Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/18—Stirring devices; Homogenisation
  • C03B5/182—Stirring devices; Homogenisation by moving the molten glass along fixed elements, e.g. deflectors, weirs, baffle plates
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/18—Stirring devices; Homogenisation
  • C03B5/193—Stirring devices; Homogenisation using gas, e.g. bubblers
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/26—Outlets, e.g. drains, siphons; Overflows, e.g. for supplying the float tank, tweels
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • 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

Definitions

• the present disclosure relates generally to glass melting systems and methods and more specifically to glass melting systems and methods for increased batch dissolution and glass homogeneity.
• Glass materials such those used as flat panel glass for display applications, including LCD televisions and handheld electronic devices, are subject to increasingly stringent requirements for glass quality, especially as the industry continues to move toward increasingly higher display resolutions. In such applications, even small defects in a finished glass sheet may render the entire sheet rejectable. Many of the defects that appear in finished glass can be attributed to incongruities in the glass melt, such as inhomogeneity from insufficient mixing or insufficient dissolution of batch materials.
• Defects such as zirconia stones
• inhomogeneity caused by off composition cords such as sludge (e.g., high zirconia material that settles to the bottom of a glass melt) or scum (e.g., high silica
• the apparatus includes a melting vessel and a mixing vessel located downstream from the melting vessel.
• the mixing vessel includes a plurality of orifices that are configured to introduce gas bubbles into the mixing vessel from a gas source so as to control the degree of mixing of a molten glass stream introduced into the mixing vessel to be above a predetermined level.
• FIG. 1 is a schematic view of an apparatus for producing a glass article including a forming device in accordance with aspects of the disclosure
• FIG. 2 is a schematic view of a portion of an apparatus for producing a glass article that includes a mixing vessel according to embodiments disclosed herein;
• FIG. 3 is a top cutaway view of the bottom of a mixing vessel according to embodiments disclosed herein;
• FIG. 4 is a top cutaway view of the bottom of a mixing vessel according to embodiments disclosed herein;
• FIG. 5 is a schematic view of a glass mixing vessel and connecting tubes, wherein an outlet connecting tube to the gas bubbler includes a static mixer;
• FIG. 6 is a schematic view of a mixing bubbling vessel and connecting tubes, wherein inlet and outlet connecting tubes to the gas bubbler include static mixers;
• FIG. 7 is a perspective view of glass temperature and flows in a mixing vessel, wherein no bubbles are introduced into the mixing vessel from an external gas source;
• FIG. 8 is a perspective view of glass temperature and flows in a mixing vessel according to embodiments disclosed herein, wherein gas bubbles are introduced into the mixing vessel via two rows of orifices that are spaced a relatively shorter distance apart;
• FIG. 9 is a perspective view of glass temperature and flows in a mixing vessel according to embodiments disclosed herein, wherein gas bubbles are introduced into the mixing vessel via two rows of orifices that are spaced a relatively longer distance apart;
• FIG. 10 is a chart showing the mixing index of molten glass in different mixing vessel environments.
• FIG. 1 illustrates an exemplary schematic view of a glass forming apparatus 101 for fusion drawing a glass ribbon 103 for subsequent processing into glass sheets.
• the illustrated glass forming apparatus comprises a fusion draw apparatus although other fusion forming apparatus may be provided in further examples.
• the glass forming apparatus 101 can include a melting vessel (or melting furnace) 105 configured to receive batch material 107 from a storage bin 109.
• the batch material 107 can be introduced by a batch delivery device 111 powered by a motor 113.
• An optional controller 115 can be configured to activate the motor 113 to introduce a desired amount of batch material 107 into the melting vessel 105, as indicated by an arrow 117.
• a glass level probe 119 can be used to measure a glass melt (or molten glass) 121 level within a standpipe 123 and communicate the measured information to the controller 115 by way of a communication line 125.
