Liquid–Liquid\nHeterogeneous Mixing Characteristics\nin a Submerged Rotating Packed Bed

The involvement of liquid–liquid heterogeneous\nintensification\nin chemical processes is indispensable due to the presence of phase\ninterfaces that impose limitations on mixing efficiency. Herein, a\nsubmerged rotating packed bed (SRPB) was developed to intensify liquid–liquid\nheterogeneous mixing under a dramatic centrifugal environment. The\npacking was submerged in continuous liquid to potentially match the\nheat-sensitive reaction systems. The liquid–liquid heterogeneous\ndispersion phenomena were photographed using a microscope, and the\nheterogeneous mixing efficiency was investigated using a sodium hydroxide\nand aspirin system as the chemical probe. As rotational speed was\nincreased from 300 to 1500 r/min, the Sauter mean diameter of the\naqueous phase was remarkably reduced from 110.65 to 19.57 μm,\nproving that SRPB could effectively disperse the liquid–liquid\nheterogeneous reaction system. Benefiting from the rotating packing,\nthe segregation index (<i>X</i><sub>S</sub>) and micromixing\ntime (<i>t</i><sub>m</sub>) respectively decreased in the\nrange of 0.33–0.11 and 3.98–1.36 ms, indicating that\nthe mixing efficiency was significantly enhanced under the centrifugal\nfield of SRPB. The increase in the total volume flow rate reduced <i>X</i><sub>S</sub> and <i>t</i><sub>m</sub>, which\ncould stem from the enlarged heterogeneous interfaces by forming multiple\ncomposite droplets at large volume flow rates. Compared with conventional\nRPB, the <i>X</i><sub>S</sub> of SRPB (0.09–0.35)\nwas slightly lower than that of RPB (0.1–0.4), and the <i>t</i><sub>m</sub> of SRPB (1.36–3.98) was remarkably\nlower than that of RPB (1–10), proving the superiority of SPRB\nin promoting heterogeneous mixing.