Experimental study and modelling of viscosity of chromium containing slags

Abstract

An apparatus was constructed to measure the viscosities of molten slags at high temperatures up to 1750 °C. Techniques and methods of viscosity measurement for chromium containing slags were developed using a concentric rotating cylinder method in combination with a high temperature furnace. The viscosities were measured for Al2O3-CaO-MgO-SiO2 slags, and for several slag systems containing chromium oxides, from a quasi-binary system CrOx-SiO2 to quasi-ternary and quaternary systems.

At low oxygen partial pressures such as in typical metallurgical processes, the chromium in the slag appears simultaneously as divalent (CrO) and trivalent (CrO1.5) oxides. It was proven that decreasing the oxygen partial pressure in the system by contacting the slag with metallic chromium increased the amount of divalent CrO, which consequently lowered the melting temperature and viscosity of the slag as well. The measured data were used to develop viscosity models based on the Iida model, the modified Iida model, the modified Urbain model and neural network algorithm methods. The Iida model and the modified Iida model performed well for slags with relatively low chromium content, less than 5 wt. %. In favour of the Iida model, it must be remembered that the chromium content in metallurgical slags is normally quite low. Also, the modified Urbain model accurately predicted the viscosities of slags with higher chromium levels. The neural network computation also proved to be a promising approach for predicting viscosities of metallurgical slags.