Electrically Enhanced Metal Purification Using Slag
A novel electrically-enhanced metal purification using slag has been developed. This was achieved by applying DC potential between liquid metal and slag phases. The concept was demonstrated through small-scale experiments at temperatures of 1500–1600°C for the removal of boron from Si-B melt using CaO-SiO2-16wt%Al2O3. Silicon (containing B) and slag were reacted in an alumina crucible in a resistance tube furnace. A circuit was produced by immersing graphite rods into the silicon bath and the slag layer. Electrical potential differences of up to 3.5 V were applied during the reactions. The reaction rates, the open-circuit voltages and short-circuit currents (in the case when the potential was applied) were then measured and determined for various slag to silicon ratio. It has been shown from this study that both the apparent rate and the boron partition ratio were increased by a factor of approximately 1.6.
Keywordssilicon metal purification solar grade silicon electrochemistry kinetics
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