JP2009245631A - Fuel cell stack and solid oxide fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack capable of reducing operating temperature without unnecessarily enlarging the fuel cell stack, and to provide a solid oxide fuel cell using the same. <P>SOLUTION: In the fuel cell stack 10 where a power generation cell 16 is sandwiched by a separator 2 forming a fuel gas passage 23 and a separator forming an oxide gas passage 24, a reaction product is generated on the surface of border at a fuel electrode layer side by reacting some of oxide ions with a fuel gas so that the oxide ions ionizing oxygen on an oxide electrode layer are diffused toward a fuel electrode layer side as a solid electrolyte 11, and the electrolyte reproducing oxygen at a fuel electrode layer side and having an electron leakage characteristic is used since some of electrons among the remnant of oxide ions flows backward to the oxide electrode layer in the solid electrolyte. Here, a nickel layer 17 is arranged between the separator and a fuel electrode layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell stack in which a fuel electrode layer is formed on one surface of a plate-shaped solid electrolyte and an oxidant electrode layer is formed on the other surface and sandwiched by separators, and a solid using the same The present invention relates to an oxide fuel cell.

  In recent years, fuel cells that directly convert chemical energy of fuel into electrical energy have attracted attention as high-efficiency and clean power generators. In addition to the polymer electrolyte fuel cells (PEFC) that have been put into practical use, Development of a phosphoric acid fuel cell (PAFC) as the first generation, a molten carbonate fuel cell (MCFC) as the second generation, and a solid oxide fuel cell (SOFC) as the third generation is expected. Among them, the solid oxide fuel cell (SOFC) has a high operating temperature of 600 ° C. to 1000 ° C., can efficiently use exhaust heat, and is suitable for large-scale power generation applications. It can be used in a wide range of fields, from home use and business use to replacement of thermal power plants.

  As this solid oxide fuel cell, for example, as shown in Patent Document 1, an oxidant electrode layer (cathode) is formed on one surface of a flat solid electrolyte layer, and a fuel electrode layer (anode) on the other surface. 2. Description of the Related Art A flat plate type solid oxide fuel cell having a flat plate type fuel cell stack having a sealless structure in which a plurality of power generation cells formed with the above are stacked in the thickness direction via a separator is known. In this flat plate fuel cell stack, a fuel electrode current collector is disposed between the fuel electrode layer and the separator, and an oxidant electrode current collector is disposed between the oxidant electrode layer and the separator. ing.

In this flat solid oxide fuel cell, during power generation, an oxidant gas (oxygen) is supplied to the oxidant electrode layer side as a reaction gas, and a fuel gas (CH ₄ or the like) is supplied to the fuel electrode layer side. The reformed gas (H ₂ , CO _2, etc.) obtained by reforming the city gas containing) by the following reaction in the reformer is supplied. These oxidant electrode layer and fuel electrode layer are both porous layers so that the reaction gas can reach the interface with the solid electrolyte layer.
CH ₄ + 2H ₂ O → 4H ₂ + CO ₂

As a result, oxygen supplied to the oxidant electrode layer side through the pores in the oxidant electrode layer reaches the vicinity of the interface with the solid electrolyte layer in the power generation cell. And is ionized to oxide ions (O ²⁻ ). The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer. The oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the reformed gas at this portion to generate a reaction product gas (H ₂ O, CO _2, etc.), and discharge electrons to the fuel electrode layer. Thereby, electrons generated by the electrode reaction are taken out as an electromotive force at an external load of another route.

By the way, in this solid oxide fuel cell, since the operating temperature is high as described above, members that can be used for fuel cell components such as the fuel cell stack and the reformer are limited to ceramics, for example. There was a problem that.
For this reason, in recent years, a low temperature operation type solid oxide fuel cell has been developed which can lower the operating temperature and can use an inexpensive metal material.

On the other hand, a high temperature of 600 ° C. to 700 ° C. is required to reform the fuel gas by the above reformer.
As a result, when the operating temperature of the solid oxide fuel cell is lowered as described above, the operating temperature of the reformer that operates using the heat generated by the stack also decreases, and the above reforming reaction is not sufficiently performed. The unreformed fuel gas may be supplied to the fuel electrode layer.
For this reason, the solid oxide fuel cell has a problem that the range in which the operating temperature can be lowered is limited by the reforming temperature by the reformer.

