Horizontal Beet Pulp Rotary Drying Machine 600mm Diameter

Customized Rotary Drying Plant

The Rotary Dryer

Despite the introduction of new technology, the long established Rotary Rotary Dryer is still widely regarded as the workhorse of many process industries. The robust yet simple construction combines flexibility with reliability, enabling this type of dryer to handle a vast range of materials and to operate continuously under the most arduous conditions. The design also permits the use of the highest possible drying temperatures and in contrast to other dryers is not sensitive to wide variations in material size, moisture content or throughput.

Principles of Operation

In its simplest form, the Rotary Dryer consists of a slightly inclined rotating cylinder, fitted with a series of peripheral flights arranged to lift, distribute and transport the material. The flights are designed to suit the particular handling characteristics of the material, which may vary with increasing dryness. The principle of operation is based on showering, or cascading the wet material through a hot gas stream, flowing either co-current or counter-current to the solids. The hot gas induces the evaporation of the moisture. The heat lost to the material and evaporation of water vapor reduces the gas temperature rapidly, such that it leaves the dryer at a comparatively low temperature. The efficiency of the dryer is largely dependent on the differential between the inlet and exhaust gas temperatures, although the heat transfer rate is also influenced by the relationship between the design of flights and the speed of rotation. However, irrespective of the gas and material temperatures the drying (or residence) time may be critical, as this is governed by the rate of diffusion of water from the core to the surface of the material. For special applications, the rotary cascade design is adapted to provide a shortfall, or ‘Cruciform’, lifter configuration.