• the glass forming apparatus 101 can also include a fining vessel 127, such as a fining tube, located downstream from the melting vessel 105 and fluidly coupled to the melting vessel 105 by way of a first connecting tube 129.
• a mixing vessel 131 such as a stir chamber, can also be located downstream from the fining vessel 127 and a delivery vessel 133, such as a bowl, may be located downstream from the mixing vessel 131.
• a second connecting tube 135 can couple the fining vessel 127 to the mixing vessel 131 and a third connecting tube 137 can couple the mixing vessel 131 to the delivery vessel 133.
• a downcomer 139 can be positioned to deliver glass melt 121 from the delivery vessel 133 to an inlet 141 of a forming device 143.
• the melting vessel 105, fining vessel 127, mixing vessel 131, delivery vessel 133, and forming device 143 are examples of glass melt stations that may be located in series along the glass forming apparatus 101.
• the melting vessel 105 is typically made from a refractory material, such as refractory (e.g. ceramic) brick.
• the glass forming apparatus 101 may further include components that are typically made from platinum or platinum-containing metals such as platinum-rhodium, platinum-iridium and combinations thereof, but which may also comprise such refractory metals such as molybdenum, palladium, rhenium, tantalum, titanium, tungsten, ruthenium, osmium, zirconium, and alloys thereof and/or zirconium dioxide.
• the platinum-containing components can include one or more of the first connecting tube 129, the fining vessel 127 (e.g.
• the mixing vessel 145 is in fluid communication with the melting vessel 105 via a mixing vessel inlet tube 129A and is in fluid communication with the fining vessel 127 via a mixing vessel outlet tube 129B.
• Gas (G) is introduced to the bottom of mixing vessel 145 via gas feed 147, which ultimately leads to the formation of gas bubbles 148, which rise in mixing vessel 145.
• Mixing vessel 145 can, in certain exemplary embodiments, also act as a second melting vessel in that it can include active heating components, such as at least one active heating mechanism selected from electrical resistance heating and combustion heating in order to maintain the average temperature of the molten glass within a predetermined range within mixing vessel 145.
• active heating components such as at least one active heating mechanism selected from electrical resistance heating and combustion heating in order to maintain the average temperature of the molten glass within a predetermined range within mixing vessel 145.
• Mixing vessel 145 can, in certain exemplary embodiments, have a volume that is sufficiently large to substantially minimize composition variation of the glass melt leaving the mixing vessel 145 as well as minimize inhomogeneity resulting from insufficient dissolution of batch materials or defects, such as zirconia stones.
• mixing vessel 145 can have a volume that is at least 80% as large as melting vessel 105, such as at least 90% as large as melting vessel, including at least 100% as large as melting vessel, including from 80% to 120% as large as melting vessel.
• FIG. 3 illustrates an exemplary top cutaway view of a bubbling vessel 145 having a plurality of gas feed orifices 146, which allow passage of gas introduced to the bottom of bubbling vessel 145 via gas feed 147.
• gas feed orifices 146 are arranged in two substantially parallel rows of orifices that are arranged a predetermined distance (D) apart from each other.
• the two substantially parallel rows of orifices extend in a direction (E) that is generally perpendicular to the flow direction (F) of the molten glass stream.
• FIG. 4 illustrates an exemplary top cutaway view of a bubbling vessel 145' having a plurality of gas feed orifices 146, which allow passage of gas introduced to the bottom of bubbling vessel 145' via gas feed 147.
• gas feed orifices 146 are arranged in three substantially parallel rows of orifices that are each arranged a predetermined distance (D) apart from each other.
• the three substantially parallel rows of orifices extend in a direction (E) that is generally perpendicular to the flow direction (F) of the molten glass stream.
• bubbling vessel 145' is dimensioned to be longer in the flow direction (F) of the molten glass than in the embodiment illustrated in FIG. 3.
• mixing vessel 145, 145' is shown as having a rectangular shape, it is to be understood that embodiments disclosed herein include those in which mixing vessel may have other shapes, such as a cylindrical shape with a circular or an elliptical cross-section.