In contrast, as shown in Patent Document 2, the present applicants have a plurality of fuel cell stacks in which the power generation cells sandwiched between separators and internal reformers sandwiched between separators are alternately stacked. A flat plate type solid oxide fuel cell is proposed.
According to this fuel cell, the fuel gas can be reformed by the internal reformer in the fuel cell stack having the highest temperature among the component parts, so that the operating temperature of the solid oxide fuel cell can be lowered. it can.

JP 2007-157479 A JP 2007-103343 A

  However, in this solid oxide fuel cell, since the fuel cell stack incorporating the internal reformer becomes larger than necessary, the heat loss accompanying the increase in size increases the use of exhaust heat. There is a drawback that energy efficiency is also reduced.

  Accordingly, an object of the present invention is to propose a fuel cell stack that can reduce the operating temperature without increasing the size of the fuel cell stack more than necessary, and a solid oxide fuel cell using the same.

  The present inventors have found that unreformed fuel gas to which oxygen has been added can be reformed by supplying it to a separator having a nickel plate mounted on the gas outflow surface. Has been completed.

  That is, according to the first aspect of the present invention, there is provided a power generation cell in which a fuel electrode layer is formed on one surface of a plate-like solid electrolyte and an oxidant electrode layer is formed on the other surface. In a fuel cell stack sandwiched between a separator in which a fuel gas passage for supplying gas is formed and a separator in which an oxidant gas passage for supplying an oxygen-containing gas as an oxidant gas is formed in the oxidant electrode layer. As a solid electrolyte, the oxide ions in which the oxygen is ionized in the oxidant electrode layer are diffused toward the fuel electrode layer side, so that one of the oxide ions is formed at the interface on the fuel electrode layer side. As a result of the reaction of the part with the fuel gas, a reaction product is generated, and electrons flow back from the remainder of the oxide ions in the solid electrolyte toward the oxidant electrode layer. Element has an electrolyte having electron leakage characteristics being regenerated used 燃極 layer side, and between the separator and the fuel electrode layer, is characterized in that the nickel layer is disposed.

Here, in the present invention, the fuel cell stack means one having a cell unit in which one power generation cell is sandwiched between two separators, and the power generation cell is connected to a fuel gas passage and It is also included to have a plurality of sets of cell units by stacking a plurality of layers through separators in which an oxidant passage is formed.
The nickel layer includes, for example, a nickel plate or a nickel plating layer applied to the surface of the separator on the fuel electrode layer side.

  According to a second aspect of the present invention, in the fuel cell stack according to the first aspect, a plurality of the power generation cells are stacked in a plate thickness direction via a separator in which the fuel gas passage and the oxidant gas passage are formed. In addition, a fuel electrode current collector is disposed between each separator and each fuel electrode layer, and the fuel electrode current collector is made of nickel foam.

  According to a third aspect of the present invention, there is provided a power generation cell in which a fuel electrode layer is formed on one surface of a plate-shaped solid electrolyte and an oxidant electrode layer is formed on the other surface, and fuel gas is supplied to the fuel electrode layer. A plurality of fuel cell stacks stacked in the plate thickness direction through separators each having a fuel gas passage to be supplied and an oxidant gas passage for supplying an oxidant gas to the oxidant electrode layer; An oxidant gas supply line for supplying the oxidant gas is connected to the oxidant gas passage, a fuel gas supply line for supplying the fuel gas is connected to the fuel gas passage, and the fuel gas supply line is connected to the fuel gas supply line. In a solid oxide fuel cell in which a reformer for reforming a fuel gas is interposed, a nickel layer is disposed between the separator and the fuel electrode layer, and the fuel gas supply line includes: In the downstream side of the Kiaratame reformer is characterized in that oxygen supply pipe adding an oxygen-containing gas into the fuel gas is connected.

  According to the fuel cell stack according to claim 1 and the solid oxide fuel cell according to claim 3, since the electrolyte having electron leakage characteristics is used as the solid electrolyte, the interface on the fuel electrode layer side of the solid electrolyte In addition, oxygen is present together with reaction products such as water vapor. For this reason, when supplying the fuel gas from the separator toward the fuel electrode layer, the fuel gas flows along the surface of the nickel layer and causes an oxidation reaction, which is an exothermic reaction, by oxygen present in the fuel electrode layer. It provides the heat and high temperature field required for steam reforming.

