Definition
Drying is defined as the removal of liquid from a product usually with application of heat.
Equipment used for the purpose of drying are called “Dryers”.
Drum Dryers.
Also known as: Roller Dryers, Film Dryers.
Principle:
It's an indirect type, continuous moving bed dryer.
The suspension or slurry to be dried forms a thin layer around the surface of the roller and gets dried.
Suitable for solutions with thick consistency.
Construction:
It consists of one or two horizontally mounted hollow drum(s) made of high grade cast iron or stainless steel, a supporting frame, a product feeding system, a scraper, storage bin or conveyors, drum speed regulator and other auxiliaries.
Typical structures of gle and double drum dryers are as shown in following diagram.
The diameter of typical drums ranges from 0.5 m to 6 m and the length from 1 m to 6 m.
Working:
The liquid to be dried is placed in a shallow pan.
The hollow rotor is mounted in the shallow pan with liquid.
As the rotor starts to move the liquid forms a thin film on the surface of the rotor.
The rotor can be heated by passing steam inside the rotor.
The liquid forming film gets dried quickly, the process can also be fastened by blowing air on the film.
The film is spread uniformly with the help of a spreader attached to the assembly.
The dried product is scrapped by using a scrapper.
The product is collected in a product bin.
Uses:
Used to dry the products of thicker consistency.
e.g.
Milk products.
Kaolin.
Antibiotics.
Yeast.
Barium carbonates etc.
Advantages:
Less drying time.
Useful for thermolabile substances.
Occupies a lesser place.
Disadvantages:
Higher investment.
Higher maintenance cost.
Skilled operators needed.
Commonly Asked Questions.
With a well labelled diagram describe construction and working of Drum Dryers.
Write a short note on the Drum Dryer.