KR20160028374A - Melting method, and production method for alkali-free glass plate - Google Patents

Abstract

The present invention provides a dissolution method capable of efficiently heating a molten glass through a bubble layer and suppressing the volatilization of B ₂ O _{3 in} the molten glass. A first chamber, a first chamber, a molten glass formed by melting the raw material, a second chamber supplied with the first chamber, a second chamber burner, Wherein the SiO ₂ content is 54 to 73% by mass, the B ₂ O ₃ content is 0.1 to 12% by mass, and the SiO ₂ content is 54 to 73% by mass, the B ₂ O ₃ content is 0.1 to 12% by mass, Wherein one of the oxygen burner and the air combustion burner is used as the raw material burner and each of the second raw burner, and the total combustion heat amount per one hour of the first raw burner is 50 To 100% is generated by the oxygen combustion burner, and 75 to 100% of the total combustion heat amount per hour of all the second room burners is generated by the air combustion burner do.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing an alkali-free glass plate,

The present invention relates to a dissolution method and a method for producing an alkali-free glass plate.

The melting furnace melts raw materials of alkali-free glass. The melting furnace includes a first chamber into which a raw material is injected, a first chamber burner which forms a flame in an upper space of the first chamber, a second chamber through which the molten glass obtained by melting the raw material is supplied from the first chamber, A second chamber burner for forming a flame in the upper space, and a throat connecting the lower portion of the first chamber and the lower portion of the second chamber.

The first chamber burner or the second chamber burner forms a flame by mixing fuel such as natural gas or heavy oil with gas and burning it. The burner which mainly uses air as gas is called an air combustion burner, and the burner which mainly uses oxygen as gas is called an oxygen combustion burner.

In the case of an air combustion burner, nitrogen gas, which occupies most of the air, is exhausted outside the melting furnace without contributing to combustion. On the other hand, in the case of the oxygen combustion burner, since the exhaust amount is smaller than that of the air combustion burner, the thermal efficiency is high, and the CO ₂ emission amount and the NO _x emission amount are small.

A burner using a mixed gas in which air and oxygen gas are mixed can be used (see, for example, Patent Document 1). In this case, in the case of the oxygen it fired burner is, of course, there is a case where in comparison with the case of air fired burners, the NO _x emissions increased (for example, see Non-Patent Document 1). Specifically, the oxygen concentration in the gas mixture is less than 93% by volume and in case of more than 25% by volume, compared to the case of the air fired burners, the NO _x emission is increased.

Japanese Patent Application Laid-Open No. 2000-128549

R & D Kobe Seiko, Vol. 51, No. 2 (Sep.2001), pp. 8 to 12, "Energy Saving by Oxygen Enriched Air and Low NOx Combustion"

In the case of alkali-free glass, the melting temperature of the raw material is higher than in the case of ordinary soda lime glass, and a bubble layer easily attaches to the liquid surface of the molten glass in the first chamber. The bubble layer is a collection of small bubbles, and the bubbles are caused by the generation of gas by pyrolysis of the raw material. The bubble layer is particularly likely to be formed when the SiO ₂ content of the alkali-free glass is 54 to 73 mass%.

If the bubble layer is present, the surface of the molten glass is less likely to be directly exposed to the atmosphere of the upper space. Therefore, heat radiation from the flame of the burner to the molten glass is cut off, and the heating efficiency of the molten glass is low.

In the case of a glass containing a general alkali component, B ₂ O ₃ in the molten glass tends to volatilize as the content of alkali in the molten glass increases. B ₂ O ₃ is volatilized, for example, as a sodium compound.

On the other hand, in the case of alkali-free glass containing almost no alkali component such as Na in the molten glass, B ₂ O ₃ in the molten glass tends to volatilize as the moisture concentration in the atmosphere of the upper space becomes higher.

