Computational fluid dynamics study of the optimal design and operating conditions of the segmentation ring used in parallel segmented flow columns

•We studied parallel segmented flow using computational fluid dynamics.•Parallel segmented flow can alleviate transcolumn velocity gradient band broadening.•Part of the efficiency gain is however lost to the segmentation ring itself.•A 0.31 mm ring disturbs band shape significantly less than a 0.62 mm ring.•Each ring thickness has its own optimal flow rate distribution.

We report on a numerical study wherein we modeled the influence of the segmentation ring used in the recently introduced parallel segmented flow concept. The study reconfirms that the parallel segmented flow concept can indeed improve separation performance of radially heterogeneous beds. It was however also found that the segmentation ring in itself introduces significant flow disturbances. Depending on its thickness and the fraction of the total flow rate going through the central opening, the ring itself can constitute a loss in volumetric variance (σv2) in the order of a few up to a few tens of μl2. Although the ideal flow-split ring would be infinitely thin, it was found that halving the current 0.62 mm ring thickness used in literature to 0.31 mm would already eliminate most of its negative effect. At the inlet, the optimal central flow rate fraction for a 0.62 mm as well as a 0.31 mm wide ring in a 4.6 mm I.D. column lies in the range of 0.25–0.4. At the outlet, the optimal range is 0.15–0.4.