Mist eliminator wash systems can prevent fouling, but excessive or poorly distributed wash liquid can cause flooding, high pressure drop, and re-entrainment. Wash rate, nozzle coverage, gas load, drainage capacity, and cleaning strategy should be designed together.

Fouling patterns on a mist eliminator can reveal gas maldistribution, liquid channeling, direct spray impingement, wall flow, drainage obstruction, and upstream packed-bed problems. Photographing and mapping deposits before cleaning can provide valuable process-diagnostic information.

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.