JP2006277969A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the covering of a fuel electrode caused by carbon deposition or drop in activity in a solid oxide fuel cell for generating electric power by reforming mixed gas containing organic material fuel and water vapor. <P>SOLUTION: The solid oxide fuel cell generates electric power by reforming mixed gas E containing hydrocarbon fuel and water vapor. The cell is equipped with a power generation element 2 comprising a fuel electrode 5, an air electrode 4, and a solid electrolyte membrane 3, and a porous partition 10 forming reformed gas by reforming the mixed gas E. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell (SOFC) cell.

  Solid oxide fuel cells are roughly classified into so-called flat plate types and cylindrical types. In a flat type solid oxide fuel cell, a stack for power generation is configured by alternately stacking so-called separators and power generation layers. That is, a fuel electrode and an air electrode are respectively formed on a solid electrolyte membrane to produce a power generation layer, and an interconnector is prepared, and ceramic powder and an organic binder are contained between the power generation layer and the interconnector. The power generation layer and the interconnector are joined by sandwiching the thin film and heat-treating the thin film.

A so-called internal reforming type is known as a solid oxide fuel cell (Patent Document 1). In the internal reforming SOFC, a mixed gas of hydrocarbon fuel and water vapor flows in the vicinity of the fuel electrode, and reformed in situ by the catalyst used in the fuel electrode to generate hydrogen and carbon monoxide (CO). Let That is, when Ni-YSZ is used as the constituent material of the fuel electrode, hydrocarbons (for example, methane) in the fuel gas are steam reformed by the catalytic action of Ni to become hydrogen and CO, contributing to the electrochemical reaction. Electricity is generated by supplying this hydrogen to the fuel electrode side of a cell provided with electrodes on both sides of the solid electrolyte membrane. If such a cell is used, it is not necessary to provide a reformer outside the cell, so that the entire power generation apparatus can be remarkably simplified.
"Solid Oxide Fuel Cell and Global Environment" Hiroaki Tagawa, Agne Jofusha (1998) p65

However, when the amount of water vapor in the mixed gas is insufficient, carbon is easily deposited. When carbon is deposited, the active part contributing to the electrode reaction in the fuel electrode is covered and the electrochemical reaction is inhibited. Further, nickel carbide (Ni ₃ C) may be generated by the reaction between nickel and carbon. As a result, the activity as the electrode material disappears, and the Ni portion undergoes volume expansion due to the formation of nickel carbide, which may cause a large strain inside the anode.

  SUMMARY OF THE INVENTION An object of the present invention is to prevent a fuel electrode from being covered or reduced in activity due to carbon deposition in a solid oxide fuel cell for reforming a mixed gas containing organic fuel and water vapor to generate electric power. It is.

  The present invention relates to a solid oxide fuel cell for reforming a mixed gas containing an organic fuel and water vapor to generate electric power, and includes a fuel electrode, an air electrode, and a solid electrolyte membrane, and a power generating element, A porous partition wall having a function of generating a reformed gas by reforming the mixed gas is provided.

  According to the present invention, a mixed gas containing an organic fuel and water vapor is permeated through a porous partition wall, and a reforming reaction is caused. The reformed gas obtained after the reforming reaction is supplied to the vicinity of the fuel electrode to generate power. Therefore, the reforming reaction can sufficiently proceed in the porous partition wall, and thereby hydrogen can be efficiently generated without the necessity of excessively supplying water vapor. Further, when carbon deposition occurs, the porous partition functions as a filter for carbon, so that it is possible to prevent carbon from coming into direct contact with the fuel electrode of the power generation element. A decrease in catalyst activity can be prevented, and deterioration of the fuel electrode over time can be suppressed.

  In a preferred embodiment, a mixed gas chamber for supplying a mixed gas is formed, and a reformed gas chamber for flowing the reformed gas is formed between the fuel electrode and the porous partition wall. By clearly separating the mixed gas chamber and the reformed gas chamber in this way, contact of the mixed gas with the fuel electrode can be prevented, and the reformed gas can be leaked relatively uniformly from the entire porous partition wall. Since it can be supplied to the fuel electrode, the power generation efficiency is further improved.

  In a preferred embodiment, the outlet side of the mixed gas chamber is closed. As a result, pressure is applied to the mixed gas supplied into the mixed gas chamber, and the permeation and reforming of the porous partition walls of the mixed gas are promoted.

  In a preferred embodiment, the inlet side of the reformed gas chamber is closed. As a result, the reformed gas once reformed can be prevented from being discharged again from the inlet side. The outlet side of the reformed gas chamber is not blocked because the exhaust gas after the electrochemical reaction is discharged.

  In a preferred embodiment, the fuel electrode and the porous partition wall are integrated to form a support base for the power generation element. If the fuel electrode and the porous partition are separate, a holding mechanism for both is required, and the configuration of the apparatus becomes complicated. However, according to the present embodiment, the fuel electrode and the porous partition wall can be integrally formed of the same material, so that the cell structure is simplified.

  In a preferred embodiment, a plurality of mixed gas chambers are provided in the support substrate. In a preferred embodiment, a plurality of reformed gas chambers are provided in the support base. In a particularly preferred embodiment, the support substrate is a honeycomb substrate.

