JP5569868B2 - Fuel cell body, fuel cell unit, fuel cell stack, and fuel cell including them - Google Patents

Description

  The present invention relates to a fuel cell body used in a solid oxide fuel cell (SOFC), a fuel cell unit, a fuel cell stack, and a fuel cell including them, and more particularly, a tubular fuel cell. The present invention relates to a fuel cell unit having cells, a fuel cell unit, a fuel cell stack, and a fuel cell including them.

  Conventionally, a fuel cell unit having a tubular fuel cell is known (see, for example, Patent Document 1). The fuel cell unit disclosed in Patent Document 1 has a current collecting terminal made of metal at the end of the fuel cell, and a conductive sealing material, that is, a metal brazing material, is exposed on the exposed surface of the inner electrode. (16a) and the current collecting terminal are arranged to be connected.

JP 2008-71712 A

  In such a case, when the electrode on the side surface of the cell end and the current collecting terminal are connected by brazing, the current is collected with a metal brazing material interposed only between the side surface of the cell end and the inner surface of the current collecting terminal. Electrical terminals were attached and then brazed by heating.

However, since the internal electrode is ceramic, the wettability of the metal brazing material is generally poor. For this reason, a phenomenon called “sink” occurs in the brazing process, and a part of the electrode on the side surface of the cell edge does not get wet with the brazing material, and the brazing material may move from the exposed portion of the electrode. It was. If the “sinking” of the brazing material occurs, the electrical contact area between the electrode and the current collecting terminal varies and the current collecting performance deteriorates. In the worst case, the electrical connection may be interrupted and gas leakage may occur. There was also.

  SUMMARY OF THE INVENTION The present invention provides a fuel cell unit, a fuel cell unit, a fuel cell stack, and a fuel cell including them, in which a current collecting terminal can be securely brazed and fixed.

In order to achieve the above object, a fuel cell unit according to the present invention used for a fuel cell is arranged in a tubular shape so as to cover a tubular inner electrode layer that forms a fuel gas flow path therein and the inner electrode layer. An outer electrode layer, and an electrolytic layer disposed in a tubular shape between the inner electrode layer and the outer electrode layer, and an end portion of the inner electrode layer is formed with respect to the electrolytic layer and the outer electrode layer. and the outer peripheral surface of the exposed tubular fuel cell of the tubular and a end face of the axial direction of the tubular, both the covering Utotomoni said end face of said outer peripheral surface and the end surface of the inner electrode layer In the fuel cell unit comprising a flow path communicating with the fuel gas flow path in the center and a current collecting terminal joined to the outer peripheral surface of the inner electrode layer by brazing, the brazing is , Electricity between the inner electrode layer and the current collecting terminal It is made of a brazing material of a metal material that secures connection and prevents leakage of fuel gas between the inner electrode layer and the current collecting terminal, and the brazing material is the current collecting terminal and the outer peripheral surface. Between the current collector and the current collector terminal and the end face .

In the fuel cell unit configured as described above, the brazing material is disposed in an integrated state from between the current collecting terminal and the outer peripheral surface to between the current collecting terminal and the end surface . When the wax is melted, the brazing material that has become liquid is prevented from moving from the exposed electrode due to “sink”. As a result, it is possible to stably perform the bonding between the electrode and the inner surface of the current collecting terminal, and it is possible to prevent variations in electrical contact area, electrical connection interruption, and gas leakage.

More specifically , in the brazing process, the brazing material between the current collecting terminal and the end face that became liquid when the solder was melted functions as priming water, and is disposed between the current collecting terminal and the outer peripheral surface and is also liquid. the Carlo c material, held in the vicinity of the cell edge. As a result, the brazing material between the collector terminal and the outer peripheral surface became liquid, it would move by a "sink" can be prevented from the exposed electrodes. Further, since the cell end surface functions as an electrical contact surface, stable current collecting performance can be exhibited.

