CN111315693B - Method for manufacturing float glass and device for manufacturing float glass - Google Patents
Method for manufacturing float glass and device for manufacturing float glass Download PDFInfo
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- CN111315693B CN111315693B CN201880071650.1A CN201880071650A CN111315693B CN 111315693 B CN111315693 B CN 111315693B CN 201880071650 A CN201880071650 A CN 201880071650A CN 111315693 B CN111315693 B CN 111315693B
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B18/00—Shaping glass in contact with the surface of a liquid
- C03B18/02—Forming sheets
- C03B18/18—Controlling or regulating the temperature of the float bath; Composition or purification of the float bath
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
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Abstract
The present invention relates to a method for producing float glass, characterized in that a molten glass obtained by melting a glass raw material is formed into a glass ribbon on molten tin in a float bath, and the obtained glass ribbon is slowly cooled to obtain a glass plate.
Description
Technical Field
The present invention relates to a method for producing float glass with reduced tin defects and an apparatus for producing float glass.
Background
In the production of float glass, it is important to reduce the dissolution of molten tin by oxygen in the float bath. One reason for this is that tin oxide generated by dissolving oxygen in molten tin adheres to the lower surface of the float glass, thereby causing tin defects.
Conventionally, in order to prevent contact between molten tin and oxygen in a float bath, the float bath has a closed structure as much as possible, and nitrogen gas having a high purity is blown as a protective atmosphere gas to prevent intrusion of air, and hydrogen gas is simultaneously blown to remove oxygen in a minute amount of air that intrudes. In order to prevent oxygen from entering the air, the pressure of the protective atmosphere gas in the float bath is set to be slightly higher than the atmospheric pressure outside the float bath.
In recent years, further reduction of tin defects has been demanded in order to improve the production yield. In order to meet this demand, it is necessary to adopt a method of directly removing tin oxide itself from molten tin.
Therefore, patent document 1 proposes the following: a part of the molten tin in the tin bath is taken out from the tin bath, and tin oxide in the taken-out molten tin is reacted and removed, and then returned to the tin bath.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 4281141.
Disclosure of Invention
However, the method described in patent document 1 requires a circulation system for circulating the molten tin outside the tin bath, and in order to remove tin oxide in the molten tin, the molten tin needs to be cooled to a temperature equal to or lower than the minimum temperature in the tin bath, and the molten tin needs to be heated again before returning to the tin bath. Therefore, the method described in patent document 1 can reduce the tin defect, but has problems of complicated equipment configuration and manufacturing conditions, and high equipment investment and operation costs.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing float glass and an apparatus for manufacturing float glass, which can obtain a glass sheet with good quality under simple manufacturing conditions.
In order to solve the above problems, the present invention provides a method for producing float glass, comprising forming a molten glass obtained by melting a glass raw material on a molten metal in a float bath into a glass ribbon, and gradually cooling the glass ribbon to obtain a glass plate, wherein a plasma gas is jetted to a molten metal exposed portion exposed in an atmosphere in the float bath.
In the method for manufacturing float glass according to the present invention, it is preferable that the plasma gas is injected to the exposed molten metal portion at a distance of 0.3W or more in the width direction, where W (mm) is a distance in the width direction of the exposed molten metal portion.
In the method for producing float glass according to the present invention, the plasma gas is preferably sprayed to the molten metal exposed portion at a distance of 10 to 400mm in the flow direction.
In the method for producing float glass according to the present invention, it is preferable that the plasma gas is injected into the molten metal exposed portion so as to be separated from the molten metal exposed portion by a distance of 5 to 30mm in a vertical direction from above.
In the method for producing float glass according to the present invention, it is preferable that the plasma gas contains a gas selected from He, Ne, Ar, and N2、CO、CO2、H2、H2O、NH3、CH4、C2H2、C2H4And C2H6At least one of (1).
In the method for producing float glass according to the present invention, it is preferable that the plasma gas is ejected so that a hydrogen radical density in an atmosphere until reaching the molten metal exposed portion is 1 × 1011/cm3The above.
In the method for producing float glass of the present invention, it is preferable that the plasma gas is jetted to the molten metal exposed portion at a linear velocity of 0.1 to 200 m/s.
In the method for manufacturing a float glass according to the present invention, preferably,
the plasma gas is ejected from a plasma ejecting apparatus provided to face an upper side of the molten metal exposed portion,
the plasma spraying device is provided with a plasma gas spraying part for spraying plasma gas,
the plasma gas injection part includes a plurality of plasma generating devices,
the electron density of the plasma gas in a plasma region in which the gas introduced into the plasma generating device is converted into plasma is 1 × 1013/cm3The above.
In the method for producing float glass according to the present invention, it is preferable that the oxygen potential of the molten metal after plasma gas injection is 1/2 or less of the oxygen potential of the molten metal before plasma gas injection in the molten metal exposed portion.
In the method for manufacturing float glass according to the present invention, the temperature of the molten metal to which the plasma gas is injected is preferably 900 ℃.
