Diffusion and Mass Transfer of Impurity P in the Purification of Metallurgical-Grade Silicon Using Calcium Silicate Slag
摘要
The study of diffusive mass transfer of impurity phosphorus (P) in silicon melts was a crucial aspect of achieving efficient deep P removal. To elucidate the mass transfer mechanism of P in silicon melts, this paper presents a kinetic analysis of impurity P removal from silicon melts. To minimize the effects of convection on diffusion, a capillary diffusion device was employed to conduct experimental investigations of P diffusion in silicon melts at different temperatures. According to slag–silicon refining experiments, the mass transfer process of P between the silicon melt and the slag phase was characterized and the mass transfer coefficient of P in the silicon melt was calculated. The experimental results indicated that the diffusion coefficients of P in silicon melt at 1450 °C, 1500 °C, and 1550 °C were 2.81 × 10−8, 3.24 × 10−8, and 3.91 × 10−8 m2·s−1, respectively. Through the calculation of the activation energy for P diffusion, the relationship between the diffusion coefficient and temperature was determined as