JPH0834623A - Production of silica glass - Google Patents

Abstract

PURPOSE:To prevent problems caused by pulsating flow, clogging of blowing tube, and bubbling, to easily control the equipment, and to decrease the cost by providing an oxyhydrogen flame burner with a ventilating passage for a silicon compd. (for doping), storing liquid silicon compds. (for doping) in the respective containers, vaporizing the compd. from the container by use of a heating medium or a heater body to supply the vapor to the ventilating passage, and supplying the silicon compd. and the doping compd. in a specified ratio to the burner. CONSTITUTION:The figure shows the vertical cross section of the producing device for a porous silica base material. Overheated steam is introduced through a heat conducting tube PIC 2 of a vaporizing container 1 which contains SiCl4. to supply SiCl4. through a gas ventilating passage 3 and flow controllers 4 and 5 to a burner 6 to form the core and to a burner 7 to form the clad. To the burner 6 SiCl4 is mixed with a second component vaporized by overheated steam from PIC 9 and introduced by TIC 19 to prepare a mixed gas of a specified partial pressure ratio and the mixture gas is supplied through a flow controller 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silica glass, and more particularly to a method for producing silica glass used for optical fiber preforms for optical communication, LSI photomask substrates and the like.

[0002]

2. Description of the Related Art Generally, silica glass is produced by using silicon tetrachloride (SiCl ₄ ) as a glass material gas and germanium tetrachloride (GeCl ₄ ) as a dopant, which is subjected to flame hydrolysis in an oxyhydrogen flame. This is carried out by forming silica fine particles and dopant fine particles, depositing these on a rotating seed rod to form a porous silica base material, and firing and vitrifying it into a transparent glass. This will be described below based on the silica glass manufacturing apparatus shown in FIG.

FIG. 2 (a) shows SiCl ₄ as a glass source gas.
Fig. 1 is a vertical cross-sectional view of an apparatus for producing a porous silica preform using a silicon compound such as SiCl ₄ , which is a metal or glass container 21 containing a silicon compound such as SiCl _4.
O ₂ gas or N ₂ gas whose flow rate is controlled by a gas flow rate controller 22 such as a mass flow controller (MFC),
Although SiCl ₄ is vaporized by bubbling by forcedly ventilating an inert gas such as Ar gas, the SiCl ₄ is constantly fed to the core forming burner 23 and the clad forming burner 24. is air also GeCl ₄ gas vaporized in the inert gas of GeCl ₄ were forced aeration in the same manner as described above as a dopant accommodated in the container 21 of the same type as the container 25 for the SiCl _4.

O ₂ gas and H ₂ gas are sent to the core forming burner 23 and the clad forming burner 24, respectively.
Since an oxyhydrogen flame is created here, SiCl ₄ and GeCl ₄ sent to these burners are made into silica fine particles, GeO ₂ fine particles 26 by flame hydrolysis in this oxyhydrogen flame, and these rotate. Fig. 2 (b)
Although it grows as the porous silica matrix 28 shown in
This method is known as the VAD method.

As described above, in the VAD method, O ₂ gas or an inert gas was used as the liquid material such as SiCl ₄ and GeCl ₄ .
It is supplied by a so-called carrier gas method vaporization method, and the vaporization rate in this method is the carrier gas velocity,
Depends on temperature and saturation, etc.
It is controlled by a carrier gas flow rate with excellent responsiveness while keeping the saturation constant. However, since this saturation degree is determined by the gas-liquid contact time when aerated in the container, there is a problem that the saturation degree is not always maintained at a constant value within the operating range of the carrier gas flow rate. A two-stage bubbler method in which one bubbler is a supersaturation tank and a second bubbler is a condensation tank (see Japanese Patent Application Laid-Open No. 4-341340), and the temperature of the vaporizer, the flow controller, the piping, etc. is kept constant without using a carrier gas. Structure consisting of gas supply equipment held (actual fairness
5-5941), a valve for controlling the flow rate and a MFC are not provided downstream of the vaporizer, one flow meter is installed for each raw material flow path, and this monitor value is fed back to the vaporization temperature controller. A method for controlling the liquid temperature (see JP-A-5-22256) is disclosed.

