Experimental Study On Erosion Corrosion Under Gas-liquid-solid Flow State Of 90° Elbow

In the shale-gas gathering pipeline system,the small solid particles and corrosive gases such as CO2 carried by the shale-gas will cause wear and corrosion on the pipeline components,and the wear and corrosion rate of the 90° elbow due to the large change of the flow field Straight pipes are dozens of times severe.Therefore,the study of 90° elbow wear corrosion law and the dominant type of wear and corrosion of elbow under erosion and corrosion conditions are urgent problems to be solved in the maintenance and production process of shale gas field gathering pipeline system.In response to this problem,this paper uses experimental and numerical simulation methods for research.Firstly,according to the erosion corrosion of shale gas gathering and transportation system,the horizontal-upward 90° elbow is determined as the research object.The force of solid particles in the gas-liquid-solid multiphase flow in the tube and the mutual interaction between the particles and the wall are analyzed.Goriv and Mandhane discriminant criteria were used to determine the gas-liquid phase flow pattern.The experimental scheme and numerical simulation scheme of erosion corrosion were determined by analyzing the corrosion mechanism of the elbow and the erosion wear mechanism,experimental research methods and prediction equations.A combined experimental device for erosion and corrosion,which can simulate the pure corrosion,pure erosion and erosion corrosion of the elbow of the gathering pipeline,was designed and built.The erosion corrosion test of 90° elbow was carried out.The erosion corrosion law and synergistic law of different positions of 90° elbow were studied by weight loss method.The influence of flow velocity and pH value on 90° elbow erosion corrosion was studied.The microstructure of the 90° elbow erosion corrosion was observed by scanning electron microscopy(SEM).The composition of the corrosion products was analyzed by X-ray diffraction(XRD).Based on the experimental results of erosion corrosion,a numerical simulation model of gas-liquid-solid multiphase flow at 90° elbow is established,and numerical simulation is carried out by using Fluent software.The flow field characteristics of 90° elbow are analyzed based on numerical simulation results.And the erosion wear characteristics,and through the comparison of experimental results and numerical simulation results,the synergistic law of erosion corrosion of 90° elbow was analyzed.In summary,the research results obtained in this paper reveal the wear and corrosion laws of 90° elbows under gas-solid two-phase?gas-liquid-solid three-phase conditions,and develop the wear and corrosion theory of pipes under specific flow fields,perfecting 90°Elbow erosion corrosion test method.And it is of great guiding significance to prevent and control the failure of 90° elbow and ensure the safe operation of shale gas production.