In this study, characteristics of dioxins emission from existing modern MWIs were evaluated via simultaneous sampling of flue gas and various types of fly ashes. Preliminary results showed that PCDDs congeners distributions were quite similar in flue gas and various types of ashes of both MWIs. PCDFs/PCDDs ratio in cyclone ash was lower than that in combustor ash or fabric filter ash excluding economizer ash of MWI-A. Similarly, PCDFs/PCDDs ratio in ESP ash was lower than that in boiler ash. PCDFs concentration was about 1.5 to 4.3 times higher than PCDDs concentration in flue gas of both MWIs. The mass balance factors of MWI-A (0.9 similar to 1.02) were clearly lower than that of MWI-B (7.71 similar to 15.63), indicating that de novo synthesis occurred under the operating conditions of ESP. In other words, MWIs equipped with ESP were less efficient in controlling PCDD/Fs emissions than that equipped with fabric filters. (C) 1998 Elsevier Science Ltd. All rights reserved.
