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
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/033—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by using resistance heaters above or in the glass bath, i.e. by indirect resistance heating
• • 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
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/021—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by induction heating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2211/00—Heating processes for glass melting in glass melting furnaces
  • C03B2211/70—Skull melting, i.e. melting or refining in cooled wall crucibles or within solidified glass crust, e.g. in continuous walled vessels
• • 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
  • C03B5/42—Details of construction of furnace walls, e.g. to prevent corrosion; Use of materials for furnace walls
  • C03B5/44—Cooling arrangements for furnace walls
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/24—Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders
• • 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 invention relates to an apparatus and a method for melting glass materials by high frequency induction heating. More particularly, the present invention relates to an apparatus in which high frequency induction heating is conducted to safely melt glass materials including ZnO, P O , and/or Bi O , which are useful substitutes for environmentally harmful heavy metals, such as PbO, but show an etching elution property upon low temperature melting. Also, the present invention is concerned with a method for melting such glass materials using the apparatus.
• metal oxide compositions comprising ZnO, P O , and/or Bi O , which are similar in function and role to PbO, should maintain the composition designs throughout vitrification processes, even when they are processed into powder or melt, without the occurrence of compositional change. It is very important to develop a technology to accomplish this.
• an object of the present invention is to provide an apparatus and a method for producing a glass melt having a composition comprising a metal oxide selected from among ZnO, P O , Bi O , and combinations thereof.
• Another object of the present invention is to provide a glass melting apparatus and method by which impurities resulting from the reaction of a glass material composition with components of a melting furnace and/or from the etching of glass materials are prevented from being incorporated into the glass melt.
• a method for producing a glass melt comprising the steps of: feeding part of a predetermined total amount of a composition of glass materials into a melting furnace, said glass materials including a metal oxide selected from a group consisting of ZnO, P O 5 Bi O , and combinations thereof; placing one or more carbon rings for ignition on the glass materials; adding the remaining amount of the glass materials to cover the carbon rings; melting the glass materials by applying a high frequency induction current to the melting furnace; and discharging a glass melt from the melting furnace, the glass melt resulting from the melting of the glass materials.
• the melting step is conducted while oxygen or air is supplied to generate bubbles within the melting furnace so as to homogeneously mix components of the glass melt.
• the melting step is conducted while amount ratios between the glass materials are controlled in response to a signal from a high- temperature viscometer monitoring the viscosity of the glass melt, so as to allow the glass melt to have a constant viscosity.
• the melting step is conducted while amount ratios between the glass materials are controlled in response to a signal from a device monitoring a change in the composition of glass materials, so as to allow the glass melt to have a constant composition.
• the melting step is conducted while the temperature of the melting furnace is controlled in response to a signal from a temperature sensor monitoring the temperature of the glass melt so as to maintain the temperature of the glass melt constant.
• a glass melting apparatus comprising: a melting furnace with an induction coil wound around the outer wall thereof, said induction coil serving as a path through which an electric current flows to cause high frequency induction heating, thereby melting glass materials; a material feeder for feeding glass materials into the melting furnace; a gas outlet for discharging the gas generated within the melting furnace therethrough; a glass melt outlet for discharging a glass melt, resulting from the melting of the glass materials, from the melting furnace; a heater, installed at a periphery of the glass melt outlet, for heating the glass melt outlet so as to discharge the glass melt without hardening it during passage through the glass melt outlet; and a high frequency controller for controlling the high frequency induction current generated through the induction coil, wherein the melting furnace has an inner wall 14a and an outer wall 14b with a water path interposed therebetween, so that cooling water is allowed to flow along the path to form a glass coat on the inner wall of the melting furnace when melting the glass materials, thereby
• the glass melt obtained therefrom has no impurities.
• a resistance heating process is conducted to melt the glass materials in a ceramic or metal container.
• such a conventional process suffers from the disadvantage of incorporating a large quantity of impurities, resulting from the reaction or etching of the metal oxides to the wall of the furnace, into the glass melt.
• the present invention employs a high-frequency induction heating process in which glass materials, instead of the melting furnace, are heated.
