Reaction mechanism and kinetics of boron removal from molten silicon via CaO-SiO<sub>2</sub>-CaCl<sub>2</sub> slag treatment and ammonia injection

Journal article (2019)

Authors

Hui Chen University of Tokyo, Sichuan University
Xizhi Yuan Sichuan University
Kazuki Morita University of Tokyo
Yanjun Zhong Sichuan University
Xiaodong Ma University of Queensland
Z. Chen (OLD) MSE-3
Ye Wang Sichuan University
Research Group
(OLD) MSE-3
More Info
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Published Date

2019

Language

English

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Research Group

(OLD) MSE-3

Abstract

To improve the boron-removal efficiency of metallurgical-grade silicon by increasing the reaction rate, a combined method with the 30 mol pct CaO-23.3 mol pct SiO2-46.7 mol pct CaCl2 slag treatment and ammonia injection at 1723 K to 1823 K was proposed. For 1 hour and at 1823 K, the maximum removal efficiency of boron was 98 pct, and the final boron concentration in silicon decreased to 1.5 ppmw by the present method without the introduction of the iron catalyst. A kinetic model was also established to clarify the reaction mechanism and rate-limiting steps of this complicated boron-removal process. In this model, the rate-limiting step is the mass transfer of boron oxide at the interface between the slag and silicon phase.