JPH11111314A - Cathode collecting structure for solid electrolyte fuel cell, and solid electrolyte fuel cell power generating module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the collecting efficiency, without an air pole current flowing through other adjacent cells by providing an exhaust gas separator for partitioning air electrode side exhaust gas and fuel pole side exhaust gas and a cathode collector adhered to a cylindrical fuel cell in the axial direction and extended to the upper part beyond the exhaust gas separator. SOLUTION: In a cathode collector 21, a lead member 22 extended in the longitudinal direction of a cell passes through an exhaust gas separator, and one end of the lead member 22 is positioned in the fuel electrode side exhaust, and the other end thereof is positioned in the air electrode side exhaust. A part of the lead member 22 positioned in the air electrode side exhaust is connected to an air pole of a cell so as to take an air pole current. At this stage, the lead member 22 is inserted between two cells arranged in the vertical direction and connected to each cell. The air electrode is coated with the collecting auxiliaries 23 at the part between a coating layer 76, and the periphery of the air pole is coated preferably with collecting auxiliary rings 2 at constant intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode current collecting structure used for a solid oxide fuel cell (hereinafter also referred to as "SOFC") and a power generation module using the cathode current collecting structure.

[0002]

2. Description of the Related Art The cell structure of a solid oxide fuel cell includes:
There are a cylindrical system and a flat plate system, and the cylindrical system has a vertical stripe cylindrical system and a horizontal stripe cylindrical system depending on the connection method of a single cell. As shown in FIGS. 16 and 17, the vertical stripe cylindrical type has a type in which a fuel electrode 83, a solid electrolyte 82, and an air electrode 81 are arranged in this order from the outside. This is constituted by one single cell on one cylindrical porous support tube 84.

In this type, a fuel containing hydrogen or carbon monoxide is passed through the outside of the cell, and air containing oxygen is passed through the inside of the cell. At the inner air electrode 81, oxygen in the air receives electrons and becomes oxide ions as described below, passes through the solid electrolyte, and reaches the outer fuel electrode 83.

(1/2) O ₂ + 2e ⁻ → O ²⁻ (reaction formula A) At the fuel electrode 83, the oxide ions react with hydrogen and carbon monoxide to release electrons as follows. Produces water and carbon dioxide.

H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (reaction formula B) CO + O ²⁻ → CO ₂ + 2e ⁻ (reaction formula C) The electricity generated by such a battery reaction is transmitted through the interconnector 85. Taken out through. That is, the cell electrolyte 8
The fuel electrode 2 and the fuel electrode 83 are not completely cylindrical, and have a gap extending in the longitudinal direction, from which electricity generated at the inner air electrode 81 is extracted. Each cell is connected in series by connecting this interconnector to the fuel electrode 83 of an adjacent cell. Then, as shown in FIG. 18, one end of the plate placed so as to sandwich the cells connected in series is an anode of the stack, and the other end is a cathode. That is, the plates at both ends play the role of a current collector.

Generally, it is said that the cylindrical system has better mechanical strength than the flat plate system and the like, and that thermal stress is easily reduced. However, yttria-stabilized zirconia (YSZ) used as a solid electrolyte exhibits high ionic conductivity at high temperatures of about 800 ° C to about 1000 ° C. Due to the operation at such a high temperature, even in the case of the cylindrical type, the thermal stress caused by the difference in the coefficient of thermal expansion is concentrated around the interconnector, which is the joining portion of different materials, and cracks are easily generated. The air leaking from this crack
Combustion with fuel gas locally heated the area around the crack, damaging the cell and shortening the life of the system.

[0007] Therefore, a cell structure (hereinafter, also referred to as an "interconnector-less system") having neither an interconnector nor a vertical stripe system or a horizontal stripe system has been developed (see Japanese Patent Application Laid-Open No. Hei 7-263001). This is, as shown in FIG. 19, the fuel electrode 93 and the electrolyte 9 in order from the inside.
2 and a cylindrical structure in which the air electrode 91 is laminated,
A conductive tube 94 for fuel supply is inserted inside the fuel electrode. A conductive felt (for example, nickel felt) is filled between the fuel electrode 93 and the conductive tube 94, and electrically connects the fuel electrode 93 and the conductive tube 94. As is clear from the figure, this cell is constituted by one single cell in one cylinder. An air electrode 91 is used as an anode of the cell, and a conductive tube 94 is used as a cathode of the cell.

