Influence of configuration on the performance of external loop airlift contactors

Various types of external loop airlift contactors (ELALCs) were examined for their hydrodynamic and mass transfer behavior. The investigation covered a variety of design parameters including the length of connection tubes (Lc), height of riser and downcomer (Lh), and the airlift configurations while maintaining the ratio between downcomer and riser cross sectional area constant at 0.269. The results demonstrated that the behavior of the external loop airlift could be modified by adjusting the design and operating variables. In general, a faster liquid velocity led to a presence of lower gas holdup and gas–liquid mass transfer rate. Increasing Lc and Lh seemed to increase liquid velocity while decreasing the overall gas holdup and the overall volumetric mass transfer coefficient. Empirical correlations for the estimation of the system behavior were finally formulated.

Research highlights
► Hydrodynamic and mass transfer behavior of external loop airlifts were examined.
► Significant design parameters were connection tube length and liquid height.
► Configuration of the connection conduits could affect the system performance.
► Estimates of system behaviors were provided as empirical correlations.