Other Types of Scrubbers:

Wet Scrubber

What is a wet scrubber?

Wet Scrubbers are a type of air pollution control equipment that may be used to remove airborne particulates and/or gases from industrial exhaust streams.

Also known as water scrubber, a wet scrubber sprays a liquid (often water) into an exhaust gas or off-gas stream to capture contaminants and neutralize pollutants.

Scrubbers are typically in the form of a cylindrical tower, where the liquid is sprayed into the top of the tower and runs downward, while exhaust enters at the bottom and moves upwards through the liquid. The tower may contain a packing material to facilitate air-to-liquid mixing.

Wet Scrubbers can be used to capture both particulates and gases in a single stream, but they are typically not effective for capturing VOCs, odors, and other organic non-polar gases. Wet scrubbers can be used to capture gases that are soluble in water, such as alcohols and other polar molecules.

Wet Scrubber effectiveness on:

Particulate matter95
Inorganic fumes, vapors, gases, and odors95
Water-soluble toxic gases95
Heavy Metals90
Hazardous Air Pollutants (HAPs)40
Volatile Organic Compounds (VOCs)20
Odors* (Organic-based)20

*A wet scrubber is effective at removing inorganic odor compounds, such as hydrogen sulfide (H2S) and ammonia (NH3).

Components of a Wet Scrubber

Ductwork and fan/blower

Scrubbers may use a forced draft or induced draft fan system, depending on the exhaust air conditions: temperature, corrosiveness, amount of particulate.

Scrubbing tower

Depending on the corrosiveness of the contaminants, a variety of materials for the scrubbing vessel may be used: stainless steel, polypropylene, fiberglass, PVC, fiber-reinforced plastic, and more.

Mist Eliminators and Stack

After scrubbing, the exhaust air is typically near 100% relative humidity. Most states require mist eliminators to remove excess water particles before exhausting out the stack, to reduce the visible plume.

Liquid Circulation and Spray

The system includes pumps to circulate the scrubbing liquid. Sometimes the spent liquid can be treated and/or filtered and then recycled.

A simple water scrubber made from stainless steel.

A water scrubber with quench spray to cool incoming air stream.
Used for hot gases above ~220°F

Wet Scrubber Design Considerations


The volume of process air to be treated is a key consideration. Scrubbers systems can be designed to handle any amount from 100 CFM to over 100,000 CFM.

Destruction or Removal Efficiency (DRE)

Factors that impact DRE:

  1. Type of contaminants
    • Solubility
    • Reactivity
  2. Concentration of contaminants
  3. Residence time
  4. Liquid-to-gas ratio
  5. Flow rates
  6. Gas temperature

Materials of Construction

Material options include:

  1. Stainless steel
  2. Fiberglass
  3. Fiber-reinforced plastic (FRP)
  4. Polypropylene
  5. PVC
  6. Non-reactive liners like Teflon available

Equipment Configuration & Layout

Key questions include:

  1. Are multiple control devices needed?
    • Due to high air volume -> 2 scrubbers in parallel
    • Due to multiple contaminants -> equipment in series
      • Two scrubbers with different liquids
      • Scrubber + thermal oxidizer combo
  2. Fan location: induced draft or forced draft?
  3. Recirculation, treatment, and pump skids
  4. Inlet ductwork
  5. Outlet ductwork and exhaust stack
  6. Test ports & access platforms

Industries, Applications, & Case Studies

Petroleum Refinery
  • Petrochemical refining and oil & gas processing generates emissions contaminated with petrochemical fumes and vapors, oil mists, or other petro-based aerosols. Wet scrubbers may be used to absorb or dissolve the harmful chemical vapors and liquid droplets before releasing to atmosphere.

Chemical Production
  • Manufacturing chemicals generates exhaust streams contaminated with toxic chemicals and gases. Wet scrubbers are often used to remove chemical vapors before releasing to atmosphere. Often an acid or basic scrubbing liquid is used to neutralize any reactive contaminants.

Acid Manufacturing
  • Wet scrubbers are effective for treating and removing acid fumes and vapors. A basic (alkaline) solution is injected into the scrubber and mixes with the exhaust vapor. A chemical reaction occurs, combining the acidic vapors and scrubbing liquid to produce harmless salts and water.

Cookers and Ovens
  • In the food-processing industry, a venturi water scrubber may be used to capture the microscopic grease mist, particulates, and smoke that forms during meat cooking. It will also work to capture the flour dust from baking and many other food-processing applications. In these cases, a wet scrubber is more effective than mechanical air filters.