Thus, since the interface on the fuel electrode layer side of this solid electrolyte is also rich in water vapor, the following reforming reaction proceeds further and a large amount of hydrogen can be generated.
CH ₄ + 2H ₂ O → 4H ₂ + CO ₂
Therefore, the fuel gas can be reformed in the fuel cell stack that is the highest temperature among the components of the fuel cell, and is not limited by the reforming temperature of the reformer installed outside the fuel cell stack. Highly efficient power generation is possible, and at the same time, the operating temperature of the fuel cell can be lowered. In addition, since the fuel cell stack is enlarged only for the nickel layer disposed between the fuel electrode layer and the separator, the energy efficiency of the entire fuel cell using exhaust heat is reduced due to the enlargement more than necessary. Can be blocked.

  In particular, according to the invention described in claim 2, by disposing the anode current collector made of foamed nickel between the separator and the anode layer, the reforming reaction is performed by the anode current collector. Since oxygen and water vapor existing at the interface on the fuel electrode layer side of the solid electrolyte diffuse from the foamed nickel to the surface of the nickel layer, the nickel layer surface and fuel electrode under the presence of oxygen and water vapor-rich conditions The reforming reaction involving the oxidation reaction can be efficiently performed in the current collector.

  In addition, according to the invention described in claim 3, the fuel gas is reformed by the reformer and supplied to the fuel gas passage of the separator together with the oxygen-containing gas added by the oxygen supply pipe. Therefore, even when unreformed fuel gas is supplied to the fuel gas passage, the fuel gas is added with oxygen-containing gas. By being supplied into the fuel cell stack, a reforming reaction accompanied by an oxidation reaction is caused on the surface of the nickel layer or the like, and a reformed gas containing more hydrogen can be sent to the fuel electrode layer side of the solid electrolyte. . For this reason, the possibility that the unreformed fuel gas is supplied to the fuel electrode layer as it is is greatly reduced, and the energy loss of the entire fuel cell due to the release of the unreformed gas from the outside of the fuel electrode layer is significantly reduced. Can be reduced.

  Hereinafter, embodiments of a flat plate type solid oxide fuel cell according to the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the fuel cell according to this embodiment has a fuel electrode layer 12 formed on one surface of the solid electrolyte 11 and an oxidant electrode layer 13 formed on the other surface. A fuel cell stack 10 having a substantially rectangular columnar shape in appearance is formed by stacking a plurality of power generation cells 16 in the plate thickness direction with a rectangular plate-like separator 2 interposed therebetween.

  Further, in the fuel cell stack 10, a circular plate-shaped fuel electrode current collector 14 is disposed between the fuel electrode layer 12 of the power generation cell 16 and the separator 2, and the fuel electrode current collector 14 and the separator 2 are arranged. A nickel plate 17 is disposed between the two. In the fuel cell stack 10, a circular plate-shaped oxidant electrode current collector 15 is disposed between the oxidant electrode layer 13 and the separator 2.

As the solid electrolyte 11, a circular flat plate-like ceria-based, bismuth-based, or lanthanum gallate-based ceramic plate having electron leakage characteristics is used.
Specifically, as a ceria-based ceramic plate having electron leakage characteristics, ceria (CeO ₂ ) doped with a small amount of Y ₂ O ₃ , Gd ₂ O ₃ , Sm ₂ O _3, etc. is used. Samarium doped ceria (SDC) doped with Sm ₂ O ₃ is used. As the bismuth ceramic plate, bismuth oxide (Bi ₂ O ₃ ) and yttria (Y ₂ O ₃ ) are used.
Further, as the solid electrolyte 11, _{preferably, La 1-x Sr x Ga} 1-yz Mg y Co z O 3 is lanthanum gallate-based ceramic plate (X = 0.05~0.3, Y = 0~0 . 29, Z = 0.01 to 0.3, Y + Z = 0.025 to 0.3 (hereinafter abbreviated as LSGMC)).

The fuel electrode layer 12 is formed of a metal such as Ni or a cermet such as Ni—YSZ, Ni—SDC, or Ni—GDC, and the oxidant electrode layer 13 is formed of LaMnO ₃ , LaCoO _3, SrCoO _3, or the like. Yes. The fuel electrode current collector 14 is formed in a circular flat plate shape with a sponge-like porous sintered nickel plate (foamed nickel), and the oxidant electrode current collector 15 is a sponge-like porous sintered metal such as Ag. The plate is formed into a circular flat plate shape.

