4. Rotary drum

Rotary drum granulation [38] is a widely used technique in the fertilizer and iron ore industries. The device, also known as a drum granulator, consists of a cylindrical shell rotating on supports and inclined at a few degrees to the horizontal. The length of the drum varies from four to more than ten times its diameter, which can reach 3 or even 4 m. The product to be pelletized is introduced at the highest end and progresses through the drum under the combined effect of rotation and inclination, to be discharged at the opposite end (figure 18 ). The residence time, generally of the order of a few minutes, is a function of drum length, slope and rotation speed. Binder can be added to the product to be pelletized either before it is introduced...