JP2003176119A - Method and apparatus for producing silicon carbide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing silicon carbide, by which an inexpensive raw material such as a carbide of chaff can be used as a raw material in addition to conventional raw materials and high purity green silicon carbide is produced at a low energy and an apparatus therefor. <P>SOLUTION: Powdery green silicon carbide is produced at a low energy cost by using a mixture of a carbide of a silicon-accumulating biomass as a raw material such as the carbide of chaff or a carbon powder and a silica powder, and irradiating the raw material with high frequency electromagnetic waves of ≥2 GHz. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method and a manufacturing apparatus for manufacturing silicon carbide by irradiating a high-frequency electromagnetic wave with silicon-accumulated biomass carbide or a mixture of carbon powder and silica powder as a raw material. It is a thing. Examples of the silicon-accumulated biomass include rice husks, straw, bamboo leaves, and corn.

[0002]

2. Description of the Related Art Generally used silicon carbide manufacturing methods include a manufacturing method using a solid phase reaction by an Acheson furnace method (resistance furnace method) and a silicon-carbon direct reaction method.

The Acheson furnace method, which is widely used on an industrial scale, uses carbon such as petroleum coke and silica as main raw materials,
A mixture sample of silica and carbonaceous material is laid between the electrodes, the electrodes are connected with a graphite powder core, and after covering with the raw material, electricity is applied, and then 1400 to 160 by Joule heat in a reducing atmosphere.
It is manufactured by forming a temperature range of 0 ° C., firing it to form an ingot (lump), crushing and refining.

[0004]

In the conventional method, a large amount of electric power is required due to the indirect heating and the holding time of 2 to 3 hours required for the solid phase reaction in the high temperature range. In terms of raw materials, carbon such as petroleum coke is used, which makes the raw materials expensive.

There are green silicon carbide and black silicon carbide in silicon carbide, and black silicon carbide contains impurities such as iron and aluminum several times more than green silicon carbide. To produce high-purity green silicon carbide, a reaction in a high temperature range of 1600 ° C. or higher is required.

The inventors of the present invention have made it a challenge to solve the problems of low energy consumption during production and availability of inexpensive raw materials, and have studied a method of producing high-purity green silicon carbide with low energy.

[0007]

In order to solve the problem of low energy cost, the present invention utilizes the high frequency electromagnetic wave absorption characteristics of carbon and carbide and uses a high frequency electromagnetic wave irradiation device of 2 GHz or more to produce the raw material itself. Is used as a heating element to carry out the synthesis reaction in an extremely short time.

In the apparatus for producing silicon carbide according to the present invention, by enclosing the raw material with a high refractory and high heat insulating material, it is possible to minimize the diffusion of thermal energy necessary for the synthesis reaction of silicon carbide to the surroundings and to reduce the frequency. By irradiating a high frequency electromagnetic wave of 2 GHz or more, heat energy is supplied from the inside of the raw material until the synthesis reaction is completed,
It can reach 1400 ° C. or higher in an extremely short time and can produce crystalline powdery green silicon carbide.

In the present invention, in order to solve the problem of cost reduction of raw materials, the above-mentioned silicon-enriched biomass carbide can be used as a main raw material. Among them, rice husk has a low utility value as agricultural waste material. It is cheap. Furthermore, since rice husks have been accumulated by the introduction of an integrated rice-polishing method (rice center) in recent years, it is a promising raw material because it is easily industrially used. The main compositional characteristic of rice husk carbide is that about 18% of silica and about 80% of carbon are dispersed very uniformly. Moreover, since the silica component in the silicon-accumulated biomass exists in the form of silica gel and is amorphous, it has higher reactivity than the silica component in the mineral, leading to a reduction in energy cost.

The reaction process according to the present invention is as follows.
The main components of the raw materials are silica (SiO ₂ ) and carbon (C). By irradiating this raw material with a high frequency electromagnetic wave of 2 GHz or more, the electromagnetic wave energy is absorbed by the raw material and becomes thermal energy. Due to this heat, a part of carbon in the raw material is burned, the temperature rises, and oxygen in the air is consumed by the burning of carbon to form a reducing atmosphere.
When the temperature becomes high in the reducing atmosphere, a part of carbon in the raw material deprives the oxygen of silica in the raw material and burns, and the oxygen-deprived silicon is combined with carbon to form silicon carbide (SiO 2).
₂ + 3C → SiC + 2CO). In this way, the carbon in the raw material has a portion that becomes the raw material of silicon carbide and a portion that becomes the fuel,
The reaction can be promoted extremely efficiently.

For optimum amounts of silica and carbon as raw materials, the reaction of the raw materials (SiO ₂ + 3C → SiC + 2CO)
The stoichiometric ratio of the portion that contributes to is 1 mol of silica: 3 mol of carbon, and carbon for reacting with oxygen in the air may be added to this, and the optimum blending ratio can be easily obtained by calculation and experiment. I can.

[0012]

EXAMPLES Examples of producing silicon carbide according to the present invention will be described below. The following examples are for the purpose of deepening the understanding of the modes and effects of the present invention, and do not limit the present invention.

