Impact of Integrating Flameless Combustion Technology and Sludge–Fly Ash Recirculation on PCDE Emissions in Hazardous Waste Thermal Treatment Systems

Abstract

Polychlorinated diphenyl ethers (PCDEs), persistent environmental pollutants, are found in flue gas from incinerators. While air pollution control systems (APCSs) capture pollutants, the resulting sludge/fly ash (SFA) requires further treatment due to residual PCDEs and other harmful substances. This study investigated a hazardous waste thermal treatment system (HAWTTS) utilizing flameless combustion technology alongside a multistage APCS (scrubbers, cyclone demisters, bag houses). SFA from the APCS was recirculated for secondary combustion. PCDE levels were measured before and after each unit within the HAWTTS. The HAWTTS achieved a remarkable overall PCDE removal efficiency of 99%. However, the incinerator alone was less effective for low-chlorine PCDEs. Scrubbers and bag houses exhibited lower removal efficiencies (17.8% and 30.9%, respectively) due to the memory effect. Conversely, the cyclone demister achieved a high removal rate (98.2%). Following complete APCS treatment, PCDE emissions were significantly reduced to 1.02 ng/Nm3. While SFA still contained some PCDEs, the flameless combustion’s uniform temperature distribution enhanced combustion efficiency, minimizing overall PCDE emissions. This system demonstrates significant potential for mitigating PCDE pollution from incinerators. Further research could focus on optimizing treatment processes to address residual PCDEs in SFA.