Method of making float glass

Abstract

The present invention relates to a float glass manufacturing method. The float glass manufacturing method includes drawing a glass ribbon, which is formed on a molten metal stored in a float bath, from the float bath using n (n is a natural number of 2 or more) convey rollers provided inside a scum box, and sending the glass ribbon to a lehr. The float glass manufacturing method includes a process of bringing a carbon member into contact with each of the n convey rollers in a lower space of the scum box. A space located at the kth position from an upstream side to a downstream side in a conveying direction of the glass ribbon among n+1 spaces divided by the carbon member in the conveying direction of the glass ribbon is defined as a kth space. The float glass manufacturing method includes a process of supplying a non-active gas to a 1st space in the lower space, and a process of supplying a reducing gas to an i-th space (i is a natural number of 2 or more and n or less) in the lower space.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing float glass. Background Technology

[0002] The float glass manufacturing method includes the following steps: forming a glass ribbon onto molten metal stored in a float furnace; pulling the formed glass ribbon out of the float furnace using multiple conveying rollers located inside a slag box; and feeding it into a slow-cooling furnace. The float glass manufacturing method also includes the following steps: slowly cooling the glass ribbon inside the slow-cooling furnace; and then cutting it into the desired size and shape. Float glass is obtained by cutting the glass ribbon.

[0003] To suppress the oxidation of the molten metal, the interior of the flotation kiln is filled with reducing gas. Conversely, the interior of the slow-cooling furnace is filled with atmospheric air flowing in from its outlet. As a result, reducing gas flows from the interior of the flotation kiln into the interior of the slag box, while atmospheric air flows from the interior of the slow-cooling furnace into the interior of the slag box. Atmosphere also flows into the interior of the slag box through openings formed in the outer wall of the slag box (e.g., holes for inserting conveyor rollers) or through gaps between the slag box and the slow-cooling furnace.

[0004] The float glass manufacturing method includes the following steps: Inside the scum tank, a carbon component is brought into contact with the conveyor rollers to remove foreign matter adhering to them. This foreign matter includes, for example, oxides formed by the oxidation of molten metal carried into the scum tank along with the glass ribbon, known as scum. When air flows into the scum tank, the oxygen in the atmosphere causes the carbon component to oxidize and be consumed, making scum removal difficult. As a result, damage occurs on the lower surface of the glass ribbon. Furthermore, when air flows into the scum tank, it causes the molten metal adhering to the lower surface of the glass ribbon to oxidize, thus generating scum defects.

[0005] Patent Document 1 discloses a technique for using an atmosphere separation device to suppress the inflow of atmospheric air from the interior of a slow-cooling furnace into the interior of a scum box. The atmosphere separation device has a separation member and a lifting mechanism for moving the separation member vertically. The separation member separates a space lower than the transport path of the glass ribbon transported in the scum box and a space lower than the transport path in the slow-cooling furnace.

[0006] Patent document 2 discloses the following technology: using a gas flow forming mechanism and using a non-oxidizing gas to seal the removal component that removes molten tin adhering to the conveying roller.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-050160

[0010] Patent Document 2: Japanese Patent Application Publication No. 2011-132099 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] According to Patent Document 1, although it is possible to suppress the inflow of air from the interior of the slow-cooling furnace into the interior of the scum box, air can sometimes flow into the interior of the scum box through holes formed in the outer wall of the scum box (e.g., holes for inserting conveyor rollers) or through gaps between the scum box and the slow-cooling furnace. Therefore, the technology described in Patent Document 1 cannot sufficiently suppress the inflow of air into the interior of the scum box. Consequently, it cannot sufficiently suppress the oxidation and consumption of carbon components due to oxygen in the atmosphere. Furthermore, it cannot sufficiently reduce scum defects generated on the lower surface of the glass belt.

[0013] The scum box contains an upper space above the glass strip G and a lower space below the glass strip G. Reducing gas flows into the upper space of the scum box from inside the flotation furnace. Sometimes the flowing reducing gas flows around the glass strip from above to below, and sometimes it flows counter-currently from the lower space of the scum box into the interior of the flotation furnace. When the counter-current reducing gas is supplied between the lower surface of the glass strip and the upper surface of the molten metal, the molten metal is easily carried into the interior of the scum box along with the glass strip, leading to an increase in scum defects on the lower surface of the glass strip.

[0014] According to Patent Document 2, although it is possible to prevent deterioration caused by oxidation of the removed components, the quality of float glass is reduced due to oxidation of tin adhering to the surface of the conveyor roller or oxidation of tin adhering to the surface of the glass strip during transport using the conveyor roller.

[0015] One aspect of this disclosure provides a technique for suppressing the formation of scum defects while simultaneously suppressing the oxidative consumption of carbon components.

