Abstract
We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition. Without flux, the pseudobrookite phase with a high melting temperature was precipitated during ilmenite smelting. This could be the main reason for decreased reduction of iron in ilmenite. To accelerate reduction of ilmenite, two factors were considered. One is increasing the reduction driving force during smelting. Activity of FeO is the major factor to control reduction in driving force. The other factor is delay in formation of the pseudobrookite phase, a high-melting point precipitation phase. In this system, MgO in ilmenite could be used to form pseudobrookite. To control these factors, in this study, flux agent (i.e., Na2O or SiO2) addition was considered. The thermochemical simulation program, FactSageTM7.0 was used to calculate the viscosity of slag and the activity of components as fluxing agents were added. High-temperature experiments using an induction furnace were also conducted to confirm the computational results. To determine the composition of final products, i.e., titanium slag, X-ray fluorescence analysis was executed. As a result of Fe and Ti behaviours in slag, SiO2 addition showed no significant difference from the slag without flux. However, Fe reduction in ilmenite, i.e. TiO2-enrichment, was more accelerated when Na2O was added. X-ray diffraction, scanning electron microscopic and transmission electron microscopic analyses results also showed that even 1 wt% Na2O addition significantly influenced the titanium slag production compared to no flux addition.
Highlights
We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition
The composition of raw ilmenite was investigated by X-ray fluorescence spectroscopy (XRF; ZSX Primus II, Rigaku, Japan), and X-ray diffraction (XRD; D/MAX-2500/PC, Rigaku, Japan) was used to confirm the phase
The absolute values of the lattice parameter of each sample could not be precisely determined from HRTEM, we suggest that the structure of Na2O-fluxed titanium slag sample is closer to the structure of Ti3O5 since the ideal (010) interplanar spacing of Ti3O5 is larger than that of FeTi2O5
Summary
We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition. The pseudobrookite phase with a high melting temperature was precipitated during ilmenite smelting. This could be the main reason for decreased reduction of iron in ilmenite. The other factor is delay in formation of the pseudobrookite phase, a high-melting point precipitation phase. In this system, MgO in ilmenite could be used to form pseudobrookite. MgO in ilmenite could be used to form pseudobrookite To control these factors, in this study, flux agent (i.e., Na2O or SiO2) addition was considered. The other is increasing the activity of FeO in slag as a driving force in the smelting reduction process. The higher the activity of FeO, the lower the viscosity of slag is expected, which improve the reaction kinetics
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