为了提高石英砂的杂质去除率,采用磁选加混酸酸洗工艺,并研究了酸洗反应动力学模型,对石英砂酸浸除杂进行理论指导。试验结果表明,铁去除率随着粒径减小而增大,150~180μm石英砂磁选效果最好。通过研究不同酸洗组合,发现混酸(硝酸+盐酸+氢氟酸)对铁的去除效果最好;使用混酸(V_酸∶V_水=1∶1),90℃水浴反应360 min,石英砂中铁去除率可达88.3%,铁杂质含量降为24.76μg/g,达到了精制石英砂的纯度要求。利用液固多相未反应核模型拟合发现,石英砂的酸洗过程控速步骤为产物内扩散控制,计算得出反应激活能Ea=51.73 k J/mol。
A new method about purification of metallurgical grade silicon （MG-Si） by a combination of Si-Al solvent refining andgas blowing treatment was proposed. The morphologies and transformation of impurity phases, especially for boron and iron in Si-Al melt were investigated during Ar-H2 gas blowing treatment. The mechanism of boron removal was discussed. The resultsindicate that gas blowing can refine grain size and increase nucleation of the primary Si. Boron can be effectively removed fromMG-Si using the Ar-H2 gas blowing technique during the Si-Al solvent refining. Compared with the sample without gas blowing,the removal efficiency of boron increases from 45.83% to 74.73% after 2.5 h gas blowing. The main impurity phases containingboron are in the form of TiB2, AlB2 and VB compounds and iron-containing one is in the form of β-Al5FeSi intermetallic compound.Part of boron combines [H] to transform into gas BxHy （BH, BH2） and diffuses towards the surface of the melt and is volatilized byAr-H2 gas blowing treatment under electromagnetic stirring.
