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Author: Michael Klepik, Chief Executive Officer
Smoke is a volatile substance that forms during combustion and spreads through the air, reducing visibility and making breathing difficult. It consists of a mixture of molecules and ultrafine aerosol particles. The molecular composition of the gaseous component depends on the material being burned but invariably includes toxic substances of both organic and inorganic origin, such as benzene and carbon monoxide.
The aerosol component includes droplets of evaporating oils and tars combined with soot particles. All these components of smoke penetrate the lungs and subsequently enter the bloodstream, causing serious respiratory difficulties and cardiovascular diseases. A smoke filter is designed to protect humans from the harmful effects of smoke.
The aerosol component includes droplets of evaporating oils and tars combined with soot particles. All these components of smoke penetrate the lungs and subsequently enter the bloodstream, causing serious respiratory difficulties and cardiovascular diseases. A smoke filter is designed to protect humans from the harmful effects of smoke.
Wet Scrubber for Boiler
Operating Principle and Definition
According to the standard definition, a flue gas scrubber is an apparatus that uses liquid or solid reagents to capture and neutralize harmful components in combustion gases before their release into the atmosphere.
Dry flue gas cleaning from solid particles is less effective than wet cleaning.
Therefore, when stricter requirements for residual concentrations of impurities are imposed, industrial facilities typically use a wet flue gas scrubber.
What is a flue gas scrubber?
It is a device consisting of a housing similar to that used in dry cyclonic separation, but with internal liquid spraying (usually water with additives).
As the air stream comes into contact with droplets, mist, and liquid flowing down the walls, not only dust particles are captured.
Certain gaseous substances, such as sulfur and nitrogen oxides, also actively interact with the liquid phase and the dissolved chemical additives.
Dry flue gas cleaning from solid particles is less effective than wet cleaning.
Therefore, when stricter requirements for residual concentrations of impurities are imposed, industrial facilities typically use a wet flue gas scrubber.
What is a flue gas scrubber?
It is a device consisting of a housing similar to that used in dry cyclonic separation, but with internal liquid spraying (usually water with additives).
As the air stream comes into contact with droplets, mist, and liquid flowing down the walls, not only dust particles are captured.
Certain gaseous substances, such as sulfur and nitrogen oxides, also actively interact with the liquid phase and the dissolved chemical additives.
Main Structural Elements
The flue gas scrubber design depends on the type of unit. Below are the key components of a typical system:
- The main chamber is a vertical or horizontal column made of acid-resistant steel or plastic. It is conventionally divided into zones: the contact section, the demister, and the drainage part.
- The flue gas inlet is usually located on the lower side section. It is often equipped with a flow distribution system.
- The spraying system includes nozzles or jets that disperse water or an absorbent (e.g., alkaline solution). This ensures maximum phase contact.
- In the contact zone, the air flows upward while liquid droplets move downward. A counterflow is created for efficient pollutant capture.
- The demister captures liquid droplets carried along with the airflow. It is often made of PTFE mesh, stainless steel, or PVC.
- The cleaned air exits through the top of the tower, sometimes passing through additional filtration.
- The liquid collection system is located at the bottom and may include filtration and recirculation of the liquid back into the process.
Equipment Diagram
🧪 Optional additional components include:
- pH monitoring and reagent dosing (e.g., NaOH for acid pollutants removal)
- Heat exchanger — in condensing scrubber models
- Sensors for temperature, pressure, flow, and liquid level
- Automatic control and emissions monitoring system
Equipment in Practice
The flue gas wet scrubber is widely used in steam boilers, water heaters, and various other thermal and power-generating equipment.
Flue gas scrubber technology significantly reduces the emission of tar, resin particles, and other potentially hazardous carcinogenic substances into the atmosphere.
Key advantages of a flue gas scrubber unit include:
The housing is relatively easy to disassemble, and the nozzles are regularly cleaned, serviced, and replaced when necessary.
At facilities operating in continuous mode, standby mist eliminators are installed, allowing flow to be redirected during maintenance of spray towers.
Among advanced technologies, the fluidized bed scrubber is one of the most effective for removing particulate-laden smoke.
Flue gas scrubber technology significantly reduces the emission of tar, resin particles, and other potentially hazardous carcinogenic substances into the atmosphere.
Key advantages of a flue gas scrubber unit include:
- The ability to treat large volumes of flue gases — from tens of cubic meters in small systems to hundreds of thousands of cubic meters at large industrial facilities.
