Flue gas treatment is a process that aims to reduce the emissions of harmful pollutants from the exhaust gases produced by industrial facilities, power plants, and other combustion processes. The treatment of flue gas is essential to mitigate the environmental and health impacts of air pollution. Various technologies and methods are employed in flue gas treatment, depending on the specific pollutants to be removed. 

General overview of the flue gas treatment process:

• Particulate Matter Removal: Particulate matter consists of tiny solid or liquid particles suspended in the flue gas. These particles can include dust, ash, and soot. Particulate matter removal is typically achieved using devices like electrostatic precipitators, fabric filters (baghouses), or cyclone separators. These devices use electrical charges, filters, or centrifugal forces to capture and remove particulates from the flue gas.

• Sulfur Dioxide (SO2) Removal: Sulfur dioxide is a major contributor to acid rain and respiratory problems. Flue gas desulfurization (FGD) is a common process used to remove SO2. One widely used FGD method is wet scrubber, where a chemical absorbent (e.g., limestone or lime) is used to react with and capture SO2 from the flue gas. The resulting products are often called "scrubber slurry" and can be further processed.

• Nitrogen Oxides (NOx) Reduction: Nitrogen oxides are a group of pollutants that contribute to smog and respiratory issues. Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are two common methods to reduce NOx emissions. SCR uses a catalyst and ammonia or urea to convert NOx into nitrogen and water, while SNCR injects ammonia or urea directly into the flue gas to chemically reduce NOx.

• Carbon Monoxide (CO) and Volatile Organic Compounds (VOCs) Removal: CO and VOCs are often removed using combustion control technologies to ensure efficient and complete combustion. This can involve optimizing burner designs and adjusting combustion conditions to minimize the production of these pollutants.

• Mercury Removal: Mercury is a toxic heavy metal that can be present in flue gas emissions. Various methods, such as activated carbon injection or sorbent injection, are used to capture and remove mercury from the flue gas.

• Particulate Matter and Heavy Metal Capture: In addition to the removal of particulate matter, some heavy metals may be present in the flue gas. Specialized technologies, like activated carbon injection or dry sorbent injection, can be used to capture heavy metals and other trace pollutants.

• Gas Cooling: Flue gas is often cooled before treatment to improve the efficiency of pollutant removal processes. This can involve the use of heat exchangers or direct contact cooling towers.

• Stack Emission Monitoring: Continuous monitoring of stack emissions is crucial to ensure that the treatment processes are effective and that emissions remain within regulatory limits. Analytical instruments measure the concentration of pollutants in the flue gas.

• Waste Management: The captured pollutants, such as scrubber slurry or solid residues from baghouses, need proper management and disposal, often following environmental regulations.

Flue gas treatment processes can vary significantly depending on the type of industrial process, the specific pollutants involved, and regulatory requirements. The goal is to reduce emissions to comply with environmental regulations and minimize the environmental and health impacts of industrial activities.

Where are flue gas scrubbers mainly used?

• Coal-Fired Power Plants: Coal combustion is a major source of sulfur dioxide emissions. Flue gas scrubbers are commonly used in coal-fired power plants to remove sulfur dioxide from the flue gases, thereby reducing air pollution and complying with emissions regulations.

• Oil-Fired Power Plants: Oil-fired power plants also produce sulfur dioxide emissions. Flue gas scrubbers can be installed in these facilities to reduce SO2 emissions and meet environmental requirements.

• Natural Gas Power Plants: While natural gas is a cleaner-burning fuel compared to coal and oil, some natural gas sources may contain sulfur compounds. In such cases, flue gas scrubbers can be used to remove sulfur dioxide from the flue gas stream.

• Industrial Processes: Various industrial processes, such as those in the chemical, pulp and paper, and metal smelting industries, may generate flue gases containing sulfur dioxide or other pollutants. Flue gas scrubbers can be employed to control emissions and comply with regulatory standards.

• Waste Incineration Plants: Waste incineration facilities generate flue gases that can contain pollutants like sulfur dioxide, hydrogen chloride (HCl), and heavy metals. Flue gas scrubbers are used to capture these pollutants and prevent their release into the environment.

• Cement Kilns: Cement manufacturing involves high-temperature processes that can produce flue gases with sulfur dioxide emissions. Flue gas scrubbers can be used to reduce these emissions and minimize the environmental impact of cement production.

• Refineries: Oil refineries produce various emissions, including sulfur dioxide, as part of their operations. Flue gas scrubbers may be installed in refineries to control SO2 emissions and meet regulatory requirements.

• Biomass and Waste-to-Energy Plants: Biomass and waste-to-energy power plants utilize organic materials or municipal solid waste as fuel sources. Flue gas scrubbers can be used to control emissions, including acidic gases and particulate matter, from these facilities.

• Marine Vessels: Some ships and vessels are equipped with flue gas scrubbers to reduce sulfur emissions from the combustion of heavy fuel oil, helping them comply with international sulfur emissions regulations, such as the International Maritime Organization's (IMO) sulfur cap.

Flue gas scrubbers are a crucial technology for reducing the environmental impact of combustion processes in these applications. They work by chemically reacting with sulfur dioxide and other acidic gases in the flue gas, converting them into less harmful substances or capturing them for proper disposal. The choice to install flue gas scrubbers often depends on regulatory requirements, fuel types, and the environmental goals of the facility or industry.