The Effect of Melting at Low Temperature on the Quality of Glass

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This work has been done for the investigation of the effect of the melting at low temperature on the quality of glass. The low temperature process has been desired in order to save the energy for the fabrication of the glass products, and also to suppress the emission of carbon dioxide produced by the combustion of fossil fuels to attain high temperature condition in the melting tank. However, low temperature melting causes the depression of fining effect of the glass melts, resulting the glass containing a large amount of bubbles inside.In this study, the direct current electrochemical treatment (DCEC) has been applied on the glass melts at 1200-1300℃, which is 200℃ lower than the melting temperature, and the effect on the fining of the glass has been investigated. The application of 1.35DCV on soda-lime-silica glass melt through the Pt electrodes caused the continuous formation of bubbles with a large mean diameter about 1mm on anode. The bubbles ascended at a high speed about 1mm/min, and form the bubble layer on the melt surface. They also induced the convection in the melts. DCEC on the glass melts containing a large amount of fine bubbles (diameter<0.5mm) decreased the bubbles in the glass mostly within 1h-treatment, while the melting without DCEC could not remove the bubbles at all. DCEC was also found to have the effect of the redox control of transition metal ions in the melts. It could decolorize the glass effectively clue to the shift of the redox of metal ions, Fe^<2+> →Fe^<3+>, From these results, DCEC treatment was considered to be a promising new process solving the problems which are caused by the lowering of the melting temperature.