Micromixing Efficiency in the Presence of an Inert Gas in a Rotor–Stator Spinning Disk Reactor

The effects on micromixing of co-feeding an inert gas with the bulk liquid are studied for a rotor-stator spinning disk reactor by means of the Villermaux-Dushman test reaction. The results of varying rotational speeds and gas-liquid ratios are reported for three configurations: injecting the acid into the dispersed region, into the bottom thin-film region, and into the upper thin-film region. The results show that injecting in the dispersed region is the optimal configuration, as the liquid experiences the shear stress between the rotor and the stator, and with increasing rotational speed, micromixing efficiency subsequently increases. Injecting in the thin-film regions leads to poor micromixing efficiency, since the gas layer reduces the turbulence levels experienced by the liquid. For the bottom thin film, increasing rotational speed improves micromixing efficiency due to inertial rotation of the liquid film. However, in the upper thin film, micromixing is significantly worse, being affected by the dripping of liquid on the stator at the injection point. Gas holdup measurements are compared to previous studies, showing that most of the gas volume is present in the thin-film regions. These results are relevant for the design of modular chemical processes using the spinning disk technology, when fast competitive chemical reactions occur in the presence of gas and liquid.