Abstract
TiO2-FeO-Ti2O3 slag system is the dominant system for industrial high-titania slag production. In the present work, viscosities of TiO2-FeO and TiO2-FeO-Ti2O3 systems were experimentally determined using the concentric rotating cylinder method under argon atmosphere. A viscosity model suitable for the TiO2-FeO-Ti2O3 slag system was then established based on the modification of the Vogel-Fulcher-Tammann (VFT) equation. The experimental results indicate that completely melted high-titania slags exhibit very low viscosity of around 0.8 dPa s with negligible dependence on temperature and compositions. However, it increases dramatically with decreasing temperature slightly below the critical temperature. Besides, the increase in FeO content was found to remarkably lower the critical temperature, while the addition of Ti2O3 increases it. The developed model can predict the viscosities of the TiO2-FeO-Ti2O3 and TiO2-FeO systems over wide ranges of compositions and temperatures within experimental uncertainties. The average relative error for the present model calculation is < 18.82 pct, which is better than the previously developed models for silicate slags reported in the literature. An iso-viscosity distribution diagram was made for the TiO2-FeO-Ti2O3 slag system, which can serve as a roadmap for the Ilmenite smelting reduction process as well as the high titania slags tapping process.
Highlights
ILMENITE smelting is a carbothermic reduction process to upgrade the mineral ilmenite (FeTiO3) for subsequent TiO2 pigment production, yielding a TiO2-rich slag as the main product and pig iron as the by-product
The ilmenite smelting process using an electric submerge arc furnace (SAF) technology has already become a dominant process for producing high-titania slag worldwide[1] During the smelting process, an inevitable problem is the sudden surges of a foamy high-titania slag, sometimes becoming uncontrollable and thereby prolonging the melting time
Foaming phenomenon is due mainly to the insufficient slag fluidity caused by changes in slag temperature or composition during the smelting process[2] the fluidity of high-titania slag has a direct effect on the tapping behavior of the molten slag, the separation of the liquid slag and molten iron, and the SAF energy consumption.[3]
Summary
ILMENITE smelting is a carbothermic reduction process to upgrade the mineral ilmenite (FeTiO3) for subsequent TiO2 pigment production, yielding a TiO2-rich slag (generally, TiO2 > 70 mass pct) as the main product and pig iron as the by-product. Tuset[5] reported the viscosity measurements of 54 different slags located in the TiO2-Ti2O3-MgTiO3 ternary system in 1968 He concluded that the completely molten slags are considerably fluid and have a low level of viscosity values, ranging from 0.5 to 1 dPa s. Grau and Poggi[6] investigated viscosity variation of the QIT slag with temperature [QIT slag was a high-titania slag (TiO2 > 72 mass pct) produced by Quebec Titanium Iron Company (QIT), Canada] These researchers obtained a consistent conclusion that high-titania slag exhibited a very low level of viscosity values stabilized at around 0.3 dPa s. Zhang et al.[10] first conducted a thermodynamic simulation and experimentally studied the viscosity of the TiO2-FeO-Ti2O3 ternary slags They found that once completely melted, high titania slags displayed very low viscosity and were very insensitive to the temperature and slag compositions. The new viscosity model can describe the viscosities of the TiO2-FeOTi2O3 ternary high-titania slag system in broad composition and temperature ranges, including the solid-liquid slurries
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