  Further, the nickel plate 17 is formed in a circular flat plate shape having the same diameter as the fuel electrode current collector 14, and an opening 17a corresponding to a discharge port 2x described later is formed at the center thereof.

  The separator 2 is made of a substantially rectangular stainless steel plate having a thickness of several millimeters, and the separator body at the center where the power generation cell 16, the current collectors 14 and 15, and the nickel plate 17 are stacked. 20 and a pair of separator arms 21 and 22 that extend in the surface direction from the separator body 20 and support opposing edges of the separator body 20 at two locations.

  The separator body 20 has a function of electrically connecting the power generation cells 16 via the current collectors 14 and 15 and supplying a reaction gas to the power generation cells 16. Is introduced from the edge of the separator 2 and ejected from the discharge port 2x at the center of the surface of the separator 2 facing the anode current collector 14, and the oxidant gas is introduced from the edge of the separator 2. And an oxidant gas passage 24 ejected from the discharge port 2y at the center of the surface of the separator 2 facing the oxidant electrode current collector 15.

Each separator arm 21, 22 has a structure that is flexible in the laminating direction as an elongated strip extending at the opposite corner with a slight gap along the outer periphery of the separator body 20. In addition, a pair of gas holes 28x and 28y penetrating in the thickness direction are provided in the end portions 26 and 27 of the separator arms 21 and 22, respectively.
One gas hole 28x communicates with the fuel gas passage 23 of the separator 2, and the other gas hole 28y communicates with the oxidant gas passage 24 of the separator 2. The gas passages 23x, 24y are connected to the gas passages 28x, 28y, respectively. The fuel gas and the oxidant gas are supplied to the surfaces of the electrodes 12 and 13 of the power generation cells 16 through the through holes.

  In addition, the power generation cell 16 and the current collectors 14 and 15 are interposed between the main bodies 20 of the separators 2, and insulating manifold rings 29x and 29y are interposed between the gas holes 28x and 28y of the separators 2, respectively. Thus, a fuel cell stack 10 having a substantially rectangular columnar shape in appearance is formed, which has a fuel gas manifold formed by the gas holes 28x and the manifold ring 29x and an air manifold formed by the gas holes 28y and the manifold ring 29y.

  As shown in FIG. 3, flanges 3 that are larger than the separator 2 are provided at the upper and lower portions of the fuel cell stack 10, and two portions corresponding to the manifolds of these flanges 3 are respectively 2 Bolts 31 are inserted one by one, and nuts 32 are screwed to both ends thereof. The flange 3 and the bolt 31 in which nuts 32 are screwed to both ends secure the gas sealing performance of the manifold having the manifold rings 29x and 29y interposed therebetween.

  The upper flange 3 is provided with a hole 30 larger than the outer diameter of the power generation cell 16 at the center. The hole 30 is substantially the same as the power generation cell 16 placed on the uppermost separator 2. A weight 39 having the same size is arranged. The weight 39 ensures mutual adhesion between the power generation cell 16, the nickel plate 17, and the separator 2 sandwiched between the current collectors 14 and 15.

  The fuel cell stack 10 configured as described above is placed on the pedestal 51 in the central portion of the inner can 5 having a rectangular cylindrical body including four side plates, a top plate, and a bottom plate. A large number of rows are arranged side by side in a plurality of rows in the vertical and horizontal directions (2 rows in this embodiment) and a plurality of columns (2 rows in this embodiment), and a plurality of rows are arranged in the vertical height direction (4 in this embodiment). Has been placed. Thereby, in the internal can body 5, fuel cell stack groups 1 a to 1 d constituted by a plurality of fuel cell stacks 10 arranged in the vertical height direction are disposed, while the internal can body 5 The outer periphery is covered with a heat insulating material 50.

  Each fuel cell stack 10 adopts a sealless structure in which a reaction gas generated by a reaction between an oxidant gas and a reformed gas or an unreacted gas is released to the outside as it is started. Further, the temperature required for power generation can be maintained in the inner can body 5 by the fuel heat of the unreacted gas.

