Research On Boron Removal Process For Metallurgical Grade Silicon Via A High Temperature Slagging Method

The main purpose for this thesis is improving the metallurgical-physicstechnical route for low cost production of solar grad silicon. This thesis proposed akind of purification method via high temperature solid phase reaction based onoxide slagging process and acid extraction to remove boron from metallurgicalgrade silicon, the method in the traditional methods for the purification of siliconmetal "slagging method" basis, mainly through the high temperature solid phasereactions between Al2O3and SiO2or MgO substances to generate mullite or spinelproducts, respectively, at the same time. The solid reaction speed can be controlledthrough the choice of crystal structures and microstructures of raw materials or byadding other oxides to the raw substances, and the high temperature solid reactioncontrollability can be implemented, and therefore the purification efficiency canbe optimized. During the high temperature solid phase reaction process, the atomsof each component in the reaction products rearranged to form new lattice. Due tothe small atomic radius of boron, the boron impurities in molten liquid silicon canbe easily absorbed into the newly formed product lattice. This method is especiallyeffective to remove the boron in metallurgical silicon, and it also has goodremoval effect for other impurities in metallurgical silicon. This method has thecharacteristics of low cost, simple process, and high efficiency.