Hereinafter, the present invention will be described in more detail with reference to the drawings as appropriate.
FIG. 1 is a cross-sectional view schematically showing a conventional internal reforming SOFC. The power generating element 2 includes a solid electrolyte membrane 3, an air electrode 4, and a fuel electrode 5. By providing the interconnector 1 on the upper side and the lower side of the power generation element 2, the oxidizing gas chamber 6 and the fuel gas chamber 7 are formed. The oxidizing gas flows into the oxidizing gas chamber 6 as shown by the arrow C and is discharged. The fuel gas chamber 7 also serves as a reforming chamber. That is, when a mixed gas containing a hydrocarbon raw material and water vapor is supplied into the fuel gas chamber 7 as shown by an arrow A, the mixed gas comes into contact with the fuel electrode in the fuel gas chamber 7 and is reformed by, for example, nickel catalytic action. To produce hydrogen and carbon monoxide. Hydrogen and carbon monoxide that did not contribute to the electrochemical reaction flow as shown by arrow B and are discharged from the cell.

With such a structure, when the amount of water vapor in the mixed gas is insufficient, carbon is deposited on the fuel electrode. When carbon is deposited, the active part contributing to the electrode reaction in the fuel electrode is covered and the electrochemical reaction is inhibited. In addition, nickel carbide (Ni ₃ C) may be generated by the reaction between nickel and carbon.

  2A is a cross-sectional view schematically showing a cell 20A according to one embodiment of the present invention, and FIG. 2B is a perspective view of the cell 20A in FIG. 2A.

  The power generating element 2 includes a solid electrolyte membrane 3, an air electrode 4, and a fuel electrode 5. The oxidizing gas chamber 6 is formed by providing the interconnector 1 on the upper side in the drawing of the power generation element 2. The oxidizing gas flows into the oxidizing gas chamber 6 as shown by the arrow C and is discharged. In the drawing of the power generation element 2, a porous partition wall 10 is installed on the lower side, and an interconnector 1 is installed on the lower side of the porous partition wall 10. A reformed gas chamber 8 is formed between the power generation element 2 and the porous partition wall 10, and a mixed gas chamber 9 is formed between the porous partition wall 10 and the interconnector 1.

  A mixed gas containing at least an organic fuel and water vapor is supplied into the mixed gas chamber 9 as indicated by an arrow E. This mixed gas flows in the mixed gas chamber 9 and permeates the porous partition wall 10 as indicated by an arrow D. The mixed gas is reformed while being in contact with the porous partition wall 10 and passing through the porous partition wall 10, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. Then, an electrochemical reaction occurs in the power generation element 2.

  More specifically, the mixed gas E before reforming contains fuel and water vapor, but the reforming reaction proceeds while coming into contact with the porous partition wall 10, and most of them generate hydrogen and carbon monoxide. However, some remain unreacted. Also, sometimes unnecessary carbon is deposited. These generated gas and unreacted gas pass through the porous partition wall 10. During this time, as the unreacted gas enters and passes through the fine porous structure, it comes into contact with a material with high specific surface area that has catalytic ability, and the reforming reaction proceeds sufficiently to generate hydrogen and carbon monoxide. Generate. In addition, unnecessary carbon deposits are aggregates larger than the pore size of the porous wall, so that they are scraped off on the porous surface and do not pass through the reformed gas chamber 8. Accordingly, the carbon that causes deterioration of the fuel electrode of the cell does not reach the fuel electrode, and can prevent deterioration of the cell performance.

In the present invention, the shape and forming method of the reformed gas chamber and the mixed gas chamber are not particularly limited. For example, as shown in FIG. 2, the reformed gas chamber 8 is formed in the gap between the power generation element 2 and the porous partition wall 10, and the mixed gas chamber 9 is formed in the gap between the porous partition wall 10 and the interconnector 1. Can be formed. Alternatively, a groove can be formed on the surface side of the fuel electrode 5, and this groove can be used as a reformed gas chamber. Or a groove | channel can be formed in the electric power generation element side surface of the porous partition 10, and this groove | channel can be used as a reformed gas chamber. Further, a groove can be formed on the surface of the porous partition wall 10 on the interconnector 1 side, and this groove can be used as a mixed gas chamber. Or a groove | channel can be formed in the surface of the interconnector 1, and this groove | channel can be made into a mixed gas chamber.
The porosity of the porous partition wall is preferably 30 to 70% from the viewpoint of air permeability, and the average pore diameter is preferably 5 to 100 μm from the viewpoint of the trapping performance of precipitated carbon.

  When such a groove is formed in an air electrode, a porous partition wall, or an interconnector, the groove can be provided by grinding. In the case of ceramics, a groove is previously formed in the molded body at the time of forming the molded body. You can also keep it.

As described above, the mixed gas chamber is opened on the inlet side for gas supply, and the reformed gas chamber is opened on the outlet side for exhaust. The mixed gas chamber and the reformed gas chamber communicate with each other through a porous partition wall. Portions other than the porous wall communicating with these openings are kept airtight so that gas does not leak. As a method for holding the porous partition wall tightly in the container partition wall, there is a method in which ceramic bond or the like is applied and hardened as a sealant. Alternatively, there is a method in which an airtight plate is bonded to a porous partition wall.

  In a preferred embodiment, the porous partition wall is made conductive, and the porous partition wall is installed between the interconnector and the cell. The generated electricity passes through the porous partition from the fuel electrode of the cell and is collected from the interconnector. Similarly to the production of the cell and the porous wall, this interconnector can also be used by stacking those produced separately. Further, the interconnector, the porous partition wall, and the power generation element may be joined with a conductive joining material or the like. Furthermore, as an integrated structure, the interconnector and the porous partition can be integrally molded and fired. Alternatively, the fuel electrode, the porous partition wall, and the interconnector can be integrally molded and fired.

  In the cell 20 </ b> B of FIG. 3, the power generating element 2 includes a solid electrolyte membrane 3, an air electrode 4, and a fuel electrode 5. In the drawing of the power generation element 2, an interconnector 1A is installed on the upper side, and a plurality of elongated grooves 11A are formed in the interconnector 1A. By installing the interconnector 1 </ b> A on the power generation element 2, each groove 11 </ b> A functions as the oxidizing gas chamber 6.

