DEM Simulations of the Effects of Lifters on Solid Mixing in a Rotary Drum
Rotary drums play an important role in the processing of granular materials in chemical, metallurgical, pharmaceutical, food as well as waste processing industries. Rotary drums are widely used in operations such as mixing, heating, drying and reacting of solid material or combination of these operations, due to its flexibility in handling feed materials of various properties and in adjustment of residence time. In this paper, a preliminary DEM modelling has also been carried out to simulate the solid motions and mixing in rotary drums under rolling mode, considering the influences of rotational speed and lifters. The DEM model seems to reasonably predict the active layer depth, in broad agreement with experimental results published in the literature. The dilated granular flow of particles within this layer is characterised by high shear and particle mixing rates normal to the surface. The simulations show that increasing rotating speed generally increases the active layer depth therefore solid mixing. Installation of the lifters significantly increases the active layer depth. The particles positioned on the top of the active layer produce larger shear stresses on the particles around the top area of the active layer, increasing the velocities and solid mixing. The results indicate that the understanding of the active layer depth is essential to the optimisation of the lifters.