The present invention also provides an apparatus for manufacturing a float glass, wherein a molten glass obtained by melting a glass raw material is formed into a glass ribbon on a molten metal in a float bath, and the obtained glass ribbon is slowly cooled to obtain a glass plate, wherein a plasma jet apparatus is disposed above a molten metal exposure portion exposed to an atmosphere in the float bath, the plasma jet apparatus includes a plasma gas jet portion and a support portion for supporting the plasma gas jet portion, and the plasma gas jet portion jets a plasma gas toward the molten metal exposure portion.
In the float glass manufacturing apparatus of the present invention, the plasma gas spraying section includes a plurality of plasma generating devices,
the plasma generation device is preferably arranged such that the longitudinal direction of the plasma generation device coincides with the flow direction of the glass ribbon.
In the plasma generating apparatus of the float glass manufacturing apparatus according to the present invention, the gas discharge portion preferably has a rectangular cross-sectional shape.
According to the present invention, float glass having good quality can be produced under simple production conditions.
Drawings
FIG. 1 is a plan view showing an example of the structure of a lower part of a float bath.
Fig. 2 is a partial sectional view taken along line I-I of fig. 1.
Fig. 3 (a) and 3 (b) are schematic views of main portions of the plasma spray device, fig. 3 (a) is a schematic view as viewed from a planar direction, and fig. 3 (b) is a schematic view as viewed from a cross-sectional direction of fig. 2.
Fig. 4(a) is a cross-sectional view showing an example of the configuration of the plasma generator, and fig. 4 (b) is a partial cross-sectional view taken along line II-II of fig. 4 (a).
Fig. 5 (a) is a cross-sectional view showing another configuration example of the plasma generating apparatus, and fig. 5 (b) is a partial cross-sectional view taken along line III-III of fig. 5 (a).
FIG. 6 is SnO showing examples and comparative examples in which the temperature of a glass plate is 500 DEG C2Graph of reduction rate.
FIG. 7 shows SnO values of examples and comparative examples in which the glass plate temperature is 625 deg.C2Graph of reduction rate.
FIG. 8 is SnO showing examples and comparative examples in which the glass plate temperature is 750 ℃2Graph of reduction rate.
FIG. 9 shows SnO2Graph of the distance dependence of the reduction rate between the plasma gas ejection site and the ejected site.
FIG. 10 shows SnO2Graph of the linear velocity dependence of the plasma gas of the reduction rate.
FIG. 11 shows SnO resulting from absence of the No. 2 discharge part of the plasma generating apparatus2Graph of the difference in reduction rate.
Fig. 12 is a graph showing the time course of the oxygen potential of the molten tin before and after the injection of the plasma gas.
Detailed Description
Hereinafter, a method for manufacturing a float glass and an apparatus for manufacturing a float glass according to an embodiment of the present invention will be described with reference to the drawings.
The present invention provides a glass sheet obtained by forming molten glass obtained by melting glass raw materials into a glass ribbon on molten metal in a float bath and slowly cooling the glass ribbon obtained.
FIG. 1 is a plan view showing an example of the structure of a lower part of a float bath, and FIG. 2 is a partial sectional view taken along line I-I of FIG. 1.
The float bath 100 shown in the figure is composed of a molten metal bath 10 for containing molten tin 20, a roof 12 disposed above the molten metal bath 10, and the like.
The metal stored in the molten metal bath 10 may be a tin alloy, a metal other than tin, or an alloy thereof. A tin alloy is for example an alloy of tin and copper. The metal other than tin is, for example, bismuth. Further, an alloy of a metal other than tin is, for example, an alloy of bismuth and copper.
Molten glass obtained by melting a glass raw material is continuously supplied to the molten tin 20 in the molten metal bath 10. The molten glass is made to flow over the molten tin 20 in the molten metal bath 10, and formed into a ribbon-shaped glass ribbon G. The glass ribbon G moves in the direction of the arrow in the figure. Hereinafter, in the present specification, the direction of the arrow in the drawing is referred to as the flow direction of the glass ribbon G, and the direction perpendicular to the arrow direction is referred to as the width direction of the glass ribbon G. In the present specification, the "flow direction" and the "width direction" correspond to the "flow direction of the glass ribbon G" and the "width direction of the glass ribbon G", respectively.
The molten metal bath 10 includes a wide region Z1 having a wide width, a middle region Z2 having a narrow width, and a narrow region Z3 having a narrow width in this order from the upstream side in the flow direction of the glass ribbon G. Between the glass ribbon G and the side walls of the molten metal bath 10 (hereinafter, sometimes referred to as the left and right sides of the glass ribbon G), there are molten metal exposed portions 22 where the molten tin 20 is exposed in the atmosphere in the float bath 100. The plasma jet apparatus 30 is disposed above the molten metal exposure portion 22 on both the left and right sides of the glass ribbon G in the narrow region Z3.
The plasma spraying device 30 includes a plasma gas spraying portion 31 and a support portion 32 for supporting the plasma gas spraying portion 31. The plasma gas injection part 31 is provided so as to protrude below the support part 32. The plasma gas injection portion 31 is constituted by a plurality of plasma generation devices 40a described later, and injects a gas (hereinafter, referred to as a plasma gas) converted into a plasma toward the molten metal exposure portion 22. The support portion 32 is provided therein with a duct for supplying the gas turned into plasma to the plasma generation device 40a and a wiring for applying a voltage to the electrode of the plasma generation device 40 a.