  A porous partition wall 10A is installed below the power generation element 2, and an interconnector 1B is installed below the porous partition wall 10A. A plurality of grooves 10 a are formed in the porous partition wall 10 A, and each groove 10 a functions as the reformed gas chamber 8. A plurality of grooves 11B are formed in the interconnector 1B, and each groove 11B functions as the mixed gas chamber 9.

  A mixed gas containing at least an organic fuel and water vapor is supplied into the mixed gas chamber 9 as indicated by an arrow E. This mixed gas flows through each mixed gas chamber 9 and permeates through the porous partition wall 10A. The mixed gas is reformed while being in contact with the porous partition wall 10A and permeating through the porous partition wall 10A, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 2. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by arrow B.

  In the cell 20C of FIG. 4, the power generating element 2A is composed of the solid electrolyte membrane 3, the air electrode 4, and the fuel electrode 5A. The porous partition 10 is installed under the power generation element 2A, the interconnector 21 is installed under the porous partition 10, and the power generation element 2A is installed under the interconnector 21. Thus, in this example, the power generating element 2A, the porous partition wall 10, and the interconnector 21 are laminated in this order.

  In this example, the porous partition wall 10 has a flat plate shape. A plurality of rows of grooves 5 a are formed in the fuel electrode 5 A in parallel with each other, and each groove 5 a functions as the reformed gas chamber 8. A plurality of rows of grooves 21a and 21b are formed on both surfaces of the interconnector 21, respectively. The groove 21 a on the porous partition wall 10 side functions as the mixed gas chamber 9. Further, the groove 21 b on the power generation element 2 </ b> A side of the interconnector 21 functions as the oxidizing gas chamber 6.

  A mixed gas containing at least organic fuel and water vapor is supplied into each mixed gas chamber 9 as shown by an arrow E. This mixed gas flows through each mixed gas chamber 9 and permeates through the porous partition walls 10. The mixed gas is reformed while being in contact with the porous partition wall 10 and passing through the porous partition wall 10, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 2. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by arrow B.

  In the cell 20D of FIG. 5, the power generating element 2 has a flat plate shape. A flat porous partition wall 10 is installed under the power generation element 2, and an interconnector 1 </ b> B is installed under the porous partition wall 10. A gap between the power generation element 2 and the porous partition wall 10 functions as the reformed gas chamber 8. A plurality of rows of grooves 11 are formed in the interconnector 1 </ b> B in parallel, and each groove 11 functions as a mixed gas chamber 9.

  A mixed gas containing at least organic fuel and water vapor is supplied into each mixed gas chamber 9 as shown by an arrow E. This mixed gas flows through each mixed gas chamber 9 and permeates through the porous partition wall 10 as indicated by an arrow D. The mixed gas is reformed while being in contact with the porous partition wall 10 and passing through the porous partition wall 10, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 2. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by arrow B.

  In the cell 20E of FIGS. 6 and 7, the fuel electrode and the interconnector are integrally formed, and an integral support base 15 is formed. 6A is a front view of the cell 20E viewed from the inlet side of the mixed gas, FIG. 6B is a side view of the cell, and FIG. 6C is the outlet side of the reformed gas chamber. It is the front view seen from. FIG. 7 is a perspective view of the cell.

  In this example, for example, one reformed gas chamber 8 and one mixed gas chamber 9 are formed in the support base 15. The support base 15 includes a fuel electrode 15a constituting the power generation element 16, a support portion 15d thereof, a porous partition wall 15b, and a support portion 15c of the porous partition wall 15b. The fuel electrode 15a and the support portions 15d and 15c are continuous and form an elongated cylindrical base. The reformed gas chamber 8 and the mixed gas chamber 9 are separated from each other by providing a porous partition wall 15 b at the center of the support base 15.

  The solid electrolyte membrane 3 is formed so as to cover the fuel electrode portion 15 a of the support base, and the air electrode 4 is formed on the solid electrolyte membrane 3 to constitute the power generation element 16. The bottom surface of the support base 15 is covered with a dense interconnector film 30. The side surfaces of the support portions 15 c and 15 d are covered with a dense film 31. The mixed gas chamber 9 is open on the gas inlet side but closed on the outlet side by a closing portion 18. Further, the reformed gas chamber 8 is closed at the inlet side by the closing portion 17 but is open at the outlet side.

  A mixed gas containing at least an organic fuel and water vapor is supplied into the mixed gas chamber 9 as indicated by an arrow E. This mixed gas flows through the mixed gas chamber 9 and permeates through the porous partition wall 15b as indicated by an arrow D. The mixed gas is reformed while being in contact with the porous partition wall 15b and passing through the porous partition wall 15b, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 16. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by an arrow B.

  In the cell 20F of FIG. 8, the fuel electrode and the interconnector are integrally formed to form an integral support base 15A. A plurality of reformed gas chambers 8 and mixed gas chambers 9 are formed in the support base 15A. FIG. 8A is a front view of the cell 20F viewed from the inlet side of the mixed gas chamber 9, FIG. 8B is a side view of the cell, and FIG. It is the front view seen from the exit side.

  The support base 15A includes a fuel electrode 15a constituting the power generation element 16, a support portion 15d thereof, a porous partition wall 15b, a support portion 15c of the porous partition wall 15b, and a partition wall 15e of the adjacent reformed gas chamber 8. The fuel electrode 15a and the support portions 15c and 15d are continuous to form a plate-like support base. The reformed gas chamber 8 and the mixed gas chamber 9 are separated from each other by providing the porous partition wall 15b at the center of the support base 15A.

