In tray dryers, the process of drying includes a combination of conduction, convection and radiation process. In fluid bed dryer, the overwhelming majority of the drying takes place through convection drying only. In fact, fluid bed drying is the best alternative to tray drying thanks to the following features:
Principle of Drying in Fluid Bed Dryers
Wet product is held in a product container with mesh screen and an air distribution plate at the bottom. Hot conditioned air passed directly through the product fluidizing the wet mass in to the expansion chamber. This allows hot air to come in contact with the surface of the wet granules, thereby effectively removing the moisture/solvent. As the wet particles move up in the expansion chamber that has relatively larger area, air loses its velocity and thus the partially dried/dried particles come back to the product container and the moist air with dust moves up to the filter housing. Filter bag arrests the fines and the moist air is exhausted out.