Experimental and modeling of CO2 removal from gas mixtures using membrane contactors packed with glass beads

The efficiency of gas removal using hollow fiber membrane (HFM) contactors and liquid solvents is determined by several factors. The liquid film resistance has been identified as one of the important factors affecting the overall mass transfer coefficient. The present work describes the use of spherical glass beads as additional packing in the shell (solvent) side to act as solid baffles which should impart stirring effect in the flowing solvent and increase its velocity. These two effects should decrease the liquid film resistance and consequently enhance the gas removal efficiency. Two types of custom-made hollow fiber membrane contactors (HFMC) were constructed from thick-walled acrylic tube (20 mm ID, OD 30 mm) and equipped with the commercially available poly(tetrafluoroethylene-co-perfluorinated alkyl vinyl ether) (PFA) hollow fibers. In one type of the contactors, glass beads were introduced in the shell side. The two types of contactors (with and without beads) were tested and compared in terms of CO2 removal efficiency from gas mixtures (5% CO2 - 95% CH4) using aqueous sodium hydroxide and several amine solutions. Different parameters were studied to evaluate the performance of the membrane contactors at feed gas pressures up to 25 bars. The obtained results indicated an increase of up to 21% enhancement in CO2 removal efficiency when the shell compartment was packed with the glass beads. The results obtained from the overall mass transfer coefficient model showed good agreement with those of the experimental data.