Study of Aeration and CO2 Absorption Using Filtration Membranes in Terms of Physical Properties and Mass Transfer Parameters

Abstract

Hollow fiber membrane contactor is nowadays one of the alternative absorption processes for the conventional bubble column. In this work, the performances of microporous hollow fiber membranes for aeration and CO2 absorption were investigated and compared with a conventional bubble column. The membranes used in this work were adapted from filtration membranes which are significantly cheaper than conventional absorption membranes. The effects of operating variables such as average pore sizes, gas flow rates, liquid flow rates, number of hollow fiber membrane, and concentrations of chemical solution on the gas-liquid absorption rate were determined. For oxygen-water absorption, the overall mass transfer coefficient (kLa), which corresponding to the absorption rate, increased with the increase of membrane porous diameter. The kLa was also enhanced with the increase of the liquid flow rate and the number of membranes while the gas flow rate was rarely influent. For carbon dioxide absorption, the increase in liquid flow rate and the carbon dioxide concentration resulted in higher mass transfer rate. Moreover, adding sodium carbonate in absorbent improved the kLa value up to 2.2 folds, comparing with physical absorption. The comparison between the membrane contractor and a bubble column indicated that the utilization of filtration membranes had more efficiency comparing to bubble column due to its high surface area and adaptability when operating with the same size especially when using lower gas velocity rate.