoir, in all the above conventional examples, the reservoir is provided at the battery end,
The structure is such that carbonate is replenished from the reservoir at the end of the battery to the electrolyte plate and the electrode.

[Problems to be Solved by the Invention] In a molten carbonate fuel cell, the amount of carbonate in each electrode is adjusted according to the carbonate absorption capacity balance between the anode and the cathode, and the best cell performance is sought. If the amount of carbonate in the electrode becomes unnecessarily large, gas diffusion failure of the reaction gas will occur inside the electrode and the cell performance will deteriorate. On the other hand, in the electrolyte plate, it is desirable that the total pore volume of the electrolyte plate is filled with carbonate in order to prevent mixing (gas cross) of the anode gas and the cathode gas that sandwich the electrolyte plate.

For this reason, the electrode is designed so that the carbonate absorption capacity of the electrolyte plate is higher than that of either the anode or the cathode, and the total pore volume of the electrolyte plate is filled so that the overflowed carbonate is distributed to each electrode. . Therefore, even when replenishing carbonate from the reservoir, the carbonate is first replenished to the electrolyte plate and then
A reservoir with a structure that distributes to the anode and cathode depending on the electrode design is desirable.

In the one described in JP-A-62-234870, since the reservoir is in direct contact with both the electrolyte plate and the electrode, it is difficult to control the amount of carbonate in the electrode, and the carbonate in the electrode is difficult to control. There is a tendency for the cell performance to decrease as the amount increases beyond the design.

Further, in the one disclosed in JP-A-63-318074, the reservoir is in contact with only the electrolyte plate, and the reserved carbonate is not in direct contact with the electrode. Since carbonate is supplied to each electrode through the electrolyte plate, it is easy to control the amount of carbonate in the electrode.

However, this reservoir has a sealed structure. In the closed reservoir structure, oxygen in the atmosphere during battery production remains inside the reservoir. The presence of oxygen in the environment of molten carbonate accelerates the corrosion of the metallic material around the reservoir.

Further, if the reservoir is sealed, the inside of the reservoir is always kept at normal pressure (1ata). Therefore, when the fuel cell is operated under pressure, a pressure difference corresponding to the operating pressure is applied between the operating pressure (reaction gas pressure) of the cell and the inside of the reservoir, so that gas leakage easily occurs.

The reservoir structure described in JP-A-61-269861 does not have the above problems. However, since the reservoir, that is, the carbonate inside the reservoir communicates with the periphery of the battery (usually nitrogen gas), the carbonate is likely to be scattered and lost to the outside through the communicating portion.

Further, in any of the above-mentioned reservoir structures, the reservoir is installed at the end of the battery. As the battery area increases, the distance that the carbonate moves from the battery end portion to the battery center portion increases, making it difficult to uniformly replenish the electrode area.

An object of the present invention is to provide a replenished carbonate in a fuel cell provided with a reservoir so that the molten carbonate is in direct contact only with the electrolyte plate without suppressing the material corrosion and preventing the carbonate from scattering and disappearing. An object of the present invention is to provide a reservoir structure that can efficiently utilize the above.

Another object of the present invention is to provide a reservoir structure capable of uniformly and rapidly replenishing the electrodes with carbonate even in a large-area battery.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electrolyte plate, an anode and a cathode arranged on both sides of the electrolyte plate, an anode gas formed at a position capable of contacting the electrode plate, and In a fuel cell comprising a cathode gas flow channel and a reservoir for holding and holding an electrolytic solution, a molten carbonate is used as the electrolytic solution, and the reservoir has a position where molten carbonate inside the reservoir can contact only the electrolyte plate. And the internal space of the reservoir communicates with the anode gas flow channel space.

In addition, the reservoir is located in a part of the anode gas flow path,
In particular, it was decided to locate it in the anode gas flow channel within the effective power generation area.

[Operation] In the present invention, by communicating the inside of the reservoir with the anode gas, the inside of the reservoir is ventilated with the anode gas during the operation of the battery, and the oxygen mixed in the reservoir during the assembly of the battery is sent out. , Will not remain inside. As a result, the corrosion of the metallic material around the reservoir is not accelerated.

Further, since the inside of the reservoir and the anode gas are always equalized in pressure, no differential pressure is generated between the reservoir and the anode when the fuel cell is operated under pressure. Therefore, it is possible to change the anode gas pressure of the fuel cell to an appropriate value without causing the gas pressure inside the reservoir to be a problem and without worrying about gas leakage.

Moreover, since the anode gas is mainly a mixed gas of hydrogen and carbon dioxide, the molten carbonate in the reservoir comes into contact with the gas having a high carbon dioxide partial pressure by making the inside of the reservoir communicate with the anode gas. . As a result, the vapor pressure of the molten carbonate becomes high, and the amount of carbonate that scatters and disappears through the communication hole decreases. In other words, since it is possible to suppress the scattering and disappearance, the reserved carbonate can be efficiently used.