[0006]

However, when a liquid material is vaporized by a carrier gas, the vaporization rate by bubbling is controlled by the flow rate of the carrier gas, with the temperature and the saturation being constant values, so that each vapor line is vaporized. The vaporizer is provided in the above, and the main purpose is to avoid the harmful effect of using the carrier gas even when the carrier gas is not used, and the vaporizer is provided for each vapor line. Therefore, in this VAD method, a vaporization vessel is installed for each vapor line of the burner, but in the production of the porous silica preform for optical fiber preform, it is necessary to further diversify the refractive index distribution, It is necessary to use the VAD method that requires SiCl ₄ and a doped material at the same time. Therefore, this requires a large number of vaporizers to be arranged in the VAD method manufacturing apparatus, which complicates facility management and
The disadvantage is that the equipment is expensive.

Further, in this case, a vaporizer is installed for each vapor line, but when the liquid replenishment commensurate with the vaporization flow rate falls below the required flow rate, intermittent replenishment is performed, and the start and stop of each line is started. In addition, since the load fluctuation during the transition to the steady state is large, complete continuous replenishment becomes difficult, and fluctuations in the carburetor liquid temperature may be induced, which may cause fluctuations in steam flow. It is necessary to install a heat exchanger in the liquid line or make the carburetor volume large enough so that the liquid temperature fluctuation in the carburetor is within the allowable range over the fluctuation range of the replenisher liquid flow rate. It has the disadvantage of being complicated and costly.

For this reason, there is also a method in which the vaporizer has a sufficiently large volume so that the liquid is not replenished during the production of one unit of the base material. In this case, however, the composition of the liquid raw material is changed during the production of one unit of the base material. The problem of large changes arises,
When this liquid raw material contains high-boiling components in addition to SiCl ₄ as the main component having a low boiling point, this liquid raw material gradually becomes high in high-boiling components, and the concentration of high-boiling components in vaporized vapor also increases. As a result, the liquid component also has the disadvantage that it is necessary to renew the liquid component in its entirety.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for producing silica glass which solves these disadvantages, drawbacks and problems, in which a vaporized silicon compound and / or a vaporized doping compound is treated with an acid. Flame hydrolysis is performed in a hydrogen flame to generate silica fine particles and / or fine particles of dope material, and these fine particles are adhered to a rotating seed rod or a transparent silica glass seed rod heated above the glass melting temperature. In the method for producing a porous glass base material or a silica glass transparent body, one or more oxyhydrogen flame burners for generating silica fine particles and / or fine particles of a doped material are prepared, and the burner is used to vaporize a silicon compound and It is equipped with a single or multiple channels for venting the dope compound and / or the liquid silicon compound. And / or a liquid dope compound is provided with a container in which it is always stored for each type, and a heat transfer medium controlled at a temperature higher than the holding temperature of each liquid material or a heat conduction phenomenon due to a temperature difference with a heating element is used. Is filled with latent heat of vaporization, and each vaporized compound is supplied from each container to the single or multiple ventilation channels for each single or multiple burner via the temperature sensor and the piping element of the flow control valve. It is characterized by being done.

That is, the inventors of the present invention have conducted various studies to develop a method for producing silica glass for optical fibers for optical communication and LSI photomask substrates, and as a result, VA
In the method for producing silica glass by the method D, one or a plurality of oxyhydrogen flame burners for generating silica fine particles and / or fine particles of a dope material are prepared, and the vaporized silicon compound and / or the compound for doping is added to the burner. Is provided with one or a plurality of ventilation passages, and the liquid silicon compound and / or the liquid dope compound is stored in a container capable of storing each type, and a heated heat medium is stored in these storage containers. Alternatively, a latent heat of vaporization is applied by using a heating element to vaporize these compounds, and each vaporized compound is supplied to a single or multiple ventilation passages of the burner, whereby a silicon compound and a doping compound are planned. Since it is supplied to the burner at a fixed ratio, a silica base material with a calculated refractive index is obtained, which is of high purity. Becomes, the replacement fluid is also easily performed for each compound was consumed the manufacture of the silica glass also resulted in completion of the present invention found that given the advantage that can be continuously performed. This will be described in more detail below.

