rotary dryer


The rotary dryer also known as tumbling dryer is an equipment employed to minimize the moisture content of a feed material by bringing it in direct contact with a heated gas. It consists of an inclined long drum or cylinderical shell often fitted with internal flights or lifters; rotary dryer rotated slowly upon bearings through which the material to be dried flow with a tumbling/cascading action in concurrent (for heat sensitive materials) or counter-current flow with the heating air or gases. The movement of the material is due to combined effect of inclination of the shell to the horizontal and the internal tumbling action or mechanical hammer crusher turn over thus the name tumbling dryer. The nature of the feed determines the directions of gas flow through the cylinder and it is relative to the solid. This drying equipment can also perform batch or continuous processing of the wet feed.

how a rotary dryer works

The material held up time is determined by;

The speed of rotation.
The angle of inclination.
The air velocity.
Based on the method of heat transfer, http://strommashina.com rotary dryer can be classified into;

Direct-heated rotary dryer.
Indirect- Direct rotary dryer.
Indirect rotary dryer.
Special type.
A rotary dryer is said to be of the direct type if by virtue of its design, heat is added to or removed from the solids by direct exchange between the gas and solids. The direct heat dryer are the simplest and the most economical class. They are used when a direct contact with the hot gas or air is not detrimental to the fed. When high temperature is required for drying process in a direct-heated rotary dryer, a combustion chamber is used and when low temperature is required on the other hand, for thermolabile materials, steam coil is used.
Rotary dryer can also be said to be indirect when the heating medium is separated from contact with the solid by a metal wall or tube. Although there is an infinite variation of rotary dryers, which present characteristics suitable for drying, chemical reactions, mixing, solvent recovery, thermal decompositions, sintering and agglomeration of solids, the main types or rotary dryers include;

Direct rotary dryer
Direct rotary kiln
Indirect steam-tube dryer
Indirect rotary calciner
Direct Roto-Louvre dryer