Kinetic Analysis of Boron and Phosphorus Removal from Si-Fe Alloy by CaO-Al2O3-SiO2-Na2O Slag

Abstract

A hybrid process of slag and solvent refining was used to remove boron and phosphorus from silicon. Quaternary slag of CaO-Al2O3-SiO2-Na2O was employed to remove boron (B) and phosphorus (P) from Si-20 wt% Fe alloy at 1300 °C. A slag-to-metal ratio of one was used at different reaction times. The mass transfer coefficient of B and P in the slag and alloy phases was calculated to determine the rate-limiting step. The mass transfer coefficients of B in the alloy and slag phases were 6.6 × 10−7 ms−1 and 2.8 × 10−7 ms−1, respectively. The mass transfer coefficients of P in the alloy and slag phases were determined to be 7.5 × 10−8 ms−1 and 3.5 × 10−7 ms−1, respectively. The rate-limiting stage of the slag–alloy reaction kinetics was mass transport in the liquid slag for B and mass transport in the alloy phase for P.