Isothermal reduction kinetics and reduction prediction for iron ore pellets

Iron ore pellets, as one of the main charges of blast furnaces, have a greater impact on the CO₂ emission reduction and stable operation of blast furnaces. The isothermal reduction behavior of the pellets obtained from a Chinese steel plant was studied in the gas mixtures of CO and N₂. The results showed the reduction process is divided into two stages. The reduction in the initial stage (time t ≤ 40 min) is cooperatively controlled by internal diffusion and interface chemical reactions with the activation energy of 30.19 and 16.67 kJ/mol, respectively. The controlling step of the reduction in the final stage (t > 40 min) is internal diffusion with the activation energy of 34.60 kJ/mol. The reduction process can be described by two equations obtained from kinetic calculations. The reduction degree can be predicted under different temperatures and time, and the predicted results showed an excellent correlation with the experimental results. The reduction mechanisms were confirmed by the analysis of the scanning electron microscope equipped with an energy dispersive spectrometer and optical microscope.