[0016] means for solving problems

[0017] One aspect of the float glass manufacturing method disclosed herein includes the following steps: a glass ribbon, formed on molten metal stored in a float casting furnace, is pulled out from the float casting furnace and fed into a slow cooling furnace using n (n is a natural number of 2 or more) conveying rollers disposed inside a slag box. The float glass manufacturing method further includes the step of contacting a carbon component with each of the n conveying rollers inside the slag box and in a lower space below the glass ribbon. The space located at the k-th position from upstream to downstream in the conveying direction is defined as the k-th space, which is one of the n+1 spaces into which the lower space is divided by the carbon component in the conveying direction of the glass ribbon. The float glass manufacturing method further includes the steps of supplying an inert gas to the first space in the lower space and supplying a reducing gas to the i-th space in the lower space (i is a natural number of 2 or more and less than n).

[0018] Invention Effects

[0019] According to one aspect of this disclosure, by supplying an inactive gas to the upstream first space, the pressure of the first space can be increased, and atmospheric inflow into the first space can be suppressed. Furthermore, by supplying an inactive gas to the upstream first space, reducing gases can be prevented from circulating into the first space from the space directly above it, while simultaneously reducing the concentration of reducing gases in the first space and preventing the backflow of reducing gases from the first space into the interior of the flotation kiln. Moreover, by supplying a reducing gas to the i-th space, the pressure of the i-th space can be increased, and atmospheric inflow into the i-th space can be suppressed. Additionally, by supplying a reducing gas to the i-th space, oxygen in the atmosphere that has already flowed into the i-th space can be converted into water vapor, etc., thus suppressing oxidation caused by oxygen. As a result, the generation of scum defects can be suppressed while the oxidation and consumption of carbon components can be suppressed. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of a float glass manufacturing apparatus according to one embodiment.

[0021] Figure 2 To enlarge the representation Figure 1 A cross-sectional view of the scum box.

[0022] Figure 3 A cross-sectional view of the scum box in the first modified example, shown in enlarged form.

[0023] Figure 4 To indicate the configuration in Figure 3 A perspective view of the nozzle in the second space shown.

[0024] Figure 5 A perspective view showing the nozzle of the second modified example.

[0025] Figure 6 A perspective view showing the nozzle of the third modified example.

[0026] Label Explanation

[0027] 1. Float glass manufacturing equipment

[0028] 2. Floating Kiln

[0029] 3 scum tank

[0030] 31 Conveying Rollers

[0031] 32 Carbon components

[0032] 5. Slow-cooling furnace

[0033] M Molten Metal

[0034] G glass ribbon Detailed Implementation

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that in the drawings, sometimes the same or corresponding structures are labeled with the same symbols and their descriptions are omitted. In the drawings, the X-axis, Y-axis, and Z-axis are mutually perpendicular directions; the X-axis and Y-axis are horizontal directions; and the Z-axis is a vertical direction. The X-axis is the transport direction of the glass strip G, and the Y-axis is the width direction of the glass strip G. In the specification, the "~" indicating a numerical range indicates that the values ​​described before and after it are the lower and upper limits.

[0036] Reference Figure 1 An embodiment of a float glass manufacturing apparatus 1 will be described. The float glass manufacturing apparatus 1 includes a float polishing furnace 2, a slag box 3, and a slow cooling furnace 5, located upstream to downstream of the glass strip G. The float glass manufacturing apparatus 1 forms a glass strip G on molten metal M stored in the float polishing furnace 2. The formed glass strip G is pulled out of the float polishing furnace 2 by multiple conveying rollers 31 provided inside the slag box 3 and sent to the slow cooling furnace 5. Furthermore, the float glass manufacturing apparatus 1 slowly cools the glass strip G inside the slow cooling furnace 5 and then cuts it into the desired size and shape. Float glass is obtained by cutting the glass strip G.

[0037] Float glass includes, for example, alkali-free glass, aluminosilicate glass, borosilicate glass, or soda-lime glass. Alkali-free glass refers to glass that substantially does not contain alkali metal oxides such as Na₂O and K₂O. Here, "substantially does not contain alkali metal oxides" means that the total content of alkali metal oxides is less than 0.1% by mass.

[0038] There are no particular restrictions on the applications of float glass; for example, it can be used as protective glass for displays (such as liquid crystal displays or organic electroluminescent displays). When float glass is used for protective purposes, it is chemically strengthened glass. Chemically strengthened glass differs from alkali-free glass in that it contains alkali metal oxides.

[0039] For example, based on the mole percent of oxides, chemically strengthened glass contains: SiO2: 62%–68%, Al2O3: 6%–12%, MgO: 7%–13%, Na2O: 9%–17%, K2O: 0%–7%, and the difference obtained by subtracting the Al2O3 content from the total Na2O and K2O content is less than 10%, and in the case of containing ZrO2, its content is less than 0.8%.

