Rotary Dryer

Rotary Dryer:  A continuous moving bed dryer.

Principle: The rotary dryer is a modified form of the tunnel dryer in which the particles are passed through a rotating cylinder. Due to rotation of the cylinder, the material is turned over and drying takes place from individual particles and not from a static bed.

Mechanism of action: The materials to be dried are fed into the dryer through a hopper, when the cylinder rotates the material flows through the shell and hot air is allowed to flow from opposite direction so that the wet materials comes in contact with hot air. Since the cylinder rotates, distance between particles increases due to baffles and the volume of the particles expands. Therefore, hot air can pass through the material. The baffles leave the solid and help the air to pass through the particle, thus improved gas-solid contact is excellent. The dry material is discharged at the lower end of the shell.

Application: The rotary dryer is widely used for drying of granular salts, sugars, crystalline powders, etc.

Advantages:

1. The drying is efficient and rapid because of good contact of gas solids.
2. The drying material can be easily discharged due to gravity.
3. It is used for continuous drying or large scale of any powder or granular solid.

Disadvantages:

1. Liquid particles can’t be dried.
2. Materials must have free flowing nature.
3. Solvent recovery isn’t possible.
4. Too much moist material is hazardous because stick to the shell wall and hopper while panning. As a result hopper may block.