Structure Optimization And Simulation Of Ozonation Process Of Ozone Contactor Based On CFD

With the continuous improvement of water supply technology and the complex and pluralistic situation faced by water environment,the regulations of water quality standards are becoming more and more strict,and the diversity of the distribution of water resources in China has resulted in different water supply processes in different places.At present,the conventional basic water treatment process has been difficult to meet the more stringent effluent quality standards.It is difficult to remove trace organic pollutants and two insects(Cryptosporidium and Giardia)in the water body.Therefore,it is urgent to treat the water source water in depth.Ozone technology has been widely used in water treatment plants at home and abroad for its efficient removal of organic matter and two insects and good odor control.However,due to the strong oxidization of ozone and the closure of contactor,it is difficult to have a detailed understanding and evaluation of its internal flow,the distribution of ozone concentration and the related chemical reactions.The baffle contactor is widely applied and it has a large area of reflux and dead water during its operation,which has a serious impact on its operational efficiency.Therefore,it is increasingly urgent to study the flow pattern in the contactor,the ozone distribution in the liquid phase and the design of the hydraulic optimization structure.Computational fluid dynamics(CFD)has become an effective tool for studying reactor operation and optimizing its hydraulic structure with the development of computer technology.Since the ozone contactor is difficult to be studied in large scale experiments,the CFD technology was used in this study to simulate the flow patterns in the ozone contactor,design a suitable hydraulic optimization structure and complete the modeling and numerical simulation of the ozone mass transfer between gas and liquid phase and the concentration distribution of liquid ozone in the contactor.This study aims to provide some guidance and reference for the actual operation and reconstruction.Firstly,the contactor was modeled and calculated to characterize the flow pattern in it.In view of the problem of reflux and dead water in the reaction chamber,the corresponding structural optimization scheme was proposed to improve the hydraulic efficiency.The main scheme has two methods of setting double baffles(double baffle type 1 and 2)and four grid setting methods(grid type 1-4)and the method of setting grille.Then the distribution function curve of the liquid age of each pool was drawn out,and the t10/HRT value was set as a hydraulic efficiency index.It was found that all the optimized schemes had improved the hydraulic efficiency of the original contactor,in which the optimization effect of grid 1 and grid 3 achieved the best.Then the self-made hydraulic experiment model was made and the curve of the liquid age distribution function of the original contactor and the grid type model were drawn by the tracer test.Compared with the curve simulated by CFD,it was found that two curves had high fitting degree,thus the reliability of flow simulation using CFD technology could be proved.Secondly,the model of gas-liquid two phase flow in the ozone contactor was established by Euler-Euler method,and the mass transfer and attenuation reaction of ozone were loaded in the form of user-defined function(UDF)to obtain the distribution of the liquid ozone concentration in various contactors.On this basis,the discrete phase method and data processing were used to obtain the average CFD-CT value of each contactor.Finally,the distribution of CT value of each contactor was calculated,and the two evaluation indexes,i.e.,hydraulic efficiency and CT value were integrated.The results showed that the optimized schemes had different degrees of improvement on the CT value of the original contactor,of which the average CT value of the grid 1 was the highest,and the distribution of its CT value showed more concentrated,which indicated that its optimization effect was higher in both the hydraulic efficiency and the ozone oxidation efficiency.Therefore,it is considered that this optimization scheme can be applied to practical engineering.Finally,bubbling column was chosen and studied as an experimental model of two phase flow and determined the concentration of liquid ozone at different heights of columns to compare and verify the two phase flow simulation.