Numerical simulations of an internal‐loop airlift reactor containing surfactants with a CFD‐PBM coupled model

Abstract The effect of surfactants on gas‐liquid systems in an internal‐loop airlift reactor was investigated using a CFD‐PBM coupled model. This model integrates three mechanisms: the inhibition of bubble coalescence, the increase in drag force, both induced by the Marangoni effect, and the enhancement of bubble breakup due to decreased surface tension. This comprehensive approach established a multiscale simulation framework for gas‐liquid systems containing surfactants. Using an ethanol‐water system as an example ( x ethanol = 0–0.05, corresponding to 0–14 vol%), the simulation results for gas holdup are in good agreement with experimental data from our previous work, showing a rapid increase followed by a gradual decrease in gas holdup as ethanol concentration increases. Further numerical simulations were performed to evaluate the relative contributions of the three surfactant‐induced mechanisms to gas holdup. The results revealed that the inhibition of bubble coalescence is the dominant mechanism by which surfactants affect the hydrodynamics.