Synergetic modification of industrial basic oxygen furnace slag and copper slag for efficient iron recovery

Abstract

With the continuous exploitation of primary high-quality mineral resources, these resources could be gradually exhausted, so it is of great significance to recover iron-rich basic oxygen furnace (BOF) slag as secondary mineral resources. Given the composition characteristics of BOF slag, a method of synergetic modification of copper slag as additive and BOF slag was proposed to separate iron minerals for recovery. In this study, FactSage thermodynamic simulation, chemical analysis, X-ray diffraction and scanning electron microscopy were used to analyze the phase transformation and structure evolution during the oxidative modification process, and the effects of oxidation temperature and addition amount of copper slag on the modification were studied. The results show that the addition of copper slag can effectively promote the transformation of iron oxides to MgFe2O4. When an appropriate amount of copper slag was added to make the basicity of the mixed slag be 2, the conversion rate of MgFe2O4, iron recovery rate and grade of magnetic slag were the best. In the oxidative modification process, increasing the oxidation temperature was beneficial to the formation and development of MgFe2O4. However, too high temperature could lead to the dissolution of Al3+ into MgFe2O4 and reduce its magnetism, which was not conducive to magnetic separation and recovery. When the mixed slag was modified at 1200 ℃, the grade of magnetic slag by magnetic separation was 31.14 % and the recovery was 64.04 %, which had the potential of returning to sintering or ironmaking. The secondary slag obtained at the same time can also be used to produce high value-added materials. Therefore, the current technological route can transform the two kinds of industrial solid waste into usable resources at the same time, and realize "waste treatment with waste".