Wet Electrostatic Precipitator (WESP) A Wet Electrostatic Precipitator (WESP) is an advanced air pollution control device designed to remove fine particulate matter, aerosols, and mist from industrial exhaust gases. Unlike dry electrostatic precipitators, WESPs utilize a liquid (typically water) to collect and flush away captured particles, making them highly effective for handling sticky, corrosive, or high-resistivity dusts, as well as condensable vapors. Working Principle The WESP operates on the same fundamental principles as a dry ESP but incorporates a wet collection surface. The process involves three key stages: 1. Charging: The contaminated gas stream passes through an ionization section, where high-voltage electrodes (discharge electrodes) emit a corona discharge, imparting a negative charge to particles and droplets. 2. Collection: The charged particles are attracted to grounded collection surfaces (plates or tubes), which are continuously irrigated with water or another liquid to prevent re-entrainment. 3. Flushing: A thin film of liquid washes the collected particles off the surfaces, carrying them away for treatment or disposal. Key Advantages - High Efficiency: WESPs can achieve removal efficiencies exceeding 99% for submicron particles, including PM2.5 and finer aerosols. - Corrosion Resistance: The wet environment minimizes corrosion risks when handling acidic or alkaline gases, especially when constructed with corrosion-resistant materials like fiberglass-reinforced plastic (FRP) or specialized alloys. - No Re-entrainment: Unlike dry ESPs, WESPs eliminate dust buildup and reduce the risk of particles being blown back into the gas stream. - Versatility: Effective for sticky or hygroscopic materials (e.g., tar, sulfuric acid mist) that would clog dry systems. Applications WESPs are widely used in industries with challenging emissions, including: - Chemical Processing: Removal of acid mists (e.g., H2SO4, HCl) and organic vapors. - Metallurgy: Capture of metal fumes and oxides. - Power Plants: Control of fine particulate matter and condensable emissions. - Waste Incineration: Treatment of flue gases containing heavy metals and dioxins. Design Considerations - Materials: FRP, polypropylene, or stainless steel are common to resist chemical attack. - Water Management: Requires a recirculation system with filtration to minimize water usage. - Energy Consumption: Higher power demand than dry ESPs due to water pumping and mist elimination. Challenges - Maintenance: Nozzles and collection surfaces may require frequent cleaning. - Water Treatment: Disposal of contaminated wash water must comply with environmental regulations. Conclusion WESPs offer a robust solution for industries requiring high-efficiency particulate and mist removal, particularly where dry methods fail. Their ability to handle complex emissions makes them indispensable in modern air pollution control systems.