Liquidus Lines in the Fe-rich Region of the FeO_x–CaO–SiO₂–Al₂O₃ System at 1573 K under Oxygen Partial Pressures between 10?6 and 10?2 atm

摘要

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 2CaOSiO_(2) in the FeO_(x)–CaO–SiO_(2) 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 Al_(2)O_(3) content on the liquidus has also been investigated as Al_(2)O_(3) 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/SiO_(2) (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 FeO_(x) content in liquid phase at C/S = 1.0 in equilibrium with solid FeO_(x) is almost constant to be 40–45 mass% irrespective of oxygen partial pressures. However, the FeO_(x) content decreases with an increase in Al_(2)O_(3) content, indicating that the homogenous liquid region in the FeO_(x)-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 Al_(2)O_(3) content.