The rotary-cylinder extruder consists of two cylinders: the first is a rotating cylinder with holes – the pelletizing cylinder, the second is a solid empty cylinder rotating towards the first. During the extrusion process, high pressure is created by the rotation of the two cylinders, resulting in a product of high density and a certain length. The advantages of the rotary-cylinder extruder are the high pressure created during the extrusion process, high density, a defined product length, and no stagnant zones. The disadvantage is the difficulty encountered in cleaning the equipment. The extruder is used for small outputs. Its design resembles that of a tablet machine. The Niro extruder is based on a unique technology of pushing and shearing the extrudate at low speed. This extruder is ideal for sensitive products that can be damaged in other, more intensive systems.

The extruder has a wide range of screens of different sizes through which the product passes to optimize pellet diameter, surface characteristics and size distribution. This extruder can be operated in continuous and batch mode, with no stagnant zones or significant product delays. The extruder has a small footprint and is easy to clean, which is an important advantage. The choice of extruder can be made taking into account the following parameters: Principle requirements for the extruder: output; footprint; energy consumption. Methods of further processing or recycling. As recommendations, the following can be highlighted: if it is necessary to obtain homogeneous pellets dried in a fluidized bed, it is better to use a radial-press extruder; if it is necessary to obtain high-density extrudate with further sphericalization, it is more appropriate to use a rotary-cylindrical and press extruder. Scalability.