Designing rotating zigzag beds: understanding dry pressure drop under varying geometries

Enhanced by centrifugal force, rotating zigzag beds (RZBs) offer great potential for process intensification in separation processes compared to conventional distillation and absorption columns. A fundamental understanding of fluid dynamics in these high-gravity (HiGee) units is still lacking, significantly hindering process design. Thus, we perform a fluid-dynamic characterization focusing on dry pressure drop and gas momentum for varying operating conditions and seven distinct zigzag geometries. A CFD method is utilized to deduce general design suggestions and a semi-physical pressure model applicable to the internals and the inner/outer cavity independently. For validation, an experimental study is conducted, showing a good agreement with both the proposed pressure model and the CFD data likewise. In a first comparison between equiareal and gradual baffle placements, no evidence of a benefit of equiareal internals is found, while equidistant approaches induce higher pressure drops. An increase in the packing height significantly reduces the pressure drop, while an elevated number of baffle pairs significantly increases it. The inner cavity is found to be a dominant contributor to the overall pressure drop at moderate and high rotational speeds because of high tangential velocities, while the outer cavity contributes insignificantly. • Design study for rotating zigzag beds with seven distinct packing geometries. • CFD and experiments show insights and relations under varing operating conditions. • Dry pressure drop model development for process models and RZB packing design. • Experimental validation shows very good agreement with model and CFD-generated data.