Experimental study on single CO2 bubbles freely rising in MEA/DEEA blended solutions: Bubble behavior and mass transfer

CO2 absorption into amine solutions is an important method for reducing carbon emissions. The influence mechanism of chemical reactions on the bubble behavior and mass transfer needs to be comprehensively investigated. In this study, firstly, we measure the bubble behavior and mass transfer of single CO2 bubbles freely rising in monoethanolamine (MEA)/N,N-diethylethanolamine (DEEA) blended solutions and DEEA solutions by high-speed photography. Moreover, we investigate the effect of amine concentration on the bubble shape, aspect ratio, rising trajectory, rising velocity, and mass transfer coefficient. The results show that CO2 bubbles in MEA/ DEEA blended solutions experience significant shape deformation, oscillation damping, surface contamination, and mass transfer deterioration. In contrast, CO2 bubbles in DEEA solutions behave similarly to those in ultrapure water, i.e. negligible surface contamination and mass transfer enhancement. Furthermore, we consider the differences in the bubble behavior and mass transfer from the viewpoint of the chemical reaction kinetics and bubble surface contamination degree. The location where a chemical reaction occurs is close to the bubble surface with a fast reaction, and as a result, the bubble surface is likely to be contaminated. Finally, this study provides insights into the intensification of amine -based CO2 chemical absorption processes.