  The solid electrolyte membrane 3 is formed so as to cover the fuel electrode portion 15 a of the support base, and the air electrode 4 is formed on the solid electrolyte membrane 3 to constitute the power generation element 16. The bottom surface of the support base 15 is covered with a dense film 30. The side surfaces of the support portions 15 c and 15 d are also covered with the dense film 31. Each mixed gas chamber 9 is open on the gas inlet side, but is closed on the outlet side by a closing portion 18. In addition, each reformed gas chamber 8 is closed on the inlet side by the closing portion 17, but is open on the outlet side.

  A mixed gas containing at least organic fuel and water vapor is supplied into each mixed gas chamber 9 as shown by an arrow E. This mixed gas flows through each mixed gas chamber 9 and permeates through the porous partition wall 15b as indicated by an arrow D. The mixed gas is reformed while being in contact with the porous partition wall 15b and passing through the porous partition wall 15b, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 2. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by an arrow B.

  FIG. 9 shows a cell according to a reference example outside the present invention. In this example, a plurality of reformed gas chambers 8 are formed on the support base, and both reforming of the mixed gas and power generation by the reformed gas are performed in each reformed gas chamber 8.

  FIG. 10 is a perspective view showing a cell 20G similar to FIG. The internal structure of the cell 20G is the same as that shown in FIG. However, in this example, the longitudinal direction of each mixed gas chamber 9 (direction of the mixed gas flow E) and the longitudinal direction of each reformed gas chamber 8 (direction of the reformed gas flow B) intersect each other. Particularly preferably, they are substantially orthogonal.

  In the example of FIGS. 11 and 12, the fuel electrode and the interconnector are integrally formed, and an integral cylindrical support base 25 is formed. A plurality of reformed gas chambers 8 and one mixed gas chamber 9 are formed in the support base 25A. FIG. 11 (a) is a front view of the cell as viewed from the inlet side of the mixed gas chamber, FIG. 11 (b) is a side view of the cell, and FIG. 11 (c) is the outlet side of the reformed gas chamber. It is the front view seen from. FIG. 12 is a perspective view of the cell.

  The support base 25 includes a cylindrical fuel electrode 25a that constitutes the power generation element 16B, a cylindrical porous partition wall 25b, and a plurality of radial spoke connection portions 25c that connect the fuel electrode 25a and the porous partition wall 25b. ing. The fuel electrode 25a and the connecting portion 25c are continuous. The mixed gas chamber 9 is formed inside the porous partition wall 25b, and each reformed gas chamber 8 is formed by the fuel electrode 25a, the porous partition wall 25b, and a plurality of connecting portions 25c.

  The solid electrolyte membrane 3 is formed on the fuel electrode 25a of the support base, and the air electrode 4 is formed on the solid electrolyte membrane 3 to constitute the power generation element 16B. Each mixed gas chamber 9 is open on the gas inlet side, but is closed on the outlet side by a closing portion 18. In addition, each reformed gas chamber 8 is closed on the inlet side by the closing portion 17, but is open on the outlet side.

  A mixed gas containing at least organic fuel and water vapor is supplied into each mixed gas chamber 9 as shown by an arrow E. The mixed gas flows in each mixed gas chamber 9 and permeates through the porous partition wall 25b as shown by an arrow D. The mixed gas is reformed while being in contact with the porous partition wall 25b and passing through the porous partition wall 25b, and oozes out into the reformed gas chamber 8 as a reformed gas containing hydrogen and carbon monoxide. An electrochemical reaction occurs in the power generation element 16B. Thereafter, the exhaust gas is discharged from each reformed gas chamber 8 as indicated by an arrow B.

Although the material which can be used as a solid electrolyte will not be specifically limited if it has ionic conductivity, The following can be illustrated.
Solid solution of neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), yttria (Y ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), calcium oxide (CaO), scandium oxide (Sc ₂ O ₃ ), etc. Stabilized zirconia and partially stabilized zirconia.
Ceria (CeO ₂ ) in which neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), yttria (Y ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ) and the like are dissolved. Lanthanum gallate (LaGaO ₃ ) in which Sr, Mg, Co, etc. are dissolved.

  The material of the air electrode is preferably a perovskite complex oxide containing lanthanum, more preferably lanthanum manganite or lanthanum cobaltite, and even more preferably lanthanum manganite. More preferably, a mixture of lanthanum manganite and zirconia is preferable. Lanthanum manganite may be doped with strontium, calcium, chromium, cobalt, iron, nickel, aluminum or the like.

  In addition, palladium, platinum, ruthenium, platinum-zirconia cermet, palladium-zirconia cermet, ruthenium-zirconia cermet, platinum-cerium oxide cermet, palladium-cerium oxide cermet, ruthenium-cerium oxide cermet, etc. may be used as the air electrode material. is there.

  Examples of the material for the fuel electrode include nickel, palladium, platinum, ruthenium, and alloys thereof. Preferably, from the viewpoint of compatibility with the thermal expansion coefficient of the electrolyte material and durability, it is particularly preferable to use a sintered body of a mixed powder of these metal particles and solid electrolyte particles. Examples of solid electrolyte particles include zirconia and ceria. Particularly preferably, the metal particles are made of nickel, and the solid electrolyte particles are made of stabilized or partially stabilized zirconia.

