Wet granular flows in a bladed mixer: Experiments and simulations of monodisperse spheres

Abstract

The flow and agglomeration of wet particles in a bladed mixer was studied experimentally using particle image velocimetry and computationally using the discrete element method. The experimental and computational work showed that particle beds at low moisture contents are characterized by enhanced convective and diffusive particle motion as well as enhanced mixing kinetics when compared to dry particle beds. This behavior is attributed to the development of small particle agglomerates which behave like rough, nonspherical particles and enable the transfer of energy from the blades to the particle bed. At higher moisture contents, a different behavior was observed. Particle convective and diffusive motion was hindered by the presence of moisture at higher levels leading to a decrease in mixing performance. This occurs as large agglomerates are formed and are not broken apart by shear leading to poor mixing. Pressure and shear stress profiles were shown to be affected by the amount of moisture in the system. The extent of agglomeration at different moisture contents was quantified via the discrete element simulations. Agglomerate size distributions and morphology were shown to be strong functions of moisture content. © 2012 American Institute of Chemical Engineers AIChE J, 2012

Numerical simulation of granular mixing in a rotary drum using a generalized interpolation material point method

“…This is due to the formation of plug flow in the active region, resulting in a slow mixing process under high cohesion cases. Similar results have been presented in DEM simulation of the rotary drum and a bladed mixer …”

DEM simulations: mixing of dry and wet granular material with different contact angles

“…Their model has been used successfully to perform a DEM simulation of a fluidized bed. Remy et al [12] transferred this model to cohesive batch mixing processes and validated their numerical findings experimentally using particle image velocimetry. This work provided interesting insights into mixing kinetics and local agglomeration in a bladed mixer at different moisture contents.…”

Forces and flow induced by a moving intruder in a granular packing: coarse-graining and DEM simulations versus experiments

“…Mixing powders using intruders, such as blades, paddles, agitators… is widely used in chemical engineering [1,2], civil engineering [3], pharmaceutical [4,5], food science [6,7] or agronomy [8,9]. Common concerns regarding interactions between an intruder and a granular bed are shared by many unit operations like blending, kneading [10], wet agglomeration [11,12] or milling [13,14].…”