Sulfuric Acid Mist Scrubber

Product Model	Acid and Alkali Mist Spray Absorption Tower Series
Category	Waste Gas Treatment Equipment
Reference Price	Price on request

Hot Customizable for Working Conditions 10 Technical Parameters

Product Overview

The acid mist purification tower is a spray absorption device specifically designed for acid mist and certain alkaline gases generated in pickling, electroplating, chemical processing and other operations. The tower body is welded from PP or PPs sheets and is corrosion-resistant to acids and alkalis. Acid mist-laden exhaust gas is drawn into the tower by a fan and flows countercurrently against the alkaline absorption liquid (typically sodium hydroxide solution) sprayed from the spray layer. Acidic pollutants are captured by droplets and the liquid film on the packing surface, where neutralization reactions take place. The purified gas is discharged after demisting, while the absorption liquid circulates in the water tank at the tower bottom, with alkali solution replenished and replaced periodically.

The acid mist purification tower is effective against a wide range of water-soluble gases. Common treatment targets include hydrogen chloride, nitric acid mist, hydrofluoric acid mist, sulfuric acid mist, chromic acid mist, hydrogen cyanide, ammonia, sodium hydroxide vapor and hydrogen sulfide. Acidic gases are neutralized with alkaline absorption liquids such as sodium hydroxide, while alkaline gases such as ammonia are treated with acidic absorption liquids. The equipment features high purification efficiency, corrosion-resistant construction, high strength, low noise, low power consumption, compact size, and easy disassembly and maintenance. It is the most widely used acid-alkali exhaust gas treatment equipment in the electroplating, surface treatment, metallurgical pickling and chemical industries.

Xicheng Environmental Protection can design acid mist purification towers according to exhaust gas type, concentration and treatment airflow, configured with packing layers, spray layers, demisting devices, circulating water pumps and chemical dosing systems. Tower diameter and height are calculated based on the airflow, and PP or PPs sheet material is available as an option. Multiple towers in series are supported for treating high-concentration or multi-pollutant exhaust gas, and automatic pH chemical dosing control can be provided to ensure stable and compliant purification performance.

Working Principle

The acid mist purification tower operates on the principles of acid-alkali neutralization and gas-liquid absorption. After entering the tower, acid mist-laden exhaust gas passes upward through the packing layer. The circulation pump delivers the alkaline absorption liquid to the spray pipe at the top of the tower, where it is sprayed evenly downward through nozzles, forming a liquid film on the packing surface and filling the space with fine droplets. The exhaust gas contacts the absorption liquid countercurrently in the packing voids; acid mist particles are scrubbed and captured by the droplets, while acidic gases dissolve in the liquid film and undergo neutralization reactions with the alkali solution to form salts. Gaseous pollutants are transferred into the liquid phase, and the gas is purified.

The direction of the neutralization reaction depends on the pollutant: acidic gases are treated with alkaline absorption liquids—for example, hydrogen chloride reacts with sodium hydroxide to form sodium chloride and water, and the same applies to sulfuric acid mist and nitric acid mist—while alkaline gases such as ammonia are treated with acidic absorption liquids such as dilute sulfuric acid. The packing layer provides a large gas-liquid contact area to improve absorption efficiency. The purified gas rises with entrained droplets and is dewatered and demisted by the demister plate (baffle plates or wire mesh) at the top or outlet of the tower before being discharged by the fan. The liquid that has absorbed pollutants falls into the water tank at the tower bottom for recirculation. As the salt concentration gradually increases, absorption capacity is maintained through regular blowdown, water replacement and replenishment with fresh absorption liquid, and the wastewater is discharged to the wastewater treatment system.

Structural Composition

The acid mist purification tower consists of a tower body, air inlet section, packing layer, spray layer, demisting layer, circulation water tank, circulating water pump and chemical dosing system. The tower body is a cylindrical shell rolled and welded from PP or PPs sheets, with reinforcing rings on the outer wall. The tower bottom serves as the circulation water tank; the air inlet is arranged tangentially or frontally at the lower part, and the air outlet is located at the top or on the side.

