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Author:
Anna Frank, Equipment Selection Expert
Anna Frank, Equipment Selection Expert
Emissions into the atmosphere have a negative impact on the overall environmental situation, and elevated levels of harmful substances in workplaces lead to numerous serious illnesses. Many technological processes are accompanied by the release of emissions into the air. Organized emissions are those that enter the atmosphere through chimney stacks, ventilation systems, and other devices that are part of the production technological cycle.
Common organized emissions include tail gases, which are formed at the final stage of a technological process. They accumulate in the air at high concentrations and contain a large amount of pollutants. A typical example is the ‘fox tail’ nitrogen, which forms as a result of photochemical reactions involving oxides in the atmosphere.
Common organized emissions include tail gases, which are formed at the final stage of a technological process. They accumulate in the air at high concentrations and contain a large amount of pollutants. A typical example is the ‘fox tail’ nitrogen, which forms as a result of photochemical reactions involving oxides in the atmosphere.
TORNADO ST Spray Tower
Sources
Exhaust gases are produced in nearly all processes involving fuel combustion or chemical reactions. Their composition varies depending on the equipment, raw materials, and operational conditions, but in every case, such emissions require monitoring and frequently treatment due to their potential harm to humans and the environment. Examples from various industrial sectors include:
- Boiler fired with natural gas: releases products of combustion such as CO₂, H₂O (steam), NOₓ, and trace amounts of CO.
- Chemical industry (e.g., sulfuric acid production): emits SO₂, SO₃, inert components like N₂ and O₂, along with water vapor.
- Metallurgical operations: discharge blast furnace gases containing CO, CO₂, N₂, particulate matter, and minor quantities of H₂ and CH₄.
- Waste incineration facilities: release HCl, HF, SO₂, NOₓ, CO₂, CO, dioxins and furans (prior to purification), as well as dust and heavy metals.
Residual Emissions
Properties and Hazards
Exhausts contain both volatile substances and microscopic solid or liquid particles. Their characteristics depend on the source, but they typically exhibit toxicity, corrosive potential, a tendency to form aerosols, and the presence of tiny particles capable of remaining suspended in the air for extended periods. Components of exhaust emissions—such as carbon monoxide, nitrogen oxides, sulfur dioxide, and dioxins—can adversely affect living organisms, even at relatively low levels.
The hazards of tail gases stem from their ability to cause both acute and chronic poisoning, degrade urban air quality, contribute to acid rain, promote photochemical smog, damage the ozone layer, and trigger other environmental issues. Fine particulate matter (PM2.5 and PM10) penetrates deep into the respiratory system and is linked to cardiovascular and pulmonary diseases. A number of organic compounds in exhaust fumes have cancer-causing potential.
For these reasons, monitoring, regulatory control, and purification of such emissions are essential for environmental safety and industrial responsibility. Wet tail gas scrubber is commonly used to remove hazardous substances from the air.
The hazards of tail gases stem from their ability to cause both acute and chronic poisoning, degrade urban air quality, contribute to acid rain, promote photochemical smog, damage the ozone layer, and trigger other environmental issues. Fine particulate matter (PM2.5 and PM10) penetrates deep into the respiratory system and is linked to cardiovascular and pulmonary diseases. A number of organic compounds in exhaust fumes have cancer-causing potential.
For these reasons, monitoring, regulatory control, and purification of such emissions are essential for environmental safety and industrial responsibility. Wet tail gas scrubber is commonly used to remove hazardous substances from the air.
Functions and Operating Principle
A wet scrubber is a cylindrical column-type device in which captured particles are absorbed by a liquid, which carries them out of the apparatus in the form of sludge.
The primary tail gas scrubber function is, of course, filtration and purification of the exhaust stream. The unit can eliminate gaseous pollutants with an efficiency of up to 99.9%. It is also highly effective at capturing solid contaminants — dust, soot, and various aerosols.
Because the gas comes into direct contact with the liquid, it is simultaneously cooled, which may be necessary for subsequent treatment stages.
In a tail gas scrubber oxidizer, air purification is accompanied by oxidation. This feature makes the system particularly suitable for removing sulfur-bearing compounds and other toxic substances.
The exhaust stream passes through a scrubbing liquid containing an oxidizing agent (for instance, oxygen, air, or specific chemical reagents). For example, residual SO₂ in the exhaust stream is captured by an acid plant tail gas scrubber, which transforms sulfur and other impurities into less harmful compounds (e.g., SO₂ → SO₃ → H₂SO₄)
The primary tail gas scrubber function is, of course, filtration and purification of the exhaust stream. The unit can eliminate gaseous pollutants with an efficiency of up to 99.9%. It is also highly effective at capturing solid contaminants — dust, soot, and various aerosols.
Because the gas comes into direct contact with the liquid, it is simultaneously cooled, which may be necessary for subsequent treatment stages.
In a tail gas scrubber oxidizer, air purification is accompanied by oxidation. This feature makes the system particularly suitable for removing sulfur-bearing compounds and other toxic substances.
