Marangoni Effect on Hydrodynamics and Mass Transfer Behavior in an Internal Loop Airlift Reactor under Elevated Pressure

The Marangoni effect on the hydrodynamics and mass transfer was studied in an internal loop airlift reactor with the addition of ethanol under elevated pressure. The overall gas holdup alpha(g) increased by similar to 10% and the gas-liquid volumetric mass-transfer coefficient k(l)a increased by similar to 0% on average for each one bar increase in pressure. When the mole fraction of ethanol x(E) increased from 0 to 0.012, alpha(g) increased by similar to 110% and k(l)a increased by similar to 50%. However, when x(E) increased from 0.012 to 0.11, alpha(g) decreased by similar to 40% and kla decreased by similar to 25%. This volcano-shaped relationship between both hydrodynamics and mass transfer behavior and ethanol concentration was determined by the Marangoni effect. Semi-empirical correlations of alpha(g) and k(l)a were proposed by including the Marangoni effect in a wide range of ethanol concentration and operating conditions. These correlations gave good predictions of alpha(g) and k(l)a compared with extensive experimental data in the literature.