[0040] Based on oxide molar percentage, another chemically strengthened glass contains: SiO2: 65%–85%, Al2O3: 3%–15%, Na2O: 5%–15%, K2O: 0%–less than 2%, MgO: 0%–15%, and ZrO2: 0%–1%, and the total content of SiO2 and Al2O3 (SiO2+Al2O3) is less than 88%.

[0041] Based on oxide molar percentages, another type of chemically strengthened glass contains: 50%–75% SiO2, 9%–20% Al2O3, 10%–20% Na2O, 0%–6% K2O, 0%–15% MgO, 0%–10% CaO, SrO and BaO in total (CaO+SrO+BaO), 0%–5% ZrO2 and TiO2 in total (ZrO2+TiO2), 0%–10% B2O3 and 0%–20% Li2O.

[0042] Float glass is used as a substrate for forming thin-film transistors or color filters in displays. When float glass is used as a substrate, it is alkali-free glass. Unlike chemically strengthened glass, alkali-free glass does not contain alkali metal oxides.

[0043] For example, based on oxides by mass%, alkali-free glass contains: SiO2: 50%–73%, Al2O3: 10.5%–24%, B2O3: 0%–12%, MgO: 0%–10%, CaO: 0%–14.5%, SrO: 0%–24%, BaO: 0%–13.5%, MgO+CaO+SrO+BaO: 8%–29.5%, and ZrO2: 0%–5%.

[0044] In the case of having both a high strain point and high melting point, the alkali-free glass preferably contains, in terms of mass percentage based on oxides: SiO2: 58%–66%, Al2O3: 15%–22%, B2O3: 5%–12%, MgO: 0%–8%, CaO: 0%–9%, ​​SrO: 3%–12.5%, BaO: 0%–2%, and MgO+CaO+SrO+BaO: 9%–18%.

[0045] For the desired high strain point, the alkali-free glass preferably contains, in oxide-based mass percent: SiO2: 54%–73%, Al2O3: 10.5%–22.5%, B2O3: 0%–5.5%, MgO: 0%–10%, CaO: 0%–9%, ​​SrO: 0%–16%, BaO: 0%–2.5%, and MgO+CaO+SrO+BaO: 8%–26%.

[0046] The thickness of float glass is selected according to its intended use. When float glass is used as protective glass for displays, its thickness is, for example, 0.1 mm to 2.0 mm. On the other hand, when float glass is used as a glass substrate for displays, its thickness is, for example, 0.1 mm to 0.7 mm.

[0047] Next, we will refer to again Figure 1 One embodiment of the floating polishing furnace 2 will be described. The floating polishing furnace 2 has a bath 21. The bath 21 contains molten metal M. Molten metal M is used, for example, molten tin. In addition to molten tin, molten tin alloys can also be used, and the molten metal M can have a higher density than molten glass. Molten glass is continuously fed onto the molten metal M, and the smooth liquid surface of the molten metal M is used to form a glass strip G in the shape of a strip plate.

[0048] The floating polishing kiln 2 has a roof 22 that forms a space above the bath 21. To prevent oxidation of the molten metal M, the interior of the floating polishing kiln 2 is filled with a reducing gas and maintained at a pressure higher than atmospheric pressure. The reducing gas is, for example, a mixture of nitrogen and hydrogen, containing 85% to 98.5% by volume nitrogen and 1.5% to 15% by volume hydrogen. The reducing gas is supplied from the joints between the bricks of the roof 22 and from the openings in the roof 22.

[0049] The scum box 3 has a conveying roller 31 for lifting the glass belt G. The conveying roller 31 is driven to rotate by a drive device (not shown) such as a motor, and uses its driving force to transport the glass belt G obliquely upward. The drive device is located on the outside of the scum box 3. Therefore, holes for inserting the conveying roller 31 are formed on the outer wall of the scum box 3.

[0050] Inside the scum box 3, multiple conveying rollers 31 are arranged at intervals along the conveying direction (X-axis direction) of the glass belt G. The number of conveying rollers 31 is... Figure 1 There are 3 in total, but more than 2 are acceptable; there can be 2 or more. The axial direction of the conveying roller 31 is the same as the width direction (Y-axis direction) of the glass belt G.

[0051] The scum box 3 has a carbon component 32 that contacts the conveying roller 31. The carbon component 32 is disposed in the lower space of the scum box 3. The lower space of the scum box 3 is the space located below the glass belt G. The carbon component 32 contacts the outer peripheral surface of the conveying roller 31 and removes foreign matter adhering to the outer peripheral surface of the conveying roller 31. Foreign matter includes, for example, oxides obtained by the oxidation of molten metal M brought into the scum box 3 along with the glass belt G, i.e., so-called scum.