The plasma gas injection portion 31 may be provided inside the support portion 32. In this case, the support portion 32 must have a height for accommodating at least the plasma generation device 40 a.
Fig. 3 is a schematic view of a main portion of the plasma spray device, fig. 3 (a) is a schematic view as viewed from a planar direction, and fig. 3 (b) is a schematic view as viewed from a sectional direction of fig. 2.
The plasma spraying device 30 includes a plasma gas spraying portion 31 and a support portion 32. The plasma gas ejection portion 31 shown in fig. 3 (a) is composed of 8 plasma generation devices 40a, and the distance in the width direction of the plasma gas ejection portion 31 is W1 and the distance in the flow direction is L1. Here, the "widthwise distance of the plasma gas ejecting section 31" means the distance (length) of the plasma gas ejecting section 31 along the widthwise direction of the glass ribbon. Further, the "distance in the flow direction of the plasma gas ejecting portion 31" means the distance (length) of the plasma gas ejecting portion 31 along the flow direction of the glass ribbon.
The plasma generation device 40a may be disposed such that the longitudinal direction of the plasma generation device 40a coincides with the flow direction of the glass ribbon. In fig. 3 (a), the plasma generation devices 40a are arranged in 2 rows along the flow direction of the glass ribbon and 4 rows along the width direction of the glass ribbon.
The plasma generating devices 40a are preferably arranged in 1 to 6 rows along the flow direction of the glass ribbon and in 1 to 15 rows along the width direction of the glass ribbon. The plasma generation device 40a may be disposed such that the longitudinal direction of the plasma generation device 40a coincides with the width direction of the glass ribbon. In this case, the plasma generating devices 40a may be arranged in 1 to 15 rows along the flow direction of the glass ribbon and in 1 to 6 rows along the width direction of the glass ribbon.
Gaps may be provided between adjacent plasma generating devices 40a along the flow direction or the width direction of the glass ribbon. The gap is preferably small in order to uniformly inject the plasma gas in the flow direction or the width direction of the glass ribbon.
The plasma gas injection unit 31 may replace all or a part of the plasma generation device 40a with a plasma generation device 40b described later.
Fig. 4(a) is a cross-sectional view showing an example of the configuration of the plasma generation device 40a, and fig. 4 (b) is a partial cross-sectional view taken along line II-II of fig. 4 (a). In the plasma generation device 40a shown in fig. 4(a), a gas introduction portion 42 for introducing a gas turned into a plasma is provided above a housing 41 made of a sintered body such as alumina. Below the gas introduction portion 42, there is a plasma formation region P in which the introduced gas is formed into plasma. In the plasma formation region P, 2 electrodes 44 are inserted at intervals from the side surface of the housing 41, and a predetermined voltage is applied between the electrodes 44 to generate an electric discharge while continuously introducing a gas from the gas introduction portion 42, thereby converting the introduced gas into plasma. The gas (plasma gas) turned into plasma is discharged from a gas discharge portion 43 provided at a lower portion of the frame 41.
As shown in fig. 4 (b), the cross-sectional shape of the gas discharge portion 43 is a rectangle having a long side in the longitudinal direction of the electrode 44, and preferably a linear rectangle (slit) having a short side. This increases the number of reactive species of the plasma gas discharged from the gas discharge portion 43, thereby promoting the reduction of tin oxide.
Fig. 5 (a) is a cross-sectional view showing another configuration example of the plasma generating apparatus, and fig. 5 (b) is a partial cross-sectional view taken along line III-III of fig. 5 (a). In the plasma generation device 40b shown in fig. 5 (a), a 2 nd discharge unit 45 is provided below the gas discharge unit (1 st discharge unit) 43. In the 2 nd discharge part 45, a plurality of holes are arranged linearly, and radicals of the same density can be ejected along the longitudinal direction of the electrode 44. As shown in fig. 5 (b), the cross-sectional shape of the hole provided in the 2 nd discharge part 45 is circular, and may be polygonal such as an ellipse, a triangle, or a quadrangle. This can suppress a discharge phenomenon of the plasma gas to the object to be processed.
In the plasma generation device 40b shown in fig. 5 (b), the ratio of the total cross-sectional area of the holes in the entire lower surface of the plasma generation device 40b is preferably 0.01 to 5%.
The plasma generating devices 40a, 40b shown in fig. 4(a) and 5 (a) are preferably in the form of a plasma discharge in the form of a hollow cathode discharge. However, the plasma discharge form of the plasma generation device may be, but is not limited to, Dielectric Barrier Discharge (DBD) or arc discharge. Further, high-frequency induction discharge or microwave discharge may be used without using an electrode. Further, the discharge may be performed by a high-frequency power supply.
In the embodiment of the present invention, the plasma gas is injected from the plasma gas injection portion 31 of the plasma injection device 30 to the molten metal exposed portion 22. Thereby, the tin oxide present in the vicinity of the surface of the molten tin 20 is reduced by the mechanism described below.
As shown in the following formula (1), the oxygen in the atmosphere in the float bath 100 or the oxygen in the molten glass is dissolved in the molten tin 20 in the molten metal bath 10 to generate tin oxide SnOx(0＜x≤2)。
Sn+O2→SnOx (1)
The reason why hydrogen gas is blown in while high-purity nitrogen gas is blown in the atmosphere in the float bath 100 is to use hydrogen in the atmosphere to make tin oxide SnO in the molten tin 20 as shown in the following formula (2)xAnd reduced to return metallic tin Sn.
