JPS599495B2 - Silica glass manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine powdered synthetic quartz glass (including doped quartz glass) using a fluidized bed formed by quartz particles.

It is well known that quartz glass with good homogeneity can be obtained by melting finely powdered quartz glass.

Synthetic silica glass is currently manufactured by oxidizing or flame hydrolyzing Si chloride or hydride.

Specifically, known methods include hydrolysis in a flame such as an oxyhydrogen flame, a high frequency plasma torch method, and a CVD method.

Although each of these has excellent characteristics, the resulting glass tends to contain OH groups, the control of the heat source is complicated, and
It also has problems such as slow reaction speed.

The present invention provides a method for efficiently obtaining a large amount of synthetic quartz glass using a heat source that is relatively easy to control.Quartz particles are placed in a heated reaction vessel 1, and an oxidizing gas (described later) is introduced from below. ) is fed to form a fluidized bed of the particles, and a reactive gas (also see below) is fed into this fluidized bed to produce fine powdered quartz glass.

Next, this will be explained in more detail.

First, to outline the apparatus used, in the drawing, reference numeral 1 denotes a closed, cylindrical reaction vessel, for example, made of quartz or the like.

An oxidizing gas introduction pipe 2 is connected to the bottom thereof, and a discharge pipe 3 is attached to the top thereof to lead out the generated quartz glass fine powder and reaction waste gas.

Reference numeral 4 denotes a porous rectifying plate made of, for example, sintered quartz, for forming a fluidized bed.

Reference numeral 5 denotes a reaction gas introduction tube, which airtightly penetrates the wall surface of the reaction vessel 1 and branches into many parts inside, and each tip penetrates the perforated plate 4 and opens onto it.

6 is a heat source such as an electric furnace, 7 is a cyclone separator, 8 is a reaction waste gas outlet, and 9 is a hopper.

Particles used to form a fluidized bed are fine as long as they do not react at all with the oxidizing gas and the reaction gas for glass formation, but if they are mixed into the formed quartz glass, they will not become impurities. For this purpose, particles of high-purity quartz (including synthetic quartz, crystal, synthetic crystal, etc.) are used.

The appropriate size is 20 to 200 pm < leprosy.

As the oxidizing gas sent from the oxidizing gas introduction pipe 2, pure 02, NO, CO, etc. are used.

The reaction gas fed from the reaction gas inlet tube 5 for glass formation is mainly SiCl4, which generates SiO2 through oxidation, but it is also oxidized in the same way as was done in the production of conventional synthetic quartz glass. So A103 + B2
03) Source gases serving as dopants such as Ti02, Alcl3, BBr3, Ticl4, etc. are also added as necessary.

In this specification, the term "reactive gas" is used to refer to gases that include these dopant gases.

The 02 introduced from the introduction pipe 2 is ejected upward from the many small holes in the current plate 4.

If the relationship between the speed of this ejected zero and the size of the particles placed above it is appropriate, the particles as a whole will be in a state similar to that of boiling liquid, that is, a state of fluidization.

10 shows the resulting fluidized bed. On the other hand, heat is applied from the heat source 6.

The inside of the fluidized bed 10 is heated almost uniformly.

Into such a state, a reaction gas for glass formation is fed from the introduction tube 5.

Then, the reaction progresses rapidly and fine powdered quartz glass is produced.

Since these particles are very small compared to the particles forming the fluidized bed 10, they are blown upward together with the reaction waste gas, and are led to the cyclone 7 through the conduit 3.

Here, the reaction waste gas is separated and discharged from the outlet 8, and the quartz fine powder falls from the cyclone 7 and is collected in the hopper 9.

Note that the method of obtaining synthetic quartz glass by flame hydrolysis of a silicon compound is not used in the present invention because the product contains OH groups.

Next, examples will be shown.

The reaction vessel 1 was made of quartz and had a diameter of 150 mm and a height of 200 mm.

Crystal powder of 20 to 200 μm is used as particles for forming a fluidized bed, and 02 is fed from the introduction tube 2 at a rate of 150 ll to form a fluidized bed 10 of the particles. was heated to 1000°C.

Here, 15% of Sicl4 contained in 20l/min.
By feeding at a rate of l/min and reacting for 1 hour, SiO
1.8 kg of fine powder of No. 2 was obtained.

Because it was so fine, it could be continuously sintered into a transparent glass body.

The effects of the present invention are as follows.

(1) Since a fluidized bed is formed and the reaction is carried out in this bed, heating from the surroundings is carried out efficiently and the reaction is carried out uniformly and efficiently.

(2) The entire process can be carried out in a sealed container, so
High purity quartz glass fine powder can be obtained.

[Brief explanation of drawings]

The drawing is a schematic illustration of the apparatus used to carry out the method of the invention. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Oxidizing gas introduction tube, 5... Reaction gas for glass formation, 6...
...Heat source, 10...Fluidized bed.

Claims (1)

[Claims] 1 Put quartz particles into a reaction vessel 1 heated from the outside,
A method for producing quartz glass, which comprises feeding an oxidizing gas from below to form a fluidized bed 10 of the quartz particles, and feeding a reaction gas for glass formation into the fluidized bed 10.