Process for Melting and Refining Soda-Lime Glass

Abstract

A process for making soda-lime glass includes forming and refining sodium silicate glass in liquid phase. At least one other material is dissolved in the refined liquid phase sodium silicate glass to produce a liquid phase soda-lime glass melt. Formation of sodium silicate glass as an intermediate product before mixing with at least one other glass-forming material has the advantage of promoting release of gaseous reaction products from the sodium silicate glass during the refining step due at least in part to the relatively low viscosity of the sodium silicate glass. One or more steps in the process can be carried out under reduced pressure to promote release of gases and to reduce bubble formation.

1 . A process for making soda-lime glass, which includes the steps of:
 (a) forming sodium silicate glass (Na2O-SiO2) in liquid phase;   (b) refining the liquid phase sodium silicate glass of step (a); and   (c) after completion of step (b), dissolving at least one other material in the refined liquid phase sodium silicate glass of step (b) to produce a liquid phase soda-lime glass melt.   
     
     
         2 . The process set forth in  claim 10  wherein step (b) is carried out under reduced pressure to promote release of a gaseous reaction product from the liquid phase sodium silicate glass of step (a). 
     
     
         3 . The process set forth in  claim 1  wherein said step (a) includes:
 melting and reacting soda ash (Na2CO3) and silica (SiO2) with each other, but without addition of water (H2O), to produce carbon dioxide (CO2) as and form the sodium silicate glass (Na2O-SiO2) in liquid phase. 
 
     
     
         4 . The process set forth in  claim 3  wherein the soda ash and the silica are melted and reacted with each other at a molar ratio of about 1:1 to about 1:5. 
     
     
         5 . The process set forth in  claim 1  wherein said step (b) is carried out at a temperature in the range of 900° C. to 1700° C. 
     
     
         6 . The process set forth in  claim 1  wherein said step (a) includes:
 melting and reacting sodium chloride (NaCl) with silica (SiO2) and steam (H2O) to produce hydrogen chloride (HCl) as and form the sodium silicate glass (Na2O-SiO2) in liquid phase. 
 
     
     
         7 . The process set forth in  claim 1  wherein the at least one other material of said step (c) is selected from the group consisting of: calcium oxide (CaO), silica (SiO2), cullet, and combinations thereof. 
     
     
         8 . The process set forth in  claim 13  wherein step (c) includes mixing to promote dissolution of the at least one other solid phase material in the refined liquid phase sodium silicate class of step (b). 
     
     
         9 . The process set forth in  claim 1  wherein step (c) is carried out at a temperature greater than about 900° C. 
     
     
         10 . The process set forth in  claim 1  wherein said step (a) includes:
 reacting a sodium-containing compound with silica (SiO2) to form the sodium silicate glass (Na2O-SiO2) in liquid phase. 
 
     
     
         11 . The process set forth in  claim 3  wherein step (b) is carried out under reduced pressure to promote release of carbon dioxide (CO2) gas from the liquid phase sodium silicate glass of step (a). 
     
     
         12 . The process set forth in  claim 6  wherein step (b) is carried out under reduced pressure to promote release of hydrogen chloride (HCl) gas from the liquid phase sodium silicate glass of step (a). 
     
     
         13 . The process set forth in  claim 1  wherein the at least one other material of said step (c) is in solid phase prior to being dissolved in the refined liquid phase sodium silicate glass of step (b). 
     
     
         14 . The process set forth in  claim 7  wherein the liquid phase soda-lime glass melt produced in step (c) has a higher concentration of silica (SiO2) than the refined liquid phase sodium silicate glass of step (b). 
     
     
         15 . The process set forth in  claim 1  wherein step (c) includes dissolving silica (SiO2) in the refined liquid phase sodium silicate glass of step (b) such that the liquid phase soda-lime glass melt produced in step (c) has a higher concentration of silica than the sodium silicate glass of step (b). 
     
     
         16 . The process set forth in  claim 1  wherein the refined liquid phase sodium silicate glass of step (b) has a relatively low viscosity at a temperature in the range of 900° C. to 1700° C., and the liquid phase soda-lime glass melt produced in step (c) has a higher viscosity than the sodium silicate glass of step (b) at the same temperature.