The conductive tube 94 is provided with a large number of pores, and natural gas (mainly methane gas) and water vapor supplied to the conductive tube 94 are supplied to the conductive tube 95 through the holes on the tube. And is converted into hydrogen and carbon monoxide which contribute to the battery reaction by the catalytic action of the conductive felt 95. In this cell, since reforming is performed inside the cell, there is no need to provide a separate reformer. The hydrogen and carbon monoxide generated inside the fuel electrode 93 in this way and the oxygen contained in the air flowing outside the air electrode 91 contribute to the cell reaction (the above-described reaction formulas A to C). The current on the fuel electrode side is taken out of the conductive tube 94 via the conductive felt 95.

By adopting such a structure, the interconnector can be omitted, and as a result, a cell resistant to thermal stress can be obtained.

[0010]

However, interconnect-less cells developed in this manner include:
The following issues remained. That is, in the case of the interconnectorless method, how to connect the electrodes and increase the current collection effect has not yet been sufficiently studied. As a current collecting structure of an interconnectorless cell, for example, as shown in FIG. 20, it has been considered that a plurality of cells are connected in parallel to form a bundle (Japanese Patent Laid-Open No. Hei 7-263001). Reference). this is,
Conductive tube 9 connected to anode 93 inside the cell
The ends of 4 are connected by a fuel distributor to form a cathode, the cathode 91 outside the cell is connected to each other by a conductive material 96, and a conductive plate 97 is provided on the side surface of the bundle. However, simply connecting the cathodes to each other with the conductive material 96 in this manner causes a current generated in a cell arranged at a position distant from the conductive plate 97 to pass through the conductive plate via a plurality of cells. 97, and the current collection efficiency is low.

In the case of the interconnector-less system,
Fuel flows inside the cell and air flows outside. Therefore, in order to connect the electrodes around the cells, it is necessary to connect the cells in a high-temperature oxidizing atmosphere, which causes difficult problems such as an increase in contact resistance and deterioration of the electrodes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a cathode current collecting structure used for a cylindrical solid electrolyte type fuel cell and a solid electrolyte type fuel using the cathode current collecting structure An object is to provide a battery power generation module.

[0013]

A cathode current collecting structure according to the present invention is an air electrode of an interconnectorless type solid electrolyte fuel cell in which an air electrode, a solid electrolyte, and a fuel electrode are sequentially stacked from the outside in a cylindrical shape. An exhaust gas separator that separates an air electrode side exhaust gas and a fuel electrode side exhaust gas at the upper end of the air electrode of the cylindrical fuel cell, which is a cathode current collecting structure for extracting a current, and is arranged to extend vertically. And a cathode current collector that is axially closely attached to the cylindrical fuel cell and extends above the exhaust gas separator.

According to the above configuration, since the air electrode current does not pass through another adjacent cell, the current collection efficiency is improved. Further, since the current flowing through the air electrode in the high-temperature oxidizing atmosphere is drawn into the reducing atmosphere, a conventional highly conductive metal can be used as the material of the air electrode-side power lead.

[0015] It is preferable that the cathode current collector is coated with a conductive material having resistance to the atmosphere in a portion below the exhaust gas separator which comes into contact with a high-temperature oxidizing atmosphere for a fuel cell reaction. Since the lead member in the exhaust on the air electrode side is in a high-temperature oxidizing atmosphere, deterioration of the cathode current collector can be prevented by covering the lead member with a substance that does not oxidize even in the high-temperature oxidizing atmosphere.

[0016] The cathode current collecting structure preferably further comprises a current collecting auxiliary provided between the cathode current collector and the air electrode, and the current collecting auxiliary is used for a fuel cell reaction. It is desirable to be formed of a material that is stable in a high-temperature oxidizing atmosphere and has a higher conductivity than the air electrode at the operating temperature.

Further, the cathode current collecting structure may include one or more current collecting auxiliary members provided around the air electrode so that an outer part thereof contacts the cathode current collector and an inner part thereof contacts the air electrode. Preferably, the device further comprises a ring, wherein the current collection auxiliary ring is stable in a high-temperature oxidizing atmosphere for a fuel cell reaction, and has a conductivity higher than the conductivity of the cathode at an operating temperature. It is desirable to be formed with.

In the case where the current collecting auxiliary agent and the current collecting auxiliary ring are provided, the current collecting effect can be further improved.

Next, a solid oxide fuel cell power module according to the present invention is a solid oxide fuel cell power module using the above-mentioned cathode current collecting structure, wherein the solid oxide fuel cells are arranged in parallel with each other. In a plurality of solid oxide fuel cell power generation modules, the exhaust gas separator plate, a fuel distributor for distributing fuel to a fuel supply pipe of the fuel cell, and one or more fuel outlets at a position above the exhaust gas separator plate. A fuel electrode side power lead connected to a fuel supply pipe; and an air electrode side power lead connected to one or more lead members at a position above the exhaust gas separator plate. I do.

