Gas density affects the gas holdup in bubble columns. Even at atmospheric pressure, different gases produce varying gas holdups. This contribution explores the causes for variations in gas holdups occurring for different gases. Differences in the bubble size distribution resulting from varying rates of bubble breakup and coalescence as well as dissimilar bubble rise velocities are the most likely causes of differences. Correlations that include a term for gas density are able to qualitatively predict the effect of changing gas density, but no correlation can consistently predict the gas holdup for multiple systems.

The solubility of carbon dioxide in binary mixtures of water and methanol containing up to 12.37 mass % methanol has been measured at temperatures between 298 K and 333 K at atmospheric pressure. The solubility increases with increasing methanol content, but the influence is, at least at low temperatures, much smaller than linear interpolation would suggest. Employing the van't Hoff equation for ideal solutions, a correlation has been proposed that fits the measurements for up to 8.16 mass % methanol in water.

A new microstructured thin film reactor that allows for thermographic imaging of the reaction through the thin metal foil along which the liquid flows has been studied with the exothermic absorption of CO2 into aqueous solutions of NaOH. The usefulness of the new method is demonstrated on the extreme differences in temperature obtained for reaction with dry CO2 compared to reaction with prehumidified CO2. The method is able to follow the reaction in a case where complete conversion is reached before the reactor’s end, meaning that the reaction rate changes drastically from a fast beginning to zero at the end. Concentration and liquid transport coefficient profiles can be derived from the measurements obtained with this method. The information obtained indicates that this method can become a useful tool in the study of gas/liquid reactions because the measurements obtained along the length of the reactor allow for a better analysis than those obtained from an integral analysis of the reactor.

The influence of wettability on the formation of a single air bubble at a submerged orifice has been investigated using computational fluid dynamic simulations in two-dimensional and three-dimensional geometries. The detachment times of the bubbles were observed. The bubble sizes were compared to those from experiments and those predicted from force balances. The simulations were able to predict the experimental results with an average deviation of less than 10%. The wettability of the orifice was varied in the simulations by varying the static contact angle of the orifice material for an air−water system. For hydrophobic orifice materials, the bubble size increases with increasing contact angle. The reason for this is that the gas entering through the orifice spreads partially along the wall, resulting in a larger force of adhesion as well as a larger area for the formation of the bubble.

Detailed measurements and computational fluid dynamics (CFD) investigation of the hydrodynamics in a bubble column containing internal features causing flow disturbances are presented for both air and helium gases. An optical needle probe has been used to measure profiles of bubble size, bubble velocity, and gas holdup at different locations across the cross section of the column. An approach combining CFD with population balances is able to represent observed multiphase flow phenomena such as the effect of the pipes to remix and redistribute the gas as well as the tendency of the gas to channel through a slit in the pipes rather than go around the pipes. The comparison of CFD simulation to experimental measurements reveal that the overall decrease in gas holdup observed when switching from air to helium gas can be explained by swarm effects, whereas the steeper decrease in the gas holdup profile across the column is due to coalescence effects. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3764–3774, 2018