Chair of Lightweight Metals Metallurgy, Institute of Materials Science and Metallurgy, Federal State Autonomous Educational Institution of Higher Professional Education “Ural Federal University named after the first President of Russia B. N. Yeltsin”, Ekaterinburg, Russia

I. V. Loginova, Assistant Professor, e-mail: loginova_irina@mail.ru
A. A. Shoppert, Post Graduate Student

Research belongs to area of production of alumina on a way of Bayer. It is offered to bring improvements at a decom position stage. Use possibility as a seed material of aluminum sulfate is shown. It is revealed that when using such substance, process can be carried out without use of mixing devices and lower temperatures. It is experimentally established that aluminum sulfate at its addition in alkaline-aluminate solution cooperates with the connected and free alkali therefore aluminum hydroxide with the developed surface is formed. At article the chemical reactions describing possibility of emergence as a result of decomposition of sulfate of aluminum of the centers of crystallization on the basis of particles of hydroxide of aluminum are described. On their surface from supersaturated aluminate solution aluminum hydroxide is intensively besieged. For lack of mixing there is a linear growth of crystals of the hydroxide, bringing to column structure. The type of such structure differs from industrial option of receiving alumina. It is revealed that at increase in amount of the added salt of aluminum the number of the centers of crystallization raises. It is shown that application of such seed intensifies process of decomposition alkaline aluminate solutions. The best indicators of decomposition of solution are reached at concentration of alkali of 130 g/l and temperature of 35 ^oC. The percent of decomposition received in experiences reached 67.7% during carrying out process of 24 h. In industrial conditions the percent of decomposition makes 48–52% during 48–60 h. Unlike industrial technology possibility of an exception of mixing operation of solution and use of a turnaround seeding is created. The granulometric structure of the dropped-out precipitation was measured by means of the analyzer of the size of particles by Mastersizer 2000. Analysed a specific surface of the alumina received from a firm phase, a method of a thermal sorption of argon. The physical and chemical analysis of the received alumina allows carrying it to alumina of sandy type with the developed specific surface which size makes more than 130 m²/g.

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2. Roelof Den Hond, Iwan Hiralal, Ab Rijkeboer. Alumina yield in the Bayer process past, present and prospects. Light Metals. 2007. Vol. 1. pp. 37–42.
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