Studies on drying kinetics of solids in a rotary dryer

Experimental and theoretical investigations on drying of non-hygroscopic material were conducted in a rotary dryer with preheated air as the drying medium. The progress of the drying process was experimentally investigated batch wise and under continuous conditions for different temperatures and flow rates of the drying medium, rotational speed and inclination of the cylinder, and initial moisture content of solids. The experimental product moisture content from continuous drying process was satisfactorily compared with predictions based on axial dispersion model. The drying rate was found to increase with increase in either rotational speed of the dryer or temperature or flow rate of the drying medium. It decreases with increase in either initial moisture content of the solids or solids holdup. The study shows that the drying kinetics coupled with residence time distribution function for the flow of the solids satisfactorily predicts the moisture content of the solids in the product.