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