Magnetic separation of roasted hematitic ore

Roasting of hematitic ore has been tested in boosting of magnetic concentration of hematitic iron ore. Coke rate, roasting time, and temperature were analyzed at several levels based on literature. Sample characterization was done to evaluate the density of sample and the size particle of ore and coke. Thermogravimetric analysis has indicated hematite to magnetite transformation by characteristic peaks of mass loss. The hematite-magnetite transformation imparts strong contrast in magnetic susceptibility between iron-bearing minerals and gangue, composed basically of quartz. The results have confirmed the reinforcement of magnetism due to roasting process and photographs proved the magnetic character of roasted sample. The best condition obtained was 35 minutes, 10 % of coke (in mass), and 1,023 K (750 oC). The yield was increased by 5.3 % under 0.93 T and by 240.3 % under 0.06 T, increasing selectivity of magnetic separation even under low magnetic gradient. This route could be successfully applied to tailings at low gradient field, recommending the application of this technique for iron ore processing, naturally after careful economic analysis, in which the quantification of environmental liabilities (primarily resulting from its non-implementation) is included.