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Author: Nikulin V, Head of Engineering
What is an acid gas scrubber? It is industrial system engineered to neutralize or remove acidic components from gas streams before they are released into the atmosphere. This equipment operates based on the principle of mass transfer, where corrosive vapors are absorbed into a liquid or solid medium and subsequently neutralized through chemical reactions.
Principle of Operation
How does an acid scrubber work? Equipment operate by bringing contaminated air streams into intimate contact with a liquid—typically water or an alkaline solution—inside a specially engineered chamber or tower. The process is driven by mass transfer principles, where gaseous acid molecules diffuse across the gas-liquid interface and dissolve into the solution. Once absorbed, these corrosive compounds undergo neutralization reactions, often involving a base such as sodium hydroxide (NaOH), resulting in the formation of non-volatile salts like sodium chloride (NaCl), sodium sulfate (Na₂SO₄), or sodium nitrate (NaNO₃), depending on the acid type.
The internal configuration of a wet acid scrubber typically includes a packed bed, spray nozzles, and droplet separators:
The internal configuration of a wet acid scrubber typically includes a packed bed, spray nozzles, and droplet separators:
- Packed bed: Filled with high-surface-area media (e.g., plastic or ceramic saddles), this section maximizes the contact area between air and liquid, promoting efficient absorption.
- Spray nozzles: These distribute the liquid evenly across the gas stream, enhancing droplet dispersion and improving capture efficiency.
- Mist eliminators (demisters): Positioned at the outlet to remove entrained liquid droplets, preventing carryover and ensuring clean air discharge.
- The liquid is usually recirculated via pumps, with continuous monitoring of pH and concentration to maintain optimal reactivity. In many systems, make-up water and reagents are added automatically to compensate for evaporation and reagent consumption.
Engineer’s Review
Thermodynamic conditions, such as temperature and pressure, also affect gas solubility and reaction kinetics. Elevated temperatures can reduce absorption efficiency for some compounds, while higher pressures generally enhance air-liquid interaction. Therefore, equipment design must consider process conditions and target contaminants to ensure effective operation.
Properly configured equipment can remove over 95–99% of acidic pollutants from exhaust gases, making them suitable for industries such as chemical production, mining, semiconductor manufacturing, and metal surface treatment.
The efficiency of an acid vapor scrubber is influenced by several factors, including air flow rate, concentration of pollutants, temperature, pressure, and the chemical properties of the cleaning media. An acid exhaust scrubber, when properly engineered and operated, delivers over 95% removal efficiency of harmful vapors.
Properly configured equipment can remove over 95–99% of acidic pollutants from exhaust gases, making them suitable for industries such as chemical production, mining, semiconductor manufacturing, and metal surface treatment.
The efficiency of an acid vapor scrubber is influenced by several factors, including air flow rate, concentration of pollutants, temperature, pressure, and the chemical properties of the cleaning media. An acid exhaust scrubber, when properly engineered and operated, delivers over 95% removal efficiency of harmful vapors.
Maximum Operating Temperatures for Scrubbers and Resistance to Acids
Types of Acid Scrubbers and Their Features
There are two primary categories of acid scrubbers: wet and dry types.
Wet Scrubbers use a liquid medium, typically water or an alkaline solution, to remove toxic vapors from the air. They are versatile and can handle high-temperature and high-moisture gas streams. Key components include a contactor (such as a packed bed tower), demister, and recirculation pump. Wet air cleaning systems are highly efficient for absorbing a wide range of corrosive compounds and are suitable for continuous operation in harsh industrial environments.
Torch-Air's wet scrubbers are designed with high chemical resistance and corrosion-proof materials to ensure durability and efficiency. These units are commonly used in chemical manufacturing, metal processing, and waste gas treatment applications.
Wet Scrubbers use a liquid medium, typically water or an alkaline solution, to remove toxic vapors from the air. They are versatile and can handle high-temperature and high-moisture gas streams. Key components include a contactor (such as a packed bed tower), demister, and recirculation pump. Wet air cleaning systems are highly efficient for absorbing a wide range of corrosive compounds and are suitable for continuous operation in harsh industrial environments.
Torch-Air's wet scrubbers are designed with high chemical resistance and corrosion-proof materials to ensure durability and efficiency. These units are commonly used in chemical manufacturing, metal processing, and waste gas treatment applications.
Dry Scrubbers (Droplet Mist Eliminators): Also known as droplet separators or demisters, adsorption towers function without a liquid phase and instead rely on inert solid media or physical separation mechanisms to trap caustic aerosols and vapors. Torch-Air offers lamellar droplet mist eliminators, which can be augmented with mesh-type configurations upon request. These units are especially effective when inlet pollutant concentrations are high and particulate matter is minimal.
