CFD study of CO2 separation in an HFMC: Under non-wetted and partially-wetted conditions

Abstract

This paper applies computational fluid dynamics (CFD) to explore a numerical simulation of mass transfer in a hollow fiber membrane contactor (HFMC) for non-wetted and partially-wetted conditions. A comprehensive 2D mathematical model based on the finite element method (FEM) was developed for modeling a gas–solvent HFMC which was applied to CO2 removal from a CO2/N2 gas mixture. Aqueous mono-ethanol-amine (MEA) solution was used as the CO2 absorbent and flowed in the fiber bore and then the gas mixture was circulated counter-currently in the shell side of HFMC. The average outlet CO2 concentrations, the absorption flux, overall mass transfer coefficient and the CO2 removal efficiencies are parametrically simulated by using the operational parameters such as gas and solvent flow rates, operating temperature, the fiber porosity and other geometrical characteristics. As a novel work, the effect of opposite fluid direction, i.e. absorbent flow in the shell and gas mixture in the fibers, on the mass transfer coefficient and CO2 removal efficiency was also taken into account for further considerations. It was concluded that while gas flows in the fibers and solvent flows in the shell an HFMC with a smaller size can be used. Furthermore, the effect of aqueous solution types such as MEA, 2-amino-2-methyl-1-propanol (AMP) and NaOH on the overall mass transfer coefficient and on the percentage removal of CO2 was investigated numerically and interesting results were obtained. Generally, the results showed that a reasonable agreement exists between the experimental and CFD results.