The amount of moisture in the atmosphere of the upper space depends on the type of the burner. In the case of the oxygen combustion burner, the concentration of moisture contained in the gas after combustion is higher than in the case of the air combustion burner, and B ₂ O ₃ in the molten glass is liable to volatilize. B ₂ O ₃ is considered to be volatilized as a hydrogen compound.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a dissolution method and the like capable of efficiently heating a molten glass through a bubble layer and suppressing volatilization of B ₂ O _{3 in} the molten glass, The purpose.

In order to solve the above problems, according to one aspect of the present invention,

A first chamber into which a glass raw material is introduced,

A first chamber burner for forming a flame in an upper space of the first chamber,

A second chamber in which molten glass obtained by melting the raw material is supplied from the first chamber,

A second yarn burner for forming a flame in an upper space of the second yarn,

And a throat for connecting a lower portion of the first chamber and a lower portion of the second chamber, the method comprising:

The raw material is a raw material for alkali-free glass having an SiO ₂ content of 54 to 73 mass% and a B ₂ O ₃ content of 0.1 to 12 mass%

Wherein either one of the oxygen combustion burner and the air combustion burner is used for each of the first room burner and each second room burner,

50 to 100% of the total combustion heat amount per hour of all the first filament burners is generated by the oxygen burner,

Characterized in that 75 to 100% of the total combustion heat amount per hour of all the second room burners is generated by the air combustion burner.

According to one aspect of the present invention, there is provided a dissolution method capable of efficiently heating a molten glass through a bubble layer and suppressing volatilization of B ₂ O _{3 in} the molten glass.

1 is a flow chart showing a method for producing an alkali-free glass plate according to an embodiment of the present invention;
Fig. 2 is a sectional view showing a melting furnace used in the melting process of Fig. 1; Fig.
3 is a cross-sectional view showing a melting furnace according to a first modification;
4 is a sectional view showing a melting furnace according to a second modification;
5 is a sectional view showing a melting furnace according to a third modification;

Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and a description thereof will be omitted. In the present specification, " to " representing a numerical range means a range including numerical values before and after the numerical range.

1 is a flow chart showing a method for producing an alkali-free glass plate according to an embodiment of the present invention. The method for producing a non-alkali glass sheet has a dissolution step S12 and a molding step S14.

The alkali-free glass is a glass substantially containing no alkali metal oxide such as Na ₂ O, K ₂ O, Li ₂ O, or the like. In the alkali-free glass according to the present invention, the sum of the content of the alkali metal oxide is 0.2 mass% or less.

Alkali-free glasses can be used, for example, as mass percentage percentages based on oxides,

SiO ₂ : 54 to 73%

Al ₂ O ₃ : 10 to 23%

B ₂ O ₃ : 0.1 to 12%

MgO: 0 to 12%

CaO: 0 to 15%

SrO: 0 to 16%

BaO: 0 to 15%

MgO + CaO + SrO + BaO: 8 to 26%

Lt; / RTI >

The content of B ₂ O _{3 in the} alkali-free glass is preferably 9% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, particularly preferably 2% by mass or less % Or less.

The B ₂ O ₃ content of the alkali-free glass is preferably not less than 0.3% by mass, more preferably not less than 0.5% by mass, further preferably not less than 1% by mass, in the case of obtaining high solubility.

The distortion point of the alkali-free glass is preferably 650 占 폚 or higher, more preferably 670 占 폚 or higher, and still more preferably 700 占 폚 or higher.

The T ₂ of the alkali-free glass (the temperature which is the target of dissolution and the temperature corresponding to the viscosity of 10 ² dPa · s) is 100 ° C or more higher than the T ₂ of ordinary soda lime glass. The T ₂ of the alkali-free glass is preferably 1600 to 1820 ° C, more preferably 1610 to 1770 ° C, and still more preferably 1620 to 1720 ° C.

Β-OH showing a water content in the alkali-free glass plate is preferably 0.2 to 0.4㎜ ^-1, more preferably 0.2 to 0.35㎜ ^{- 1.} The higher the value of β-OH, the greater the water content. This value increases when dissolved in an atmosphere having a high water concentration. The value B of? -OH is calculated by measuring the plate thickness C and the transmittance T of the alkali-free glass plate and substituting the measurement result into the following equation. A general Fourier transform infrared spectrophotometer (FT-IR) is used to measure the transmittance of the alkali-free glass plate.

