Two-Fluid and Discrete Population Balance Model for Simulation of Batch Sedimentation Relevant to Plutonium Reconversion

There are widespread occurrence and application of solid-liquid sedimentation processes among different industries. Therefore, it becomes important to understand the hydrodynamic inside the process equipment and particle agglomeration characteristics. In the present work, solid-liquid sedimentation is analyzed, which will be helpful for the design of continuous process equipment in plutonium (Pu) reconversion. Experiments were carried out in a batch settler to understand solid sedimentation in suspension in terms of varying the overall solid fractions. Euler-Euler two-fluid simulations were performed to investigate the local and overall solid phase volume fraction distributions, position of the active interface (AI) (settling curve), axial solid phase velocity, and pressure distributions during settling, and selected data were compared with the measured data. Further, the discrete population balance model (PBM) with different agglomeration kernels was used with the two-fluid computational fluid dynamics (CFD) model to understand and further improve predictions in terms of the AI position. The variation in number density of the different particles in the settler with time was investigated. The predicted results show that agglomeration is dominant during the sedimentation process and application of the discrete PBM with the CFD model enhances the predictive capability in comparison with the predictions obtained from only the two-fluid model. The results reported using CFD+PBM will aid in the design of continuous process equipment (thickener/precipitator) for Pu reconversion.