Simulating Solid Suspension in Stirred Vessels with a Fully Coupled CFD-DEM Algorithm

Solid – Liquid mixing in high viscosity liquid and/or high solids concentration is a challenging problem due to the solid-solid and solid-liquid phase interactions. Just suspended speed (N_js), suspension height (H_s) and the power consumption can vary not only with the material properties but also with the design of tank and impellers.

At the AIChE annual meeting 2016 we presented a new method for simulating solid suspension based on a fully coupled CFD-DEM algorithm [1]. Validation was done against experimental data for a broad variety for impeller speed.

In this contribution we are evaluating the effect of material properties and different bottom clearance on the fraction of suspended particles and the occurrence of dead zones below the impeller. Additionally we are comparing the achieved results with results based on an Eulerian Multiphase – Granular Flow (EMP-GF) approach with respect to accuracy and runtime. The differences and limitations of both approaches are discusses.

[1] Baran, O. et al.: A Fully Coupled CFD-DEM Algorithm for S-L Mixing in Stirred Vessels, AIChE Annual Meeting 2016, San Francisco, Ca

[2] Bertrand, F. et al.: Experimental investigation of the mixing of viscous liquids and non-dilute concentrations of particles in a stirred tank, Chem. Eng. Res. Des. (108), 2016, 55–68