SnOx+H2→Sn+H2O(g) (2)
When the plasma gas is jetted to the molten metal exposed portion 22, hydrogen present in the plasma gas or hydrogen in the atmosphere in the float bath 100 is radicalized or ionized. As a result, hydrogen radicals and hydrogen ions as reactive species are supplied at a higher density, and the reaction represented by the above formula (2) is promoted.
It is confirmed from the examples described later that the reaction represented by the above formula (2) is accelerated when the plasma gas is injected.
Tin oxide present near the surface of molten tin adheres to the lower surface of float glass to cause tin defects.
In the embodiment of the present invention, since the reduction of the tin oxide existing in the vicinity of the surface of the molten tin 20 is promoted by injecting the plasma gas to the molten metal exposure portion 22, float glass having good quality with few tin defects can be manufactured.
In the embodiment of the present invention, when the distance in the width direction of the molten metal exposed portion 22 (the distance (length) of the molten metal exposed portion 22 along the width direction of the glass ribbon G and the distance between the glass ribbon G and the inner wall of the molten metal bath 10) is W (mm), it is preferable to inject the plasma gas at a distance of 0.3W or more in the width direction because it acts to promote the reduction of the tin oxide existing in the vicinity of the surface of the molten tin 20. The widthwise distance at which the plasma gas is ejected coincides with the widthwise distance W1 of the plasma gas ejection portion 31. The width direction distance W1 is more preferably 0.5W or more, and still more preferably 0.7W or more. However, if the width direction distance W1 is equal to or greater than W, the plasma jet device 30 is present above the glass ribbon G, and therefore, there is a possibility that foreign matter adhering to the plasma jet device 30 falls on the glass ribbon G and causes defects. Therefore, the width direction distance W1 is preferably W or less.
In fig. 1 and 2, a part of the plasma jet apparatus 30 is located outside the molten metal bath 10 for connection to an external device such as a power supply.
As shown in fig. 1, the distance W in the width direction of the molten metal exposed portion 22 differs depending on the position of the molten metal exposed portion 22 in the molten metal bath 10, specifically, the position in the flow direction of the glass ribbon G.
The distance W in the width direction of the molten metal exposed portion 22 also differs depending on the size and shape of the molten metal bath 10.
The distance W in the width direction of the molten metal exposed portion 22 at the position where the plasma jet apparatus 30 is disposed is preferably 100 to 600mm, more preferably 200 to 500 mm. The reason for this is as described below.
When the distance W in the width direction is 100mm or more, even if the glass ribbon G fluctuates in the width direction, it is possible to prevent trouble that the glass ribbon G contacts and adheres to the side wall of the molten metal bath 10. Further, when the distance W in the width direction is 600mm or less, the glass ribbon G having a wide width can be efficiently molded without increasing the dimension of the molten steel bath 10 in the width direction.
In the embodiment of the present invention, it is preferable that the plasma gas is jetted at a distance of 10 to 400mm in the flow direction. The flow direction distance of the injected plasma gas coincides with the flow direction distance L1 of the plasma gas injection part 31. The distance L1 in the flow direction is more preferably 50 to 400 mm. Here, the "flow direction distance L1 of the plasma gas ejection portion 31" means the distance (length) of the plasma gas ejection portion 31 along the flow direction of the glass ribbon.
In the embodiment of the present invention, it is preferable that the plasma gas is injected from the molten metal exposed portion 22 to the upper side so as to be separated by a distance of 5 to 30mm in the vertical direction. The vertical distance is equal to the vertical distance between the plasma gas ejecting part 31 and the molten metal exposed part 22. If the vertical distance is increased, the above-described effect by the injection of the plasma gas is reduced. However, if the vertical distance is too small, the plasma gas injection portion 31 may come into contact with the molten metal exposure portion 22 and the glass ribbon G present on the molten tin 20. The vertical distance is more preferably 5 to 20 mm.
In fig. 1 and 2, 1 plasma jet apparatus 30 is disposed on each of the right and left sides of the glass ribbon G. When the plurality of plasma jet apparatuses 30 are arranged along the flow direction of the molten metal exposed portion 22, the distance between the plurality of plasma jet apparatuses is not particularly limited, and may be appropriately selected according to the number of arranged plasma jet apparatuses and the flow direction distance of the glass ribbon G in the plasma jet apparatuses.
Here, as is clear from fig. 4(a), the range in which the plasma generating apparatus 40a injects the plasma gas is determined by the size of the gas discharge portion 43, and the size of the gas discharge portion 43 substantially matches the distance between the electrodes 44. The distance between the electrodes is preferably 1 to 600 mm. The distance in the longitudinal direction of the frame 41 is preferably 5 to 600 mm. Further, the distance in the depth direction of the paper surface of the housing 41 in fig. 4(a) and 5 (a) is preferably 5 to 400 mm.
As described above, since the reaction represented by the above formula (2) is promoted by the injection of the plasma gas, the plasma gas preferably contains an inert gas and/or a reducing gas. The kind of gas contained in the plasma gas is the same as the gas introduced from the gas introduction portion 42.
