INVESTIGATION OF PHASE TRANSFORMATIONS DURING THE SINTERING OF FERRUGINOUS SANDS FROM ALUMINA PRODUCTION FROM THE PERSPECTIVE OF MULTICOMPONENT OXIDE SYSTEMS

Abstract

This study examines the physicochemical characteristics of ferrous sands generated during alumina production from the perspective of thermodynamic–diagram analysis of multicomponent oxide systems. It was established that the specific properties of these ferrous sands, including their low melting point, fine particle size distribution, and the absence of clay components, hinder their application in conventional sintering processes and subsequent metallurgical treatment. To evaluate the mechanisms of phase formation, the FeO–CaO–Fe₂O₃–Al₂O₃, FeO–MgO–Fe₂O₃–Al₂O₃, and FeO–MgO–CaO–Fe₂O₃ systems, representing the composition of ferrous waste and the resulting slag melts, were investigated. The analysis showed that hercynite (FeAl₂O₄), which adversely affects the reducibility of iron-bearing materials and promotes the formation of low-melting slag phases, may form during the sintering process. The introduction of magnesia-containing fluxes was found to reduce the amount of hercynite while promoting the formation of more refractory phases, including magnesium and ferrite spinels, thereby improving the structural stability of the sinter. The thermodynamic analysis confirms the potential of MgO-containing fluxes for the sintering of ferrous sands and demonstrates the necessity of thermodynamic modeling of multicomponent oxide systems for selecting rational burden compositions and producing high-strength sinter with stable physicochemical properties. The results provide a theoretical basis for the development of technologies for the integrated recycling of iron-bearing alumina production wastes and for improving the preparation of iron ore raw materials for subsequent metallurgical processing.