Engineering Aspects of Single- and Twin-screw Extrusion-cooking of Biopolymers

A survey is given of the properties of single- and twin-screw extruders. The influence on the design of the different leakage gaps existing in co-rotating, counter-rotating, self-wiping, twin-screw extruders and single-screw equipment is discussed. The mixing effects in single- and twin-screw equipment and the shear distribution and shear levels that can be generated in the equipment are discussed. The overheating effect possible in single-screw extruders is related to the type of flow in the extruder channel. Finally, the properties and power consumption of Cincinnati conical, twin-screw extruders are discussed.