Role of MgO in Sinter from Perspective of MgO Distribution between Liquid and Magnetite Phases in FeO_x-CaO-SiO_2-MgO System

摘要

The chemical compositions of liquid in equilibrium with FeO_x in the FeO_x-CaO-SiO_2-MgO system at 1 573 K and oxygen partial pressures of 10~(-7) atm and 10~(-6) atm have been determined along with the MgO concentrations in the liquid and FeO_x phases to understand the role of MgO in improvement of reducibility of the sinter produced from deteriorated iron ores. The liquid area in the FeO_x-rich side was decreased with additions of MgO over the measurement range of C/S ratios between 0.32 and 2.28, and was separated into silicate-based and calcium ferrite-based liquid phases, where 2CaO-SiO_2 phase becomes stable thermodynamically in the C/S ratios between 1.66 and 1.96. The ratio of MgO concentration in the liquid phase to that in the FeO_x phase decreased with increasing C/S ratio from 0.36 to 2.28, which trend has been explained from the viewpoint of basicity. On the basis of these findings, the role of MgO in improvement of reducibility of the sinter has been discussed to conclude that additions of MgO make the cohesive zone thinner and improves the gas permeability in a blast furnace.