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AN ISOMER PREDICTION MODEL FOR PCNS, PCDD/FS, AND PCBS FROM MUNICIPAL WASTE INCINERATORS
Citation:
Iino**, F, K. Tsuchiya, T. Imagawa, AND B K. Gullett*. AN ISOMER PREDICTION MODEL FOR PCNS, PCDD/FS, AND PCBS FROM MUNICIPAL WASTE INCINERATORS. ENVIRONMENTAL SCIENCE & TECHNOLOGY 35(15):3175-3181, (2001).
Description:
Isomer patterns of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated biphenyls (PCBs) from municipal waste incinerators (MWIs) were predicted by a model based on dechlorination kinetics from the most-chlorinated species. Successful prediction of PCN isomer patterns indicates that the formation mechanisms of PCNs in emissions from stoker type incinertors are controlled mainly by dechlorination. It is assumed for the prediction that the position-specific dechlorination probabilities from the parent octachloro-naphthalene (OcCN) to the heptachloro-naphthalene (HpCN) isomers, obtained from the HpCN relative chromatogram peak ratios of a representative MWI sample, can subsequently predict the relative concentrations of lower chlorinated isomers such as hexa-, penta-, and tetrachloro-naphthalenes (HxCN, PeCN, and TeCN, respectively). Fly ash isomer patterns from five stoker type and seven fluidized bed incinerators were compared to validate the prediction model. The relative equilibrium concentrations of TeCNs at 298.15, 573, and 1072K, based on Gibbs free energy of formation (AGfdegreesT) values, were calculated by an ab initio method. The relative equilibrium concentrations did not fit well to the TeCN field isomer patterns. A combination of dechlorination and 2,4,6-trichlorophenol condensation mechanism seems to explain the PCDD isomer pattern from MWIs. No conclusions could be drawn for PCBs due to the similar predicted results by chlorination and dechlorination.