Kinetic Modeling and Experimental Verification of a Swirl Flocculation-Enhanced Reactor: A Case Study of Coal Chemical Wastewater Pretreatment

Abstract

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 best flocculation effect was achieved at the 8:5 of aspect ratio of SFR and the mixing blade length was at 3/10 of the reactor as well as 180 r/min of agitating rate, where 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 single 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.

Keywords: Swirl flocculation-enhanced reactor, Computational Fluid Dynamics, Coal chemical wastewater, Flocculation efficiency