• embodiments disclosed herein include those in which mixing vessel may have other shapes, such as a cylindrical shape with a circular or an elliptical cross-section.
• FIGS. 3 and 4 show gas feed orifices 146 arranged in substantially parallel rows, it is to be understood that embodiments disclosed herein include those in which gas feed orifices may be arranged in other patterns such as elliptical patterns, square patterns, rectangular patterns, or patterns having other shapes or configurations.
• FIGS. 3 and 4 show two and three rows of orifices, respectively, it is understood that embodiments herein can include other numbers of rows, such as at least 4 rows, at least 5 rows, and so forth.
• mixing vessel 145, gas feed 147, and gas feed orifices 146 may be operated such that the release of gas into gas feed orifices 146 is timed such that the bubbles are sequentially formed and rise in the bubbling vessel at a
• timing in conjunction with the geometric arrangement of the gas feed orifices 146, can enable an enhanced mixing effect, wherein the drag effect of the bubbles in the gas melt provides a stirring action, which can enhance dissolution of any yet undissolved glass batch materials as well as minimize or eliminate various glass melt inhomogeneities, such as the types of inhomogeneities that can result in cord or knots in the ultimate glass product.
• the average size of the gas bubbles 148 within the glass melt in the mixing vessel 145 may, for example, be at least 2 millimeters in diameter in order to enable sufficient bubble rise under expected mixer height and temperature (glass melt viscosity) conditions, as can be configured by persons of ordinary skill in the art.
• the average size of the gas bubbles 148 may range from about 2 millimeter diameter to about 50 millimeter diameter, such as from about 5 millimeter diameter to about 20 millimeter diameter, and further such as from about 10 millimeter diameter to about 15 millimeter diameter.
• the rate of introduction of gas bubbles 148 into the mixing vessel 145 can depend on a number of factors including, but not limited to, flow rate of the glass melt through the mixing vessel, glass composition, temperature of the mixing vessel, pressure of the mixing vessel, degree of desired mixing effect, and the gas species being introduced, among others.
• introduction of bubbles into the glass melt in mixing vessel 145 may introduce gaseous species into the gas melt that may alter gas chemistry, specifically by adding desirable gasses that facilitate fining and by minimizing or eliminating gases that may be detrimental to fining.
• the introduction of certain gas species in the glass melt in the mixing vessel 145 may lead to the reduction of gases such as SO2, which has high equilibrium pressure in many glass melts, while at the same time, supporting an oxidized fining redox agent, such as tin, so that there is abundant oxidized species that can release O2 when heated in the fining vessel 127.
• the introduction of certain gas species in the glass melt in the mixing vessel 145 may lead to a reduction of gas bubbles that are generated in the fining vessel 127.
• gas (G) introduced to the bottom of mixing vessel 145 may, for example, be selected from at least one of the group consisting of nitrogen, oxygen, air, noble gases (e.g., He, Ne, Ar, Kr, etc.), and mixtures of the same.
• gas (G) introduced into the bottom of the mixing vessel 145 may comprise at least 50mol% nitrogen, such as at least 60mol% nitrogen, including at least 80mol% nitrogen, including from 50 to 100mol% nitrogen, such as from 60 to 90mol% nitrogen.
• Gas (G) introduced into the bottom of the mixing vessel 145 may also comprise mixtures of at least nitrogen and oxygen, such as a mixture comprising at least 50mol% nitrogen and up to 50mol% oxygen, such as mixtures comprising from 50 to 90mol% nitrogen and from 10 to 50 mol% oxygen, including from 60 to 80 mol% nitrogen and from 20 to 40 mol% oxygen.
• Mixing vessel 145 may, for example, comprise a refractory material, such as refractory (e.g. ceramic) brick.
