FLUIDISED BED DRYER SCALE-UP

Design methods for fluidised bed dryers have developed to the point where reliable scale-up is now possible for most applications. The model underlying the methods is described in terms of its constituent parts, namely a material model and an equipment model. The material model utilises drying data from laboratory tests together with scientifically based rules for predicting the effect of changes in operating conditions and the main design parameters on performance. The equipment model describes the residence time distribution for the system. This paper focuses on continuous well mixed and plug flow units. There are a number of factors which must be considered in scale-up beyond the basic design method. In particular, the feed system, distributor, plenum and freeboard regions can introduce operational differences between the laboratory and full scale units which may adversely affect performance. Guidance is given on these practical considerations.