Abstract. The dissolution kinetics of potassium sulfate dissolved in water under pneumatic mixing has been investigated. The mass transfer coefficients were determined by the experiments, as well as on the basis of the local isotropic turbulence theory. The ratio between theoretical and experimental data was found to be satisfying that allows to determine the theoretical mass transfer coefficient to calculate the mentioned process.

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The dissolution process of potassium chloride particles in the apparatus with two-blade mechanical stirrer was investigated and the mass transfer coefficient was determined. The experimental results were generalized by criterion dependence. The independence of the mass transfer coefficient from the solid particles diameter was confirmed. A countercurrent process of potassium salt dissolution in two apparatuses with a mechanical stirring was considered. A mathematical model for countercurrent dissolution was developed and the efficiency of this process was determined.

Abstract.1 The dissolving process of benzoic acid polydisperse mixture in the gas-liquid flow has been examined. On the basis of criterial dependence and the theory of local isotropic turbulence the mass-transfer coefficient was determined experimentally and theoretically and their values were compared. Theoretical calculation of polydisperse mixture dissolution was performed during periodic dissolution under variable driving force. Theoretical and experimental results were compared.

Filtration drying of grinded sunflower stems as the unit operation of the technological line for solid biofuel production has been proposed. Theoretical aspects of heat transfer processes during filtration drying have been analyzed. The effect of the drying agent velocity increase from 0.68 to 2.05 m/s on the heat transfer intensity has been established. The values of heat transfer coefficients have been calculated on the basis of the thin-layer experimental data and equation . Calculated coefficients for grinded sunflower stems have been correlated by the dimensionless expression within Reynolds number range of and the equation has been proposed to calculate the heat transfer coefficients, that is important for forecasting the heat energy costs at the filtration drying equipment design stage.