DEM study of mixing behaviours of cohesive particles in a U-shaped ribbon mixer

Abstract

Cohesive particles handling is frequently encountered in particle-mixing processes, especially in food industries, but the mixing mechanism of cohesive particles in large-scale mixers is not well understood. In this work, the influence of different liquid properties (i.e., water and honey) on the mixing performance of cohesive particles in an industrial-scale U-shaped ribbon mixer is explored using discrete element simulation (DEM). The results show that the cohesive force performs a significant influence on the particle behaviours during the mixing process. The wet mixture presents a faster mixing rate and higher final mixing degree than the dry mixture at low impeller speeds. With the increase of impeller speeds, the mixing rates for both wet and dry mixtures increase but the overall final mixing degrees decrease. Meanwhile, the influence of cohesive force becomes more insignificant at higher impeller speeds. For industrial mixing processes, the addition of a certain liquid helps improve the final mixing quality. For both dry and wet mixtures, a low impeller speed (50– 100 rpm) is recommended to realise a high final mixing quality, but a high impeller speed can increase the processing capacity per unit time. A suitable impeller speed should be selected in practical industrial mixing processes with a promise between the product quality and handling capacity. This study sheds light on the detailed mixing behaviour of the U-shaped ribbon mixer for cohesive particle mixing and provides an operation guide for the practical food mixing process.