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Wet scrubber system for paint spray room exhaust gas treatment
Wet scrubber system introduction
A wet scrubber system is a type of air pollution control device used to remove pollutants from gas streams by bringing the gas into contact with a liquid. Here is a detailed introduction:
Working Principles
Absorption: Gaseous pollutants in the exhaust gas are dissolved in the scrubbing liquid. For example, acidic gases like sulfur dioxide and hydrogen chloride can be absorbed by alkaline solutions, while water-soluble organic gases can be dissolved in water.
Wetting and Agglomeration: The liquid sprayed in the scrubber wets the particulate matter in the gas. Tiny particles adhere to the liquid droplets and agglomerate into larger particles, which are easier to separate and remove.
Chemical Reaction: In some cases, chemical reactions occur between the pollutants and the components in the scrubbing liquid. For instance, when treating exhaust gases containing ammonia, an acidic scrubbing liquid can be used to react with ammonia to form ammonium salts, thereby removing ammonia from the gas.
Components
Spray Nozzles: These are used to spray the scrubbing liquid into the scrubber chamber in the form of fine droplets, increasing the contact area between the liquid and the gas.
Scrubber Chamber: This is the main body of the wet scrubber system. It provides the space for the gas and liquid to come into contact and interact. The interior of the chamber may be equipped with packing materials or baffles to enhance the contact efficiency between the gas and the liquid.
Liquid Distribution System: It ensures the even distribution of the scrubbing liquid in the scrubber chamber to achieve uniform contact with the gas.
Gas Inlet and Outlet: The gas inlet allows the polluted gas to enter the scrubber system, and the gas outlet discharges the purified gas after treatment.
Liquid Collection and Recycling System: After the scrubbing process, the liquid containing pollutants is collected at the bottom of the scrubber chamber. It is then pumped to a treatment facility for separation and treatment. The treated liquid can be recycled and reused in the scrubber system.
Gas Collection: A well-designed exhaust system in the paint spray room, including hoods and ducts, is used to collect the exhaust gas. This ensures that the exhaust gas containing paint mist and other pollutants is effectively captured and transported to the wet scrubber system for treatment.
Liquid Atomization: In the wet scrubber, the scrubbing liquid (usually water or a special chemical solution) is sprayed into the scrubber chamber through spray nozzles. The nozzles break the liquid into tiny droplets, creating a large surface area for contact with the exhaust gas.
Initial Contact and Adsorption: As the exhaust gas rises or passes through the scrubber chamber, the paint mist particles and some soluble gaseous pollutants in the exhaust gas come into contact with the sprayed liquid droplets. The paint mist particles are adsorbed or adhered to the surface of the liquid droplets due to the wetting effect.
Particle Removal and Agglomeration
Inertial Impaction and Interception: Larger paint mist particles in the exhaust gas are removed by inertial impaction and interception. When the gas flow changes direction or encounters obstacles in the scrubber, the paint mist particles, due to their inertia, continue to move in their original direction and collide with liquid droplets or the inner wall of the scrubber, and are then captured by the liquid.
Brownian Diffusion and Agglomeration: For fine paint mist particles, Brownian motion causes them to collide and agglomerate with liquid droplets or other particles. As the particles agglomerate into larger ones, their settling velocity increases, making it easier to be separated from the gas.
Absorption of Gaseous Pollutants
Solubility-based Absorption: Some gaseous pollutants in the exhaust gas from the paint spray room, such as water-soluble organic solvents and acidic gases, can be dissolved in the scrubbing liquid. The solubility of these pollutants in the liquid enables them to transfer from the gas phase to the liquid phase, thus achieving removal from the exhaust gas.
Chemical Reaction-based Absorption: In some cases, the scrubbing liquid contains chemical substances that can react with specific gaseous pollutants. For example, an alkaline scrubbing liquid can be used to react with acidic gases in the exhaust gas to form harmless or less harmful substances, which are then retained in the liquid.
Separation and Discharge of Treated Gas
Liquid-Gas Separation: After the exhaust gas has passed through the scrubbing and purification process, it enters the liquid-gas separation section of the scrubber. Here, various separation technologies, such as gravity separation, centrifugal separation, or the use of demisters, are used to separate the remaining liquid droplets from the gas.
Purified Gas Discharge: The purified gas, with a significantly reduced content of paint mist and gaseous pollutants, is then discharged into the atmosphere through the outlet of the wet scrubber system. The discharged gas meets the relevant environmental protection emission standards, reducing pollution to the environment.
Treatment and Recycling of Scrubbing Liquid
Settling and Filtration: The scrubbing liquid containing paint mist and dissolved pollutants is collected at the bottom of the scrubber and then flows into a settling tank or filtration device. In the settling tank, the paint mist and other solid particles settle to the bottom under the action of gravity, while filtration devices can further remove fine particles to clarify the liquid.
Chemical Treatment: For the pollutants dissolved in the liquid, chemical treatment methods may be used to further decompose or transform them into harmless substances. For example, chemical oxidation or reduction reactions can be used to treat organic pollutants in the liquid.
Liquid Recycling: After treatment, the scrubbing liquid that meets the requirements can be recycled and pumped back to the spray nozzles in the scrubber for reuse. This not only reduces water consumption but also ensures the continuous and stable operation of the wet scrubber system.
