Experimental and Morphological Investigations of the Reduction from Coarse Hematite to Magnetite and Wustite under Fluidized Bed Conditions

For optimization of iron ore fines reduction processes, fundamental knowledge of the reduction kinetics under industrial operating conditions is required. Reduction tests with coarse hematite iron ore were performed in H(2)-rich reduction gas atmospheres of H(2), H(2)O, CO, CO(2) and CH(4) considering elevated pressures similar to industrial process conditions. The reaction kinetics of the reactions hematite to magnetite, magnetite to wustite and hematite to wustite were investigated in a laboratory-scale pressurized fluidized bed reactor. To facilitate kinetic measurements, the laboratory-scale fluidized bed reactor is equipped with a sampling system, which allows sampling of the bed material at operating conditions. Process conditions were chosen close to industrial plants in a temperature range from 400 to 700 degrees C. Significant influence of temperature on the rate of reduction was found in all tests. Variation of reduction gas composition showed no influence on the rate of reduction in the range of concentrations investigated. Results presented herein proved the feasibility of depicting industrial process conditions in laboratory scale. For the reduction of hematite to magnetite and magnetite to wustite topochemical phase growth were observed. In the single step reduction of hematite to wustite, magnetite appeared as intermediate product formed by topochemical reaction while progressive conversion of magnetite to wustite was found.