Evaluation of mass transfer characteristics of non-porous and microporous membrane contactors for the removal of CO2

A comprehensive experimental investigation of membrane gas absorption for the removal of carbon dioxide (CO2) using non-porous silicone rubber and porous polypropylene hollow fibre membrane contactors was performed. Water, monoethanolamine (MEA) and diethanolamine (DEA) were used as absorbing solvents. Performances of membranes for gas absorption were evaluated as mass transfer through the membranes, selectivity and removal efficiency of CO2. Water flow rate affected the mass transfer through the porous membrane more than non-porous one. But, increase in flow rate of amine solutions has not affected the mass transfer for both membranes. Mass transfer, compared with water, increased four and eight times roughly for non-porous and microporous membranes, respectively, when amine solutions of 10 wt.% were used. Amine solutions also increased the CO2 selectivity 2 and 4 folds roughly for non-porous and microporous membranes, respectively. Basic absorbents including MEA or DEA wetted the hydrophobic porous polypropylene membrane and increased the membrane resistance against the mass transfer. Increase in pressure difference between both sides of the membranes reduced the membrane CO2 selectivity. Whether water or amine solutions were used as absorbent, mass transfer through non-porous silicone rubber was mainly controlled by membrane itself. A mathematical model based on the effective permeability of the gaseous mixtures has been used to assess the performance of both membranes, and a correlation for the shell side mass transfer has been developed.

► Membrane morphology affects the mass transfer in CO2 removal.
► Type of absorbent and gas flow rates and flow modes affect the mass transfer.
► Mathematical model based on effective permeability can be used for CO2 absorption.
► Membrane wetness can be understood by comparing the results of experiments and model.
► CO2 removal can be achieved efficiently by absorption using a microporous membrane.