Research On Oil-water Flow And Separation Characteristic Of Sump Caisson

The sump caisson as the last stage oil-water separation equipment of offshore oilfield production wastewater,provide a buffer channel for the discharge of sewage,so can effectively reduce the possibility of marine pollution caused by oil spill accidents,with the characteristics of simple structure,less occupied space,large treatment capacity,etc.,widely used in offshore Oilfield open drain system.In this paper,a set of "U" experimental process is established for the first time to simulate the running state of sump caisson in seawater.The experimental model is simplified according to the geometrical similarity principle,operation parameters determined by the on-site sewage retention time,and the microscopic technique is used to count oil droplet diameter.Experimental study the influence of operating parameters and structure parameters on the separation performance of sump caisson,and use the numerical calculation analyzes the effects of structure parameters on the flow characteristics of oil-water two-phase flow in the sump caisson based on the experimental model.To provide theoretical basis for sump caisson structure optimization and industrialization.Comprehensive the sump caisson’s basic separation characteristics and flow characteristics the results show that,the existence of the inclined plate makes the mainstream obtain a larger horizontal velocity component,effectively reduce the difficulty of oil drop and prolong residence time,make the oil droplet diameter decreases along the axial fluctuation.In the inclined plate separation area,the mainstream frequent steering,and a low velocity zone formed below the inclined plate the velocity is about half of the mainstream velocity.The flow of fluid impinging on the wall of the caisson,and the upward flow formation a vortex is conducive to the accumulation of oil droplets in the plate,the separation efficiency is about 53% of the total separation efficiency,at the end of it average particle diameter is smallest;In inlet area exist obvious Jet aeration,preliminary separation out of more than 100μm large droplets,separation efficiency after the inclined plate separation zone,the vortex flow field is formed at the top of the first plate after the flow is encountered;The mixed fluid flowing out of the inclined plate separation zone forms a large eddy in the bottom of the last inclined plate,and the average particle diameter of oil droplets is larger than that of the end of the inclined plate area,the separation efficiency is slightly higher than that of the natural subsidence area.Comprehensive comparative analysis results show that the separation efficiency increased with the increasing of inlet oil content,there is a high efficiency range of inlet flow rate,installation of inclined plate can increase the turning point of concentration,the treatment capacity range of sump caisson,turning point of concentration increased from 800mg/L to 1500mg/L,the treatment capacity is increased to 160L/h;The first piece of inclined plate installed in the distance from end of the inlet 100 mm,the formation of the refluxing swirl in inlet area is elliptic,with the best separation efficiency is about 22%;The inclined plate installation distance is 80 mm and 100 mm,between the inclined plates with smaller velocity,static separation space below the inclined plate is larger.