Inside the tower, from bottom to top, are arranged the packing support grid, packing layer (polyhedral balls or Raschig rings), spray pipes and nozzles; multiple stages of packing and spraying can be provided, with a demister plate in the upper section. The water tank is equipped with make-up water, overflow, blowdown and chemical dosing ports as well as a level gauge. The circulating water pump draws liquid from the tank, pressurizes it and delivers it to the spray pipes. The chemical dosing system consists of a dosing tank, metering pump and online pH meter, automatically replenishing alkali or acid according to the pH of the circulating liquid. The tower body is fitted with manholes, inspection doors, ladders and platforms, and observation ports are provided to check the spray and packing conditions. The inlet and outlet air ports are equipped with flanges for connection to ducts and fans.

Specification and Model Table

The table below shows the main treatment targets and absorption liquid configurations of the acid mist purification tower; specific designs are based on the exhaust gas composition.

Exhaust Gas Type	Representative Pollutants	Absorption Liquid
Acidic gases	Hydrogen chloride, sulfuric acid mist, nitric acid mist	Sodium hydroxide alkali solution
Fluorine-containing gases	Hydrogen fluoride, hydrofluoric acid mist	Alkali solution absorption
Alkaline gases	Ammonia	Acidic absorption liquid

Product Features

The acid mist purification tower offers strong targeting, high purification efficiency and economical operation, making it a mature solution for acid and alkali mist exhaust gas treatment. Its main features are as follows.

Alkali neutralization absorption with high purification efficiency for various acid mists
PP or PPs tower body, corrosion-resistant to acids and alkalis for long service life
Countercurrent packing contact for thorough gas-liquid exchange and stable absorption performance
Low noise and low power consumption, low operating cost, compact size
Demister plate dewatering for minimal liquid carryover in the outlet gas
Detachable structure with complete inspection doors and manholes for easy maintenance
Optional automatic pH chemical dosing for stable unattended operation

Material of tower body	PP / PPs sheets
Purification Principle	Alkali Spray Absorption Neutralization
Gas-Liquid Contact	Filler bed counter-current
Object Processing	Acid and Alkali Mists, Water-Soluble Gases
Defogging Method	Dehumidifying Plate Drying
Recirculation Mode	Bottom Tank Circulation
Chemical Dosing Control	pH Automatic Dosing Optional
Corrosion resistance performance	Acid and Alkali Salt Resistance
Structural Features	Easy to disassemble and repair
Specifications and Features	Non-standard design based on airflow

Application Industries

Acid mist treatment for hydrochloric acid and sulfuric acid pickling tanks in electroplating production lines
Acid mist purification in metallurgical and stainless steel pickling workshops
Hydrogen chloride and hydrogen fluoride tail gas absorption in chemical enterprises
Acid-base exhaust gas washing and purification in semiconductor and photovoltaic factories
Acid mist treatment for surface treatment and anodizing processes
Acid-base fume washing in laboratory and testing institution ventilation hoods
Acid-containing exhaust gas treatment for batteries, electronic etching, etc.

Typical Process Locations

The acid mist purification tower is installed in the exhaust system of pollution-emitting points such as pickling tanks and electroplating lines. The acid mist collected by the hood enters the lower inlet of the purification tower through ducts. Inside the tower, the acid mist rises from bottom to top through the packing layer and spray layer, where it is washed by alkaline solution. The purified gas is demisted and then discharged through the top or side outlet of the tower into a corrosion-resistant fan, before being emitted to the atmosphere via an exhaust stack. The circulating pump and chemical dosing device are arranged around the tower body, with the bottom water tank connected to the water replenishment, wastewater discharge, and wastewater treatment systems. The fan is generally installed after the purification tower to maintain negative pressure in the tower and pipelines, preventing acid mist leakage.

During installation, the tower body is vertically fixed on a concrete foundation, with horizontal and vertical alignment meeting requirements. Flexible connections are installed at the duct inlet and outlet. The weight of the tower body and liquid is borne by the foundation. Before operation, the alkaline solution of the specified concentration is prepared, and inspections are conducted to ensure uniform nozzle spray, properly filled packing, and correctly positioned demisting plates. Water pumps should be turned on before fans, and fans should be turned off before water pumps during shutdown. During operation, alkaline solution is replenished according to pH indicators, water is replaced and discharged regularly, and pollutant concentrations at the inlet and outlet are monitored to ensure the absorption liquid concentration and spray volume remain within the design range.

