Regular Article

Study on the separation of silicon from refining slag of industrial silicon

State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, PR China

^* e-mail: ghzhang0914@ustb.edu.cn

Received: 6 November 2020
Accepted: 22 April 2021

Abstract

During the process of production and refining of industrial silicon, the discharged slag usually contains more than 15 mass% of metallic silicon. However, the separation of silicon from slag is very difficult due to the close density of silicon and slag as well as the high viscosity of slag, which results in the waste of resources. In the present work, the effect of Na₂O addition on the separation of silicon from slag is investigated in detail. It is found that the optimum separation condition of slag and silicon is 1723 K reacting for 60 min by adding 10 mass% Na₂O to the slag. Viscosity and density are two important factors affecting the separation effect of silicon from slag. The addition of Na₂O reduces the viscosity of slag and promotes the separation of silicon from slag. Even if the addition of Na₂O will decrease the density of slag which is detrimental to the separation of silicon, the density variation is not the determining factor affecting the separation relative to viscosity. The separation and extraction of metallic silicon from silicon slag is of great significance for improving utilization of resources and reducing environmental pollution.