15This review paper describes the state-of-the-art in the field of HiGee contactors used for gas-16 liquid mass transfer processes, with a special focus on distillation, and for heterogeneously 17 catalyzed reactions. 18Several types of rotating beds are discussed, including single-block rotating packed-bed, split-19 packing rotating bed, rotating zigzag bed, two-stage counter-current rotating packed bed, 20 blade packing rotating packed bed, rotating bed with blade packing and baffles, counter-flow 21 concentric-ring rotating bed and crossflow concentric-baffle rotating bed. 22The working principles of HiGee technology, as well as the modeling, design and control 23 aspects, and practical applications are explained and discussed. In addition, this paper 24 addresses the advantages and disadvantages with respect to mass-transfer performance, 25 pressure drop, rotor complexity and suitability to perform continuous distillation and to be 26

The Danckwerts' plot method is a commonly used graphical technique to independently determine the interfacial area and mass-transfer coefficient in gas-liquid contactors. The method was derived in 1963 when computational capabilities were limited and intensified process equipment did not exist. A numerical analysis of the underlying assumptions of the method in this paper has shown a bias in the technique, especially for situations where mass-transfer rates are intensified, or where there is limited liquid holdup in the bulk compared to the film layers. In fact, systematic errors of up to 50% in the interfacial area, and as high as 90% in the mass-transfer coefficients, can be expected for modern, intensified gas-liquid contactors, even within the commonly accepted validity limits of a pseudo-first-order reaction and Hatta numbers in the range of 0.3 < Ha < 3. Given the current computational capabilities and the intensified mass-transfer rates in modern gas-liquid contactors, it is therefore imperative that the equations for reaction and diffusion in the liquid films are numerically solved and subsequently used to fit the interfacial area and mass-transfer coefficient to experimental data, which would traditionally be used in the graphical Danckwerts' method.