Two-dimensional computational fluid dynamics (CFD) simulations of internal airlift reactors were considered to predict hydrodynamic and mass transfer in unsteady state flow. The main aim of this work is to provide insight into the effect of a draft tube on the air– water reactor mass transfer and hydrodynamics. A complex mathematical model was used to investigate the coalescence and breakup towards a more precise simulation of airlift reactors. The effect of the draft tube was considered in terms of coalescence and breakup to evaluate the reactor performance. The simulation results reveal that the presence of a draft tube in an airlift reactor results in a significant enhancement of the gas–liquid mass transfer rate, and a reduction in average liquid velocity and gas holdup. The coalescence and break-up affected the results significantly. The CFD predictions also confirmed that there was reasonable conformity between the predicted model values and the experimental data.
