KR20040095428A - Feeding device of porous glass preform material gas - Google Patents

Abstract

PURPOSE: Provided is a device for supplying a charge gas of a porous glass preform for optical fiber, comprising no droplets, to a burner for vapor-phase synthesis of the preform, so as to prevent the change in flow of charge gas and to produce the preform in a stable manner with no extra cost. CONSTITUTION: The device for supplying a charge gas for a porous glass preform comprises a vaporizer(14) for vaporizing raw materials for the porous glass preform to be subjected to vapor-phase synthesis, wherein the vaporizer(14) is connected to a knock-out container(19) for removing droplets from the charge gas, and the knock-out container(19) is connected, in turn, to a burner(25) for forming the porous glass preform via a duct(20) for supplying the charge gas.

Description

Feeding device of porous glass base material gas {FEEDING DEVICE OF POROUS GLASS PREFORM MATERIAL GAS}

This invention relates to the apparatus which supplies raw material gas with the burner which gas-phase synthesizes the porous glass base material used as a raw material of an optical fiber.

The optical fiber is a porous glass base material obtained by vapor phase synthesis in which a raw material gas such as tetrachlorosilane or tetrachloro germanium, which is liquid at room temperature and atmospheric pressure, is hydrolyzed by an oxyhydrogen flame of a burner to deposit the formed glass fine particles. It is made from raw materials. The base material is sintered, dehydrated and transparent vitrified, stretched, and then drawn by a line to obtain an optical fiber.

The raw material liquid is vaporized by a vaporizer that is heated and boiled to become a raw material gas of a single composition, or vaporized by a vaporizer that is bubbled with argon gas or oxygen gas, which is a carrier gas, to a raw material gas having a partial pressure of equilibrium vapor pressure. After that, the gas flow rate is adjusted and supplied to the burner.

The raw material gas contains a small amount of micro droplets called mists in which bubbles boiled or bubbles bubbled out of the raw material liquid at the time of vaporization are scattered. This droplet may contain a mixture of high-boiling substances or solid impurities in the raw material liquid.

If the source gas supplied to the burner contains droplets, the resultant gas may be flow rate fluctuated as a result of droplets being attached to a precise supply path such as a mass flow controller (mass flow controller), a filter, or a pipe that adjusts the flow rate to the burner. As a result, clogging of impurities in the droplets causes the source gas to flow away, and the porous glass base material cannot be stably formed. In addition, once the supply path is obstructed, the obstruction must be replaced, which is cumbersome and costly.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus for supplying a raw material gas containing no droplets as a burner for vapor-phase synthesizing a porous base material as a raw material of an optical fiber.

1 is a skeleton configuration diagram showing an embodiment of a supply apparatus for a porous glass base material stock solution to which the present invention is applied.

Fig. 2 is a partial skeleton configuration diagram showing another embodiment of the supply apparatus of the porous glass base material stock solution to which the present invention is applied.

3 is a partial skeleton configuration diagram showing another embodiment of the supply apparatus of the porous glass base material stock solution to which the present invention is applied.

4 is a partial skeleton configuration diagram showing another embodiment of the supply apparatus of the porous glass base material stock solution to which the present invention is applied.

<Explanation of symbols for the main parts of the drawings>

11: storage container

12: raw material liquid

13: flow control valve

14: carburetor

15: space

16: raw material liquid

17: heat source

18: raw material gas sending pipe

19: knock out containers

20: raw material gas supply piping

21: heating heater

22: filter

23: mass flow controller

24: insulation heater

25: burner

26: porous glass base material

30: reflux pipe

31, 32: baffle

The vaporizing apparatus 14 of the raw material liquid 16 of the porous glass base material synthesize | combined by gas phase is demonstrated with reference to FIG. 1 corresponding to an Example, The supply apparatus of the porous glass base material raw material gas of this invention made in order to achieve said objective. ) Is connected to the delivery pipe 18 of the vaporized raw material gas, connected to the knock-out container 19 for removing the droplets in the raw material gas, and the knock-out container 19 is passed through the supply pipe 20 of the raw material gas, It is connected to the porous glass base material synthesis burner 25.

