Kinetic modeling and experimental verification of a swirl flocculation-enhanced reactor: A case study of coal chemical wastewater pretreatment

In this study, a swirl flocculation-enhanced reactor (SFR) was designed to address the problems of high dosage and poor pollutant removal in the pretreatment process of coal chemical wastewater (CCW). The effects of different height-to-diameter (H/D) ratios, stirring speed, and impeller length on SFR flow field were analyzed by computational fluid dynamics (CFD) simulation. The optimal H/D and operating condition of SFR were determined by comparing and analyzing fluid velocity, eddy viscosity, and turbulent kinetic energy. Then the lab-scale SFR was manufactured to conduct agglomeration tests. The results showed that the flocculation effect was the best when the H/D ratio of SFR is 8:5 and the mixing blade length was at 3/10 of the reactor as well as 180 r/min of agitating rate. The removal rates of oil, suspended solids (SS), chemical oxygen demand (COD) and phenol in CCW could reach 73.43%, 87.88%, 78.63% and 65.20%, respectively. In addition, the plausibility of SFR design was further validated by the fact that the reagent dose was reduced by 50–60% and the removal rate was increased by 20–30% in comparison with the beaker flocculation experiment. The SFR flow field flocculation enhancement mechanism was analyzed. It is expected that the reactor designed in this work, has a wide range of industrial applications in the CCW treatment.