Furthermore, the fuel cell according to the present embodiment includes a fuel gas supply line 6 that supplies reformed gas to the fuel electrode layer 12 of the flat plate fuel cell stack 10 through the fuel gas manifold and the fuel gas passage 23, and an oxidant. An oxidant gas supply line 7 for supplying an oxidant gas to the polar layer 13 through an oxidant gas manifold and an oxidant gas passage 24 is provided.
The oxidant gas supply line 7 includes air heat exchangers 72a or 72b each formed of a rectangular parallelepiped casing disposed along the side surfaces of the fuel cell stack groups 1b and 1c or 1d and 1a, and downstream sides of the air heat exchangers 72a or 72b. The air buffer tank 73a or 73b provided in the fuel cell stack 10, the oxidant gas manifold of each fuel cell stack 10, and the pipes 74a and 74b for connecting them and the pipes connected to the introduction side of the air heat exchangers 72a and 72b (illustrated) And an oxidant gas passage 24.

On the other hand, the fuel gas supply line 6 is provided with a branch pipe 60 having an inlet for introducing fuel gas at one end and branching into two at the other end. The branch pipe 60 is connected to a water vapor supply line having a water vapor generator (not shown) on the other end side branched into two. Further, the branch pipe 60 is connected to the fuel heat exchangers 61a and 61b at the other end on the downstream side of the connecting portion.
Each of the fuel heat exchangers 61a and 61b is formed of a rectangular parallelepiped casing disposed along the side surface of each of the fuel cell stack groups 1a and 1b or 1c and 1d, and the discharge side is reformed via the introduction pipe 62, respectively. Connected to the device 63.

  The reformer 63 includes a cruciform cross-sectional casing disposed between opposing side surfaces of the fuel cell stack groups 1a to 1d, and includes a wing portion 63a positioned between the fuel cell stack groups 1a and 1b, and a stack group. It has 63b located between 1b and 1c, the wing | blade part 63c located between the stack groups 1c and 1d, and the wing | blade part 63d located between the stack groups 1d and 1a. Each of the wing parts 63a to 63d has a height extending from between the uppermost fuel cell stacks 10 to between the lowermost fuel cell stacks 10, and each of the wing parts 63a to 63d. Each of them contains a reforming catalyst.

The reformer 63 has an introduction pipe 62 connected to the upper parts of the blade parts 63a and 63c, and a discharge pipe 64 connected to the lower parts of the blade parts 63b and 63d, respectively. The other end of 64 is connected to fuel buffer tanks 65a and 65b, respectively.
The fuel buffer tanks 65a and 65b are connected to the fuel gas manifolds of the fuel cell stacks 10 through pipes 66a and 66b, respectively.

  Accordingly, the fuel gas supply line 6 includes the branch pipe 60, the fuel heat exchangers 61a and 61b, the introduction pipe 62, the reformer 63, the discharge pipe 64, the fuel buffer tanks 65a and 65b, the fuel gas manifold and the pipes 66a and 66b. And the fuel gas passage 23.

  Further, oxygen supply pipes (not shown) for supplying an oxygen-containing gas are connected to the fuel buffer tanks 65a and 65b, respectively, so that the fuel cell can supply the oxygen-containing gas supplied to the fuel gas manifold. Is supplied to the fuel electrode layer 12 of the power generation cell 16 of each stack 10, and the oxidant gas supplied to the air manifold is supplied to the oxidant electrode layer 13 of the power generation cell 16 of each stack 10. It has become.

  The fuel heat exchangers 61a and 61b, the reformer 63, the fuel buffer tanks 65a and 65b, the steam generator, the air heat exchanger 72, and the air buffer tanks 73a and 73b described above are all in the inner can body 5. Or it is arrange | positioned in the vicinity and it heats by the infrared rays burner 55 which operate | moves at the time of starting installed in each side plate of the internal can body 5, the above-mentioned temperature rise in the internal can body 5, etc.

Next, the operation of the flat plate type fuel cell will be described.
First, the infrared burner 55 is activated, and city gas as fuel gas is supplied to the fuel gas supply line 6 through the branch pipe 60 and air as oxidant gas is supplied to the oxidant gas supply line 7.

  Then, the air supplied to the oxidant supply line 7 is heated in the air heat exchangers 72a and 72b, and then supplied to the air buffer tanks 73a and 73b. Then, the air is supplied to the oxidant supply line 7 via the pipes 74a and 74b. The gas is supplied to the oxidant gas passage 24 of each separator 2 through the oxidant gas manifold of the fuel cell stack 10.