- Stable performance in conditions involving heat, flammable mixtures, aggressive chemical vapors, and aerosol contaminants.
- Near-100% efficiency in removing toxic components from the air stream.
- Affordable price combined with low operating costs, ensuring quick return on investment.
The housing is relatively easy to disassemble, and the nozzles are regularly cleaned, serviced, and replaced when necessary.
At facilities operating in continuous mode, standby mist eliminators are installed, allowing flow to be redirected during maintenance of spray towers.
Among advanced technologies, the fluidized bed scrubber is one of the most effective for removing particulate-laden smoke.
In tray towers, in addition to water being sprayed through nozzles, rotating trays with small openings are used to further enhance mixing within the tower.
Water often falls in a continuous curtain, creating a fine mist inside that effectively captures dust particles.
Hollow scrubbers, systems with moving packing, and centrifugal units are also suitable for this purpose.
Water often falls in a continuous curtain, creating a fine mist inside that effectively captures dust particles.
Hollow scrubbers, systems with moving packing, and centrifugal units are also suitable for this purpose.
Condensing Flue Solution
A condensing flue gas scrubber is a device designed for both the purification and heat recovery from flue gases generated during fuel combustion. These systems are used in boilers where exhaust contains a high concentration of water vapor — enabling both pollutant removal and energy savings.
The key distinction from other types of scrubbers lies in the condensation of water vapor. This unit not only purifies the gases but also recovers additional energy from the latent heat of vapor, increasing overall equipment efficiency by 5–15%.
Main functions:
A condensing flue gas scrubber is a device designed for both the purification and heat recovery from flue gases generated during fuel combustion. These systems are used in boilers where exhaust contains a high concentration of water vapor — enabling both pollutant removal and energy savings.
The key distinction from other types of scrubbers lies in the condensation of water vapor. This unit not only purifies the gases but also recovers additional energy from the latent heat of vapor, increasing overall equipment efficiency by 5–15%.
Main functions:
- Condensation — Water vapor in the flue gases condenses, releasing latent heat. This recovered heat can be reused (e.g., for space or process heating).
- Purification — Along with the moisture, fine particulates, dust, sulfur compounds (SO₂), chlorine, fluorine, and other contaminants are removed from the gas stream.
- Condensate removal — The collected condensate is drained and, if necessary, further treated or safely discharged.
- Bioenergy plants (burning wood chips, pellets, or biomass)
- Boiler houses and CHP (combined heat and power) plants, especially those using moist fuels
- Industrial facilities requiring high ecological efficiency and energy optimization
Cost Estimation
Flue gas scrubber cost varies widely depending on unit design, throughput capacity, required pollutant removal efficiency, and the inclusion of advanced features such as vapor condensation. Below are the main cost components:
💰 Estimated Cost by Boiler Size:
Feel free to contact us for assistance with system selection and complete technical calculations.
Cost Component | Description | Approximate Share of Total Cost (%) | Price Range (USD) |
System Type | Wet, dry, or condensing — affects design complexity | 20–30% | $10,000 – $1,500,000+ |
Capacity (m³/h or SCFM) | The higher the air volume, the higher the cost | 20–35% | $20,000 – $2,000,000+ |
Construction Materials | Stainless steel, FRP, corrosion-resistant alloys and coatings | 10–15% | $5,000 – $500,000 |
Purification Level | Based on SO₂, dust, HCl, carcinogens, etc. removal requirements | 5–10% | $3,000 – $300,000 |
Automation & Sensors | PLC, pump controls, pressure/temperature/level sensors | 5–10% | $5,000 – $100,000 |
Installation & Commissioning | Installation, integration, and system startup | 10–25% | $10,000 – $500,000 |
Auxiliary Systems | Condensate drainage, reagent supply, spare components | 5–10% | $2,000 – $200,000 |
Certification & Compliance | EPA, OSHA, UL, ASME standards | 2–5% | $1,000 – $50,000 |
💰 Estimated Cost by Boiler Size:
Application | Estimated Cost (USD) |
Small boiler (up to 1 MW) | $50,000 – $150,000 |
Industrial boiler (1–10 MW) | $150,000 – $500,000 |
Power plant / CHP facility | $1 million – $5+ million |
Feel free to contact us for assistance with system selection and complete technical calculations.
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We always perform precise calculations and offer expert assistance in selecting the optimal dust collection or gas cleaning systems, typically completing this process within 1 to 2 days
Head of Engineering,
Vladimir Nikulin
Vladimir Nikulin
CALCULATION AND SELECTION
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