Removal of carbon dioxide from pressurized landfill gas by physical absorbents using a hollow fiber membrane contactor

This article details the physical absorption of CO₂ from synthetic landfill gas (containing 40% CO₂ and 60% CH₄) using a hollow fiber membrane contactor (HFMC) at elevated pressures in the range of 0.1–1.2 Mpa. Polyethylene glycol dimethyl ether (Selexol) was used as absorbent in HFMC for the first time. The effects of operating parameters on the absorption process were investigated. The results show that the use of Selexol as absorbent gives higher CO₂ absorption fluxes and removal efficiencies compared to water. The highest absorption flux reached 1.61 × 10⁻³ mol/m² s at 1.2 Mpa. A 2D mathematical model and a resistance-in-series model were used together to analyze the absorption process and membrane wetting at different pressures. Due to the relatively lower surface tension of Selexol, the absorption process suffers more negative effects from membrane wetting at higher pressures. The change of mass transfer resistances in each phase along with the elevated pressures was theoretically calculated. The results reveal that even when slight membrane wetting occurs, resistance in the wetted part of the membrane is nonnegligible.