Gas-liquid transport characteristics in mechanically agitated vessel – experimental determination

The study aimed to expand the database for industrial gas-liquid contactors by measuring gas phase axial dispersion in a non-coalescent batch in a pilot-plant fermenter. This involved using several impeller types of varying sizes on a common shaft under different impeller tip speeds and gas flow rates. Key findings include: - For Lightnin A315 impellers, Peclet number (Pe) generally decreased with increasing Reynolds number (Re), indicating a shift from plug flow to mixed behavior. Smaller impellers reached the ideal gas flow faster. - Pitched blade turbines (pumping down) also showed decreasing Pe with increasing Re, with plug flow at lower Re. Smaller impellers reached ideal gas flow quicker. - For Rushton turbines, Pe generally decreased with Re, with some variations depending on impeller size and gas velocity. - Techmix impellers (pumping down) showed a general Pe reduction with increasing Re. Flow patterns were less distinct at higher Re for lower gas velocities. The study highlights the influence of impeller type and size on gas phase mixing, with smaller impellers promoting faster recirculation. Operating conditions like impeller speed and gas superficial velocity also play a crucial role in the transition between plug flow and mixed behavior. These findings contribute to a better understanding for the design and scale-up of gas-liquid contactors.