Since the solid oxide fuel cell power generation module according to the present invention has the above configuration, the power collection efficiency is high, and the air electrode side power lead and the fuel electrode side power lead are connected in a reducing atmosphere. Therefore, the power lead can be made of a conventional highly conductive metal material, and the problem of increase in contact resistance and deterioration of the electrode is eliminated.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a cathode current collecting structure and a solid oxide fuel cell power generation module according to the present invention will be described below with reference to the accompanying drawings.

The cathode current collector structure Figure 1 shows an embodiment of a cathode current collector structure according to the present invention. As shown in FIG. 1, the cathode current flowing to the cathode arranged outside the cell is taken out from the cathode current collector 21 which is in close contact with the cathode of the cell. The cathode current collector 21 has a lead member 22 extending in the longitudinal direction of the cell. The lead member 22 can be formed of a highly conductive metal such as copper or nickel. Lead member 2
2 penetrates an exhaust gas separator 11 (see FIG. 9) provided to prevent mixed combustion of the air electrode side exhaust and the fuel electrode side exhaust. Therefore, one end of the lead member 22 is located during exhaust on the fuel electrode side, and the other end is located during exhaust on the air electrode side.

The portion of the lead member 22 which is being exhausted on the cathode side is connected to the cathode of the cell, whereby the cathode current is taken out. In the embodiment of FIG.
The lead member 22 is inserted between the two cells and connected to each cell. At a portion where the lead member 22 is connected to the air electrode, there is a coating layer 76 that covers the lead member. The coating layer 76 is made of a material such as platinum, which is stable in a high-temperature oxidizing atmosphere and has higher conductivity than the air electrode material. The lead member in the air electrode side exhaust is
Since the lead member 22 is in a high-temperature oxidizing atmosphere, the deterioration of the lead member 22 can be prevented by covering the lead member 22 with a substance which does not oxidize even in the high-temperature oxidizing atmosphere.

In order to enhance the current collecting effect on the air electrode 1, a current collecting auxiliary agent 23 is provided between the air electrode 1 and the coating layer 76. Further, at regular intervals around the air electrode 1, several millimeters to several tens millimeters in width are provided. It is preferable to coat the current collecting auxiliary ring 24 in advance. The current collecting auxiliary agent 23 and the current collecting auxiliary ring 24
For example, it is made of a material that is stable in a high-temperature oxidizing atmosphere such as a platinum paste and that has a higher conductivity than the air electrode material.

Since a large amount of current flows through the cathode current collector 21 at the top of the cell and is small at the bottom of the cell, the width of both the cathode current collector 21 and the current collection aid 23 can be reduced toward the bottom. As a result, the amount of material used can be reduced. It is desirable that the uncovered portion of the lead member 22 has flexibility such as a stranded wire structure to withstand thermal stress.

In the example using the cell of FIG. 1, a cathode current collector 21 is attached between cells arranged in a vertical direction,
The cathode spacer 25 is inserted between the cells arranged in the horizontal direction (see FIG. 2). The material of the cathode spacer 25 is preferably the same as the air electrode of the cell, and may not be electrically conductive.

The power module will be described interconnector-less cylindrical solid oxide fuel cell power generation module using the cathode current collector structure of the above.

(1) When using an interconnectorless cell of a type in which fuel is supplied from the upper part of the cell First, an embodiment of a solid oxide fuel cell power generation module according to the present invention is shown in FIG. 3 and FIG. The case where a single cell is used will be described as an example. FIG. 3 shows an example of a cell structure of a solid oxide fuel cell.
This cell has a cylindrical shape in which an air electrode 1, an electrolyte 2, and a fuel electrode 3 are stacked in this order from the outside, and has a structure in which the bottom of the cell is closed. Inside the fuel electrode 3, a fuel supply pipe 4 is inserted from the upper side of the cell. A conductive felt 5 is packed between the fuel electrode 3 and the fuel supply pipe 4 to electrically connect the fuel electrode 3 and the fuel supply pipe 4. The fuel supply pipe 4 is used for the cathode of the cell, and the air electrode 1 is used for the anode.

Inside the fuel supply pipe 4, there is provided a water vapor thin tube 6. The steam narrow tube 6 is for steam-reforming a fuel containing methane as a main component (natural gas or the like) into a gas rich in hydrogen and carbon monoxide that can be used as a fuel for a fuel cell. The steam tube 6 is located on the bottom side of the cell.
More steam can be supplied. By increasing the amount of steam supplied from the steam tube 6 toward the bottom of the cell, the steam concentration from the top to the bottom of the conductive felt 5 can be made uniform. As a result, it is possible to prevent carbon deposition due to insufficient water vapor at the bottom of the cell, and to prevent dilution of hydrogen and carbon monoxide resulting from excessive supply of water vapor at the top of the cell.

