太阳能硅制备过程湿法提纯SiO_2的工艺优化

Optimization of Hydrometallurgical Purification for SiO_2 in the Process of Preparing Solar-grade Silicon

考察了HF质量分数、H2C2O4质量分数、HNO3质量分数、酸浸时间、粒径、液体质量与固体质量的比值(简称液固比,下同)等因素对混酸法提纯SiO2工艺过程的影响,利用电感耦合等离子体发射光谱仪(ICP-OES)、场发射扫描电子显微镜(SEM)进行表征。结果表明,最佳工艺条件为:w(HF)=2%、w(H2C2O4)=3%、w(HNO3)=30%、酸浸时间4 h、粒径100～120目、液固比4∶1、酸浸温度30℃。Fe、Al、Ca、P杂质的去除率分别达到99.99%、14.02%、73.27%、60.00%,经混酸法处理后SiO2中杂质总量的质量分数降至1.465×10-4。

As a pre-treatment unit for preparing solar-grade silicon, hydrometallurgical route could remove most metallic impurities in silicon dioxide （SiO2 ） and raise the yield of the final product. Acid leaching of SiO2 could reduce the cost and energy consumption of industrialized development. Combined with high purity of reducing agent, the successor process of pyrometallurgy can also achieve ＂continuous casting＂. Factors such as the mass fraction of leaching agent, time, the particle size of SiO2, and the liquid-solid ratio were investigated, and the samples were characterized by means of ICP- OES, SEM, etc. The optimal reaction conditions were as follows ： w （HF） = 2 %, w （ H2 C2 O4 ） = 3 %, w （HNO3 ） = 30% ,reaction time 4 h ,the average size of SiO2 powder particle 100 -120 mesh ,the liquidsolid ratio 4：1 ,and room temperature 30 ℃. It was found that the final removal rates of impurities of Fe, Al, Ca, P could reach 99.99%, 14.02% ,73.27%, and 60.00% respectively and the mass fraction of total amount of impurities could be reduced to 1. 465 ×10-4.