4. PRINCIPLE
• Hot air is passed at high pressure through a
perforated bottom of the container containing
granules to be dried
• The granules lifted from the bottom and
suspended in the stream of air
• This condition is known as fluidised state
• The hot air uniformly dry the granules
5. CONSTRUCTION
• Two types of bed dryers available
• 1.vertical fluidised bed dryer
• 2.horizontal fluidised bed dryer
• Materials: stainless steel or plastic
• A detachable bowl placed at the bottom
used for charging and discharging
bowl has perforated bottom with a wire
mesh support for placing materials to be
dried
6. • A fan mounted on the upper part to circulate
hot air
• Fresh air inlet, prefilter and heat exchanger
are connected serially – to heat the air to the
required temperature
• Bag filters placed above the drying bowl to
recover fines
7. Working
• The wet granules to be dried are placed in the
detachable bowl
• The bowl is pushed in to the dryer
• Fresh air is allowed to pass through a prefilter
• Which is subsequently get heated by passing
through a heat exchanger
• The hot air flows through the bottom of the
bowl ,simultaneously fan is allowed to rotate
8. • The air velocity is gradually increased
• When the velocity of air is greater than
settling velocity of granules, the granules
remain partially suspended in the gas stream
Fluidised state
during this period hot air surrounds each of the
granules and absorb moisture from the
granules so we get completely dried product
9. • The air that carries moisture and passes
through bag filters where entrapped particles
are adhered on inner surface of the bag filter.
• We can remove the entraped particles simply
by shaking .this can be done periodically
• The dried product can be remove by taking
out the bowl
10. uses
• Used for drying granules in the production of
tablets
• This type of equipment is also used for mixing
and granulation
11. Advantages
• The residence time for drying is about 20-40
minutes compared to tray dryer becoz tray
dryer requires 24 hrs .
• Handling time is also short.it is 15 times faster
than tray dryer
• drying capacity:5 - 200 kg per hour .so spray
dryer is available in different size and capacity
12. • The drying containers are mobile handling the
equipment is eazy and labour costs involved
are very low
• Thermal efficiency is 2-6 times greater than
tray dryer
13. disadvantages
• Possibility of product loss
• Drying sticky materials is difficult
• Electrostatic charges may develop during
drying
