Principles of Rotary Drying
The directly heated rotary dryer operates on the principle of
lifting and showering the product through a hot gas stream moving.
The efficiency of the dryer is largely dependant 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 greater thermal efficiency and where inertization is required,
recycling of exhaust gases can be used. This can be implemented on
all our airstream drying systems and retrofitted on customer's
existing drying operations.
For special applications, the rotary cascade design is adapted to
provide a shortfall, or 'Cruciform', lifter configuration.
Co-Current Rotary Dryers are the most widely used and are particularly suitable for drying
materials containing a high moisture content, which are heat
sensitive or have a tendency to stick or cake.
The wet material is in contact with the gas at its highest
temperature, which rapidly evaporates surface moisture. The initial
heat transfer rate is high, causing an immediate and considerable
drop in gas temperature, which prevents overheating of the material
and the dryer shell. The final product is in contact with the gas
at its lowest temperature, enabling the moisture content to be
readily controlled, usually by maintaining the dryer exhaust gas
temperature at a pre-set value.
Co-Current Rotary Dryers Features
Wet material is in contact with the gas at its highest temperature,
which rapidly evaporates surface moisture
The final product is in contact with the gas at its lowest
temperature
Co-Current Rotary Dryers Benefits
Initial heat transfer rate is high, causing an immediate and
considerable drop in gas temperature, which prevents overheating of
the material and the dryer shell; co-current dryers are
particularly suitable for drying materials containing a high
moisture content
Enables the moisture content to be readily controlled
Co-Current Rotary Dryers Process Flow Diagram
Co-Current Rotary Dryers Technical Details
Diameter: 600mm to 3500mm
Length: 8000mm to 65 000mm
Methods of heating: Direct or indirect
Capacity: 500kg/h to 175t/h
Fuel: coal, natural gas, heavy oil, etc
Temp range: 200-700°C
Material: Carbon steel, Stainless steel, etc
Thickness: 8mm to 70mm
