JPH07240214A - Base body tube for inner reform for solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To suppress carbon production and improve the durability of electrodes by dispersing and carrying Ni fine particles of suitable shapes for a catalyst in a calcia-stabilized zirconia which is a base body tube composing material. CONSTITUTION:Ni of 0.1mum or smaller particle size is mixed with calcia- stabilized zirconia(CSZ), the mixture is granulated, formed into a cylindrical shape, sintered at 1600-1700 deg.C to provide a porous base body tube 1 for inner reform, and a cermet of Ni and yttria-stabilized zirconia(YSZ) is plasma sprayed to form a film which is used as a fuel electrode 2. Further, an electrolyte 3 which is plasma-sprayed film of an oxygen ion conductive YSZ, an air electrode 4 composed of an acetylene-flame-sprayed film of LaCoO3, and an interconnector 5 composed of NiAl are formed to compose a fuel cell. Since methane is reacted with steam to be reformed in the base body tube 1 by an Ni fine particle catalyst carried on the CSZ before the methane, which is a fuel, reaches the fuel electrode 2, carbon production is little and the durability of the catalyst is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate tube for internal reforming of a solid oxide fuel cell.

[0002]

2. Description of the Related Art FIG. 3 schematically shows a conventional internal reforming substrate tube of a solid oxide fuel cell. As shown in the figure, the thermal spraying type solid electrolyte (SOFC) is a plasma sprayed cermet of Ni and yttria stabilized zirconia (YSZ) as a fuel electrode 02 on a calcia-stabilized zirconia (CSZ) porous cylindrical substrate tube 01. Then, oxygen ion conductive YSZ is formed as the electrolyte 03 by plasma spraying. Then, a LaCoO ₃ film is formed as an air electrode 04 on this by acetylene flame spraying to form a fuel cell. The fuel electrode 02 and the air electrode 03 are connected to each other in series by an interconnector 05 formed of a cermet of NiAl and alumina.

The solid electrolyte fuel cell generally has a high oxygen ion conductivity of YSZ at about 700 to 1000 ° C.,
By supplying air to the air electrode and hydrogen or carbon monoxide to the fuel electrode to reduce the oxygen partial pressure on the fuel electrode side, a potential difference is generated between the electrodes. When a load is connected between the electrodes and an electric current is applied, oxygen ions move from the air electrode in the electrolyte to the fuel electrode and react with hydrogen and carbon monoxide in the fuel electrode. A fuel cell continuously generates this reaction by supplying a fuel to cause this reaction.

In the solid electrolyte fuel cell, about 700
In order to cause the reaction from 1000 to 1000 ° C., methane and steam are directly supplied to cause a steam reforming reaction using Ni of the fuel electrode as a catalyst to produce hydrogen and carbon monoxide, which can be used as a fuel. . At this time, an endothermic reaction occurs and the amount of heat generation increases. In a solid electrolyte fuel cell, heat is generated due to the resistance of the cell.Therefore, by cooling this heat by absorbing heat by a steam reforming reaction, the exhaust heat of the solid electrolyte fuel cell can be recovered as the calorific value of the fuel, thus improving power generation efficiency. You can This is called "internal reforming".

[0005]

By the way, in the reforming reaction of methane, carbon is generated when the temperature is high, and the form of Ni used for the fuel electrode of the fuel cell does not always match the form suitable for the catalyst. . Since Ni used for the fuel electrode needs to flow an electric current, Ni needs to be continuously connected.

However, Ni used as a catalyst must have a large surface area and must be dispersed in fine particles on a carrier such as alumina in order to prevent burning at high temperatures. For this reason, the shape suitable for the electrode is not the shape suitable for the catalyst, carbon is generated in the fuel electrode by internal reforming, and the fuel electrode structure is destroyed to deteriorate the fuel electrode electrode performance of the SOFC. Further, there is a problem that the reaction activity is low and the durability is poor even if carbon is not generated.