FIG. 4 shows the structure of the fuel supply pipe 4 and the water vapor thin tube 6. Small holes 7 and 15 for discharging fuel are provided at the tip and side surfaces of the fuel supply pipe 4. The size, number, and position of the holes 15 on the side surface are provided so that the fuel can be evenly distributed on the surface of the fuel electrode 3. The hole 15 is formed in the fuel supply pipe 4 so as to be inclined toward the upper part of the cell, so that the fuel gas (especially the fuel gas at the bottom of the cell) ejected from the hole does not stay in the cell, and the cell 15 smoothly flows. So that it is exhausted outside. The fuel is supplied to the fuel supply pipe 4 at a pressure of, for example, about 0.5 to 3 kg / cm ² · G, and is blown out from the hole 15 on the side surface of the fuel supply pipe and the fuel outlet 7 at the tip.

At the position of the fuel outlet 7 provided at the tip of the fuel supply pipe 4, a steam outlet 8 of the steam tube 6 is arranged. The upper end of the steam tube 6 is fixed to a hole formed in the upper portion of the fuel supply tube 4 by welding or the like.

With the ejection of the fuel from the fuel supply pipe 4, a negative pressure is generated in the vicinity of the fuel outlet 7, and steam is drawn from the steam outlet 8. Steam is extracted from the steam outlet 8 by such an ejector effect, and new steam is correspondingly sucked into the steam tube 6 through the steam inlet 9. Fuel electrode side exhaust is used for new steam. Exhaust gas separator plate 11 at the top of the cell
Is attached, only the fuel electrode side exhaust flows around the steam inlet 9 and the air electrode side exhaust 12 does not pass around the steam inlet 9 (see FIG. 3). Therefore, only the fuel electrode side exhaust is sucked into the water vapor thin tube 6. As a result, it is possible to effectively use the steam in the fuel electrode side exhaust again as steam for reforming without providing an external circulation route.

Since the SOFC operates at a high temperature, if the position of the fuel outlet 7 at the tip and the position of the steam outlet 8 are shifted due to thermal expansion or the like, the ejector effect is adversely affected. It is desirable to fix the fuel supply pipe 4 and the water vapor thin tube 6 by performing the above-described steps. Further, in order to prevent the water vapor thin tube 6 from swinging, it is preferable to provide a swing stopper 13 as shown in FIG. Anti-sway bracket 13
Is fixed to the steam tube by welding or the like.

Conventional materials can be used for the material of the air electrode 1, and for example, strontium-added lanthanum manganite and the like can be used. In addition, as a material of the electrolyte 2, for example, yttria-stabilized zirconia or the like can be used. As a material of the fuel electrode 3, for example, nickel zirconia cermet or the like can be used. As a material of the fuel electrode 3, it is preferable to use a material having a catalytic function of fuel reforming such as natural gas, such as nickel zirconia cermet. The material of the fuel supply pipe 4 needs to be a material having high conductivity and sufficient strength against the internal fuel gas pressure even at a high temperature of 1000 ° C.
Preferably, a metal material such as nickel, copper, stainless steel, and Inconel is used. Preferably, the material of the fuel supply pipe 4 is one having catalytic performance for reforming the fuel. The material of the steam tube 6 is preferably the same as the material of the fuel supply tube 4 from the viewpoint of the consistency of the coefficient of thermal expansion with the fuel supply tube 4 and the consistency at the time of welding.

As described above, the fuel supply pipe 4 and the water vapor thin tube 6 are formed of a conductive metal material, whereas the cells are formed of a ceramic material.
A shift occurs due to a temperature change due to start-stop. In order to absorb this deviation, it is preferable to provide a sliding part in a part of the fuel supply pipe 4 and a part of the water vapor thin tube 6 as shown in FIG.

