Simulation of CO2 absorption by solution of ammonium ionic liquid in hollow-fiber contactors

• Mathematical modeling of gas separation using porous polymeric membranes.
• Development of 2D mass transfer approach for simulation of membranes.
• Application of finite element method for simulation of membrane separation.

Membrane-based chemical absorption of CO2 from gas mixtures containing CO2 using tetramethylammonium glycinate solution was studied in this work. The absorption media studied in this work involves a porous membrane contactor which is utilized as a physical barrier for contacting feed gas stream and the chemical solvent. The considered membrane module type was hollow fiber. The equations of concentration for both CO2 and solvent were derived and solved numerically using computational fluid dynamics (CFD) approach. The equations were solved in two dimensions and in cylindrical coordinate, i.e. axial and radial directions in order to obtain the concentration and mass transfer flux of CO2 and solvent in the hollow-fiber contactor. Both convection and diffusional mass transfers were taken into account in the simulations. The findings of CFD simulation demonstrated that as the flow rate as well as the concentration of the absorbent increased, the CO2 removal from gas mixture enhanced; while, the enhancement of gas flow rate declined the removal rate of CO2 in the contactor. The proposed simulation method revealed to be capable of predicting CO2 capture from gas mixtures in membrane contactors.