JPS5939737A - Production of glass base material for optical fiber - Google Patents

Abstract

PURPOSE:To remove non-deposited pulverized glass particles in waste gas stably for a long period of time and to improve the production efficiency of a glass base material by heating the waste gas produced after reaction of a glass raw material under heating, and removing said particles at a prescribed temp. CONSTITUTION:Pulverized glass particles are formed by the combustion of the gaseous raw material ejected from a burner 2 in a protective vessel 1, and are built up on a support rod 4. The hydrogen chloride and excess steam generated in the reaction for forming the pulverized glass particles and further the non- deposited pulverized glass particles are conducted through a ventilation pipe 7 to a removing device 14. The waste gas in the device 14 collides against a baffle plate 15, and the non-deposited pulverized glass particles stick to the plate 15 and are thus removed. Since the waste gas is held at the dew point temp. of the steam and hydrogen chloride or above by a heater wire 17, no condensation arises. Therefore, the deposition of the sludge, etc. in the device 14 are surely prevented and the waste gas is discharged stably for a long period of time. The waste gas conducted to a scrubbing column 9 through the pipe 8 is neutralized and is then discharged to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method that improves the manufacturing efficiency of a glass base material by stably removing non-deposited glass particles in exhaust gas over a long period of time.

As a method for manufacturing a glass base material for a fiber, there are known manufacturing methods that utilize a gas phase reaction, such as an internal attachment method, an external attachment method, and a vapor phase attachment method. These manufacturing methods involve, for example, ejecting a gaseous glass raw material from an oxyhydrogen flame burner and subjecting it to flame hydrolysis, and depositing the resulting glass fine particles in a rod shape to produce a porous optical fiber base material within a protective container. This is the way to do it. In this method, the following reaction occurs inside the protective container. That is, 5iC4'fr as a raw material gas
When used, water vapor (I(20) and hydrogen chloride gas (HCl) and 2H2+Ot → 2LO(11 stcz4+21hO−+5i02+4HC6(2)S
iOt microparticles are produced. Here, in the normal case -1 (
The amount of each gas to be supplied is set so that the amount of HO (produced in the reaction 1) sufficiently exceeds the total amount of H2O required in the reaction 2). Therefore, the exhaust gas discharged from the inside of the sleep aid device contains water vapor (Hg
o), contains a large amount of hydrogen chloride (HCl).

On the other hand, the sio fine particles produced by the reaction (2) are
Normally, 50 to 90 parts of the glass are deposited in a columnar shape to form a porous glass matrix, but the rest is not deposited and is discharged to the inner surface of the protective container. Although some glass particles remain attached to the inner surface of the protective container, their proportion is small.

As a result of the above, when the water vapor and hydrogen chloride contained in the exhaust gas are cooled and condensed in the exhaust pipe, becoming an aqueous solution of hydrochloric acid and staying or adhering to the exhaust pipe, glass fine particles contained in the same exhaust gas There is a risk that this will mix with this and turn into sludge-like deposits, gradually clogging the exhaust pipe.

To avoid this blockage phenomenon, do as follows. fJ
Methods r and - prevent water vapor or hydrogen chloride in the exhaust gas from condensing by insulating or heating the exhaust pipe over its entire length.

The second method is to remove glass particles in the exhaust gas before the water vapor or hydrogen chloride gas in the exhaust gas condenses, thereby preventing blockage.

The present invention is based on the second method described above, and provides a method for producing f'J material for B0 fiber that is stable for a long period of time by further increasing the removal efficiency. When gaseous glass raw materials are heated and reacted to produce glass fine particles, and the glass fine particles are deposited to produce a porous lath, non-deposited glass is contained in the waste gas discharged from the protective container. The manufacturing method for removing all of the glass particles is characterized in that the antagonistic gas is heated to remove the non-deposited glass particles at a predetermined temperature.

The present invention will be explained in detail below along with examples.

FIG. 1 shows an outline of the manufacturing method according to the present invention.

