A hybrid compartmental-CFD model to investigate forced circulation crystallizer performance

Abstract

Forced Circulation (FC) crystallizer plays a key role in a Zero Liquid Discharge desalination process. The hydrodynamics of an FC crystallizer involves a complex turbulent flow field. Computational Fluid Dynamics as a powerful method for simulating flow hydrodynamics suffers from high computational cost. In contrast, the compartmental method has widely been used in practical applications. This method does not have the challenge of high computational cost, but it may give unrealistic results since the hydrodynamics of the flow is not taken into account. In the present work, a hybrid compartmental-CFD model, as a powerful method, is utilized. In this model, a simple CFD simulation is made at a relatively low cost. The CFD results are then translated into several proper parameters to modify the compartmental model. Results show that taking 3D hydrodynamic effects into account in the compartmental model, after 15E4 seconds confrontation between growth and attrition mechanisms, finally narrower distribution with a 37% decrease in Sauter diameter is obtained. Furthermore, boiling zone is intensely susceptible to particle segregation, preventing the presence of particles above 583 μm. In addition, mixing zone with moderate volume fraction and supersaturation plays a significant role in crystallization, contributing 54% of the total mass transfer.