Evaluation of he characteristics of dioxin decomposition and reformation in reburning-combustor applied purification system for MSW incinerator exhaust gas

摘要

We developed a new gas purification system for MSW incinerators. By reburning the whole exhaust gas from the incinerator, dioxin entrained in the exhaust gas was thermally degraded then the gas was cooled down with a high-speed gas cooler or a heat exchanger to suppress dioxin reformation. In order to verify the system, we carried out fundamental experiments using a basic model and verification experiments in both an MSW and an industrial solid waste incineration plant. Consequently, we verified that the system could reduce the dioxin concentration below the level between 0.1 and 0.01 ng-TEQ/(m{sub}N){sup}3. Furthermore, we revealed the following as technical data for designing the system: (1) Co-presence of fly ashes, HCl and dioxin precursors in the exhaust gas promotes dioxin synthesis and prevents dioxin from being broken down in the high temperature decomposition process, (2) In the cooling process, dioxin reformation depends on the time needed for the exhaust gas to pass through the temperature window (250 to 400°C), and (3) The maximum concentration of dioxin can be roughly estimated according to the concentration of [fly ash] [HCl] [2,4,6-trichlorophenol]{sup}2 in the system using a 0.5 second high-speed gas cooler.