Principle: If a gas is allowed to flow upward through a bed of solid particle at a velocity greater than the settling velocity of the particle, particle partially suspended in the gas stream.
The resultant mixture behaves like a liquid and the solid are said to be fluidized.
Each individual particle is surrounded by drying gas with the result that drying take place in much shorter period.
It also provides uniform condition of temperature, composition and size distribution.
Working:
In fluidized bed dryer air is introduced by fan situated in the upper part of dryer.
Air is heated by heater to required temp and air flow is adjusted by recirculation control and air is filtered by filter bags to prevent the passage of fine particles to dryers, then air is passed to the bottom to flow through the bed of material to be dried.
They are available in different capacity ranging from 5 kg to 200 kg and drying time is 20 to 40 mins.
Use:
Used in granulation process for tablet preparation
It is used in coating.
Used for drying of filter cake.