The knock-out container 19 is an empty tank, for example. When source gas flows in into this tank 19 gradually through the delivery piping 18, the droplet in source gas will settle. As a result, the source gas which hardly contained the droplet collects above the tank 19, passes through the source gas supply piping 20 in the upper part of the tank 19, and is supplied to the burner 25. FIG.

The vaporizer 14 is integrated with the knock-out container 19, and has enough space 15 so that even if the droplets scatter in the vaporizer 14, the vaporizer 14 does not reach the delivery pipe 18 located above the vaporizer 14. You may be. As a result, the raw material gas containing no droplets is supplied to the burner 25.

The mass flow rate per unit area of the source gas into the knock-out container 19 is preferably 300 kg / m 2 h or less. If there is more than this, the momentum of the raw material gas which rises in the knock-out container 19 is too strong, and a droplet will fly without settling, and it cannot remove a droplet in source gas.

In the supply apparatus of the porous glass base material raw material gas, as shown in FIG. 2, the delivery piping 18 is inserted in the knock-out container 19, and the tip part may be downward.

In the supply apparatus of the porous glass base material raw material gas, the member which prevents the spread of a droplet may be provided in the knock-out container 19. This member may be the baffle 31 which consists of a shielding plate bent downward, for example as shown in FIG. This member may be referred to as baffle 32, which is a shielded flat plate covering the delivery pipe 18 widely as shown in FIG. In addition, this member may be a demister which blows gas toward the delivery pipe 18 from above in the knock-out container 19.

It is preferable that the source gas supply piping 20 has the heaters 21 and 24 which heat above the boiling point in the pressure of a raw material liquid.

The heater may be a heating heater 21 for completely vaporizing droplets in the source gas above the boiling point in the pressure of the source liquid and a heater 24 for insulating the source gas having passed therethrough.

The heating heater 21 is preferably a double tube heat exchanger or a shell tube heat exchanger, and more preferably a double tube heat exchanger having a simple structure. It is preferable that the source gas is heated 20 degreeC or more higher than the boiling point of the source liquid under the pressure by the heater heater 21. For example, when a raw material liquid is tetrachlorosilane which has a boiling point of 80 degreeC by the pressure of 0.1 MpaG, it heats to about 100 degreeC. Even if a minute droplet which could not be removed from the knock-out container 19 remains, it is completely vaporized by the heating heater 21.

It is preferable that the thermal insulation heater 24 is an electric heater, the heater which uses a heating medium oil as a heat source, and the heater which uses steam as a heat source. By this heat retention heater 24, raw material gas is warmed to the appropriate temperature below the heating temperature of a heating heater more than the boiling point in the pressure of a raw material liquid, and is supplied to the burner 25 in the state fully vaporized without condensation. .

It is preferable that the vaporizer | carburetor 14 is a cylindrical vertical type or a cylindrical horizontal type which used the up-and-down mirror board, and it is still more preferable if it is a cylindrical vertical type which is easy to vaporize uniformly with internal pressure. On the outer wall of the vaporizer | carburetor 14, the heat source 17, such as an electric heater, steam, and a heating medium oil, is provided. The heat source 17 of the vaporizer | carburetor 14 may be a steam reflux tube and an electric heater which are injected into the raw material liquid 16 and directly heat the raw material liquid 16.

The vaporizer 14 may be heated while bubbling an inert gas.

By using this porous glass base material feed gas supply device, the raw material gas containing no droplets can be stably supplied to the burner 25.

Hereinafter, the Example of the supply apparatus of the porous glass base material raw material gas to which this invention is applied is explained in full detail.

1 is a skeleton configuration diagram of a device for supplying a porous glass base material gas.

In this apparatus, the vaporizer 14 connected to the raw material liquid storage container 11 is connected to the knock-out container 19 via the raw material gas delivery pipe 18, and the knock-out container 19 is connected to the raw material gas supply pipe ( It is connected to the burner 25 via 20).

