JPH1032016A - Fastening and heating device of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the thermal deflection in an excessive operation time, and to heat the cells evenly for a short time, by providing a pair of current drawing-out plates and a pair of insulating plates having a necessary property, and realizing the fastening and the heating while maintaining a soft structure. SOLUTION: To this fastening and heating device 10, a pair of current drawing-out plates 12 contacting to the upper and the lower surfaces of a laminate fuel cell 7; a pair of insulation members 14 contacting to the upper and the lower surfaces of the plates 12; a pair of fastening plates 16 contacting to the upper and the lower surfaces of the members 14; a gas header 18; and a gas heater 20; are provided. And at least to one side of the plates 12, a gas passage 12b communicated to the gas header 18 is formed through a felxible piping 19. The plates 12 which consist of a copper, a stainless steel, or the like have the flexibility and the heat conductivity almost same as a single separator, while the members 14 which consist of a fire- resisting material, a hard heat insulating material, or the like have a sufficient insulating property and flexibility. The thickness of the plates 12 is made two to three times of the thickness of the separator, the surfaces contacting to a battery 7 are finished at a high plane accuracy, and current terminals 12a are formed integrally or welded to the plates 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten carbonate fuel cell, and more particularly, to a fuel cell tightening and heating apparatus capable of tightening and heating while maintaining a flexible structure of the fuel cell.

[0002]

2. Description of the Related Art As shown schematically in FIG. 3, a molten carbonate fuel cell has a cell 4 in which a thin flat electrolyte plate 1 is sandwiched between a fuel electrode (anode) 2 and an air electrode (cathode) 3. And a separator 5 sandwiching the cell 4 therebetween. Since the voltage of each separator 4 is low (about 0.8 V), the separators 5 are used to obtain a high voltage by stacking the separators. A battery in which a plurality of cells are stacked is called a stack.

An anode gas containing hydrogen is supplied to the anode 2 and a cathode gas containing air is supplied to the cathode 3 to the upper and lower surfaces of the separator 5 via a manifold (not shown). By maintaining a high temperature (about 650 ° C.) in this state, electric power is generated by an electrochemical reaction in each cell 4, and a current is taken out in a direction perpendicular to the cell surface (vertical direction in the figure). At this temperature, the electrolyte (molten carbonate) contained in the electrolyte plate 1 is dissolved, and the gas seal between the upper and lower separators is maintained by the wetness of the molten salt and the separator. This seal is called a wet seal. In FIG. 3, the positions of the anode 2 and the cathode 3 may be upside down.

As described above, the separator 5 has functions such as a partition plate for separating anode gas and cathode gas, a current collector for connecting each cell, and a gas manifold for supplying an note gas and a cathode gas to each cell. . In order to manufacture such a separator accurately and inexpensively, the applicant of the present application has created and has already implemented a corrugated separator 5a (A) and a press separator 5b (B) as shown in FIG. These separators have high planar accuracy and are formed to be thin. For example, even if they have a reaction area of about 1 m ² or more, the thickness is only about 5 mm or less, and the whole has flexibility. .

FIG. 5 is an overall configuration diagram of a conventional additional heating device for a fuel cell. Conventional molten carbonate fuel cell (MC
In FC), the fuel cell (stack 7) laminated is sandwiched between two rigid clamping plates 6, and the stack 7 is clamped by the two clamping plates 6 at a substantially constant surface pressure. One of the two fastening plates 6 (usually the lower side) also functions as a gas header for supplying and discharging gas to and from the stack 7, and therefore has a thickness of at least 100 mm or more. Further, the other clamping plate 6 does not have the function of a gas header, but requires sufficient rigidity to maintain the flatness at the time of tightening, and therefore has a thickness of at least 50 mm or more. Furthermore, these fastening plates 6 have a built-in heater (not shown) for heating the fastening plates and the fuel cell when the fuel cell is heated. This heater is stack 7
Used to raise the temperature of the stack and maintain the stack temperature at a high temperature. The electricity (DC current) generated in the fuel cell is usually taken out of the upper and lower fastening plates 6 to the outside.

[0006]

FIGS. 6A and 6B are temperature distribution diagrams in the plane of a cell having a reaction area of about 1 m ² , wherein FIG. 6A shows a state at no load and FIG. 6B shows a state at the time of rated load operation. I have. This figure is an example of a parallel flow, and both gases (annot gas and cathode gas) flow upward as indicated by arrows in the figure.