Examples of the inert gas include He, Ne, Ar, and N2. Examples of the reducing gas include CO and CO2H containing H in the molecule2、H2O、NH3、CH4、C2H2、C2H4、C2H6. Of these, the plasma gas preferably contains a gas selected from He, Ne, Ar, and N2、CO、CO2、H2、H2O、NH3、CH4、C2H2、C2H4And C2H6At least one of (1).
Therefore, the plasma gas may contain He, Ne, Ar, N only2Such as an inert gas. Among these, Ar and N are preferable from the viewpoint of cost2. Ar and N2Only 1 species of them may be used, or 2 species may be used in combination.
The reducing gas is preferably H from the viewpoint of low cost and large amount of reactive species generated2。
More preferably, the plasma gas contains H2. In this case, only H may be contained2May also contain H2And an inert gas. Containing H2And an inert gas, for example, H2And Ar gas, containing H2And N2Of a gas containing H2Ar and N2The gas of (2).
E.g. the plasma gas contains H2In the case of selecting a gas species that actively generates hydrogen radicals as reactive species as in the case of (1), the hydrogen radical density in the atmosphere until reaching the molten metal exposed portion 22 by injecting the plasma gas is preferably 1 × 10 in terms of room temperature conversion11/cm3Above, more preferably 1 × 1012/cm3The above. If the hydrogen radical density is 1X 1011/cm3As described above, even in the lowest temperature portion of the atmosphere in the float bath 100, the reduction of tin oxide present in the vicinity of the surface of the molten tin 20 is promoted.
It should be noted that, in the description,when the plasma gas contains only the inert gas, hydrogen in the atmosphere in the float bath 100 is entrained between the plasma gas ejection portion 31 and the molten metal exposure portion 22 and is converted into radicals, and therefore the hydrogen radical density is 1 × 1011/cm3Left and right.
The hydrogen radical density was measured by vacuum ultraviolet spectroscopy. As the light source, a micro hollow plasma light emitting source whose spectrum is known is used, and as the detector, a monochromatic light beam splitter with a photoelectron multiplying tube is used. Light sources located on the front side of the plasma generation devices 40a and 40b shown in fig. 4(a) and 5 (a) are used to aim at positions separated by 0 to 10mm from the center position in the longitudinal direction of the plasma gas ejection site toward the lower side of the paper surface, and absorption intensity is measured by detectors located on the back side of the paper surface of the plasma generation devices 40a and 40 b. From this, the hydrogen radical density is calculated from known spectral information and found.
In the embodiment of the present invention, it is preferable that the plasma gas is ejected at a linear velocity (converted into room temperature) of 0.1 to 200m/s in any gas type. If the linear velocity is 0.1m/s or more, hydrogen radicals can be sufficiently transported to the molten metal exposed portion 22. Further, when the linear velocity is 200m/s or less, the fluctuation of the liquid surface of the molten metal exposed portion 22 can be suppressed.
Preferably, when any gas species is contained, the electron density of the plasma gas in the plasma formation region P is 1X 10 in terms of room temperature conversion13/cm3The above.
The electron density of the plasma gas was calculated by measuring the stark broadening of the barmer β line of hydrogen in luminescence analysis of the plasma at room temperature. The emission of the plasma gas is detected by a multichannel spectrometer with a ccd array on the lower side of the paper of the plasma generation apparatuses 40a and 40b shown in fig. 4(a) and 5 (a). The density of the plasma gas is calculated from the half-value width resulting from the stark broadening of the resulting hydrogen's barmer β line.
In fig. 1, the plasma jet device 30 is disposed in the narrow region Z3 on the downstream side in the flow direction of the glass ribbon G in the molten metal exposed portion 22, but the present invention is not limited to this, and the plasma jet device may be disposed in the wide region Z1 and the intermediate region Z2 on the upstream side in the flow direction of the glass ribbon G.
However, when the plasma spraying device is disposed on the upstream side in the flow direction of the glass ribbon, the molten tin reduced from the tin oxide may be oxidized again. Therefore, the plasma jet apparatus 30 is preferably disposed in the narrow region Z3 on the downstream side in the flow direction of the glass ribbon G.
In the molten metal exposed portion 22 in the molten metal bath 10, the oxygen potential after the plasma gas injection is preferably 1/2 or less of the oxygen potential before the plasma gas injection. This is because the oxygen potential in the molten metal decreases as the reduction of tin oxide is promoted by the plasma gas.
The oxygen potential can be measured using a zirconia-type oxygen sensor. Specifically, a metal measuring electrode, a reference electrode having a generally constant oxygen potential, and a sensor are immersed in the molten metal bath 10, and the oxygen potential can be determined from the voltage difference between the electrodes due to the difference in oxygen potential. The sensor uses stabilized zirconia that exhibits oxygen ion conductivity at high temperatures.
When the temperature of the molten metal to which the plasma gas is injected is taken into consideration, the molten metal temperature is preferably 900 ℃ or lower. The molten metal temperature of the narrow region Z3 is usually 900 ℃ or lower, although it depends on the composition of the glass produced by the float process. The temperature of the molten metal to which the plasma gas is injected is preferably selected as appropriate in a temperature region of 900 ℃ or lower depending on the composition of the glass to be produced. The lower limit of the temperature of the molten metal to which the plasma gas is injected is not particularly limited, and the molten metal temperature is usually 500 ℃ or higher in order to inject the plasma gas to the molten metal exposed portion 22 in the molten metal bath 10.
