The particle size distribution of the resulting pellets is within a wide range of sizes. Pelletizing by rolling is the process of giving a spherical shape to extrudate after the extrusion process or to wet pellets after the wet granulation process. The spherical shaped pellets provide good stable friability and pellets with minimal mass variation are obtained. For example, in the study of granulates of calcium biphosphate, magnesium hydroxide and sulfadimezine prepared by wet granulation followed by rolling, it was found that their bulkiness increased by 40-100%. Rolling of wet pellets or extrudate is carried out on equipment called spheronizer. The principle of operation of a spheronizer is as follows: in the first stage, the material is compacted. With the help of a rotor-transfer granulator pellets are formed, which in the second stage are rolled in the spheronizer to a spherical shape and removed from the apparatus. In the presented GEA spheronizer, the plate is covered with smooth recesses. The plate is rotating and is tightly adhered to the walls of the apparatus. In this way, pellets with a good spherical shape are formed and a good particle size distribution is achieved.

The granulate or extrudate is rolled to a spherical shape under the action of centrifugal and frictional forces. This design of the spheronizer solves the problem of material edge breakage and the appearance of unwanted small particles. Optimization of the process is achieved by selecting the rotation cycle time, plate speed, product loading and controlling the air flow around the periphery of the rotating plate. In the Glatt spheronizer, wet pelletized products or pre-formed extrudates are fed onto a rotating disk for pelletizing. The rotation of the disk, the flow of incoming product and a jet of air supplied through a slit in the side wall create an orderly product movement in a spiral path at the vessel wall. Due to intensive rolling, the surface of the particles is smoothed to form pellets. The dust particles generated in this process are captured again by the resulting pellets directly in the process. To increase the throughput capacity of the equipment in batch operation, several spheronizers are combined in a cascade. The cascade principle is also used to produce pellets with a laminated structure. The structure of the pellets is determined by the granulation process that takes place earlier in the process chain.