B = (1 / C) log ₁₀ (T1 / T2)

T1: transmittance of an alkali-free glass plate at a reference wave number 4000 / cm (unit:%)

T2: Minimum transmittance of an alkali-free glass plate in the vicinity of a water absorption wavelength of 3570 / cm (unit:%)

The alkali-free glass plate is used as a substrate for a display such as a liquid crystal display, a substrate for a magnetic disk, and the like. The use of the alkali-free glass plate may be various. According to the present embodiment, a homogeneous alkali-free glass sheet having few defects such as bubbles can be obtained, which is particularly suitable for substrates for liquid crystal displays which require high quality.

In the melting step S12 shown in Fig. 1, a raw material of alkali-free glass is charged into a melting furnace, and the raw material is melted to obtain a molten glass.

In the molding step S14 shown in Fig. 1, the molten glass is formed into a plate. The molding method may be a general method, and examples thereof include a float method and a fusion method.

The float process is a process of continuously feeding molten glass onto a molten metal (for example, molten tin) and forming molten glass into a plate shape by causing the molten glass to flow in a horizontal direction on the molten metal.

The fusion method is also called an overflow downdraw method in which the molten glass flowing over the left and right sides from the trough is caused to flow down along both the left and right sides of the trough and the molten glass merged at the lower end of the trough is further flowed downward, .

Further, a clarifying apparatus (for example, a vacuum degassing apparatus) or a stirring apparatus (for example, a stirring stirrer) may be provided between the dissolving step S12 and the molding step S14.

Fig. 2 is a sectional view showing a melting furnace used in the melting process of Fig. 1; Fig. The melting furnace has a first chamber 21, a first chamber burner 26, a second chamber 31, a second chamber burner 36, a throat 41, and the like.

The first chamber 21 is filled with a raw material 12 of alkali-free glass. The first chamber (21) melts the raw material (12) and reserves the molten glass (14). The first chamber 21 includes a horizontal bottom wall 22, an upstream side wall 23 perpendicular to the bottom wall 22, a downstream side wall 24 parallel to the upstream side wall 23, a ceiling 25 For example, an arch-like ceiling). The downstream side wall 24 reaches the ceiling 25 as shown in Fig. 2, but it may be higher than the bubble layer 16 and may not reach the ceiling 25 as shown in Fig. At the upstream side wall 23, a charging port 23a for the raw material 12 is formed.

The first chamber burner 26 forms a flame by mixing a fuel such as natural gas or heavy oil with a gas and burning it. The first chamber burner 26 forms a flame in the upper space of the first chamber 21 and heats the raw material 12 or the like injected from the inlet 23a. The raw material 12 is melted by radiant heat or the like of the flame formed by the first chamber burner 26, and is gradually dissolved in the molten glass 14.

The first chamber burner 26 ejects flames from the openings of both the left and right side walls connecting the upstream side wall 23 and the downstream side wall 24 to the first chamber 21. The first chamber burner 26 may continuously spray the flame, or may spray the flame intermittently.

The first chamber burner 26 is disposed on each of the right and left side walls. The first chamber burners 26 may be arranged laterally symmetrically with the first chamber 21 therebetween, may be arranged in a zigzag manner with the first chamber 21 therebetween, They may be arranged in a zigzag manner.

Any one of an air combustion burner and an oxygen combustion burner is used for each of the first chamber burners 26. Of the plurality of first yarn burners 26, all may be oxygen burners, some may be oxygen burners, and the remaining amount may be air burners.

In the present specification, an air combustion burner refers to the use of air mainly as a gas to be mixed with fuel, and means that the oxygen concentration of the gas is 25% by volume or less. If the oxygen concentration of the gas is 25 vol% or less, a mixed gas of air and oxygen gas may be used, or air may be used.

