The low separation efficiency of alkali/surfactant/polymer (ASP)-flooding-produced water, attributed to its high emulsification, high viscosity, and surfactant enrichment, presents a significant treatment challenge. To evaluate the effects of flotation unit structure on internal flow field characteristics and the separation performance of oil and suspended solids in a dissolved air flotation–sedimentation tank, this study conducted CFD numerical simulations. The results demonstrate that with 40 gas injection ports, the flow field achieves optimal uniformity and stability: the oil removal rate reaches 68.1%, and the suspended solids removal rate reaches 56.6%. Compared to the single-ring and triple-ring configurations, the double-ring gas injection form exhibits better flow continuity, resulting in increased removal rates of 67.6% for oil and 56.7% for suspended solids. At a gas injection ring height of 10,500 mm, the oil layer in the flotation zone remains continuous and stable, while suspended solids settle into a distinct sediment layer at the bottom, enhancing both oil and suspended solids removal efficiencies. On this basis, the optimized structure of the flotation unit was determined. The removal rates of oil and suspended solids were enhanced by approximately 1.8% to 4.8% and 3.5% to 7.0%, respectively, compared to the existing conditions.
Wang et al. (Sat,) studied this question.