The nitrogen gas source is connected to the upper part of the storage container 11. The storage container 11 is filled with a porous glass base material stock 12 such as tetrachlorosilane, tetrachlorogermanium, or halogenated alkylsilane. From the lower part of this storage container 11, the supply pipe which has the flow regulating valve 13 is extended, and is inserted in the vicinity of the bottom of the vaporizer | carburetor 14.

The vaporizer | carburetor 14 is a cylindrical longitudinal type, the electric heater which is the heat source 17 surrounds the outer wall, and the porous glass base material raw material 16 is filled. The raw material gas sending pipe 18 extends from the upper part of the vaporizer | carburetor 14, and is connected to the intermediate degree of the main-body part of the knock-out container 19 which is an empty tank.

The delivery pipe 18 is preferably inserted into the knock-out container 19. In addition, as shown in FIG. 2, the discharging pipe 18 may be vertically downward. As shown in Fig. 3, a baffle 31 which is a shielding plate which protrudes from the inner wall higher than the delivery pipe 18 and is bent downward in the knock-out container 19 to block the tip end of the delivery pipe 18 may be provided. . As shown in Fig. 4, a shielding plate which protrudes horizontally from the inner wall of the knock-out container 19 and is installed higher than the delivery pipe 18, and covers at least half of the body of the container 19 while covering the delivery pipe 18. Phosphorus baffle 32 may be provided. It may be a demister that blows gas upwards above the knock-out container 19. Combining them further reduces the diffusion of the droplets.

From the lower part of the knock-out container 19, the reflux tube 30 which has an opening-closing valve and a check valve is extended and inserted in the vaporizer | carburetor 14 as needed.

From the upper part of the knock-out container 19, the source gas supply piping 20 which has the heating heater 21 which is a double tube type heat exchanger is extended. The raw material gas supply piping 20 is branched in front of it, the filter 22 and the mass flow controller 23 are provided in each, and the heat insulation heater 24 which is an electric heater is provided in the periphery. The mass flow controller 23 is connected to the burner 25. The burner 25 is connected to a hydrogen gas source and an oxygen gas source.

This porous glass base material supply device operates as follows.

Nitrogen gas is introduced into the storage container 11. The flow rate control valve 13 is opened or closed, and the raw material liquid 12 of the storage container 11 is replenished at any time so that the vaporizer 14 is always sufficiently filled with the raw material liquid 16.

In the electric heater 17 of the vaporizer | carburetor 14, the raw material liquid 16 in the vaporizer | carburetor 14 is heated and boiled. The raw material liquid 16 becomes a raw material gas containing the micro droplets which splashed and scattered from the liquid surface at the time of boiling.

This source gas flows gently from the vaporizer | carburetor 14 to the source gas delivery piping 18, and to the knock-out container 19. FIG. The droplets contained in the source gas are settled in the knock-out container 19 for their own weight, aggregate, and eventually form a liquid and are stored at the bottom in the knock-out container 19. When the aggregate liquid accumulates to some extent, the open / close valve is opened to pass through the reflux tube 30 and return to the vaporizer 14. Moreover, you may always open this open / close valve.

On the other hand, the raw material gas in which the very small droplets remain slightly above the knock-out container 19 is stored. This raw material gas flows from the knock-out container 19 to the raw material gas supply pipe 20, and is heated in the heating heater 21 above the boiling point in the pressure of the raw material liquid and completely vaporized.

The completely vaporized raw material gas flows branched, is heated by the warm heater 24, passes through the filter 22, the flow rate is adjusted to the mass flow controller 23, and is supplied to the burner 25.

The raw gas is hydrolyzed by the oxyhydrogen flame of the burner 25. The glass fine particles thus produced are deposited to form a porous glass base material 26.

The example which manufactured the porous glass base material using the supply apparatus of a porous glass base material raw material according to the said Example is shown to the following 1st Example and 2nd Example.