A burner 2 and a support rod 4 protrude inside the preservation container 1.
Glass particles generated by the flame hydrolysis force f of the burner 2 are deposited on the support rod 4 to form a porous glass base material 3. The support rod 4 is gripped and rotated by the chuck 5, and is pulled upward as the glass particles are rapidly deposited. On the other hand, a supply pipe 6 for inert gas etc. and an exhaust pipe 7 for guiding exhaust gas are connected to the protective container 1, and a removal device 14 for removing non-deposited glass particles is interposed in the exhaust pipe 7. A cleaning tower 9 is connected to the device 14 through an exhaust pipe 8.
connects. A liquid tank 10 is provided at the bottom of the cleaning tower 9, while a spray shower 11 is installed at the top of the cleaning tower 9. A pump 12 for pumping caustic soda used as a neutralizing liquid to the shower 11 is provided in the liquid tank IO, and an exhaust fan 13 is provided on the side of the shower 11.

In the above manufacturing apparatus example, a baffle plate type is generally used as a device for removing non-deposited glass particles because it is simple and widely used. That is, a large number of baffle plates 15 are installed inside the device 14. In order to improve the removal effect, the number of bends in the exhaust gas flow inside the device may be increased, and the number of collisions with the baffle plate 15 may be increased. The residence time of the exhaust gas becomes longer, and the contact area between the inner wall surface of the device or the baffle plate 15 and the exhaust gas is large, and the temperature of the exhaust gas decreases inside the device2)
This results in condensation of water vapor and hydrogen chloride.

Therefore, in the present invention, the removing device 14 is provided with a rear section for heating and keeping the inside of the removing device 14 warm. That is, the heater wire 17 is built inside the cover 16 of the removing device 14.

The heater wire 17 is connected 11 to an external power source 18.

In the above configuration, glass particles are generated by combustion of the raw material gas ejected from the burner 2 on the inner surface of the protective container, and are deposited on the support rod 4. Hydrogen chloride and excess water vapor generated in the glass particle production reaction, as well as non-deposited glass particles, are led to the removal device 14 through the exhaust pipe 7 as exhaust gas. In the removal device 14, the exhaust gas collides with a baffle plate 15, and non-deposited glass particles adhere to this baffle plate 15 and are removed.

In this case, the exhaust gas is kept warm by the heater wire 17 to a temperature higher than the dew point temperature of water vapor and hydrogen chloride, so that no condensation occurs.

Therefore, the accumulation of sludge inside the removing device 414 is reliably prevented, and the exhaust gas is stably discharged for a long period of time.

The exhaust gas led to the cleaning tower 9 through the exhaust pipe 8 is neutralized and discharged to the outside. As described above, according to the manufacturing method of the present invention, when non-deposited glass particles are removed from the exhaust gas, clogging of the exhaust gas flow path is reliably prevented, so that the glass base material can be manufactured stably for a long period of time, and Reliability can be improved.

Next, examples of the present invention will be shown.

When glass preform was manufactured under the manufacturing conditions and removal equipment conditions shown in Table 11γ, the pressure loss inside the equipment was 37wnA@'''C in the case of the present invention, which was not so large compared to the pressure loss before operation. In contrast, in the case of the conventional method, 9
A significant pressure drop of up to 0 mmAH occurred.

From the above, it can be seen that the manufacturing method of the present invention reliably prevents clogging of the exhaust pipe.

Table 1 Manufacturing conditions (a) Meteor glass raw material 5iC4300ω/Tough G
eCt4 20 tt (b) Acid water accumulation gas flow garden 02 6 t/”■t2.
8〃 (c) Surplus air volume 50 t,/mnTable 2
Removal equipment conditions Heating temperature 72℃ Heater container i #uv shape Gas passage part diameter 250 questions (Note) The condensation temperatures LL of chloride scale and water vapor in the above production case are 68℃ and 40℃, respectively.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a device 414 according to the present invention.
・Protective container, 2... Burner, 3... Porous glass base material, 4... Support rod, 5... Chuck, 6... Supply pipe, 7.8... Exhaust pipe, 9 Mountain cleaning tower, 14o...liquid tank, 11...shower, 12...pump, 13.・
...Fan, 14...Removal device, 15...Baffle plate,
16...Cover, 17...Heater wire, 18...Power source. Agent for patent applicant Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] (1) When producing a porous glass base material by heating and reacting gaseous glass raw materials in a protective container and depositing the glass particles, in the exhaust gas discharged from the protective container. A method for producing a glass base material for an optical fiber, characterized in that the non-deposited glass particles contained in the glass preform are removed by heating the exhaust gas and removing the non-deposited glass particles at a predetermined temperature. (21) A method for manufacturing a glass preform for a former fiber, as set forth in claim 1, characterized in that the heating temperature of the exhaust gas is set to be higher than the dew point of hydrogen chloride gas or water vapor contained in the exhaust gas.