[0052] The carbon component 32 is, for example, a cuboid. The carbon component 32 can also be a trapezoidal or inverted trapezoidal quadrangular prism when viewed from the X-axis direction. Multiple carbon components 32 can be arranged axially along the conveyor roller 31. The number of carbon components 32 arranged along each conveyor roller 31 is determined based on the width of the glass belt G (Y-axis dimension) or the axial length of the conveyor roller 31 (Y-axis dimension).

[0053] The Y-axis dimension of the carbon component 32 is, for example, 300mm to 1000mm, preferably 400mm to 800mm. The Z-axis dimension of the carbon component 32 is, for example, 50mm to 200mm, preferably 70mm to 150mm. The X-axis dimension of the carbon component 32 is, for example, 20mm to 100mm, preferably 30mm to 80mm.

[0054] The carbon component 32 may contain graphite powder. The maximum particle size of the graphite powder is, for example, 0.1 mm to 3 mm, preferably 0.5 mm to 2.5 mm. When the maximum particle size of the graphite powder is 0.1 mm to 3 mm, the strength of the carbon component 32, which is a molded body of graphite powder, can be ensured.

[0055] The Shore hardness of the carbon component 32 is, for example, 20HS to 90HS, preferably 30HS to 80HS. When the Shore hardness of the carbon component 32 is 20HS to 90HS, the wear resistance of the carbon component 32 to the conveyor roller 31 can be ensured.

[0056] The scum box 3 may have a force-applying member 33 that presses the carbon component 32 onto the conveying roller 31. The force-applying member 33 may include, for example, a metal spring. The spring is a leaf spring. The force-applying member 33 may include a helical spring, a compression helical spring, a disc spring, a conical helical leaf spring, a ring spring, etc., instead of a leaf spring. It should be noted that the force-applying member 33 may include a fluid pressure cylinder, such as a pneumatic cylinder.

[0057] The scum box 3 may have a support member 34 that supports the carbon component 32 in a liftable manner. The support member 34 is disposed on the bottom wall 35 of the scum box 3. The cross-sectional shape of the support member 34 perpendicular to the Y-axis direction is U-shaped, and the carbon component 32 and the force-applying component 33 are disposed inside the support member 34. The support member 34 prevents the carbon component 32 and the force-applying component 33 from shifting in the X-axis direction.

[0058] To regulate the temperature of the glass strip G, the scum tank 3 may include a heater 37. The heater 37 may be located below the glass strip G. In the scum tank 3, the temperature of the glass strip G is preferably (Tg-50℃) to (Tg+30℃) based on the glass transition temperature Tg of the float glass.

[0059] The scum box 3 has a cover plate 38 located above the glass strip G, an insulating material 39 disposed on the cover plate 38, and a curtain 40 that runs through a portion of the insulating material 39 and the cover plate 38 and hangs down from the lower surface of the cover plate 38. The curtain 40 is a plate-shaped component containing refractory materials such as steel or glass.

[0060] The curtain 40 divides the upper space of the scum box 3 into multiple spaces in the transport direction (X-axis direction) of the glass belt G. The upper space of the scum box 3 is the space located above the glass belt G. The curtain 40 is positioned, for example, directly above the rotation center line of each transport roller 31. The curtain 40 extends in the axial direction (Y-axis direction) of each transport roller 31.

[0061] The slow cooling furnace 5 slowly cools the glass strip G to a temperature below its strain point while it is being transported by conveyor rollers 51. To regulate the temperature of the glass strip G, the slow cooling furnace 5 has heaters (not shown) on its roof and bottom walls. The conveyor rollers 51 are driven to rotate by a drive device (not shown) such as a motor, using their driving force to transport the glass strip G horizontally. The outlet of the slow cooling furnace 5 on its downstream side is open to the outside. Therefore, atmospheric air flows into the interior of the slow cooling furnace 5.

[0062] Incidentally, atmospheric air can flow from the interior of the slow-cooling furnace 5 into the interior of the slag box 3. Atmosphere can also flow into the interior of the slag box 3 through holes (not shown) formed on the outer wall of the slag box 3 (e.g., holes for inserting the conveying roller 31) or through the gap GP between the slag box 3 and the slow-cooling furnace 5.

[0063] Previously, due to atmospheric inflow into the scum box 3, the carbon component 32 was oxidized and consumed by oxygen in the atmosphere, making it difficult to remove the scum adhering to the conveyor roller 31. In addition, previously, when atmospheric inflow into the scum box 3, the molten metal M adhering to the lower surface of the glass belt G was oxidized, resulting in scum defects.

