Improving the production efficiency of high-titania slag in Ti extraction process: fluxing effect on formation of pseudobrookite

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., Na 2 o or Sio 2 ) addition was considered. The thermochemical simulation program, factSage TM 7.0 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, SiO 2 addition showed no significant difference from the slag without flux. However, Fe reduction in ilmenite, i.e. tio 2 -enrichment, was more accelerated when Na 2 O was added. X-ray diffraction, scanning electron microscopic and transmission electron microscopic analyses results also showed that even 1 wt% Na 2 o addition significantly influenced the titanium slag production compared to no flux addition.As titanium has good physical and chemical properties, e.g. excellent strength, corrosion resistance, fatigue resistance, fracture toughness, and high-temperature characteristics, its demand steadily increases 1-5 . The major raw material for titanium extraction is rutile (~95% TiO 2 ), which quickly is being depleted. Therefore, ilmenite (FeTiO 3 , 30-65% TiO 2 ) as a substitutional resource is in the spotlight. There are previous studies about the ilmenite smelting process in conjunction with pre-oxidation treatment, which improves the reactivity of ilmenite 6-13 . After the pre-oxidation treatment, the ilmenite ore is sent to direct leaching or high temperature reduction stages according to the consecutive processes [14][15][16][17][18] .Our group originally investigated the effect of temperature on FeO reduction, i.e., TiO 2 -upgrading, from ilmenite ore from 1723 to 1923 K 13 . Unlike the expectation that the Ti-yield would be greater with higher temperatures, the slag composition in the actual experiment was not significantly changed. One of the reasons is precipitation of pseudobrookite (ps-BR), which is one of the most stable phases with M 3 O 5 stoichiometry. In the position of M, the divalent cations (mainly Fe 2+ , minor Ti 2+ and/or Mg 2+ ) and the trivalent cations (primarily Ti 3+ ) are in balance of valence. Thus, it is normally expressed as [Fe,Ti,Mg] x Ti y O 5 (x + y = 3) formula. Because the melting point of ps-B...

Processing of titanium-containing ores for the production of titanium products: A comprehensive review

“…In particular, soda is added to the reduction charge [ [50] , [51] , [52] ], which is both a reduction catalyst and a flux that reduces the viscosity of the slag. The introduction of sodium oxide (Na 2 O) into the mixture leads to the formation of low-melting sodium titanates (Na 2 TiO 3 with a melting point of 1030 °C, Na 2 Ti 2 O 5 –985 °C, and Na 2 Ti 3 O 7 –1128 °C).…”

Influence of Anthracite-to-Ilmenite-Ratio on Element Distribution in Titanium Slag Smelting in Large DC Furnaces

“…The other factor is the delay in the formation of the pseudobrookite phase, which is a high-melting point precipitation phase. In this system, MgO in ilmenite can be used to form pseudobrookite [11].…”

Phase equilibria of the Na2O‐TiO2‐SiO2 system between 900 and 1600°C in air

“…5,6 Na 2 O fluxing in the form of Na 2 CO 3 can improve the recovery and kinetics of iron separation from SiO 2 -Na 2 O-TiO 2 slag that is titania-rich during the carbothermic reduction of ilmenite. 7,8 The formation of soluble sodium compounds is crucial in numerous metal extraction processes. 9,10 In the extraction of vanadium from titania-rich slag, the aim is to form sodium aluminosilicate, which can be leached to separate vanadium and titanium from impurities.…”

“…In extractive metallurgy, soda is added to the smelting process to control the viscosity and remove the impurities as slag 5,6 . Na 2 O fluxing in the form of Na 2 CO 3 can improve the recovery and kinetics of iron separation from SiO 2 ‐Na 2 O‐TiO 2 slag that is titania‐rich during the carbothermic reduction of ilmenite 7,8 . The formation of soluble sodium compounds is crucial in numerous metal extraction processes 9,10 .…”