JPH02275725A - Production of vitreous fine granule accumulation - Google Patents

Abstract

PURPOSE:To provide the subject production process so designed that vitreous fine granules formed in the inner layer are prevented from adherence to the inner wall of the projected part by heating a combustion-supporting gas and allowing the gas to flow onto the inner wall of a double flame burner of special structure. CONSTITUTION:The central part of a burner is provided with a boat (inner layer) for synthesizing vitreous fine granules comprising a raw gas injection boat 1, combustion gas injection boats 2, combustion controlling inert gas injection boats 3 and combustion-supporting gas injection boats 4, and on the outer periphery of the inner layer, a flame-forming boat (outer layer), projected by a length L, comprising inert gas injection boats 5, fuel gas injection boats 6, combustion-controlling inert gas injection boats 7 and combustion-supporting gas injection boats 8 is formed. And just in front of the entrance of the boats 4, a flow channel 10 with a heater 9 for the gas is set. Thence, a fuel gas and an oxygen gas heated to >=150 deg.C are injected from the boats 2 and the boats 4, respectively, to form a flame on the inner wall of the outer layer, and a raw gas is then introduced into the flame to form vitreous fine granules.

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).
Alternatively, the present invention relates to a method of synthesis using a soot synthesis method such as the OVD method (external deposition method), and particularly relates to a method of manufacturing a glass fine particle deposit body suitable for an intermediate product used in an optical fiber preform that requires high quality. .

[Prior Art] One method for manufacturing a glass particle deposit is to eject a mixture of combustion gas and glass raw material gas from a combustion burner, generate granular glass through a hydrolysis reaction or oxidation reaction in a flame, and produce granular glass. is deposited on the tip of a rotating starting material to form a glass fine particle deposit, and the starting material is moved relative to the combustion burner as the deposit grows, thereby producing a glass fine particle deposit ■ΔD There is a law.

In addition, the OVD method (for example, Japanese Patent Application Laid-open No. 73522/1983) involves 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 to produce a glass particle deposit. (see official bulletin).

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 body. For example, this is published in Utility Model Publication No. 60-4797,
As shown in Japanese Patent Publication No. 62-50418, a concentric multi-tube burner is equipped with a glass particle synthesis port having at least a frit injection port, a fuel gas injection port, and a combustion supporting port in the center. one or more flame-forming ports having at least a fuel gas port and a combustion-supporting gas port protruding from the outer periphery by a length in the gas flow direction with respect to the outlet of the glass particle synthesis port. This is a trading burner.

Traditionally, the efficiency of granular glass deposition 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 part (port 1 in the figure) compared to single flame type burners.
~4) port 21 for glass particle synthesis (called inner layer,
The flame formed by this port is called the inner flame)
A flame forming port 22 consisting of a fuel gas ejection port and a combustion-supporting gas ejection port (ports 5 and -8 in the figure) is installed on the outer periphery of the inner layer by a length L with the tip of the port protruding from the inner layer. The group of ports is called the outer layer, and the flame formed is called the outer flame.The presence of this outer flame increases the overall flame size, and the entire synthesized glass particle deposit increases. Easily heated. Furthermore, the presence of the protrusion ff1L made it possible to stably lengthen the inner flame, making it possible to stably advance the reaction of the glass raw materials.

However, as shown in FIG. 3, granular glass 20 is generated by the reaction of the glass raw materials in the inner flame 1), and as it flows as a flow of glass particles 13 through the protruding portion surrounded by the outer layer, this granular glass A phenomenon can be observed in which a portion of the material 20 diffuses in the outer circumferential direction and adheres to the innermost wall 12 of the outer layer port as shown as 14 in the figure. Since the amount of granular glass deposited increases over time, the flow of the flame 1) and the glass particle flow 13 will gradually become narrower, or if the circumferential deposition I4 is uneven, the flow will be directed to the center of the burner. In some cases, the flow was asymmetrical with respect to the axis, making it impossible to obtain a steady and stable glass particle deposit. In more severe cases, the adhering granular glass I4 could clog the protrusion, causing the bar to break.

[Means and effects for solving the problems] The structure of the present invention for solving the above problems is to eject a gaseous glass raw material from a combustion burner and cause a hydrolysis reaction or an oxidation reaction in a flame. Glass fine particles are deposited on the tip of a rotating starting material or on the outer periphery of a mandrel, and the starting material or mandrel is moved in the direction of the rotation axis relative to a combustion burner in accordance with the deposition of the granular glass. In the method for manufacturing a burner, the burner is a concentric multi-tube burner, which has a glass particle synthesis port having at least a frit injection port, a fuel gas injection port, and a combustion-supporting gas injection port in the center, and the outer periphery of the burner. A multi-flame method glass in which one or more flame forming ports having at least a fuel gas injection port and a combustion-supporting gas injection port are installed in the glass by a length L in the gas injection direction beyond the glass particle synthesis port. The burner for producing fine particle deposits is characterized in that the gas flowing through the outermost layer of the port for synthesizing glass fine particles is heated to a temperature of 150° C. or higher at the outlet of the gas port.

