Rheological properties of Al2O3–CaO–SiO2 slags

The Al2O3–CaO–SiO2 ternary is a basic oxide system relevant for the Pedersen alumina production process and for aluminothermic silicon production with low environmental impact using secondary aluminium and silica raw materials. Rheological property is one of the most important properties for the above applications. A phenomenological viscosity model, inspired by the Calphad technique, has been proposed for the description of the rheological properties covering from homogenous liquid to heterogenous partial solidified Al2O3–CaO–SiO2 slags. The model has been developed by modification of the well-known Vogel-Fulcher-Tammann (VFT) formalism. Based on the phenomenological viscosity model, the effective diffusivity of slag can be evaluated. The relationships between cooling temperature rate, incubation time of solid precipitates as well as transition temperature have then been estimated. The model calculated the isothermal time-temperature-transformation (TTT) and the non-isothermal continuous-cooling-transformation (CCT) curves of CaAl2O4 and anorthite phases are in good agreement with the experimental observations.