Research On Coalescence And Breakage Characteristics Of Oil Droplets In Hydrocyclone Under The Condition Of Gas-containing

Hydrocyclone has been extensively used in multiphase medium separation of petrochemical and municipal environmental protection fields because of its convenient operation,small footprint,large treatment capacity and high separation efficiency.Especially it plays an important role in the rapid separation of produced liquid in the oil field and efficient treatment of oily sewage.For a long time,the researches of hydrocyclone have focused on the strengthening method of separation performance,the design and optimization of novel structure and broadening the field of application and so on.With the in-depth study of the motion characteristics of the discrete phase in the hydrocyclone,some scholars realize that the collision,coalescence and breakage of oil droplets are critical factors affecting the separation performance of the hydrocyclone.As Population Balance Model(PBM)can better predict the size change and distribution of oiling droplets,it provides help for the research and analysis of discrete coalescence and breakage characteristics,and gradually attracts a large number of scholars to undertake research.In addition,with the increase of oil wells with high gas-liquid ratio year by year,the existence of gas phase has always been an unavoidable problem in the popularization and application of hydrocyclones,especially the continuous maturity of research methods for simulating droplet collision in recent years.The research on the influence of gas on hydrocyclone has been transferred from the flow field characteristics of the pressure field,velocity field and the concentration field at the macro level to the micro-level particle collision theory between liquid-liquid,gas-liquid,liquid wall and gas wall.This paper takes the conventional equal cross-section twinned tangential inlet double-cone hydrocyclone as the research goal,using theoretical analysis,numerical simulation,laboratory experiments,particle size measurement,oil analysis and High Speed Video(HSV).Visualization experiments were conducted to screen the applicability of different coalescence and crushing model combinations of the hydrocyclone,and the variation characteristics of oil droplet size and separation performance in the cyclone field under different gas conditions were analyzed and evaluated.Thus,we can grasp the growth and change law of the discrete phase oil droplets in the hydrocyclone flow field,fundamentally deepen the separation and application of the hydrocyclone,and provide a theoretical basis of reasonably determining the particle size distribution and growth characteristics of the dispersed phase oil droplets in the hydrocyclone flow field.Strong study on the movement characteristics of oiling droplets in the hydrocyclone to improve the separation performance of the hydrocyclone.The Computational Fluid Dynamics(CFD)is used to load the PBM model conditions,and the Reynolds Stress Model(RSM)is selected to carry out numerical simulation of different coalescence and breaking model combinations under conventional double-cone hydrocyclones.The volume fraction of the oil phase and the particle sized distribution of oiling droplets in hydrocyclones under different combination schemes is analyzed,and the simulation results of different schemes are screened and verified by indoor particle size analysis and separation performance experiments.The combination scheme for coalescence model and crushing model which can simulate the variation characteristics of oiling droplets in hydrocyclone is obtained.Then,a comparative study is made on the relationship between the oil droplet size and its turbulent kinetic energy distribution of the hydrocyclone,which shows that they are inversely proportional to each other,and reveals the influencing factors of oil droplet coalescence and breakage in the swirl field.Through the study of the influence of separation performance,it is shown that under the optimal model combination scheme.Mass separation efficiency of hydrocyclone increases at first and then decreases to the treatment capacity and split ratio,and the best operation parameters are obtained.Based on the optimal coalescence and breaking model combination scheme,the CFD-PBM numerical simulation coupling method is used to compare the oil droplet coalescence and breaking changes in the hydrocyclone with different inlet gas content and oil concentration,and the simulation results are sorted out to analyze the oil droplet size,turbulent kinetic energy,tangential velocity and axial velocity in different separation sections,such as swirl cavity,large cone section and small cone section of the hydrocyclone.The results show that the continuous increase in the inlet gases content will affect the turbulent kinetic energy and axial velocity distribution in the hydrocyclone,but has little effect on the tangential velocity,so that the internal oil droplet size decreases at first and then increases,while under the proper gas content condition,the increase of inlet oil concentration will promote the oil droplet coalescence and increase the internal oil droplet size.The indoor experimental system of oil droplet coalescence and breakage analysis and separation performance in the hydrocyclone under the gas-bearing condition is constructed,and the swirl flow field visualization study is realized with the help of the HSV system.The changes of the gas core of different gas injection condition and the influence on the internal oil core of the oil-bearing condition is compared.Experimental measurements of oil droplet size and oil concentration of hydrocyclone inlet,overflow and underflow under different inlet gas content and oil concentration were quantitatively analyzed by particle size measurement and oil analysis system.Finally,changing rules of oil droplet sizes and separation efficiency in the hydrocyclone under the condition of gas were obtained by the experimental results,and compared with the simulation results to verify the accuracy of the simulation results.