[0064] Additionally, reducing gas can flow from the interior of the float kiln into the upper space of the scum box 3. Previously, the flowing reducing gas sometimes flowed from above the glass belt G to below, and sometimes flowed back into the interior of the float kiln 2 from the lower space of the scum box 3. Due to the backflow of reducing gas, molten metal M is easily carried into the interior of the scum box 3 along with the glass belt G, increasing the scum defects generated on the lower surface of the glass belt G.

[0065] Next, refer to Figure 2 The scum box 3 of one embodiment will be described in detail. Multiple conveying rollers 31, carbon components 32, force-applying components 33, and support components 34 are arranged at intervals along the conveying direction (X-axis direction) of the glass belt G. The axial direction of the conveying rollers 31 is the same as the width direction (Y-axis direction) of the glass belt G.

[0066] The scum box 3 includes a process in its lower space where the carbon component 32 contacts each of the n (n is a natural number greater than 2) conveying rollers 31. n in Figure 2 The value is 3, but it can also be 2, or even 4 or more.

[0067] In this specification, the space located at the k-th position from the upstream side to the downstream side of the lower space of the scum box 3, which is divided into n+1 spaces by carbon component 32 in the transport direction (X-axis direction) of the glass belt G, is defined as the k-th space.

[0068] In addition, in this specification, the conveying roller 31 located at the k-th position from the upstream side to the downstream side in the conveying direction among the n conveying rollers 31 installed inside the scum box 3 is defined as the k-th conveying roller 31-k.

[0069] Furthermore, in this specification, the carbon member 32 that contacts the kth conveying roller 31-k is defined as the kth carbon member 32-k. Additionally, the force-applying member 33 that applies force to the kth carbon member 32-k is defined as the kth force-applying member 33-k. Furthermore, the support member 34 that supports the kth carbon member 32-k is defined as the kth support member 34-k.

[0070] The lower space of the scum box 3 is divided into four spaces S1, S2, S3, and S4 by three conveying rollers 31-1, 31-2, and 31-3. In any two adjacent spaces among the four spaces S1, S2, S3, and S4, gas sometimes flows from one space to the other, and sometimes the gases mix.

[0071] like Figure 2 As shown, when viewed from the Y-axis direction, the first space S1 is surrounded by the upstream wall 41 of the slag box 3 facing the floating kiln 2, the bottom wall 35 of the slag box 3, the first conveying roller 31-1, the first carbon component 32-1 and the first support component 34-1.

[0072] When viewed from the Y-axis direction, the second space S2 is surrounded by the first conveying roller 31-1, the first carbon component 32-1, the first support component 34-1, the bottom wall 35 of the scum box 3, the second conveying roller 31-2, the second carbon component 32-2, and the second support component 34-2.

[0073] When viewed from the Y-axis direction, the third space S3 is surrounded by the second conveying roller 31-2, the second carbon component 32-2, the second support component 34-2, the bottom wall 35 of the scum box 3, the third conveying roller 31-3, the third carbon component 32-3, and the third support component 34-3.

[0074] When viewed from the Y-axis direction, the fourth space S4 is surrounded by the third conveying roller 31-3, the third carbon component 32-3, the third support component 34-3, the bottom wall 35 of the scum box 3, and the downstream wall 42 of the scum box 3 facing the slow cooling furnace 5.

[0075] The scum box 3 has a first nozzle 43 that supplies inactive gas to the first space S1. The first nozzle 43 is inserted into the interior of the scum box 3, for example, from the outer wall of one or both ends in the Y-axis direction, and sprays inactive gas into the first space S1. The spraying direction of the first nozzle 43 is in the Y-axis direction, but it can also be in the positive Z-axis direction (upward direction).

[0076] Space S1 is the upstream space. The inert gas supplied to Space S1 is, for example, nitrogen or a rare gas such as argon. The inert gas supplied to Space S1 may contain nitrogen or a rare gas, or it may be a mixture of nitrogen and a rare gas. No reducing gas is supplied to Space S1.

[0077] According to this embodiment, by supplying an inactive gas into the first space S1, the pressure of the first space S1 can be increased. Therefore, it is possible to suppress the inflow of atmospheric air into the first space S1 through holes in the outer wall of the scum box 3. Therefore, it is possible to suppress the oxidation and consumption of the carbon component 32 due to oxygen in the atmosphere. Furthermore, it is possible to suppress scum defects caused by oxygen in the atmosphere.

[0078] The pressure in the first space S1 is, for example, 1 Pa to 15 Pa higher than atmospheric pressure. If the pressure in the first space S1 is more than 1 Pa higher than atmospheric pressure, it is possible to suppress the inflow of air into the first space S1 from holes in the outer wall of the scum box 3. As a result, the oxidation consumption of the carbon component 32 can be suppressed. In addition, scum defects can be reduced. If the pressure difference between the first space S1 and atmospheric pressure is less than 15 Pa, it is possible to reduce the flow rate of inactive gas supplied to the first space S1.

