JP5125376B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell configured by connecting a plurality of fuel cell stacks, and particularly to an insulating structure of each fuel cell stack.

In a power generation cell having a structure in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between an air electrode layer and a fuel electrode layer from both sides, oxygen (air) is supplied to the air electrode layer and fuel gas (H ₂ , CO, It is known that by supplying CH ₄ ), a power generation reaction occurs between the electrodes and an electromotive force is obtained. Water (steam), carbon dioxide and the like are generated by the power generation reaction.

However, since the electromotive force per unit cell is as small as about 1 V in the power generation cell having the above configuration, a large number of the power generation cells are usually stacked through stacking conductive members such as separators and current collectors to form a stack. By doing so, a substantial battery output is obtained.
In such a flat plate type fuel cell stack, metal end plates are provided at both upper and lower ends of the stack, and gas pipes are connected to the end plates to supply reaction gas to each power generation cell. It is comprised so that. The end plate is for fastening the laminated body from above and below to press-contact and tightly contact each component of the laminated body. Normally, the end plate and the laminated body are electrically insulated through an insulating member. It is in the state.

A high-power fuel cell in which a plurality of the fuel cell stacks are arranged in series has also been proposed.
That is, in a high-power fuel cell, for example, assuming that a voltage of 50 V can be obtained with one fuel cell stack 3 (for example, a configuration of 50 power generation cells), 10 fuel cell stacks 3 are arranged in series. In this case, a high voltage output of 500 V in total can be obtained. In this case, a potential difference of 500 V is generated between the positive electrode (+ output) of the first stack and the negative electrode (− output) of the last stack.

  By the way, in a fuel cell that operates in a high-temperature atmosphere of 600 ° C. or higher, such as a solid oxide fuel cell, a plastic pipe having poor heat resistance cannot be used as the gas pipe, and usually it has a high temperature oxidation resistance. Excellent metal piping (for example, stainless steel piping) is used. For this reason, in the high power type fuel cell having the above configuration, the end plates of the fuel cell stacks are always electrically connected via the metal pipe.

  In this state, when an insulation failure occurs between the end plate of the first fuel cell stack and the positive electrode, the positive electrode and the end plate are short-circuited. As a result, the last fuel cell stack connected in series A potential difference of 500 V, which is a total voltage, is generated between the negative electrode and the end plate. In particular, in a solid oxide fuel cell, in a high temperature and humidity atmosphere, electrical insulation between the negative electrode and the end plate is reduced, and sparks are likely to occur. As a result, the positive electrode and the negative electrode are short-circuited, resulting in a problem relating to reliability that the output is greatly reduced.

Patent Document 1 is disclosed as an electrical insulation structure of a fuel cell. Patent Document 1 discloses an electrical connection structure between fuel cell stacks when a plurality of fuel cell stacks formed by arranging a plurality of cells in series on an insulating substrate are juxtaposed.
JP 2006-310005 A

  The present invention has been made in view of the above problems, and provides a highly reliable fuel cell capable of preventing a short-circuit accident in battery output due to spark even in a high-power fuel cell formed by connecting a plurality of fuel cell stacks. The purpose is to do.

  That is, in the fuel cell according to claim 1, a plurality of fuel cell stacks configured by alternately stacking a plurality of power generation cells and separators are connected in series and / or in parallel and accommodated in a housing, and each fuel In a fuel cell in which a metal pipe is connected to the battery stack and a reaction gas is supplied to each power generation cell through the metal pipe, an insulating mechanism is provided in the middle of the metal pipe, and the insulating mechanism provides the above-mentioned of each fuel cell stack. The conductive portions excluding the laminated body are electrically insulated from each other.

  The fuel cell according to claim 2 includes a plurality of fuel cell stacks in which a plurality of power generation cells and separators are alternately stacked, and a plurality of fuel cell stacks configured by arranging a pair of end plates at both ends of the stack. In the fuel cell, which is connected in parallel and accommodated in the housing, a metal pipe is connected to the end plate, and a reaction gas is supplied from the metal pipe to each power generation cell through the gas passage of the end plate. An insulating mechanism is provided in the middle of the metal pipe, and the end plates of the fuel cell stacks are electrically insulated by the insulating mechanism.

  According to a third aspect of the present invention, in the fuel cell according to the first or second aspect, the fuel cell stack is fixed to the housing via an insulating member.

