JPH10120429A - Burner for producing fine glass particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce and deposit fine glass particles by making a specific O2 -containing gas flow to the outermost layer of a multitubular burner for producing the fine glass particles by hydrolytic reaction of a glass raw material gas in a flame therein. SOLUTION: This multitubular burner for producing fine glass particles is capable of making an O2 -containing gas which is an inert gas such as preferably N2 gas, He or Ar gas containing O2 at 15-25vol.% concentration or air flow to the outermost layer of the multitubular burner. The feed rate of the O2 -containing gas is preferably 3-60vol.% based on the glass raw material (e.g. SiCl4 gas) and the flow velocity of the O2 -containing gas is preferably 0.1-3 times that of the glass raw material gas. As a result, the diffusion and converging of a flame can be prevented and controlled and the temperature distribution in the flame in regions for producing and depositing the fine glass particles can be optimized. Thereby, the fine glass particles can efficiently be produced and deposited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner for producing glass fine particles used for producing a glass preform for optical fibers and the like.

[0002]

2. Description of the Related Art As a method for producing glass fine particles, there is a method in which a glass raw material gas is subjected to a hydrolysis reaction in a flame. In the production of glass preforms for optical fibers, as a glass raw material gas, a silicon compound such as silicon tetrachloride (SiCl ₄ ) has a dopant raw material for increasing the refractive index, such as germanium tetrachloride (GeCl ₄ ). Hydrogen gas
(H ₂ ), flammable gas such as methane gas (CH ₄ ), and oxygen gas
It is supplied into a mixed flame of an auxiliary combustion gas such as (O ₂ ) and hydrolyzed to generate glass fine particles. This may be deposited on a heat-resistant target or glass rod to form a deposit.

[0003]

However, the supply amounts of the glass raw material gas, the flammable gas, and the auxiliary combustion gas are optimal supply amounts in the case of generating glass particles and in the case of depositing glass particles on an adherend. Generally, there is a difference. In the former case, it is usually necessary to generate and deposit a raw material supply amount that is intermediate between the optimum raw material supply amounts in generation and deposition. For example, in the case of producing glass particles, the optimum gas supply amount is a combustible gas of 2 to 40 and a combustible gas of 1 to 20 with respect to the glass raw material gas 1 by volume ratio. In the case of depositing on the body, the optimum gas supply amount is the ratio of the flammable gas 2 to 40 and the auxiliary gas
1.5 to 15. In addition, conventional burners for producing glass fine particles require that the gas flow rate of the outermost layer of the multi-tube burner be controlled by the optimal gas supply amount for generating glass fine particles, regardless of the shape and the type and amount of each raw material gas supplied. Since the difference from the gas flow velocity is large, the flame spreads or converges. For this reason, when glass particles are deposited on the adherend, the deposition efficiency of the glass particles is deteriorated, and the density of the porous glass body after the deposition is reduced.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems. Deposits can be made. That is, the present invention is characterized in that an oxygen-containing gas having an oxygen concentration of 15 to 25% by volume flows through the outermost layer of a multi-tube burner that produces glass fine particles by a hydrolysis reaction of a glass raw material gas in a flame. It is.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention prevents the diffusion and convergence of a flame by flowing an oxygen-containing gas to the outermost layer of a multi-tube burner, and can control the flame freely, and regulates the supply amount. By doing so, it is possible to control the diffusion of the entire flame, optimize the temperature distribution in the flame in the generation region and the deposition region of the glass fine particles, and efficiently generate and deposit the glass fine particles.

[0006] If the oxygen concentration of the oxygen-containing gas is less than 15% by volume, the temperature of the flame is lowered, and the density of the porous glass body after deposition is reduced. Since it deviates from the range and the production efficiency and deposition efficiency of the glass fine particles decrease, it is necessary to set the range of 15 to 25% by volume. Examples of oxygen-containing gas include nitrogen gas and
An inert gas such as He gas or Ar gas containing oxygen or air is preferable. The supply amount of the oxygen-containing gas does not adversely affect the temperature distribution in the region in which the glass fine particles are generated in the flame, and a range of 3 to 60 volumes of the glass raw material gas is used because the temperature range optimal for the deposition of the glass fine particles is more secured. % Is preferable. Further, by setting the flow rate of the oxygen-containing gas to be 0.1 to 3 times the flow rate of the glass raw material gas, it is possible to prevent the diffusion and convergence of the flame.

In the present invention, even when glass particles are deposited on the adherend, the supply amounts of the glass raw material gas, the flammable gas, and the auxiliary gas may be determined so that the glass particle generation efficiency is optimal. For example, the ratio of the combustible gas 2 to 40 and the combustible gas 1 to 20 with respect to the glass raw material gas 1 may be set as the volume ratio.

The multi-tube burner may be a known one. For example, a quintuple tube having nozzles for a glass raw material gas, a combustible gas, a flammable gas, a seal gas, and an oxygen-containing gas provided in the outermost layer in this order from the center tube is used. As an example, in the present invention, 5
The present invention is not limited to a heavy pipe, and may be at least more than a five-ply pipe. In short, it is sufficient that an oxygen-containing gas nozzle is provided in the outermost layer.

[0009]

【Example】

Example 5 In order from the center nozzle of a quintuple tube burner, silicon tetrachloride gas 10SLM (gas supply rate under standard conditions, liter / min,
The same applies to the following), 150 SLM of hydrogen gas, 100 SLM of oxygen gas, and 10 SLM of argon gas are supplied to each nozzle, and 5 SLM of air is supplied to the outermost nozzle. When this flame was vertically separated from the surface of the glass plate by 30 cm on a glass plate having a thickness of 7 mm and the glass particles were deposited to a thickness of 7 mm, the deposition efficiency was 53% of the total glass particle amount, and the deposition density was 0.6%. g / cm ³ .

Comparative Example When glass fine particles were deposited under the same conditions as in the example except that air was not supplied to the outermost nozzle of the five-tube burner, the deposition efficiency was 47% of the total glass fine particle amount. The density was 0.45 g / cm ³ .

[0011]

According to the present invention, glass particles can be efficiently generated and deposited.

Claims (1)

[Claims] 1. A multi-tube burner for producing glass fine particles by a hydrolysis reaction of a glass raw material gas in a flame,
A burner for producing glass fine particles, characterized in that an oxygen-containing gas having an oxygen concentration of 15 to 25% by volume is passed through the outermost layer.