Modelling of particulate drying in theory and practice

The range of theoretical models used by SPS for the design and analysis of dryers, especially dispersion dryers, is reviewed. Different levels of complexity are appropriate at different stages of the design process. Models should use an appropriate level of rigour for the available data and the required purpose of the results. Scale-up from experimental design curves often yields better results in practice than a highly complex model requiring many parameters, and the type of drying kinetics measurements required also depends on the type of model to be used. Models at four different levels are presented in general terms and for a number of major types of dryers. Significant developments in the SPS methodology for fluidised bed, pneumatic conveying and cascading rotary dryers are noted. It is also important to consider the dryer in the context of the overall process flowsheet.