[Examples] Hereinafter, some examples of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cross section of a single cell P constituting a laminated battery. The unit cell P is composed of an electrolyte plate 1, electrodes of an anode 2 and a cathode 3 that face each other across the electrolyte plate, collector plates 4 and 5 arranged on each electrode, and a reaction formed on each collector plate. Gas flow path 6
And 7, and separators 8 and 9. The reaction gas flow passage is secured by the corrugated plates 6a and 7a.

Through the reaction gas flow path, a fuel gas containing hydrogen as a main component is supplied to the anode, and an oxidant gas that is a mixed gas of air and carbon dioxide is supplied to the cathode. The collector plates 4,5 have small holes, each reaction gas is supplied to each electrode 2, 3 through the small holes of the collector plates 4,5, and the presence of carbonate absorbed in each electrode. The hydrogen oxidation reaction occurs at the anode and the redox reaction occurs at the cathode.

For the purpose of efficiently supplying the fuel gas to the anode, the fuel gas is usually supplied only to the reaction gas channel 6b opened on the anode side. The reaction gas channel 6c that is not open to the anode side is closed.

On the other hand, the oxidant gas which also functions as a cooling gas is supplied to all the reaction channels 7b and 7c.

In this embodiment, a part of the reaction gas flow path which is open to the anode side is exclusively used as the carbonate reservoir 10. Also,
In order not to replenish the anode directly with the carbonate reservoir 10, the anode portion in contact with the reservoir 10 is removed along the reaction gas flow path, and the electrolyte plate 1 having the same thickness as the anode is attached. It is filled to form a carbonate supply path 11. Specifically, on the upper part of the electrolyte plate 1, the anode 2 and the carbonate supply path 11 are stacked side by side.

During manufacture of the battery, the reservoir 10 is replenished with an appropriate amount of carbonate 12. Molten carbonate inside the reservoir during operation 12
First moves to the electrolyte plate 11 through the small holes of the current collector plate 4. Electrodes are designed so that the carbonate absorption capacity of the electrolyte plate 1, the anode 2 and the cathode 3 becomes stronger in the order of electrolyte plate 1> anode 2> cathode 3. Therefore, the carbonate that has moved to the electrolyte plate substance in the carbonate supply path 11 is then absorbed by the electrolyte plate 1 and moves in the lateral direction (in-plane direction) of the electrolyte plate 1. A part of the carbonate supplied to the electrolyte plate 1 is distributed to the anode 2 and the cathode 3 and supplied to each electrode. In this embodiment, the electrolytic solution is replenished to each electrode through the electrolyte plate 1, so that the carbonate distributed according to the electrode design can be surely replenished to each electrode. Since the anode part in contact with the reservoir 10 is removed along the reaction gas flow path and the electrolyte plate 1 having the same thickness as the anode is filled to form the carbonate replenishment path 11, more specifically, Since the anode 2 and the carbonate replenishing path 11 are laminated side by side on the upper part of the electrolyte plate 1, more than necessary carbonate is absorbed by the anode even though the reservoir is arranged at any position on the anode. The cell performance does not deteriorate due to poor gas diffusion of the reaction gas.

In addition, since the electrolyte plate 1 is first supplied to the electrolyte plate 1 through the electrolyte plate of the carbonate supply path 11, the total pore volume of the electrolyte plate 1 is first filled with carbonate. Then, the carbonate overflowing from the electrolyte plate 1 is distributed to each electrode. That is, the entire pore volume of the electrolyte plate 1 is always filled with carbonate, and one of the functions required for the electrolyte plate, that is, the function of preventing gas crossing between the anode gas and the cathode gas, should be sufficiently exerted. You can

By filling the same material as the electrolyte plate 1 in the part in contact with the reservoir of the anode, the electrolyte plate 1 and the substance in the carbonate supply path 11 have good adhesion, and the carbonate moves smoothly. Be seen. Also, the anode 2 and the carbonate replenishment route 11
And, the boundaries do not have to be in close contact. Further, by forming a plurality of thin sheets of the same material as the electrolyte plate to form the carbonate replenishing path 11, the thickness adjustment with the anode 2 can be easily achieved. As described above, the reservoir structure of the present invention can be easily manufactured.

In this embodiment, a part 10 of the reaction gas channel 6b opened on the anode side is exclusively used as a reservoir. A gas communication hole 13 is provided between the inside of the reservoir 10 and the anode gas flow channel 6b. Further, in order to prevent the molten carbonate 12 in the reservoir 10 from flowing out of the battery, its inlet and outlet are sealed by an appropriate means to store the carbonate inside.