As is apparent from this figure, the temperature inside the cell is almost uniform when no load is applied (A), but the temperature on the outlet side increases by about 100 ° C. due to reaction heat during load operation (B). .

For this reason, in FIG. 5, the end cells 7a located at the upper and lower ends of the stacked stack 7 have one surface in contact with one of the upper and lower clamping plates 6 and the other surface in contact with the stack 7 from the outside. It is held down by the clamping plate 6.
In this state, when the operation of the fuel cell is repeatedly changed from no load to load operation, the cells at the center of the stack 7 and the end cells 7a (at the upper and lower ends) during the transient operation due to the presence of upper and lower thick plates (clamping plates 6). (Cell), which causes a problem in that a temperature difference is generated, and distortion is increased near the end cell.

As schematically shown in FIG. 7, during rated operation, the temperature distribution of the tightening plate is kept substantially constant because the plate thickness is substantially large despite the temperature gradient in the stack. As a result, there is a problem that the tightening force distribution of the thick plate cannot follow the stack height distribution due to the temperature distribution, and the contact between cells becomes poor.

That is, in the large-capacity stack, as described above, the temperature distribution of the heater plate (clamping plate 6) and the stack 7
Are different from each other, and accordingly, various dimensions (height, outer shape) differ due to thermal expansion of each cell. Further, in a rapid change such as load shedding, the thick plate structure (clamping plate) has a large heat capacity and cannot follow the temperature change of the stack in a short time. For this reason, cracks are generated in the electrolyte plate constituting the wet seal and the cell due to the repetition of the temperature distribution and the transient change, and adverse effects such as a drastic reduction in the life are caused.

Further, in the conventional heating means, since the temperature of the stack is raised by a heater built in the clamping plate, the heat of the heater plate is gradually transmitted from the end cell to the central cell at the time of raising the temperature, so that the heat is hardly transmitted. In addition, there is a problem that it takes a very long time to raise the temperature and it is not possible to uniformly heat each cell.

The present invention has been made to solve the above problems. That is, an object of the present invention is to perform tightening and heating while maintaining the flexible structure of the fuel cell, thereby reducing thermal distortion generated during transient operation, and heating each stacked cell almost uniformly in a short time. It is an object of the present invention to provide a fuel cell fastening heat device that can be used.

[0013]

According to the present invention, in a fuel cell tightening heating device for heating a fuel cell in which a plurality of cells are stacked via a separator and heating the fuel cell, the fuel cell contacts upper and lower surfaces of the fuel cell, And a pair of current extracting plates having substantially the same flexibility and thermal conductivity as a single separator, and a pair of heat insulating materials in contact with the upper and lower surfaces of the current extracting plate and having sufficient heat insulating performance and elasticity. A pair of clamping plates which are in contact with the upper and lower surfaces of the heat insulating material and which can apply a sufficient tightening force to the fuel cell through the heat insulating material and the current extracting plate at the time of tightening; A gas header for supplying / discharging gas to / from the fuel cell, and a gas heater for heating the gas to be supplied to the gas header. The gas is heated and Heating each cell, the fuel cell of the fastening heating device is provided, characterized in that.

According to the structure of the present invention, the fuel cell is fastened by the fastening plate disposed outside the heat insulating material via the heat insulating material and the current extracting plate. The heat insulating material has sufficient heat insulating performance and elasticity, and the current extraction plate has almost the same flexibility and heat conductivity as a single separator. Tightening and heating can be performed while maintaining the flexible structure of the fuel cell without any components, thereby reducing thermal distortion generated during transient operation, preventing tile cracking due to repeated thermal distortion, and securing the flexible structure with a flexible structure. Therefore, the tightening force distribution is improved.

Further, since there is no thick plate structural member in the heating portion as in the prior art, the heat capacity is small, and a gas header is connected to the fuel cell via a flexible pipe (for example, bellows). Since the gas heated by the gas heater is supplied to each cell and heated, the temperature difference between the cell near the end of the stack and the cell at the center of the stack can be reduced even during a transient, and the stacked cells can be shortened almost uniformly. Can be heated in time.

