Quick Read
- An air pollution scrubber removes contaminants such as gases, fumes, vapours, odours and particulates from industrial gas streams by bringing them into contact with a scrubbing liquid.
- The three main types are Packed Tower Scrubbers, Jet Venturi Fume Scrubbers and High Energy Venturi Scrubbers. They differ in how gas and liquid are brought together.
- Efficiency depends on the scrubber type and its design. Jet Venturi scrubbers achieve dust and particulate removal above 99%, High Energy Venturi scrubbers capture sub-micron particles below 1 micron, and Packed Towers deliver maximum absorption efficiency at low pressure drop.
- Selection starts with the contaminant: gases and vapours, fumes and particulates, or very fine sub-micron dust.
- For wet or saturated gas streams with fine mists and aerosols, a Wet ESP may be a better fit than a scrubber alone.
What Is an Air Pollution Scrubber?
An air pollution scrubber is a device that cleans an industrial gas stream before it is discharged. It brings contaminated gas into close contact with a scrubbing liquid, typically water or a liquid chosen for its chemistry. The pollutants transfer from the gas into the liquid.
Scrubbers are used for two broad purposes:
- Emission control: cleaning exhaust gases so they meet discharge requirements
- Process applications: absorbing specific gases or recovering valuable byproducts from a gas stream
The Common Principle Behind Every Wet Scrubber
Wet scrubbers differ in design, but they all follow the same three-part sequence:
- Contact: Gas and scrubbing liquid are brought together, whether over packing, through a liquid spray or through atomized droplets.
- Capture: Contaminants move from the gas into the liquid through absorption, impact or turbulence.
- Separation: The liquid, now carrying the pollutants, is separated from the gas using a separator or mist eliminator, and clean gas is discharged.
The liquid is then either drained (once-through) or returned to the scrubber (recirculating or recycle), depending on the system design.
The difference between scrubber types lies almost entirely in the contact stage, which in turn shapes what each type captures best.
Types of Air Pollution Scrubbers
| Scrubber Type | How Gas and Liquid Make Contact | Flow Pattern | Energy Comes From |
|---|---|---|---|
| Packed Tower Scrubber | Liquid spreads over a packed bed while gas rises through it | Countercurrent | Liquid distributed over packing |
| Jet Venturi Fume Scrubber | High-pressure liquid sprayed into a cone-shaped throat draws gas in | Co-current | Scrubbing liquid |
| High Energy Venturi Scrubber | High-velocity gas atomizes liquid into ultra-fine droplets in the throat | Gas-driven | Gas stream |
Packed Tower Scrubber
Gas enters at the bottom of the tower and rises through a packed bed, while scrubbing liquid is distributed from the top and flows downward. The packing creates a large surface area for contact, and a mist eliminator ensures clean gas discharge. Each tower is optimized for packing type, liquid chemistry and operating conditions.
Jet Venturi Fume Scrubber
High-pressure scrubbing liquid is sprayed through a nozzle into a cone-shaped throat. The fast-moving liquid creates a vacuum effect that draws in the contaminated gas, and the two mix in the throat. A separator then removes the liquid and captured pollutants. The scrubber has no moving parts and is engineered for high volumes of contaminated gas.
High Energy Venturi Scrubber
Here the gas does the work. It accelerates through the Venturi throat and atomizes the scrubbing liquid into a mist of fine droplets. These droplets capture dust, fumes and gases through impact and turbulence. Throats can be fixed, variable or manually adjustable, and the unit can be installed horizontally or vertically.
Scrubber Efficiency: What Each Type Achieves
Efficiency means different things depending on the contaminant. For gases, it is about absorption. For dust and particulates, it is about capture, and particle size matters a great deal.
| Scrubber Type | Efficiency Strength | Best Captures |
|---|---|---|
| Packed Tower Scrubber | Maximum absorption efficiency with low pressure drop | Pollutants and process gases |
| Jet Venturi Fume Scrubber | Dust and particulate removal above 99%; high removal rates at low velocities | Fumes, odours, particulates and gases such as SO₂, HCl, HF, NH₃ and SiF₄ |
| High Energy Venturi Scrubber | High-efficiency removal of sub-micron particles below 1 micron | Fine dust, fumes and gases |
What Influences Scrubber Efficiency?
Within each type, efficiency depends on how well the scrubber is engineered for the application:
- Contact surface: In packed towers, the packing type determines the surface area available for gas-liquid contact.
- Liquid chemistry: The scrubbing liquid must suit the contaminants being removed.
- Throat configuration: In High Energy Venturi scrubbers, variable or adjustable throats help maintain performance when gas flow fluctuates.
- Flow pattern: Countercurrent flow keeps rising gas in contact with fresh liquid throughout the tower, while Venturi designs rely on intense mixing in the throat.
- Separation: A properly designed separator or mist eliminator ensures captured pollutants leave with the liquid rather than with the clean gas.
- Operating conditions: Gas volume, temperature and corrosiveness all affect design and performance.
How to Select the Right Air Pollution Scrubber
Step 1: Identify the Main Contaminant
| Main Contaminant | Recommended Scrubber |
|---|---|
| Gases and vapours that need absorbing | Packed Tower Scrubber |
| Corrosive gases (SO₂, HCl, HF, NH₃, SiF₄) at high volumes | Jet Venturi Fume Scrubber |
| Fumes, odours and general particulates | Jet Venturi Fume Scrubber |
| Fine dust and fumes that conventional scrubbers miss | High Energy Venturi Scrubber |
| Sub-micron particles below 1 micron | High Energy Venturi Scrubber |
| Fine mists and aerosols in wet or saturated gas | Wet ESP (see below) |
Step 2: Consider Gas Volume and Duty
- High volumes, continuous duty: Jet Venturi Fume Scrubbers are designed for high-load, continuous-duty operation.
