Drying of Solids in a Rotary Dryer

Abstract

Experiments were conducted in a batch rotary dryer for obtaining the drying kinetics of a non-hygroscopic material with preheated air as the drying medium. The progress of the drying process was investigated for different temperatures and flow rates of the drying medium, initial moisture content of the solids, and rotational speed of the dryer. The contacting pattern of the same dryer was obtained through Residence Time Distribution (RTD) studies and the variables include rotational speed and inclination of the dryer and feed rate of the solids. The RTD data was subjected to axial dispersion model and axial dispersion number was estimated. Correlations were proposed for mean residence time, hold-up of the solids, and dispersion number. The performance of the continuous dryer was predicted through batch kinetics and RTD, and the predictions were validated with experimental data. 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 in a continuous dryer.

Keywords:

• Continuous drying
• Drying kinetics
• Rotary dryer
• RTD

ACKNOWLEDGMENTS

The author wishes to acknowledge the support of Mr. M. Narasimhulu and Mr. Avaneendra Linga in carrying out the experiments.