Analysis of cohesive particle percolation in a packed bed using discrete element method

Abstract

Many granular materials are in cohesive or wet state in pyrometallurgy processes. The present work systematically studies the cohesive particle percolation behaviour in a packed bed by discrete element method (DEM). The results indicate that the vertical velocity of percolating particles increases with increasing the cohesive force from 0 to 2 mg (the gravity force of percolating particle, given by gd3/6). While for a higher cohesive force, e.g. fe=8 mg, insufficient percolation occurs and percolating particles stick in the packed bed. Percolating particles in the packed bed shows a diffusivity for the cases of smaller cohesive force. The transverse dispersion of fe=2 mg is smaller than that of fe=0, while the longitudinal dispersion becomes larger when the cohesive force changes from 0 to 2 mg. In addition, the influence of other key variables, such as diameter ratio, damping coefficient and rolling friction coefficient on percolation behaviour is also discussed. The transverse dispersion coefficient increases with the diameter ratio, while the longitudinal dispersion coefficient decreases with the diameter ratio. With the increase of damping coefficient or rolling friction coefficient, the transverse dispersion coefficient decreases but the longitudinal dispersion increases. The study provides a fundamental understanding on percolation behaviour of cohesive particles in a packed bed, and is useful for processes understanding and optimization in cohesive particles handling and mixing.