Low-temperature vacuum stripping of CO2 from aqueous amine solutions using thin-film silicalite-filled PDMS composite membranes

Abstract

Carbon dioxide (CO2) recovery by vacuum stripping technology using membranes was studied as an alternative to the desorption process at low temperatures (below 120°C) in conventional aqueous amine absorption process. Composite membranes were prepared by coating hydrophobic silicalite-filled polydimethylsiloxane (PDMS) layers on polyethylene (PE) porous supports and used as new membrane strippers for CO2 recovery to prevent the typical pore wetting problem of hydrophobic porous membranes. Aqueous 30wt% solutions of monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) were used as absorbents in the desorption process. CO2 fluxes were measured under various operation conditions, such as different vacuum pressures, stripping temperatures, CO2 loadings, types of amine solutions and operation time. CO2 stripping fluxes increased with increasing temperature and CO2 loading of amine solutions as well as with decreasing stripping pressures because of the enhanced upstream and downstream driving forces. CO2 stripping fluxes were much higher in the TEA and DEA solutions than in the MEA solutions. The thin-film silicalite-filled PDMS composite membranes showed excellent long-term stability in the vacuum stripping process when compared with porous polytetrafluoroethylene (PTFE) membranes.