金属硅的酸洗和氧化提纯

Purification Metallurgical Silicon by Acid Leaching and Oxidation

为了降低金属硅酸洗的后续工艺难度,在成熟的常温酸洗技术的基础上加上湿氧氧化新技术对金属硅进行提纯.酸洗主要作用是去除大部分裸露在金属硅颗粒表面的金属杂质;而湿氧氧化后,使颗粒内部分凝系数(在硅和二氧化硅系统中的分凝系数)较小的硼在高温下扩散进入二氧化硅中,再腐蚀去除氧化层和其中的杂质.实验表明该方法对硼杂质有明显的提纯作用,提纯后,硼杂质的含量最低为4×10-6.两种技术在工艺上兼容,在提纯目标上互补,是非常有效的低能耗和低成本的提纯方法.

To reduce the difficulty of the process after acid leaching, purification of metallurgical silicon with a combined technique of acid leaching at room temperature with oxidation has been studied in this paper. Acid leaching is useful to remove the most metallic impurities which are on the surface of the grains of Si. After thermal oxidation, B whose separation coefficient （in the system of Si and SiO3 ） is less than 1 would transfer towards SiO2 layer from the side of Si. Then SiO2 layer and the impurities in it were removed by fluorhydric acid. The result of the experiment shows that B would be removed powerfully. After the purification, the best result of the concentration of B is about 4×10^-6. And the method of oxidation has some effect in removing AI whose separation coefficient is less than 1 too. The two techniques are compatible in technology and complemented each other in the objective of purification. The technique in our experiment is a promising method with good effect,low cost and low energy.