In addition, since the brazing material between the current collecting terminal and the outer peripheral surface and the brazing material between the current collecting terminal and the end surface are the same material, each brazing material is easy to become familiar with when brazing in the brazing process. Demonstrate. That is, when the solder is melted, the brazing material between the current collecting terminal and the outer peripheral surface and the brazing material between the current collecting terminal and the end surface are likely to be integrated, and the brazing material between the current collecting terminal and the end surface is surely secured. Since it functions as a priming water, “sinks” can be prevented.

In the embodiment of the fuel cell unit according to the present invention, preferably, the brazing material is arranged on the entire circumference of the end face.

In the fuel cell unit configured as described above, the brazing material between the current collecting terminal and the outer peripheral surface and the brazing material between the current collecting terminal and the end surface are connected all around the end surface of the fuel cell. Therefore, the brazing material between the current collecting terminal and the outer peripheral surface is held over the entire periphery of the cell end, and the occurrence of gas leak can be reliably prevented .

  In order to achieve the above object, a fuel cell according to the present invention includes the above-described fuel cell unit.

  As described above, the fuel cell body, the fuel cell unit, the fuel cell stack and the fuel cell including them according to the present invention provide a highly reliable fuel cell while maintaining stable current collecting performance. be able to.

1 is an overall configuration diagram showing a solid state electric reforming fuel cell (SOFC) according to an embodiment of the present invention. It is sectional drawing which shows the fuel cell module of the solid electric reforming type fuel cell (SOFC) by embodiment of this invention. It is sectional drawing along the III-III line of FIG. It is a fragmentary sectional view showing a fuel cell unit of a solid electric reforming fuel cell (SOFC) according to a conventional form. FIG. 6 is a cross-sectional view showing a state where an inner electrode layer and a current collecting terminal are ideally connected by a metal brazing material in a solid state electric reforming fuel cell (SOFC) according to a conventional form. FIG. 10 is a cross-sectional view showing a state in which a “sink” of a metal brazing material has occurred in a conventional fuel cell unit. FIG. 6 is a cross-sectional view showing a state in which “sink marks” of a metal brazing material are generated over the entire circumference in a fuel cell unit according to a conventional form. In the fuel cell unit concerning the embodiment of the present invention, it is a sectional view showing the state before current collection terminal wearing. It is sectional drawing which shows the state which has arrange | positioned the metal brazing material in the current collection terminal which concerns on embodiment of this invention. It is a perspective view which shows a mode that a metal brazing material is arrange | positioned in the current collection terminal which concerns on embodiment of this invention. In the fuel cell unit according to the embodiment of the present invention, it is a cross-sectional view showing a state where a current collecting terminal is attached to the fuel cell. It is sectional drawing which shows the state which the brazing process was completed in the fuel cell unit which concerns on embodiment of this invention.

Next, a solid oxide fuel cell (SOFC) according to an embodiment of the present invention and a fuel cell assembly used in the SOFC will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to a first embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell (SOFC) 1 according to a first embodiment of the present invention includes a fuel cell module 2 and an auxiliary unit 4.

  The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed in the housing 6 via a heat insulating material (not shown). In addition, you may make it not provide a heat insulating material. A fuel cell assembly 12 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14, and the fuel cell stack 14 includes 16 fuel cell units 16. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant (air) ) And combusted to generate exhaust gas.
Further, a reformer 20 for reforming the fuel gas is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which a reforming reaction can be performed by the combustion heat of the remaining fuel gas. doing. Further, an air heat exchanger 22 for receiving combustion heat and heating power generation air is disposed above the reformer 20.