According to a preferred embodiment of the present invention, at least one of the current extraction plates has a gas passage for supplying / discharging gas to / from a fuel cell, and one end of the flexible pipe communicates with the gas passage. The other end communicates with the gas header.
With this configuration, while keeping the current extraction plate in a flexible structure,
Gas can be supplied / discharged to / from the fuel cell through the flexible pipe and the gas passage of the current extraction plate.

The gas heater includes an electric heater or a gas burner. With this configuration, the heat radiation loss can be reduced, the gas supplied to the fuel cell can be efficiently heated, and the temperature rise time can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description will be omitted. FIG. 1 is an overall configuration diagram of the additional heating device for a fuel cell according to the present invention. As shown in this figure, the tightening additional heat device 10 of the present invention tightens the stacked fuel cells 7 (stacks) and heats them.

Referring to FIG. 1, an additional heating device 10 according to the present invention is shown.
Is a pair of current extraction plates 12 in contact with the upper and lower surfaces of the fuel cell 7.
And a pair of heat insulating materials 14 in contact with the upper and lower surfaces of the current extraction plate 12.
And a pair of tightening plates 16 in contact with the upper and lower surfaces of the heat insulating material 14.
And a gas header 18 for supplying / discharging gas to / from the fuel cell 7
And a gas heater 20 for heating the gas supplied to the gas header 18.

The current extracting plate 12 is a flat plate made of a metal material having high thermal conductivity and high electric conductivity (for example, copper, stainless steel, etc.), and has a thickness of a single separator (for example, about 5 mm).
mm) to 2 to 3 times (approximately 10 to 15 mm) the thickness, and has almost the same flexibility and thermal conductivity as the separator. The surface of the current extraction plate 12 which is in contact with the fuel cell 7 is finished with high planar accuracy so that the entire surface of the fuel cell can be held at a substantially uniform surface pressure. In addition, a current terminal 12a is integrally formed on each current extraction plate 12, respectively.
Alternatively, they are connected by welding or the like.

Further, as shown in FIG. 1, at least one of the current extracting plates 12 (the lower side in this figure) is provided with a gas passage 12b for supplying / discharging gas to / from the fuel cell 7 through the plate. .

The heat insulating material 14 is formed of a material having sufficient heat insulating performance and elasticity, for example, a refractory material or a hard heat insulating material. The heat insulating material 14 has a high temperature at least equal to or higher than the maximum temperature (about 700 ° C.) of the fuel cell 7 and a surface pressure (for example, about 3 kg) for sandwiching the fuel cell 7 via the current extraction plate 12.
/ Mm ² ) for the long term. Further, in response to thermal deformation during operation of the fuel cell 7,
It is necessary that the fuel cell 7 has elasticity (elastic coefficient) enough to be slightly deformed in the vertical direction while maintaining the surface pressure holding the fuel cell 7.

Further, as shown in FIG. 1, at least one (lower side in this figure) of the heat insulating material 14 has a sufficiently large opening for passing a pipe connecting the gas passage 12b of the current extraction plate 12 and the gas header 18. 14a is provided. The gap between the openings 14a is preferably filled with a resilient heat insulating material (for example, cahor).

The pair of upper and lower clamping plates 16 does not require a high-temperature creep-resistant material because the fuel cell is clamped through a heat insulating material and a current extracting plate, and further directly clamps the fuel cell as in the conventional clamping plate 6. Unlike the case, high planar accuracy is not required. The tightening plate 16 is held at a predetermined surface pressure by an appropriate tightening device 22, for example, a press bellows, a compression spring, a hydraulic cylinder, or the like. As the fastening device 22, other known means can be used. The fastening plate 16 may be divided for each spring.

The gas header 18 has at least four of an inlet header 18a and an outlet header 18b for anode gas and an inlet header 18c and an outlet header 18d for cathode gas.
Consists of strains. Each of the gas headers 18 a to 18 d is connected to each of the internal manifolds of the fuel cell 7 via a flexible pipe 19. That is, one end of the flexible pipe 19 communicates with each gas passage 12b of the current extraction plate 12, and the other end communicates with the gas headers 18a to 18d. With this configuration, the gas can be supplied / discharged to / from the fuel cell 7 via the flexible pipe 19 and the gas passage 12b of the current extraction plate 12, while the current extraction plate 12 is held in a flexible structure.

