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Home / Blog / Wet Scrubber for Boiler: Design, Construction, Principle of Operation, Types of Materials

Wet Scrubber for Boiler: Design, Construction, Principle of Operation, Types of Materials

Author: Michael Klepik, Chief Executive Officer

Brief Introduction

A boiler is a technical apparatus designed to convert water into steam or hot water using thermal energy. It plays a pivotal role in heating systems, power generation, and industrial processes. The fundamental operational principle involves converting fuel (commonly coal, oil, or wood) into thermal energy, which is then transferred to a working substance (typically water) to produce steam or hot water.

Specification of Pollutants
  • Soot and Particulate Matter (PM)
  • Sulfur Dioxide (SO2) and Nitrogen Oxides (NOx)
  • Hydrocarbons and Carbon Dioxide (CO2)
  • Toxic Substances and Metals
  • Toxic Substances in Flue Gases
Understanding these pollutant types is crucial for developing effective methods to purify emissions and ensuring compliance with environmental legislation.


The design of a wet scrubber is a critical aspect in the realm of industrial air pollution control.

Tailored specifically for furnaces, the equipment design involves meticulous consideration of various factors. These include air flow rates, temperature profiles, pollutant concentrations, and the desired efficiency of air purification. The primary goal is to create a setup that optimizes the interaction between the gas phase, carrying contaminants, and the liquid phase, typically water or a chemical solution.

The engineering process includes selecting appropriate materials for the components and determining the suitable size and configuration. This careful planning ensures not only efficient pollutant removal but also compliance with environmental regulations governing air quality standards.

Key Construction Elements

Wet scrubber boiler design for cleaning flue exhaust involves several crucial elements.
  • Housing or column apparatus;
  • Inlet pipe (1); Liquid supply pipeline (2);
  • Outlet pipe;
  • Water recirculation tank;
  • Sludge discharge nozzle.
Integrated control mechanisms play a vital role in monitoring and regulating various parameters, including absorbent flow rate, pH levels, and pressure. Drainage structures and waste treatment mechanisms are incorporated to manage the byproducts effectively, ensuring proper waste disposal.

In summary, the design of a boiler scrubber flue exhaust cleaning encompasses the systematic application of physical and chemical processes, control measures, and the use of appropriate materials for optimal efficiency and environmental compliance.
Wet scrubber diagram
Wet scrubber diagram

How Do Boiler Scrubbers Work?

Wet scrubber for a boiler operates through a process known as absorption. Here's a concise explanation of how they work:
  1. Flue gas, laden with pollutants such as sulfur dioxide (SO2) and particulate matter, is directed through the wet unit.
  2. Inside the equipment, a solution absorbent (typically water or a chemical solution) is sprayed or circulated. This liquid comes into direct contact with the contaminants.
  3. The contaminants undergo a chemical reaction with the solution absorbent. For instance, sulfur dioxide can react with water to form sulfurous acid.
  4. The chemical reactions result in the formation of byproducts, which are often less harmful or can be easily disposed of, reducing the environmental impact.
  5. The treated gas, now substantially free of pollutants, is released into the atmosphere. The liquid absorbent may need periodic replenishment or treatment, depending on the level of contamination.
In essence, boiler scrubbers work by utilizing a liquid medium to capture and neutralize contaminants present, leading to cleaner emissions and compliance with environmental regulations.

What Is the Best Method of Cleaning a Boiler?

The ideal method for purifying a heating system involves utilizing a wet scrubber. This method utilizes a solution absorbent to remove contaminants, enhancing overall efficiency and minimizing emissions. The boiler wet scrubber acts as a proficient purification setup by absorbing and dissolving pollutants, resulting in a cleaner and more environmentally friendly combustion process. This technique is widely recognized for its efficacy in maintaining performance while adhering to stringent environmental standards.
The catalytic scrubbers for boiler flue gas are systems designed to purify air by utilizing catalysts to accelerate chemical reactions and efficiently remove harmful substances. Such setups are employed to reduce emissions of nitrogen oxides (NOx), sulfur dioxide (SO2), and other pollutants that can form during combustion. Catalysts activate chemical reactions, facilitating a more effective conversion of harmful substances into less hazardous compounds.

Types of Materials Used

The choice of materials plays a pivotal role in ensuring the effectiveness and longevity of the equipment. From the outer casing that battles harsh environmental conditions to the intricate internals designed for optimal gas-liquid interaction, each component relies on specific materials tailored to combat the challenges posed by contaminants.

Technical Aspects

Tornado ST — Spray Tower Scrubber
Achieving effective air cleaning in a boiler chimney scrubber involves careful consideration of key planning parameters, such as contact time between the gas and solution. The dimensions and configuration of the unit internals significantly influence this vital aspect, ensuring optimal interaction for pollutant removal.

The physical size of the boiler flue gas scrubber depends on the volumetric flow rate of the exhaust stream, the concentration of pollutants, and the desired level of cleaning efficiency.

Contact Time:
The design must ensure an adequate contact time between the airflow and cleansing solution. This is influenced by the dimensions and configuration of the unit internals.

Pump Capacity:
The pump capacity is determined by the liquid flow rate required for effective cleansing, which is influenced by the gas flow rate, pollutant concentration, and the specific technology employed in the water scrubber for boiler.

Fan or Blower:
In certain applications, a fan or blower may be necessary to control the flow and pressure drop across the equipment. The power requirements of these components depend on the system's engineering parameters.

Monitoring and Control Systems:
Implementation of monitoring and control arrangements, including sensors and instrumentation, is essential for optimizing the performance. The power requirements for these setups vary based on complexity and scale.
Comprehensive understanding of the materials employed and sizing considerations is imperative for the successful implementation of a boiler scrubber system across various industrial applications, ensuring efficient and reliable air cleaning.

Flue Gas Purification in Boiler and Power Plants

When solid fuel is burned, a significant amount of harmful impurities is released. Thermal power stations, utilizing hydrocarbons, may employ a basic flue air purification scheme with a wet scrubber. However, coal-fired power plants, especially waste incineration facilities, demand a more sophisticated air pollution control system.

Multi-stage purification in power plants involves mechanical filtration in the initial stage, typically using heat-resistant metallic screens or coarser cyclone dust collectors. The remaining fine particulate matter is directed into a Venturi scrubber with a minimal amount of liquid, aiding in resource conservation for sludge disposal. In Venturi devices, smoke flows through narrow channels, accelerating the movement of dust particles. For highly effective atmospheric emission control, an electrostatic precipitator is installed as the final stage in purification process.

Depending on the fuel composition, the nature of emissions may vary. Purification in boiler systems typically requires regular laboratory analysis. If nitrogen or sulfur compound levels increase, additional modules are integrated into the purification setup, and active additives are introduced into the cleansing solution.
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We always make extremely precise calculations and provide assistance in choosing the optimal cleaning systems, which usually takes 1 to 2 days.
Head of Engineering,
Vladimir Nikulin
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