Embodiments of the present invention can be widely applied to a glass sheet manufactured by a float process. The glass composition is not particularly limited, and the glass composition can be applied to glasses having a wide range of compositions, such as soda-lime-silicate glass, aluminosilicate glass, borosilicate glass, and alkali-free glass.
The thickness of the glass plate produced by the embodiment of the present invention is not particularly limited, but is preferably 0.1 to 2.0 mm.
Examples
The present invention will be further described with reference to examples.
In examples, SnO deposited on a glass plate by sputtering2The film was evaluated for SnO when injecting plasma gas according to the procedure shown below2The membrane reduction rate.
As the glass plate, a 20mm square quartz glass plate was used. SnO was coated on the entire surface of one main surface of the glass plate to a thickness of 500nm2And sputtering the film to form the film. Thereafter, for SnO2The center of the film was masked at 5mm and other SnO removed using an etching solution2Film formed with SnO remaining only in mask portion2Samples of the film. This is for the purpose of plasma gas to SnO2The membrane was treated uniformly throughout for analysis.
SnO was treated from a plasma generator 40b shown in FIG. 5 in a state where the glass plate was heated to 500 ℃, 625 ℃ or 750 ℃2The film ejects a plasma gas.
The discharge mode of the plasma generation device 40b shown in fig. 5 (a) is a micro-hollow cathode discharge, the distance between the electrodes 44 is 20mm, and the distance from the lower surface of the plasmatization region P to the 1 st discharge part 43 is 6 mm. The height of the 2 nd discharge part 45 was 1mm, the diameter of the hole having a circular cross-sectional shape formed in the 2 nd discharge part 45 was 0.5mm, and the ratio of the total cross-sectional area occupied by the holes in the entire lower surface of the plasma generation device 40b was 0.55%.
Ar and H are supplied from a gas introducing part 42 at a linear speed of 12.1m/s with the pressure of the plasma forming region P set as the atmospheric pressure2Mixed gas (H) of (2)28 vol%) as a gas to be converted into plasma.
A voltage of 9kV was applied between the electrodes 44 by a high-frequency power supply having a frequency of 20 kHz.
Plasma gas ejection site (lower surface of No. 2 exhaust part 45) — ejection target site (SnO)2Film) was 5 mm.
The treatment time (plasma gas ejection time) is 10sec to 90 sec.
SnO after plasma gas ejection2The membrane was treated with 17.5% hydrochloric acid and then subjected to fluorescent X-ray analysis (XRF). SnO before plasma gas injection2The film was also subjected to XRF.
The calculated residual film thickness I (nm) was calculated from Tin-count obtained by XRF using the following formula.
Tin-count after I [ nm ] ═ 500[ nm ] × plasma gas injection (after hydrochloric acid treatment)/Tin-count before plasma gas injection
The curve of the residual film thickness I converted with respect to the process time (plasma gas injection time) was plotted, and the slope thereof was defined as SnO2The membrane reduction rate.
As a comparative example, the method is not applied to SnO in a state where a glass plate is heated to 500 ℃, 625 ℃ or 750 ℃2The sample whose film was sprayed with the plasma gas and kept for the above treatment time was also subjected to hydrochloric acid treatment, and then subjected to XRF.
The results are shown in FIGS. 6 to 11. FIG. 6 shows SnO values of examples (with plasma) and comparative examples (without plasma) in which the glass plate temperature is 500 deg.C2Graph of reduction rate. FIG. 7 shows SnO values of examples (with plasma) and comparative examples (without plasma) in which the glass plate temperature is 625 deg.C2Graph of reduction rate. FIG. 8 shows SnO values of examples (with plasma) and comparative examples (without plasma) in which the glass plate temperature is 750 deg.C2Graph of reduction rate. From these results, it is understood that SnO was improved by injecting plasma gas2The reduction rate. Further, SnO2The reduction rate is dependent on the temperature of the glass sheet, and in the temperature region of this operation, SnO is observed at a higher temperature2The greater the reduction rate.
The plasma gas injection site (lower surface of the 2 nd discharge part 45) to the injection site (SnO) was set to a glass plate temperature of 500 ℃ and a treatment time (plasma gas injection time) of 60sec2Films) were carried out at 3 values of 5mm, 10mm, and 15 mm. FIG. 9 is a graph showing SnO based on the results2Reduction speedGraph of the distance dependence of plasma gas injection site-injected site of the intensity. From FIG. 9, it is clear that SnO2The reduction rate is inversely related to the distance between the plasma gas ejection site and the ejection site, and SnO is observed as the distance between the plasma gas ejection site and the ejection site is larger2The smaller the reduction rate. This is considered to be because the larger the distance is, the more the inactivation amount of hydrogen radicals as reactive species becomes.