[0011]

The method for producing silica glass according to the present invention is VAD
In the method for producing silica glass according to the method, one or a plurality of oxyhydrogen flame burners provided with a single or a plurality of vaporized silicon compound and / or dope compound ventilation passages are prepared, and a liquid silicon compound and / or Alternatively, prepare a container for storing the liquid dope compound for each type, put a heating medium or heating element controlled at a high temperature in this container to vaporize these compounds, and then vaporize these vaporized compounds, and the aeration channel of the burner. To produce silica fine particles and / or dopant fine particles by flame hydrolysis of these compounds in an oxyhydrogen flame, from which silica carrier rods are manufactured. A silica base material with a refractive index can be obtained, and replacement of each consumed compound can be easily performed, so silica glass can be obtained continuously. It is possible.

The silica glass according to the present invention is produced, for example, by the apparatus shown in FIG. FIG. 1 is a vertical cross-sectional view of a porous silica preform manufacturing apparatus according to the present invention. As shown in FIG. 1 (a), this is an evaporation container 1 containing SiCl ₄ as a silicon compound. Heat Transfer Tube / PIC2
The superheated steam is introduced via the steam generator, and this SiCl ₄ is vaporized by indirect heating due to the latent heat of condensation of steam, and the SiCl ₄ gas is passed through the gas ventilation passage 3, the flow rate controllers 4, 5, and the core forming burner 6 and the clad. Air is sent to the forming burner 7.

The core forming burner 6 is contained in an evaporation vessel 8 and is vaporized by superheated steam from the PIC 9 and mixed with the second component introduced by the TIC 19 as a mixed gas having a constant partial pressure ratio to the reaction system. GeCl ₄ as a doping agent is also sent through the flow rate controller 10.
The SiCl ₄ vapor and GeCl ₄ vapor are converted into silica fine particles and GeO ₂ fine particles 11 by flame hydrolysis in the oxyhydrogen flame in the burner 6 for forming the core and the burner 7 for forming the cladding, and are deposited on the rotating target 12. As shown in FIG. 1 (b), it grows as a silica glass fine particle deposit body 13. At this time, the SiCl ₄ liquid and GeCl ₄ liquid contained in the evaporation vessels 1 and 8 are deposited.
The liquid is continuously replenished with SiCl ₄ liquid and GeCl ₄ liquid from pumps 14 and 15, and the waste liquid is continuously discarded by pumps 16 and 17.

In this case, SiCl ₄ , GeCl ₄ generated here
Vapors such as are sent to the burner through the gas ventilation flow path 3 and the flow controllers 4, 5 and 10. These piping parts, control valves, etc. are heated to a temperature at least 10 ° C higher than the compound vapor body. To prevent recondensation of the compound vapor, and the vapor phase pressure of this compound container is conducted at a pressure value at least 0.35 kg / cm ² higher than the maximum pressure value in the back pressure of the ventilation channel. It is preferable to supply the amount of heat.

Further, in the present invention, the heating medium or heating element heated to a high temperature as described above is placed in the containers 1 and 8 storing liquid compounds such as SiCl ₄ , GeCl ₄ and the like, and these heat sources and containers are used. The liquid compound is vaporized by applying this latent heat of vaporization due to the temperature difference from the liquid temperature, but this container capacity is such that when the evaporation mass velocity per unit area of the gas-liquid interface exceeds 0.5 g / cm ² , This should not exceed 0.5 g / cm ^2, as the convection in the liquid phase becomes violent and the gas phase pressure may fluctuate every few minutes. In the case where the gas phase in the container is a two-component system in which the gas body of the liquid compound is the first component and the inert gas of O ₂ or Ar or N ₂ gas is the second component, this is the inside of the container. The area A (cm ² ) of the gas phase interface is such that A ≧ 44.8√Q with respect to the flow rate Q (cm ³ / min) of the second component gas at the maximum load, and the gas phase pressure is constant. The second component gas may be supplied continuously or at an indefinite time so that the compound gas in the second component gas has a saturation level of 99% or more.

In the present invention, the liquid compound is continuously replenished from the pumps 14 and 15 as described above, but the power transportation equipment by this pump may be pressure transportation equipment by N ₂ pressurization. Pump 16 as described above,
Although the waste liquid may be discharged by means of 17, the amount of this waste liquid should be approximately 10 to 10% of the consumption flow rate, which allows concentration or non-volatility of a substance having a boiling point higher than that of the liquid compound in the liquid in the container. An advantage is given that residual concentrated particles of impurities are prevented. Further, the replenishment of the liquid to the container is controlled by setting the total flow rate of the evaporation consumption and the discharge as a set value.

