Application of Population Balance Equations and Interaction Models in Cfd Simulation of The Bubble Distribution in Dissolved Air Flotation

Abstract This study concerns the application of computational fluid dynamics (CFD) and population balance equations (PBEs) in biphasic (water-air) simulations of the dissolved air flotation (DAF) process. The incorporation of population balance equations for simulation of the microbubble diameter distribution was based on the literature. The gas phase was simulated as being composed of two different phases: air 1 ( d 2 ( d ≥50 μm). A non-homogeneous discrete model was applied and specific models enabled the prediction of phase change by breakage or coalescence. The models Turbulent and Luo were used to represent coalescence. The grid convergence index (GCI) method was applied for quantification of the discretization error of the tested computational grids. The grid selected for the simulations showed a discretization error of 5.17%. The results indicated that the velocity vectors of the aqueous phase presented stratified horizontal flow characteristics close to the surface and vertical plug flow inside the tank. The PBE results for the air volumetric fraction demonstrated that the coalescence model had a major impact in terms of the behavior of the gas phase in the white zone. Simulations indicated that the Luo model reduced in about 60% the air 1 concentration in the positions evaluated when compared with Turbulent model.