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Author:
Anna Frank, Equipment Selection Expert
Anna Frank, Equipment Selection Expert
Industrialists often face the challenge of removal of odor to avoid environmental violations and complaints from residents. Specialized odor removal systems help eliminate this byproduct of the industrial process.
Main Sources of Odors
Frequent sources of unpleasant smells include receiving chambers, sand traps, and sludge ponds in wastewater treatment plants, where hydrogen sulfide, ammonia, and mercaptans are produced. Additional sources include solid waste landfills and incinerators. Some of the most highly concentrated sources of ammonia and hydrogen sulfide are pig and poultry farms, as well as biogas plants.
Smells of organic origin containing volatile fatty acids are evident in various food production facilities, including meat processing plants, fish canneries, breweries, and restaurants and fast food outlets.
Smells of organic origin containing volatile fatty acids are evident in various food production facilities, including meat processing plants, fish canneries, breweries, and restaurants and fast food outlets.
Waste processing requiring odor removal
The chemical industry is known to produce pungent and toxic smells, making air odor removal essential to prevent harm to the environment and employees. Harmful fumes, including formaldehyde, phenols, and acidic compounds, are also generated during the production of building materials and in woodworking. Commercial facilities such as dry cleaners (tetrachloroethylene), printing houses (paint vapors, isopropyl alcohol), and underground parking garages (exhaust fumes) represent another source of smells. Air purifiers for odor removal are also used to combat these emissions.
Industrial Odor Removal Methods
The main odor removal solutions are represented by the following methods, each targeting a specific type of pollutant:
1. Wet scrubbers – used to remove acidic, alkaline, and easily soluble compounds. They operate by bringing the contaminated stream into contact with a washing liquid (water or a reagent solution) in a packed column or tray unit. For example, sodium hypochlorite in an alkaline medium is used to neutralize hydrogen sulfide. Scrubbers can process large volumes of air and can also cool the stream and remove dust.
1. Wet scrubbers – used to remove acidic, alkaline, and easily soluble compounds. They operate by bringing the contaminated stream into contact with a washing liquid (water or a reagent solution) in a packed column or tray unit. For example, sodium hypochlorite in an alkaline medium is used to neutralize hydrogen sulfide. Scrubbers can process large volumes of air and can also cool the stream and remove dust.
2. Dry adsorbers – used for a wide range of volatile organic compounds (VOCs): toluene, xylene, styrene, as well as hydrogen sulfide and ammonia (using special grades of carbon). They utilize two mechanisms of action: physical retention of molecules in the micropores of odor removal filters and a chemical reaction with the pollutants. They are often used as a final treatment stage and are not suitable for high-humidity conditions, as moisture can cause the pores to become clogged and lead to operational issues.
3. Catalytic reactors – used to destroy a wide range of compounds, including complex aromatic hydrocarbons, formaldehyde, and acrolein, through oxidation to carbon dioxide and water. They utilize mechanisms such as heating to high temperatures to combust the contaminants, followed by catalytic conversion, and include heat recovery, which returns thermal energy to the system. This type of air odor removal system can be used for high concentrations and complex multi-component smell mixtures.
Selection of Technology and Equipment
The process for selecting suitable odor removal equipment includes the following steps. First, assess the odors to be removed. These are classified by composition into acidic or alkaline gaseous compounds (ammonia, hydrogen sulfide), volatile organic compounds (toluene, formaldehyde), and complex mixtures containing various compounds, as well as dust and grease aerosols.
The smell concentration must also be considered. The selection strategy depends on the concentration range: dry adsorbers are recommended for low concentrations (less than 0.5 g/m³), wet scrubbers for medium concentrations (0.5–5 g/m³), and thermal oxidizers for high concentrations (more than 5 g/m³). Temperature, humidity, and the presence of particulate matter must also be taken into account.
The smell concentration must also be considered. The selection strategy depends on the concentration range: dry adsorbers are recommended for low concentrations (less than 0.5 g/m³), wet scrubbers for medium concentrations (0.5–5 g/m³), and thermal oxidizers for high concentrations (more than 5 g/m³). Temperature, humidity, and the presence of particulate matter must also be taken into account.
Integrated system with wet scrubber and adsorber for industrial odor removal
Overview of an integrated odor removal system
A comparison of filters is provided in the table.
Odor Wet Scrubbers Design, Applications, and Advantages
After selecting a specific filter, equipment parameters such as capacity and physical dimensions are calculated. System capacity is determined by airflow (hydraulic power) as well as process power — the ability to treat a given mass of pollutants per unit of time. Capacity depends not only on air volume but also on contact time. Equipment dimensions and fan power are both determined by the airflow rate.
However, odor removal purifiers should not operate in isolation but rather as part of the building's overall ventilation system or process exhaust system, so it is important to properly integrate them with the existing ventilation.