[0013]

Example 1 A commercially available rice husk carbide (rice husk charcoal) was used in an amount of 40 to 6
The material pulverized to 0 μm is used as a raw material. About 10g of this raw material
Enclosed with high fire resistance and high insulation, 2.5 GHz, output 500
It is installed in a high frequency electromagnetic wave irradiation device of W and irradiated for about 20 minutes. In this process, silicon carbide is synthesized, the reaction is completed, the electromagnetic wave absorption property is deteriorated, and the temperature is decreased. The mass of the powdery green silicon carbide recovered after the synthesis was about 1 g, and as a result of X-ray diffraction, it was found to be highly pure silicon carbide. This X-ray diffraction pattern is shown in FIG.

[0014]

Example 2 A commercially available rice husk carbide (rice husk charcoal) was used in an amount of 40 to 6
Mass ratio of crushed to 0 μm and commercially available silica powder is about 2:
The material mixed at a ratio of 1 is used as a raw material. About 10g of this raw material
Enclosed with high fire resistance and high insulation, 2.5 GHz, output 500
It is installed in a high frequency electromagnetic wave irradiation device of W and irradiated for about 20 minutes. In this process, silicon carbide is synthesized, the reaction is completed, the electromagnetic wave absorption property is deteriorated, and the temperature is decreased. The mass of the powdery green silicon carbide recovered after the synthesis was about 2 g, and as a result of X-ray diffraction, it was found to be high-purity silicon carbide. This X-ray diffraction pattern is shown in FIG.

[0015]

Example 3 A raw material is a mixture of a commercially available carbon powder and a commercially available silica stone powder in a mass ratio of about 3: 2. About 10 g of this raw material is surrounded by a high refractory and high heat insulating material, placed in a high frequency electromagnetic wave irradiation device of 2.5 GHz and output of 500 W, and irradiated for about 20 minutes. In this process, silicon carbide is synthesized, the reaction is completed, the electromagnetic wave absorption property is deteriorated, and the temperature is decreased. The mass of the powdery green silicon carbide recovered after the synthesis is about 2
As a result of X-ray diffraction, it was found to be silicon carbide with high purity. This X-ray diffraction pattern is shown in FIG.

[0016]

The production of silicon carbide according to the prior art requires a lot of energy, time and process, but according to the present invention, 10 g of hulled carbide or 10 g of a mixture of silica stone powder and carbon powder is used. By irradiating with a high-frequency electromagnetic wave irradiation device with an output of 500 W for about 20 minutes, about 1 to 2 g of powdery green silicon carbide can be easily manufactured. In addition, it is possible to expect high economic effects by applying it to industrial production scales, such as materials with low utility value as agricultural waste materials such as rice hulls. The green silicon carbide refined by the present invention has high purity, heat resistance, acid resistance, thermal shock resistance,
Since it has excellent hardness, it can be used as a material for a high temperature combustion catalyst structure support, a diesel engine exhaust gas filter, a semiconductor, an abrasive, and the like.

[Brief description of drawings]

1 is an X-ray diffraction pattern of silicon carbide manufactured in Example 1. FIG.

FIG. 2 is an X-ray diffraction pattern of silicon carbide manufactured in Example 2.

FIG. 3 is an X-ray diffraction pattern of silicon carbide manufactured in Example 3.

FIG. 4 is a schematic sectional view of the silicon carbide manufacturing apparatus used in Examples 1, 2 and 3.

Continued front page    (72) Inventor Hiromi Sarai             11-chome, Kita-ku, Kita-ku, Sapporo, Hokkaido             Inside the Hokkaido Industrial Test Station (72) Inventor Kazuhiko Kudo             11-chome, Kita-ku, Kita-ku, Sapporo, Hokkaido             Inside the Hokkaido Industrial Test Station (72) Inventor Kunitoshi Soba             32, Nopuro Matsunami-machi, Ebetsu City, Hokkaido             Inside the company dish F-term (reference) 4G046 MA14 MC02 MC06

Claims (4)

[Claims] 1. A silicon-accumulated biomass (silica (Si
O ₂ ) component of plant) carbide powder, frequency 2G
A method for producing silicon carbide, which comprises synthesizing silicon carbide by irradiating a high frequency electromagnetic wave of Hz or higher. 2. A carbonized material is irradiated with a high frequency electromagnetic wave having a frequency of 2 GHz or more by irradiating a mixed raw material of a carbide powder of silicon-enriched biomass and a silica powder such as quartz or a powder such as silica stone containing silica as a main component. A method for producing silicon carbide, which comprises synthesizing silicon. 3. Irradiating a mixed raw material of carbon powder such as graphite or amorphous carbon and silica powder such as quartz or powder such as silica stone containing silica as a main component with a high frequency electromagnetic wave having a frequency of 2 GHz or more. A method for producing silicon carbide, which comprises synthesizing silicon carbide by means of: 4. An apparatus for producing silicon carbide, characterized in that a raw material is surrounded by a high refractory and high heat insulating material and is irradiated with a high frequency electromagnetic wave having a frequency of 2 GHz or higher.