Agitated dryers give significantly higher drying rates per unit heating area than non-agitated systems such as ovens and tray dryers. This is due to continuous renewal of solids in contact with the dryer’s heated surfaces. In addition, the agitation improves uniformity of the product.
By contrast, due to long drying times, oven or tray drying operations are often allowed to proceed overnight which can impact energy costs and production rates.
The main issue with agitated dryers is the risk of product attrition or generation of too many “fines”. Also, some designs, such as rotary dryers or tumble blenders, can typically accommodate only free-flowing solids as feed material.