  Next, the auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as tap water and uses the filter to obtain pure water, and a water flow rate that adjusts the flow rate of the water supplied from the water storage tank. An adjustment unit 28 (such as a “water pump” driven by a motor) is provided. The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from an air supply source 40, and a reforming air flow rate adjustment unit 44 that adjusts the flow rate of air (driven by a motor " An air blower "and the like, a power generation air flow rate adjustment unit 45 (such as an" air blower "driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a power generation chamber And a second heater 48 for heating the second power generation air supplied to the power generator. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

Next, a hot water production apparatus 50 to which exhaust gas is supplied is connected to the fuel cell module 2. The hot water production apparatus 50 is supplied with tap water from the water supply source 24, and the tap water is heated by the heat of the exhaust gas and supplied to a hot water storage tank of an external hot water heater (not shown).
The fuel cell module 2 is provided with a control box 52 for controlling the amount of fuel gas supplied and the like.
Furthermore, the fuel cell module 2 is connected to an inverter 54 that is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module to the outside.

Next, the internal structure of a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view showing a fuel cell module of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line III-III in FIG.
As shown in FIGS. 2 and 3, in the sealed space 8 in the housing 6 of the fuel cell module 2, as described above, the fuel cell assembly 12, the reformer 20, and the air heat exchange are sequentially performed from below. A vessel 22 is arranged.

  The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In addition, in the reformer 20, an evaporation unit 20a and a reforming unit 20b are formed in order from the upstream side, and the reforming unit 20b is filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 20 are reformed by the reforming catalyst filled in the reformer 20. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

  A fuel gas supply pipe 64 is connected to the downstream end side of the reformer 20, and the fuel gas supply pipe 64 extends downward and further in an manifold 66 formed below the fuel cell assembly 12. It extends horizontally. A plurality of fuel supply holes 64 b are formed in the lower surface of the horizontal portion 64 a of the fuel gas supply pipe 64, and the reformed fuel gas is supplied into the manifold 66 from the fuel supply holes 64 b.

  A lower support plate 68 having a through hole for supporting the fuel cell stack 14 described above is attached above the manifold 66, and the fuel gas in the manifold 66 flows into the fuel cell unit 16. Supplied.

  Next, an air heat exchanger 22 is provided above the reformer 20. The air heat exchanger 22 includes an air aggregation chamber 70 on the upstream side and two air distribution chambers 72 on the downstream side. The air aggregation chamber 70 and the air distribution chamber 72 include six air flow path tubes 74. Connected by. Here, as shown in FIG. 3, three air flow path pipes 74 form a set (74a, 74b, 74c, 74d, 74e, 74f), and the air in the air collecting chamber 70 is in each set. It flows into each air distribution chamber 72 from the air flow path pipe 74.

The air flowing through the six air flow path pipes 74 of the air heat exchanger 22 is preheated by exhaust gas that burns and rises in the combustion chamber 18.
An air introduction pipe 76 is connected to each of the air distribution chambers 72, the air introduction pipe 76 extends downward, and the lower end side communicates with the lower space of the power generation chamber 10, and the air that has been preheated in the power generation chamber 10. Is introduced.

Next, an exhaust gas chamber 78 is formed below the manifold 66. Further, as shown in FIG. 3, an exhaust gas passage 80 extending in the vertical direction is formed inside the front surface 6 a and the rear surface 6 b which are surfaces along the longitudinal direction of the housing 6, and the upper end of the exhaust gas chamber passage 80 is formed. The side communicates with the space in which the air heat exchanger 22 is disposed, and the lower end side communicates with the exhaust gas chamber 78. Further, an exhaust gas discharge pipe 82 is connected to substantially the center of the lower surface of the exhaust gas chamber 78, and the downstream end of the exhaust gas discharge pipe 82 is connected to the above-described hot water producing apparatus 50 shown in FIG.
As shown in FIG. 3, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.

Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 4 is a partial cross-sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to a conventional embodiment.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and a current collecting terminal 86 connected to each end of the fuel cell 84 in the vertical direction.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolytic layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

  Since the current collecting terminals 86 attached to the upper end side and the lower end side of the fuel cell unit 16 have the same structure, here, the current collecting terminals 86 attached to the upper end side will be specifically described. The end portion 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an end surface 90 c exposed to the electrolytic layer 94 and the outer electrode layer 92. That is, the inner electrode layer 90 is exposed at the outer peripheral surface 90b and the end surface 90c, which are the side surfaces of the fuel cell unit 16, respectively. The current collecting terminal 86 is connected to the outer peripheral surface 90 b of the inner electrode layer 90 through the metal brazing material 96, and is further in direct contact with the end surface 90 c of the inner electrode layer 90, thereby electrically connecting the inner electrode layer 90. It is connected. The current collecting terminal 86 includes a protruding cylindrical portion 86a and a flat surface 86b, and a fuel gas channel 98 communicating with the fuel gas channel 88 of the inner electrode layer 90 is formed inside the cylindrical portion 86a. Has been.