  According to the first and second aspects of the invention, since the insulating mechanism is provided in the middle of the metal pipe connected to the fuel cell stack, in the fuel cell in which a plurality of fuel cell stacks are connected in series and / or in parallel. In addition, it is possible to avoid electrically connecting the conductive portions (the end plates in claim 2) except for the stack (power generation unit) of each fuel cell stack through the metal pipe, and the conductivity of each fuel cell stack can be avoided. Since the electrical insulation of the conductive portion is ensured, the risk of sparking between the power generation portion and the conductive portion due to the high voltage is remarkably reduced, and the reliability is greatly improved.

  According to the invention described in claim 3, since the fuel cell stack is fixed to the housing via the insulating member, the fuel cell in which a plurality of fuel cell stacks are connected in series and / or in parallel is described above. It is possible to avoid electrically connecting conductive portions (for example, end plates) other than the stack (power generation unit) of each fuel cell stack through the housing, and insulation of the conductive portions of each fuel cell stack is prevented. Therefore, the risk of sparking between the power generation portion and the conductive portion due to the high voltage is remarkably reduced, and the reliability is dramatically improved.

Embodiments of a fuel cell according to the present invention will be described below with reference to the drawings.
1 is a schematic diagram showing an internal configuration of a solid oxide fuel cell according to the present embodiment, FIG. 2 is a diagram showing a configuration of a fuel cell stack, FIG. 3 is an electric circuit diagram showing a connection form of a plurality of fuel cell stacks, 4 and 5 are exploded perspective views showing an insulating mechanism for metal piping.

  In FIG. 1, reference numeral 1 denotes a fuel cell, and reference numeral 2 denotes a metal housing. A heat insulating material (not shown) is disposed on the inner wall of the housing 2 so that the inside of the housing 2 can be kept warm. A fuel cell stack 3 is installed in the housing 2 with the stacking direction being vertical.

As shown in FIG. 2, the fuel cell stack 3 includes a power generation cell 7 in which a fuel electrode layer 5 and an air electrode layer 6 are disposed on both surfaces of a solid electrolyte layer 4, and a fuel electrode current collector outside the fuel electrode layer 5. 8, an air electrode current collector 9 outside the air electrode layer 6, and a power generation unit having a structure in which a large number of separators 10 outside the current collectors 8 and 9 are stacked in order. An upper end plate 20a and a lower end plate 20b are disposed between upper and lower ends of the laminate (power generation unit) with insulating members (not shown) interposed therebetween. The upper and lower end plates 20a and 20b are used to stack the laminate in the stacking direction. It is made into a stack by making it fasten.
In addition, a tubular fuel gas manifold 13 and an air manifold 14 made of an insulating member such as ceramic are extended in the stacking direction at the edge of the stack.

Among the constituent elements of the laminate (power generation unit), the solid electrolyte layer 4 is composed of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 5 is a metal such as Ni or a cermet such as Ni-YSZ. The air electrode layer 6 is made of LaMnO ₃ , LaCoO ₃ or the like, the fuel electrode current collector 8 is made of a sponge-like porous sintered metal plate such as Ni, and the air electrode current collector 9 is made of Ag. The separator 10 and the upper and lower end plates 20a and 20b are made of stainless steel or the like.

  The separator 10 electrically connects the power generation cells 7 and has a function of supplying a reaction gas to the power generation cells 7. The separator 10 supplies the fuel gas supplied via the fuel gas manifold 13 to the outer peripheral surface of the separator 10. From the outer peripheral surface of the separator 10 is introduced from the outer peripheral surface of the separator 10 and air supplied through the air manifold 14 and the fuel gas passage 11 that is discharged from the substantially central portion of the separator 10 facing the anode current collector 8 of the separator 10. There are provided air passages 12 that discharge from substantially the center of the surface facing the 10 air electrode current collectors 9.

  In the present embodiment, six fuel cell stacks 3 having the above-described configuration are disposed in the housing 2, and these fuel cell stacks 3 are connected in series as shown in FIG. Each fuel cell stack 3 is a laminated body in which ten or more power generation cells 7 are stacked. For example, in 50 power generation cells, an electromotive force of about 50 V can be obtained per unit, and in a six-unit configuration, a total of about 300 V is obtained. High output can be obtained.

  Further, a metal pipe 21 for supplying fuel gas and a metal pipe 22 for supplying air are introduced into the housing 2 from the outside. These metal pipes 21 and 22 are made of stainless steel pipes having excellent high temperature oxidation resistance.