[0017]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Examples 1 and 2 and Comparative Example 1 (1) Three devices for producing silica glass fine particle deposits were placed side by side, and a vaporization facility of SiCl ₄ was shared, with an inner diameter of 200 mmφ and a capacity of 10
One shared liter evaporator, hot water of 80 ℃ as a heat source, and adjusting the heating amount, vapor pressure of the evaporator is 0.5kg / cm ² , 69 ℃
Held in place and SiCl ₄ was added to 6 oxyhydrogen flame burners.
Differential pressure of 0.4kg for steam using commercial MFC for high temperature steam
While controlling the flow rate at 1 / cm ² , the flow rate is 20 for 1 line of SiCl ₄ vapor.
When g / min and 120 g / min of 6 units were supplied, the evaporation mass velocity at the gas-liquid interface in the container in this case was 0.38 g / cm ² min.

Then, silica fine particles generated by flame hydrolysis in the oxyhydrogen flame are deposited on a rotating heat-resistant carrier to prepare a porous silica base material, which is melted and vitrified to prepare silica glass. As a result of examining this physical property, no heterogeneous site such as striae was detected in this product, and the number of bubbles was 1 / kg or less.

(2) In the above method for producing a porous silica matrix, the flow rate of SiCl ₄ vapor in one line is 25 g / min, and the evaporation amount of one co-evaporator is 150 g / min.
When was producing a porous silica matrix in exactly the same conditions, the evaporation mass rate of 0.48 g / cm ² becomes in a gas-liquid interface in the vessel at this time, such as striae in the silica glass which is produced therefrom not No homogeneous part is detected, and only one bubble /
It was below kg.

(3) For comparison, in the above method for producing a porous silica base material, the flow rate of SiCl ₄ vapor in one line was 30 g / min, and the evaporation amount of one co-evaporator was 180 g / min. Other than that, when a silica glass fine particle deposit was manufactured under exactly the same conditions as above, the evaporation mass velocity at the gas-liquid interface in the container at this time was 0.57 g / cm ² minutes, and in this case the flow fluctuation of the vapor was A large amount of striae were detected in the silica glass obtained by vitrification of this porous silica preform, which was frequently generated.
It contained more than kg. (The results are summarized in Table 1.)

[0021]

[Table 1]

Examples 3, 4 and Comparative Example 2 (1) In the production of the porous silica preform, two porous silica preform producing apparatuses each having one large burner consuming SiCl ₄ vapor and one small burner were installed. The raw material vapors used for the large and small burners in these devices are shown in Table 2, and their back pressure, MFC operating pressure and vapor flow rate are also shown in Table 2. In addition, the SiCl ₄ vaporization equipment is a single co-evaporator, which uses hot water of 80 ° C as a heat source to adjust the heating amount and vapor pressure of the evaporator to 0.5 kg / cm ² , 69 ° C.
, A shared evaporator and one porous silica preform manufacturing equipment, two burners, SiCl ₄ vapor consumption line and SiCl ₄
Supplying SiCl ₄ vapor and GeCl ₄ vapor to the mixed gas consumption line of vapor and GeCl ₄ vapor, performs flow detection control operation differential pressure 0.40~0.49kg / cm ² at MFC commercial high-temperature steam, the steam line Was heated to 75-85 ° C by a heating device.

Further, the vaporizer 1 for GeCl ₄ also has a common vaporizer 1.
The temperature of the evaporator vapor phase should be maintained at 0.5 kg / cm ² and 43 ° C by adjusting the heating amount using a hot water source of 50 ° C as a heat source. At this time, if Ar gas is used as the second component gas, the vapor phase component The volume ratio is Ar: GeCl ₄ = 4.6: 1. In addition,
Both SiCl ₄ vapor and GeCl ₄ vapor have an inner diameter of 25 cmφ and a capacity of 5
Since a liter shared evaporator was used, the evaporation mass velocities at the gas-liquid interface in the container were 0.022 g / cm ² min and 0.0004 g / cm ² min, respectively.
5g / cm ² minutes, the area A of the gas-liquid interface is 490 cm ² , and the flow rate Q of the second component gas is 106 cm ³ / minute, so the calculated value is greater than 44.8√Q value 461 cm ^2. The liquid raw material, vapor phase pressure, vaporization flow rate, and gas flow rate of the second component at this time were as shown in Table 3.

