Slag phase equilibria and viscosities in ferronickel smelting slags

The properties of the slag phase are critical to the smooth operation of ferronickel smelting operations. Phase equilibria studies have been carried out on the FeO-SiO2-MgO-Al2O3 system in equilibrium with iron in the range of compositions and temperatures directly relevant to the nickel laterite ores. The results of recent studies on liquidus temperatures and primary phase fields in the range 1500 -1650oC have been incorporated in FactSage databases, and the updated databases have been used to develop a fundamentally-based, quasichemical slag viscosity model capable of predicting the effects of changing temperature and slag composition at liquid and sub-liquid conditions over a wide range of compositions. The results of the model predictions of phase equilibria and viscosities are presented in the form of pseudo-binary sections. The study demonstrates the value of model predictions in identifying trends and the sensitivities of the system to changes in bulk composition and temperature. In particular the influence of the extensive solid solutions in the olivine (Mg,Fe)2SiO4 primary phase field on subliquidus equilibria, and the effects of alumina on phase equilibria and slag viscosities.