Study On Emission Characteristics And Detection Of PCDD/Fs And Environment Persistent Free Radicals During Solid Waste Disposal

The urbanization of China is historical process inevitablely followed by one of negative impact that municipal slid waste increase dramatically, therefore, Garbage Innocuity Disposalis significantly meaningful. However, the World Bank warned in a report on the city’s solid waste that there exists potential cost of handling an increasing number of garbage, and what’s more, dioxin emission in the process of solid waste disposal and the people’s concernsover risk of exposure to pollutants is the current constraints of spreading the promotion ofincineration technology.Based on this background above, the research was carried outin manyfocused on this coresolid waste incineration, and some valuable statements as following:On study of dioxins and chlorobenzene in flue gas from simulationalgarbage incineration, the key incineration factors including temperature, oxygen content and metal catalysts, have similar effect on the formation of dioxins and chlorobenzene, but with difference in both of them at the same time.Optimal temperature to form chlorobenzene is at about950℃. Oxygen content has an impact onthe formation of chlorobenzene and dioxins. Elemental metal catalysts obviously change the generated amount of dioxins, whilefor CBz there is no significant effect.By extraction technology, envoironmental persistent free radicals (EPFRs) were detectedin the incineration fly ash and different types of persistent free radicals were distinguished from different sources of incineration.These radicals included organic radicals, chlorine free radicals, semi-quinone as well as carbon-centered radicals, and they were associated with metal componentand dioxinsconcentration in fly ash.According to the survey on dioxin emissionsin flue gas from China’s current garbage incinerator and sampling analysis, only60%of MSWI can meet the national standard of dioxin emission (0.1ng I-TEQ/m3). It’s worth noting that the highest concentration of dioxins and chlorobenzene was up to8.12ng I-TEQ/m3and126.71μg/m3, respectively. Hence, government still should strengthen supervision and control in dioxins and chlorobenzene emissions from municipal waste incinerator. Chlorobenzene is good indicator for PCDD/Fs and total I-TEQ concentrations in flue gas, with an indicative correlation coefficient reaches R2>0.8, andthe on-line measurement of dioxinindirectly was achieved by the VOV-TOFMS combined with trichlorobenzene association model.According to the survey on dioxins emissions from national cement production, all of dioxin emissions from normal and co-disposal condition meet the national standard with0.1ng I-TEQ/m3in stack gases. Through calculation in dioxins quality balance of the cement production system, cyclone preheater and heat recovery unit were provedout the main source of dioxin formation.The average dioxin emissionfactor is5.89μg/ton cement, and dioxin emissions in whole cement industry of China is up to10kg I-TEQ/year, accounted for6.51percentage of total emissionaccording to the dioxin emission inventories. The dioxin emissionof cement industry in Chinais relativelow, and there is still room for improvement and optimization.