Wet Electrostatic Precipitators (WESP)
The polishing technology for everything dry collection can’t catch: sub-µm aerosols, acid mist, SO3, condensable tars and pyrolysis fume. A high-voltage corona charges the contaminant; water-washed collection plates carry it down. Continuous wetting prevents the re-entrainment that fouls dry ESPs.
Outlet PM < 10 mg/Nm3 achievable. Stainless modular fabrication. Pairs with quench tower or packed-bed pre-conditioning.
Typical duties:
- Acid plant tail-gas polishing — SO3 / H2SO4 mist
- Roaster and calciner offgas
- Pyrolysis and biochar fume — e.g. Pyrocal (Queensland) two WESP units on sticky tars
- Sticky and condensable particulate — e.g. CSR Ingleburn WESP upgrade (NSW), 6 stainless modules to NSW EPA Licence 13087
- Blue-plume mitigation
Dry Electrostatic Precipitators
The Vortex Engineering Group operates the largest dry ESP range in New Zealand. Dry ESPs use high-voltage corona discharge and grounded collector plates to remove particulate from dry gas streams — no liquor recirculation, simple downstream handling, well-suited to high-flow / moderate-load duties.
Typical duties:
- Iron / steel sintering and pelletising
- Cement and lime kiln offgas
- Furnace dust capture
- Glass furnace offgas — e.g. O-I Glass / Visy Glass (Auckland)
- Iron-process ESP — e.g. PT Krakatau / PT Meratus Jaya (Indonesia)
Modules with rapping systems, hoppers, gas-distribution baffles and TR sets matched to the duty. Materials selected for gas chemistry — carbon steel, stainless, or alloyed shell.
Engineering envelope
Both wet and dry ESPs delivered under a unified engineering envelope:
- Particulate size — 0.01 µm and up
- Outlet PM — < 10 mg/Nm3 achievable (WESP duty)
- Gas inlet (WESP) — cooled / saturated, 60–80 °C typical
- Configurations — plate, tubular, multi-module
- Materials — 304 / 316 SS, alloy options, carbon steel for dry duty
- Power — HV TR sets, arc-quench logic, PLC control
- Pairs with — quench tower, packed-bed scrubber, venturi pre-scrubber
ISO 9001 / 14001 / 45001 aligned. AS/NZS 5131 structural, AS/NZS 1554.6 welding, ASME IX / VIII where required. Process guarantees written project-by-project against measured inlet conditions and target outlet limits.
Where we've delivered ESPs
Wet and dry electrostatic precipitator installations across mining, building materials, biomass and acid-plant duties. Hover over any location to see the project.
Frequently asked questions
Dry ESP vs wet ESP — what is the difference?
A dry ESP collects dry particulate from hot, high-flow gas; a wet ESP (WESP) handles sub-micron aerosols, acid mist, SO3 and oily/condensable fume using continuous irrigation.
When do I need a WESP?
For sub-micron aerosol, acid mist, SO3 or oily/condensable fume — where dry collection or inertial scrubbing cannot meet the limit. A WESP reaches outlet PM below 10 mg/Nm3.
ESP vs baghouse vs wet scrubber?
ESPs suit high-flow particulate including high temperatures; baghouses suit dry filterable dust; wet scrubbers suit soluble gases and condensable or sticky duties. The right pick depends on particle size, temperature and gas chemistry.
What dust properties decide whether a dry ESP will work?
Electrical resistivity governs it. An ESP has to charge the dust, hold it on the plate, then release it when rapped, so resistivity roughly in the 10^8 to 10^11 ohm-cm band is where dry precipitation works well. Below that band the dust loses charge on contact and re-entrains; above it, charge builds in the collected layer until it breaks down electrically. Resistivity is a property of your dust at your gas temperature and moisture, so it is measured rather than assumed.
What is back-corona?
Reverse ionisation from a highly resistive collected dust layer. Charge cannot bleed away through the layer, so it breaks down electrically and fires back into the gas, which forces the controller to reduce voltage and can hold an ESP well short of its design efficiency. The routes around it are shifting resistivity (temperature, moisture or SO3 conditioning), high-frequency power supplies that hold a more stable corona, or a WESP, where an irrigated conductive surface removes the mechanism entirely.
Can an ESP handle high gas temperatures?
Yes, and that is one of the main reasons to choose one. Dry ESPs handle high-temperature, high-flow gas such as kiln, furnace, smelter and boiler exhaust at low pressure drop, in duties where fabric filter media would need protecting or cooling.
Why has our existing ESP lost performance?
Usually one of five things, all diagnosable before anyone quotes a replacement: broken or misaligned electrodes limiting the achievable voltage; rapping that is too gentle (insulating layer) or too aggressive (re-entrainment); ageing transformer-rectifier sets, failed bus sections or conservatively tuned controls; hopper heating or insulation failure causing bridging, or air in-leakage at the discharge; and corroded or blocked gas distribution plates letting gas short-circuit through part of the casing.
Can an existing ESP be upgraded instead of replaced?
Often yes, and for much less cost. High-frequency power supplies, electrode renewal, gas distribution correction and control retuning on a sound existing casing recover a large part of the original performance. We assess the casing and internals first, then quote the upgrade against a measured baseline.
Does a WESP need water treatment?
Yes, and it belongs in the scope from the start. Captured solids and acid leave as a slurry, so recirculation rate, blowdown, pH control, solids removal and the downstream treatment load all form part of the design. On acid-mist duties the blowdown chemistry often drives operating cost more than fan power does.
What materials are used in a WESP?
Selection follows the halides as much as the pH, running from FRP and conductive polymer through 316L to higher alloys such as 904L, alloy 20 and Hastelloy. Chloride and fluoride content, temperature and acid strength are what rule out the cheaper austenitic stainless steels; a low pH on its own does not decide it.
Can a WESP be installed after a wet scrubber?
Yes, and it is a common arrangement. The scrubber removes soluble gas and the bulk particulate, and the WESP polishes the remaining sub-micron aerosol and mist. The gas arriving at the WESP is already saturated, which is exactly the condition continuous irrigation suits.
Do you support legacy ESPs?
Yes — we supply spares and servicing for JOY-Western, TAPC, Lurgi, Flakt and Lodge Cottrell electrostatic precipitators.
Do you guarantee outlet emissions?
Yes — against your measured inlet conditions and target outlet limits.