Siberian Federal University, Krasnoyarsk, Russia:

O. V. Yushkova, Senior Lecturer, Department of Metals Science and Heat Treatment of Metals named after V. S. Biront, Head of Laboratory, Candidate of Technical Sciences, e-mail: olga_yushkova_1954@mail.ru
A. S. Yasinskiy, Associate Professor, Department of Non-Ferrous Metallurgy, Candidate of Technical Sciences
P. V. Polyakov, Professor, Department of Non-Ferrous Metallurgy, Doctor of Chemical Sciences

“United Center for Research and Development” LLC, Moscow, Russia:

V. V. Yushkov, Head of Procurement Department

The material consisting of alumina and frozen bath is used nowadays to cover the anodes. It is known that the cover material:
– protects the anode against the oxidation by air and carbon dioxide;
– contributes to the thermal insulation of the top of the cell;
– traps volatile fluorides (HF, NaAlF₄ and AlF₃).
The effect of mechanical activation of alumina being a part of cover material on its physical-mechanical properties is studied. Mechanical activation is known to increase the internal and surface energy of the alumina particles by performing the dissipation work. It is accompanied by the structure defects (dislocation and vacancies) appearance. Cover material with the G-00k (smelter grade) alumina of the Achinsk Refinery and the Nikolaevsk Refinery before and after the dry scrubbers and the frozen bath in a ratio (1:1) was used in this work. Alumina was activated in periodic (M-3 and R-400) and continuous (AGO-9) mills. Physicomechanical properties (namely angle of repose, dusting index, particle size distribution, bulk density, funnel flow time) were determined for alumina and the cover material. The angle of repose increases from 30 up to 45–47 degrees after mechanical activation. It is proposed to use the cover material, which includes secondary alumina after mechanical activation and frozen bath in the ratio (1:1). It is shown that the mechanical activation of alumina:
– increases the angle of repose, which contributes to the reduction of a heat loss and the anode oxidation rate;
– decreases the material dusting index due to the aggregation of particles, which contributes to the exclusion or reduces dusting, bulk density and heat losses by decreasing the cover material thermal conductivity.

The alumina mechanical activation is proved to be a promising solution.

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