Regular Article

Comparison between slag refining processes for B removal with metallurgical grade silicon and Si–Sn alloy

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), 100083 Beijing, PR China
² Beijing Key Laboratory of Green Recycling and Extraction of Metal, University Of Science & Technology Beijing, 100083 Beijing, PR China

^* e-mail: liyq_ustb@163.com

Received: 12 March 2018
Accepted: 17 May 2018

Abstract

Boron (B) removal by slag refining using CaO–SiO₂–CaCl₂ was investigated in metallurgical-grade silicon (MG-Si) and 75 wt% Si–Sn alloy. Experiments were conducted at 1500 °C for 15 min. The microstructure was characterized before and after refining. The effects of acid leaching, basicity, and slag/Si mass ratio on B removal were investigated. Experimental results showed that acid leaching had no effect on B removal from MG-Si but had a clear effect on the refined Si–Sn alloy after slag refining. The final B concentration was highly affected by the CaO/SiO₂ mass ratio with minimum value, where the content of B was reduced from 18.36 ppmw to 5.5 ppmw at the CaO/SiO₂ = 1.2 for MG-Si slag refining and from 18.36 ppmw to 3.7 ppmw at CaO/SiO₂ = 1.5 for 75 wt% Si–Sn alloy. Increasing the slag mass ratio by 2:1 mass ratio also increased B removal efficiency by approximately 15–20% more than an increase by 1:1.