STUDY OF THICKENING AND WASHING KINETICS OF RED MUDS FROM LOW-SILICA BAUXITES

The PURPOSE of the article is to study the effect of the main parameters on the kinetics of thickening and washing processes of red mud from low-silica bauxites. METHODS. To study the kinetics of red mud pulp thickening the control method of the pulp level was used in the settling process. The countercurrent washing was studied according to a specially developed method taking into account the sorption properties of the dispersed phase. The parameters of the decanting countercurrent multiphase washing were calculated using the equations derived on the basis of the solution of the system of balance equations. RESULTS. The thickening and washing kinetics of red muds from low-silica bauxites is studied. Consideration is given to the effect of the main parameters on the loss of valuable dissolved matter under the countercurrent washing of red muds and the formation of precipitation zones. The study of the countercurrent decantation washing has showed that a certain washing stage features the maximum value of the clarification rate corresponding to the isoelectric state. The isoelectric state corresponds to the lowest moisture content in the sediment, which is determined by the smallest development of solvate shells of particles in the dispersed phase in the compression zone. The phenomenon of charge exchange of sludge particle surface causes the presence of two zones with relative stability of pulps. CONCLUSION. A method is proposed for calculating the indices of non-closed countercurrent circuits with a complete cycle of multiphase washing in thickening-washing facilities. The nature of the effect of the flow rate of the washing liquid on the dissolved material loss with the finally washed sediment is determined. The influence of red mud pulp dilution on the formation process of condensation zones is studied: it is shown that the average value of R = L:S is (2.2 - 2.4) in the transition zone: 1 for a wide range of initial values R₀ = L: S, it is determined that the increase in Ro leads to the formation of more dense precipitation in the compression zone, while the shortest duration of the period of collective precipitation of dispersed particles corresponds to the isoelectric state of red mud pulps (20 g/l Na₂О_K).

thickening, washing, red mud, decantation, isoelectric state, washing stages

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