• Mixing vessel inlet tube 129A, and/or mixing vessel outlet tube 129B may be constructed using a high temperature metal, and in particular a high temperature metal that is resistant to oxidation. Suitable metals can be selected, for example, from the platinum group metals, i.e. platinum iridium, rhodium, palladium, osmium and ruthenium. Alloys of the platinum group metals may also be used.
• mixing vessel inlet tube 129A, and/or mixing vessel outlet tube 129B may be constructed from platinum or an alloy of platinum, such as a platinum-rhodium alloy.
• the average temperature of the mixing vessel 145 may in certain embodiments be controlled such that, depending on the glass composition, the average viscosity of the molten glass stream in the mixing vessel ranges from 250 to 500 poise, such as from 300 to 500 poise. Applicants have found that maintaining the viscosity of the molten glass stream in these ranges within the mixing vessel, in combination with mixing vessel configurations and operating conditions disclosed herein, can provide an enhanced mixing effect.
• the average temperature of the mixing vessel 145 is less than the average temperature of the melting vessel 105 and the average temperature of the melting vessel is less than the average temperature of the fining vessel 127.
• the average temperature of the mixing vessel 145 may be at least 25°C less than, including at least 40°C less than, and further including at least 50°C less than the average temperature of the melting vessel 105. In such
• the average temperature of the mixing vessel 145 may, for example, range from about 1540°C to about 1690°C, such as from about 1590°C to about 1640°C while the average temperature of the melting vessel 105 may, for example, range from about 1590°C to about 1740°C, such as from about 1640°C to about 1690°C.
• the average temperatures in the mixing vessel 145 and the melting vessel 105 can be controlled such that, depending on the glass composition, the average viscosity of the molten glass stream in the melting vessel 105 ranges from 200 to 400 poise and the average viscosity of the molten glass stream in the mixing vessel 145 ranges from 300 to 500 poise.
• the average temperature of the melting vessel 105 may be at least 10°C, such as at least 20°C less, and further such as at least 30°C less than the average temperature of the fining vessel 127.
• the average temperature of the melting vessel 105 may, for example, range from about 1590°C to about 1740°C, such as from about 1640°C to about 1690°C while the average temperature of the fining vessel 127 may, for example, range from about 1600°C to about 1750°C, such as from about 1650°C to about 1700°C.
• the average temperatures in the melting vessel 105 and the fining vessel 127 can be controlled such that, depending on the glass
• the average viscosity of the molten glass stream in the melting vessel 105 ranges from 200 to 400 poise and the average viscosity of the molten glass stream in the fining vessel 127 ranges from 150 to 400 poise.
• the average temperature of the mixing vessel outlet tube 129B may be higher than the average temperature of the mixing vessel 145.
• the average temperature of the mixing vessel inlet tube 129A may be lower than the average temperature of the melting vessel 105.
• the average temperature of the mixing vessel outlet tube 129B may be at least 25°C, such as at least 40°C, and further such as at least 50°C higher than the average temperature of the mixing vessel 145, including from 25°C to 75°C higher than the average temperature of the mixing vessel 145.
• the average temperature of the melting vessel 105 may be at least 25°C, such as at least 40°C, and further such as at least 50°C higher than the average temperature of the mixing vessel inlet tube 129A, including from 25°C to 75°C higher than the average temperature of the mixing vessel inlet tube 129A.
• indirect or direct heating methods may, for example, be employed, as known by persons of ordinary skill in the art.
• FIG. 5 illustrates an exemplary schematic view of a glass mixing vessel 145, mixing vessel inlet tube 129A, and mixing vessel outlet tube 129B, wherein outlet tube 129B includes a mixer and, in particular, a static mixer 149B.
• Static mixer 149B can provide a torturous path for glass melt exiting the mixing vessel 145, thereby enabling improved mixing and increased homogeneity of the glass melt and further reducing or eliminating inhomogeneities that can result in cord or knots in the ultimate glass product.
