Drum drier

Principle

A heated hallow metal drum rotates on its longitudinal axis,
which is partially dipped in the solution to be dried.

The solution is carried as a film on the surface of the
dryer &

Dried to form a layer. A suitable knife scraps the dried
material, while drum is rotating

Construction

• It consist of a horizontally mounted hollow steel drum of
0.6 – 3.0 meters diameter & 0.6 – 4 meters in length, whose external
surface is polished.

• Below the drum, feed pan is placed in a such way that the
drum dips partially into the feed.

• On one side of the drum a spreader is placed & on
other side a doctor’s knife is placed to scrap the dried material

• A storage bin is placed connecting the knife to collect
the material

Working                

• Steam is passed inside the drum. Drying capacity is
directly proportional to the surface area of the drum. Heat is transferred by
conduction to the material

• Drum is rotated at a rate of 1- 10 revolutions per minute.
The liquid material present in the feed pan adheres as a thin layer to the
external surface of drum during its rotation

• Material is completely dried during its journey in
slightly less than one rotation. the dried material is scrapped by knife, which
then falls into a storage bin. The time of contact of the material with the hot
metal is 6-15 seconds only

Advantages

1. Drying time is less only few seconds. Hence, heat
sensitive material can be dried

2. Less space as compared to spray dryer

3. Rates of heat & mass transfer are high

4. Product obtained is completely dried & is in the
final form

Disadvantages

1. Maintenance cost is higher than spray dryer

2. Skilled operators required

Uses

It is used for drying solutions, slurries, suspensions

etc. & also drying of products like;

1. Milk product

2. Starch product

3. Ferrous salt

4. Suspensions of zinc oxide & kaolin

5. Antibiotics

6. Yeast & pigments

7. Malt & glandular extracts

8. Insecticides

9. Calcium & barium carbonates