Three-dimensional simulation of the influence of different flotation media in the dissolved air flotation tank through the population balance model

Abstract

Gas–liquid flow in the dissolved air flotation (DAF) tank was studied through computational fluid dynamics through the realizable k-ε model and the population balance model (PBM) to predict the gas content of different flotation mediums (air, carbon dioxide, and chlorine) at different heights of the separation zone in the DAF tank. Simultaneously, a particular focus was placed on studying the effects of bubble aggregation and breakage on gas content. The results indicated that there were virtually no bubbles present in the region below 0.1 m of the separation zone. The gas content in the separation zone could meet the needs for gas content in the DAF tank when all these three gases were adopted as flotation medium. The introduction of models for bubble aggregation and breakage resulted in lower gas content at the bottom of the separation zone and higher gas content at the top, aligning more closely with experimental data. Due to the structural similarity and similar physicochemical characteristics of carbon dioxide and water molecules, the impact of bubble aggregation and breakage on the gas content is minimal. HIGHLIGHTS Considering the aggregation and breakage of bubbles during simulation.; Introducing the population balance model to consider non-uniform-sized bubbles.; Study the hydraulic characteristics of the separation zone when adopting air, carbon dioxide, and chlorine gas as flotation medium.;

Keywords

• bubble
• cfd
• dissolved air flotation
• flotation medium
• population balance model
• separation zone