2015 Volume 55 Issue 10 Pages 2090-2097
The performance of iron ore sinter in a blast furnace such as strength and reducibility is strongly affected by the amount and the chemical composition of liquid phase in sinter during the sintering process. Thus, it is necessary to control the production of liquid phase during the sintering process. Iron ore sintering process consists of rapid heating of pulverized raw materials, partial reduction reaction of iron ores as well as liquid phase production, which are caused by combustion of cokes and suction of flaming gas. The heating time of raw materials is too short that the chemical reactions within the sinter never reach the thermodynamic equilibriums. Nevertheless, controlling the melt production could be attempted based on the thermodynamic data such as the phase diagrams. In this study, liquidus lines coexisting with iron oxides and/or 2CaOSiO2 in the FeOx–CaO–SiO2 system have been measured at 1573 K in the range of oxygen partial pressures between 10−6 atm and 10−2 atm. In addition, the effect of Al2O3 content on the liquidus has also been investigated as Al2O3 is a major gangue component affecting the quality of sinter. It has been found that the homogenous liquid region extends over a wide range of CaO/SiO2 (C/S) ratio between 0.6 and 2 or even more for all the measurement oxygen partial pressures. It has also been found that the FeOx content in liquid phase at C/S = 1.0 in equilibrium with solid FeOx is almost constant to be 40–45 mass% irrespective of oxygen partial pressures. However, the FeOx content decreases with an increase in Al2O3 content, indicating that the homogenous liquid region in the FeOx-rich side becomes narrower. As a consequence, it is considered that the amount of slag melt produced in sinter during the sintering process becomes smaller with increasing Al2O3 content.