Study of gas condensation in transmission pipelines using a hydrodynamic model

Liquid condensation is a common occurence in pipelines used in transporting natural gas over substantial distance, such as in the case of transmission pipelines. In such pipelines, the percentage of liquid varies very widely depending on the composition of the transported gas, pressure and temperature conditions as well as the hydrodynamic behaviour of the system. The problem is further complicated by the fact that the pipeline may traverse undulating terrain thereby subjecting it to varying inclinations. Performance design of such pipelines is very intricate and must incorporate the hydrodynamic of the resulting two-phase system. Details of a viable compositional hydrodynamic model used for predicting pressure drop, quantity of liquid, pressure and liquid hold up profiles and gas/liquid flow rates and designing optimal locations of such components as liquid catchers, compressors and separators are presented. Results from a field case study are compared with other models. (P.J.B.)