When the air supplied to the oxidant gas passage 24 is supplied from the oxidant electrode current collector 15 of the power generation cell 16 to the oxidant electrode layer 13 through the discharge port 2y, oxygen receives electrons in the air electrode layer 13. As a result, it is moved to the solid electrolyte layer 11 while being ionized to oxide ions (O ²⁻ ). The oxide ions diffuse toward the fuel electrode layer 12 in the solid electrolyte layer 11. Then, at the interface of the solid electrolyte 11 on the fuel electrode layer 12 side, some of the oxide ions react with the following reformed gas to release reaction products such as water vapor to the outside, and the rest of the oxide ions As a result, some electrons flow backward toward the oxidant electrode layer 13 of the solid electrolyte 11 so that oxygen is regenerated on the fuel electrode layer 12 side.

On the other hand, the city gas supplied to the fuel gas supply line 6 is heated in the fuel heat exchangers 61a and 61b together with the steam supplied from the steam supply line, and then supplied from the introduction pipe 62 to the reformer 63. Then, the fuel cell stack groups 1a to 1d are reformed into hydrogen-rich reformed gas by contacting with the reforming catalyst while being efficiently heated by the heat radiation from each stack 10.
The reformed gas is supplied to the fuel buffer tanks 65a and 65b through the discharge pipe 64, and air is added from the oxygen supply pipe in the fuel buffer tanks 65a and 65b, and then the pipe 66a, 66b and the fuel gas manifold 23 of each fuel cell stack 10 are supplied to the fuel gas passage 23 of each separator 2.

  The reformed gas supplied to the fuel gas passage 23 flows along the surface of the nickel plate 17 when supplied from the discharge port 2x toward the fuel electrode layer 12 through the opening 17a of the nickel plate 17, It moves to the fuel electrode layer 12 through the fuel electrode current collector 14. At this time, when unreformed fuel gas is present together with the reformed gas, the fuel gas is absorbed on the surface of the nickel plate 17 where oxygen or water vapor diffused from the interface on the fuel electrode layer 12 side of the solid electrolyte 11 exists. In the fuel electrode current collector 14, a reforming reaction accompanied by an oxidation reaction is caused and supplied to the fuel electrode layer 12. Therefore, as described above, it reacts with the oxide ions present at the interface of the solid electrolyte 11 on the fuel electrode layer 12 side to release reaction products such as water vapor to the outside and discharges electrons to the fuel electrode layer 12. . The emitted electrons are taken out as an electromotive force.

  According to the flat plate type solid oxide fuel cell of this embodiment, LSGMC having electron leakage characteristics is used as the solid electrolyte 11, so that a reaction product such as water vapor is present at the interface of the solid electrolyte 11 on the fuel electrode layer 12 side. Along with oxygen. Further, during power generation, a small amount of air is added from the oxygen supply pipe when the reformed gas obtained by reforming the fuel gas by the reformer 63 is supplied to the fuel gas passage 23 through the fuel gas supply line 6.

  At this time, the amount of air supplied from this oxygen supply pipe is such that when the city gas mainly composed of methane gas is supplied as fuel gas to the fuel gas supply line 6, the amount of oxygen contained in the air is 1 of methane gas. It is prepared to have a mole number of / 10 to 4/10. This is because if the ratio is less than 1/10, the above reforming reaction is not sufficiently performed on the surface of the nickel plate 17 or the like, and if it exceeds 4/10, combustion occurs in the fuel cell stack 10 in a high temperature atmosphere. This is because the amount of power generated by the electrode reaction decreases.

  Therefore, even when a partially unreformed fuel gas is supplied to the fuel gas passage 23 together with the reformed gas, the fuel gas is directed together with the reformed gas from the discharge port 2x toward the fuel electrode layer 12 through the opening 17a. When supplied, it flows along the surface of the nickel plate 17 and then moves to the anode layer 12 through the anode current collector 14. At this time, the fuel gas causes a reforming reaction accompanied by an oxidation reaction on the surface of the nickel plate 17 where the oxygen or water vapor diffused from the fuel electrode layer 12 side of the solid electrolyte 11 exists or in the fuel electrode current collector 14. Thus, a reformed gas containing a large amount of hydrogen is generated. For this reason, even when unreformed fuel gas is supplied to the fuel gas passage 23, it is supplied to the interface on the solid electrolyte 11 side of the fuel electrode layer 12 as reformed gas.

