The Effect of Sweeping Media and Temperature on Aqueous CO2 Removal Using Hollow Fiber Membrane Contactor (HFMC): An Experimental Determination

Abstract

Transport phenomena through hollow fiber membrane contactors (HFMCs) indicate the exchange of a component between the two phases, inside and outside of hollow fibers. In this research, we designed and fabricated lab-made HFMCs to assess the difference between water and air as sweeping media for CO2 exchange. The effects of flow rates and temperature ratios on aqueous CO2 absorption were investigated accordingly. A semiclosed circuit incorporating our fabricated HFMCs was set up to regulate the operating parameters and evaluate the aqueous CO2 concentration using an initiative pH-based method. The results of our experiments remarkably reveal that air tends to remove aqueous CO2 more than water when aqueous CO2 concentration is higher than 3.53 × 10−6 mlCO2/l. However, water would surpass air in lower concentrations. Nevertheless, tripling the flow rate of sweeping media from 500 to 1500 ml/min shifts up this cutoff point 50 times to around 1.66 × 10−4 mlCO2/l. The experiments performed at three different temperature ratios of 22 : 22, 44 : 12, and 22 : 12°C (CO2-rich liquid: sweeping medium) demonstrated that a higher temperature gradient deteriorates the CO2 absorption capacity of sweeping media. Nonetheless, temperature gradient becomes highly effective in aqueous CO2 concentrations lower than 1.57 × 10−6 CO2/l. The results of this research could be applied in performance optimization of aqueous CO2 absorbing HFMCs, even in sophisticated medical procedures such as arterio-venous and veno-venous CO2 removal systems where both water and air could be used as blood’s CO2 sweeping media.