St. Petersburg Mining University (St. Petersburg, Russia):

Baldaeva T. M., Postgraduate Student, baldaeva.t.m@gmail.com

The extensive studies, performed in the area of granular materials applied mechanics in recent years, including the studies on polydisperse bulk materials segregation and rheological properties, suggest that preliminary separation of fine size fractions may promote vibratory screening efficiency increase, resulting from directed changes in bulk material mass physical properties. The paper describes the results of the laboratory studies, performed on mineral coal sample of –5+0 mm size through experiments with observation of fine size fractions preliminary separation effect upon vibratory sieve classification efficiency. The experiments were performed on a vibratory analyzer with horizontal orbital vibrations, equipped with squaremesh sieves with diameter of 200 mm. The sieves’ vibrational frequency was 16.7 s^–1. The starting mass of loaded coal sample was 400 g, which provided for formation of thick layer of material on the sieve. Vibratory classification of material was conducted in batch mode on sieve with 2.5 mm mesh size and in sequential mode on sieves with 2.0 mm and 2.5 mm mesh size. The tests showed that sequential vibratory classification from small size fraction to coarse size fraction permits to noticeably increase overall classification efficiency in –2.5 mm size fraction over a reasonable period of time. The results obtained on the coal sample were verified by the tests in sequential fine dry screening of finely crushed apatite ore and coppernickel ore of –2.0 mm size on sieves of 0.5 and 0.63 mm mesh size, demonstrating stable increase in classification efficiency by 4–5 %. Notice also that this approach is of a practical interest first of all for light-weight minerals that are classified only in thick material layer.
The studies were performed with the aid of the Russian Science Foundation Grant (Project No. 17-79-30056).

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