Analysis of the Drying Process of Granular and Powdered Materials During the Falling Rate Period

Abstract

The drying rate curves of granular and powdered materials for various drying methods are shown in Figs. 1～4. It is clear from these figures that the falling drying rate of granular material is proportional to the water content of the material. It is also shown that the temperature gradient can be neglected for the granular material which has a diameter below 2～3mm. According to these facts, we have discussed the relation between the water content and the material temperature during the falling rate period under stationary drying conditions in Chap. I. In Chap. II, we have discussed the relations among water content, material temperature and air temperature under non-stationary conditions which take place in a continuous (parallel- or counter-current flow) dryer. The drying rate and the drying time in the continuous adiabatic dryer can be easily calculated by using these relations. The application of this calculation to the dryer design is discussed in Chap. III.