  Therefore, the possibility that unreformed fuel gas is directly supplied to the fuel electrode layer 12 is significantly reduced, and energy loss caused by discharging the unreformed gas as it is from the outside of the fuel electrode layer 12 is significantly reduced. Can do. In addition, the fuel gas can be reformed by the reformer 63 that is efficiently heated by the heat radiation from each fuel cell stack 10, and the reforming reaction is performed in the highest temperature fuel cell stack 10. Therefore, the operating temperature of the fuel cell can be reduced to the maximum. In addition, since the fuel cell stack 10 can obtain the above-described reforming function by arranging the same number of nickel plates 17 as the power generation cells 16, a flat plate that uses exhaust heat without increasing the size more than necessary. The decrease in energy efficiency in the solid oxide fuel cell of the type can also be prevented.

The present invention is not limited to the above-described embodiment. For example, instead of the nickel plate 17, the surface of the separator 2 on the fuel electrode current collector 14 side may be subjected to nickel plating. It is not necessary to have both the oxygen supply pipe for supplying the oxygen-containing gas to the fuel buffer tanks 65a and 65b and the solid electrolyte 11 having the electron leakage characteristic for regenerating oxygen on the fuel electrode layer side, at least one of them. As long as it has.
Further, the present invention is not limited to a flat plate type solid oxide fuel cell having a plurality of flat plate type fuel cell stacks 10, and may be a solid oxide fuel cell other than this flat plate type.

It is a perspective view for demonstrating the structure of the fuel cell stack 10 which concerns on this invention. 2 is a cross-sectional view for explaining a reaction in the fuel cell stack 10. FIG. FIG. 2 is a configuration diagram of the fuel cell stack 10, wherein (a) is a plan view and (b) is a side view. 1 is a cross-sectional view of a flat plate type solid oxide fuel cell according to the present invention. It is a longitudinal cross-sectional view of the solid oxide fuel cell.

Explanation of symbols

2 Separator 2x Fuel gas discharge port 2y Oxidant gas discharge port 6 Fuel gas supply line 7 Oxidant gas supply line 10 Fuel cell stack 11 Solid electrolyte 12 Fuel electrode layer 13 Oxidant electrode layer 14 Fuel electrode current collector 15 Oxidation Current collector 16 Power generation cell 17 Nickel plate 17a Opening 23 Fuel gas passage 24 Oxidant gas passage 63 Reformer

Claims (3)

A power generation cell in which a fuel electrode layer is formed on one surface of a plate-shaped solid electrolyte and an oxidant electrode layer is formed on the other surface is formed with a fuel gas passage for supplying fuel gas to the fuel electrode layer In a fuel cell stack sandwiched between a separator and a separator formed with an oxidant gas passage for supplying an oxygen-containing gas as an oxidant gas to the oxidant electrode layer,
As the solid electrolyte, the oxide ions in which the oxygen is ionized in the oxidant electrode layer are diffused toward the fuel electrode layer side, so that the oxide ions are formed at the interface on the fuel electrode layer side. A reaction product is generated by a part of the reaction with the fuel gas, and a part of the electrons from the remainder of the oxide ions flows back through the solid electrolyte toward the oxidant electrode layer, thereby generating oxygen. A fuel cell stack, wherein an electrolyte having electron leakage characteristics regenerated on the fuel electrode layer side is used, and a nickel layer is disposed between the separator and the fuel electrode layer . A plurality of the power generation cells are stacked in the plate thickness direction via a separator in which the fuel gas passage and the oxidant gas passage are formed, and a fuel electrode current collector is disposed between the fuel electrode layer and the nickel layer. The fuel cell stack according to claim 1, wherein the fuel electrode current collector is made of nickel foam. A power generation cell having a fuel electrode layer formed on one surface of a plate-like solid electrolyte and an oxidant electrode layer formed on the other surface, a fuel gas passage for supplying fuel gas to the fuel electrode layer, and the oxidant A plurality of fuel cell stacks stacked in the thickness direction through separators each formed with an oxidant gas passage for supplying an oxidant gas to the polar layer, and the oxidant gas in the oxidant gas passage of the separator; A reformer for connecting a fuel gas supply line for supplying the fuel gas to the fuel gas passage, and for reforming the fuel gas to the fuel gas supply line In a solid oxide fuel cell in which
A nickel layer is disposed between the separator and the fuel electrode layer, and an oxygen supply pipe for adding an oxygen-containing gas to the fuel gas is connected to the fuel gas supply line on the downstream side of the reformer. A solid oxide fuel cell.

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