Technical Solution for Wet Electrostatic Precipitator in Coal-Fired Power Plants

     Technical Solution for Wet Electrostatic Precipitator in Coal-fired Power Plants

      I. Project Background and Objectives

      Flue gas emitted from coal-fired power plants contains a large amount of pollutants such as dust, SO₃ acid mist, heavy metals (e.g., mercury), and PM2.5. Traditional dry electrostatic precipitators struggle to meet ultra-low emission requirements. The Wet Electrostatic Precipitator (WESP) utilizes water film cleaning and a high-voltage electric field to efficiently remove fine particulate matter and aerosols, achieving a dust emission concentration of ≤5 mg/m³ and complying with national and local environmental standards.

      II. Technical Principles

1. Electric Field Charging: A high-voltage power supply (DC or pulse) creates a strong electric field between the anode tubes and cathode wires, charging particles such as dust and mist droplets in the flue gas.
2. Particle Capture: Charged particles migrate to the inner walls of the anode tubes under the influence of the electric field, forming a water film.
3. Water Film Cleaning: Continuous water spray rinses the inner walls of the anode tubes, flushing out dust with the water flow to prevent secondary dust emission.
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      III. System Design

1. Equipment Selection
   • Anode Tubes: Made of conductive fiberglass reinforced plastic or 2205 duplex stainless steel, with specifications including a regular hexagon inscribed circle diameter of 350 mm, tube length of 4500 mm, and wall thickness of 1.5 mm.
   • Cathode Wires: Rigid barbed wires made of 2205 stainless steel, with a wire current density of ≥0.3 mA/m and a corona onset voltage of ≤30 kV.
   • High-Voltage Power Supply: Utilizes a composite pulse power supply with an output voltage of 72-100 kV, current of 1000-3000 mA, and features spark tracking and flashover control functions.
2. Process Flow
   • Flue Gas Inlet: Saturated wet flue gas (temperature ≤50°C) from the desulfurization tower enters from the bottom of the WESP at a flow velocity of ≤3 m/s.
   • Electric Field Zone: Flue gas passes vertically through anode tube bundles (37 tubes per module) with a residence time of ≥5 s.
   • Outlet Purification: Purified flue gas has a dust content of <10 mg/m³, SO₃ removal rate of ≥80%, and droplet emission concentration of ≤15 mg/m³.
3. Auxiliary Systems
   • Spray System: Equipped with 316L stainless steel nozzles, with a single unit’s flushing water flow rate of 1.9 m³/h and water pressure of 0.3-0.5 MPa.
   • Ash Water Treatment: Ash water is neutralized (pH=6-9), settled, and recycled, with a small amount of wastewater discharged to the desulfurization system.
   • Corrosion Protection Design: The main body uses carbon steel lined with glass flake resin, and the insulator box is equipped with a heating device to prevent condensation.