Ar and H were supplied from the gas introducing portion 42 at 3 linear velocities of 4.04m/s, 12.1m/s, and 24.3m/s, assuming that the glass plate temperature was 500 ℃ and the treatment time (plasma gas injection time) was 60sec2Mixed gas (H) of (2)28 vol%) was carried out. FIG. 10 shows SnO2Graph of the linear velocity dependence of the plasma gas of the reduction rate. From FIG. 10, it is understood that SnO2The reduction rate is positively correlated with the linear velocity of the plasma gas, and the higher the linear velocity of the plasma gas is, the SnO2The higher the reduction rate. This is considered to be because the larger the linear velocity of the plasma gas is, the more the amount of hydrogen radicals that are reactive species are delivered to the object to be processed without being inactivated.
FIG. 11 shows SnO of the plasma generator without the 2 nd discharge part2Graph of the difference in reduction rate. The linear velocity was set to 4.04m/s, and the plasma gas ejection site-the ejection site (SnO)2Film) was set to 5mm, and the treatment time (plasma gas ejection time) was set to 60sec, and the treatment was carried out at 3 values of 500 ℃, 625 ℃, and 750 ℃ for the glass plate temperature. The cross-sectional shape of the gas discharge portion 43 of the plasma generation device 40a shown in fig. 4 is a linear rectangle having a longitudinal distance (long side) of 20mm from the electrode 44 and a short side of 0.3 mm. The cross-sectional shape of the 2 nd discharge part 45 of the plasma generation device 40b shown in fig. 5 is a shape in which 21 circles are arranged in parallel along the longitudinal direction of the electrode 44 with a diameter of 0.5mm and a pitch of 0.5 mm. As can be seen from fig. 11, the reduction rate of the plasma generator 40a is higher than that of the plasma generator 40 b. This is considered to be because the plasma generation device 40b has a larger wall area in contact with the plasma gas than the plasma generation device 40a, and the reaction is causedThe amount of active species trapped and inactivated increases.
Fig. 12 is a graph showing the time course of the oxygen potential of the molten tin before and after the plasma gas is ejected. An alumina crucible having a depth of 25mm was charged with 300g of tin and heated to 750 ℃ to form molten tin. Ar and H to be made into plasma by using a plasma generating apparatus 40a shown in FIG. 42Mixed gas (H) of (2)24 vol%) of molten tin before and after the molten tin was sprayed, the oxygen potential of the molten tin was measured by a zirconia-type oxygen sensor. The distance from the surface of the molten tin to the gas discharge portion 43 of the plasma generation device 40a was 5mm, and the measurement portion of the zirconia-type oxygen sensor was disposed at a depth of 20mm from the surface of the molten tin. The arrows in FIG. 12 indicate that Ar and H are2The time zone of the plasma formation of the mixed gas of (1) has a larger absolute value of the slope than the time zone of the plasma formation. This indicates that the decay rate of the oxygen potential in the time zone of plasmatization is fast.
In addition, in the vicinity of 300 minutes in FIG. 12, there were no plasma-formed Ar and H2The mixed gas of (3) has a common logarithmic value of oxygen potential converged to the vicinity of-23, whereas the plasmatized Ar and H2The mixed gas of (2) has a common logarithmic value of oxygen potential converged to about-24.3 in about 380 minutes. This is considered to be a result of shifting the equilibrium value of the oxygen potential of the molten tin to a smaller value by plasmatization. It is considered that the equilibrium value varies depending on the distance between the molten tin and the plasma generating device 40a, the concentration of the plasma gas, the linear velocity, and the like.
The present invention is described in detail with reference to specific embodiments, but it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.
The present application is based on japanese patent application 2017-214508, filed on 11/7/2017, the contents of which are incorporated herein by reference.
Description of the symbols
10: molten metal bath
12: top part
20: molten tin
22: molten metal exposed portion
30: plasma jet device
31: plasma gas injection part
32: support part
40a, 40 b: plasma generating device
41: frame body
42: gas introduction part
43: gas discharge part (No. 1 discharge part)
44: electrode for electrochemical cell
45: 2 nd discharge part
G: glass ribbon
P: plasmatizing zone
Claims (12)
1. A method for producing float glass, characterized in that a molten glass obtained by melting a glass raw material is formed into a glass ribbon on a molten metal in a float bath, and the glass ribbon obtained is slowly cooled to obtain a glass plate,
and injecting a plasma gas into a molten metal exposed portion exposed in the atmosphere in the float bath so as to be separated by a distance of 5 to 30mm in a vertical direction from the molten metal exposed portion upward.
2. The method of manufacturing float glass according to claim 1, wherein the plasma gas is jetted to the molten metal exposed portion at a distance of 0.3W or more in the width direction when the distance in the width direction of the molten metal exposed portion is W mm.
3. A method of manufacturing float glass according to claim 1 or 2, wherein the plasma gas is jetted to the molten metal exposed portion at a distance of 10 to 400mm in a flow direction.
4. The method for manufacturing float glass according to any one of claims 1 to 3, wherein the plasma gas contains a gas selected from He, Ne, Ar, N2、CO、CO2、H2、H2O、NH3、CH4、C2H2、C2H4And C2H6At least one of (1).
5. The method of manufacturing float glass according to claim 4, wherein the plasma gas is ejected so that a hydrogen radical density in an atmosphere until reaching the molten metal exposed portion is 1 x 1011/cm3The above.