• cooling water is allowed to flow along a path provided between an inner wall and an outer wall of the melting furnace to form a glass coat on the inner wall, thereby preventing not only the erosion of the inner wall of the melting furnace, but also the incorporation of the glass melt with impurities eroded from the melting furnace.
• a glass composition comprising a metal oxide selected from ZnO, P 2O 5 5 Bi 2O 3 and combinations thereof, instead of harmful heavy oxides, such as PbO, can be melted to form a glass melt substantially free of impurities.
• this glass melt produced according to the present invention can be used as a material or a component for flat display electronic products. Because impurities are not incorporated, the glass melt has almost the same composition as was designed initially, and is suitable for use in such high- value added products.
• the present invention provides a way to overcome various environmental legislation that is to be enacted, including ROHS and WEEE, which are going to come into force on 1 July, 2006, and in 2007, respectively, and will prohibit the use of harzardous heavy metals, such as PbO. That is, ZnO, P O , and/or Bi O , instead of
• the glass melt produced in accordance with the apparatus and method of the present invention can be used as a material for glass structures which are required to exhibit hardness, low-temperature melting points, and thermal resistance as well as micro-structural properties.
• the glass melt produced according to the present invention has optical and structural properties, such as transparency and homogeneity, satisfying the requirements for low-temperature melting, thermal resistance, and high hardness, as well as amorphous properties, that is, it is suitable for use in PDP barrier ribs, frits, fillers, and sealings.
• the present invention can bring about a great improvement in the compositional reliability of glass melt, thereby making it easy to design quality glass melts having desired properties. Further, the glass melts can be produced at low cost.
• FIG. 1 is a schematic view showing an apparatus for melting glass materials using high-frequency induction heating
• FIG. 2 is an X-ray diffractogram of the glass produced using the apparatus and method for melting glass materials using high-frequency induction heating of the present invention.
• FIG. 3 shows glass melting processes according to Example 2.
• FIG. 1 an apparatus for melting glass using high frequency induction heating is shown in accordance with an embodiment of the present invention.
• a glass melting furnace 14 is provided for melting starting materials of a glass melt and is preferably cylindrical and made from a stainless material.
• An induction coil 22 is wound around the melting furnace 14. When an electric current flows through the induction coil 22, high frequency induction heating occurs to melt the starting materials.
• the high frequency inducing current is under the control of a high frequency controller (not shown) connected to the induction coil.
• the material feeder 10 is equipped with storage and measurement hoppers 12 for respective glass materials.
• a window 18 is provided to monitor therethrough the molten status of the glass materials with the naked eye.
• the vitrification process occurring within the melting furnace can be continuously viewed through the window 18.
• the window 18 functions as an inlet through which carbon rings for ignition are fed into the melting furnace.
• the carbon rings serve as an ignition initiator in heating the glass materials at an early stage.
• the melting furnace has an outlet 16 for discharging therethrough the gas generated within the furnace.
• the melting furnace is divided into an upper part and a lower part.
• the glass materials start to melt and the resulting glass melt has a temperature of l,050°C or higher and preferably, a temperature from 1,050 to l,100°C.
• the glass materials including ZnO, P O and/or Bi O can melt around a temperature as low as 800°C.
• the glass melt ranges in electrical conductivity from 0.1 to 0.3 ohm "1 at around 800°C, but the electrical conductivity of the glass melt increases about four to five fold at l,050°C or higher. Accordingly, the increased electrical conductivity improves the distribution and density of induction current over the melt, leading to a rapid increase in heating efficiency.
• the glass materials which are low in vapor pressure, readily vaporize to cause a compositional change.
• the glass melt is preferably heated at 1,050 to l,100°C.
• the glass melt having such a high temperature is apt to fuse the wall of the melting furnace.
• the melting furnace 14 has an inner wall 14a and an outer wall 14b with cooling water flowing therebetween.
• the cooling effect forms a glass coat on the inner wall of the melting furnace when melting the glass materials.
