Wet Scrubber Mist Eliminator Selection and Washing Checks

Wet scrubber mist eliminators must balance removal efficiency, pressure drop, washability and corrosion resistance. A design that performs well on clean water mist may fail quickly in slurry or sticky service.

Define what the scrubber creates

The separator may receive coarse droplets from spray nozzles, finer droplets generated by high-energy contact, foam, suspended solids or condensed aerosol. Record the scrubber type and the location of the mist eliminator relative to sprays, packing, trays or venturi throat. “Wet scrubber” alone does not establish the droplet distribution or liquid loading.

Also define what happens if carryover passes downstream: stack deposits, fan erosion, duct corrosion, product contamination or an emission limit. This determines whether the project needs a construction replacement, an engineering performance review or specialist aerosol equipment.

Common choices

PP vane packs are widely considered in wet scrubber and comparable flue gas desulfurization (FGD) duties because they are compatible with some corrosive wet environments and can tolerate fouling better than dense mesh. Stainless mesh may still be suitable for cleaner, hotter or mechanically demanding service.

PTFE or special alloys can be considered for aggressive chemistry, but cost and support design should be reviewed separately.

Mesh is generally a stronger starting point for relatively fine, clean entrainment where drainage remains stable. Open vanes are generally a stronger starting point for high liquid load, solids and duties that require washing. A combined mesh and vane arrangement can cover two functions, but it adds pressure drop and another fouling surface. None of these labels defines performance without geometry and duty.

For polymer internals, freeze the raw material producer, named commercial grade, continuous and upset temperature, mechanical loading and chemical environment. Thermal expansion, creep, support spacing and fastening can govern fit even where the polymer is chemically compatible.

Washing matters

A mist eliminator with no effective wash system may plug even if the media is correct. Review spray nozzle coverage, wash water quality, washing frequency, drainage path and access for inspection.

Pressure drop trend is useful evidence. A gradual increase points towards fouling; a sudden change points towards flooding, liquid slugs or mechanical displacement. The trend alone does not establish a single cause.

Build a wash review around the whole path:

• source-water or liquor quality and its scaling potential;
• available pressure and flow at the operating nozzles;
• nozzle pattern, orientation, overlap and shadowed areas;
• top, bottom or alternating sequence;
• wash duration and trigger;
• route by which removed solids and liquid leave the media.

Changing frequency without verifying coverage can waste water while leaving the first deposit zone untouched. A site trial should track pressure drop, nozzle condition and deposit pattern rather than only recording total wash flow.

Troubleshoot by pattern

Edge deposits can be associated with wall bypass or poor wash coverage. A uniformly loaded upstream face can indicate high solids or insufficient cleaning. Clean channels can indicate local high velocity, missing media or direct inlet flow. Broken plastic blades suggest a different review from a gradual scale layer. Treat these as hypotheses and compare them with operating data and deposit analysis.

RFQ details

Send gas flow, temperature, liquid chemistry, solids content, mist load, pressure drop allowance, wash method, vessel or duct dimensions, access limits and existing part photos.

Add minimum and maximum gas cases, pressure and gas density, scrubber and nozzle type, droplet or carryover basis, slurry concentration and particle character, foaming or sticky contaminants, clean and current pressure-drop trend, material temperature excursions, support geometry and downstream acceptance requirement. Mark estimates openly.

What to freeze in the purchase

Identify flow direction, media family and offered geometry, material grade, overall and section dimensions, blade or mesh orientation, support and hold-down interface, wall seals, wash interfaces, marking and packing. The quoted QA package should be limited to the measurements, photos, packing list and material or batch evidence stated in the PI; additional testing or third-party inspection is optional and separately quoted.

For a build-to-drawing replacement, avoid implying efficiency or pressure-drop guarantees. A performance route must separately freeze inlet droplets and liquid loading, operating envelope, clean or fouled condition, wash assumptions and acceptance method.

Use the mesh-versus-vane guide for the first device decision and the FGD guide where limestone, lime, gypsum or ash dominates.

Engineering sources and transfer limits

Koch-Glitsch’s Severe Services explains why open, smooth vane paths and irrigation are used when solids, sticky droplets or plugging threaten mesh. The U.S. EPA’s FGD inspection manual provides operating evidence on pressure drop, deposits and mist-eliminator washing. These sources support the diagnostic method; proprietary performance and old plant wash settings do not transfer automatically to a new scrubber.