[0079] Furthermore, according to this embodiment, by supplying an inactive gas into the first space S1, the pressure of the first space S1 can be increased, and the concentration of reducing gas in the first space S1 can be reduced. Therefore, it is possible to suppress the reducing gas from flowing around into the first space S1 from the space directly above it, and simultaneously reduce the concentration of reducing gas in the first space S1. Therefore, it is possible to suppress the backflow of reducing gas from the first space S1 into the interior of the flotation furnace 2, and to suppress the molten metal M from being carried into the interior of the scum box 3 along with the glass belt G. Therefore, it is possible to reduce scum defects generated on the lower surface of the glass belt G.

[0080] The hydrogen concentration in the first space S1 is, for example, less than 5% by volume, preferably less than 3% by volume. If the hydrogen concentration in the first space S1 is less than 5% by volume, then less hydrogen flows back from the first space S1 into the interior of the floating kiln 2. The hydrogen concentration in the first space S1 is, for example, 1% by volume or more, preferably 3% by volume or more.

[0081] The oxygen concentration in the first space S1 is, for example, 100 ppm by volume or less, preferably 10 ppm by volume or less. If the oxygen concentration in the first space is 100 ppm by volume or less, the generation of scum defects can be suppressed, and the oxidation consumption of carbon components 32 can also be suppressed. The oxygen concentration in the first space S1 can be 0 ppm by volume or more.

[0082] The scum box 3 includes a second nozzle 44 that supplies reducing gas to the i-th space (i is a natural number greater than 2 and less than n). The second nozzle 44 supplies reducing gas to all spaces except the upstream first space S1 and the downstream (n+1)-th space (e.g., the fourth space S4). The reducing gas can convert oxygen into water vapor, etc., thereby reducing the oxygen concentration.

[0083] As described above, instead of supplying a reducing gas to the first space S1, an inert gas is supplied. To avoid insufficient reducing gas in the second space S2 adjacent to the first space S1, the second nozzle 44 preferably supplies reducing gas to at least the second space S2. That is, it is preferable that the i-th space at least includes the second space S2. It should be noted that the second nozzle 44 may also supply reducing gas to the third space S3.

[0084] The reducing gas supplied to the i-th space may include, for example, hydrogen, carbon monoxide, or acetylene. Hydrogen, carbon monoxide, and acetylene have excellent reducing properties. It should be noted that the reducing gas supplied to the i-th space may contain hydrogen, or may also contain inactive gases.

[0085] The reducing gas supplied to the i-th space preferably contains 0.1 vol% to 20 vol% hydrogen, more preferably 10 vol% to 20 vol% hydrogen. If the hydrogen concentration is 0.1 vol% or more, it is easy to achieve the effect of reducing oxygen. In addition, if the hydrogen concentration is 20 vol% or less, it is easy to manage the reducing gas.

[0086] The second nozzle 44 is inserted into the interior of the scum box 3 from one or both ends of its outer wall along the Y-axis direction, and sprays reducing gas into the i-th space. Figure 2 The image shows the Y-axis direction, or it can be shown as follows: Figure 3 and Figure 4 The diagram shows the positive Z-axis direction (upward direction).

[0087] like Figure 3 and Figure 4 As shown, the second nozzle 44 may, for example, comprise a horizontal tube 441 extending along the Y-axis and a vertical tube 442 extending upward through a slit (not shown) formed along the horizontal tube 441. The horizontal tube 441 is inserted into a hole in the outer wall of the scum box 3 at one end along the Y-axis. The vertical tube 442 opens upward and ejects reducing gas upward. Figure 4 and Figure 5 As shown, there are no particular restrictions on the Y-axis dimension of the vertical tube 442. The vertical tube 442 can be configured at one or both ends of the Y-axis direction in the i-th space, or it can be configured in the entire Y-axis direction of the i-th space.

[0088] like Figure 6 As shown, the second nozzle 44 may include a horizontal tube 441 extending along the Y-axis and ejection holes 443 formed on the horizontal tube 441. Multiple ejection holes 443 may be spaced apart along the Y-axis. The ejection holes 443 may be configured at only one or both ends of the i-th space along the Y-axis, or they may be configured along the entire Y-axis of the i-th space. The ejection holes 443 open upwards and eject reducing gas upwards.

[0089] like Figure 3 As shown, the second nozzle 44 can spray reducing gas towards the upstream conveying roller 31 (e.g., the first conveying roller 31-1). An airflow is generated near the outer peripheral surface of the first conveying roller 31-1 in the direction of rotation of the first conveying roller 31-1. This airflow allows the reducing gas to be supplied to the first carbon component 32-1, thereby effectively reducing the oxygen concentration near the first carbon component 32-1.