• cooling water is allowed to flow along a path provided between the inner wall 14a and the outer wall 14b, and is then discharged through a water outlet 26 provided at an upper portion of the melting furnace.
• the inner wall has a constant temperature of 70 to 80°C at its surface, which allows the formation of a glass coat 50 thereon.
• the glass coat 50 prevents not only the erosion of the inner wall of the melting furnace, but also the incorporation of the glass melt with impurities eroded from the melting furnace.
• a temperature sensor (not shown) is provided for monitoring the temperature of the glass melt.
• the high frequency controller functions to control induction currents thereby maintaining the temperature of the glass melt constant.
• the glass melt is required to have a viscosity of 0.5-1.0x10 poise in order to produce quality glass products.
• the melting furnace is equipped with a high-temperature viscometer (not shown). If the glass melt is measured to have too high a viscosity, a trace amount of B O and/or Na O is further added. On the other hand, if the glass melt is measured to have too low a viscosity, a trace amount of SiO is further added.
• the glass materials or the glass melt are stirred to mix the components thereof well.
• An air inlet 28 is provided at a lower portion of the melting furnace for oxygen or air introduction. With the aid of an external bubbler (not shown), oxygen or air is introduced into the melting furnace so that the components of the glass melt are mixed sufficiently.
• a ring heater 32 is installed at a periphery of the glass melt outlet 34 so that the glass melt is discharged without being hardened during passage through the outlet 34.
• the composition of the starting materials includes at least one metal oxide selected from a consisting of ZnO, P O , and Bi O .
• the composition is called a zinc based composition when comprising ZnO as a major component, a phosphate based composition when comprising P O as a major component, and a bismuth based composition when comprising Bi O as a major component.
• These metal oxides are not mutually exclusive. That is, two or more components may be used simultaneously. For example, ZnO and P O may be used together in the composition.
• B O and CaO may be used as main components of each of the compositions.
• Table 1 below shows an example of compositions of the glass materials suitable for use in the present invention. These compositions exhibit similar characteristics in regard to manufacturing processes, including baking temperature, thermal expansion and shrinkage, etc.
• glass materials After being weighed and mixed, glass materials are loaded into respective hoppers from which they are fed into the melting furnace. Initially, only 3/4 by weight of the amount of each glass material is added.
• a carbon ring for ignition is introduced in the melting furnace through the window as descried above.
• the carbon ring used in the present invention may be, for example, 30 to 40 cm in diameter and may be placed within the glass materials at a height of 15 to 20 cm from the bottom of the melting furnace.
• the carbon ring plays an important role as an igniter for generating the heat necessary for melting the glass materials. As heat induction is generated by the coil, the carbon ring starts to melt, thereby melting adjacent glass materials. Even after the carbon ring melts up, the glass materials continue to be melted by the high frequency induction heating of the external induction coil.
• a titan ring may be used instead of a carbon ring.
• titanium or titanium alloy remains in the final glass melt, which thus differs from the desired composition.
• carbon is exhausted in a gaseous form of CO or CO at l,000°C or higher, thereby having no influence on the composition of the final glass melt product.
• the present invention has the ultimate goal of leading the glass materials to stable vitrification.
• the electrical current induced through the inductor around the melting furnace is applied to the contents of the melting furnace. Under this condition, electrical resistance occurs at the carbon ring to generate thermal energy, resulting in ignition of the carbon ring. As the carbon ring is fired, the glass materials adjacent to the carbon ring start to melt. The initial ignition of the carbon ring can be viewed through the window. At this time, a decrease in the external voltage applied to the melting furnace also occurs, along with a rapid increase in the current. Afterwards, an induced current is generated in the glass materials as well, so that the glass material remains molten. The initial ignition of the glass materials depends substantially on the composition thereof.
• the properties of the composition are very important.
• a composition of glass materials can be readily ignited at a temperature from 1,050 to l,100°C when it ranges in viscosity from 0.5 to 1.0x10 poise and has an electrical conductivity of 0.3 s/cm or less.