  The fuel gas pipe 21 is branched into a plurality of pieces in the housing 2, and each is connected to the upper end plate 20 a of each fuel cell stack 3 through an insulating mechanism 30, and the air pipe 22 is also formed in the housing 2. It is branched into a plurality of pieces, each of which is connected to the lower end plate 20b of each fuel cell stack 3 through the insulating structure mechanism 30. The fuel gas pipe 21 and the air pipe 22 are connected to the fuel gas manifold 13 through the gas passages (not shown) in the upper and lower end plates 20a and 20b, respectively. Is connected to the air manifold 14 described above.

  Next, the insulating mechanism 30 of the fuel gas pipe 21 (air pipe 22) will be described.

  FIG. 4 shows an example of the structure of the insulating mechanism 30. Each of the connecting portions of the fuel gas pipe 21 (air pipe 22) is provided with a rectangular metal flange 31 (made of stainless steel). The insulating ring 32 (ceramic ring) is interposed on the same axis a.

Bolt holes (not shown) are provided at four corners of each metal flange 31, and each metal flange 31 is tightened by inserting the metal bolt 33 into the bolt hole and tightening each metal flange 31. In this structure, the pipes 31 and 31 are pressed tightly to connect both pipes in an insulated state. A tightening portion of each metal flange 31 by the metal bolt 33 is provided with an insulating ring 34 (ceramic ring) for tightening, and the bolt hole is provided so that the metal bolt 33 does not contact the bolt hole when tightening. The inner diameter is made larger than the diameter of the metal bolt 33 so that a sufficient gap is secured between the metal bolt 33 and the bolt hole.
As a result, the fuel gas pipe 21 (air pipe 22) and the upper and lower end plates 20a, 20b of each fuel cell stack 3 are electrically insulated at the connecting portion of these pipes.

Next, FIG. 5 shows another configuration example of the insulating mechanism 30, and a fuel gas pipe 21 (air pipe 22) in which a metal flange 31 (made of stainless steel) is provided at each connection portion, and this fuel gas pipe 21 (air pipe). 22) and a half-cylindrical metal holder 35 (made of stainless steel).
A hole 40 having a diameter somewhat larger than the outer diameter of the fuel gas pipe 21 (air pipe 22) is provided at the center of both end portions 35a and 35b of the metal holder 35. The fuel gas pipe 21 (air The other end of the pipe 22) extends outward.

In the metal holder 35, an insulating ring 36 for insulation from the metal holder 35 is interposed between the metal flange 31 and the one end 35a of the metal holder 35 in one of the connecting portions. In the other connecting portion, an insulating ring 38 for insulation with the metal holder 35 is interposed adjacent to the metal flange 31, and a metal is further interposed between the insulating ring 38 and the other end 35 b of the metal holder 35. A metal ring 39 having a larger thermal expansion coefficient than the holder 35 is interposed.
For example, when SUS430 is used for the metal holder 35, SUS316 having a thermal expansion larger than that of SUS430 can be used as the metal ring 39. An insulating ring 37 (ceramic ring) for gas supply is interposed between the metal flanges 31 and 31. The insulating ring 36, the insulating ring 37, the insulating ring 38, and the metal ring 39 are provided on the same axis a as the fuel gas pipe 21 (air pipe 22).
In the above configuration, it is desirable to make the diameter of each metal flange 31 smaller than the diameter of the insulating ring 37 in order to improve the insulation of the connecting portion.

  In the insulating mechanism 30 in FIG. 5, the metal ring 39 in the metal holder 35 is thermally expanded in a high temperature atmosphere during operation, so that the metal flange 31, the insulating ring 36, the insulating ring 37, the insulating ring 38, the metal described above are expanded. Each ring 38 is in tight pressure contact, and this pressure contact force connects both pipes in an insulated state. In this structure, unlike the case of FIG. 4, a complicated bolting operation for connection can be eliminated.

By the way, when installing the fuel cell stack 3, it is normally fixed to the housing 2 at the lower end plate 20b.
In the present embodiment, as shown in FIG. 1, the lower end plate 20b of each fuel cell stack 3 is fixed to the bottom 2a of the housing 2 while being supported by a metal installation base 23. In this case, In order to ensure electrical insulation between the lower end plate 20b and the housing 2, an insulating plate 24 (insulating member) made of alumina or the like is interposed between the lower end plate 20b and the installation base 23, for example.

