Drying is an essential process that involves transferring heat to remove moisture from wet products. Common drying methods include vacuum tray drying, freeze drying, rotary drum drying, spray drying, and pneumatic conveyor drying. Vacuum tray drying works by removing moisture through a vacuum, while spray drying uses nozzles to spray liquid droplets into a heated gas stream to evaporate water. Freeze drying preserves biological activity by freezing and then applying a vacuum to directly sublimate ice. Rotary drum dryers use a heated, rotating cylinder to dry materials, and pneumatic conveyor dryers suspend particles in a heated air stream to dry reasonably solid feeds.

1. Drying Process

2. Drying:
Drying is an essential component of product formulation. It
basically involves the transfer of heat to a wet product for
removal of moisture.
Most of the biological products of fermentation are sensitive
to heat, and therefore require gentle drying methods.

3. There are numerous benefits of utilizing drying.
The cost of transport is lowered as redundant weight like
water and solvent weight is removed.
The handling and packaging of the material is simpler and
storage is also more convenient in a dry state.

4. Some of the dryers used nowadays are as follows:
1. Vacuum Tray Dryer
2. Freeze Drying
3. Rotary-Drum Dryers
4. Spray Dryers
5. Pneumatic Conveyor Dryers

5. Vacuum tray dryer:
I. Vacuum tray dryer Vacuum tray dryer works by removing
moisture through a vacuum created .
II. An air tight environment is then created, with the oven
connected to a vacuum pump for the creation of a pressure
free environment.
III. The product to be dried is kept in a tray, which is then put
in the oven for the drying process.
IV.The water vapor that is produced from the drying process
is sent into the condenser of the vacuum oven and the dried
product is then removed from the trays.

7. Spray drying:
Spray drying is used for drying
large volumes of liquids.
In spray drying, small droplets of
liquid containing the product are
passed through a nozzle directing
it over a stream of hot gas.
The water evaporates and the
solid particles are left behind.

8. Freeze-drying:
Freeze-drying or lyophilization is the most preferred
method for drying and formulation of a wide-range of
products—pharmaceuticals, foodstuffs, diagnostics,
bacteria, viruses. This is mainly because freeze-drying
usually does not cause loss of biological activity of the
desired product.
Basically it is constituted of four steps:
1. Pretreatment
2. Freezing
3. Primary Drying
4. Secondary Drying

10. Rotary Drum Dryer
1. Rotary Drum Dryers are made up of large rotating
cylindrical tube with a slight slope using the gravity force
for material transfer.
2.The water is removed by the steam-heated surface of the
rotating drum.
3. The inner wall of the dryer is usually equipped with a
series of internal fins lining.
4. A dryer can also consist of multiple shells to be utilized
in a more compact space.

11. 5. Rotary Drum dryers can be used for temperature stable bioproducts.
The material is in contact with the heating surface for 6-15 seconds.

12. Pneumatic Conveyor Dryers
The idea of pneumatic drying is dry reasonably solid feed
(moisture level below 35-40 %) even further.
Powders or granular materials are dried while suspended in
a stream of heated air
Pneumatic drying requires reasonable solid feed as
particles. Heated air is conveyed to particles and removes
moisture.
The blower blows the air which transports feed particles
into the silo. Temperature is adjusted by heater.