REC «Mekhanobr-Tekhnika» (St. Petersburg, Russia):

Ustinov I. D., Supervisor of the Research Training Center, Doctor of Chemical Sciences, Professor, gornyi@mtspb.com

St. Petersburg Mining University (St. Petersburg, Russia):
Baldaeva T. M., Postgraduate Student, baldaeva.t.m@gmail.com

Loose material vibratory size classification processes generalizing description has been performed in science terms of thermodynamics, primarily, with respect to mineral raw materials. The proposed approach is based on applicability of Gibbs thermodynamic potential to loose granular systems. The examples are provided with regard to calculations of classification process total energy, enthalpy and entropic increment. The calculations are based on measured process parameters and fundamental properties of dry granular media, as dry friction, true density and loose density. All these three parameters are measurable, and are taken account of quantitatively in the proposed approach. This approach is not applicable to systems, in which loose material is in aggregated state, e. g., when exposed to electrostatic forces. The system in question includes a screen, separated material, gravitational field and atmospheric air; material mass, machine mass and elastic properties of separated material particles do not change, initial and final temperatures practically do not change, either. It was established, that the system screen — separated polydisperse raw material in a gravitational field is subject to non-dissipative loss of energy, uncontroversial to the second law of thermodynamics. Thermodynamic picture of loose material separation under vibration in principle unalters even when separating plate as sieve is not present. This phenomenon as size segregation almost without exception is the case in oversize zone in the first half of vibratory screen from charging point, when material is loaded on screen and is transported in thick layer. In the phenomenon of vertical vibratory segregation of polydisperse material the role of a set of «sieves» is fulfilled by larger particles sifting smaller ones down to undersize. The developed analytical tools may be used as an evaluating factor in design of various screening media.
The authors are deeply grateful to Prof. I. I. Blekhman and academician of the Russian Academy of Sciences L. A. Vaisberg for constructive criticism and great help in the preparation of the article.
The study was performed with the aid of the Russian Science Foundation Grant (Project No. 17-79-30056).

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