There are two basic fan connection schemes: before purification (suction) and after (discharge). Each option has its own characteristics. The first eliminates the risk of unpurified gas leakage through the flanges, but the fan then operates with an aggressive environment (before purification). The second option operates with clean air, but requires a highly sealed purification housing to prevent smell from escaping.
When designing a system, pressure drops must be taken into account, as each purification stage creates flow resistance, and often the existing ventilation system does not have the pressure reserve to overcome this resistance. Therefore, the fan capacity must be recalculated or an additional exhaust fan synchronized with the main system must be installed.
To ensure continuous ventilation (HVAC) for industrial odor removal during maintenance activities (such as carbon replacement, scrubber pump repair, or catalyst warm up), a bypass line with a manual or automatic damper is provided.
There are two basic fan connection schemes: before purification (suction) and after (discharge). Each option has its own characteristics. The first eliminates the risk of unpurified gas leakage through the flanges, but the fan then operates with an aggressive environment (before purification). The second option operates with clean air, but requires a highly sealed purification housing to prevent smell from escaping.
When designing a system, pressure drops must be taken into account, as each purification stage creates flow resistance, and often the existing ventilation system does not have the pressure reserve to overcome this resistance. Therefore, the fan capacity must be recalculated or an additional exhaust fan synchronized with the main system must be installed.
To ensure continuous ventilation (HVAC) for industrial odor removal during maintenance activities (such as carbon replacement, scrubber pump repair, or catalyst warm up), a bypass line with a manual or automatic damper is provided.
Biofilter for biological odor removal
Challenges and Risks
Regardless of the filter selected, dust and odor removal may encounter the following problems, which require prompt resolution during operation: corrosion of the housing and internal components; clogging with dust, grease, biofilm, or salt crystals; disruption of the hydraulic balance with the ventilation system; issues with automation performance; and problems related to waste disposal.
Water filter odor removal may be associated with the following problems: freezing at low temperatures (heating must be provided); pump cavitation (the liquid level in the tank must be raised or the water temperature lowered); and foaming (accumulated surfactants or organic contaminants must be removed from the circulating water).
Water filter odor removal may be associated with the following problems: freezing at low temperatures (heating must be provided); pump cavitation (the liquid level in the tank must be raised or the water temperature lowered); and foaming (accumulated surfactants or organic contaminants must be removed from the circulating water).
The most dangerous problem with adsorption air filter odor removal is spontaneous combustion of the carbon when it becomes saturated with flammable organic compounds (acetone, alcohols, solvents), resulting in elevated system temperatures. Therefore, it is important to take preventative measures. These include selecting carbon with a high flash point, limiting the types of substances captured, installing temperature and carbon monoxide sensors, spark arrestors on the air inlet duct, a nitrogen fire suppression system, a bypass line with an automatic damper, and other safeguards. Improper operation can also lead to moisture condensation, premature saturation, channeling due to improper backfilling, and carbon dust carryover.
GIF animation of the adsorber’s operating principle for odor removal
For catalytic reactors used for toxic odor removal, the following problems may arise: poisoning of the catalyst due to the ingress of silicon compounds (silicones, antifoams), phosphorus, lead, arsenic, sulfur (in large quantities), or halogens; and the formation of highly toxic dioxins during incomplete combustion or in the presence of organochlorine compounds combined with improper temperature control.
When industrial and commercial odor removal equipment is improperly integrated into a ventilation system, problems such as negative pressure in the room, fan overload, condensation in the ducts, noise, and vibration can arise. These issues are resolved through precise hydraulic calculations that take into account all network elements, balancing the supply and exhaust air, selecting the correct circuit configuration, and automating the synchronized operation of the devices.
When industrial and commercial odor removal equipment is improperly integrated into a ventilation system, problems such as negative pressure in the room, fan overload, condensation in the ducts, noise, and vibration can arise. These issues are resolved through precise hydraulic calculations that take into account all network elements, balancing the supply and exhaust air, selecting the correct circuit configuration, and automating the synchronized operation of the devices.
FAQ
- 1. We have a mixed flow of chemical and organic smells. Will a single unit handle it?Most often, a combined multi-stage system is required. We can design a custom solution for you.
- 2. Hydrogen sulfide odor removal how does it work?Neutralization occurs through a two stage chemical reaction in a wet scrubber. The gas passes through a packed bed irrigated with a solution of caustic soda and sodium hypochlorite. Hydrogen sulfide is first absorbed by the alkaline medium and then instantly oxidized by the hypochlorite into harmless sulfates and water.
- 3. How should the scrubber be maintained?Monitor pH and reagent levels daily, and inspect the nozzles monthly.
- 4. Will the carbon filters catch fire?If saturated with flammable VOCs (and without temperature control), the carbon can spontaneously combust. That is why it is necessary to install temperature sensors in the bed, spark arrestors at the inlet, and either nitrogen fire suppression systems or bypass lines for emergency situations.
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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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