- Steady or fluctuating flow: High Energy Venturi Scrubbers with variable or adjustable throats adapt to changing gas flows.
- Small to large installations: Packed Towers can be engineered for anything from small-scale to large industrial installations.
Step 3: Account for Temperature and Corrosion
All three types can be built for corrosive conditions, and Jet Venturi and High Energy Venturi scrubbers also handle high-temperature gas streams. Materials of construction are selected to suit:
| Scrubber Type | Available Materials |
|---|---|
| Packed Tower Scrubber | Wide range of materials for corrosion resistance and cost optimization |
| Jet Venturi Fume Scrubber | Fibreglass, stainless steel or lined metals |
| High Energy Venturi Scrubber | Fibreglass, steel, stainless steel, Incoloy or rubber-lined construction |
Step 4: Decide on Liquid Handling
Choose between once-through operation, where liquid passes once and is drained, and recirculating operation, where liquid is collected and reused. Packed Towers and Jet Venturi scrubbers support both. In a High Energy Venturi scrubber, the liquid is recycled or drained after separation.
Step 5: Consider Maintenance and Installation
- No moving parts: Jet Venturi and High Energy Venturi scrubbers have no moving parts, which keeps maintenance low.
- Installation flexibility: High Energy Venturi scrubbers can be installed horizontally or vertically.
- Long service life: All three are designed for dependable, long-term performance.
When a Scrubber Isn’t Enough: The Wet ESP
Some gas streams are wet or saturated and carry fine mists, acid mists, heavy metals or condensed aerosols. For these, a Wet Electrostatic Precipitator (WESP) may be the better solution.
Instead of a scrubbing liquid, a Wet ESP uses a high-voltage electrical field to charge particles and mists and collect them on grounded electrodes, which are periodically washed with water. It achieves up to 99.9% collection efficiency, including for sub-micron particles, at very low pressure drop. A Wet ESP also works alongside scrubbing, since the gas is pre-scrubbed and cooled before it enters the collector.
(For a full comparison of scrubbers and Wet ESPs, read our guide: Different Types of Air Pollution Control Equipment)
Air Pollution Scrubbers from Mazda Limited
At Mazda Limited, we design and manufacture all three types of air pollution scrubber, along with Wet ESPs, through our Air Pollution Control Division:
- Packed Tower Scrubber: Custom-engineered countercurrent towers for maximum absorption efficiency at low pressure drop
- Jet Venturi Fume Scrubbers: Non-mechanical scrubbers for high-volume, continuous-duty removal of fumes, corrosive gases and particulates
- High Energy Fume Scrubber: Venturi scrubbers for fine dust and sub-micron particles where conventional systems fall short
- Wet ESP: Condensing WESP for fine mists, aerosols and sub-micron particulates in saturated gas streams
Every system we build is engineered around the process conditions of the application, so the scrubber you get is selected for your contaminants rather than adapted from a standard design.
Share your gas composition, flow rate, temperature and emission requirements, and we will recommend the right scrubber for your plant.
Frequently Asked Questions
What does an air pollution scrubber do?
An air pollution scrubber removes contaminants from an industrial gas stream by bringing the gas into close contact with a scrubbing liquid. Pollutants transfer into the liquid, which is then separated from the gas so that clean gas can be discharged.
What are the main types of air pollution scrubbers?
The main types are Packed Tower Scrubbers, Jet Venturi Fume Scrubbers and High Energy Venturi Scrubbers. They differ in how gas and liquid make contact: over a packed bed, through a high-pressure liquid spray, or through liquid atomized by high-velocity gas.
Which scrubber has the highest efficiency?
It depends on the contaminant. Packed Towers deliver maximum absorption efficiency for gases. Jet Venturi scrubbers achieve dust and particulate removal above 99%. High Energy Venturi scrubbers are designed for sub-micron particles below 1 micron.
Which scrubber is best for fine dust and sub-micron particles?
A High Energy Venturi Scrubber is designed for fine dust and sub-micron particles. High-velocity gas atomizes the scrubbing liquid into ultra-fine droplets that capture particles through impact and turbulence. For wet or saturated gas streams, a Wet ESP is also worth considering.
Can scrubbers handle corrosive and high-temperature gases?
Yes. All three types can be built from corrosion-resistant materials. Jet Venturi and High Energy Venturi scrubbers also handle high-temperature conditions, and Jet Venturi scrubbers are effective on gases such as SO₂, HCl, HF, NH₃ and SiF₄.
What is the difference between once-through and recirculating scrubbers?
In a once-through scrubber, the liquid passes through once and is drained. In a recirculating scrubber, the liquid is collected and reused. The choice depends on system design and process requirements.
What information is needed to select a scrubber?
The key inputs are the contaminant type and particle size, gas volume and duty, temperature, corrosiveness, preferred liquid handling and the emission standard to be met.
Conclusion
Every air pollution scrubber follows the same basic idea: contact, capture and separation. The type you choose determines what it captures best. Packed Towers excel at absorbing gases, Jet Venturi scrubbers handle high-volume and corrosive gas loads, and High Energy Venturi scrubbers capture the finest dust and fumes.
Start with the contaminant, then factor in gas volume, temperature, corrosion and liquid handling, and the right scrubber becomes clear. Where saturated gas streams carry fine mists, a Wet ESP can take efficiency further still.
