Hydrodynamics of Newtonian and non-Newtonian liquids in internal-loop airlift reactors

Airlift reactors have numerous applications in processing industries, and thus the hydrodynamic behaviors using fluids that have distinct rheological characteristics need to be better understood for the successful design and operation of these devices. In this sense, the novelty of this study is to evaluate the influence of the energy losses in each reactor region on the interstitial liquid velocity (VLR), and to provide correlations for prediction of gas hold-ups (εR and εD) and VLR for a wide range of physical and rheological properties of the liquid, using different models (draft-tube-DTA, split-cylinder-SCA) and scales (5 and 10 L) of airlift reactors. Gas hold-ups were determined by a manometric method, and VLR was calculated by circulation time of spheres with the same liquid density. Energy losses were calculated using a semi-theoretical method. The total energy dissipated in the riser and downcomer was greater for DTA reactors, whereas in the bottom was greater for SCA reactors. Non-Newtonian fluids showed higher VLR in SCA reactors, while the opposite was observed for Newtonian fluids. Excellent fits to the experimental data were achieved using simple correlations to predict εR and εD, as well as dimensionless correlations that incorporated the desired parameter (VLR).