abstract
Ionic liquids (ILs) have been widely considered as potential green solvents for CO2 capture, and many
promising ionic liquids have been synthesized and reported. However, knowledge related to the hydrodynamics
of CO2 absorption with ionic liquids especially the bubble behavior is still scarce compared
with the conventional molecular solvents. In this study, it is the first time to discuss the multi-bubble
behavior in a carbon capture system with ionic liquid by using a high speed image pick-up system.
The bubble behavior, such as bubble size distribution, total gas holdup, Sauter diameter and interfacial
area at different operating conditions are investigated. The experimental results show that the bubble
diameter of CO2–[bmim][BF4] system is smaller than that of N2–[bmim][BF4] system. The bubble diameter
increases as the gas superficial velocity increases and the height along the axis of the column rises,
but decreases with the increase of the temperature. The total gas holdup in [bmim][BF4] increases with
the increase of the system temperature due to the decrease of the ionic liquid viscosity. In addition, the
gas superficial velocity improves the total gas holdup due to the higher gas momentum favors the formation
of small bubbles. A new correlation based on the experimental data is proposed for the prediction of
Sauter diameter in gas–ionic liquid systems. The prediction results calculated by the new correlation are
in good agreement with the experimental data with a relative error less than 6%