Exploring the effects of screw geometry and particle size distribution in a twin-screw conveying system

Screw conveying has a wide range of applications, including mining, agriculture, pharmaceuticals and food. However, there is still a limited understanding of the dynamics inside these systems. In this paper, the effects of altering the geometry of a horizontal twin-screw conveyor are explored using the Discrete Element Method (DEM). The screw pitch, screw spacing, screw speed and particle size distribution were investigated. Clear optima exist within most parameters, but particularly for the screw pitch. A 18 mm pitch (the length of the barrel diameter) showed greater efficiency in material transport because of the helix angle. An interaction was also observed between the geometric parameters. High pitches demonstrated better conveying at low spacing, and lower pitches were better at higher spacing. The effect of the particle size distribution was smaller, and the bulk behaviour was almost identical for all size distributions. However, there appeared to be some segregation as the difference between sizes in a binary distribution widened.