Effects of TiO₂ content on the viscosity and structure of primary slag in blast furnace with high FeO content

The physicochemical properties of primary slag in a blast furnace are closely related to the smooth operation of the blast furnace. In this paper, the CaO-SiO₂-MgO-Al₂O₃-FeO-TiO₂ slag system in vanadium and titanium ore blast furnace smelting was studied. The changes in the properties of primary slag with varying titanium load were examined through a combination of experimental studies and thermodynamic calculations. The slag viscosity was measured by the rotating cylinder method, while FactSage thermodynamic software was employed to calculate crystal phase transition during the crystallization process. Raman spectroscopy was further applied to analyze the structural evolution of the slag. The results show that with the increase of TiO₂ content in the primary slag, the slag viscosity decreases. The lower the temperature, the more significant the impact of TiO₂ on the viscosity of the slag. TiO₂ behaves as a basic oxide in this slag system, dissociating free oxygen ions to disrupt the slag structure. Additionally, as the TiO₂ content increases, the initial crystallization temperatures of perovskite and titaniferous spinel exhibit an upward trend, while the crystallization temperature of melilite gradually decreases and remains below 1 573 K. Thereby, TiO₂ can promote the precipitation of Ti-containing crystalline phases during the cooling process. When TiO₂ is added to the slag, it releases Ti⁴⁺ and free oxygen ions (O^2-), and O^2- can break the bridging oxygen in the Si-O network, simplifying complex structural units.