Subsea natural gas dehydration in a membrane contactor with turbulence promoter: An experimental and modeling study

Abstract

Subsea natural gas reservoirs are usually saturated with water vapor that causes corrosion in pipelines and forms hydrates blocking pipes and installations. In this work, the viability of the subsea natural gas dehydration in a non-porous membrane contactor was evaluated experimentally and by modeling.A flat sheet composite membrane is employed as the membrane interface and a structured packing turbulence promoter was installed at the gas side. The water flux and the outlet dew point were measured at different operating conditions (e.g., pressures, liquid and gas flow rates). To estimate simultaneously the permeability, overall mass transfer coefficient, and outlet water content, a systematic approach was applied and a 1D-2D model was developed bypassing the liquid phase mass transfer resistance and solved numerically coupled with a developed correlation for axial dispersion coefficient. The results show an increase in transmembrane water flux to the highest values of 72 g/m2h and 53 g/m2h with increasing gas flow rate and pressure to 500 ml/min and 11 bara, respectively. The effect of using a turbulence promoter was evaluated, and a good agreement between the simulated and experimental results was obtained. The mass transfer resistance of a dense layer was found to be dominating compared to that of gas and liquid phase and the high pressure and high gas flow rate are favored in this process. This study shows that membrane contactor enables effective water separation under subsea conditions. Installation of a turbulence promoter in the gas phase significantly reduced the water content in the outlet gas stream.