JPH02164733A - Production of glass fine particle deposited body - Google Patents

Abstract

PURPOSE:To prevent the deposition of the glass fine particles formed in an inner layer on the inner wall of a protruding outer layer by providing an inert gas injection port at a specified height between the inner and outer layers of a burner at the time of using the multiple-flame type burner to produce the glass fine particle deposited body by axial deposition in vapor phase. CONSTITUTION:A glass fine particle synthesizing port (inner layer) consisting of a raw gas injection port 2, a gaseous fuel injection port 3, and a combustion- improving gas injection port 4 is provided at the center of a concentric multiple- pipe burner. A flame forming port (outer layer) consisting of a gaseous fuel injection port 5, a combustion-improving gas injection port 6, and a combustion- controlling inert gas injection port 7 is provided around the inner layer, and allowed to protrude by the length L. An inert gas injection port 1 is provided between the inner and outer layers, and allowed to protrude by 0.4-0.8 L. The burner is used to produce the glass fine particle deposited body by axial deposition in vapor phase, external deposition, etc. By this method, the deposition of glass fine particles on the inner wall of the outer layer is prevented, and a stable glass fine particle deposited body is synthesized.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to the production of glass fine particle deposits using the VAD method (vapor deposition method).
Or, it relates to a method of synthesis using a soot synthesis method such as the OVD method (external deposition method), and in particular relates to a method of manufacturing a glass fine particle deposit body used as an intermediate product used in an optical fiber preform that requires high quality. .

[Conventional technology]

One method for producing a glass fine particle deposit is to eject a mixture of combustion gas and raw material gas from a combustion burner, generate granular glass through a hydrolysis reaction or oxidation reaction in a flame, and rotate the granular glass as a starting material. deposited on the tip,
There is a VAD method in which a glass particulate deposit is produced by forming a glass particulate deposit and moving a starting material relative to a combustion burner as the deposit grows.

In addition, the OVD method (for example, disclosed in Japanese Patent Application Laid-Open No. 73522-1983) produces a glass particle deposit by depositing granular glass produced by a combustion burner on the outer periphery of the starting material and traversing the starting material or the combustion burner one or more times. (See Publication No.).

In such a soot synthesis method, a multiple flame type burner has been proposed as a means for improving the efficiency of depositing granular glass produced by a combustion burner onto a glass fine particle deposit. The multiple flame type burner is, for example,
As shown in Japanese Patent Publication No. 0-4797 and Japanese Patent Publication No. 62-50418, a concentric multi-tube burner has at least a frit injection port, a fuel gas injection port, and a fuel gas injection port in the center.
It has a glass particulate synthesis port having each of the combustion-supporting gas ports, and has at least a fuel port on its outer periphery that protrudes by a length in the gas flow direction with respect to the outlet of the glass particulate synthesis port. This burner has one or more sets of flame-forming ports with combustion-supporting gas ports. Conventionally, the efficiency of depositing granular glass has been improved by using this multiple flame type burner.

[Problem to be solved by the invention]

As shown in Figure 2, conventional multiple flame type burners have a central glass particle synthesis port (called the inner layer, and the flame formed by this port is called the inner flame) than single flame type burners. ), one or more sets of flame forming ports consisting of a fuel gas injection port and a combustion-supporting gas injection port (a group of these ports) are provided on the outer circumference of the The outer layer has an outer layer, and the flame formed is called an outer flame), and the presence of this outer flame increases the overall flame size, making it easier to heat the entire glass particle deposit to be synthesized. Furthermore, the presence of the protrusion ff1L made it possible to stably lengthen the inner flame, making it possible to sufficiently proceed with the reaction of the glass raw materials.

However, on the other hand, in the inner flame, granular glass is generated due to the reaction of the glass raw materials, and the protruding portion I surrounded by the outer layer
7, a part of this granular glass diffuses in the outer circumferential direction and adheres to the innermost wall of the outer layer port as shown in FIG. 3. As the amount of granular glass deposits increases over time, the inner flame flow becomes progressively narrower, or in the case of non-uniform circumferential deposition, the flow becomes asymmetrical with respect to the central axis of the burner, resulting in a steady flow. In some cases, it was not possible to obtain a stable glass particle deposit. In even more serious cases, the adhering granular glass could clog the protrusion, causing damage to the burner.

[Means and operations for solving problem 1] The structure of the present invention for solving the above problem is to eject a gaseous glass raw material from a combustion burner and cause a hydrolysis reaction in a flame,
The granular glass thus produced is deposited on the tip of the rotating starting material or the outer periphery of the mandrel, and the starting material or the mandrel is moved in the direction of the rotation axis relative to the combustion burner in accordance with the deposition of the granular glass. In a method for producing a particulate deposit, a concentric multi-tube burner has a port for synthesizing glass particulates having at least a frit injection port, a fuel gas injection port, and a combustion-supporting gas injection port in the center; At least a fuel gas injection port protrudes from this outer periphery by a length ■ in the gas injection direction than the glass particle synthesis port.

