Study On Typical Pipe Fitting's Flow Field And Solid Particle's Deposition Law In Gathering System Of Natural Gas

Solid particle deposition appears in gathering system during gathering and transferring of high-sulfur natural gas which can lead to gathering ability decresing,or even stopping production.Therefore,it is necessary to have a research on flow behavior of gas and solid phase,diameter change and distribution of solid particles when natural gas flows through some typical pipe fittings in gathering system,such as metering separator,restriction orifice(valve),manifold and tee joint.The study will have important engineering significance for predicting the deposit location of solid particles,raising the security level of gathering and transferring system and ensuring stable operation for gathering and transferring system.This work investigated computational fluid dynamics approach to predict the flow behavior of the complex gas–solid two-phase flow in a three-dimensional(3-D)straight pipe,metering separator and restriction orifice.By comparing different turbulence model,gas–solid two-phase flow and population balance model(PBM),Standard k-? model and Eulerian model were choosed to simulate turbulent flow and gas–solid two-phase flow,Luo model and Ghadiri model were selected for aggregation and breakage mechanisms of solid particles.Through simulation the conclusitions are as follows:The diameter of particles on the centre of circular pipe is the smallest,and near the wall of the pipe is the largest.With the flow distance and import particle concentration increasing,the diameter of particles is increased and the arrangement of pipe has a great influence on the particle diameter distribution.There are different sizes of low speed region and whirlpool region in metering separator.Natural gas flows steady in the mainstream direction and there are many stronger secondary flow in the direction perpendicular to the mainstream.The particles diameter range is less than 10?m,overall the aggregation of particles is weaker and gravity sedimentation is dominated.There is a leptokurtic low temperature area after natural gas flows through a restriction orifice and the area has a growing trend as throttling pressure drop and orifice diameter ratio increased.The minimum temperature is located at the central axis of pipe and the temperature near the wall of pipe will be higher than the centre.The particle diameter increases quickly once the gas and particles flow past the restriction orifice.The characteristics of particle distribution is that a peak on behalf of smaller diameter particles appears in the center of the pipe downstream of the orifice,and the diameter of particles which are located in the surrounding of the peak is much larger.As natural gas continues to flow along the pipe,the particle diameter distribution will reach stable state finally.What's more,as the throttling pressure drop and import particle concentration increases as well as the decrease of the orifice diameter ratio,the diameter of the particles behind orifice plate shows a trend of increase.