In the present specification, the term "oxygen combustion burner" refers to the use of oxygen gas mainly as a gas to be mixed with fuel, and means that the oxygen concentration of the gas is 93 vol% or more. If the oxygen concentration of the gas is 93 vol% or more, a mixed gas of oxygen gas and air may be used, or only oxygen gas may be used.

Any one of the air combustion burner and the oxygen combustion burner is used for each first chamber burner 26, so that the NO _x emission amount can be reduced.

An electrode for electrically heating the molten glass 14 may be formed in the molten glass 14 of the first chamber 21 for the purpose of assisting heating of the molten glass 14 by the first chamber burner 26. [

It is preferable not to introduce a dry gas such as nitrogen gas into the upper space of the first chamber 21. [ It is possible to prevent a decrease in thermal efficiency and an increase in the amount of exhaust gas.

In the second chamber 31, the molten glass 14 formed by melting the raw material 12 is supplied from the first chamber 21. The second chamber (31) refines the molten glass (14) or adjusts the temperature. The second chamber 31 includes a horizontal bottom wall 32, an upstream side wall 33 perpendicular to the bottom wall 32, a downstream side wall 34 parallel to the upstream side wall 33, a ceiling 35 . At the lower portion of the downstream side wall 34, a blow-out port 34a for the molten glass 14 is formed.

The bottom wall 32 of the second chamber 31 and the bottom wall 22 of the first chamber 21 are integrated as shown in Fig. 2, but they may not be integrated as shown in Fig. 4, the bottom wall 32 of the second chamber 31 and the bottom wall 22 of the first chamber 21 may have a step D therebetween. The bottom wall 32 of the second chamber 31 and the bottom wall 22 of the first chamber 21 may be either higher.

The upstream side wall 33 of the second chamber 31 and the downstream side wall 24 of the first chamber 21 are integrated but may not be integrated as shown in Fig.

The ceiling 35 of the second chamber and the ceiling 25 of the first chamber 21 are integrated but may not be integrated. 5, the downstream side wall 24 of the first chamber 21 is connected to the ceiling 35 of the first chamber 21 and the ceiling 35 of the second chamber 21, And the upstream side wall 33 of the second chamber 31 are not integrated with each other.

The second chamber burner 36 forms a flame by mixing a fuel such as natural gas or heavy oil with a gas and burning it. The second chamber burner 36 forms a flame in the upper space of the second chamber 31 and heats the molten glass 14 supplied from the first chamber 21.

The second chamber burner 36 ejects flames from the openings of the left and right side walls connecting the upstream side wall 33 and the downstream side wall 34 to the second chamber 31. The second chamber burner 36 may continuously spray the flame, or may spray the flame intermittently.

The second chamber burner 36 is disposed on each of the left and right sidewalls connecting the upstream side wall 33 and the downstream side wall 34. The second chamber burners 36 may be arranged laterally symmetrically with the second chamber 31 interposed therebetween. The second chamber burners 36 may be arranged in a staggered manner with the second chamber 31 interposed therebetween. They may be arranged in a zigzag manner.

Each of the second chamber burners 36 uses either an air combustion burner or an oxygen combustion burner. Of the plurality of second seal burners 36, all may be air burners, some may be air burners, and the remaining amount may be oxygen burners.

Any one of the air combustion burner and the oxygen combustion burner is used for each second room burner 36, so that the NO _x emission amount can be reduced.

An electrode for energizing and heating the molten glass 14 may be formed in the molten glass 14 of the second chamber 31 for the purpose of assisting the heating of the molten glass 14 by the second chamber burner 36. [

It is preferable not to introduce a dry gas such as nitrogen gas into the upper space of the second chamber 31. [ It is possible to prevent a decrease in thermal efficiency and an increase in the amount of exhaust gas.