In the conventional tank with carbonate sealed inside, air remains in the reservoir when the battery is assembled (when carbonate is replenished), and the temperature of the air becomes high and the carbonate melts. It will remain even if it becomes. This means that the remaining oxygen accelerates the corrosion of the metal material such as the separator 8, the corrugated plate 6a, the current collector plate 4 and the like, and is highly likely to be mixed with the fuel gas containing hydrogen as a main component to cause a combustion reaction. .

In the present invention, the inside of the reservoir 10 and the anode gas passage
By providing the gas communication hole 13 between the 6b, the inside of the reservoir will be ventilated with the anode gas, as a result,
Metal corrosion around the reservoir can be reduced.

Further, by providing the gas communication hole 13, it is possible to always equalize the pressure inside the reservoir with the anode. As a result, there is no concern about the generation of a differential pressure between the reservoir and the anode when the fuel cell is operated under pressure. Therefore, the fuel cell can be operated under pressure without making the gas pressure inside the reservoir a problem.

Furthermore, by communicating the inside of the reservoir with the anode gas,
Since the inside of the reservoir can be maintained at a high carbon dioxide partial pressure, it is possible to suppress the amount of carbonate that scatters and disappears through the communication hole. As a result, the reserved carbonate salt can be used more efficiently as compared with the conventionally known one in which the inside of the reservoir communicates with the periphery of the battery (nitrogen gas). In addition, as the electric scale of the reservoir having a structure communicating with the surroundings of the battery as in the conventional example increases, it becomes difficult to uniformly replenish an electrode having a wide area only by replenishing carbonate from the end of the battery. In this embodiment, a part of the anode gas flow path inside the battery is diverted to a reservoir, so that the carbonate having a large area can be uniformly and quickly replenished.

According to the present embodiment, even in a large-area stacked battery, it becomes possible to install the reservoir within the effective power generation area of the electrolytic plate of each single cell P, so that the electrode surface is evenly distributed between the single cells. It is possible to replenish the carbonate without variation.

FIG. 2 shows an embodiment in which the reservoir 10 of the present invention is provided at the end of the battery. In the figure, the reservoir 10 is provided in the separator 8, and the carbonate in the reservoir is in direct contact with only the electrolyte plate 1. The space above the reservoir 10 is the passage 13
It communicates with the anode gas flow path 6 through the (opening).

Even in this embodiment, since the inside of the reservoir communicates with the anode gas, the inside of the reservoir is ventilated with the anode gas as in the embodiment of FIG. 1, and as a result, In addition to reducing metal corrosion around the reservoir, there is no concern about pressure difference between the reservoir and the anode when the fuel cell is operated under pressure. Therefore, the fuel cell can be operated under pressure without making the gas pressure inside the reservoir a problem. Furthermore, compared to the case where it communicates with the surroundings of the battery (nitrogen gas), the amount of carbonate that scatters and disappears can be suppressed
The reserved carbonate can be used efficiently.

FIG. 3 shows an embodiment in which the anode is laminated on the lower side of the electrolyte plate. The same members that perform the same functions as those in FIG. 1 are indicated by the same numbers, and the description thereof will be omitted. In this structure, three continuous portions 10 ', 10 ", 10' of the anode gas flow channel 6 are exclusively used as reservoirs. The left and right reservoirs 10 ', 10' are
In the embodiment shown in FIG. 1, a portion corresponding to the reaction gas flow channel 6c which is not opened to the electrode side is used, and after the carbonate 12 is replenished inside, both end portions thereof are closed. The central reservoir 10 ″ uses a portion corresponding to the channel 6b opened on the electrode side in the embodiment shown in FIG. 1, and is filled with the felt 14 of inorganic fiber.

Further, in the case of this embodiment, the corrugated plate 6a located between the reservoirs 10 'and 10 "is further provided with a communication hole 15 for molten carbonate in the lower part thereof.

The inorganic fiber 14 in this example serves to prevent molten carbonate as a holding material from flowing out of the battery and to move the molten carbonate to the carbonate supply path 11 by capillarity. It is preferable to use alumina (Al ₂ O ₃ ), zirconia (Zr ₂ O ₃ ) or the like, which has corrosion resistance to molten carbonate.

According to the present embodiment, even when the anode is laminated on the lower side of the electrolyte plate, a reservoir can be provided, and the portion corresponding to the reaction gas flow channel 6c which is not open to the electrode side is provided as the reservoir. Since it is used as, the reserve amount of carbonate can be increased. Further, in this example, since it is possible to replenish the reservoir with carbonate (powder state) before stacking the current collector plate on the corrugated plate, it is possible to compare with the case where the anode is stacked above the electrolyte plate. Then, there is a feature that the carbonate replenishment work at the time of battery assembly becomes easy.

