2004 Volume 44 Issue 3 Pages 462-469
Commercially, high grade acidic and basic fluxed iron ore pellets were isothermally reduced at 1 023-1 273 K under different load values ranging from 0.0 up to 0.0559 MPa. The reduction was carried out with synthetic gas mixture containing 55 vol% H2, 36 vol% CO, 5 vol% H2O, 3 vol% CO2 and 1 vol% N2. The oxygen weight loss resulted from the reduction of Fe2O3 to lower oxides or to metallic iron was continuously recorded as function of time. X-ray phase analysis, optical microscope, high-pressure mercury porosimeter were used to characterise fluxed and reduced pellets. The different parameters affecting the reduction of these pellets were studied and correlated. It was found that the basicity of pellets (CaO+MgO)/(SiO2+Al2O3) is 0.37 and 1.62. At early and intermediate stages, the reduction increased gradually with temperature showing a significant increase in the rate at >1 173 K. At later reduction stages, the load had a measurable effect on the reduction due to the sintering of freshly reduced metallic iron that increased with temperature and reduction extent. The internal structure was correlated with the reduction kinetics to predict the corresponding mechanism. The inter-relating effect of temperature and load on the reduction kinetics of fluxed pellets was also given.