The throat 41 connects the lower portion of the first chamber 21 and the lower portion of the second chamber 31. The throat 41 is filled with the molten glass 14. A plurality of throats 41 may be formed. The molten glass 14 of the first chamber 21 is supplied to the second chamber 31 through the throat 41. [

The inlet of the throat 41 is formed in the downstream sidewall 24 of the first chamber 21 in Fig. 2 but may be formed in the bottom wall 22 of the first chamber 21 as well. Similarly, the outlet of the throat 41 is formed in the upstream wall 33 of the second chamber 31 in Fig. 2, but may also be formed in the bottom wall 32 of the second chamber 31. Fig.

However, the T ₂ of the alkali-free glass is 100 ° C or more higher than the T ₂ of the ordinary soda lime glass. Thus, in the present embodiment, the molten glass 14 is heated by using both the first and second seal burners 26 and 36.

In the case of alkali-free glass, the melting temperature of the raw material 12 is high and the bubble layer 16 is easily attached to the liquid surface of the molten glass 14 in the first chamber 21, as compared with the case of ordinary soda lime glass. The bubble layer 16 is an aggregate of small bubbles, and the bubbles are caused by generation of gas due to pyrolysis of the raw material 12 and the like. Foam layer 16 is liable to be formed especially in the case where the SiO ₂ content of 54 to 73% by weight alkali-free glass. The bubble layer (16) blocks heat radiation from the flame of the first chamber burner (26) to the molten glass (14).

Therefore, in this embodiment, 50 to 100% (preferably 55 to 100%, and more preferably 60 to 100%) of the total combustion heat amount per hour of all the first yarn burners 26 is supplied by the oxygen combustion burner .

In the case of an air combustion burner, nitrogen gas, which occupies most of the air, is exhausted outside the melting furnace without contributing to combustion. On the other hand, in the case of the oxygen combustion burner, since the exhaust amount is smaller than that of the air combustion burner, the thermal efficiency is high, and the CO ₂ emission amount and the NO _x emission amount are small.

It is possible to efficiently heat the molten glass 14 even if the bubble layer 16 is interposed, if 50 to 100% of the total combustion heat amount per hour of all the first chamber burners 26 is caused by the oxygen combustion burner, The molten glass 14 can be heated to a desired temperature. The total combustion heat amount is obtained by summing the heat amount generated when the fuel used in each burner is completely burned.

The molten glass 14 melted in the first chamber 21 is supplied to the second chamber 31. The molten glass 14 is supplied to the second chamber 31 through the throat 41 and the molten glass 14 is supplied to the second chamber 31 without being influenced by the bubble layer 16 of the first chamber 21 The bubble layer 16 is hardly formed in the second chamber 31 different from the first chamber 21 because the homogeneous molten glass 14 is supplied.

The liquid surface of the molten glass 14 is exposed in the second chamber 31 and the molten glass 14 is exposed to the atmosphere in the upper space of the second chamber 31. The gas in the atmosphere in the upper space of the second chamber 31 is dissolved in the molten glass 14.

However, in general alkali-containing glass, the larger the alkali content in the molten glass, the more easily B ₂ O ₃ in the molten glass is volatilized. B ₂ O ₃ is volatilized, for example, as a sodium compound.

On the other hand, in the case of alkali-free glass containing almost no alkali component such as Na in the molten glass, B ₂ O ₃ in the molten glass tends to volatilize as the moisture concentration in the atmosphere of the upper space becomes higher.

The amount of moisture in the atmosphere of the upper space depends on the type of the burner. In the case of the oxygen combustion burner, the concentration of moisture contained in the gas after combustion is higher than in the case of the air combustion burner, and B ₂ O ₃ in the molten glass is liable to volatilize.

Therefore, in the present embodiment, it is preferable that 75 to 100% (preferably 80 to 100%, more preferably 85 to 100%, and even more preferably 90 to 100%) of the total combustion heat amount per hour of all the second yarn burners 36 100%) is assumed to be caused by the air combustion burner.