  The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolytic layer 94 includes, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

  FIG. 5 is a cross-sectional view showing a state in which the connection between the inner electrode layer 90 and the current collecting terminal 86 is ideally performed by the metal brazing material 96 in the solid state reforming fuel cell (SOFC) according to the conventional form. FIG. In the drawing, the entire outer peripheral surface 90 b of the inner electrode layer 90 is joined to the current collecting terminal 86 in a state where it is wetted by the metal brazing material 96. If it is joined in such a state, the electrical connection between the inner electrode layer 90 and the current collecting terminal 86 is stable and uniform, and the fuel gas passing through the fuel gas flow path 88 flows out to the outside. The route can be blocked reliably.

However, in the conventional fuel cell unit 16, an ideal connection as shown in FIG. 5 is rarely made. Actually, as shown in FIG. 6, the metal brazing material moves away from the corner portion 100 of the end surface 90 c of the inner electrode phase 90 due to sink marks of the metal brazing material generated in the process of joining with the metal brazing material. In many cases, a part or the whole of the outer peripheral surface 90b is joined to the current collecting terminal 86 in a state where it is not wet with the metal brazing material.
In such a state, in addition to the possibility that the fuel gas passing through the fuel gas flow path 88 flows out to the outside, there is a possibility that the electrical connection between the inner electrode layer 90 and the current collecting terminal 86 is the cell. It will vary from time to time. The inner electrode layer 90 is electrically connected also by direct contact with the end surface 90c, but the connection state is unstable, and the inner electrode layer 90 is not connected in the brazing process. In some cases. As a result, as shown in FIG. 7, “sinking” of the metal brazing material occurs over the entire circumference, and even when the electrical connection between the inner electrode layer 90 and the current collecting terminal 86 cannot be secured.

  Hereinafter, the structure of the fuel cell unit 16 according to the embodiment of the present invention will be described with reference to FIGS. 8 to 12. FIG. 8 is a cross-sectional view showing a state before the current collector terminal 86 is mounted in the fuel cell unit 16 according to the embodiment of the present invention. A paste-like metal brazing material 96a (first brazing material) is applied to a portion of the side surface of the end portion 90a of the fuel cell unit 16 that faces the inner peripheral surface of the current collecting terminal 86. This is the same as the fuel cell unit 16 according to the conventional configuration.

  Conventionally, the current collector terminal 86 is attached to the fuel cell unit 16 in the state shown in FIG. On the other hand, in this embodiment, as shown in FIGS. 9 and 10, a plate-shaped metal brazing material 96b (second brazing material) formed in a disk shape by forming a through hole in the center is used as a current collecting terminal. After being arranged in 86, the current collector terminal 86 is mounted on the fuel cell unit 16 shown in FIG. As a result, as shown in FIG. 11, not only the surface where the current collecting terminal 86 and the outer peripheral surface 90b face each other, but also the state where the metal brazing material is arranged on the surface where the current collecting terminal 86 and the end surface 90c face each other. It becomes.

  When brazing processing by heating is performed in this state, as shown in FIG. 12, the paste-like metal brazing material 96a (first brazing material) and the plate-like metal brazing material 96b (second brazing material) are dissolved. And become one. At this time, the paste-like metal brazing material 96a (first brazing material) is dissolved in the plate-like metal brazing material 96b (second brazing material) to become “priming water”, whereby the corner portion of the end face 90c. In 100, the entire state (entire circumference) is maintained, so that “sinking” due to poor wettability between the metal brazing material and the ceramic surface is prevented.