Animal Feed
  • Manufacturing of animal feed creates dust and airborne particulates during the pelleting and drying of the animal feed. A wet scrubber can be used to filter the dust and particulate from the exhaust before releasing to atmosphere. Removal efficiencies of 99% can be achieved.

Paint Booth Overspray
  • Water scrubbers are used to capture paint overspray in high-volume paint booths. In the Automotive industry, the wet scrubber is often built into the paint booth itself. Toyota uses a combination wet scrubber with cyclone mist tower to improve capture efficiencies. Others use a Dynatube, Circula, or Venturi-type wet scrubber.

Metal Grinding
  • Metal finishing often includes grinding and drilling. A wet scrubber can be used to filter the metal shavings, small pieces, and metal dust from the air prior to exhaust from a stack. The scrubbing liquid can be filtered with a magnetic filter and recirculated for re-use in the scrubber. A dust collector and/or filterbox may also be used.

  • In the semiconductor industry, wet scrubbers are used to capture various Hazardous Air Pollutants (HAPs) and ozone-depleting GHGs, including Silane-, Tetrachloride-, and Siloxane-based contaminants. These compounds will hydrolyze and decompose once in contact with water. Any solid reaction products will end up in the scrubbing liquid and need to be filtered out.

The Best Wet Scrubber Manufacturers

CECO Environmental

CECO offers their HEE-Duall brand of wet scrubbers to treat chemical fumes, NOx, Odors, high-temp gases, particulates, and more. CECO builds scrubbers for the building products, manufacturing, oil & gas, chemical, and semiconductor industries.

CECO differentiators:

  • High quality materials
  • Expertly engineered
  • Many technology options
  • Higher cost

Gulf Coast Environmental

Gulf Coast Environmental Systems (GCES) offers both venturi and packed bed wet scrubbers for Ammonia, Chlorine, HCl Acid, Chlorinated Silanes, Sulfur Dioxide, Hydrogen Sulfide, Boron Trifluoride, and Amines. GCES supplies systems worldwide.

Gulf Coast differentiators:

  • Often lowest cost
  • Quality in-house construction
  • Best service techs
  • Limited scrubber options

HEIL Engineered Equipment

HEIL builds wet scrubbers to remove odors, hazardous and corrosive chemicals, and particulates. HEIL provides scrubbers to the Metal Finishing, Chemical Processing, Food/Bev, Pharmaceutical, Fertilizer, Glass/Optics, Pulp/Paper, Semiconductor, and Mining industries.

HEIL differentiators:

  • In-house manufacturing
  • High quality construction
  • In-house design and engineering
  • Limited to 8 industries

Tri-Mer Corporation

Tri-Mer offers wet scrubbers for applications below 300°F. They can build crossflow, packed bed, and fume scrubbers to remove NOx, Particulate Matter (PM), SO2, HCl, HF, HNO3, H2SO4, CI2, NH3 Odors, Chrome, and other fumes.

Tri-Mer Corp differentiators:

  • Many technology options
  • Large in-house fabrication facility
  • Variety of material options
  • Higher cost

Hydro-Sonic Systems

Hydro-Sonic Systems offers wet scrubbers with a steam or tandem nozzle design. They supply scrubbers worldwide with a focus on Texas and the central U.S. They focus on the metals/steel, hazardous/radioactive waste, and chemical processing industries.

Hydro-Sonic Systems differentiators:

  • Optimized for sub-micron particles
  • Expert gas/fluid Engineering
  • Offers sonic-based technologies
  • Only offers wet scrubbers

Pollution Systems

Pollution Systems offers a diverse selection of wet scrubber technologies and designs. They supply primarily to Texas and the Southern US region, with a focus on food processing, metal finishing, and chemical processing.

Pollution Systems differentiators:

  • High quality construction
  • Highest reliability
  • Many technology options
  • Higher cost

Other Types of Scrubbers

  • Scrubbers
Venturi Scrubber
  • Particulate Scrubber
  • Dust Scrubber
Ammonia Scrubber
  • Alkaline Scrubber
NOX Scrubber
  • Boiler Scrubber
Acid Scrubber
  • Sulfuric Acid Scrubber
  • H2S Scrubber
  • Chlorine Scrubber
Coal Scrubber
  • Sulfur Dioxide Scrubber
  • SO2 Scrubber
  • Flue Gas Desulfurization (FGD)
Smokestack Scrubber
  • Power Plant Scrubber

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