Tin Removal from Tin-Bearing Iron Concentrate with a Roasting in an Atmosphere of SO2 and CO

Abstract

The tin could be volatilized and removed effectively from the tin-bearing iron concentrate while roasted in an atmosphere of SO2 and CO. The reduction of SO2 by CO occurred in preference to the SnO2 and Fe3O4, and the generated S2 could sulfurize the SnO2 to an evaporable SnS, which resulted in the tin volatilization. However, the Fe3O4 could be sulfurized simultaneously, and a phase of iron sulfide was formed, retaining in the roasted iron concentrate. It decreased the quality of the iron concentrate. In addition, the formation of Sn-Fe alloy was accelerated as the roasting temperature exceeded 1100 °C, which decreased the Sn removal ratio. An appropriate SO2 partial pressure and roasting temperature should be controlled. Under the condition of the roasting temperature of 1050 °C, SO2 partial pressure of 0.003, CO partial pressure of 0.85, and residence time of 60 min, the tin content in the roasted iron concentrate was decreased to 0.032 wt.% and the sulfur residual content was only 0.062 wt.%, which meets the standard of iron concentrate for BF ironmaking.