Study on the kinetic mechanism of steel resulfurization by sulfur-bearing slag

School of Metallurgical and Ecological Engineering University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing City 100083, P.R. China
e-mail: chunyangliuvip@163.com

Received: 31 December 2014
Accepted: 19 June 2015

Abstract

In practice, hot metal with low sulfur content is inevitably resulfurized in an oxygen converter. In order to fully understand the steel resulfurization process and control the sulfur content at the end of the converter blowing, resulfurization behavior of steel by slag (CaO-FeO-SiO₂-CaS) was investigated in this study. The rate-controlling step was obtained and further confirmed through Si-Mo electric resistance furnace and induction furnace experiments. The effects of slag parameters including slag basicity, slag amount, initial sulfur content, CaF₂ and MgO content on the rate and extent of resulfurization were investigated through induction furnace experiments. The results indicate that the rate-controlling step of resulfurization lies in sulfur transfer in the slag phase. The initial sulfur content and slag amount have a positive effect on both the rate and extent of resulfurization, while slag basicity has a negative effect on either the rate or extent of resulfurization. CaF₂ addition promotes the rate of resulfurization but has little impact on the resulfurization extent. MgO addition has complex effects on resulfurization. In addition, a kinetic model was developed and its calculation results agreed well with the experimental data.