Ural Federal University, Ekaterinburg, Russia:

I. V. Loginova, Professor of a Chair of Metallurgy of Non-Ferrous Metals, e-mail: loginova_irina@mail.ru
A. A. Shoppert, Senior Lecturer of a Chair of Metallurgy of Non-Ferrous Metals, e-mail: andreyshop@list.ru
E. Yu. Kryuchkov, Bachelor of a Chair of Metallurgy of Non-Ferrous Metals, e-mail: evgeny2203@mail.ru

Our paper shows the characteristics of Middle Timan mine bauxites, which differ from the ones, processed at Bogoslovskiy aluminium plant. X-ray phase and chemical analysis of these bauxites made a conclusion about the necessity of their classification as the bauxites of lower quality. Experiment required the preliminary grinding of more than 90% of bauxite with ~75 μm coarseness. Synthetic alkaline-aluminate solution (caustic module 3.3 and 300 g/dm³ of Na₂O) was used as reagent and was obtained in laboratory by dissolution of caustic soda and chemically-pure aluminium hydroxide in distilled water. The experimental concentration required the solution dilution with distilled water. Investigation of Middle Timan bauxite leaching carried out the experiments, where the initial material was mixed with synthetic solution and set into laboratory autoclave Parr (1000 dm³). The pulp was further held in it with the given temperatures and leaching time and was cooled after holding, diluted by two times and filtrated for solution separation from solid residual of leaching. The experimental plan was applied for the optimal parameters of the process. The temperature varied among 180, 210, and 240 ^oC. The time was changed from 30 to 120 min with a step of 30 min. Concentration of reusable solution varied from 190 to 250 g/dm³ with a step of 30 g/dm³. Alumina extraction in solution was the respond function. Results of multifactor experiment were under mathematical processing. On the basis of our obtained equation of multiple regression we made a conclusion about the optimal parameters of the process. Investigation of kinetic regularities of the process and explanation of increased rate of alumina extraction in solution (in comparison with theoretic one) calculated the caused energies of activation of alumina extraction in solution. At the same time, shamosite extraction offered the decrease of leaching temperature. 86% of optimal extraction of alumina is reached with 90 min leaching at the process temperature of 220 ^oC, and concentration of turnover solution of 240 g/dm³. Recommendations were offered to use in the existing technological cycle of the Bayer method at Ural Aluminium Smelter which nowadays uses our investigated bauxite in alumina production technology on use the in work of raw materials of Middle Timan mine.
This work was carried out with financial support of the Government of Russian Federation, contract No. 10.7347.2017/8.9.

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