Preferably, a structure is adopted in which a combustion-supporting gas is allowed to flow through the outermost layer of the port for synthesis of a glass particulate accumulating pot, and a greater effect can be obtained by heating the combustion-supporting gas.

The present invention will be explained along with 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 raw material gas injection port 1 is located at the center of the burner. Combustion gas injection port 2. A port for glass particle synthesis (inner layer) is composed of an inert gas injection port 3 for combustion control and a combustion-supporting gas injection port 4, and an inert gas injection port 5 protrudes from the outer periphery by a length.
．． A flame forming port (outer layer) is constituted by a fuel gas ejection port 6, an inert gas ejection port 7 for combustion control, and a combustion supporting gas ejection port 8. Immediately before the entrance of the combustion-supporting gas ejection port 4 in the inner layer, a flow path 1O having a gas heating heater 9 is installed, so that the combustion-supporting gas in the inner layer can be heated.

Glass particles are generally generated from the fuel gas injection port 2 in the same way as in the conventional method shown in Figure 3 (1)! .

A fuel gas such as 01)4 is ejected from the combustion supporting gas ejection port 4 of the can, and a flame 1) is formed in the inner wall of the outer layer. In this flame 1), 5iCel, S
Eyes (CI!s, 5iHt Cb),
Mat: When changing the refractive index, use G as a dopant raw material.
eC1h, BCEs, etc. are input. Taking Si C14 as a representative example, the raw material introduced into the flame produces 5Iot of glass particles through a hydrolysis reaction according to the following formula (1).

As described in Rijf, the glass particles form a glass particle stream 13 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 12 of the outer layer.

In this way, when the number of particles adhering to the inner wall 12 increases, an adhering particle accumulation layer 14 is formed, the flow path is narrowed, and the size of the flame and the flow direction of the particle flow 13 are subtly changed. This greatly affects the production process, making it impossible to perform stable manufacturing. In order to stably synthesize a glass particle deposit, it is necessary to perform synthesis while preventing particles from adhering to the inner wall 12.

As a result of a detailed study of the adhesion mechanism of the glass particles to the inner wall 12, the present inventors found that the glass particles were not caused by the above-mentioned diffusion to the outer periphery that occurs with the flow, but were caused by the temperature distribution of the inner flame 1). It turned out that it was to receive the power to do so. 0, 1 to Q, 57 formed in this fire iti
In a flow with a temperature gradient, fine particles of zm move from a high temperature side to a low temperature side under force (this phenomenon is generally called the thermoporesis effect).

Flames are usually formed between fuel and combustion-supporting gases, so
In flame 1), a temperature distribution is formed in which the temperature is high at the center and low at the periphery. Therefore, the glass particles generated within the flame move to the outer periphery due to the thermohoresis effect, and if this thermohoresis effect is large, they will adhere to the inner wall 12.

Therefore, the present invention prevents glass particles from adhering to the inner wall 12 of the outer layer by increasing the temperature of the outer periphery of the flame 1) by heating a gas flowing around the outer periphery, such as a combustion-supporting gas, and reducing the above → nomophoresis effect. It is.

As for the gas flowing along the protrusion (length L), the temperature near the wall surface cannot be controlled with combustion gas (
There is a problem that the quartz vibrator is easily overheated), so a combustion-supporting gas or an inert gas is preferable.

On the other hand, considering the combination of gases for the port for glass particle synthesis, the simplest and most effective method is to arrange the combustion-supporting gas port in the outermost layer.

When an inert gas is placed in the outermost layer, the cross-sectional area of the flow path of the glass particle synthesis port tends to increase, which increases the diffusion of the glass particle flow to the outer periphery, making it possible to efficiently attach the particles to the base material. becomes difficult.

Specifically, the combustion-supporting gas heating heater 9 was used to heat the gas, and as a result of sooting for 5 to 7 hours while monitoring the temperature at the combustion-supporting gas outlet, the outlet temperature was It was found that the effect of preventing adhesion to the inner wall 12 appears when the temperature exceeds 150°C. The upper limit of the outlet temperature depends on the heat resistance of the vibrator that constitutes the protruding portions of the glass particle synthesis port and the flame formation port. Usually, quartz glass is used as a material for this type of vibrator, but quartz glass becomes easily deformed when heated to 1000 to 1200°C.

Considering the heating from the flame, it is considered preferable for the -1-limit of the gas outlet temperature to be approximately 500°C in practical use.

Furthermore, the same effect can be obtained by flowing an inert gas outside the combustion-supporting gas and heating the inert gas.