Next, the flow path for fuel and the like will be described with reference to FIGS. Fuel such as natural gas flows from the upper part of the cell through the fuel supply pipe 4 to the ejector part (tip part) provided at the lower part of the cell. A part of the fuel is blown into the conductive felt 5 from the hole 15 provided on the side surface of the fuel supply pipe 4 before reaching the ejector portion. The fuel that has reached the ejector section is ejected from the fuel ejection port 7. The steam sucked from the steam inlet 9 by the ejector effect at this time is released from the steam outlet 8. The fuel and steam that have exited the ejector section enter the conductive felt 5 and are reformed. On the other hand, air containing oxygen flows outside the cell, and the oxygen receives electrons and is ionized (reaction formula A), passes through the electrolyte, and reaches the fuel electrode 3. On the fuel electrode side, oxide ions react with hydrogen and carbon monoxide in the conductive felt 5 while emitting electrons (reaction formulas B and C). The water vapor and carbon dioxide generated by this reaction flow in the conductive felt 5 toward the upper part of the cell. Then, the steam generated by the reaction formula B again contributes to the reforming reaction. An exhaust gas separator plate 11 is provided on the upper part of the cell, and the steam or the like discharged from the conductive felt 5 becomes the fuel electrode side exhaust without being mixed with air. A part of the fuel electrode side exhaust is taken in from the steam inlet 9 in the upper part of the cell and flows toward the lower part of the cell as steam for reforming.

Next, connection of cells will be described. The connection between the cells is performed by connecting a plurality of cells via the cathode current collector 21 shown in FIG. 1 in the vertical direction and the cathode spacer 25 in the horizontal direction on the paper of FIG. , Constitute one bundle. Cathode spacer 25
Extends to a position slightly lower than the upper end of the cell so as to form a gap above the cell so that air flowing between the cells is exhausted.

FIG. 5 shows an example of the bundle structure.
Here, a bundle structure in which a total of six cells are connected, two in the vertical direction and three in the horizontal direction, is shown. Air is supplied to the cell through holes in the bottom air chamber separator plate 26 and rises up the cell along the outer cathode. The cathode side exhaust and the fuel side exhaust coming out from inside the cell are
The exhaust gas is separated by the exhaust gas separator plate 11 so as not to mix and burn. The exhaust gas separator plate 11 is provided with a through hole 27 through which the cathode current collector 21 passes.

A bundle spacer 28 is provided between the bundles to electrically insulate the bundles from each other and to provide a gap between the bundle and the exhaust gas separator plate 11 so as to provide a passage for the air electrode side exhaust. Provide. Therefore, as shown in FIG. 6, the air electrode side exhaust between the cells is caused by the bundle spacer 28 in the lateral direction on the paper of FIG.
From the upper part of the cathode spacer 25 in the vertical direction.

FIG. 6 is a plan view showing a case where four bundles shown in FIG. 5 are connected in a vertical direction to form a stack. Six cells connected in parallel as described above constitute each bundle. There is a bundle spacer 28 between each bundle, and in this state, bundles 1 to 4
Are insulated from each other.

FIG. 7 shows how to take out the electrodes from the bundle. On the fuel electrode side (cathode), the fuel supply pipe 4 serves as a current collector. Therefore, the fuel electrode (cathode) side can extract electricity from the fuel supply pipe 4 through the fuel electrode side power lead 29. The air electrode (anode) side extracts electricity from the cathode current collector 21 through the air electrode side power lead 30. By connecting the fuel electrode side power lead 29 to the six fuel supply pipes 4, the cathodes of the cells are connected in parallel and become equipotential. In addition, the air electrode side power lead 3
By connecting the three cathode current collectors 21 by 0, the anodes of the cells are also connected in parallel and become equipotential.

Each fuel supply pipe 4 and fuel electrode side power lead 2
9, and the cathode current collector 21 and the air electrode side power lead 30 are firmly fixed by welding, bolting or the like so as not to increase the contact resistance. It is desirable that each power lead has flexibility by using a stranded wire structure or the like.

As shown in FIG. 8, the electrical connection between the bundles is performed by connecting the air electrode side power lead 30 and the fuel electrode side power lead 29 of the adjacent bundle by welding or bolting. In this way, the bundles are electrically connected in series. The connection of the power lead is performed after the cell is covered with the exhaust gas separator plate 11.

FIG. 9 shows an example of a stack structure.
This is obtained by connecting four bundles shown in FIG. 5 in series in the vertical direction. The fuel is sent from the fuel distributor 31 through the flexible insulating joint 32 and the fuel supply pipe 4 to the inside of the cell. The stacks are partitioned by a partition board 33. For the sake of clarity, the power lead on the air electrode side and the power lead on the fuel electrode side (power lead assembly)
Is omitted.

FIG. 10 shows a flexible insulating joint 3.
2 shows the connection between the fuel supply pipe 2 and the fuel supply pipe 4 in an enlarged manner. Fuel supply pipe 4 and fuel distributor 31
And are connected by a flexible insulating joint 32. As shown in FIG. 10, the flexible insulating joints 32 can be connected to each other by screwing. If the flexible insulating joint 32 has a flexible structure, even if the cells and the power generation module have different thermal stresses and different expansion coefficients, the sliding caused by the differences can be absorbed. The flexible insulating joint 32 is formed of an insulating material such as ceramics or Teflon, and is connected to the fuel supply pipe 4 and the fuel distributor 31.
Can be electrically isolated from each other.

