Black Powder Removal Method In Natural Gas Pipeline Based On A Jetting Pig

Acid gases and free water in long-distance natural gas pipelines can corrode uncoated tubes and generate large amounts of black powder.Black powder will generally be scattered in the pipe or adhered to the pipe wall,its existence will bring about mangy problems.It can corrode tube detection devices,block the valves,reduce the effective area of circulation,and even invalidate the fuel supply device of pipeline terminal.Considering all the problems,it is very important to find out effective method to remove black powder safely and efficiently.The natural gas pipeline cleaning device combines the cup's scraping function with the nozzle's jetting function together to remove black powder.The jet part is in the form of a main nozzle combined with eight side nozzles.A mechanical model with a by-pass pipe pig is established theoretically,which reveals the movement of the by-pass pig.The simulation of jetting flow field is completed by computational fluid dynamics method combined with actual gas model.A series of simulations are conducted by changing the main nozzle's diffusion angle,diffusion length,diameter and length of the horizontal part,and also the side nozzle's injection angle and diameter.Based on the flow velocity and turbulent kinetic energy in the flow field,the best structure parameters are gained.The multiphase flow model is used to simulate the black powder removal process.Change the diameter,stacking concentration,stacking height of the black powder and the pipeline pressure to complete the simulations.After calculation,the transfer speed of black powder is compared with the operating speed of the pig to verify the feasibility of jet cleaning.By using discrete phase model,considering the coupling between solid and gas,the path of black powder with different diameters is traced,and the movement of black powder in horizontal and vertical directions are analyzed,which can reflect the diffusion law of black powder.