〔Example〕

Comparative Example 1 A concentric multi-tube burner with 8 tubes as shown in FIG.
Using a claw tube burner with a protrusion L of 150 mm,
A glass particle deposit was synthesized. The gases include St Cg4, fuel H1, inert gas N, and raw materials from the center.
To combustion-supporting gas, inert gas △r, fuel I■2, inert gas Ar, combustion-supporting gas 0! It was played in this order. The flow rate at this time is 5iCJ's 5f/min, inner layer H*141/min, outer layer)
1,801/min, inner layer 0*30jl'/min, outer layer ots
ol/min, Ar15j2/min. Under these conditions, the inner layer combustion supporting gas is 0. was run without heating as usual, and the glass fine particle deposit was synthesized for 5 hours. As a result, glass fine particles were found to be deposited on the inner wall 12 of the burner outer layer to a thickness of about 2 mm. The attachment point was a portion 25 to 35 mm from the tip, but the attached glass fine particles could not be completely removed after the synthesis was completed. After synthesizing 10 base materials, adhered glass particles remained on the inner wall of the burner tip to a thickness of about 0.5 a+m. It was observed that the outer diameter of the base material became thicker over time in 10 base materials. In other words, it was found that the base material with 10 strands is about 5 mm thicker than the base material with 1 strand, making stable production impossible.

Example 1 With the same configuration as the burner of Comparative Example 1, using the gas heating heater 9 shown in FIG.
It was heated to 50°C.

The temperature was measured by inserting an upstream thermocouple on the burner population side (gas introduction side).

As a result, although the base material was synthesized for 5 hours in the same manner as in Comparative Example 1, no adhesion of glass fine particles was observed on the burner inner wall 12. In addition, eight pieces of 1) material were synthesized using the same method, but no adhesion of glass particles to the inner wall 12 was observed, and the outer diameter of the base material was stable with fluctuations of ±1 mm.

Furthermore, when the heating temperature of the combustion-supporting gas was set at 100°C, after 5 hours of base material synthesis, the adhesion of glass particles to the inner wall 12 was reduced compared to Comparative Example 1, but the adhesion was approximately 0.5 - was seen. Although the heating effect has appeared, it is thought that heating to 150° C. or higher is necessary to fully obtain the effect.

In the above embodiments, a case has been described in which the raw material gas and the fuel gas are ejected from completely different ports, but the effects of the present invention described above can be obtained even when they are mixed with each other and flowed.

The glass fine particle deposit synthesized according to the present invention is dehydrated to remove moisture depending on the purpose of use, and then heated to a temperature of about 1600° C. or higher in a high-temperature electric furnace to become transparent vitrified and used as a glass lot.

〔Effect of the invention〕

As explained above, the present invention heats the combustion-supporting gas on the inner wall to 150° C. or more and flows it in a double flame burner, so that the protruding portion of the glass particles formed in the inner layer 1
2, it is possible to synthesize a stable glass particle deposit, and it is possible to obtain a base material that is very suitable for the synthesis of optical fiber base materials that require high quality. .

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention, FIG. 2 is a schematic sectional view showing the configuration of an example of a multiple flame burner according to the present invention, and FIG. It is an explanatory view of how it adheres to an inner wall. ■ is the raw material gas injection port, 2.6 is the fuel gas injection port, 3, 5.7 is the inert gas injection port, 4, 8 is the combustion-supporting gas injection port, 9 is the heater for heating the combustion-supporting gas, lO 1) is the pipe, 1) is the flame formed in the inner layer, 12 is the inner wall of the protruding part, 13 is the flow of glass particles, 14 is the part where the glass particles are attached to the inner wall of the protruding part, 20 is granular glass, and 21 is for synthesizing glass particles. The port 22 is an outer flame synthesis port, and ■ represents the protrusion length.

Claims (2)

[Claims] (1) A gaseous glass raw material is ejected from a combustion burner and subjected to a hydrolysis reaction or an oxidation reaction in a flame, and the resulting granular glass is deposited on the tip of a rotating starting material or on the outer periphery of a mandrel, and the starting material is Alternatively, in a method for manufacturing a glass fine particle deposit body by moving a mandrel in the direction of a rotational axis relative to a combustion burner in accordance with the deposition of glass particles, the method comprises a concentric multi-tube burner, in which at least a glass It has a glass particle synthesis port that has a raw material injection port, a fuel gas injection port, and a combustion-supporting gas injection port, and a length L protrudes from the glass particle synthesis port in the gas injection direction on the outer periphery of the glass particle synthesis port, and at least the fuel gas injection port is provided. In a burner for producing a glass particle deposit of a multiple flame type having one or more sets of flame forming ports each having an ejection port and a combustion-supporting gas ejection port, the gas flowing through the outermost layer of the glass particle synthesis port is A method for producing a glass particle deposit, which comprises heating the gas to a temperature of 150° C. or higher at the gas port exit. (2) The method for producing a glass particulate deposit according to claim (1), wherein the gas flowing through the outermost layer of the glass particulate synthesis port is a combustion-supporting gas.