FIG. 11 shows an embodiment of the power generation module constructed by further connecting the stack shown in FIG. 9 in series.
Shown in In the power generation module, the air chamber 3
4. A battery reaction chamber 35, a fuel electrode exhaust gas chamber 36, and a fuel distributor 31 are provided. Air chamber 34
The cell reaction chamber 35 is partitioned by the air chamber separator plate 26, and the cell reaction chamber 35 and the fuel electrode exhaust gas chamber 36 are partitioned by the exhaust gas separator plate 11. Further, a top plate 37 for supporting the fuel distributor 31 is attached between the fuel distributor 31 and the fuel electrode exhaust gas chamber 36.

The air entering the air chamber 34 is blown upward from a hole provided in the air chamber separator plate 26,
After contributing to the battery reaction in the battery reaction chamber 35, it is discharged as air electrode side exhaust. On the other hand, fuels such as natural gas
The fuel is distributed to each cell by the fuel distributor 31, supplied to the fuel supply pipe 4 of each cell via the flexible insulating joint 32, and enters the battery reaction chamber 35. After the fuel contributes to the reforming and the battery reaction in the cell reaction chamber 35, the fuel enters the fuel electrode exhaust gas chamber 36 as fuel electrode side exhaust. Part of this is sucked through the steam inlet 9 and again contributes to the reforming reaction. The other fuel electrode side exhaust is discharged outside the fuel electrode exhaust gas chamber 36.

Between the anode exhaust gas chamber 36 and the battery reaction chamber 35, the anode exhaust gas chamber 36 is controlled by a differential pressure control.
And the gas pressure difference between the battery reaction chamber 35 and the battery reaction chamber 35 are preferably eliminated. By eliminating the pressure difference, mixed combustion due to gas leakage from between the exhaust gas separator plate 11 and the cell can be suppressed, and a special seal between the exhaust gas separator plate 11 and the upper part of the cell can be eliminated. Further, the flammable gas in the fuel electrode side exhaust gas that has risen to the upper part of the cell is almost consumed by the battery reaction, so that a slight leak is allowed.

(2) In the case where an interconnector-less cell of a type in which fuel is supplied from the lower part of the cell is used. Next, an embodiment of a solid oxide fuel cell power generation module according to the present invention is shown in FIG. An example in which a single cell is used will be described. FIG. 12 shows an example of a cell structure of a solid oxide fuel cell. This cell is a cylindrical cell in which an air electrode, a solid electrolyte, and a fuel electrode are sequentially arranged from the outside. A cylindrical air electrode 51, an electrolyte 52, and a fuel electrode 53 are coaxially laminated on the inside, and a conductive tube 54 for supplying natural gas and water vapor is inserted inside the fuel electrode 53. A conductive felt 55 is provided between the conductive tube 54 and the anode 53.
(For example, nickel felt or the like), and electrically connects the fuel electrode 53 and the conductive tube 54. An air electrode 51 is used for the anode of the cell, and a conductive tube 54 is used for the cathode.

The conductive tube 54 has a double structure with a cross-section in part, and natural gas is supplied to the inside and steam is supplied to the outside. The natural gas and water vapor supplied to the conductive tube 54 are blown outward from a number of pores provided in the conductive tube 54 and enter the conductive felt 55. Here, natural gas (mainly composed of methane) and steam are reformed into a fuel that contributes to the cell reaction.

On the other hand, air is supplied outside the cell, and oxygen in the air receives electrons at the air electrode 51 and is ionized (reaction formula A). Oxide ions generated at the air electrode 51 reach the fuel electrode 53 through the electrolyte 52. At the fuel electrode 53, oxide ions supplied through the electrolyte 52 react with hydrogen and carbon monoxide generated by reforming to release electrons (reaction formulas B and C).

[0052] generated in the fuel electrode 53 by cell reaction H ₂
Battery reaction between H ₂ O (steam), reforming and CO (reaction formula C)
And CO ₂ made by, while remaining of H ₂ unreacted is discharged from the top of the cell outside the cell. It should be noted that almost all of the fuel CO produced by the reforming contributes to the cell reaction (reaction formula C), and thus is scarcely contained in the exhaust gas.

On the top side (top) of the cell, the steam generated by the battery reaction (reaction formulas A and B) again contributes to the reforming reaction, and therefore, from the base side (bottom) to the top side (top) of the cell.
If the water vapor is supplied uniformly between them, the water vapor becomes excessive on the distal side and insufficient on the proximal side. By making only a part of the base end side of the conductive tube 54 a double structure, the fuel concentration can be made uniform and the cell performance can be improved.