[0090] According to this embodiment, by supplying a reducing gas to the i-th space, the pressure of the i-th space can be increased. Therefore, it is possible to suppress the inflow of atmospheric air into the i-th space through holes in the outer wall of the scum box 3. Thus, it is possible to suppress the oxidation and consumption of the carbon component 32 due to oxygen in the atmosphere. Furthermore, it is possible to suppress scum defects caused by oxygen in the atmosphere.

[0091] The pressure in the i-th space is, for example, 1 Pa to 15 Pa higher than atmospheric pressure. If the pressure in the i-th space is more than 1 Pa higher than atmospheric pressure, it is possible to suppress the inflow of air into the i-th space from holes in the outer wall of the scum box 3. As a result, the oxidation consumption of the carbon component 32 can be suppressed. In addition, scum defects can be reduced. If the pressure difference between the i-th space and atmospheric pressure is less than 15 Pa, it is possible to reduce the flow rate of reducing gas supplied to the i-th space.

[0092] Furthermore, according to this embodiment, by supplying a reducing gas to the i-th space, the oxygen flowing into the i-th space can be converted into water vapor or the like, and oxidation caused by oxygen can be suppressed. Therefore, the oxidation consumption of the carbon component 32 can be suppressed. In addition, the generation of scum defects can be suppressed.

[0093] The hydrogen concentration in the i-th space is, for example, 1% to 20% by volume, preferably 2% to 10% by volume. If the hydrogen concentration in the i-th space is 1% by volume or more, the oxygen in the atmosphere flowing into the i-th space is easily reduced. On the other hand, if the hydrogen concentration in the i-th space is 20% by volume or less, the management of the reducing gas supplied to the i-th space is easy.

[0094] The oxygen concentration in the i-th space is, for example, 100 ppm by volume or less, preferably 50 ppm by volume or less. If the oxygen concentration in the i-th space is 100 ppm by volume or less, it is possible to suppress the formation of scum defects while also suppressing the oxidation consumption of the carbon component 32. The oxygen concentration in the i-th space can be 0 ppm by volume or more.

[0095] The (n+1)th space is the downstream space, for example, the fourth space S4. The reducing gas supplied to the (n+1)th space includes, for example, hydrogen, carbon monoxide, or acetylene, and may also contain inert gases. In addition, the inert gas supplied to the (n+1)th space is, for example, nitrogen or a rare gas such as argon.

[0096] According to this embodiment, by supplying an inactive gas or a reducing gas to the (n+1)th space, the pressure of the (n+1)th space can be increased. Therefore, it is possible to suppress the inflow of atmospheric air into the (n+1)th space through holes in the outer wall of the scum box 3. Therefore, it is possible to suppress the oxidation and consumption of the carbon component 32 due to oxygen in the atmosphere. Furthermore, it is possible to suppress scum defects caused by oxygen in the atmosphere.

[0097] The pressure in the (n+1) space is, for example, 1 Pa to 15 Pa higher than atmospheric pressure. If the pressure in the (n+1) space is more than 1 Pa higher than atmospheric pressure, it is possible to suppress the inflow of air from the gap GP between the scum box 3 and the slow cooling furnace 5 into the (n+1) space. As a result, the oxidation consumption of the carbon component 32 can be suppressed. In addition, scum defects can be reduced. If the pressure difference between the (n+1) space and atmospheric pressure is less than 15 Pa, it is possible to reduce the flow rate of gas supplied to the (n+1) space.

[0098] The hydrogen concentration in the (n+1) space is, for example, 1% to 20% by volume, preferably 2% to 10% by volume. If the hydrogen concentration in the (n+1) space is 1% by volume or more, the oxygen in the atmosphere flowing into the (n+1) space is easily reduced. On the other hand, if the hydrogen concentration in the (n+1) space is 20% by volume or less, the management of the reducing gas supplied to the (n+1) space is easier.

[0099] The oxygen concentration in the (n+1)th space is, for example, 100 ppm by volume or less, preferably 50 ppm by volume or less. If the oxygen concentration in the (n+1)th space is 100 ppm by volume or less, the oxidation consumption of the carbon component 32 can be suppressed while suppressing the generation of scum defects. The oxygen concentration in the (n+1)th space can be 0 ppm by volume or more.

[0100] [Example]

[0101] The experimental data are described below. Example 1 is a comparative example, and Example 2 is an exemplary example. In Examples 1 and 2, the experimental data were... Figure 3 The scum tank 3 shown was used to manufacture float glass under the conditions shown in Table 1. In Example 1, no hydrogen-containing gas was supplied to the second space S2; in contrast, in Example 2, hydrogen-containing gas was supplied to the second space S2. Otherwise, float glass was manufactured under the same conditions in Examples 1 and 2. The hydrogen-containing gas used was a gas containing 12% by volume hydrogen and 88% by volume nitrogen.

