CO2 capture using a superhydrophobic ceramic membrane contactor

The wetting and fouling of a membrane contactor deteriorated performance of the membrane gas absorption system for CO2 post-combustion capture in coal-fired power plants. To solve these problems, in this study, a superhydrophobic ceramic (SC) membrane contactor was fabricated from an alumina tube with a ZrO2 layer by means of grafting with fluoroalkylsilane (FAS) in a triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane solution. The performances of the SC membrane contactor and polypropylene (PP) hollow fiber membrane contactor were compared through experiments conducted in a CO2 absorption experimental system using a monoethanolamine (MEA) aqueous solution. Although the membrane fabrication cost per effective membrane area (CPA) of the SC membrane is 12.5 times that of the PP hollow fiber membrane, the SC membrane fabrication cost per absorbed CO2 flux (CPC) was lower than that of the PP membrane. For the SC membrane, the detrimental effect of wetting can be alleviated by periodic drying to ensure a high CO2 removal efficiency (>90%). Drying does not work for the PP membrane because the swelling of the PP fibers is irreversible. The SC membrane contactor exhibited a better anti-fouling ability than the PP membrane contactor because the superhydrophobic surface can self-clean. To ensure a continuous, high-efficiency CO2 removal, a method was proposed in which two-hollow fiber SC membrane contactors operate alternately with the addition of periodic drying. The SC hollow fiber membrane contactor shows great potential in real industrial CO2 post-combustion capture because of its good anti-wetting and anti-fouling features.