FIG. 13 shows a solid oxide fuel cell power generation module using such cells. Cell 5
6 is accommodated in a casing 57. Casing 5
Near the upper end (upper part) of the fuel cell 7, an anode exhaust gas chamber 58 above the cell 56, and a battery reaction chamber 59 existing around the cell from near the lower end (bottom) to near the upper end (upper part) of the cell. An exhaust gas separator plate 60 to be separated is provided.

As shown in FIG. 13, a fuel electrode side exhaust port 61 is provided at an upper portion of the casing 57.
Further, on the side wall of the casing 57, an air supply port 62 is provided at a height immediately below the cell 56, and an air electrode side exhaust port 63 is provided immediately below the exhaust gas separator plate 60. The air that has entered through the air supply port 62 is blown upward from the air outlet of the air chamber separator plate 64. Oxygen in the air contributes to the battery reaction in the battery reaction chamber 59 and is consumed, and the remaining oxygen is used together with other components in the air in the air electrode side exhaust port 63.
From the power generation module 65.

On the other hand, the natural gas and the steam supplied from the natural gas supply passage 66 and the steam supply passage 67 are distributed to each cell 56 by the fuel distributor 68, reformed in each cell 56, and then subjected to the battery reaction. To contribute. Thereafter, the hydrogen not contributing to the cell reaction, the water vapor generated by the cell reaction, and the carbon dioxide generated by the reforming enter the anode exhaust gas chamber 58 from the upper end of the cell 56, and enter the casing 57 through the anode-side exhaust port 61. It is discharged outside.

A part of the fuel electrode side exhaust gas is recirculated to the steam supply passage 67 via the pump 69 and the flow controller 70. Since the fuel electrode side exhaust contains a large amount of pure steam, a part of the fuel electrode side exhaust is
It has been returned to 7.

FIG. 14 shows a basic bundle structure in which a plurality of cells shown in FIG. 12 are bundled. The conductive tube 54 of each cell is connected to a fuel distributor 68 via a flexible joint 71. The flexible joint 71 and the fuel distributor 68 are, for example, iron, copper, nickel, stainless steel,
It is formed of a conductive material such as Inconel, and a conductive tube 54 serving as a cathode of each cell is electrically connected in parallel. An insulating joint 72 is provided on the base end side of the fuel distributor 72. A fuel electrode-side power lead 73 is drawn out from the distal end side of the conductive tube.

The cathode current collector 21 shown in FIG. 1 is inserted between the cells, and is connected to the air electrode side power lead 74. Power lead 7 for each air electrode
4 is connected to the fuel electrode side power lead 73 of the adjacent bundle. Therefore, in this embodiment, six cells of each bundle are connected in parallel, and each bundle is connected in series.

FIG. 15 shows a stack in which a plurality of the bundle structures shown in FIG. 14 are arranged.
The stack is configured by connecting the air electrode side power lead 74 and the fuel electrode side power lead 73 of each bundle in series. In this figure, the exhaust gas separator plate 6
0 is omitted. The power generation module shown in FIG. 13 is configured by arranging a plurality of stacks shown in FIG.

[0061]

The cathode current collecting structure according to the present invention and the solid oxide fuel cell power generation module using the cathode current collecting structure have the above-described structure, and therefore have the following effects.

The cathode current collecting structure according to the present invention has a high current collecting efficiency because the current of the cell does not pass through another adjacent cell, and the current flowing through the air electrode in a high-temperature oxidizing atmosphere is reduced in a reducing atmosphere. Since it is pulled out, a conventional highly conductive metal can be used as the material of the air electrode side power lead.

Further, if a current collecting auxiliary or a current collecting auxiliary ring is coated between the cathode current collector and the air electrode, the current collecting effect can be further improved.

Next, since the solid oxide fuel cell power generation module according to the present invention utilizes the cathode current collecting structure having the above-mentioned effects, the current collecting efficiency is high, and the air electrode side power lead and the fuel electrode Since the side power leads are also connected in a reducing atmosphere, the power leads can be made of a conventional highly conductive metal material, and are free from the problems of increased contact resistance and electrode deterioration.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a cathode current collecting structure according to the present invention.

FIG. 2 is a plan view showing a state where adjacent cells are connected using the cathode current collecting structure shown in FIG.

FIG. 3 is a cross-sectional view showing an example of a cell that can use the cathode current collecting structure shown in FIG.

