Beneficiation of fluxed titaniferous slag to a marketable titania product using the modified upgraded slag process

Abstract

Smelting production of a limestone-fluxed titaniferous slag with low MgO content for subsequent beneficiation using the modified Upgraded Slag (UGS) process was investigated, with the aim of producing a marketable titania product. Smelting of titaniferous magnetite (titanomagnetite) with a carbon reductant and limestone flux was conducted in a water-cooled copper crucible in an iron-suscepting induction furnace under argon. The resulting titaniferous slag contained high residual iron (from the susceptor and incomplete iron reduction in the titanomagnetite), which caused crystallization of an ulvospinel. The slag was beneficiated using the modified UGS process, an industrial roast–leach process used for beneficiation of low-titania slag to a feedstock suitable for production of titania pigment. The upgraded product contained 90.5 mass% TiO₂, with a recovery of 83%. Although the TiO₂ grade met the feedstock specification for pigment production via the chloride route, SiO₂, Al₂O₃, CaO, and Cr₂O₃ concentrations exceeded the specification and the particle size distribution was too fine.