<First Embodiment>

Tetrachlorosilane was used as the porous glass base material stock solution 16. The operating pressure of the vaporizer | carburetor 14 was 0.1 MpaG. As the knock-out container 19, a raw material gas having a cross-sectional area of 0.95 m 2 at a diameter of 1100 mm was used, and the raw material gas flowing there from the raw material gas supply pipe 20 was heated to 110 deg. C by the heating heater 21, and the heating heater 21 The raw material gas supply pipe from the filter 22 and the mass flow controller 23 to the burner 25 was warmed to 100 ° C. by the thermal insulation heater 24. The source gas was supplied to 16 burners 25 capable of batch operation. Since the mass flow rate of the source gas flowing from the vaporizer 14 to the knock-out container 19 with the fluctuation | variation of the number of the burners 25 which are batch operation | movement was 150-250 kg / h, into the knock-out container 19 The mass flow rate per unit area varied from 158 to 263 kg / m 2 h.

The feeder continued to operate for six months, but the feeder was not blocked anywhere. In the meantime, the supply amount of source gas to the burner 25 was stable, and the porous glass base material 26 was able to be formed continuously.

Second Embodiment

Tetrachlorosilane was used as the porous glass base material stock solution 16. The operating pressure of the vaporizer | carburetor 14 was 0.05 MpaG. As the knock-out container 19, a raw material gas having a cross-sectional area of 0.50 m 2 at a diameter of 800 mm is used, and the raw material gas flowing there from the raw material gas supply pipe 20 does not use a heating heater, but the raw material gas up to the burner 25 is used. The supply piping was warmed to 100 ° C. in the warming heater 24. The source gas was supplied to 18 burners 25 capable of batch operation. Since the mass flow rate of the source gas which flows from the vaporizer 14 to the knock-out container 19 with the fluctuation | variation of the number of the burners 25 which are batch-operating is 20-40 kg / h, the mass flow rate per unit area is 40- It changed to 80 kg / m <2> h.

The feeder continued to operate for six months, but the feeder was not blocked anywhere. In the meantime, the supply amount of the source gas to the burner 25 was stable, and the porous glass base material 26 could be continuously formed.

As described above, when the porous base material gas supply device of the present invention is used as described in detail, it is possible to stably supply the source gas completely vaporized without the droplets to the burner.

Even if the raw material liquid is severely vaporized by the vaporizer and a large amount of liquid droplets are contained in the raw material gas, the droplets can be reliably removed until it is supplied to the burner, thereby increasing the vaporization efficiency. In addition, since it is not necessary to vaporize gradually, the vaporizer can be miniaturized.

In addition, since the source gas containing no droplets can be supplied to the burner, the porous glass base material formed by vapor phase synthesis using the vapor phase deposition method (VAD method) or the external deposition method (OVD method) using the same is homogeneous and has excellent quality.

Claims (6)

The vaporizer of the raw material liquid of the porous glass base material synthesized in the gas phase is connected to a knock-out container for removing droplets in the source gas via a delivery pipe of vaporized source gas, and the knock-out container passes through a supply pipe of source gas. A porous glass base material feed device, which is connected to a porous glass base material synthesis burner. The mass flow rate per unit area of the said source gas into the said knockout container is 300 kg / m <2> h or less, The supply apparatus of the porous glass base material raw material gas of Claim 1 characterized by the above-mentioned. The porous glass base material supply device according to claim 1 or 2, wherein the delivery pipe is inserted into the knock-out container, and the tip thereof is downward. The apparatus for supplying a porous glass base material gas according to claim 1 or 2, wherein a member for preventing diffusion of the droplets is provided in the knock-out container. The porous glass base material feed gas supply device according to claim 1 or 2, wherein the raw material gas supply pipe has a heater that heats above a boiling point in the pressure of the raw material liquid. The porous glass base material according to claim 5, wherein the heater is a heating heater for completely vaporizing droplets in the raw material gas above a boiling point in the pressure of the raw material liquid and a heater for insulating the raw material gas having passed therethrough. Supply of raw gas.