Waste Incineration Of Dioxin In The Process Of Fly Ash Distribution Characteristics And Preliminary Study Of The Control Technology

Municipal solid waste (MSW) Incineration technology has been a rising technology in China gradually. Controlling technologies of dioxins in MSW incinerator have been pop topics in environmental pollution research all over the world. This study gives synthesis mechanism of precursors, characterization of dioxins in fly ash produced from MSW incinerator and controlling technologies of dioxins, which are the foundation of controlling technologies of dioxins from MSW incineration for the future.Model studies were performed to determine the content and homologue profile of dioxins which produced from PCP, trichlorobenzene and PAH precursors. The effects have been discussed. The pathways of dioxins formation were found.Distribution characteristics of dioxins in fly ash from Bag filters of MSW incinerators were studied. The results showed there was a positive correlation between chlorine content with dioxins levels. Although large amounts of heavy metals were found in fly ash .there were not distinct relationship between dioxins levels and heavy metals. Dioxins in fly ash from grate fired MSW incinerators were formed from precursors and those from fluidized bed incinerators were formed from de novo synthesis.The thermal treatment of fly ash showed it was necessary to take measures to rapidly cool down the exhaust gas to prevent dioxins regeneration. Dioxins in fly ash could be decomposed under the temperature was higher than 1100℃ in an oxidative atmosphere.Ultra-violet photolysis of OCDD and OCDF in different organic solvents were performed by using multi-functional photochemical reactor. The photolysis pathway of OCDD correlated with the polarities of solvents. The major photolysis pathway of OCDD and OCDF in n-hexane are reductive dechlorination.Photolysis rate of OCDD and OCDF in n-hexane fits a first-order kinetics.Different methods were used for decompose dioxins in fly ash by Ultra-violet photolysis.The photolysis rate of dioxins in solutions were higher than those in solid.The addition of TiO2 catalyzed photolysis of dioxins. The photolysis rate correlated to the properties of fly ash particle. TiO2 produced OH radical which has powerful oxidable ability. Dioxins were attacked by OH radical initially and then occurred electrophilic addition reaction. As a result, dioxins were decomposed by photocatalytic degradation.Some suggestions were proposed for the farther research of controlling technologies of dioxins in the end of this paper.