Liquid droplets entering catalyst beds can wet surfaces, carry catalyst poisons, leave salt or hydrocarbon deposits, increase bed pressure drop, and create gas maldistribution. Upstream mist separation should therefore be matched to the specific catalyst's contamination tolerance.

Mist eliminator capacity is not one universal velocity. Re-entrainment, liquid-handling, allowable pressure drop, and outlet carryover can each become the governing limit, and fouling can shift those limits during operation.

Downstream duct deposit patterns can reveal whether mist carryover is uniform or concentrated near a specific demister edge, module, or flow path. Deposit location, elbow impact, chemistry, and module mapping can provide valuable troubleshooting evidence.

Mist carryover can interfere with CEMS and process gas analyzers by wetting probes, dissolving soluble gas species, depositing salts, plugging filters, and disturbing sample flow. Sampling temperature and downstream condensation must be checked before attributing every wet analyzer problem to the demister.

Mist eliminator DP alarms and cleaning triggers should be based on clean load-specific baselines and deterioration trends rather than one universal pressure-drop limit. Maintenance, high-DP alarm, and process-limit thresholds may serve different purposes.