Mechanically Agitated Fluidized Bed Drying of Cohesive Particles at Low Air Velocity

The drying of micrometer-sized, cohesive particles belonging to the group C type materials according to Geldart's classification is always challenging. An agitated fluid bed dryer (AFBD) of pilot-scale capacity was designed to study the effect of the type of agitator and its speed, gas velocity, and inlet temperature and feed loading on the hydrodynamic performance of the AFBD. Key hydrodynamic parameters such as pressure drop have a profound influence on determining the fluidization characteristics. The pressure drop across the AFBD system was expressed in terms of flow coefficient, xi, which can be conveniently used as a design parameter. The choice of agitator has an even greater influence on the drying kinetics and the results have been summarized, paving the way for a more efficient spiral agitator of the helical ribbon type.