The Effect of Silica and Reducing Agent on the Contents of Impurities in Silicon Produced

Abstract

Petroleum coke, soft coal and silica are the main raw materials used to produce silicon, and impurities in them remarkably influence the purity of silicon products. Two different furnace types (8.5 MVA and 12.5 MVA) were used in this study, each of which has two different sub-types. The influence of the three raw materials on the contents of multiple impurities in silicon was systematically studied using a large industrial data set. The correlation between the total impurity contents in silicon products and the different amounts of raw materials used was analyzed by a linear regression method. The correlation between the percentage of impurity contents in silicon products in raw materials and the different raw material consumption was also investigated using the same method. The results showed that the total percentage of impurities in silicon products was closely associated with the amounts of raw materials used and the correlation coefficient reached ≥98%. The slopes of the linear fitting lines showed that using coal as the reducing agent significantly increased the percentage of impurities in silicon products followed by petroleum coke and silica. Comparing the 12.5 MVA and 8.5 MVA furnaces, the variation between the different raw materials and the percentage of impurities in silicon products was also represented by a linear fit. The 12.5 MVA furnaces exhibited more efficient smelting by producing the highest-quality silicon products under the same amounts of raw materials. The results may provide guidance and a theoretical basis for the future cleaner production of silicon.