SiCl ₄ vapor, G thus supplied
Silica fine particles generated by flame hydrolysis in an oxyhydrogen flame using eCl ₄ vapor, GeO ₂ fine particles are deposited on a heat-resistant carrier to form a porous silica base material, which is fused and vitrified to form silica glass. However, upon studying this, no heterogeneous site such as striae was detected in this, and the number of bubbles was 1 or less / kg.

However, for comparison, in the above apparatus, in a GeCl ₄ co-evaporator whose vapor phase pressure was kept at 0.5 kg / cm ² and 35 ° C., Ar gas as the second component gas was loaded at maximum load. , 150 cm ³ / min flow rate and the other creates a porous silica preform in exactly the same conditions as above, which was then molten vitrified to create a silica glass, this compound GeO ₂
The content concentration was less than the specified value, and the gas-liquid interface area of 490 cm ² was smaller than the calculated 44.8√Q value of 550 cm ² .

[0026]

[Table 2]

[Table 3]

[0027]

EFFECTS OF THE INVENTION According to the present invention, troubles due to pulsating flow, blockage of a blowing pipe, and harmful effects due to bubbling are avoided, and one container for liquid compounds is provided for each type of compound, so facility management and cost are low. However, since the liquid compound consumption is concentrated in only one unit, the cost does not increase even if the vaporizer is enlarged, and the liquid compound supply amount to the vaporizer becomes large, so continuous supply is realized and a continuous constant flow rate is achieved. The advantage is given that it can also be discarded.

[Brief description of drawings]

1 (a) and 1 (b) are vertical sectional views of an apparatus for producing a porous silica preform according to the present invention.

2 (a) and 2 (b) are vertical cross-sectional views of an apparatus for producing a porous silica preform by a conventional method.

[Explanation of symbols]

1, 8, 21, 25 ... Evaporation container 2, 9 ... PIC 3 ... Gas ventilation channel 4, 5, 10, 22 ... Flow controller 6, 23 ... Burner for core formation 7, 24 ... Burner for clad formation 11, 26 ... Silica fine particles, GeO ₂ fine particles 12, 27 ... Seed rod (target) 13, 28 ... Porous silica base material 14, 15, 16, 17 ... Pump 19 ... TIC

[Procedure amendment]

[Submission date] August 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The core forming burner 6 is contained in an evaporation container 8 and is vaporized by superheated steam from T IC 19 and mixed with a second component introduced by P IC 9 at a constant partial pressure ratio. GeCl ₄ as a dopant, which is sent as a gas to the reaction system, is also sent in through the flow rate controller 10. The SiCl ₄ vapor and GeCl ₄ vapor are oxyhydrogen flames in the core forming burner 6 and the clad forming burner 7. Silica fine particles and GeO ₂ fine particles 11 are deposited by flame hydrolysis in the inside and deposited on the rotating target 12, and grow as a silica glass fine particle deposit body 13 as shown in FIG. 1B. At this time, the pump 1 is used for the SiCl ₄ solution and the GeCl ₄ solution stored in the evaporation containers 1 and 8.
The SiCl ₄ liquid and the GeCl ₄ liquid are continuously replenished from Nos. ₄ and 15, and the waste liquid is continuously discarded by the pumps 16 and 17.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Further, in the present invention, SiCl ₄ , Ge
The heating medium or heating element heated to a high temperature as described above is placed in the containers 1 and 8 storing the liquid compound such as Cl _4, and the latent heat of vaporization is applied by the temperature difference between these heat sources and the liquid temperature of the container. When the evaporation mass velocity per unit area of gas-liquid interface exceeds 0.5 g / min · cm ² , the convection in the liquid phase becomes violent and the liquid compound is vaporized. Since the phase pressure may cause fluctuations in the cycle of several minutes, this is 0.5 g / min · c.
It is better not to exceed m ² . The gas phase in the container is a liquid compound gas body as the first component, and O ₂ or Ar,
In the case of using a two-component system in which an inert gas of N ₂ gas is the second component, this is because the area A (cm ² ) of the gas-phase interface in the container is the maximum of the second component gas. The second component gas may be continuously or irregularly supplied so that the phase pressure is maintained at a constant value.
The saturation of the compound gas in the component gas is maintained at 99% or more.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

