The influence of tank size and impeller geometry on turbulent flocculation: II. Model

A population balance model has been developed to simulate the dynamics of particle agglomeration and breakup during flocculation in turbulent flow. The model was used to simulate flocculation in three square tanks of 5-, 28- , and 560-L volume with Rushton turbines and A310 fluid foil impellers. The average power per unit volume, G(m), was set at 40 s^-1 for all tank/impeller configurations. The numerical results show that the model predicts the shift in the cumulative particle-size distribution to a smaller particle-size range with increasing tank size, regardless of impeller type. The model also predicts the shift in the cumulative particle size distribution to a smaller particle-size range moving from the A310 fluid foil impeller to the Rushton turbine. Model sensitivity to tank size and impeller geometry was accomplished by incorporating the turbulence intensity in the impeller discharge zone in the breakup part of the population balance model.