Fluidized bed dryers, their
construction, working, FBD finger bags, finger bag MOC and their features and
application in pharmaceutical manufacturing.
Drying in
pharmaceutical manufacturing is the
removal of water and other liquid solvents from the granules or other materials
by heat and a current of air. Fluidized bed dryer is used to dry the granules in pharmaceuticals using FBD finger
bags.
1. In fluidized bed
dryer hot air is passed at high pressure through a perforated bottom of the
container containing granules to be dried.
2. The granules are
lifted from the bottom and suspended in the stream of air this condition is
called fluidized state.
3. The hot air is
surrounding every granule and dries them completely. Therefore, the granules
dry equally.
Construction:
The dryer is
generally made up of stainless steel. A removable bowl is attached at the base
of the dryer that is used for loading and unloading of material. The stainless
steel bowl has a perforated base of a wire mesh supporting for material that is
being dried. A fan is available at the top of the circulating hot air. Fresh
air enters; filters and heat exchange are connected serially to heat the air to
the required temperature.
Working:
1. The wet granules
to be dried are placed in removable bowl. The bowl is pushed into the fluidized
bed dryer.
2. Fresh air passes
through the pre-filter, which subsequently get heated by passing through a heat
exchange.
3. The hot air flows
through the bottom of the bowl simultaneously fan is allowed to rotate.
4. The air velocity
is increased with time. When the velocity of the air is more than the settling
velocity of the granules, the granule remains partially suspended in the air
stream.
5. After some time, a
point of pressure is reached at which frictional drag on
the particles is equal to the
force of gravity.
6. The granules rise
in the container because of high velocity of air (1.5 to 7.5 meter per minute)
and later fall back in a random boiling motion. This condition is said to be
fluidized state. The gas surrounds every granule to completely dry them.
7. The air leaves the
dryer by passing through the bag filter. The entrained particles remain attached
to the inner surface of the finger bags. The bag is shaken periodically to
remove the attached particles.
FBD Finger Bag:
Fluidized bed dryer
filter bag are made up of different type of superior quality of fabrics, as per
requirement of material involving in drying.
Different types of
fabrics are:
1. Antistatic
2. Polypropylene
3. Stain
The manufacturing of
fluidized bed dryer filter bag depends on required factor like retention
micron, static change and air permeability. Fluidized bed dryer filter bags are
cost efficient and durable, as those are manufactured according to the
specification and are regularly tested to meet standard quality. FBD finger
bags have finger like structures to increase their surface area and efficiency.
Drying process in FBD depends upon the MOC of the finger bags. Finger bags are
constructed by a combination of anti static polymer, nylon fabric and cotton
fabric.
Application:
● Pharmaceutical
industry
● Chemical industry
● Agricultural
industry
● Processing industry
Features
of fluidized bed dryer finger bag:
● Excellent
resistance to wear and abrasion
● Extremely durable
construction
● High flow rate
combination with good particle retention
● Increased surface
area