| With the increasingly serious problem of water shortage and the gradual increase of people’s concern about the environment,the global demand for water resources utilization and wastewater treatment continues to increase,and improving the comprehensive energy efficiency of wastewater treatment,increasing energy recovery and exploring new sustainable processes are gradually becoming the development direction of indirectly reducing carbon emissions in the wastewater treatment process.As one of the main pollution sources of water resources,oily wastewater has a wide range of sources,huge production and complex water quality.As filter separation and filtration technology will be accompanied by concentration polarization and the filter layer contamination in the process of treating oily wastewater,increasing total filtration resistance,a decrease in infiltration rate,a decrease in separation efficiency,and instability in the continuity of filter layer material used.The centrifugal separation process with cyclonic separation technology as the core often leads to a decrease in separation size and separation efficiency due to the fragmentation of oil droplets in oily wastewater,which cannot meet the goal of efficient separation for small size oil droplets.Therefore,to solve the above-mentioned problems in the oil-water separation process,this dissertation applies the super hydrophilic-submerged oleophobic copper mesh separation filtration technology to the oily wastewater treatment device and proposes a swirl-filtering coupling separator,which uses the turbulence generated by the cyclone separation technology to generate a high shear force on the surface of the filter layer,slowing down the concentration polarization and pollution blockage on the filter layer surface and reducing the total filtration resistance.At the same time,combined with surface modification treatment technology to achieve the surface selection of the filter layer for the wettability of the oil and water phases,it strengthens the filtration and separation performance of oily wastewater.The filter layer separation filtration with selective wettability improves the separation sharpness in the process of oil-water cyclonic separation,which enables the separation of oil droplets with smaller particle sizes and improves the separation efficiency of oily wastewater.This dissertation analyzes the separation mechanism of the swirl-filtering coupling separator,and designs a swirl-filtering coupling separator from two aspects: the main structure adopts traditional hydrocyclone for oil-water separation,and the mixed liquid enters from the double tangential inlet through the inverted cone at the top of the cyclone chamber to stabilize the flow,and is separated in the double cone structure,and discharged from the overflow pipe and bottom flow pipe in the same direction.The main structure of the double cone part of the filter layer structure design,the filter layer structure consists of surface-modified treatment with super hydrophilic-submerged oleophobic wetting characteristics of copper mesh filter separation,to achieve the goal of the treatment of oily sewage from the overflow,bottom flow and filter flow are collected or discharged.The theoretical basis of the fluid flow motion in swirl-filtering coupling separators is studied in terms of the fundamental equations of rotating fluid motion,the fundamental equations of vortex motion and the mechanism of oil droplet agglomeration and fragmentation.The Euler number and separation efficiency are used as the performance evaluation parameters of the swirl-filtering coupling separator,and are analyzed in detail from the evaluation perspectives of mass efficiency,commuted separation efficiency and overall efficiency.According to the design structure of the swirl-filtering coupling separator,compared to the single structure of separator with the same rated treatment capacity,the oil-water separation hydrocyclone is used as the research object,and the velocity field,pressure field,oil phase concentration and oil droplet particle size and other internal flow field distributions are analyzed by PIV test technology and CFD-PBM numerical simulation method under different treatment volume conditions.The velocity distribution of the flow field from the PIV test experiment and numerical simulation has a good consistency.The separation ratio,separation efficiency and Euler number of the hydrocyclone for oil-water separation gradually increase with the increase of the bottom flow outlet pressure,and the gradient of the increasing separation efficiency gradually decreases,and the increase of the bottom flow outlet pressure makes the overall energy consumption of the equipment increase.Since the copper mesh separation of the filter layer of the swirl-filtering coupling separator is a solidified porous media model,to obtain the resistance coefficients of the copper mesh filter separation with different pore sizes,an experimental system for measuring the resistance coefficients of porous media is designed,and the mathematical model of the flow resistance equation of the porous media in the cyclonic field is established through a combination of experimental tests and numerical simulations,using the porous leap model of computational fluid dynamics for the numerical simulation analysis of the filter layer,and compare the accuracy of the experimental test and numerical simulation results.By analyzing the contact angle of the solid surface and the force on the droplets,the contact angle changes of the filtering copper mesh in four mixed states of oil and water,such as water droplets and oil droplets in the air,oil droplets in water environment and water droplets in oil environment,before and after the surface modification treatment were discussed.The analysis of the adsorption effect on the surface of the copper mesh film was realized by testing the adsorption performance of water under oil and the number of times the copper mesh was recycled with the adsorbed water.The effect of surface wetting characteristics of copper mesh on oil-water separation performance was studied by analyzing the effect of different oil products,different oil content volume fractions and different mesh sizes on oil-water separation performance.The water droplet spreading and oil droplet aggregation on the super hydrophilic-oleophobic solid surface are analyzed using time simulation.In the studied time range,the water droplet spreading coefficient on the hydrophilic solid surface gradually increases with time,and the oil droplet spreading coefficient on the submerged oleophobic solid surface increases slowly and then remains stable.Based on the geometric structure model of hydrocyclone for oil-water separation,the initial structure of the filtering hydrocyclone coupling separator is determined,and the Euler number and separation efficiency are taken as the objective function,and the response surface optimization method is applied to optimize the geometric structure;through the analysis of the influence of the material performance parameters of the filter layer,the influence of the parameters about the porosity of the filter layer,the thickness of the filter layer,the resistance coefficient and the permeability on the separation performance is obtained The influence of treatment volume and oil content volume fraction on the flow field characteristics and separation performance of the filter cyclone coupled separator is analyzed by numerical simulation technology;the experimental evaluation study of the separation performance of the cyclone-fliter coupled separator is carried out,and the influence of different treatment volumes and oil content volume fraction on the separation effect of the filtering hydrocyclone coupling separator is comparatively studied.In this dissertation,the macroscopic separation performance and microscopic flow field and oil droplet behavior characteristics of the swirl-filtering coupling separator reveal the law of filtered cyclone coupled separation,which provides a new idea to solve the problems of concentration polarization and filter layer contamination in the filtered separation process and limit the refinement of cyclone separation particle size,which can further improve the separation performance of the swirl-filtering coupling separator and expand the application field of swirl-filtering coupling enhanced separation. |
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