  The material of the porous partition wall is composed of a material having catalytic ability capable of steam reforming hydrocarbon fuels such as methane and propane, and the porosity is preferably 30 to 70% from the viewpoint of air permeability. The material of the porous partition wall can be composed of the same material as the fuel electrode material. It is also possible to form porous bodies with non-catalytic materials such as alumina, zirconia, silica, mullite, cordierite and other ceramics, iron-chromium alloys, and stainless steel, and use it as a catalyst. . The catalyst is a material containing nickel, iron, copper, platinum, palladium, ruthenium or the like.

  The interconnector material can be Fe-Cr alloy, stainless steel, and heat-resistant alloys such as Inconel. In ceramics, lanthanum chromite and lanthanum chromite added with calcium or strontium can be raised. In either case, it is required to be airtight.

Examples of organic fuels include alkane fuels derived from petroleum such as methane, ethane, propane, and butane, petroleum fuels such as gasoline, via and naphtha, and alcohol fuels such as methanol and ethanol.
The water vapor concentration in the mixed gas is not particularly limited. For example, when methane is used, the water vapor / methane ratio (Steam / Carbon ratio, S / C) can be about 2 to 5, and it should be 2 to 3. Further preferred.

The method for assembling the power generation element and the porous partition wall is not particularly limited.
(1) For example, a battery can be assembled by producing a power generation element, separately producing a porous partition, and laminating the power generation element and the porous partition.
(2) A power generation element is manufactured, and a porous partition is manufactured separately, and the power generation element and the porous partition are joined and joined together with a bonding member or the like.
(3) When producing the power generation element, the fuel electrode and the porous partition wall can be integrally formed as described above.

  The method for producing the SOFC of the present invention is not limited. For example, the method for forming the green molded body for the fuel electrode is not limited, and may be an ordinary ceramic molding technique such as a doctor blade method, a dip method, an extrusion method, or a die press molding method. The method for forming the fuel electrode coating layer is not limited, and a known film forming method such as screen printing, dip coating, or casting is preferable.

  The method for forming the green molded body of the solid electrolyte membrane is not limited, and may be a normal ceramic forming technique such as a doctor blade method, a dip method, or an extrusion method. When molded by the doctor blade method, polyethylene glycol, polyalkylene glycol, dibutyl phthalate, etc. as plasticizers other than the above binder, glycerin, oleic acid, sorbitan triol, etc. as peptizers, toluene, ethanol, butanol etc. as solvents preferable.

  The green molded body of the solid electrolyte membrane is preferably a molded body obtained by molding a mixture obtained by mixing an organic binder and water (solvent) with the main raw material of the solid electrolyte membrane. As the organic binder, those described above can be used. When the weight of the main raw material is 100 parts by weight, the amount of the organic binder added is preferably 0.5 to 20 parts by weight.

  The method for forming the porous partition wall is not limited, and may be an ordinary ceramic forming technique such as a doctor blade method, a dip method, or an extrusion method. In the case of molding by the doctor blade method, polyethylene glycol, polyalkylene glycol, dibutyl phthalate, etc. as plasticizers other than the above binder, glycerin, oleic acid, sorbitan triol, etc. as peptizers, toluene, ethanol, butanol etc. as solvents And preferred.

Further, in order that the porous wall has higher filter performance and reforming performance, it is preferable to control the pore diameter. For example, the mixed gas chamber side of the porous wall has coarse pores from the viewpoint of air permeability. From the viewpoint of reforming performance, it is preferable that the reformed gas chamber side has fine pores. Such a double-layered wall is more effective. In such an embodiment, the pore diameter on the mixed gas chamber side of the porous wall is preferably 20 μm to 100 μm, the pore diameter on the reformed gas chamber side is preferably 5 μm to 20 μm, and the difference between the two is 20 μm. The above is preferable.
Such a double-structured porous partition wall is prepared by, for example, pressing a sheet by a doctor blade method, which forms coarse pores after sintering, and a sheet, which forms fine pores after sintering, and firing them simultaneously. There is a way.

  In addition to the above-described method of forming a raw material that is a catalyst mixed with a raw material in advance, there is also a method for supporting a catalytic material by forming a porous material and then immersing the porous material in a slurry of the catalytic material. Is possible.

[Example 1]
The SOFC cell described with reference to FIG. 3 was produced.
(Preparation of solid electrolyte plate 3)
Put an alumina ball with a diameter of 10 mm in a nylon container, add 100 parts by weight of 3 mol yttria-added zirconia (3YSZ) and 20 parts by weight of toluene, 11 parts by weight of ethanol, and 2 parts by weight of butanol at a rotational speed of the mill of 60 rpm. Ball mill mixed. Thereafter, 8 parts by weight of polyvinyl butyral, 3 parts by weight of dibutyl phthalate, 26 parts by weight of toluene and 15 parts by weight of ethanol were added to this mixture, followed by ball mill mixing. The obtained slurry was formed into a sheet on a polyethylene terephthalate sheet (thickness 100 μm) by the doctor blade method, and a green compact (solid electrolyte) of 3 mol% yttria-added zirconia (3YSZ) having a width of 50 mm and a thickness of 400 μm. Membrane compacts) were prepared.
This was cut into a square flat plate having a length of 130 mm and a width of 130 mm and fired at 1400 ° C. for 1 hour to obtain a dense solid electrolyte plate 3 having a thickness of about 200 μm.

(Fabrication of fuel electrode 5)
Nickel oxide powder having an average particle diameter of 0.6 μm and 8 mol% yttria-stabilized zirconia (8YSZ) powder having an average particle diameter of 0.5 μm were weighed to a weight ratio of 1: 1, and then 100 parts by weight of the mixed powder and alkyl Acetated polyvinyl alcohol (3 parts by weight) and TVneol (30 parts by weight) were mixed in an alumina mortar to form a paste. The kneaded material thus obtained was printed on a solid electrolyte plate with a # 80 screen, dried, and baked at a temperature of 1350 ° C. for 1 hour. The fuel electrode thickness at this time was 30 μm.