  As a result, as shown in FIG. 12, the paste-like metal brazing material 96a (first brazing material) and the plate-like metal brazing material 96b (second brazing material) are integrally brazed. Processing is complete. Therefore, the occurrence of “sinking” does not occur, the electrical connection between the inner electrode layer 90 and the current collecting terminal 86 is reliably ensured, and the leakage of fuel gas is also reliably prevented.

  The paste-like metal brazing material 96a (first brazing material) shown in the present embodiment has a lot of brazing material particles made of the same material as the plate-like metal brazing material (second brazing material) in the binder. It has been placed. Therefore, when the brazing material is melted in the brazing process, each brazing material exhibits the property of being easily adapted. In other words, the first brazing material and the second brazing material are likely to be united at the time of melting, and the second brazing material exhibits the effect of reliably functioning as priming water.

  In the present embodiment, an example in which a paste-like metal brazing material is employed as the first brazing material and a plate-shaped metal brazing material is employed as the second brazing material has been described. Not limited to. A plate-like metal brazing material may be wound around the side surface of the end portion 90 a of the fuel cell unit 16 to serve as the first brazing material, or conversely, a paste-like metal brazing material is disposed in the current collecting terminal 86. Alternatively, a second brazing material may be used.

1 Solid oxide fuel cell (SOFC)
2 Fuel cell module 4 Auxiliary unit 6 Housing 6a Front surface 6b Rear surface 8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit 18 Combustion chamber 20 Reformer 20a Evaporating section 20b Reforming section 22 Heat exchanger for air 24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit 30 Fuel supply source 32 Shutoff valve 36 Desulfurizer 38 Fuel flow rate adjustment unit 40 Air supply source 42 Solenoid valve 44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit 46 First heater 48 Second heater 50 Hot water production device 52 Control box 54 Inverter 60 Pure water introduction pipe 62 Reformed gas introduction pipe 64 Fuel gas supply pipe 64a Horizontal portion 64b Fuel supply hole 66 Manifold 70 Air collecting chamber 72 Air distribution chamber 74 Air flow channel tube 76 Air introduction tube 78 Exhaust air Exhaust chamber 80 exhaust gas passage 82 exhaust gas discharge pipe 83 ignition device 84 fuel cell 86 current collecting terminal 86a cylindrical portion 86b flat surface 88 fuel gas flow channel 90 inner electrode layer 90a end portion 90b outer peripheral surface 90c end surface 92 outer electrode layer 94 Electrolytic layer 96 Metal brazing material 96a Paste-like metal brazing material (first brazing material)
96b Plate-shaped metal brazing material (second brazing material)
98 Fuel gas flow channel 100 Corner

Claims (3)

A tubular inner electrode layer forming a fuel gas flow path therein;
An outer electrode layer disposed in a tubular shape so as to cover the inner electrode layer;
An electrolytic layer disposed in a tubular shape between the inner electrode layer and the outer electrode layer;
An end portion of the inner electrode layer has a tubular outer peripheral surface exposed to the electrolytic layer and the outer electrode layer, and a tubular fuel cell including the tubular axial end surface ;
Comprising a flow path communicating with said fuel gas flow channel in the center of Utotomoni the end face covering both the outer peripheral surface and the end surface of the inner electrode layer, brazed to the outer peripheral surface of the inner electrode layer In a fuel cell unit comprising a current collecting terminal joined at
The brazing is a brazing material made of a metal material that ensures electrical connection between the inner electrode layer and the current collecting terminal and prevents leakage of fuel gas between the inner electrode layer and the current collecting terminal. The brazing material is disposed in an integrated state from between the current collecting terminal and the outer peripheral surface to between the current collecting terminal and the end surface. Battery cell unit. Characterized in that said brazing material is disposed on the entire circumference of the front Symbol end faces, the fuel cell unit according to claim 1. Fuel cell comprising a fuel cell unit according to claim 1 or 2.

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