Understanding and Mitigating Corona Quenching in ESPs Under High Fly Ash Concentrations in a 660 MW Coal-Fired Unit

Corona quenching is a major obstacle to the stable and efficient operation of electrostatic precipitators (ESPs) in coal-fired power plants, particularly under high-ash coal combustion. This study evaluates a novel double-V labyrinth pre-collection device as an active strategy to mitigate corona quenching. Field measurements from a 660 MW ultra-supercritical coal-fired unit, combined with computational fluid dynamics (CFD) simulations, demonstrate that the retrofit significantly improved inlet flow uniformity and reduced fly ash concentration before the ESP. Consequently, corona discharge stability was enhanced, overall collection efficiency increased from 99.42% to 99.92%, and outlet fly ash concentration decreased from 81 mg/m3 to 20.5 mg/m3. Although the pressure drop rose modestly (128 Pa to 187.5 Pa), the overall ESP energy demand was reduced due to more stable operation at lower voltages. These results confirm the technical feasibility and engineering applicability of pre-collection technology, providing a cost-effective solution to overcome corona quenching and ensure ultra-low emission compliance in large coal-fired units.