It is preferable that the amount of the total combustion heat per hour of all the second room burners 36 is 75 to 100% by the air combustion burner, the amount of water in the upper space of the second chamber 31 Is low. As a result, the volatilization of B ₂ O _{3 in} the molten glass can be suppressed.

The distance L1 in the flow direction (lateral direction in FIG. 2) between the upstream end and the downstream end of the first chamber 21 is preferably 50 to 75% of the reference distance L0, more preferably 55 To 70%. The distance L2 in the flow direction (left-right direction in FIG. 2) between the upstream end and the downstream end of the second chamber 31 is preferably 10 to 40% of the reference distance L0, more preferably, the reference distance L0 Lt; / RTI > The reference distance L0 is the distance between the upstream end of the first chamber 21 and the downstream end of the second chamber 31 in the flow direction.

The molten glass 14 is balanced in the first chamber 21 and the second chamber 31 when the distance L1 is 50 to 75% of the reference distance L0 and the distance L2 is 10 to 40% .

In the embodiment of the present invention, among the first chamber burners 26, the total number of times of the total combustion of the first chamber burners 26 installed in the area away from the upstream end of the first chamber 21 by 0.5L1 or more It is assumed that 60% or more (preferably 65% or more, more preferably 70% or more, and more preferably 80% or more) of the heat quantity is caused by the oxygen combustion burner.

If the amount of exhaust gas is less than 60% of the total combustion heat amount per hour of the first chamber burner 26 provided in the above region, the amount of exhaust gas can be reduced and the molten glass 14 can be efficiently heated, An alkali-free glass sheet can be produced with a small gas consumption.

The present invention is not limited to the above-described embodiment, and can be applied to the melting furnace, the melting method, the method of producing an alkali-free glass plate, and the alkali- Various modifications and substitutions may be made to the embodiments.

For example, although the melting furnace of the above embodiment has the first chamber 21 and the second chamber 31, it is also possible to further include a third chamber in which the molten glass 14 is supplied from the second chamber 31 do. The melting furnace may have four or more chambers. Further, for example, a bubbler or the like may be provided on the bottom wall of the first chamber 21 and / or the second chamber 31 in order to promote dissolution and homogeneity of the glass.

12: Ingredients of alkali-free glass
14: molten glass
16: bubble layer
21: 1st room
22: bottom wall of the first room
23: upstream side wall of the first chamber
23a: input port of raw material
24: downstream side wall of the first chamber
25: Ceiling of room 1
26: First chamber burner
31: The second room
32: bottom wall of the second room
33: upstream side wall of the second chamber
34: downstream side wall of the second chamber
35: Ceiling of the second room
36: Second room burner
41: throat

Claims (3)

A first chamber into which a raw material of glass is introduced,
A first chamber burner for forming a flame in an upper space of the first chamber,
A second chamber in which molten glass obtained by melting the raw material is supplied from the first chamber,
A second yarn burner for forming a flame in an upper space of the second yarn,
And a throat for connecting a lower portion of the first chamber and a lower portion of the second chamber, the method comprising:
The raw material is a raw material for alkali-free glass having an SiO ₂ content of 54 to 73 mass% and a B ₂ O ₃ content of 0.1 to 12 mass%
Wherein either one of the oxygen combustion burner and the air combustion burner is used for each of the first room burner and each second room burner,
50 to 100% of the total combustion heat amount per hour of all the first filament burners is generated by the oxygen burner,
Wherein 75 to 100% of the total combustion heat amount per hour of all the second room burners is generated by the air combustion burner. The method according to claim 1,
The alkali-free glass is represented by mass% based on oxide,
SiO ₂ : 54 to 73%
Al ₂ O ₃ : 10 to 23%
B ₂ O ₃ : 0.1 to 12%
MgO: 0 to 12%
CaO: 0 to 15%
SrO: 0 to 16%
BaO: 0 to 15%
MgO + CaO + SrO + BaO: 8 to 26%
≪ / RTI > A dissolution step comprising the dissolution method according to claim 1 or 2,
And a molding step of molding the molten glass melted in the melting step into a plate.

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