Research On Emulsification Mechanism By Shear And Structure Improvement Of Throttle Valve Used In Crude Oil Exploitation And Transportation

Throttle valve as an important industrial base for fluid transmission and control is widely used in the process of crude oil production,transportation and separation.In the process of operation,throttle valve causes the breakup of the dispersed phase droplets in the oil-water mixture due to the intense shear and the emulsification which would increase the difficulty of subsequent oil-water separation.Therefore,the research on the development of low shear throttle valve has a high practical value to improve the separation efficiency.In domestic,only a few studies have been carried out preliminary structural design and feasibility study of low shear throttle valve until now.However,the design analysis method and related mechanism have not been in-depth studied yet.Firstly,the mechanism of droplet breakup caused by throttle valve,coalescence mechanism of droplet in cyclone field and low shear throttle valve at domestic and abroad are described in this thesis.The high-water content of oil-water mixture through the throttle orifice of dispersed phase droplet breakup mechanism is studied by particle dynamic analyzer under different experimental conditions,and the accuracy of PDA measurement is verified by CFD numerical simulation.Experimental results showed that the variation of viscosity,interfacial tension and flow rate of dispersed phase had a certain impact on the droplet breakup,and the variation of the tangential velocity gradient has the greatest influence on the droplet breakup.CFD-PBM numerical simulation and experimental method are used to analyze the droplet size after the flow channels with different single cage hole.The coalescence model in PBM is revised to turbulent-model.The modified PBM model is used to simulate the droplet size of different types of flow channels,and the basic structure of the low shear throttle valve is determined as tangential valve cage and venturi cyclone chamber.Based on the basic structure of low shear throttle valve and the structure characteristics of the conventional plunger throttle valve,preliminary structure of the low shear throttle valve would be determined.The response surface method and the modified CFD-PBM numerical simulation method are used to optimize the key structure of low shear throttle valve,and finally the overall structure size of the low shear throttle valve would be determined.In order to verify the feasibility and the performance of the low shear throttle valve,a low shear throttle valve and plunger valve have been manufactured.Meanwhile,a performance evaluation device for throttle valve has been built up.Based on the typical characteristics of oil and water mixture,the experiment investigates the variation of droplet diameter,which through the low shear throttle valve influenced by the different conditions.The dispersed droplet diameter through low shear throttle valve is compared with conventional valve with different operating parameters.The result showed that low shear throttle valve could maintain high performance with pressure of 0.05MPa,flow rate of0.5m~3/h,and oil concentration of 12000ppm.The droplet diameter of the low shear throttle valve is larger than that of the conventional valve under any experimental conditions,which verifies the performance advantage of the low shear throttle valve.In this paper,the research of low shear throttle valve is carried out from the view of mechanism,structure and characteristics,and would provide the necessary technical support for upgrading of domestic wellhead throttle valve used in crude oil exploition and improvement of separation efficiency of gathering and processing equipment.