FIG. 4 is a diagram showing a fuel supply pipe and a steam capillary of the cell shown in FIG. 3;

FIG. 5 shows a cathode current collecting structure shown in FIG. 1 and FIG.
FIG. 3 is a perspective view showing an example of a bundle constituted by the cells shown in FIG.

FIG. 6 is a plan view showing a state where a plurality of bundles shown in FIG. 5 are arranged.

FIG. 7 is a perspective view showing a structure for connecting the electrodes of the cell shown in FIG. 3 using the cathode current collecting structure shown in FIG. 1;

FIG. 8 is a perspective view showing electrode connections between the bundles shown in FIG. 5;

FIG. 9 is a perspective view illustrating an example of a stack configured by arranging a plurality of bundles illustrated in FIG. 5;

FIG. 10 is an enlarged perspective view of the flexible insulating joint shown in FIG. 9;

FIG. 11 is a sectional view showing one embodiment of a solid oxide fuel cell power generation module according to the present invention.

FIG. 12 is a cross-sectional view showing another example of a cell in which the cathode current collecting structure shown in FIG. 1 can be used.

FIG. 13 is a sectional view showing another embodiment of the solid oxide fuel cell power generation module according to the present invention.

14 is a perspective view showing an example of a bundle formed by using the cathode current collecting structure shown in FIG. 1 and the cell shown in FIG.

15 is a perspective view showing an example of a stack in which a plurality of bundles shown in FIG. 14 are arranged.

FIG. 16 is a perspective view showing a conventional vertical stripe cylindrical solid electrolyte fuel cell.

FIG. 17 is a perspective view showing an installed state of the cell shown in FIG. 16;

FIG. 18 is a plan view showing a connection structure of electrodes in a conventional vertical stripe cylindrical cell.

FIG. 19 is a perspective view showing an interconnectorless solid oxide fuel cell.

FIG. 20 is a plan view showing a conventional electrode connection structure of an interconnectorless cell.

[Explanation of symbols]

 1, 51, 81, 91 Air electrode 2, 52, 82, 92 Electrolyte 3, 53, 83, 93 Fuel electrode 4 Fuel supply pipe 5, 55, 95 Conductive felt 6 Steam thin tube 11, 60 Exhaust gas separator plate 21 Cathode collection Electric body 22 Lead member 23 Current collecting auxiliary agent 24 Current collecting auxiliary ring 76 Coating layer 25 Cathode spacer 29, 73 Fuel electrode side power lead 30, 74 Air electrode side power lead 35, 59 Battery reaction chamber 36, 58 Fuel electrode side exhaust gas Room

Claims (5)

[Claims] 1. A cathode current collecting structure for extracting an air electrode current of an interconnector-less type solid electrolyte fuel cell in which an air electrode, a solid electrolyte, and a fuel electrode are sequentially stacked from the outside in a cylindrical shape, An exhaust gas separator that separates an air electrode-side exhaust gas and a fuel electrode-side exhaust gas at the upper end of the air electrode of the cylindrical fuel cell that is disposed so as to extend in the axial direction; And a cathode current collector extending above the exhaust gas separator. 2. The cathode current collector according to claim 1, wherein a portion below the exhaust gas separator in contact with a high-temperature oxidizing atmosphere for a fuel cell reaction is coated with a conductive material having resistance to the atmosphere. The cathode current collecting structure according to claim 1, wherein 3. The fuel cell system further comprises a current collecting auxiliary provided between the cathode current collector and the air electrode, wherein the current collecting auxiliary is stable in a high-temperature oxidizing atmosphere for a fuel cell reaction. 3. The cathode current collecting structure according to claim 1, wherein the cathode current collecting structure is formed of a substance having a higher conductivity than an air electrode at an operating temperature. 4. The device further comprises one or more current collection auxiliary rings provided around the air electrode so as to contact the cathode current collector at a part of an outer side and to contact the air electrode at an inner side, The current collection auxiliary ring is characterized by being formed of a material that is stable in a high-temperature oxidizing atmosphere for a fuel cell reaction and has a conductivity higher than that of an air electrode at an operating temperature. The cathode current collecting structure according to claim 1. 5. A solid oxide fuel cell power generation module using the cathode current collecting structure according to claim 1, wherein a plurality of the solid oxide fuel cells are arranged in parallel with each other. In the electrolyte fuel cell power generation module, the exhaust gas separator plate, a fuel distributor that distributes fuel to a fuel supply pipe of the fuel cell, and one or more fuel supply pipes at a position above the exhaust gas separator plate. A solid electrolyte type comprising: a fuel electrode side power lead connected thereto; and an air electrode side power lead connected to one or more lead members at a position above the exhaust gas separator plate. Fuel cell power generation module.