Characterization of the Kenics Mixer as a Liquid-Liquid Extractive Reactor

Authors:

M. E. Tunison

Thomas W. Chapman 

This research investigates the performance of the Kenics static mixer as a continuous extractive reactor for recovering copper using the chelating agent Kelex 100. By comparing conversion data with intrinsic kinetics from single-drop experiments, the study demonstrates that the mixer's efficiency is driven by a high interfacial area that increases alongside total flow rates. The results establish that this plug-flow-like configuration offers an effective alternative to conventional equipment by exploiting rapid mixing and kinetic selectivity without forming stable emulsions.

Key Learnings

• Reactor Efficiency: The Kenics static mixer is highly effective for metal solvent extraction, achieving up to 15% conversion in residence times as short as two seconds.
• Flow Rate and Surface Area: Unlike many reactors where higher throughput reduces efficiency, the Kenics mixer shows increased conversion at higher flow rates because the higher turbulence generates a larger interfacial area (a).
• Kinetic Modeling: For complex systems like copper-Kelex 100, reactor performance is best characterized by a volumetric rate constant (ka), which combines chemical kinetics with local hydrodynamic behavior.
• Single-Drop Correlation: Data from single-drop experiments provide a reliable functional form for the reaction rate, though the actual flux in the mixer is roughly half (a factor of k ≈ 0.6) of that observed in growing drops, likely due to interfacial aging.
• Operational Advantages: The mixer behaves similarly to a plug-flow reactor and avoids the formation of stable emulsions; drops remain large enough to allow for rapid coalescence and phase separation in a settler.
• Predictive Trends: Drop size in the mixer follows the correlation D₃₂ ∝ (W e)⁻⁰.⁶, which is consistent with established models for non-coalescing dispersions in turbulent flow.