Macro-Mixing Optimization in a High-Aspect-Ratio Liquid–Liquid Stirred Tank under Transitional Flow: Impeller Configuration and Energy Efficiency

In complex multiphase processes (e.g., hydroformylation), high-aspect-ratio reactors frequently suffer from axial transport bottlenecks. Since conventional power intensification merely exacerbates local dissipation, quantitatively guiding geometric reconfigurations in these opaque, transitional dispersions remains critical. To address this, the present work extracted macro-mixing kinetics and axial phase distribution profiles to establish an empirical baseline. Guided by these data, a hybrid configuration─dual marine propellers (MP) above a modified Rushton turbine (MRT)─was implemented to functionally decouple macroscopic axial transport and localized phase dispersion. This mitigates hydrodynamic compartmentalization and re-establishes bulk circulation. To rigorously evaluate this, a hydrodynamic synergy factor (ξ) was formulated to explicitly decouple efficiency gains of flow reconfiguration from specific power input. Demonstrating a 30% efficiency gain (peak ξ = 1.30) at equivalent power, this work translates physical mitigation into a quantitative, empirical approach, providing robust support for the evaluation of complex multiphase reactors.