Method and apparatus for adding thermal energy to a glass melt

Abstract

Disclosed herein are methods and apparatuses for adding thermal energy to a glass melt. Apparatuses for generating a thermal plasma disclosed herein comprise an electrode, a grounded electrode, a dielectric plasma confinement vessel extending between the two electrodes, and a magnetic field generator extending around the dielectric plasma confinement vessel. Also disclosed herein are methods for fining molten glass comprising generating a thermal plasma using the apparatuses disclosed herein and contacting the molten glass with the thermal plasma. Glass structures produced according to these methods are also disclosed herein.

What is claimed is: 
     
         1 . An apparatus for generating a thermal plasma, comprising:
 an electrode,   a grounded electrode,   a dielectric plasma confinement vessel extending between the electrode and the grounded electrode,   a magnetic field generator extending around the dielectric plasma confinement vessel,   an inlet for delivering a gas into the dielectric plasma confinement vessel,   an RF current source coupled to the electrode and the grounded electrode for converting the gas into a thermal plasma, and   an outlet for delivering the thermal plasma.   
     
     
         2 . The apparatus of  claim 1 , wherein the electrode and the grounded electrode comprise metal rings. 
     
     
         3 . The apparatus of  claim 1 , wherein the inlet comprises a central jet and a peripheral annulus comprising a plurality of jets. 
     
     
         4 . The apparatus of  claim 1 , wherein the RF current generates electric field lines parallel to a direction of gas flow in the dielectric plasma confinement tube and magnetic field lines orthogonal to the direction of gas flow. 
     
     
         5 . The apparatus of  claim 1 , wherein the magnetic field generator generates magnetic field lines parallel to a direction of gas flow in the dielectric plasma confinement tube. 
     
     
         6 . The apparatus of  claim 1 , wherein the thermal plasma comprises a core region having a first temperature ranging from about 9000K to about 11000K and a peripheral region having a second temperature ranging from about 300K to about 1000K. 
     
     
         7 . The apparatus of  claim 1 , wherein the RF current has a frequency ranging from about 3 MHz to about 100 MHz. 
     
     
         8 . A system for fining molten glass comprising at least one apparatus according to  claim 1 . 
     
     
         9 . The system of  claim 8 , further comprising a fining vessel containing the molten glass. 
     
     
         10 . The system of  claim 9 , wherein the at least one apparatus is directed at a glass-air interface in the fining vessel. 
     
     
         11 . The system of  claim 9 , wherein the at least one apparatus is directed at an exterior surface of the fining vessel. 
     
     
         12 . A method for fining molten glass comprising:
 introducing a gas into an apparatus for generating a thermal plasma, the apparatus comprising:
 an electrode, 
 a grounded electrode, 
 a dielectric plasma confinement vessel extending between the electrode and the grounded electrode, 
 a magnetic field generator extending around the dielectric plasma confinement vessel, 
 an inlet for delivering a gas into the dielectric plasma confinement vessel, 
 an RF current source for converting the gas into a thermal plasma, and 
 an outlet for delivering the thermal plasma, 
   introducing molten glass into a fining vessel; and   contacting the molten glass with the thermal plasma.   
     
     
         13 . The method of  claim 12 , wherein the gas is a noble gas chosen from argon, helium, neon, krypton, and xenon. 
     
     
         14 . The method of  claim 12 , wherein contacting the molten glass with the thermal plasma comprises directing the thermal plasma at a glass-air interface in the fining vessel. 
     
     
         15 . The method of  claim 12 , wherein contacting the molten glass with the thermal plasma comprises directing the thermal plasma at an exterior surface of the fining vessel. 
     
     
         16 . The method of  claim 12 , wherein the thermal plasma heats the molten glass to a temperature greater than or equal to about 1700° C. 
     
     
         17 . The method of  claim 12 , wherein the thermal plasma locally heats at least one predetermined region in the fining vessel through which the molten glass flows. 
     
     
         18 . A glass structure having a T g  greater than about 1650° C. and a bubble concentration of less than 0.001 bubbles/pound. 
     
     
         19 . The glass structure of  claim 18 , comprising from about 45 to about 95 wt % collectively of alumina and/or silica and from about 5 to about 55 wt % collectively of at least one oxide of barium, boron, magnesium, calcium, sodium, strontium, tin, and/or titanium 
     
     
         20 . The glass structure of  claim 18 , wherein the glass structure is a glass sheet.