Augmenting CO₂ Absorption Flux through a Gas-Liquid Membrane Module by Inserting Carbon-Fiber Spacers

We investigated the insertion of eddy promoters into a parallel-plate gas-liquid polytetrafluoroethylene (PTFE) membrane contactor to effectively enhance carbon dioxide absorption through aqueous amine solutions (monoethanolamide-MEA). In this study, a theoretical model was established and experimental work was performed to predict and to compare carbon dioxide absorption efficiency under concurrent- and countercurrent-flow operations for various MEA feed flow rates, inlet CO₂ concentrations, and channel design conditions. A Sherwood number's correlated expression was formulated, incorporating experimental data to estimate the mass transfer coefficient of the CO₂ absorption in MEA flowing through a PTFE membrane. Theoretical predictions were calculated and validated through experimental data for the augmented CO₂ absorption efficiency by inserting carbon-fiber spacers as an eddy promoter to reduce the concentration polarization effect. The study determined that a higher MEA feed rate, a lower feed CO₂ concentration, and wider carbon-fiber spacers resulted in a higher CO₂ absorption rate for concurrent- and countercurrent-flow operations. A maximum of 80% CO₂ absorption efficiency enhancement was found in the device by inserting carbon-fiber spacers, as compared to that in the empty channel device. The overall CO₂ absorption rate was higher for countercurrent operation than that for concurrent operation. We evaluated the effectiveness of power utilization in augmenting the CO₂ absorption rate by inserting carbon-fiber spacers in the MEA feed channel and concluded that the higher the flow rate, the lower the power utilization's effectiveness. Therefore, to increase the CO₂ absorption flux, widening carbon-fiber spacers was determined to be more effective than increasing the MEA feed flow rate.