Simultaneous separation of H2S and CO2 from natural gas by hollow fiber membrane contactor using mixture of alkanolamines

In the present work we studied the use of a membrane contactor system for simultaneous absorption of H2S and CO2 from a gas mixture similar to natural gas. MDEA solution and mixtures of MDEA/DEA and MDEA/MEA were used as absorbent liquid. PVDF and PSf hollow fiber membranes were used in the membrane contactor modules. Design of experiments were carried out by Taguchi method in a manner that a systematical investigation of the effect of operational parameters (temperature, pressure, gas and liquid flow rates, absorbent concentration and acid gas content of the feed), in addition to the effect of membrane material and absorbent liquid, was implemented on process performance parameters including removal efficiencies, overall mass transfer coefficients and H2S to CO2 selectivity. The results indicate that liquid side resistance is negligible in comparison with membrane and gas side resistances. Both membranes were wetted by the liquid, but PSf suffered more. The presence of a dense layer in membrane side adjacent to the liquid, changes the influence of operational parameters. It was observed that increasing absorbent concentration had a different effect in the presence or absence of CO2. Addition of MEA enhanced the removal efficiencies while DEA had no significant effect.