The gas heater 20 has one or both of anode gas and cathode gas,
The gas supplied to 8 is heated. Also,
The gas heater 20 has a built-in electric heater or gas burner. With this configuration, the heat radiation loss can be reduced, the gas supplied to the fuel cell can be efficiently heated, and the temperature rise time can be reduced. In addition, the heater 20 for anode gas
Is preferably indirect heating because the anode gas is flammable. Since the main component of the cathode gas is air, the heater 20 for the cathode gas can use both indirect heating and direct heating.

FIG. 2 is a diagram schematically showing the technical means of the present invention. As shown in this figure, since the upper and lower end heat plates (clamping plates 6) having a large heat capacity are eliminated and the flexible structure and the weight are reduced, it is possible to achieve a faster start-up and gas heating. With the configuration of the present invention described above,
Since the fuel cell 7 is tightened by the tightening plate 16 disposed outside the heat insulating material 14 via the heat insulating material 14 and the current extracting plate 12, tightening and heating can be performed while maintaining the flexible structure of the fuel cell 7. Thereby, thermal distortion generated during transient operation can be reduced, tile cracks due to repeated thermal distortion can be prevented, and the tightening structure becomes flexible, so that the tightening force distribution is improved.

Further, since there is no thick plate structural member in the heating portion as in the prior art, the heat capacity is small, and the gas header 18 is connected to the fuel cell via a flexible pipe 19 (eg, bellows). Since the gas heated by the gas heater 20 is supplied to each cell via the gas header 18 and heated, the temperature difference between the cell near the end of the stack and the cell at the center of the stack can be reduced even during a transition, and the stacked cells can be removed. It can be heated almost uniformly in a short time.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0030]

As described above, according to the present invention, the heater equipment and the thick plate structure are eliminated, and the additional heating device for the fuel cell can be reduced in weight and cost, the heat capacity can be reduced, and the startup time can be shortened. The temperature distribution in the stack stacking direction can be made uniform by eliminating the thick plate such as the heater plate and performing gas heating.

Therefore, the tightening and heating device for a fuel cell according to the present invention can be tightened and heated while maintaining the flexible structure of the fuel cell, thereby reducing the thermal distortion generated at the time of transient operation and stacking. It has an excellent effect that each cell can be heated almost uniformly in a short time.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an additional heating device for a fuel cell according to the present invention.

FIG. 2 is a diagram schematically showing the technical means of the present invention.

FIG. 3 is a schematic view of a molten carbonate fuel cell.

FIG. 4 is a configuration diagram of a separator.

FIG. 5 is an overall configuration diagram of a conventional additional heating device for a fuel cell.

FIG. 6 is a temperature distribution diagram in a cell plane.

FIG. 7 is a schematic diagram showing a stack height distribution during rated operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis chamber plate 2 Anode 3 Cathode 4 Cell 5 Separator 6 Clamping plate 7 Stack 7a End cell 10 Tightening additional heating device 12 Current extraction plate 12a Current terminal 12b Gas passage 14 Heat insulating material 14a Opening 16 Tightening plate 18, 18a-18d Gas header 19 Flexible piping (bellows) 20 Gas heater 22 Tightening device

Claims (3)

[Claims] A fuel cell tightening heat device for heating a fuel cell in which a plurality of cells are stacked via a separator and heating the fuel cell, wherein the flexible device is in contact with the upper and lower surfaces of the fuel cell and is substantially equivalent to a single separator. A pair of current extraction plates having electrical conductivity and thermal conductivity;
A pair of heat insulating materials that are in contact with the upper and lower surfaces of the current extraction plate and have sufficient heat insulating performance and elasticity;
In addition, a pair of clamping plates capable of applying a sufficient clamping force to the fuel cell via the heat insulating material and the current extracting plate at the time of clamping, and supplying / discharging gas to / from the fuel cell via flexible piping. A gas header and a gas heater for heating a gas supplied to the gas header are provided.The fuel cell is fastened through a heat insulating material and a current extraction plate by a fastening plate, and the supply gas is heated by the gas heater. And heating the fuel cell. 2. At least one of the current extraction plates has a gas passage for supplying / discharging gas to / from a fuel cell, one end of the flexible pipe communicating with the gas passage, and the other end communicating with a gas header. The tightening heating device for a fuel cell according to claim 1, wherein: 3. The apparatus according to claim 1, wherein the gas heater includes an electric heater or a gas burner.