Detailed experimental study on the dissolution of CO2 and air bubbles rising in water

- Bubble dissolution dynamics is studied experimentally with a high-speed camera.
- Clear contrast between dissolving CO2 bubbles and non-dissolving air bubbles.
- Bubbles reduce mass and size, thus the amplitude of wobbling oscillation is drastically decreased.
- Comparison with boundary layer dissolution models shows minor deviations.

An experimental investigation of single bubbles rising in water in a confined cylindrical geometry is performed as means of obtaining further understanding on the CO2 dissolution and chemical conversion in multi-phase bubble towers. Single isolated bubbles (D~ 4,5- 5,5 mm) and individual bubble tracking in small bubble swarms at low gas volume fraction is evaluated using a high-speed camera. Comparison with dissolution rate of air and CO2 bubbles reveals hardly a diameter change for air bubbles, in contrast with near-total dissolution of CO2 bubbles within the 2 m column height. Comparison with 1D numerical analysis on single rising bubbles and previous 3D CFD simulations of small bubble swarms show a fair agreement although certain deviations are encountered. Only CO2 bubbles decrease their aspect ratio from wobbling ellipsoidal bubbles to spherical bubbles depending on their vertical location in the tower, i.e. their size. The amplitude of oscillation is decreased while bubbles dissolve.