| In order to reduce the environmental pollution and waste of resources,how to deal with the problems of sewage and mud sand in the produced fluid of oil field has become a difficult problem to be solved urgently in the oil field.Mud sand is difficult to separate because of its fine particle size,oil and gas quality and production are affected.It is urgent to use one-time oil-water sand three-phase separation equipment.In this paper,based on the traditional two-phase swirl separation device,an efficient and compact fine-grained sand separation cyclone is designed and optimized for the fine-grained mud sand containing oily water.Based on the theory of rotating flow separation mechanism,multi-phase flow technology and computational fluid dynamics,a three-phase cyclone slurry concentration and separation device was designed.The numerical analysis of its initial structure model is carried out by using FLUENT software.The influence of structural parameters on the performance of three-phase cyclone is studied,and the structure parameters are optimized to improve the separation performance of the three-phase cyclone.Finally,the experiment is guided by simulation,which provides a reference for the research and development of the separation device.The main results are as follows:(1)The overall design scheme and the main structural parameters and dimensions of the three-phase cyclone,such as swirl cavity,inlet,overflow and underflow,are determined.The RSM and Mixture models are used to describe the multiphase turbulence in a three-phase cyclone.By comparing and analyzing the experimental results,it is found that the model and its simulation results are reliable.(2)The performance of the three-phase cyclone is affected by changing the structure parameters(inlet,overflow,height-diameter-ratio and underflow).The inlet size has no effect on the flow field distribution,but has a significant effect on the pressure drop and separation performance.The pressure drop decreases with the increaseof inlet size,and the ratio of inlet width to height is the lowest,while the separation efficiency of mud and sand increases with the increase of the inlet diameter,and the oil separation effect is better when the inlet diameter is 0.24 D.The diameter of the overflow has a greater effect on the velocity of the flow field than the length of the overflow,and has a negative correlation with the pressure drop.The separation performance is greatly affected by it.The ratio of height to diameter has a great effect on the velocity of the flow field,the pressure drop is less affected by the small cone section,and the separation performance is less affected by the large cone section,while the size of the underflow has a greater effect on the pressure drop and separation performance.(3)The genetic algorithm(GA)is used to optimize the weights and thresholds of BP neural networks,and the structural parameter optimization model(GA-BP)is constructed.The corresponding relations between the structural parameters and the separation efficiency are analyzed and predicted.The optimum structural parameters are as follows: inlet diameter 0.27 D,overflow diameter 0.02 D,height-diameter-ratio 3.0and underflow diameter 0.16 D,the maximum separation efficiency of mud and sand is71.93%,and the error with the actual value is only 5%.It is 18.53% larger than the original model.Therefore,this method provides a new optimal design method for multiphase flow separation equipment or device.The research in this paper is of theoretical significance to the research and development of a new three-phase cyclone separation device and the improvement of separation mechanism.At the same time,it provides a feasible scheme for the efficient treatment of sludge-bearing oil wastewater produced in oil fields. |
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