Dry gas cleaning systems are ideal for scenarios where liquid handling is impractical or restricted due to regulatory or process limitations. In some cases, droplet mist eliminators are employed downstream of wet scrubbers to capture residual mist and improve overall efficiency. Additionally, the recovered acid condensate can be returned to the storage tank for reuse, contributing to resource efficiency.
A scrubber for acid feed is engineered to remove corrosive vapors from the gas stream before it enters the chemical processing unit.
Dry gas cleaning systems are ideal for scenarios where liquid handling is impractical or restricted due to regulatory or process limitations. In some cases, droplet mist eliminators are employed downstream of wet scrubbers to capture residual mist and improve overall efficiency. Additionally, the recovered acid condensate can be returned to the storage tank for reuse, contributing to resource efficiency.
A scrubber for acid feed is engineered to remove corrosive vapors from the gas stream before it enters the chemical processing unit.
The Acid Tank Vent Scrubber is designed specifically for tank venting applications. This equipment ensures that corrosive vapors released during filling, storage, or pressure equalization are captured and neutralized.
Portable acid gas scrubbers are compact, mobile systems engineered to neutralize and remove corrosive vapors from industrial emissions. These units are particularly useful in temporary or field applications, where permanent installations are not feasible or necessary. They provide a flexible solution for industries like construction, chemical manufacturing, and maintenance operations, offering an effective way to comply with environmental regulations during short-term projects.
These portable units typically utilize a combination of alkaline solutions and filtration media to capture and neutralize harmful vapors. Because of their smaller size and portable design, they are ideal for use in areas with limited space or in situations where temporary control of emissions is required. These units can be easily moved between different locations and deployed quickly, making them a valuable tool for emergency situations, temporary processes, or areas undergoing maintenance. While they may have lower capacity compared to stationary equipment, their mobility and ease of setup make them a practical choice for short-term air quality management.
These portable units typically utilize a combination of alkaline solutions and filtration media to capture and neutralize harmful vapors. Because of their smaller size and portable design, they are ideal for use in areas with limited space or in situations where temporary control of emissions is required. These units can be easily moved between different locations and deployed quickly, making them a valuable tool for emergency situations, temporary processes, or areas undergoing maintenance. While they may have lower capacity compared to stationary equipment, their mobility and ease of setup make them a practical choice for short-term air quality management.
Experience and Application of Acid Scrubbers: Real Cases
Applications for Specific Acids
Types and Applications | Key Features and Requirements |
Acetic Acid Scrubber | CH₃COOH emissions are common in the food processing and chemical industries. Units must be constructed with materials resistant to organic acid corrosion, such as FRP or polypropylene. They often use water or diluted alkali as the cleaning medium. |
Hydrofluoric Acid Scrubber | Due to its high reactivity and toxicity, HF requires specialized units with fluoropolymer linings and advanced mist elimination stages. Packed bed towers with caustic soda (NaOH) solutions are frequently employed to ensure effective neutralization. |
Phosphoric Acid Scrubber | H₃PO₄ vapors are primarily encountered in fertilizer manufacturing and phosphate processing. Configurations with packed beds and high-efficiency demisters are effective for capturing these emissions. Material selection is crucial due to the abrasive nature of phosphate dust. |
Caustic Scrubbers for Sulfuric Acid | They are among the most commonly used systems in industrial gas treatment. Configurations with multiple contact stages and integrated mist eliminators are used to achieve compliance with environmental discharge standards. H₂SO₄ droplets are highly corrosive, requiring the use of stainless steel, lined configurations, or specialized plastics such as PVC, PP, or PVDF to ensure long-term durability. |
Hydrochloric Acid Scrubber (Alkaline) | Widely used in galvanizing, pickling, and chlorine production, these units utilize a countercurrent flow design to maximize contact between the gas and the alkaline cleaning liquid. |
Perchloric Acid Scrubber | These units are engineered with special safety features due to the highly reactive and oxidizing nature of HClO₄. Applications include laboratory exhaust systems and chemical synthesis processes. |
Each caustic-specific application demands tailored engineering to match the chemical and physical properties of the target contaminants.
You can request the latest acid scrubber design pricelist to compare models and select the optimal solution for your application:
+1 (918) 406-5684
info@torch-air.com
Maintenance and Support
Routine acid scrubber maintenance is essential to ensure long-term performance, operational safety, and compliance with environmental regulations. Treatment units, especially those handling aggressive chemical compounds, are prone to degradation that must be managed proactively.
Key maintenance activities include:
1. Inspection of packing materials and internals: Regular checks should be performed to detect fouling, clogging, or material degradation in structured or random packing. Accumulated residues can impede gas-liquid contact and reduce efficiency.
