Parameter Optimization Of Dyeing Wastewater Treatment And Characterization Of Hydrodynamics In A Spiral Flow Tubular Electrochemical Reactor

Recently electrochemical oxidation treatment has been a heat topic for removing pollutants from orgainc wastewater,and the tubular electrochemical reactor is one kind of the most frequently used electrochemical reactor.However,the flow field on the electrode surface in a traditional concentric tubular reactor is not homogeneous and the tubulence intensity is weak,which leading to low treatment efficiency of the reactors.Therefore,a new tubular electrochemical reactor based on spiral flow caused by a turbulence promoter is presented.In this work,we studied fluid dynamics and electro-oxidation of methylene blue wastewater of the new reactor by comparing them to the traditional one.Firstly we investigated the individual effects of operating parameters on treatment performance,and then optimized these parameters through using response surface methodology(RSM).The flow field of two reactors were also simulated by Computational Fluid Dynamics(CFD).Finally,we compared the performance of electro-oxidation of methylene blue wastewater between the spiral flow tubular electrochemical reactor and the traditional one.A spiral flow tubular electrochemical reactor with the turbulence promoter was used to analyze the influence of current dens ity and hydraulic retention time(HRT)on the performance of electro-oxidation process.The results showed that the increase in current density and HRT led to greater removal of methylene blue and TOC,nearly approaching to 99% and 55%,respectively.Through the kinetics analysis,we found that the electrochemical degradation of methylene blue and TOC were agreed with pseudo first-order kinetics,and kinetically limited by reaction controlled.We also optimized these two operating parameters by response sur face methodology.The quadratic model for MB degradation was abtained and there was a significant interaction between current density and hydraulic retention time in the RSM model.The optimal conditions for MB removal was i=8.5 m A/cm2,HRT=90 min.Similarly,the primary model for TOC degradation was also obtained,wheras the interaction between current density and HRT was really weak.Fluid flow and hydrodynamics of the spiral flow tubular electrochemical reactor using computational fluid dynamics(CFD)method,were also studied by comparing them to the traditional one.In the spiral flow tubular electrochemical reactor,due to the presence of spiral turbulence promoter,the velocit y distribution trended to be more homogeneous,and the mean flow rate clearly increased by 500-700% compared to that of the traditional one.Besides,the mean turbulence intensity and wall shear stress were 1.6 and above 4 times those of the traditional tubular electrochemical reactor,respectively.The temperature field seemed to be more chaos in the spiral flow reactor and the mean temperature of anode surface was cooler than that in the traditional one,which was beneficial for the stable operation of reactors.The electro-oxidation of methylene blue simulation wastewater treatment was developed to analyze the processing efficiency of the two types of electrochemical reactors.Due to the turbulence promotor,the spiral flow reactor performed better than the traditional reactor,improving the removal rate of MB and TOC by 17% and 71%,respectively.The results affirmed that the spiral flow tubular electrochemical reactor could greatly improve the removal efficiency of dyeing wastewater.