8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

The increment in the impurities of iron ore such as Al2O3 lowers the reducibility of iron ore sinter and increases the gas permeability resistance in a blast furnace. In order to overcome the problems, MgO is often added into sinter by blending dolomite and/or serpentine as a constituent of raw materials of sinters. The role of MgO in sinter at the lower part of a blast furnace depends on the MgO distribution in sinter. In this study, liquidus in equilibrium with iron oxides in the FeOx-CaO-SiO2-MgO system has been measured at 1573 K and at oxygen partial pressures of 10-7 atm and 10-6 atm which is similar to that of the sintering process. In addition, MgO concentrations in the liquid and the FeOx phases have also been measured so as to elucidate the compositional dependency of the MgO partitioning between two phases. It has been found that the liquidus region in the FeOx-rich side is decreased by 5 mass% MgO addition over the measurement range of the C/S ratios between 0.32 and 2.28. The liquidus is also divided into two compositional areas of the silicate-based liquid and the calcium ferrite-based liquid, where the C2S phase becomes stable thermodynamically in the range of the C/S ratios between 1.66 and 1.96. The MgO content in magnetite is as large as 14 mass% at C/S = 1.62, and the partitioning of MgO in liquid phase decreases with increasing the C/S ratio.