2. Monitoring of pH and reagent concentration: The chemical effectiveness of the cleaning solution depends on maintaining appropriate alkalinity levels. Automated dosing systems often support this function, but periodic manual testing remains necessary for calibration and control.
3. Pump and nozzle verification: Recirculation pumps and spray nozzles must be checked for wear, blockages, and pressure consistency. Reduced flow or uneven distribution can compromise absorption and lead to equipment inefficiency.
Key maintenance activities include:
1. Inspection of packing materials and internals: Regular checks should be performed to detect fouling, clogging, or material degradation in structured or random packing. Accumulated residues can impede gas-liquid contact and reduce efficiency.
2. Monitoring of pH and reagent concentration: The chemical effectiveness of the cleaning solution depends on maintaining appropriate alkalinity levels. Automated dosing systems often support this function, but periodic manual testing remains necessary for calibration and control.
3. Pump and nozzle verification: Recirculation pumps and spray nozzles must be checked for wear, blockages, and pressure consistency. Reduced flow or uneven distribution can compromise absorption and lead to equipment inefficiency.
TORNADO-FB Fluidized Bed Scrubber
4. Demister and droplet eliminator replacement: Mist eliminators (e.g., lamellar or mesh types) should be cleaned or replaced regularly to prevent pressure drop increases and to ensure efficient capture of entrained liquid particles.
5. Corrosion monitoring: Surfaces exposed to corrosive vapors or condensates, particularly metallic components, require inspection for pitting, scaling, or stress corrosion cracking.
Torch-Air provides comprehensive technical support, including spare parts supply, on-site inspection, retrofitting, and system upgrades. To minimize unplanned downtime, the company offers preventive maintenance plans, which may include scheduled site visits, performance audits, and replacement part forecasting.
Additionally, remote monitoring systems can be integrated into equipment to track operational parameters in real time. These units support predictive maintenance strategies, allowing early identification of deviations and minimizing emergency shutdowns.
All Torch-Air systems are delivered with detailed technical documentation, including operation and maintenance manuals, P&ID diagrams, and safety data sheets (SDS), ensuring smooth integration into existing process infrastructures.
5. Corrosion monitoring: Surfaces exposed to corrosive vapors or condensates, particularly metallic components, require inspection for pitting, scaling, or stress corrosion cracking.
Torch-Air provides comprehensive technical support, including spare parts supply, on-site inspection, retrofitting, and system upgrades. To minimize unplanned downtime, the company offers preventive maintenance plans, which may include scheduled site visits, performance audits, and replacement part forecasting.
Additionally, remote monitoring systems can be integrated into equipment to track operational parameters in real time. These units support predictive maintenance strategies, allowing early identification of deviations and minimizing emergency shutdowns.
All Torch-Air systems are delivered with detailed technical documentation, including operation and maintenance manuals, P&ID diagrams, and safety data sheets (SDS), ensuring smooth integration into existing process infrastructures.
Materials and Filtration Media
Acid scrubber material selection is critical in its construction. Depending on the process environment, common materials include fiberglass-reinforced plastic (FRP), polypropylene (PP), polyvinylidene fluoride (PVDF), and various grades of stainless steel (such as 316L). Each offers specific advantages in terms of corrosive resistance, temperature tolerance, and structural integrity.
Filtration media varies by design but typically includes structured packing, random packing, demister pads, and mesh filters. These components maximize surface area for mass transfer and facilitate the removal of fine mists or droplets. Torch-Air offers custom filtration assemblies optimized for different corrosive gas streams and operational requirements.
Selecting the appropriate acid scrubber media and construction materials not only ensures durability, but also lowers the total cost of ownership by reducing maintenance needs and replacement frequency.
Whether employing wet systems for broad-spectrum corrosive neutralization or dry droplet mist eliminators for specific applications, proper design, material selection, and maintenance are key to effective operation. Torch-Air's comprehensive range of solutions supports diverse industrial needs with high-performance, customizable air cleaning systems.
Filtration media varies by design but typically includes structured packing, random packing, demister pads, and mesh filters. These components maximize surface area for mass transfer and facilitate the removal of fine mists or droplets. Torch-Air offers custom filtration assemblies optimized for different corrosive gas streams and operational requirements.
Selecting the appropriate acid scrubber media and construction materials not only ensures durability, but also lowers the total cost of ownership by reducing maintenance needs and replacement frequency.
Whether employing wet systems for broad-spectrum corrosive neutralization or dry droplet mist eliminators for specific applications, proper design, material selection, and maintenance are key to effective operation. Torch-Air's comprehensive range of solutions supports diverse industrial needs with high-performance, customizable air cleaning systems.
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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
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