• FIG. 6 illustrates an exemplary schematic view of a glass mixing vessel 145, mixing vessel inlet tube 129A, and mixing vessel outlet tube 129B, wherein inlet tube 129A includes a mixer and, in particular, a static mixer 149 A, and wherein outlet tube 129B includes a mixer and, in particular, a static mixer 149B.
• Static mixers 149A and 149B can provide a torturous path for glass melt entering and exiting the mixing vessel 145, thereby enabling improved mixing and increased homogeneity of the glass melt and further reducing or eliminating inhomogeneities that can result in cord or knots in the ultimate glass product.
• FIGS. 5 and 6 illustrate static mixers
• embodiments disclosed herein also include other types of mixers, such as active mixers, for example, mixers having a rotating blade and shaft wherein the blade may rotate, for example, through operation of motor, such as an electric motor.
• Embodiments disclosed herein also include static mixers having geometries other than shown in FIGS. 5 and 6, such as plates that extend the entire diameter of the inlet and/or outlet tubes and have various patterned openings to allow molten glass flow there through.
• embodiments disclosed herein also include those in which the inlet tube to the mixing vessel includes at least one mixer and the outlet tube to the mixing vessel may not contain at least one mixer (not shown).
• the molten glass As the molten glass is conveyed through the delivery apparatus, it is conditioned by passing it through a fining vessel where a de-gasifi cation process takes place. During the melting process a variety of gases are evolved. If left within the molten glass, these gases can produce bubbles in the finished glass article, such as the glass sheet from the fusion process. To eliminate bubbles from the glass, the temperature of the molten glass is raised in the fining vessel to a temperature greater than the melting temperature. Multivalent compounds included in the batch and present in the molten glass release oxygen during the increase in temperature and aid in sweeping the gases formed during the melting process from the molten glass.
• the gases are released into a vented volume of the fining vessel above a free surface of the molten glass.
• the temperature in the fining vessel can in some cases, for example in the production of glass sheets for the display industry, exceed 1650°C and even exceed 1700°C and approach the melting temperature of the fining vessel wall.
• One method of increasing the temperature in the fining vessel is to develop an electric current in the fining vessel, wherein the temperature is increased via the electrical resistance of the vessel's metal wall.
• Such direct heating may be referred to as Joule heating.
• electrodes also referred to as flanges, are attached to the fining vessel and serve as entrance and exit locations for the electric current.
• FIG. 7 illustrates a perspective view of glass temperature and flows in a mixing vessel 145, wherein no bubbles are introduced into the mixing vessel from an external gas source.
• the tick marks shown in FIG. 7 illustrate predicted molten glass flow direction (line angle) and flow velocity (line length) in the mixing vessel 145.
• the shading shown in FIG. 7 illustrates predicted molten glass temperature regimes in the mixing vessel 145.
• FIG. 8 illustrates a perspective view of glass temperature and flows in a mixing vessel 145 according to embodiments disclosed herein, wherein gas bubbles are introduced into the mixing vessel via two rows of orifices that are spaced a relatively shorter distance apart (as compared to, for example, the embodiment illustrated in FIG. 9). Specifically, gas bubbles are introduced via two substantially parallel rows of six orifices, wherein the distance between the rows of orifices is about 12% of the length of the mixing vessel in the flow direction (F) of the molten glass stream.
• the tick marks shown in FIG. 8 illustrate predicted molten glass flow direction (line angle) and flow velocity (line length) in the mixing vessel 145. As can be seen by comparing FIG. 8 to FIG. 7, the embodiment shown in FIG. 8 results in increased mixing and temperature uniformity relative to the embodiment shown in FIG. 7.
• FIG. 9 illustrates a perspective view of glass temperature and flows in a mixing vessel 145 according to embodiments disclosed herein, wherein gas bubbles are introduced into the mixing vessel via two rows of orifices that are spaced a relatively longer distance apart (as compared to, for example, the embodiment illustrated in FIG. 8). Specifically, gas bubbles are introduced via two substantially parallel rows of six orifices, wherein the distance between the rows of orifices is about 34% of the length of the mixing vessel in the flow direction (F) of the molten glass stream.