Further, each fuel cell stack 3 may be individually fixed to the bottom portion 2a of the housing 2, but for example, as shown in FIG. It may be installed in a row.
In this case, the installation base 23 of each fuel cell stack 3 is fixed to a support frame (not shown), and the support frame is fixed to the bottom 2 a of the housing 2. Also in this case, the insulating plate 24 is interposed between the lower end plate 20b of each fuel cell stack 3 and the installation base 23 so as to ensure electrical insulation between the lower end plate 20b and the support frame.

As described above, in the present embodiment, the metal pipes (the fuel gas pipe 21 and the air pipe 22) connected to the upper and lower end plates 20a and 20b of the fuel cell stack 3 are electrically insulated by the insulating mechanism 30. In the fuel cell 1 in which a plurality of fuel cells are connected in series, it is possible to prevent the end plates 20a and 20b of each fuel cell stack 3 from being electrically connected via the fuel gas pipe 21 and the air pipe 22.
As a result, electrical insulation between the end plates 20a, 20b of each fuel cell stack 3 can be ensured, and as a result, a total high voltage is applied to the end plate on the output side as in the prior art. This eliminates the risk of generating sparks between the end plate and the power generation unit, and can greatly improve the reliability of the solid oxide fuel cell 1 in a high-temperature and high-humidity atmosphere.

Further, since the lower end plate 20b of the fuel cell stack 3 is fixed to the housing 2 via the insulating member 24, in the fuel cell 1 in which a plurality of fuel cell stacks 3 are connected in series, each fuel is connected via the housing 2. It can be avoided that the end plates 20a and 20b of the battery stack 3 are electrically connected.
Thereby, similarly to the above, it is possible to ensure electrical insulation between the end plates 20a, 20b of each fuel cell stack 3, and, similarly to the above, between the end plates 20a, 20b and the power generation portion due to the high voltage. Thus, the risk of occurrence of sparks is remarkably reduced, and the reliability of the solid oxide fuel cell 1 in a high temperature and high humidity atmosphere can be remarkably improved.

As mentioned above, although this embodiment demonstrated the fuel cell 1 which connected the some fuel cell stack 3 in series, this invention is not limited to this, For example, as shown in FIG.3 (b), FIG. (A) It is applicable also to the fuel cell 1 of the structure which connected the fuel cell stack 3 group of the serial structure shown further more in parallel (for example, 3 sets), and as shown in FIG.3 (c), For example, the present invention can also be applied to a fuel cell 1 having a structure in which a plurality of (for example, four) high-power fuel cell stacks 3 each having 200 power generation cells 7 stacked and having an electromotive force of about 200 V are connected in parallel.
In the high-power fuel cell in which the number of stacks in one stack exceeds 100, the present invention is extremely effective in terms of ensuring reliability.

The schematic diagram which shows the internal structure of the solid oxide fuel cell which concerns on this invention. The figure which shows the principal part structure of the fuel cell stack which concerns on this invention. It is an electric circuit which shows the connection form of a some fuel cell stack, (a) is a serial connection type, (b) is a series-parallel connection type, (c) is a figure which shows a parallel connection type. The disassembled perspective view which shows the insulation mechanism of metal piping. The disassembled perspective view which shows the insulation mechanism different from FIG. 4 of a metal pipe.

Explanation of symbols

1 Fuel cell (solid oxide fuel cell)
2 Housing 3 Fuel cell stack 7 Power generation cell 10 Separator 20a, 20b End plate 21, 22 Metal piping 24 Insulating member 30 Insulating mechanism

Claims (3)

A plurality of fuel cell stacks configured by alternately laminating a plurality of power generation cells and separators are connected in series and / or in parallel and accommodated in a housing, and a metal pipe is connected to each fuel cell stack. In the fuel cell in which the reaction gas is supplied to each power generation cell through
An insulating mechanism is provided in the middle of the metal pipe, and the electrically conductive portions excluding the stacked body of each fuel cell stack are electrically insulated by the insulating mechanism. A plurality of power generation cells and separators are alternately stacked, and a plurality of fuel cell stacks configured by arranging a pair of end plates at both ends of the stacked body are connected in series and / or in parallel and accommodated in a housing. In the fuel cell in which a metal pipe is connected to the end plate, and a reaction gas is supplied from the metal pipe to each power generation cell through the gas passage of the end plate.
An insulating mechanism is provided in the middle of the metal pipe, and the end plate of each fuel cell stack is electrically insulated by the insulating mechanism. The fuel cell according to claim 1, wherein the fuel cell stack is fixed to the housing via an insulating member.

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