Gas-liquid membrane contactors for carbon dioxide separation: A review

Membrane gas–liquid contactors have been developed to reduce the capital cost and energy consumption of conventional CO2 absorption and stripping columns. As a hybrid technology of membrane separation and amine absorption, these units can improve the gas absorption process by generating 400–1500% greater mass transfer area per unit volume leading to smaller equipment sizes. Regeneration of CO2 can occur within a membrane contactor below the boiling point of the solvent, leading to lower energy consumption. Over recent years, a vast array of polymeric and ceramic materials have been considered for membrane gas–liquid contactors and an array of solvents have been used including amines, potassium carbonate, ammonia and amino acids. The major technical challenge with membrane contactors is the wetting of the membrane pores with solvent, which reduces the mass transfer coefficient. However, other factors such as the choice of solvent, the placement of the solvent on the shell or lumen side and the operational temperature are also critical to success. This review describes the recent progress in membrane gas–liquid contactor technology for CO2 separation in terms of the materials, solvents, modules and processes and provides direction on where research can best be directed in the future to enhance the feasibility of the technology’s industrial application.