Suppression of dioxins in waste incinerator emissions by recirculating SO2

•A pilot-scale system was built for reducing dioxins from a waste incinerator.•Dioxins were inhibited by SO2 circulation in the system.•Dioxins were further degraded by thermal treatment (400 °C) in the system.•The reduction efficiency of dioxins reached 94%.

Sulphur is an effective inhibitor of the formation of Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD/Fs), as was proven in laboratory and pilot plant studies. In this study, a pilot-scale system with capacity 300 N m3 h−1 was situated at the bypass of an actual hazardous waste incinerator (HWI) and tested to reduce the emission of PCDD/Fs. Activated carbon was used as a medium to adsorb SO2 from flue gas and release it again at the higher temperature of filtered ash detoxification to achieve SO2 circulation in the system. Most PCDD/Fs in the filtered ash are decomposed by thermal treatment. Experimental results indicate that the system is capable of stable operation with SO2 accumulation at a high level of concentration and a high reduction efficiency of PCDD/Fs. A reduction of more than 80% was already achieved without addition of other sulphur compounds. When pyrite (FeS2) was added the reduction of PCDD/Fs could reach 94%, with a residual PCDD/Fs concentration in the flue gas as low as 0.13 ng TEQ N m−3. This SO2 recirculating and suppression technology potentially provides significant progress for dioxin emission control in waste incineration and could be useful for controlling emissions of PCDD/Fs and other chlorinated organic chemicals in China.