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ArticleName Spatial particle distribution during Stokes sedimentation of alumina in high temperature concentrated suspension-electrolyte for aluminium production
DOI 10.17580/tsm.2018.02.05
ArticleAuthor Yasinskiy A. S., Polyakov P. V., Yushkova O. V., Sigov V. A.

School of non-ferrous metals and material science, Siberian federal university, Krasnoyarsk, Russia:
A. S. Yasinskiy, Senior Lecturer of a Chair of Metallurgy of Non-Ferrous Metals, phone: +7-983-169-78-09
P. V. Polyakov, Professor, Consultant of a Chair of Metallurgy of Non-Ferrous Metals
O. V. Yushkova, Head of Laboratory of V. S. Biront Chair of Metal Science and Thermal Processing of Metals
V. A. Sigov, Master’s Degree Student of a Chair of Non-ferrous Metals Metallurgy


Our paper researches the behavior of high-temperature electrolyte suspensions in liquid metals production (in particular aluminium) and demonstrates new experimental data that explain some features of sedimentation in such systems. The experiments were carried out at 700 оC on the KF – AlF3 – Al2O3 suspension system. The local concentration of particles is determined as a function of the vertical coordinate and time with different volume fraction of particles in the suspension (φ). The transition of the first type of sedimentation to the third type for a system with the volume fraction φ = 0.24 was identified. An uncharacteristic type of sedimentation was observed when φ = 0.28. It is expressed in a gradual increase of φ with the vertical coordinate (z) without shocks, inherent for the transition from the settlement zone to the sediment. When φ = 0.32, the z – dependence indicates a hindered sedimentation, the value of  is close to the maximum packing fraction (φm), which corresponds to an infinitely large suspension viscosity. Dependence of the average particle size on z for systems with different compositions was investigated on micrographs of solidified samples. Sedimentation at low Reynolds numbers is significantly hindered in the part of the disperse system that is located near the wall that is bounding it. With a decrease of an average particle size and polydispersity, φm decreased as well, which is accordance with literature data. It was established that φm strongly depends on the presence of a rigid wall. Based on the obtained results, we can assert that the decrease in the anode — cathode distance (ACD) is a very important direction in development of suspension electrolysis technology with vertical electrodes, and should be set in the 5 < ACD < 15 mm range in order to drop energy consumption. The solid phase volume fraction in the KF – AlF3 – Al2O3 system can then be set from 0.28 to 0.32, depending on the established ACD. Under such conditions, one should expect suppressed sedimentation and uniform current distribution.
Our investigation was carried out with the financial support of the Russian Foundation for Basic Research, the Government of Krasnoyarsk Region, Krasnoyarsk regional funds for the support of scientific and scientific and technical activities within the scientific project No. 16-43-240781.

keywords Aluminium, alumina, suspension, settlement, sedimentation, cryolite melt, low temperature electrolysis, particle distribution, non-newtonian fluids, Stokes regime

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