In a burner for producing a nolas particulate deposit of a multiple flame type having one or more sets of flame forming ports each having a combustion-supporting gas ejection port, there is an inert space between the glass particulate synthesis port and the flame forming port. It is characterized by using the burner for producing a glass particle deposit as described above, which is provided with a gas ejection port, and the ejection port of the inert gas ejection port is provided to protrude from the glass particle synthesis port by a length of 0.4L to 0.8L. It is something.

The present invention will be described below with reference to specific examples.

FIG. 1 is a schematic diagram showing the basic configuration of the present invention, in which the combustion burner is a concentric multi-tube burner, and the burner has a glass gas injection port with a 3° source gas injection port and a combustion-supporting gas injection port 4 in the center of the burner. A port for fine particle synthesis (inner layer) is configured,
A flame forming port (outer layer) consisting of a fuel gas ejection port 5, a combustion-supporting gas ejection port 6, and a combustion control inert gas ejection port 7 is configured so as to protrude from the outer peripheral portion by a length. Further, an inert gas ejection port I is installed between the inner layer and the outer layer so as to protrude by a length of 0.4L to 0.8L.

Conventionally, glass particles are generally generated from the fuel gas injection port 3 at 82.0 as shown in FIG. Fuel gas such as CH (0□) is ejected from the combustion-supporting gas ejection port, and flame 1
0 is formed in the inner wall 8 of the outer layer. In this flame, Si CN4, Si HC&'3 are contained as raw material gases.
, Si N2 Cj'2 and other glass raw materials, and when changing the refractive index, C,6 (:
, 14. Bc13 etc. are injected. Taking Si C14 as a representative example, the raw material introduced into the flame produces glass particles Si 02 through a reaction as shown in formula (1) below.

The glass particles form a glass particle stream 9 that flows through the flame and reaches the glass particle deposit.

At this time, the glass particles spread toward the outer circumference due to diffusion, and some of them reach the inner wall 8 of the outer layer. As the number of particles adhering to the inner wall 8 increases in this way, an adhering particle accumulation layer 11 is formed, and the flow path becomes narrower. If the flow path is narrowed, the size of the flame and the flow of the particle flow will change slightly, which will greatly affect the synthesis of the glass fine particle deposit, making stable production impossible.

The adhesion of particles to the inner wall 8 is particularly noticeable when there is turbulence in the flame flow, and in such a case, the adhering particle accumulation layer grows to a large extent, which may lead to clogging of the burner outlet.

The adhesion of this glass particle is 1 for the length of the protruding part.
It often starts at a position of about /2L, and it adheres particularly in large quantities at a position 10 to 20m+n from the tip of the outer layer.

In order to stably synthesize a glass particle deposit, it is necessary to synthesize it while preventing particles from adhering to the inner wall 8. As a result of various studies, the present inventors have developed a structure shown in FIG. We arrived at a burner structure like this. That is, the inner layer (2,3
, 4) and the outer layer (5, 6, 7) with glass particles Si 0
No. 2 blow-off ports 1 are provided, and inert gas is flowed through these ports to prevent the 5iOa particles from diffusing to the wall surface.

The outlet of the inert gas ejection port 1 is preferably located at a position 0.4L to 0.8L from the internal outlet in view of the adhesion of glass particles. Further, the gas flow rate is preferably a flow rate that does not cause disturbance to the flow in the inner layer.

For example, with respect to the flow velocity of combustion-supporting gas flowing adjacently, ±2
It is preferable to set the flow rate so that the flow rate is within 0% in order to stabilize the flow.

Inert gases used in the present invention include ArHe, N2
etc. are used, but 02 is generally used as a combustion-supporting gas in the outermost layer of the inner wall.
The same effect can be obtained even if 2 is passed through, since it does not participate in the reaction.

〔Example〕

Comparative Example 1 A glass particulate deposit was synthesized using a concentric multi-tube burner, such as a multi-flame burner as shown in FIG. The structure of the burner is an 8-layer tube with 4 inner layers and 4 outer layers, starting from the center with raw material Si CN4, fuel H2, inert gas Δr, combustion supporting gas 02, inert gas Ar, fuel H2,
Inert gas Ar and combustion supporting gas 02 were flowed in this order. For the protrusions of the inner and outer layers, 150fflI11 was used. The flow rate at this time is Si CN4517 min, inner layer H
, 141/min, outer layer 1°601/min, inner layer 02301
/min, outer layer Ox 5017 min, Ar 151/min.

As a result of synthesizing the glass particle deposit at the tip of the starting material under these conditions, the outer diameter of the base material gradually becomes thicker from the start side to the end side of the soot coating (see Figure 4, 13 is the starting material, 14
(glass fine particle deposit), stable base material synthesis could not be achieved. After 5 hours of base material synthesis, the wall surface 8 of the burner was observed, and it was found that the tip of the outer layer had glass particles with a thickness of 2ffl [
It was observed that about 11 particles were attached. The adhesion extended from the outlet to 25 to 30 [nff1] on the upstream side.

