Mathematical modeling for the simultaneous absorption of CO₂ and H₂S using MEA in hollow fiber membrane contactors

A comprehensive two-dimensional mathematical model was developed for the simultaneous transport of carbon dioxide and hydrogen sulfide through hollow fiber membrane (HFM) contactors while using monoethanol amine (MEA) as the chemical solvent. The model considered non-wetting and partial-wetting conditions where the gas mixture and the solvent fill the membrane pores for countercurrent gas-liquid flow arrangement. Axial and radial diffusion were considered inside the fiber, through the membrane, and within the shell. The model was validated for physical and chemical absorption of CO₂ using water and MEA, respectively. The model results were in excellent agreement for the physical absorption while considering non-wetting conditions. However, for chemical absorption the model showed excellent agreement with the experimental data while considering 10% wetting for polypropylene (PP) when 0.005 M MEA was used, and 50% wetting for polyvinyllidene fluoride (PVDF) when 2 M MEA was used. The effect of MEA concentrations, gas and liquid velocities were studied on the simultaneous removal of CO₂ and H₂S. The % removal of CO₂ increased while increasing the MEA concentration. As for H₂S, low concentration of MEA was efficient in complete removal. The % removal of CO₂ decreased while increasing gas velocity, whereas, H₂S % removal did not change with increasing gas velocity when operating at low gas velocity. However, the effect is more pronounced while operating at high gas velocities. Both CO₂ and H₂S % removal was increased with increasing the liquid velocity. CO₂% removal increased slightly, while H₂S % removal increased substantially while operating at high gas velocity.