Numerical simulation of black powder removal process in natural gas pipeline based on jetting pig

Black powder is a common contamination problem for natural gas pipeline all over the world. In this study, a method based on the jetting pig is proposed to remove the black powder in natural gas pipeline. Numeric simulations based on the computational fluid dynamics method, were conducted to investigate the dynamic migration process of black powder particles in the jetting field by using the multiphase flow model. Diameter of black powder particles, initial stacking concentration, stacking height and the inlet pipeline pressure were taken into consideration to study the black powders jetting cleaning effect. By using discrete phase model, considering the coupling between solid and gas, the path of black powder with different diameters was traced, and the movements of black powder in horizontal and vertical directions were analyzed, which reflect the diffusion law of black powder. Our results show that the higher the initial stacking concentration and larger the particle diameter, the lower the cleaning efficiency of black powder. The horizontal position of black powder with particle diameter of 20 μm were obviously ahead of other kinds of particle, and the horizontal velocity decreased slowly. The vertical velocity of black powder with particle diameter of 20 μm were also obviously lower than other kinds of particle. While other five kinds of particle with particle diameter over 20 μm would gradually stick to the wall until they stop moving and secondary settlement will occur. Our results can contribute to the mechanical design of jetting pig and optimal design of pigging process for black powder cleaning in natural gas pipeline.