Study On Coalescence And Migration Characteristics Of Oil Droplets In Non-Newtonian Fluid Swirling Field

Due to the presence of polymers in oilfield production fluid,the difficulty of oil-water separation treatment is greatly increased.The hydrocyclone has the characteristics of simple structure,fast processing speed and high separation efficiency,and is widely used in the petrochemical industry day by day.Therefore,grasping the coalescence characteristics and migration rules of oil droplets in hydrocyclone under polymerization conditions has important practical significance and engineering application value for solving oil-water treatment problems in oil fields.Firstly,the research progress of the swirling separation technology,the non-Newtonian fluid swirling field and the coalescence,breakup and migration trajectory of oil droplets in the swirling field are summarized separately.Based on the theory of fluid mechanics and non-Newtonian flow field of hydrocyclone,specific research contents and methods are proposed.Taking the spiral-conducting inner cone hydrocyclone as the research object,the Solidworks,Gambit and Fluent software was used to model,mesh and grid independence test for the hydrocyclone.Polyacrylamide solution with the concentration of 100～700 mg/L was used to carry out rheological characteristics test.The power-law fluid model was used for regression analysis to obtain its rheological equation and correct the calculation of the flow field in the hydrocyclone under polymerization conditions.The PBM model was used to study the effects of different polymer concentrations(100～700mg/L)on the viscosity field,velocity field,pressure field,coalescence and separation characteristics of oil droplets in the hydrocyclone under small-sized oil droplets.It is found that the polymer concentration has a greater effect on the coalescence and separation efficiency of the oil droplets in the hydrocyclone.As the polymer concentration increases,the viscosity resistance increases,the centrifugal force on the oil droplets decreases,and some of the oil droplets coalesce near the side wall and flow out from the underflow,the oil-water separation efficiency gradually decreases.In the case of polymer concentration of 500mg/L,the influence of inlet flow rate,split ratio,inlet oil concentration and oil droplets size on coalescence and separation of oil droplets was studied.It is concluded that the appropriate increase of the above operating parameters under polymerization conditions can increase the coalescence probability of oil droplets at the axis of the hydrocyclone,thereby improving the separation efficiency.The DPM model was used to study the trajectory and separation efficiency of oil droplets in the hydrocyclone,it is found that the increase of polymer concentration would prolong the axial distance and migration time of oil droplets in the hydrocyclone,and the velocity amplitude of oil droplets in the x and y direction also decreases,which would increases the difficulty of oil droplet separation.Increasing the inlet flow rate and oil droplets size can improve the capture efficiency of oil droplets under polymerization conditions.As the flow rate increases from 1m~3/h to 5m~3/h,the number of oil droplets captured by the overflow increases from 176 to 367,and the movement speed of the oil droplets in all directions is increased,and the residence time in the hydrocyclone is also reduced.And the oil droplets size has a more significant effect on the number of oil droplets captured by hydrocyclone overflow.when the size of oil droplets increases to 0.5mm,the capture efficiency of oil droplets by hydrocyclone overflow reaches 97.03%.