TRANSPORTATION AND AXIAL DISPERSION OF SUGAR IN FLIGHTED ROTARY DRYERS

Model based control of rotary dryers relies on accurate modeling of the heat and mass transfer between air and solids and the transport of solids through the dryer. The need to improve control of these units is expected to increase with increased quality demands placed on Australia’s sugar industry. Although many models are available for predicting the residence time in rotary dryers, their reliability has been limited by the lack of industrial data for validating these models. This work presents experimental data for the residence time of solids in an industrial sugar dryer. Tracer studies have been used to determine residence time distributions. Axial dispersion and mean residence times are examined under different operational conditions. Reactor models commonly used to reproduce the experimental residence times are discussed. The importance of sugar residence time distributions on dryer performance is also discussed