[0102] Table 1

[0103]

[0104] As shown in Table 1, in Example 1, no gas containing hydrogen was supplied to the second space S2. In contrast, in Example 2, gas containing hydrogen was supplied to the second space S2. Otherwise, float glass was manufactured under the same conditions in Examples 1 and 2.

[0105] In Table 1, the hydrogen concentration in the second space S2 is the same in Examples 1 and 2 because the supply of hydrogen-containing gas is carried out in the center of the Y-axis direction of the scum box 3, while the hydrogen concentration is measured at one end of the Y-axis direction of the scum box 3.

[0106] However, as shown in Table 1, in Example 2, because a hydrogen-containing gas was supplied to the second space S2, the pressure in the second space S2 increased compared to Example 1. Furthermore, in Example 2, because a hydrogen-containing gas was supplied to the second space S2, the hydrogen concentration in the third space S3 increased compared to Example 1 due to the infiltration of the hydrogen-containing gas.

[0107] In Examples 1 and 2, the end faces of the float glass were illuminated in a dark room to examine the surfaces of the float glass in contact with the molten metal M, and the number of dross defects with a major diameter greater than 20 μm per unit area was investigated. The investigated numbers are shown as relative values ​​in Table 1. Table 1 shows that in Example 2, N2 gas was supplied to the first space S1 and a gas containing hydrogen was supplied to the second space S2, thus reducing the number of dross defects compared to Example 1.

[0108] Furthermore, in Examples 1 and 2, float glass was continuously manufactured for 50 days under the conditions shown in Table 1, and the oxidation consumption of carbon component 32 was visually inspected during these 50 days. In Table 1, an evaluation of carbon component 32 marked with "○" indicates no visual oxidation consumption, while an evaluation of carbon component 32 marked with "×" indicates visual oxidation consumption. As can be seen from Table 1, in Example 2, N2 gas was supplied to the first space S1 and a gas containing hydrogen was supplied to the second space S2; therefore, compared to Example 1, the oxidation consumption of carbon component 32 was suppressed.

[0109] The method for manufacturing float glass according to this disclosure has been described above, but the present invention is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations can be made within the scope of the claims. These, of course, also fall within the technical scope of this disclosure.

Claims

1. A method for manufacturing float glass, the method comprising the following steps: using n conveying rollers disposed inside a slag box to pull a glass strip formed on molten metal stored in a float polishing furnace from the float polishing furnace and send it to a slow cooling furnace, wherein n is a natural number greater than or equal to 2, wherein... The float glass manufacturing method includes: The process of bringing the carbon component into contact with each of the n conveying rollers inside the scum box and in the lower space below the glass belt, and... When the space located at the k-th position from the upstream to the downstream side of the transport direction of the glass ribbon is defined as the k-th space among the n+1 spaces into which the lower space is divided by the carbon component in the transport direction of the glass ribbon, The float glass manufacturing method includes: The process of supplying inactive gas to the first space in the lower space, and The process of supplying reducing gas to the i-th space in the lower space, where i is a natural number greater than 2 and less than n. The float glass manufacturing method includes a step of supplying a reducing gas to the transport roller on the upstream side of the transport direction in the i-th space.

2. The float glass manufacturing method as described in claim 1, wherein, In the process of supplying reducing gas to the i-th space in the lower space, reducing gas is supplied to at least the second space in the lower space, where i is a natural number of 2 or more and n or less.

3. The float glass manufacturing method as described in claim 1 or 2, wherein, The float glass manufacturing method includes the step of supplying an inactive gas or a reducing gas to the (n+1)th space in the lower space.

4. The float glass manufacturing method as described in claim 1 or 2, wherein, The reducing gas supplied to the i-th space contains hydrogen, carbon monoxide, or acetylene.

5. The method for manufacturing float glass as described in claim 1 or 2, wherein, The reducing gas supplied to the i-th space contains 0.1% to 20% hydrogen by volume.

6. The method for manufacturing float glass as described in claim 1 or 2, wherein, The hydrogen concentration in the first space is less than 3% of the volume.

7. The method for manufacturing float glass as described in claim 1 or 2, wherein, The hydrogen concentration in the i-th space is 1% to 20% by volume.

8. The method for manufacturing float glass as described in claim 1 or 2, wherein, The pressure in the i-th space is 1 Pa to 15 Pa higher than atmospheric pressure.

9. The method for manufacturing float glass as described in claim 1 or 2, wherein, The oxygen concentration in the i-th space is below 100 ppm by volume.

Images