2017 Volume 57 Issue 2 Pages 228-235
Aiming to better understand the effect of MgO on sintering process of iron ores, the formation of [Mg1-x,Fex]O·Fe2O3 in solid-state reactions between MgO and Fe2O3 was studied. Experiment was carried out in air from 873 K to 1573 K by MgO mixing with Fe2O3. X-ray diffraction, optical microscope, scanning electron microscopy and energy-dispersive spectroscopy were used to characterize the phase change of the sintered samples. The content of ferrous ion in the sintered samples was determined by potassium dichromate titration for distinguishing the MgO·Fe2O3 (x=0) and the Fe3O4 (x=1). Thermogravimetric and differential scanning calorimeter test was carried out in air by MgO mixing with Fe2O3 to investigate the thermal decomposition of Fe2O3. The results show that the reactions between the Fe2O3 and MgO in air formed first the magnesium ferrite at 1073 K, subsequently magniferous magnetite appeared at 1173 K, resulting that the thermal decomposition of Fe2O3 was carried out at a lower temperature than that of its own self. The following conversion of the magniferous magnetite to the magnesium ferrite was also observed with the temperature increasing to 1482 K. It has been deduced that the [Mg1-x,Fex]O·Fe2O3 is formed by the reaction between the prior formed MgO·Fe2O3 and the Fe2O3 in the heating-up process. It was obtained that amount of ferrous ion formed in sintering process is mainly related by the amount of MgO in raw materials and it’s diffusion rate. Therefore, adding MgO appropriately into raw material can be beneficial to improve the low temperature reduction degradation of iron ore sinter.