Modelling of gas-solid-liquid flow and particle mixing in a rotary drum

Solid-liquid rotary drums have been widely practised in various industries, while the complex multiphase hydrodynamics hinders the understanding and optimisation of these apparatuses. In this work, the computational fluid dynamics-discrete element methoddata (CFD-DEM) coupled with volume of fluid (VOF) is developed to describe the gas-solid-liquid flow and mixing behaviours in a rotary drum considering inter-particle collisions, inter-phase interactions, and interface morphology. A smoothing method is used to link the quantities between the particle and computational grids, allowing the fine grids to resolve flow details such as the gas-liquid interface position and curvature. After model validations, the typical mixing behaviours of gas-solid-liquid flow in a rotary drum are studied. The effects of liquid presence and rotating speed on particle-scale behaviours (e.g., repose angle, active-passive zone depth, solid residence time and contact force chain) and the time evolved mixing performance (e.g., mixing index and dispersion) are studied. The results show a positive correlation of the active depth, mixing degree, and particle dispersion with the rotating speed. The liquid presence leads to a deeper active depth, prolonged solid residence time in the active zone, and lower contact force. The work sheds light on the design and process optimization of rotary drums.

Automated summary

In this work, a computational fluid dynamics-discrete element method-data coupled with volume of fluid is developed to describe the gas-solid-liquid flow and mixing behaviors in a rotary drum. The effects of liquid presence and rotating speed on the mixing performance are studied.