A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia:

K. L. Zanaveskin, Senior Researcher, Candidate of Chemical Sciences, e-mail: zakon82@mail.ru

The results of a study of the chlorination of various fractions of the quartz-leucoxene concentrate of the Yaregskoye deposit are presented. Comprehensive complementary work has been carried out to study the changes in the chemical and mineral composition of leucoxene grains that occur during their chlorination at a temperature of 850 ^oC and a 5-fold molar excess of carbon. It has been established that under the conditions of the process, the quartz admixture is inert to the action of chlorine, and the chlorination of aluminosilicates does not proceed completely. Chlorination of leucoxene grains proceeds according to the model of a contracting core of a particle of a constant size. During the chlorination process, the reacting core is reduced, leaving a solid inert layer, which mainly consists of quartz. The inert layer prevents direct contact of carbon particles with the TiO₂ surface located inside the grains. The TiO₂ chlorination reaction proceeds through the formation of gaseous intermediates (presumably chlorine atoms) formed on the carbon surface. Gaseous reagents reach the surface of TiO₂ inside the particles by means of their diffusion through the pores and channels of the inert quartz layer. Chlorine atoms enter into recombination reactions, which leads to thea decrease in their concentration when passing through the quartz layer. Having reached the surface of the reacting core inside the leucoxene grains, chlorine atoms interact with TiO₂. As the thickness of the quartz layer increases, the degree of recombination of chlorine atoms increases, and the rate of the TiO₂ chlorination reaction decreases. Upon reaching the critical thickness of the quartz layer, equal to 55 μm, chlorine atoms practically disappear, and the process of chlorination of TiO₂ stops. For this reason, titanium dioxide in the fractions of the concentrate, the grains of which are larger than 110 microns, is not completely chlorinated. Processing of the concentrate of natural grain size makes it possible to achieve the extraction of titanium at the level of 80%. Grinding the grains of the concentrate leads to high losses of TiO₂ with dusty fractions and cannot be used as a stage in the preparation of the concentrate for chlorination. To create an industrial process for the production of titanium tetrachloride in fluidized bed reactors, it is necessary to develop a method that enables to increase the extraction of TiO₂ from the concentrate.
The study was carried out with the financial support of the Russian Foundation for Basic Research within the framework of the scientific project No. 18-29-24187 MK.

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