• the tick marks shown in FIG. 9 illustrate predicted molten glass flow direction (line angle) and flow velocity (line length) in the mixing vessel 145. As can be seen by comparing FIG. 9 to FIG. 8, the embodiment shown in FIG. 9 results in increased mixing and temperature uniformity relative to the embodiment shown in FIG. 8.
• the degree of mixing within a mixing vessel in accordance with embodiments disclosed herein can be quantitatively approximated by determining a mixing index with the vessel.
• the mixing index is in essence, a summation of the velocities of the glass melt within the mixing vessel and can be calculated as:
• volume n dx n x dy n x dz n
• u, v, and w are molten glass velocity vectors in the x, y, and z directions, respectively.
• FIG. 10 is a chart showing the mixing index of molten glass in different mixing vessel environments, controlled for mixing vessel size, glass composition, temperature, and molten glass flow rate, the difference in the environments being the bubbling configuration in the vessel. With respect to the bubbling configuration in the vessel, four different conditions are presented: (1) no bubbles are introduced into the mixing vessel from an external gas source (similar to FIG.
• bubbles are introduced into the mixing vessel from an external gas source in the form of one row of 6 orifices that is generally perpendicular to the flow direction of the molten glass stream; (3) bubbles are introduced into the mixing vessel from an external gas source in the form of two substantially parallel rows of 6 orifices that are generally perpendicular to the flow direction of the molten glass stream, wherein the distance between the two substantially parallel rows of orifices is about 12% of the length of the mixing vessel in the flow direction of the molten glass stream (similar to the embodiment shown in FIG.
• the embodiments having two substantially parallel rows of orifices correspond to a mixing index of at least 250.
• condition (1) corresponds to a mixing index of 50
• condition (2) corresponds to a mixing index of 195
• condition (3) corresponds to a mixing index of 290
• condition (4) corresponds to a mixing index of 348.
• embodiments disclosed herein can enable mixing indexes of at least 250, such as at least 275, and further such as at least 300, and still yet further such as at least 325, such as from 250 to 350, including from 275 to 325.
• the distance between each of the at least three substantially parallel rows of orifices can be at least 10%, such as at least 20%, and further such as at least 30% of the length of the mixing vessel in the flow direction of the molten glass stream, including from about 10% to about 40% of the length of the mixing vessel, and further including from about 20% to about 40% of the length of the mixing vessel, and still further including from about 30% to about 40% of the length of the mixing vessel in the flow direction of the molten glass stream.
• the distances between each of the substantially parallel rows may be about equal or may be different.
• the average number of orifices in a row may be at least 2, such as at least 3, and further such as at least 4, and yet further such as at least 5, and still yet further such as at least 6, such as from 2 to 20, and further such as from 3 to 10, and yet further such as from 4 to 8, including all ranges and subranges therebetween.
• the distance between the ends of the rows of orifices and a sidewall of the mixing vessel is at least 5%, such as at least 8%, and further such as at least 10% of the width of the mixing vessel.
• the distance between the tops of the orifices and the bottom of the mixing vessel is at least 1%, such as at least 2%, and further such as at least 5% of the height of the mixing vessel. Maintaining these distances can help minimize the potential for erosion on surfaces of the mixing vessel.
• Embodiments disclosed herein may be used with a variety of glass compositions. While not limited, such compositions may, for example, include a glass composition, such as an alkali free glass composition comprising 58-65wt% S1O2, 14-20wt% AI2O 3 , 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO.
• a glass composition such as an alkali free glass composition comprising 58-65wt% S1O2, 14-20wt% AI2O 3 , 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5-2wt% SrO.
• compositions may also include a glass composition, such as an alkali free glass composition, comprising 58-65wt% Si0 2 , 16-22wt% AI2O3, l-5wt% B2O3, l-4wt% MgO, 2-6wt% CaO, l-4wt% SrO, and 5- 10wt% BaO.
