A model for solids transport in flighted rotary dryers based on physical considerations

The following paper outlines the development of empirically fitted and pseudo-physically derived compartment models of a flighted rotary dryer with counter current airflow processing solid material. Underloaded, overloaded and design-loaded dryers are considered. Four key parameters are estimated to fit the empirical model to industrial residence time distribution data and common empirical mean residence time/holdup correlations. Utilising the fundamental structure of the empirical model and physical and mechanical properties such as the dryer and flight geometry as well as solids material properties, the number of estimated parameters in the pseudo-physical model was reduced to 2. The experimental data required to characterise and validate the models is discussed. Optimisations to determine the model parameters were undertaken by comparison with an experimental residence time distribution curve for an industrial dryer processing sugar. Simulation of the model using gPROMS®® illustrates model performance. The potential to integrate the solids transport model and a full heat and mass transfer model is also discussed.