Saint-Petersburg Mining University, St. Petersburg, Russia:

O. A. Dubovikov, Professor, Department of Chemical Technologies and Energy Carrier Processing
V. N. Brichkin, Head of Department of Metallurgy, e-mail: kafmet@spmi.ru
A. D. Ris, Post-Graduate Student, Department of Metallurgy
A. V. Sundurov, Post-Graduate Student, Department of Metallurgy

It is demonstrated that activation of minerals of kaolin and chamosite series is based on their thermodynamic unsteadiness with reference to thermal dissociation with formation of amorphous silicon oxide and aluminium as primary products followed by generation of mullite and crystalline modifications of oxides as steady final products. This provides a technological basis of partial silicon and aluminium separation along with rising the silicon module of thermochemical treatment products until the values, acceptable for alumina production by alkaline methods. Adduced are the diagrams of kaolin and chamosite phase transformation on thermal treatment as well as design dependences of the silicon module value of thermochemical processing products upon mullitization degree of the products and the value of silica chemical extraction into alkaline solution. Listed are the results of experimental study of chemical and phase composition of chamosite samples with different iron oxidability level. It is established an essential difference in activity of natural chamosite forms and the probes after heat treatment. It is shown that chamosite oxidability level, temperature and duration of heat treatment resulting in differences of mullitization degree of the products, as well as indices of silica chemical extraction on hydrochemical treatment of activated materials are the significant factors of separation of silicon and aluminium oxides. Proposed are the techniques of thermochemical activation of low-grade bauxites, containing minerals of kaolin and chamosite groups, which are realized in the form of the principal schematic apparatus and process diagram, possessing the required adaptation rate to alumina manufacturing by alkaline methods.

The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577 dated April 26, 2018 on providing the grant for conducting fundamental scientific and exploratory researches.

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