6. A float glass production method according to claim 4 or 5, wherein the plasma gas is jetted at a linear velocity of 0.1 to 200m/s to the molten metal exposed portion.
7. The method of manufacturing a float glass according to any one of claims 1 to 6, wherein the plasma gas is ejected from a plasma ejection device provided to face an upper side of the molten metal exposed portion,
the plasma spraying device is provided with a plasma gas spraying part for spraying the plasma gas,
the plasma gas ejection section includes a plurality of plasma generation devices,
the electron density of the plasma gas in a plasma region in which the gas introduced into the plasma generating device is converted into plasma is 1 × 1013/cm3The above.
8. The method for producing float glass according to any one of claims 1 to 7, wherein the oxygen potential of the molten metal after plasma gas injection is 1/2 or less of the oxygen potential of the molten metal before plasma gas injection in the molten metal exposed portion.
9. The method of manufacturing a float glass according to any one of claims 1 to 8, wherein the temperature of the molten metal to which the plasma gas is injected is 900 ℃ or lower.
10. A float glass production apparatus, characterized in that it is a float glass production apparatus for forming a molten glass obtained by melting a glass raw material on a molten metal in a float bath into a glass ribbon, slowly cooling the obtained glass ribbon to obtain a glass sheet,
a plasma jet device is disposed above the molten metal exposed portion in the atmosphere in the float bath so as to be separated by a distance of 5 to 30mm in the vertical direction,
the plasma spraying device comprises a plasma gas spraying part and a supporting part for supporting the plasma gas spraying part,
the plasma gas injection unit injects a plasma gas to the molten metal exposed portion.
11. The manufacturing apparatus of a float glass according to claim 10, wherein the plasma gas injection part comprises a plurality of plasma generating devices,
the plasma generation device is disposed such that the longitudinal direction of the plasma generation device coincides with the flow direction of the glass ribbon.
12. The float glass manufacturing apparatus according to claim 11, wherein a cross-sectional shape of the gas discharge portion of the plasma generating apparatus is a rectangle.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017214508 | 2017-11-07 | ||
| JP2017-214508 | 2017-11-07 | ||
| PCT/JP2018/040776 WO2019093231A1 (en) | 2017-11-07 | 2018-11-01 | Method for producing float glass, and apparatus for producing float glass |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111315693A CN111315693A (en) | 2020-06-19 |
| CN111315693B true CN111315693B (en) | 2022-06-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201880071650.1A Active CN111315693B (en) | 2017-11-07 | 2018-11-01 | Method for manufacturing float glass and device for manufacturing float glass |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP7173040B2 (en) |
| KR (1) | KR102518796B1 (en) |
| CN (1) | CN111315693B (en) |
| WO (1) | WO2019093231A1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1202468A (en) * | 1997-06-13 | 1998-12-23 | Ppg工业公司 | Method and apparatus for reducing tin defects in float glass |
| KR20100037990A (en) * | 2008-10-02 | 2010-04-12 | 주식회사 엘지화학 | Method for manufacturing float glass and apparatus for manufacturing the same |
| KR20130009048A (en) * | 2011-07-14 | 2013-01-23 | 주식회사 엘지화학 | Apparatus and method for removing dross in float bath |
| CN105683101A (en) * | 2013-10-31 | 2016-06-15 | 旭硝子株式会社 | Tin alloy float bath, device for manufacturing float glass, method of manufacturing float glass, and float glass |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4281141B2 (en) | 1999-02-23 | 2009-06-17 | 旭硝子株式会社 | Float glass manufacturing method and apparatus |
| EP2414296A1 (en) * | 2009-03-31 | 2012-02-08 | Pilkington Group Limited | Method and apparatus for reducing tin oxide in float glass production |
| WO2013179862A1 (en) * | 2012-05-28 | 2013-12-05 | 旭硝子株式会社 | Device for molding float glass, and method for producing float glass |
-
2018
- 2018-11-01 JP JP2019552757A patent/JP7173040B2/en active Active
- 2018-11-01 KR KR1020207012578A patent/KR102518796B1/en active IP Right Grant
- 2018-11-01 CN CN201880071650.1A patent/CN111315693B/en active Active
- 2018-11-01 WO PCT/JP2018/040776 patent/WO2019093231A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1202468A (en) * | 1997-06-13 | 1998-12-23 | Ppg工业公司 | Method and apparatus for reducing tin defects in float glass |
| KR20100037990A (en) * | 2008-10-02 | 2010-04-12 | 주식회사 엘지화학 | Method for manufacturing float glass and apparatus for manufacturing the same |
| KR20130009048A (en) * | 2011-07-14 | 2013-01-23 | 주식회사 엘지화학 | Apparatus and method for removing dross in float bath |
| CN105683101A (en) * | 2013-10-31 | 2016-06-15 | 旭硝子株式会社 | Tin alloy float bath, device for manufacturing float glass, method of manufacturing float glass, and float glass |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2019093231A1 (en) | 2019-05-16 |
| KR102518796B1 (en) | 2023-04-10 |
| CN111315693A (en) | 2020-06-19 |
| KR20200070283A (en) | 2020-06-17 |
| JP7173040B2 (en) | 2022-11-16 |
| JPWO2019093231A1 (en) | 2020-11-19 |
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