The rheology of dense granular flows in a disc impeller high shear granulator
Artikel i vetenskaplig tidskrift, 2013
The aim of the present study is to evaluate the new approach to dense particulate systems proposed by Jop et al. [1],
in the dense regions of a High Shear Granulator (HSG). Wet granulation in high shear mixers is a common process
in pharmaceutical technologies and a good understanding of the local mixing and flow patterns is a pre-requisite
for this step. In the aforementioned model a dense granularflow is characterized as a visco-plasticfluid. Therefore
the local rheology of the system can be predicted assuming averaged and virtual properties and a constant solid
volume fraction.
A simple disc impeller granulator with glass spheres was chosen for this study. The dynamics of the system have
been studied using several techniques including PIV analyses, CFD simulation and image processing. The flow
behaviour has been characterized for various impeller speeds and particle loads. Several cases have been analyzed
from different aspects both in experiments and through equivalent simulations to evaluate the validity of the
model in these particular applications.
Results look promising in spite of the simplicity of the model. The model was found to give a good general
description of the flow field and bed shape. On the other hand the model is insufficient in some aspects; mostly
related to the regions with low volume fraction. The next step would be to combine the model with conventional
models on rapid granular flow such as Kinetic Theory of Granular Flows (KTGF).
Rheology
High shear granulation
Dense granular flows
Disc impeller