Abstract
The effect of melting properties of quartz is discussed based on estimated temperature distribution in industrial furnaces combined with measured melting properties for various quartz sources.
Softening and melting properties for four industrial quartz sources have been investigated in a sessile drop apparatus in both non-isothermal experiments and with holding temperatures of 1730 oC, 1750 oC and 1775 oC. This showed that quartz needs superheating to achieve complete melting and that it takes long time to melt particles even with temperatures above the melting point of SiO2. Time needed for complete melting increases with decreasing temperature and is much longer than the time needed for heating the particle. Heating rates of 2, 5.5 and 10 oC/min have been investigated. With higher heating rates higher temperature is needed obtain complete melting. Recorded melting temperatures were similar in Ar and CO atmosphere.
Time needed to achieve complete melting varies considerably between the different quartz sources. This difference is expected to affect behaviour of different quartz sources in industrial FeSi and Si furnaces. The effect depends on the temperature profile in the industrial furnaces. A comparison of melting properties of quartz with the temperature profile in an industrial Si furnaces indicates that most of the furnace volume is filled with softened or partly molten SiO2. Use of and change between different quartz sources are based on this expected to affect furnace performance in industrial Si and FeSi production.
Softening and melting properties for four industrial quartz sources have been investigated in a sessile drop apparatus in both non-isothermal experiments and with holding temperatures of 1730 oC, 1750 oC and 1775 oC. This showed that quartz needs superheating to achieve complete melting and that it takes long time to melt particles even with temperatures above the melting point of SiO2. Time needed for complete melting increases with decreasing temperature and is much longer than the time needed for heating the particle. Heating rates of 2, 5.5 and 10 oC/min have been investigated. With higher heating rates higher temperature is needed obtain complete melting. Recorded melting temperatures were similar in Ar and CO atmosphere.
Time needed to achieve complete melting varies considerably between the different quartz sources. This difference is expected to affect behaviour of different quartz sources in industrial FeSi and Si furnaces. The effect depends on the temperature profile in the industrial furnaces. A comparison of melting properties of quartz with the temperature profile in an industrial Si furnaces indicates that most of the furnace volume is filled with softened or partly molten SiO2. Use of and change between different quartz sources are based on this expected to affect furnace performance in industrial Si and FeSi production.