(Production of air electrode 4)
A mixed powder of 50 parts by weight of lanthanum manganite powder having an average particle size of 1 μm and 50 parts by weight of 3YSZ powder having an average particle size of 0.3 μm was prepared. 30 parts by weight of neol was mixed with an alumina mortar to form a paste. The kneaded material thus obtained was printed on a # 80 screen, dried, and baked at a temperature of 1200 ° C. for 1 hour. The film thickness at this time was 50 μm.

(Preparation of porous partition wall 10A)
After weighing nickel oxide powder having an average particle diameter of 1 μm and 8YSZ powder having an average particle diameter of 1 μm to a weight ratio of 1: 1, an organic binder and water are added and wet-mixed in a ball mill, and the mixture is dried. Granulated. This granulated powder was molded in a mold and pressed at ² t / cm ² by CIP to produce a porous wall molded body having a thickness of 3 mm. This was baked at 1400 ° C. for 2 hours and processed into a length of 100 mm, a width of 100 mm and a thickness of 1 mm, and a groove 10a was formed on one side by grinding to form a porous partition.

(Preparation of interconnector plate 1B)
An organic binder and water were added to a calcium-added lanthanum chromite powder having an average particle size of 0.5 μm and wet-mixed in a ball mill, and the mixture was dried and granulated. This granulated powder was molded in a mold and pressed at ² t / cm ² by CIP to produce a porous wall molded body having a thickness of 3 mm. This was fired at 1600 ° C. for 4 hours to obtain a dense sintered body. This was processed into a length of 100 mm, a width of 100 mm, and a thickness of 1 mm, and a groove 11 was formed on one side by grinding to form an interconnector plate 1B.

[Example 2]
The SOFC cell described with reference to FIG. 4 was produced.
(Manufacture of molded body for solid electrolyte 3)
Put an alumina ball with a diameter of 10 mm in a nylon plastic container, add 100 parts by weight of 3 mol yttria-added zirconia (3YSZ) and 20 parts by weight of toluene, 11 parts by weight of ethanol, and 2 parts by weight of butanol as the solvent. And ball mill mixing. Thereafter, 8 parts by weight of polyvinyl butyral, 3 parts by weight of dibutyl phthalate, 26 parts by weight of toluene and 15 parts by weight of ethanol were added to this mixture, followed by ball mill mixing. The obtained slurry was formed into a sheet on a polyethylene terephthalate sheet (100 μm thick) by the doctor blade method, and a green compact (solid electrolyte) of 3 mol% yttria-added zirconia (3YSZ) with a width of 50 mm and a thickness of 20 μm. A molded body for film 3) was prepared.

  The fuel electrode was divided into a part made of fine particles having high activity contributing to the electrochemical reaction and a part having a structural strength as a substrate. The former is the first fuel electrode and is formed of a thin film. The latter is used as the second fuel electrode, and is formed into a honeycomb shape integrated with the porous wall.

(Manufacture of first fuel electrode layer coating layer)
A nickel oxide powder having an average particle diameter of 0.6 μm and an 8 mol% yttria-stabilized zirconia (8YSZ) powder having an average particle diameter of 0.5 μm are weighed to a weight ratio of 1: 1, and an organic binder and a solvent are added to the mixed powder. The mixture was added and mixed in an alumina mortar to form a paste. Thereafter, screen printing was performed on the solid electrolyte membrane molded body to form a first fuel electrode layer coating layer. The film thickness of screen printing at this time was 15 μm.

(Formation of second molded product for fuel electrode layer)
After weighing nickel oxide powder having an average particle diameter of 1 μm and 8YSZ powder having an average particle diameter of 1 μm to a weight ratio of 1: 1, an organic binder and water are added and wet-mixed in a ball mill, and the mixture is dried. Granulated. This granulated powder was molded in a mold to produce a second molded body for the fuel electrode layer having a thickness of 3 mm.

  In addition, it is preferable that the green molded object for fuel electrodes and the coating layer for fuel electrode layers consist of the mixture which mixed the organic binder, the pore former, and water with each raw material. Examples of the organic binder include polymethyl acrylate, nitrocellulose, polyvinyl alcohol, polyvinyl butyral, methyl cellulose, ethyl cellulose, starch, wax, acrylic acid polymer, and methacrylic acid polymer. When the weight of the main raw material is 100 parts by weight, the addition amount of the organic binder is preferably 0.5 to 5 parts by weight.

(Integration of solid electrolyte / first fuel electrode layer / second fuel electrode layer)
The produced solid electrolyte molded body, the first fuel electrode layer coating layer, and the second fuel electrode layer molded body were laminated. This laminate was covered with a vacuum bag film bag and cold isostatic pressed (pressure: ² ton / cm ² holding time: 1 minute). The obtained press-molded body was taken out from the mold and the film was peeled off to obtain a press-molded body.

The pressure at the time of cold isostatic pressing the stack, from the viewpoint of enhancing the adhesion of each green body of the laminate, 500 kgf / cm ² or more, more preferably to 1000 kgf / cm ² or more, pressure Is practically 10 tf / cm ² or less. The firing temperature is usually 1200 ° C to 1700 ° C.

(Baking of pressure-molded body)
This pressure-molded body was fired in air at a maximum temperature of 1400 ° C. for 2 hours to obtain a laminated sintered body. After that, it was processed into a length of 100 mm and a width of 100 mm to a total thickness of 2 mm, and a flow path with a width of 2 mm and a depth of 0.5 mm was provided on the second fuel electrode substrate surface by grinding.