Mainly treats acid mists and water-soluble gases that can be absorbed by water or alkaline solutions, such as hydrogen chloride, sulfuric acid mist, nitric acid mist, hydrogen fluoride, chromic acid mist, hydrogen cyanide, hydrogen sulfide, and other acidic gases, using alkaline solutions like sodium hydroxide for absorption; alkaline gases such as ammonia are treated with acidic absorbing solutions. It is not suitable for treating water-insoluble organic exhaust gases (e.g., benzene derivatives, esters, VOCs), which require processes such as activated carbon adsorption and catalytic combustion. When multiple pollutants are present, their solubility and reaction characteristics must be analyzed separately. Multi-stage, multi-process combinations may be necessary if required, with specific configurations determined by exhaust gas composition testing and process design.

Common reasons include: insufficient circulating caustic soda concentration or long-term non-replacement, leading to saturated absorption capacity; insufficient spray volume, nozzle blockage, or uneven spraying, resulting in dry zones in the packing layer; packing blockage, crystallization, or scaling reducing gas-liquid contact area; airflow exceeding design value, high gas velocity, or insufficient contact time; abnormal demisting and wastewater discharge. Regularly test the circulating liquid's pH and density, promptly replenish alkali and replace water, clean and clear nozzles and packing, and verify if the actual airflow exceeds the design. When the single-stage tower is insufficient for high-concentration exhaust gas, increase the number of spray stages or use two-stage towers in series. Do not rely on indefinitely increasing alkali concentration as a solution.

No fixed cycle; it depends on the acid mist generation volume and the saturation level of the circulating liquid. In engineering practice, pH meters and salt concentration (density) are used for control: when the pH drops below the set lower limit, alkaline reagents are automatically added. When the salt concentration in the circulating liquid becomes excessively high, absorption efficiency decreases, or the discharge standard is reached, some or all of the circulating liquid is discharged and replaced with fresh water and fresh alkaline reagents. It is recommended to configure automatic pH dosing and regular discharge systems. Wastewater must be sent to a wastewater treatment facility and cannot be discharged directly. For manual management, pH and liquid level should be tested by shift, and records for reagent dosing and water replacement should be established to avoid long-term liquid replacement based on subjective judgment.

Moisture or white mist discharge may be caused by clogged, damaged, or improperly installed demisting plates, where liquid droplets cannot be effectively separated as air flows through the demisting layer; alternatively, it could result from excessively high gas velocity within the tower or excessive spray volume, carrying liquid droplets out of the tower. In winter, steam condensation can also form visible white mist. Inspect, clean, or replace the demisting plates, control airflow and gas velocity within the design range, adjust spray volume, and increase the demisting section or add a secondary demisting stage if necessary. Water carryover can corrode fans and ducts and cause water dripping from the exhaust stack, requiring prompt treatment upon detection.

Salts generated by acid-base neutralization crystallize on the packing surface, combined with dust accumulation, which increases the resistance of the packing layer, reduces airflow, and decreases purification efficiency. Preventive measures include: enhancing dust control in the front-end hood and ductwork, maintaining clean and filtered circulating water, controlling circulating liquid concentration to avoid supersaturated crystallization, and regularly flushing the packing layer with large amounts of water. If blockage occurs, shut down the equipment and enter through the maintenance door to flush the packing with high-pressure water. Soluble crystallization can be cleaned by circulating appropriate dilute acid or dilute alkali (material and waste liquid treatment must be verified), while severely hardened or broken packing should be removed and replaced, along with cleaning accumulated deposits in the grating and water tank.

Need to provide the types and concentrations of main exhaust pollutants, treatment air volume, exhaust temperature, and humidity/dust conditions, required purification efficiency and emission standards, installation location (indoor or outdoor), and available space, as well as absorption liquid and wastewater treatment conditions. The pollutant types determine the absorption liquid formulation and tower materials, air volume determines the tower diameter, and concentrations and efficiency determine the number of packing layers, spray stages, and tower height. Providing these parameters allows the manufacturer to select the appropriate model and ensure compliance. Basing quotes solely on air volume and tower diameter without verifying pollutant composition can easily result in mismatched treatment capacity.

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