In the present work, a CFD simulation, using two-fluid model, has been performed to obtain the flow pattern and the gas hold-up in external loop air-lift reactors (EL-ALR). An agreement was observed between the predicted and the experimental data available in the published literature. The validated CFD model has been extended for the simulation of mixing and the axial dispersion coefficient. CFD predictions of mixing time are well in agreement with the experimental values published in literature, and the results of axial dispersion coefficient also show good agreement with the experimental values published in literature except in the case of Vial et al. (2005), where the CFD model underpredicts. A systematic numerical study was undertaken to understand the relative contribution of convection and eddy diffusion to the mixing and axial dispersion.