Comparative study of magnetic reduction-separation behavior and kinetics of refractory oolitic iron ore through coal-based versus gas-based reductive roasting

A comparative study was conducted on the kinetics of coal- and gas-based magnetization roasting processes and the reduction-separation behavior for an oolitic hematite ore. The magnetization reduction rate of roasted ore reached 46.86%when roasting for 45 min under 750 ℃with coal-to-ore ratio of 8% for coal-based system, an optimized concentrate with iron grade and recovery rate of 61.51% and 91.43% could be obtained; for gas-based system, the magnetization rate was 44.34%, and the iron grade and recovery rate reached 58.09% and 94.30% under the optimized roasting temperature of 650 ℃ for 60 min with CO proportion of 30%. Microscopic morphology analyses indicated that the transformation process for both systems was in accordance with the unreacted-core shrinking model. Artificial magnetite was generated layer-by-layer, and the inside oolitic cores were difficult to fully magnetize. Kinetic studies showed that the magnetization reduction process mainly fitted the internal-diffusion-control and chemical-reaction-control model, respectively, for coal- and gas-based systems, with activation energy of 127.80 and 36.68 kJ/mol, indicating that the gas-based system was significantly lower than that of the coal-based system.