Rotary Dryer

Darmawan produces, among others, several types of dryers. Rotary dryer is a type of industrial dryer that is used to reduce or minimize the moisture content of the material to be dried with heated air. The dryer consists of a rotating cylindrical drum, a drive mechanism, and a support structure (concrete posts or steel frame). The material to be dried enters the dryer and, as the dryer rotates, the material is lifted by a series of fins on the wall on the inside of the cylindrical drum. When the material is lifted to the top, it will fall back to the bottom of the cylindrical drum, passing through the hot gas stream as it falls.


Rotary dryers have many applications but are most commonly used in the minerals industry to dry sand, rock, soil and ore. They are also used in the food industry for granular materials such as grains, cereals, coffee beans and waste water sludge.


A wide variety of rotary dryer designs are available for different applications. Gas flow, heat source and drum design all affect drying efficiency and suitability for different materials.

Gas Flow

The hot gas flow can move towards the outlet from the inlet (known as co-current flow), or towards the inlet from the outlet (known as counter-current flow).

Heat Source

The gas stream is most often heated by a burner using gas, coal or oil.

  • Direct heating system

The hot gas stream consists of a mixture of air and combustion gases from the burner or furnace

  • Indirectly heated system

Where the combustion gases of the burner or furnace do not enter the dryer. The hot gas stream consists of circulating clean air. Indirectly heated dryers are used when product contamination is a concern.

Drum Design

Rotary dryers can consist of single drum (single phase) or double drum (two phase). Multiple drums can reduce the amount of space required for equipment to achieve the same output with smaller dimensions.

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