(Production of air electrode 4)
100 parts by weight of lanthanum manganite powder having an average particle size of 1 μm, 3 parts by weight of alkyl acetate polyvinyl alcohol, and 30 parts by weight of TVneol were mixed in an alumina mortar to form a paste. The kneaded material thus obtained was printed on a # 80 screen, dried, and baked at a temperature of 1200 ° C. for 1 hour.

(Preparation of porous partition wall 10)
An alumina ball having a diameter of 10 mm is placed in a nylon plastic container, nickel oxide powder having an average particle diameter of 1 μm and 8 YSZ powder having an average particle diameter of 1 μm are mixed in a weight ratio of 100 parts by weight and 20 parts by weight of toluene as a solvent. 11 parts by weight of ethanol and 2 parts by weight of butanol were added, and ball mill mixing was performed at a mill rotation speed of 60 rpm. Thereafter, 8 parts by weight of polyvinyl butyral, 3 parts by weight of dibutyl phthalate, 26 parts by weight of toluene and 15 parts by weight of ethanol were added to this mixture, and carbon powder was added as a pore-forming agent for adjusting the porosity, followed by ball mill mixing. Did. The obtained slurry was subjected to sheet molding on a polyethylene terephthalate sheet (thickness: 100 μm) by a doctor blade method to prepare a green molded body of 3 mol% yttria-added zirconia (3YSZ) -nickel oxide having a width of 200 mm.

  This was cut into a square shape and fired at 1400 ° C. for 1 h to obtain a porous partition wall having a thickness of about 200 μm, a length of 100 mm, and a width of 100 mm.

(Preparation of interconnector plate 21)
An organic binder and water were added to a calcium-added lanthanum chromite powder having an average particle size of 0.5 μm and wet-mixed in a ball mill, and the mixture was dried and granulated. This granulated powder was molded in a mold and pressed with CIP at 2 t / cm ² to produce a molded product having a porous partition wall thickness of 3 mm. This was fired at 1600 ° C. for 4 hours to obtain a dense sintered body. This was processed to a length of 100 mm, a width of 100 mm, and a thickness of × 2 mm, and grooves were formed on both sides by grinding to form a porous partition wall.

[Example 3: Power generation test]
A power generation element 2, a porous partition wall 10 and an interconnector plate 1B shown in FIG. 5 were produced by the same manufacturing method as the structure shown in Example 2, and a power generation test was conducted by stacking them. Size is 20mm x 50mm x for single cell test
A 4.2mm cell was prepared, set in a power generation test device, and an internal reforming power generation test using methane was conducted. A platinum mesh was brought into contact with the air electrode portion and the interconnector portion to form a current collector. The temperature was raised while flowing air to the air electrode side and flowing nitrogen to the fuel electrode side supply hole. After reaching 800 ° C., the gas on the fuel electrode side stopped nitrogen and allowed hydrogen to flow. As a result, the nickel oxide contained in the fuel electrode and the porous partition wall was reduced to metallic nickel. After 4 hours when the open-circuit voltage was almost stabilized, power generation was performed at a constant current of 0.3 A / cm ² for 24 hours. After that, the current was turned off, and then switched to supply of argon-diluted methane to which water vapor was added. After the voltage stabilized, a constant current discharge of 0.3 A / cm ² was performed, and the power generation output was measured. The output after 5 hours from the supply of methane and the output after 100 hours were measured. The test was performed in the same manner as the above procedure with the steam / methane ratio (S / C) changed as shown in Table 1.

(Comparative Example 1)
Similarly, a power generation test was conducted using a cell having a structure without a porous wall.

  While the output change rates of the examples (1-1 to 1-3) are all zero, the comparative examples (1- (1) to 1- (2)) have a large change rate of 10% or more. Deterioration is recognized. As a result of disassembling and observing the cell after the power generation test, in the comparative example, carbon deposition was observed on the surface of the fuel electrode and blackened, whereas in the example, carbon deposition was observed on the surface of the fuel electrode. There wasn't. In the examples, although carbon deposition was observed on the surface of the porous wall in the second space, the power generation performance was not affected.

[Example 4]
The SOFC cell 20F described with reference to FIG. 8 was produced and a power generation test was performed.
(1) Raw material preparation 3 wt% of methylcellulose, 7 wt% of cellulose, 3 wt% of polyvinyl alcohol, and 100 wt% of powder mixed with 8 YSZ powder with an average particle diameter of 3 μm and nickel oxide powder with an average particle diameter of 1 μm in a weight ratio of 1: 1. And 18 wt% water was mixed.

  The mixture prepared according to the above composition was kneaded for 3 hours with a pressure kneader to obtain a kneaded product. The kneaded material is formed into a cylindrical shape of φ50mm x 300mm with a vacuum kneader to make clay.

(Extruded molding)
The cylinder of the extrusion molding machine is filled with clay, and a honeycomb molded body having a pitch of 3 mm, a wall thickness of 200 μm, a length of 3 mm, a width of 18 mm, and a length of 300 mm and 2 × 6 through holes is produced. This was stored in a constant temperature and humidity dryer, and dried at 80 ° C. for 10 hours while appropriately adjusting the humidity.

(Sealed at one end)
Then, it was housed in an electric furnace, heated to 1200 ° C. at a rate of 100 ° C./h, held for 1 hour, and then cooled at a rate of 200 ° C./h. The calcined body thus obtained was sealed with a rubber stopper at one end of the reformed gas chamber 8 and one end of the mixed gas chamber 9 at the end, and 8 mol% yttria-stabilized zirconia and Walls 17 and 18 are formed in openings other than those sealed with rubber stoppers by immersing only the ends in a nickel oxide mixture slurry. This was stored in a constant temperature and humidity dryer, dried at 80 ° C., and then the rubber stopper was removed.

