Physicochemical Properties of the Molten Iron-Rich Slags Related to the Copper Recovery
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INTRODUCTION
MOLTEN slag is the main byproduct of the copper smelting industries. Copper slag contains a significant amount of useful metals, such as Cu, Fe, Co and Ni, which are important secondary resources.[1–7] These elements mainly exist as oxides and matte in the magnetite or fayalite through chemical dissolution and mechanical entrapment.[8–12] Therefore, the physical properties of the molten copper slag play an important role in the metal recovery process. High-temperature viscosity is a key physical property related to molten slag fluidity during the copper pyrometallurgical process. The maximum viscosity of FeO-SiO2 binary molten slags is observed at the fayalite formation point. Kaiura et al. showed that the viscosity can be reduced slightly by increasing the Fe2O3/FeO mass ratio in the FeO-Fe2O3-SiO2 ternary system.[13] The same results have been obtained in other studies.[14] The viscosity can increase with the SiO2 content for a Fe-saturated FeO-Fe2O3-SiO2 slag.[15] The addition of FeO in the FeO-Fe2O3-SiO2-CaO system can decrease the molten slag viscosity due to FeO dissociation and silicate depolymerization.[16] Electrical conductivity is HUAIWEI ZHANG and LI FU are with the College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, P.R. China. Contact e-mail: [email protected] JIANBO QI is with the School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, P.R. China. WEIDONG XUAN is with the State Key Laboratory of Advanced Special Steel, Shanghai Key Laboratory of Advanced Ferrometallurgy, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, P.R. China Contact e-mail: [email protected] Manuscript submitted January 14, 2019. Article published online May 30, 2019. 1852—VOLUME 50B, AUGUST 2019
another important property, which closely correlates with molten slag diathermancy. The electrical conductivities for the various fayalite-containing systems of FexO-CaO-SiO2, FexO-CaO-MgO-SiO2, and FexOCaO-SiO2-Al2O3 were studied.[17–21] The higher the FexO, CaO, or MgO content in the molten slags, the higher the electrical conductivity. The conductance activation energies for these compounds are in similar ranges and decrease with the molten slag basicity. Surface tension and density are two other important properties. However, there are almost no relevant data for these properties in literature. Surface tension and density models have been developed by Tanaka et al.[22,23] and Chou, et al.,[24] respectively. These models are suitable for most ternary silicate-based molten slag comprising CaO, Al2O3, MgO, FeO, or MnO.[25–28] Liu et al. studied that increasing the MgO or Al2O3 content in a CaO-SiO2-MgO-Al2O3-based slag could increase their surface tension.[29] The interface tension between liquid Fe and molten CaO-SiO2-Al2O3 slag is related to the viscosity of the molten slag, and the oxygen interface diffusion was very slow in this system.[30] The density is increased significantly by the substituti
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