What is the working principle of a rotary drum granulator?

As a key piece of equipment for producing granular materials, the rotary drum granulator is widely used in industries such as fertilizers, building materials, and chemicals. Its working principle revolves around the core logic of "material agglomeration - rolling molding - stabilization and solidification," achieving the transformation of powdered raw materials into uniform particles through the synergy of mechanical motion and physicochemical processes.

The core structure of the equipment is an inclined cylindrical drum, typically at an angle of 3°-6° to the horizontal plane. This design provides the power basis for the axial movement of the material. During operation, the drum is driven by a motor to rotate at a uniform speed. Powdered raw materials enter the drum through the feed inlet, while a suitable amount of binder (such as water, slurry, or a special binder) is sprayed onto the material through a spraying device. The raw material and binder are fully mixed under the rotation of the drum, forming a sticky film on the surface of the moistened powder particles, creating conditions for agglomeration.
As the drum continues to rotate, the material continuously tumbles and collides under the combined action of centrifugal force, friction, and gravity. Tiny, moist particles attract each other, gradually forming tiny "master granules." These master granules continuously attract surrounding powder materials during subsequent rolling, growing larger like a snowball. The inner wall of the drum is typically equipped with lifting plates and other devices, which improve the mixing uniformity of the material, prevent material from sticking to the wall, and lift the material to a certain height before scattering it, enhancing the impact and compaction effect of the particles, resulting in a denser particle structure.
The quality of the formed particles is closely related to the drum speed, tilt angle, and material moisture content: too high a speed can cause particles to be thrown out by centrifugal force, while too low a speed will not form sufficient agglomeration force; too large a tilt angle results in too short a material residence time, making it difficult for particles to grow, while too small a tilt angle reduces production efficiency; the amount of binder needs to be precisely controlled, as too much can cause particles to stick and clump together, while too little will not form stable particles. Once the particles reach the preset particle size, they will be discharged from the outlet as the drum tilts, entering the subsequent drying and screening stages. Unqualified fine powder is returned to the rotary drum granulator for re-granulation, forming a closed-loop production process.
The rotary drum granulator does not require high temperature and high pressure throughout the entire process. It achieves molding by relying on physical agglomeration and mechanical compaction. It not only maintains the original properties of the raw materials, but also allows for precise control of particle size, strength and other indicators through parameter adjustment, making it an ideal equipment for granulation processing in industrial production.