Example 1 The burner has almost the same configuration as the burner of Comparative Example 1, and the inert gas injection port shown in FIG. A glass fine particle deposit was synthesized using a space () provided between the two.

This inert gas injection port is 100 mm from the inner layer outlet.
I set it to (0.67L). Ar was used as the inert gas, and the flow rate was 151/min. The flow method and flow rate of other gases were the same as in Comparative Example 1. The flow velocity of the inner layer combustion-supporting gas 02 at the outlet was 2.1 m/sec, and the flow velocity of the inert gas A was 1.9 m/sec, and the flame flow was stable. The outer diameter of the material was almost uniform from the start to the end of the soot application in the steady composite part, and the variation could be suppressed to within ±I n+m. No glass particles were observed on the burner wall surface 8 after the material synthesis.

Comparative Example 2 Almost the same configuration as Comparative Example I, with the inert gas injection port shown in Figure 1 placed between the inner layer and the outer layer, that is, between the inner layer combustion-supporting gas port and the innermost inert gas port of the outer layer. A glass fine particle deposit was synthesized using the provided burner. This inert gas blowout port was set at 40 points (0.27L) from the inner layer outlet. A as an inert gas
r, and the flow rate was varied from 151/min to 2017 min. Flow velocity: 1.9 m 7 seconds to 2.5 m
It was 7 seconds. Under these conditions, 10 to 15
Soot particles were observed throughout the city. When we investigated the thickness of the soot after 7 hours of base material synthesis, we found that it was approximately 0.
．． Five parts were thick and adhered. These soots could not be completely removed, and when 10 soots were synthesized, there was a tendency for the outer diameter of the soot to gradually increase, increasing by 31 nffl from the initial outer diameter.

From the results of the above Examples and Comparative Examples, it is clearly understood that the effect is due to providing an inert gas ejection port between the inner layer and the outer layer as in the present invention. Furthermore, it can be understood that the protruding bottle of the inert gas ejection port has an aesthetic effect within the scope of the present invention.

In the above embodiments, the raw material gas and the fuel gas are ejected from completely different ports, or even if they are mixed with each other and flowed, the effects described in detail of the present invention can be obtained. Furthermore, it is equally effective to insert an inert gas between the fuel gas and the combustion-supporting gas for combustion control, either omitted in Figures 1 and 2, or as described in the example. .

〔Effect of the invention〕

As explained above, by providing an inert gas outlet between the inner layer and the outer layer, the present invention can prevent glass particles generated in the inner layer from adhering to the inner wall 8 of the protruding portion, thereby creating a stable glass particle deposit. It is possible to obtain a base material that is very suitable for the synthesis of optical fiber base materials that require high quality.

The glass fine particle deposit synthesized according to the present invention is heated to a temperature of about 1600° C. or higher in a high-temperature electric furnace after dehydration of the contained water depending on the purpose of use, and then turned into transparent glass, which can be used as a glass rod.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the burner structure of the present invention, FIG. 2 is a schematic cross-sectional view showing the structure of a conventional multiple flame burner, and FIG.
The figure is an explanatory diagram of how glass particles generated in the inner layer of a conventional burner diffuse and adhere to the protruding part, and Figure 4 is a diagram showing the influence that the attachment of glass particles to the inner wall of the burner has on fluctuations in the outer diameter of the glass particle deposit body. . (2) is an inert gas injection port which is a feature of the present invention; 2 is a source gas injection port; 3 is a fuel gas injection port; 4 is a combustion-supporting gas injection port; 5 is a fuel gas injection port; 6 is a combustion-supporting gas Ejection port, 7 is an inert gas (for combustion control) ejection port, 8 is an inner wall of the protruding part, 9 is a glass particle flow, I
O is a flame formed in the inner layer, 11 is a glass particle attached to the inner wall 8, 12 is a glass particle generated in the inner layer, 13 is a starting material, and 14 is a glass particle deposit.

Claims (1)

[Claims] (1) A gaseous glass raw material is ejected from a combustion burner and subjected to a hydrolysis reaction in a flame, and the resulting granular glass is deposited on the tip of a rotating starting material or the outer periphery of a mandrel, and the starting material or mandrel is A method for manufacturing a glass fine particle deposit by moving relative to a combustion burner in the direction of a rotational axis according to the deposition of glass particles, the method comprising: a concentric multi-tube burner having at least a glass raw material ejection port in the center; , has a glass particle synthesis port having a fuel gas injection port and a combustion-supporting gas injection port, and has a glass particulate synthesis port on its outer periphery that protrudes by a length L in the gas injection direction beyond the glass particle synthesis port, and has at least a fuel gas injection port. In a burner for manufacturing glass particle deposits using a multiple flame method having one or more sets of flame formation ports having combustion-supporting gas injection ports, an inert gas is ejected between the glass particle synthesis port and the flame formation port. Glass particles characterized by using the burner for producing a glass particle deposit as described above, which is provided with a port, and the outlet of the inert gas injection port is provided with a length of 0.4L to 0.8L protruding from the glass particle synthesis port. Method for manufacturing a deposited body.