Edge gaps between a mist eliminator and vessel wall can create low-resistance gas bypass paths, causing liquid carryover even when the active separator performs correctly. Actual vessel dimensions, ovality, segmentation, support, and thermal movement should all be considered.

Vane spacing, blade angle, number of turns, hooks, pockets, and drainage geometry all influence droplet capture, pressure drop, liquid drainage, re-entrainment, and fouling tolerance. Vane packs with the same outside dimensions are not necessarily hydraulically equivalent.

Very low gas velocity can reduce droplet inertia and make fine droplets more likely to follow gas streamlines through a mist eliminator. Demister selection should therefore consider minimum, normal, and maximum gas-flow cases rather than only the maximum design velocity.

Liquid density affects droplet inertia, viscosity affects drainage and liquid holdup, and surface tension affects droplet formation, wetting, coalescence, and re-entrainment. These properties can materially change mist eliminator performance even when gas flow and droplet size remain unchanged.

Real process mist contains a distribution of droplet sizes, not one uniform diameter. Fine droplets can dominate downstream carryover even when average droplet size appears favorable, so mist eliminator selection should consider the full droplet population and how it is generated.