Many chemical reactions
contain heterogeneous reagents, products,
byproducts, or catalysts, making their transposition from batch to
continuous-flow processing challenging. Herein, we report the use
of a photochemical rotor–stator spinning disk reactor (pRS-SDR)
that can handle and scale solid-containing photochemical reaction
conditions in flow. Its ability to handle slurries was showcased for
the TiO
2
-mediated aerobic photodegradation of aqueous methylene
blue. The use of a fast rotating disk imposes high shear forces on
the multiphase reaction mixture, ensuring its homogenization, increasing
the mass transfer, and improving the irradiation profile of the reaction
mixture. The pRS-SDR performance was also compared to other lab-scale
reactors in terms of water treated per reactor volume and light power
input.
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.
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