Characterization of Dust Characteristics from Sludge Co-combustion in Coal-fired Units and Experimental Study on Retrofit of Pneumatically Rapped ESP
Sludge co-combustion in coal-fired power plants generates flue gas dust with high viscosity, causing severe dust deposition on downstream environmental protection equipment. This study analyzed the dust deposition mechanism in electrostatic precipitators (ESPs) and characterized the dust layer properties. Results indicated that sludge co-combustion increased flue gas moisture content, altered particle morphology, and elevated dust viscosity. To address these issues, an anode pneumatically rapped ESP technology was developed to enhance anode plate cleaning. This technology was retrofitted on a 1000 MW unit at Zhejiang Jiahua Power Plant, and performance tests under sludge co-combustion conditions were completed in February 2025. At a specific dust collection area of 118 m²·s/m³ and a unit load of 987 MW, the ESP outlet dust concentration decreased from 25.32 mg/m³ before retrofit to 7.95 mg/m³ after retrofit. Analysis revealed that sludge co-combustion caused excessive dust deposition on the first electric field anode plates, inducing back corona, high-voltage power supply flashover, and low secondary voltage and current. After retrofit, regions with low rapping acceleration were eliminated, achieving effective dust cleaning. Secondary voltage and current were significantly improved, and overall ESP efficiency was remarkably enhanced. The proposed technology provides a reference for ESP retrofitting of coal-fired units under biomass (sludge) co-combustion and low-load conditions.