Three-Dimensional Model on Liquid–Liquid Mass Transfer of the Kenics Static Mixer: Considering Dynamic Droplet Size Distribution

Abstract

The Kenics static mixer is anticipated to replace conventional extraction apparatuses because of its outstanding mass transfer performances and economy. The lack of a practicable mass transfer model limits its wide application. In this study, a three-dimensional liquid−liquid mass transfer model was developed for the Kenics static mixer while considering the dynamic droplet size distribution due to both interphase mass transfer and droplet breakage and coalescence. It has been proven to have good accuracy because of the mean relative errors between simulated and experimental results within 7%. Different hydrodynamic and mass transfer behaviors were found at different fluid velocities. The patterns thus presented were supported by other publications as an additional proof of the constructed model's accuracy. It was also found from the effect analysis on fluid velocity that the static mixer, even with few mixing elements (5) and at a low total inlet fluid velocity (0.7 m/s), can achieve excellent mass transfer performance.

Numerical Investigation of Mass Transfer Prediction in Various Sizes of Kenics Static Mixers on Extraction: Corrected with Eddy Cell Model and Droplet Size Effect Model

“…Previous research found that kinetic energy declined rapidly to almost zero in the regions where the turbulence and the dispersed-phase droplet breakage occurred. , According to the analysis presented above, this region overlapped with the flow dead zone. According to Figure b, higher velocity results in a higher turbulence dissipation rate, as also reported by Cao et al It was also found that with the size magnification of the static mixer, the turbulence dissipation rate decreased, indicating the larger dispersed-phase droplet sizes in the larger device. In this phenomenon, first, in larger equipment, the organic-phase droplet is less likely to collide with the wall than the smaller one.…”

“…In the mixing and outlet sections, the velocity of the organic phase surpassed that of the aqueous phase in a lab-scale static mixer, while the inlet velocity ratio of the organic to the aqueous phase was 1:4. In our previous work, this was explained using the momentum conservation equation.…”

“…Turbulence characteristics and mean droplet diameter were incorporated into the calculation of the interphase mass transfer coefficient based on the CFD-PBE model. Additionally, in our previous work, the model-forming strategy was similar to that of Yu et al, with the consideration for the interphase mass transfer–dispersed phase droplet size effect. Kleczek et al summarized the Marangoni effect in an empirical formula group and explained that the interface solute concentration and mass transfer direction affect the droplet size of the dispersed phase. − In this work, the relative errors of the substance concentration distribution between numerical simulations and the experimental results were less than 7%, while those for the dispersed-phase droplet size were less than 5%, indicating a relatively good approximation.…”

Hydrothermal Conversion of Microalgae Slurry in a Continuous Solar Collector with Static Mixer for Heat Transfer Enhancement

“…The Nusselt numbers of tubes with static mixers are three times higher than plain tubes, while the twist ratio of the static mixer is between 3 and 10 [32]. In addition, the high-efficiency mixing induced by static mixers is beneficial to optimize the mass transfer in the continuous reactor during chemical conversion [33,34]. Chen et al proposed a tubular reactor with a static mixer [24]; the convective heat transfer coefficient (1707 W•m −2 •K −1 ) and biocrude yield (0.298 g•L −1 ) were 2.55 and 1.59 times higher than those of a plain tubular reactor [22].…”