The heated screw dryers exploit the transmission of heat by contact, where the coil and the jacket of the screw are heated by a fluid – usually diathermic oil or steam is preferred – and in counter current a light gaseous flow is made to flow (air or inert gas) which helps the stripping of the steam released during drying.
The heated coil, in addition to releasing energy to the material, makes it move forward and turn inside the casing so as to facilitate the mixing and advancement of the material. This type of dryer can also be internally polished. It can be washed and is suitable for the treatment of food products.
This technology allows you to dry up powdery or oxidation-sensitive products even at high temperatures.