Environ. Sci. Technol. 2003, 37, 3164-3170
Application of Electron Beam for the Reduction of PCDD/F Emission from Municipal Solid Waste Incinerators KOICHI HIROTA,* TERUYUKI HAKODA, MITSUMASA TAGUCHI, MACHIKO TAKIGAMI, HYONHA KIM, AND TAKUJI KOJIMA Department of Material Development, Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
The electron-beam technology was applied to reduce the emission of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in a flue gas of 1000 m3N/h from the municipal solid waste incinerator (MSWI) at a temperature of 200 °C. More than 90% decomposition of PCDD/Fs was obtained using an electron accelerator at a dose of 14 kGy. The decomposition was initiated through reactions with OH radicals produced by the irradiation of flue gases, followed by oxidation such as the ring cleavage of the aromatic ring, the dissociation of ether bond, and dechlorination. The cost analysis estimated that the electron-beam system can cut the annualized cost by approximately 50% for the treatment of PCDD/Fs in a pre-dusted MSWI flue gas as compared with a bag-filter system when operating on electricity generated from an incineration. Electron-beam technology is an economically and technologically useful method for reducing PCDD/Fs in an incineration flue gas.
Introduction Dioxin is a very toxic chemical that can bind to a hormone receptor and cause a serious problem to the body. Carcinogenicity and mutagenicity are the most notorious effects of dioxin. Dioxin involves polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanner polychlorinated biphenyls (PCBs). The annual emission of dioxin in 2001 was estimated to be approximately 1,750 g-TEQ in Japan, in which the largest contributor of a municipal solid waste incinerator (MSWI) accounted for half of the emission (1). The domestic MSWIs have reduced the dioxin emission to 0.5-5.0 ng-TEQ/m3N by the combination of adsorption with dry activated carbons and precipitation at a temperature below 200 °C under the control of the secondary formation of dioxin. The Government of Japan established new emission standards for dioxin in 1999, in which the existing MSWIs having the incineration capacity over 4 t/h must reduce the emission lower than 1.0 ng-TEQ/ m3N by December 2002 (2). An emission limit of 0.1 ng-TEQ/ m3N was set for newly constructed incinerators. To satisfy the new standards, local governments have been constructing advanced incinerators or replacing dry electric precipitators by bag filters with the repair of furnaces to improve incineration conditions such as turbulence, time, and temperature. There are, however, still strong requests for lower * Corresponding author telephone: +81-27-346-9421; fax: +8127-346-9687; e-mail:
[email protected]. 3164
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 37, NO. 14, 2003
PCDD/F emissions than the new standards (e.g.,
