Indirectly acting drying drums are predominantly used for calcination of finely-grained solids at high temperatures. They are also suitable for heating finely-grained materials to high temperatures.
The indirect supply of heat for drying means that it is possible to work with a reduced oxygen atmosphere (to avoid product oxidisation or to avoid or reduce harmful exhaust gases).
Example of application
The exemplary plant is used for heat treatment of very fine minerals. The solid is heated indirectly through the wall of the rotating drum to a few hundred degree Celsius. Thus the powder gets the by the client required characteristics. Heating is realized by a number of in-line gas burners inside a static insulation jacket. The exhaust gases are partially recirculated for best heat recovery.