Effect of MgO and CaCO₃ as Additives on the Reduction Roasting and Magnetic Separation of Beach Titanomagnetite Concentrate

Abstract

To understand the effect of MgO as additive on the reduction roasting of beach titanomagnetite concentrate, the phase transformations, metallization degree and Fe–Mg–O phase diagram were studied in this paper. Results indicated that with the increasing of MgO dosage, more Mg²⁺ diffused into the magnetite lattice, replaced some of the Fe²⁺, and formed a large of MgFe₂O₄. So adding MgO not only did not effectively improve iron recovery, but baffled the reduction of iron oxides. Besides, the effect of CaCO₃ on the growth of iron particles was also studied by optical microscope and Qwin image analysis software. Tests revealed that an appropriate CaCO₃ dosage can facilitate the growth of iron particles. Because CaCO₃ promoted the reaction of iron oxides, FeO content in the slag decreased and more nuclei of iron crystal was formed, resulting in the growth of iron particles. However, excessive CaCO₃ increased the slag melting point, which hindered the diffusion and growth of iron particles. At last, the best product indexes were obtained by magnetic separation when CaCO₃ dosage was 4%.