Abstract: The process of drying particles can be divided into three stages, i. e. heating of particles, evaporation of water content at a constant rate and drying at a lower rate of evaporation. The drying processes of different screen fractions of particles are very much alike, but their rates of evaporation are quite different. The finer the particles are, the faster the rates of drying will be, because finer particles have relatively larger surface areas than coarser particles when their volumes are the same,The rate of drying increases with the increaseof temperature. Therefore, it is advisable to dry different screen fractions of particles separately. In order to get a better distribution of the drying medium, it is desirable to make the temperature at the inlet higher than that at the outlet of the dryer. A downstream of air circulation in the dryer is feasible.