258006 A Simplified and Optimized Novel Design of RDC-Columns
The applicability of Computational Fluid Dynamics (CFD) to extraction column research is constantly growing due to the incessant increase of calculation power. So far, the interfering phenomena are still far too complex to be predicted without using a bunch of models and assumptions. At present, CFD-simulations can provide hydrodynamic parameters (axial dispersion coefficients, bubble hold-up, droplet size distributions etc.) which are crucial for apparatus design.
In the present work, the continuous phase flow fields of two configurations of the Rotating Disc Contactor (RDC150 & RDC100) were recorded with Particle Image Velocimetry (PIV). The mean velocity vector fields obtained from PIV were subsequently used to evaluate the simulation setup in Ansys Fluent 14.
The residence time distribution of the continuous phase was obtained by injecting saturated salt solution and by monitoring the electric conductivity at four different axial positions. The obtained values for the axial dispersion coefficient were compared with Euler-Langrange Simulations (stochastic tracking method) and showed excellent agreement.
Based on the validated simulation settings (models and parameters) continuous phase simulations combined with the Euler-Langrange framework were used to optimize the ratio of the column internals. The shaft diameter, the compartment height, the rotor diameter and the stator diameter were systematically altered in order to find the optimum compartment geometry that leads to lowest axial dispersion. In a next step the same tracking method was applied to quantify and optimize radial mixing within one compartment. With the target of minimal axial dispersion and maximal radial mixing an optimized RDC geometry was proposed.
Subsequent dual phase simulations (Euler-Euler model combined with population balances) were performed to evaluate an optimized and stabilized flow pattern in dual phase operation. Smaller droplets and narrow drop size distributions were observed for the optimized internals geometry, confirming optimization in terms of overall column performance.