Two-phase gas-condensate flow in pipeline open-network systems

Even if gas transmission occurs after the necessary processing of the gas has been completed, condensation still occurs in the natural gas transmission and/or distribution systems. The quantity of the condensate formed will not only depend on composition, pressure, and temperature, but also on the unequal splitting phenomenon that takes place at T-junctions in a network system. This paper investigates the splitting phenomenon in horizontal-branching T-junctions. The compositional hydrodynamic model developed at Pennsylvania State U. is used to evaluate gas-condensate flow in a pipeline under steady-state conditions. Using a double-stream model for splitting analysis at T-junctions, the mass-liquid-intake fractions are determined. The junction is considered as a separator and the new compositions are calculated at the run and at the branch of the junction. Although quantitative validation of the model is limited by the incompleteness of the available data, a reasonable qualitative match of experimental data is achieved. The results demonstrate the predictive capability of liquid route preference in two-phase natural-gas/condensate flow at T-junctions. In addition to liquid split, compositional split is tested using polychlorinated biphenyl (PCB) as the focal point. It is found that the concentration of PCB is distributed in direct proportion to the liquid preference route, and the PCB concentration in the delivery points can be higher or lower than the inlet concentration at the supply point.