Because of the centrifugal field in rotating packed beds (RPB), a process intensification of gas–liquid mass transfer takes place. While two-rotor RPBs offer a great potential to increase the separation performance, compared to one-rotor RPBs, there is a lack of fundamental understanding of hydrodynamics and mass transfer in two-rotor RPBs. To bridge that gap, systematic experimental approaches are needed to derive correlations for mass transfer and hydrodynamic behavior. The current article presents a detailed analysis of dry pressure drop (Δp total) by measurements with different rotor configurations (one-rotor RPB vs two-rotor RPB) equipped with metal foam as packing and operating conditions at F-factors (F G) up to 4.9 Pa0.5 and rotational speeds (n rot) up to 1200 rpm at T = 293.15 K and p = 1 atm. Based on the Δp total of a one-rotor RPB, a correlation was proposed for Δp total of a two-rotor RPB as a function of F G and n rot. The correlation allows predicting Δp total of two-rotor RPB for F G up to 3.5 Pa0.5, using the data of the one-rotor RPB only.

Multi-rotor RPBs (MR-RPBs) are a promising way to intensify mass transfer by exploiting the centrifugal field while achieving high separation performance. Reaching the full potential of the separation performance of MR-RPBs requires a uniform liquid distribution in each rotor. As conventional liquid distributors like nozzles can only be used at the pressurized inlet of the liquid, a new concept is needed for distribution on additional rotors. For this r eason, a novel liquid distribution concept named rotating baffle distributor (RBD) was developed. It has a compact design and exploits the rotational speed n rot of the rotor. High-speed camera analyses showed that a minimum n rot of 600 r min −1 was required for axial liquid distribution with water at ambient conditions. CT scans revealed a uniform liquid distribution in the circumferential direction using RBD with 36 baffles. Furthermore, RBDs with 12, 24, and 36 baffles were applied to the distillation of ethanol−water at atmospheric pressure under total reflux using a one-rotor RPB (1R-RPB). The F-factor (F G ) was set up to 2.3 Pa 0.5 and n rot up to 1200 r min −1 . The results were compared to the same distillation experiment in the 1R-RPB using the conventional liquid distribution, i.e., spraying the liquid on the packing via a full-jet nozzle. The distillation study revealed that the RBD with 36 baffles showed one theoretical stage higher separation performance at n rot ≥ 900 r min −1 compared to the conventional liquid distribution. Those results suggest that the RBD is not only multi-rotor-compatible but also provides uniform liquid distribution while being easier to adjust and operate than the conventional nozzle setup.

Recently, various internals for rotating packed beds (RPBs) have been developed. However, the technical maturity of these internals is still relatively low compared to packings for columns. In this work, a novel design is proposed for RPBs, consisting of a seal structure combined with a Zickzack packing. The seal structure around the packing was developed to avoid bypasses in the spaces between packing and inner rotor walls, comparable to wall wipers used for structured packings in columns. This design was applied to deaeration experiments using water and nitrogen as stripping gas at rotational speeds from 450 to 1800 rpm. Using sealings, the overall liquid-side volumetric mass-transfer coefficient could be increased by up to 50% compared to the unsealed packing. Furthermore, the Zickzack packing turned out to be more resistant than conventional packings to hydrodynamic effects that lead to the formation of a peaked mass-transfer maximum at a certain rotational speed.

In Centrifugal Partition Chromatography, two immiscible liquids are used as mobile and stationary phases. During operation, bleeding of the stationary phase cannot be eliminated completely. For optimal separation performance, however, it is crucial to maintain sufficient amounts of stationary phase in the system, which is quantitatively measured by the retention value. With an online measurement of that retention value, it is possible to make predictions about the separation performance of the system. Therefore, an image processing algorithm was developed in this study, allowing quick and effortless online evaluation of retention by image analysis. Finally, the results were compared with proven analysis methods to evaluate the measurements’ validity. With the help of the new algorithm, it was possible to improve the number of pictures analyzed per time and the precision compared to the previously used technique.

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