Drum drier - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes

Drum drier


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


• 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


• 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


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


1. Maintenance cost is higher than spray dryer

2. Skilled operators required


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


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