Evaluation of Titania-Rich Slag Produced from Titaniferous Magnetite Under Fluxless Smelting Conditions
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https://doi.org/10.1007/s11837-020-04304-3 Ó 2020 The Author(s)
HIGH TEMPERATURE PROCESSING OF COMPLEX ORES
Evaluation of Titania-Rich Slag Produced from Titaniferous Magnetite Under Fluxless Smelting Conditions I.J. GELDENHUYS
,1,3 Q.G. REYNOLDS,1 and G. AKDOGAN2
1.—Mintek, Randburg, South Africa. 2.—Faculty of Engineering, University, Stellenbosch, South Africa. 3.—e-mail: [email protected]
Stellenbosch
Titanium-bearing magnetite ore is generically defined as magnetite with > 1% titanium dioxide (TiO2) and is usually vanadium-bearing. The iron and titanium occur as a mixture of magnetite (Fe3O4) and ilmenite (FeTiO3) with vanadium oxide usually occurring within the solid solution of the titaniumbearing magnetite phase. These ores are currently widely processed in blast furnaces via modified ironmaking processes. Typically, vanadium is recovered as a by-product from the ironmaking process, while the diluted titania slag is stockpiled. Fluxless smelting in a direct-current open-arc furnace is proposed as an opportunity to improve iron and vanadium recovery and potentially unlock the titanium as a slag product. Slags produced from a pilot study are compared to industrial slags produced from ilmenite. The findings from the pilot test show that slag produced under fluxless smelting conditions in an open-arc electric furnace is remarkably similar to industrial ilmenite slags. The test conditions were varied to evaluate the slag and metal composition, and furnace operation, under increasing reducing conditions. The study showed that the slag and metal product was remarkably similar to industrial slag produced from ilmenite.
INTRODUCTION Fluxless smelting of ilmenite to produce furnace slag as feedstock for the pigment industry is a wellestablished industrial practice with extensive installed smelting capacity globally.1–4 Commercial ilmenite smelters produce two products, namely titania-rich slag and a pig iron by-product. In contrast, smelting practices for titaniferous magnetite (or titanomagnetite) recover only iron and vanadium. Vanadium is recovered as a by-product from the ironmaking process, while the titaniabearing slag is discarded as an inconvenient waste stream. In China it is said that about 90% of Chinese titanium resources are associated with magnetite.5 Current practices treat these ores as a complex iron ore. The slag is modified by adding combinations of silica, limestone and even hematite ore to dilute the titania in the slag to overcome process constraints. In blast furnaces, for example, (Received May 10, 2020; accepted July 22, 2020)
high-titania content in the slag can lead to severe operational challenges, such as blocking of tuyeres and hearth build-up due to excess formation of highly refractory titanium carbide phases. Present titanomagnetite processing practices result in large stockpiles of low-grade slags. Economically competitive methods to extract the residual value from the slag dumps have yet to be realised. Numerous technically feasible processes have been proposed, but as th
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