In the present invention, the liquid compound is continuously replenished from the pumps 14 and 15 as described above, but the power transportation equipment by this pump may be pressure transportation equipment by N ₂ pressurization. The waste liquid may be discharged by the pumps 16 and 17 as described above, but the amount of this waste material may be about 1.0 to 10% of the consumption flow rate, and according to this, a substance having a boiling point higher than that of the liquid compound is used. Concentration in the liquid in the container or residual concentration party of non-volatile impurities
The advantage is given that curl and the like are prevented. Further, the replenishment of the liquid to the container is controlled with the total flow rate of the evaporation consumption and the discharge as a set value.

Claims (9)

[Claims] 1. A vaporized silicon compound and / or a vaporized dope compound are subjected to flame hydrolysis in an oxyhydrogen flame to generate silica fine particles and / or fine particles of a dope material, and these fine particles are rotated. In a method for producing a porous glass base material or a silica glass transparent body by adhering onto a seed rod or a silica glass transparent body heated above the glass melting temperature, a silica fine particle and / or a dope material fine particle are generated. One or a plurality of oxyhydrogen flame burners are prepared, and the burner is equipped with a single or a plurality of passages for aerating the vaporized silicon compound and / or the doping compound. And / or one container for storing liquid dope compound for each type, and holding each liquid material Heat medium controlled to a temperature higher than the temperature,
Or the latent heat of vaporization is applied by utilizing the heat conduction phenomenon due to the temperature difference with the heating element, and each compound vaporized here from each container through the temperature sensor and the piping element of the flow control valve,
A method for producing silica glass, characterized in that a single or a plurality of burners are supplied to a single or a plurality of ventilation channels. 2. The silica glass according to claim 1, wherein the re-condensation of the compound vapor is prevented by heating the piping portion and the control valve body portion in contact with the compound vapor to a temperature at least 10 ° C. higher than the vapor phase temperature of the container. Production method. 3. The amount of conduction heat so that the gas phase pressure of each compound container is maintained at a pressure value higher by at least 0.35 kg / cm ² than the maximum pressure value among the back pressures of all the ventilation channels of the compound vapor. The method for producing silica glass according to claim 1, wherein the silica glass is supplied. 4. The liquid material container according to claim 1, wherein the liquid material container is provided with a power transportation facility by a pump or a pressure transportation facility by N ₂ pressurization so that the liquid material is supplied according to the consumption amount. Method for producing silica glass. 5. The production of silica glass according to claim 1, wherein the application of latent heat of vaporization of the liquid compound prevents the vaporization mass velocity per unit area of gas-liquid interface in the container from exceeding 0.5 g / cm ² min. Method. 6. A two-component system in which a vapor phase in a container when the latent heat of vaporization of a liquid compound is applied has a liquid compound as a first component and O ₂ gas or an inert gas such as Ar or N ₂ as a second component. The method for producing silica glass according to claim 1, wherein the method is for producing silica glass. 7. The area A (cm ² ) of the gas-liquid interface in the container is A with respect to the flow rate Q (cm ³ / min) of the second component gas at the maximum load.
The structure is such that ≧ 44.8√Q, and the amount of heat from the heat medium or heating element is controlled so that the liquid phase is maintained at a constant temperature, while the gas phase pressure is maintained at a constant value. The method for producing silica glass according to claim 6, wherein the component gases are continuously or irregularly supplied. 8. The method for producing silica glass according to claim 1, wherein the compound vapor supply facility is provided with a waste liquid facility for transferring a liquid compound from a container to a waste liquid storage tank by power transfer with a pump. 9. A liquid compound container according to its consumption flow rate
By discharging liquid compounds at a flow rate of 1.0 to 10%,
A method of preventing concentration of a substance having a boiling point higher than that of a liquid compound in a liquid in a container, and replenishing the liquid to the container is controlled by setting a total flow rate of evaporation consumption and the discharge as a set value.
The method for producing silica glass according to 1.