The exhaust stream passes through a scrubbing liquid containing an oxidizing agent (for instance, oxygen, air, or specific chemical reagents). For example, residual SO₂ in the exhaust stream is captured by an acid plant tail gas scrubber, which transforms sulfur and other impurities into less harmful compounds (e.g., SO₂ → SO₃ → H₂SO₄)
Packed Bed Tower Operation
TORNADO FB
The tail gas scrubber operation is based on washing the contaminated flow with a dedicated solution or water. Polluted air enters the tower through an inlet nozzle and moves into the contact zone, where it encounters the liquid. The interaction can occur through packing elements or trays that increase the contact surface, through sprayed liquid jets, or through rising solution bubbles. Harmful substances dissolve in or react with the absorbent. Example reaction:
SO₂ + NaOH → Na₂SO₃
Impurities settle in the lower section of the vessel (the sump). The purified stream rises and exits through the outlet duct, containing only minimal residual pollutants.
The scrubbing liquid may be recirculated after treatment or discharged to a waste-handling system.
SO₂ + NaOH → Na₂SO₃
Impurities settle in the lower section of the vessel (the sump). The purified stream rises and exits through the outlet duct, containing only minimal residual pollutants.
The scrubbing liquid may be recirculated after treatment or discharged to a waste-handling system.
Types of Designs
Wet-type air-extraction systems have proven highly effective in removing hazardous compounds and particulate matter. Emissions such as the “fox tail” plume can be captured with up to 98% efficiency. Depending on the initial parameters (composition and volume of the exhaust stream, gas temperature, type of scrubbing solution, and other factors), purification may be carried out using conventional steel equipment or plastic tail gas scrubber systems.
H3: Packed Bed Scrubbers
These systems are constructed as vertical columns filled with packing of various shapes. Typically, contaminated air enters the unit from the bottom. The packing may consist of large geometrically shaped bodies or masses of small elements such as balls, shavings, or rings. The packing is either supported on a grid or tightly loaded within the column. Under suitable conditions, the efficiency of a tail gas scrubber for ammonia and other compounds may approach 100%.
Spray Towers and Venturi Scrubbers
Spray towers consist of vertically oriented chambers where the air mixture is introduced under pressure. Nozzles spray water into the flow, and the droplets capture contaminants. The nozzle layout ensures that the mixture is washed from all possible directions. Depending on the configuration, the number of spray layers can be one, two, or three. The polluted liquid drains into a collection basin for further treatment or disposal, while the cleaned air—still containing fine droplets—moves into a demister. The final step is the discharge of purified air from the unit.
In Venturi units, the contaminated airflow is introduced tangentially. Inside the chamber, the stream forms a vortex and meets water delivered through nozzles. Close contact between phases ensures efficient mass transfer. Thanks to the large wetted surface area, pollutant capture is extremely effective.
In Venturi units, the contaminated airflow is introduced tangentially. Inside the chamber, the stream forms a vortex and meets water delivered through nozzles. Close contact between phases ensures efficient mass transfer. Thanks to the large wetted surface area, pollutant capture is extremely effective.
Bubble-Tray (Barbotage) Units
These devices contain circular trays that rotate and are continuously sprayed with a solution. The polluted stream flows through small openings in the trays, where it interacts with the liquid. During this barbotage process, bubbles form inside the tail gas scrubber pot. If surfactants are added to the liquid, the internal volume becomes filled with foam, enhancing the contact between phases.
Plastic Scrubbers
These systems are suitable for removing chemical compounds, acids, alkalis, and many other types of pollutants. Plastic materials are resistant to corrosion and aggressive contaminants, which makes them widely used in chemical-processing applications. They are also employed in machinery manufacturing, metalworking, the chemical and food industries, pharmaceuticals, and laboratories to remove nitrogen oxides and other substances.
Our company manufactures both plastic and steel scrubbers that provide reliable emission control. Based on the chemical composition, airstream temperature, and operational conditions, our specialists will assist in selecting the optimal configuration free of charge.
Our company manufactures both plastic and steel scrubbers that provide reliable emission control. Based on the chemical composition, airstream temperature, and operational conditions, our specialists will assist in selecting the optimal configuration free of charge.
Design and Engineering
Tail gas scrubber design is carried out in several stages, and the first step is gathering complete information about the composition of pollutants generated at the facility. The primary purpose of this system is to reduce harmful substances in the exhaust stream—such as acid fumes, soot, ammonia, and volatile organic compounds—to safe levels before they are discharged into the atmosphere or sent for further processing.
Design parameters and the choice of configuration depend on:
Material Selection
Stainless steel is suitable for acidic vapors. Polypropylene, PVC, and fluoroplastics are chosen for highly aggressive chemicals. Fiberglass is used for mildly corrosive components.
Design parameters and the choice of configuration depend on:
- Pollutant composition – acids, alkalis, organics, dust.
- Air flow rate and velocity – used to size the tail gas scrubber vessel and the contact section.
- Temperature and pressure – determine the appropriate construction materials.
- Required removal efficiency – percentage of contaminants that must be eliminated.
- Corrosion resistance – materials must tolerate aggressive chemical environments.
Material Selection
Stainless steel is suitable for acidic vapors. Polypropylene, PVC, and fluoroplastics are chosen for highly aggressive chemicals. Fiberglass is used for mildly corrosive components.
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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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