METHOD OF PREDICTING TEMPERATURE OF FINES CONTAINING FREE AND BOUND MOISTURE, IN CONVECTIVE DRYING PROCESS Russian patent published in 2013 - IPC F26B25/22 

FIELD: heating.

SUBSTANCE: method of predicting the temperature of fines containing free and bound moisture in the convection drying process is characterised in that it comprises a preliminary derivatographic analysis of fines, on the basis of which the critical moisture content is determined, corresponding to termination of removal of all free moisture and start of the period of removal of the bound moisture; then for the period of removal of the bound moisture a diagram of dependence of the degree of heating of the dry part of the material on the degree of dehydration of the material is made, and by mathematical treatment of this diagram the value of the coefficient of the equation of temperature curve of drying t is determined; then the temperature of the material in the process of convective drying is determined: during removal of free moisture its value is taken equal to the temperature of "wet-bulb thermometer", which is defined by I-d-diagram of humid air, depending on the thermodynamic parameters of the air entering the drying chamber, during removal of bound moisture the temperature of the material at a fixed moisture content is determined by calculation according to the equation of the temperature drying curve: $$T=T_w+\left(T_d-T_w\right)\cdot \left\{\frac{1}{m}\left[{\left(\frac{U-U_c}{U_{cr}-U_c}\right)}^{m+1}-1\right]+\frac{m+1}{m}\left(\frac{U_{cr}-U}{U_{cr}-U_c}\right)\right\}\left(1\right)$$ (1), where T is absolute temperature of the material in the drying process, K; T_d T_w are absolute temperatures of the air entering the drying chamber, measured, respectively, on a dry- and wet-bulb thermometers, K; U_cr is critical moisture content corresponding to complete removal of free moisture, kg of moisture/kg of dry matter; U_c is moisture content of the product which is in equilibrium with the air entering the drying chamber, kg of moisture/kg of dry matter; U is a fixed moisture content of the product at a given moment of drying, kg of moisture/kg of dry matter; m is an empirical coefficient which is not dependent on the modes of drying and which is a constant value for each material. Knowing the value of the material temperature T in the process of drying the predicted temperature curve can be made.

EFFECT: method of prediction enables prior to implementing the drying process on the basis of laboratory analysis to predict the temperature of heating of fines in the process of drying, and to choose reasonably the optimum temperature mode of drying with sufficient high accuracy and reliability, and to reduce the number of experiments in scientific studies of the kinetics of drying.

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