Thermodynamic Properties and Viscosities of CaO-SiO₂-MgO-Al₂O₃ Slags

In this work, the effects of Al₂O₃, basicity, and MgO/Al₂O₃ ratio on the heat capacity, enthalpy change, and viscosity of CaO-SiO₂-MgO-Al₂O₃ slags at 1773 K, 1823 K, and 1873 K (1500 °C, 1550 °C, and 1600 °C) were investigated. The heat capacity of the slag increased with increasing Al₂O₃, basicity, and MgO/Al₂O₃ ratio in the experimental temperature range. The enthalpy change increased with increasing Al₂O₃ content and MgO/Al₂O₃ ratio, and decreasing basicity. Under the fixed heat quantity of the slag, the addition of Al₂O₃ would result in a decrease of slag temperature and increase of slag viscosity. The effect of decreasing temperature on the viscosity was more significant than increasing Al₂O₃ content. Increases of slag basicity led to the increased slag temperature and the decreased viscosity which was due to the increased slag temperature. The viscosity change rate with different temperatures was more pronounced than that of different slag compositions. The change of the slag temperature at fixed heat quantity would be opposite due to different expressions of MgO/Al₂O₃ ratio. In addition, when the heat decrement of the slag was fixed, the slag temperature rose first with the increase of MgO/Al₂O₃ ratio and then decreased, while the viscosity decreased gradually. The viscosity fluctuation caused by different heat decrements reduced as well with increasing MgO/Al₂O₃ ratio.