Research of the processes of reductive-nitrating roasting of perovskite concentrate with the addition of SiO2

The paper presents the results of a study on the reducing-nitrating roasting of perovskite concentrate from the Afrikanda deposit to convert titanium into its nitride, which can then be subjected to low-temperature chlorination (300–500 °C) with the extraction of titanium in the form of TiCl₄. The material composition of the perovskite concentrate has been clarified. A thermodynamic assessment of the equilibrium compositions in the CaTiO₃-SiO₂-C-N₂ system in the temperature range of 1250–1350 °C has been carried out. The phase compositions of the roasting products obtained at the specified temperatures with different amounts of SiO₂ additive used to bind CaO formed during perovskite nitriding have been studied. It has been shown that the maximum conversion of titanium into its nitride is achieved at temperatures above 1300 °C. At the same time, an increase in the amount of SiO₂ additive in the batch also promotes the formation of the oxynitride phase. When SiO₂ is added in the molar ratio CaO:SiO₂ = 3:1, unreacted perovskite remains in the calcination product. In addition, the product contains residual calcium oxide, and the silicate phase consists of CaO·SiO₂ and 2CaO·SiO₂. The maximum transfer of titanium to the nitride phase is achieved at a molar ratio of CaO:SiO₂ = 1:1. Under these conditions, CaO·SiO₂ will predominate in the silicate phase.