In view of the above problems, it is an object of the present invention to provide a base tube for internal reforming of a solid oxide fuel cell, which has high reaction activity and improved durability.

[0008]

The structure of a substrate tube for internal reforming of a solid oxide fuel cell which achieves the above-mentioned object is suitable for a catalyst as a constituent material of the substrate tube of a thermal spraying type solid oxide fuel cell. It is characterized in that fine particles of Ni having a different shape are mixed and supported by dispersion.

[0009]

In order to disperse fine particles of Ni having a shape suitable for a catalyst in the base tube, a steam reforming reaction occurs in the base tube before methane reaches the SOFC fuel electrode, and changes into hydrogen and carbon monoxide.
Further, the Ni dispersed in the fuel electrode has a shape suitable for the reforming reaction, has a high reaction activity, and has a high catalyst durability because sintering of Ni hardly occurs even at the operating temperature of SOFC.

[0010]

EXAMPLE A preferred example of the present invention will be described.

FIG. 1 (A) is a schematic view of a substrate tube according to this embodiment, FIG. 1 (B) is a sectional view of part A of FIG. 1 (A), and FIG.
It is a B section enlarged view of (B). CSZ forming the substrate tube 1 shown in FIG. 1 and Ni having a particle diameter of 0.1 micron or less are mixed and granulated to prepare particles in which CSZ11 carries fine particles Ni12 as shown in FIG. Then, this is formed into a cylindrical shape by a hydrostatic press, and the temperature is about 1600 to 1700 ° C.
Then, the porous substrate tube 1 is manufactured by sintering. A cermet 2 of Ni and yttria-stabilized zirconia (YSZ) is formed as a fuel electrode 2 on this substrate tube 1 by plasma spraying, and an oxygen ion conductive YSZ as an electrolyte 3 is formed thereon by plasma spraying. LaCo as the air electrode 4 on this
A film of O _{3 is formed} by acetylene flame spraying to form a fuel cell. These are connected in series by connecting the fuel electrode 2 and the air electrode 3 with an interconnector 5 formed of a cermet of NiAl and alumina (see FIG. 1).

SOFC is heated from 700 ° C. to 1000 ° C. to supply methane and steam into the inside of the base tube on the fuel electrode side. Methane causes a reforming reaction while diffusing into the fuel electrode in the substrate tube, and is converted into hydrogen and carbon monoxide. At the fuel electrode, oxygen ions that have moved through the electrolyte react with hydrogen and carbon monoxide to form water vapor and carbon dioxide, which diffuse through the fuel electrode substrate tube and move into the fuel. Methane is N suitable for the reaction
In order to cause a steam reforming reaction in the substrate tube 1 containing the i catalyst,
It does not easily generate carbon, has high catalytic activity, and has a fast reaction rate.

[0013]

As described above, in the internal reforming substrate tube of the solid oxide fuel cell according to the present invention, since Ni is dispersed in CSZ which is a constituent element of the substrate tube, the sintering of Ni does not occur. Since it is suppressed, the durability of the catalyst is also high. Further, even when carbon is generated, there is no carbon generation at the fuel electrode, so there is no change in electrode characteristics and no SOFC performance change.

[Brief description of drawings]

FIG. 1 is a schematic view of a base pipe according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a base pipe according to an embodiment of the present invention.

FIG. 3 is a schematic view of a base tube according to a conventional example.

[Explanation of symbols]

 1 Base Tube 2 Fuel Electrode 3 Electrolyte 4 Air Electrode 5 Interconnector 11 CSZ Particle 12 Ni Fine Particle

Claims (1)

[Claims] 1. An internal reforming of a solid electrolyte fuel cell, characterized in that, in a base tube of a thermal spraying type solid electrolyte fuel cell, fine particles of Ni having a shape suitable for a catalyst are mixed and carried on a constituent material of the base tube. Quality substrate tube.