In addition, in the above-described embodiment, only one reservoir is formed in each single cell of the battery. However, the present invention is not limited to having only one reservoir. For example, in the case of FIGS. 1 and 3, it is possible to configure another parallel anode gas flow path portion to be used exclusively as a reservoir, and those and the embodiment shown in FIG. It is also possible to configure in combination with the example. By doing so, it becomes more reliable to uniformly and quickly replenish the carbonate in the electrode surface even in a large-area laminated battery.

Further, in the present invention, if the internal space of the reservoir in the molten carbonate fuel cell is connected to the anode gas space, the intended purpose can be achieved. It is obvious that the shape of is not limited to the shape shown in each of the above embodiments.

FIG. 4 shows an embodiment in which a large area laminated battery is provided with the reservoir of the present invention. The same members as those in FIGS. 1 to 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In this figure, four unit cells P are integrated, and each unit cell has a structure in which an anode is stacked below the electrolyte plate as shown by disassembling one unit cell. As shown in the figure, this one uses exclusively three locations in the anode gas flow path as the reservoirs 10, 10, 10, and a carbonate replenishing path 11 is provided at the location of the anode 2 corresponding to the reservoirs. Specifically, on the upper side of the current collector plate 3, three carbonate supply paths 11 (made of the same material as the electrolyte plate 1) and two anodes 2 are stacked side by side. By doing so, it is possible to provide a reservoir inside the battery even in a large area, and it is possible to uniformly replenish the carbonate even in an electrode having a large area. Further, by providing a plurality of reservoirs at equal intervals, the reservoirs can be positioned without causing the anode gas to flow unevenly.

According to the embodiments of the present invention described above, the reservoir can be installed inside the battery or at the end of the battery, and the anode can be stacked either above or below the electrolyte plate. Also makes it possible to install a reservoir. Further, even in a large-area laminated battery, by installing reservoirs at equal intervals inside each unit cell, the anode gas is not unevenly flowed, the electrode surface is even, and there is no variation between unit cells. Can be supplemented with carbonate.

[Effects of the Invention] According to the present invention, in a fuel cell provided with a reservoir so that the molten carbonate directly contacts the electrolyte plate, the interior of the reservoir is communicated with the anode gas, thereby accelerating material corrosion. Since it is possible to suppress the disappearance of carbonates,
A reserve structure can be created so that the supplied carbonate can be used efficiently. Further, even in the case of a battery having a large area, it is possible to provide a reservoir structure capable of uniformly and quickly replenishing the electrodes with carbonate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a single cell showing an embodiment of the present invention. FIG. 2 is a cross-sectional view of a battery end portion showing an embodiment in which the reservoir of the present invention is provided at the battery end portion. FIG. 3 is a cross-sectional view of a single cell showing an embodiment of the present invention when an anode is laminated on the lower side of an electrolyte plate. Figure 4 shows
It is a perspective view which shows one Example which provided the reservoir of this invention in the large area laminated battery. [Explanation of symbols] 1 ... Electrolyte plate, 2 ... Anode 3 ... Cathode, 4,5 ... Current collector plate 6,7 ... Reacting gas flow path, 8, 9 ... Separator 10 ... Reservoir, 11 …… Carbonate supply route 12 …… Carbonate, 13 …… Gas communication hole 14 …… Inorganic fiber, 15 …… Carbonate communication hole P …… Single cell

Claims (8)

[Claims] 1. An electrolyte plate, an anode and a cathode arranged on both sides of the electrolyte plate, an anode gas and a cathode gas flow channel formed at a position capable of contacting the electrode plate, and a reservoir for holding and holding an electrolytic solution. A fuel cell comprising
A molten carbonate is used as the electrolytic solution, and the reservoir is provided at a position where the molten carbonate inside the reservoir can contact only the electrolyte plate, and the interior space of the reservoir communicates with the anode gas channel space. A feature is a molten carbonate fuel cell. 2. A molten carbonate fuel cell according to claim 1, wherein the reservoir is located within the effective power generation area of the anode. 3. The fuel cell according to claim 1 or 2, wherein the anode gas flow channel comprises a plurality of partitioned flow channels. 4. The molten carbonate fuel cell according to claim 3, wherein a part of the anode gas flow channel is exclusively used as a reservoir. 5. The fuel cell according to claim 1, wherein a plurality of reservoirs are provided within the effective power generation area of the anode. 6. A molten carbonate fuel cell according to any one of claims 1 to 5, characterized in that a member holding molten carbonate is inserted in the reservoir. 7. The molten carbonate fuel cell according to claim 6, wherein the holding member is an inorganic fiber. 8. A molten carbonate fuel cell according to claim 7, wherein alumina or zirconia is used as the inorganic fiber.