• a glass composition such as an alkali free glass composition, comprising 57-61wt% S1O2, 17-21wt% AI2O3, 5-8wt% B2O3, l -5wt% MgO, 3-9wt% CaO, 0-6wt% SrO, and 0-7wt% BaO.
• compositions may additionally include a glass composition, such as an alkali containing glass composition, comprising 55- 72wt% Si0 2 , 12-24wt% AI2O3, 10-18wt% Na 2 0, 0-10wt% B 2 0 3 , 0-5 wt% K 2 0, 0-5 wt% MgO, and 0-5 wt% CaO, which, in certain embodiments, may also include l-5wt% K 2 0 and l-5wt% MgO.
• a glass composition such as an alkali containing glass composition, comprising 55- 72wt% Si0 2 , 12-24wt% AI2O3, 10-18wt% Na 2 0, 0-10wt% B 2 0 3 , 0-5 wt% K 2 0, 0-5 wt% MgO, and 0-5 wt% CaO, which, in certain embodiments, may also include l-5wt% K 2 0 and l-5wt% MgO.
• Embodiments disclosed herein can reduce or eliminate many of the aforementioned defects associated with inhomogeneity resulting from insufficient mixing or insufficient dissolution in a glass melt. For example, by placing a mixing vessel downstream of a melting vessel (wherein mixing vessel may, in certain embodiments, act as a second melting vessel), variation of glass composition as a function of time may be improved. Reducing such variability can, in turn, substantially reduce visible cord or striations in a resulting glass sheet.
• ⁇ pressure drop
• L length of the pipe
• ⁇ dynamic viscosity
• Q volumetric flow rate
• r radius of the pipe. Since temperature and glass level may be tightly controlled, compositional changes tend to otherwise be the largest source of flow variability. Reduction of flow variability can result in improved attributes with respect to, for example, stress, thickness, and wedge.
• Embodiments disclosed herein wherein a mixing vessel is located downstream of a melting vessel and upstream of a fining vessel, can also reduce defects, such as zirconia stones, by enabling increased dissolution of defects prior to the melt stream entering the fining vessel.
• defects such as zirconia stones
• embodiments herein can enable high zirconia glass to be stripped from the stones prior to the glass melt entering the fining vessel.
• Embodiments disclosed herein can further minimize inhomogeneity caused by off composition cords, such as sludge (e.g., high zirconia material that settles to the bottom of a glass melt) or scum (e.g., high silica material that floats at the top of a glass melt) that may cause undesired crystallization or devitrification as the glass melt encounters relatively lower temperature regions of a glass forming apparatus.
• sludge e.g., high zirconia material that settles to the bottom of a glass melt
• scum e.g., high silica material that floats at the top of a glass melt
• embodiments disclosed herein can enable the production of glass sheets having reduced defects, such as blisters, cords, and/or knots.
• embodiments disclosed herein may enable the production of glass sheets having at least a 30% reduction, such as at least a 50% reduction, and further such as at least a 70% reduction of blisters having a length of greater than 300 microns, including the production of glass sheets having at least a 30% reduction, such as at least a 50% reduction, and further such as at least a 70% reduction of blisters having a length of greater than 200 microns, and yet further the production of glass sheets having at least a 30% reduction, such as at least a 50% reduction, and further such as at least a 70% reduction of blisters having a length of greater than 100 microns, including the production of glass sheets having at least a 30% reduction, such as at least a 50% reduction, and further such as at least a 70% reduction of blisters having a length of from 100 to 500 microns, relative to methods that do not include embodiments disclosed herein.

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• 2016
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  • 2016-11-21 CN CN201680068479.XA patent/CN108290761A/zh not_active Withdrawn
  • 2016-11-21 WO PCT/US2016/062989 patent/WO2017091481A1/en active Application Filing
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