Influence of alumina on physical properties of an industrial zinc-copper smelting slagPart 1 – viscosity

The rotating cylinder method was applied to measure the viscosities of an industrial iron silicate slag and mixtures of this slag with 5, 10 and 15 wt-% alumina addition, in temperature range 1100–1300°C. The measured viscosities were compared with the predicted values using two of the commercially available software products for viscosity calculations, namely Thermoslag®1·5 and FactSage™6·2. As the models can only predict viscosities for a solid free melt, obtained values by FactSage™6·2 were modified using the Einstein–Roscoe equation. Results show that aluminium behaves as a network former cation in this type of slag, and by increasing the alumina concentration, the melt becomes progressively polymerised. Consequently, the viscosity of the slag increases at a given temperature, which is supported by thermodynamic predictions. According to the modified FactSage™6·2 calculations, the viscosity of the solid containing slag increases from 2·1 to 5·5 poise at the industrial operating temperature (∼1250°C).