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a Abstract This study attempts to clarify the effects of chlorine content in waste on the formation mechanisms of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDyFs) in full scale incinerators by proposing and using the principal component analysis (PCA) to compare the congener profiles of PCDDyFs in the stack flue gases of 17 emission sources, including incinerators and vehicles. Four incinerators, among these 17 emission sources, were sampled and analyzed in this study, and the data for the other 13 emission sources were selected from previous studies. These 17 emission sources can be classified into four categories, including medical waste incinerators (MWIs, H1-H5), municipal solid waste incinerators (MSWIs, M1-M8), vehicle fuel combustion (unleaded gas-fueled vehicles, UGFV; diesel-fueled vehicles, DFV, ns2) and polyvinylchloride (PVC) facility vent combustors (PVC1 and PVC2, ns2). PCA was conducted for these emission sources with the fractions of 17 2,3,7,8-congeners in the stack flue gases as variables to clarify the effect of chlorine content in feeding wastes on the emission of PCDD yFs. From the results of PCA, we extrapolated that the threshold value of the chlorine content was at 0.8-1.1%, and the formation mechanisms of PCDDyFs are influenced first by whether the chlorine content in the feeding waste is over or below the threshold value then by other factors, which furnaces or APCDs represent. When the chlorine level in the waste is below the threshold value at 0.8-1.1%, the formation of PCDDs dominates, probably because the chlorine is used to chlorinate the non-substituted phenol to produce chlorophenols, which are important precursors for PCDDs. rather than chlorinate the dibenzofuran. While the chlorine level in the waste exceeds this threshold (0.8-1.1%), the rates of formation of PCDFs increase faster than those of PCDDs, probably because the chlorine content in the waste contributes to the deterioration of combustion conditions, and many products of incomplete combustion (PICs) like PAHs, will grow to a substantial level. When PCDDyFs are formed from PAHs, the formation rates of PCDFs are higher than those of PCDDs. 2002 Elsevier Science B.V. All rights reserved.

Catalytic incineration was one of the cost-effective technologies to solve the troublesome VOCs. However, some sulfur containing VOCs, such as dimethyl disulfide, may deactivate the Pt catalyst that was commonly used in the catalytic incineration process. This article provides information on the poisoning effect of dimethyl disulfide. The catalytic incineration of dimethyl disulfide and ethanol, typically emitted from the petrochemical industry, over a Pt/Al 2 O 3 fixed bed catalytic reactor were studied. The effects of operating parameters including inlet temperature, space velocity, VOCs concentration, O 2 concentration and catalyst size were characterized. Catalytic incineration on a mixture of dimethyl disulfide and ethanol was also tested. The results show that the conversions of C 2 H 5 OH and (CH 3 )S 2 increase as the inlet temperature increases and the space velocity decreases. The higher the C 2 H 5 OH concentration is, the higher its conversion is. However, the reverse is true for the case of (CH 3 ) 2 S 2 . The O 2 concentration has no effects on the conversion of C 2 H 5 OH but has a positive effect on the conversion of (CH 3 ) 2 S 2 . (CH 3 ) 2 S 2 has a poisoning effect on the Pt/Al 2 O 3 catalyst, especially at a lower temperature. The conversion of C 2 H 5 OH is significantly suppressed by the existence of (CH 3 ) 2 S 2 at a temperature lower than 300°C.