(Baking)
It was housed in an electric furnace, heated to 1600 ° C. at a rate of 100 ° C./h, held for 3 hours, and then cooled at a rate of 200 ° C./h. In this way, it is possible to form a substrate whose end is sealed. The honeycomb structure thus obtained was used as a cell support base 15A.

(Preparation of interconnector film 30)
3 wt% of ethylcellulose was added to Ca-doped lanthanum chromite powder having an average particle diameter of 1 μm, and a solvent was added to obtain a printing paste. Using this paste, it was applied to one side of the honeycomb substrate by screen printing. After evaporating the solvent in a dryer at 120 ° C., this was baked at 1600 ° C. to obtain an interconnector film 30.

(Preparation of solid electrolyte membrane 3)
100 parts by weight of 8YSZ powder having an average particle diameter of 0.5 μm, 3 parts by weight of alkyl acetate polyvinyl alcohol, and 30 parts by weight of TVneol were mixed in an alumina mortar to form a paste. The kneaded material thus obtained was printed on one side of the substrate with a # 200 screen. Then, it dried and baked at 1400 degreeC for 2 hours.

(Production of air electrode 4)
To a La0.7Sr0.3MnO3 powder having a particle size of 1 μm, 2 wt% of ethylcellulose was added and a solvent was added to obtain a printing paste. Using this paste, a rectangular shape was applied on the electrolyte. After evaporating the solvent in a dryer at 120 ° C., the solvent was baked at 1200 ° C. to form the air electrode 4.

(Ensuring airtightness on the side)
On the side surfaces, a zirconia-based ceramic paste was applied to form a dense film 31 to ensure airtightness.

(Cell of Comparative Example 2)
As a comparative example, a honeycomb substrate having 1 row × 6 through-holes was prepared, and a structure without open porous walls with both ends open was prepared (see FIG. 9). The clay was produced by adopting the same composition as the clay shown in the above examples. Drying and firing were performed in the same manner as in the above example, and the solid electrolyte membrane 3, the air electrode 4, the interconnector membrane 30, and the dense membrane 30 were formed in the same manner.

(Power generation test)
Using the cell thus prepared, a power generation test was performed in the same manner as described above. The results are shown in Table 2.

  The output change rates of the examples (2-1 to 2-3) were all zero, while the comparative examples (2- (1) to 2- (2)) showed a large change rate. As a result of disassembling and observing the cell after the power generation test, in the comparative example, carbon deposition was observed on the surface of the fuel electrode and blackened, whereas in the example, carbon deposition was observed on the surface of the fuel electrode. There wasn't. In the examples, although carbon deposition was observed on the porous partition wall surface of the mixed gas chamber, the power generation performance was not affected.

It is sectional drawing which shows the conventional internal reforming type SOFC typically. (A) is sectional drawing which shows typically the cell 20A which concerns on one Embodiment of this invention, (b) is a perspective view of the cell 20A of Fig.2 (a). It is a perspective view which shows the cell 20B which concerns on embodiment of this invention. It is a perspective view which shows the cell 20C which concerns on other embodiment of this invention. It is a perspective view which shows cell 20D which concerns on other embodiment of this invention. FIG. 6A is a front view of the cell 20E viewed from the inlet side of the mixed gas, FIG. 6B is a side view of the cell, and FIG. 6C is a view of the cell viewed from the outlet side of the reformed gas chamber. FIG. It is a perspective view of the cell 20E. (A) is the front view which looked at the cell 20F from the entrance side of the mixed gas chamber 9, (b) is the side view of the cell, (c) looked at the cell from the exit side of the reformed gas chamber 8. It is a front view. It is a cross-sectional view which shows the cell which concerns on the reference example outside this invention. It is a perspective view which shows the same cell 20G as FIG. (A) is the front view which looked at the cell 20H from the entrance side of the mixed gas chamber, FIG.11 (b) is a side view of a cell, FIG.11 (c) is a cell from the exit side of a reformed gas chamber FIG. It is a perspective view of the cell 20H.

Explanation of symbols

  1, 1A, 1B, 21 Interconnector 2, 2A, 16 Power generation element 3 Solid electrolyte membrane 4 Air electrode 5, 5A Fuel electrode 6 Oxidizing gas chamber 8 Reformed gas chamber 9 Mixed gas chamber 10, 10A Porous partition walls 20A, 20B , 20C, 20D, 20E, 20F cells

Claims (9)

A solid oxide fuel cell for reforming a mixed gas containing organic fuel and water vapor to generate electric power,
A solid electrolyte type comprising a power generation element including a fuel electrode, an air electrode and a solid electrolyte membrane, and a porous partition wall having a function of reforming the mixed gas to generate a reformed gas Fuel cell.   The cell according to claim 1, wherein a mixed gas chamber for supplying the mixed gas and a reformed gas chamber between the fuel electrode and the porous partition wall are formed.   The cell according to claim 2, wherein an outlet side of the mixed gas chamber is closed.   The cell according to claim 2 or 3, wherein an inlet side of the reformed gas chamber is closed.   The cell according to any one of claims 1 to 4, wherein the fuel electrode and the porous partition wall are integrated to form a support base of the power generation element.   The cell according to claim 5, wherein a plurality of the mixed gas chambers are provided in the support base.   The cell according to claim 5 or 6, wherein a plurality of the reformed gas chambers are provided in the support substrate.   The cell according to any one of claims 5 to 7, wherein the support base has a plate shape.   The cell according to any one of claims 5 to 7, wherein the support base has a cylindrical shape.

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