Structural viscosity model for aluminosilicate slags

Abstract

Based on the structure of aluminosilicate slag, a new model has been proposed for viscosity calculation of aluminosilicate slags. Contributions of bridging oxygen (O⁰), non-bridging oxygen (O⁻) and free oxygen (O²⁻) to viscous activation energy were modelled. Compositions of three types of oxygen were calculated from optical basicity values by combining the Toop–Samis model with a correlation between reciprocal of optical basicity and polymerisation extent proposed by Ottonello and Moretti. Charge compensation equilibrium among charge compensated Al, cations for modifying network and Al with no charge compensating cations was considered. The model has been applied in calculations of viscosity of the Al₂O₃–CaO–MgO–SiO₂ system. Good agreement between calculated and measured viscosity with a mean deviation of less than 25% was achieved. Since most viscosity measurements for molten slag at high temperature ware subject to an experimental uncertainty of 25%, the present model could provide accurate viscosity values for slag systems investigated.