• the high frequency controller regulates induction currents in response to the signal from the temperature sensor to maintain the temperature of the glass melt at 1,050 to l,100°C.
• the glass melt is made to have a viscosity of about 0.5 to 1.0x10 poise by monitoring with a high-temperature viscometer. If the viscosity of the glass melt increases, B O , and/or Na O, out of the glass materials, is added in a trace amount to decrease the viscosity. On the other hand, the viscosity of the glass melt can be increased by the addition of a trace amount of SiO 2.
• composition of the glass melt is monitored in real time with a composition measuring device so as to adjust the changed composition of the glass materials to the initial composition. Meanwhile, oxygen and air are supplied to generate bubbles, thereby homogeneously mixing the components of the glass melt.
• the glass melt is discharged through the outlet 34 provided at a lower portion of the melting furnace.
• a composition of fresh glass material the same as the initial composition is fed in an amount as much as the amount of discharged glass melt, so that the glass melt can be produced continuously and stably.
• the amount of fresh glass materials to be added is determined in real time according to the monitoring of the change in viscosity and composition. That is, before being fed into the furnace, a batch of glass materials must be calculated with regard to the addition amount. If the glass materials fail to be controlled, the operation of the apparatus may be ceased as the melt drastically increases in viscosity. Mode for the Invention
• FIG. 2 is an X-ray diffractogram of the glass produced through this experiment. As shown in the figure, the diffraction pattern is characteristic of glass, demonstrating that excellent vitrification of the glass materials was achieved according to the present invention.
• EXAMPLE 2 Used in this example was a glass composition that was able to be baked as a candidate for use in PDP barrier ribs at as low as about 500°C upon the formation of barrier ribs, and had a coefficient of thermal expansion of around 70x10 .
• the glass melt was pulverized into a powder using a zirconia mortar. From the powder, an X-ray diffractogram similar to that of FlG. 2 was obtained, demonstrating that the melt was typical of glass.
• COMPARATIVE EXAMPLE [84] Using a 99.7% Al O container, a glass melt was produced in a low-temperature heating manner from the same amount and composition of starting materials as in Example 1. After pulverization the same as in Example 1, 5g of the powder was analyzed.
• Example 1 and Comparative Example After being uniformly spread on respective carbon tapes, glass samples obtained in Example 1 and Comparative Example were subjected to pre-treatment such as Au coating. Thereafter, the glass samples were analyzed for Al O content (EDS analysis) using a Kevex Sigma EDX spectrometer.
• EDS analysis Al O content
• the present invention is different in melting apparatus and method from conventional technologies. That is, the melting apparatus of the present invention is operated according to induction heating process, unlike gas combustion or resistance heating processes. Also, a batch of the glass composition used in the present invention cannot be processed into a desired glass melt in conventional induction furnaces due to high insulation properties. However, a glass melt can be manufactured from the composition, with no serious change in composition, according to the melting apparatus and method of the present invention.
• High frequency induction heating furnaces such as that employed in the present invention, are known to be generally or commercially applicable to the production of metal melts.
• metal melts can be readily obtained by use of high frequency induction heating furnaces because the high electrical conductivity of metal is suitable for an induction heating process which utilizes the electrical conduction of an object to be heated.
• high frequency induction heating furnaces as are used to produce metal melts are difficult to use in the production of glass melts because of their high insulation properties unless special design features are added thereto.
• a high frequency induction heating furnace was modified with regard to operation conditions including power and frequency and equipped with auxiliary devices, thereby allowing glass materials to be melted.
• the glass melt produced according to the apparatus and method of the present invention has a homogenous composition and shows the structure and state of a transparent or semi-transparent amorphous material both within the furnace and after being quenched, that is, it shows chemical and physical properties as an amorphous material.
• the glass product manufactured according to the method of the present invention can be applied to PDP barrier ribs and has a highly homogeneous and constant composition, thereby assuring the production of quality PDP barrier ribs.

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• Geochemistry & Mineralogy (AREA)
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• 2006
  • 2006-02-21 KR KR1020060016632A patent/KR100700076B1/ko active IP Right Review Request
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