Influence of ω(SiO₂)/ω(Al₂O₃) on the Crystalline Behaviour during Fibrillation of Melting-separated Red Mud Slag

Objective The preparation of inorganic fibres from melting-separated red mud is an effective way to achieve high-value scale utilization of red mud. During the fibrillation process of slag from melting-separated red mud, crystalline phase precipitation increases the viscosity and reduces the fluidity of the slag, thus affecting the quality of inorganic fibres. Method The effect of ω(SiO₂)/ω(Al₂O₃) on the crystalline behaviour of melting-separated red mud slag during the cooling process was investigated using FactSage thermodynamic simulation combined with X-ray diffraction analysis and field emission electron microscopy analysis. Result The mineral phases precipitated during the cooling process of fusion-split red mud slag are mainly chalcocite and spinel, yellow feldspar, feldspar, and chalcocite phases, and the first precipitated phases are constantly transformed with the increase of ω(SiO₂)/ω(Al₂O₃). The results of remelting tests showed that the initial crystallisation temperature of the melting-separated red mud slag decreased with increasing ω(SiO₂)/ω(Al₂O₃). At the condition of 1 300 ℃, when ω(SiO₂)/ω(Al₂O₃) increased to 0.86, no more crystals were precipitated from the melting-separated red mud slag. Conclusion Increasing ω(SiO₂)/ω(Al₂O₃) will be beneficial for the preparation of inorganic fibres from melting-separated red mud.