CFD Investigation of Enhanced Gas Dispersion in Coaxial Mixers Using Integrated Gas-Inducing Impellers for Multiphase Applications
Coaxial mixers, consisting of independently driven central and anchor impellers, have emerged as an advanced and adaptable technology for managing gas-liquid-solid systems. Their ability to control shear zones and flow regimes makes them well-suited for processing non-Newtonian fluids and high-solids suspensions. However, in conventional configurations, gas spargers located below the impellers can interfere with the hydrodynamics, particularly in downward pumping modes, by disrupting the natural flow paths and reducing gas dispersion efficiency. To overcome this challenge, the integration of gas-inducing impellers into coaxial mixer systems offers a compelling alternative that eliminates the need for external sparging devices. In this configuration, a pilot-scale coaxial mixing vessel with aspect ratio of 1 and diameter of 0.4 m, the gas-inducing impeller draws gas directly from the headspace into the liquid phase, while the secondary impeller promotes bulk fluid circulation and effective solid suspension. This separation of gas induction and fluid mixing functions enhances key hydrodynamic parameters, including gas hold-up, bubble residence time, and interfacial area, which are critical for improving mass transfer performance. Additionally, the system exhibits robust operation under high-viscosity and high-solid-loading conditions, extending its industrial applicability. These advantages position gas-inducing coaxial mixers as a highly efficient, flexible, and scalable solution for intensified gas-liquid-solid operations in chemical, biochemical, and metallurgical processing industries .