In order to investigate the dioxin emission levels of hazardous waste incinerators (HWIs), and estimate their emission factors to the atmosphere, flue gas samples were collected from 12 HWIs in China, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Eleven HWIs are located in the south-eastern coastal areas of China, with rotary kilns being is the most widely used type of incinerator (more than 50% of the units), followed by pyrolysis kilns. Eleven incinerators had their emission levels below the current standards in China, while only four facilities exhibited emission levels below the European Union's limits. The highest concentration of PCDD/Fs, at nearly 1 ng TEQ/Nm 3 , was in the flue gas collected from an HWI with a waste burning capacity of 5 ton/d. This result was significantly higher than the values found for the other 11 incinerators, and thus was due to the poor performance of air pollution control devices and the influence of memory effects caused by PCDD/Fs emissions related to the start-up of the incinerator. In addition, the high dioxin emissions of this HWI were related to its feeding wastes, which mainly consisted of chemical industry waste residue with high a chlorine content. The emission factors of PCDD/Fs from the HWIs examined in this work were in the range of 0.27-18 µg TEQ/ton hazardous waste, with an average value of 3.74 µg TEQ/ton hazardous waste. It is estimated that 5.0 g TEQ of PCDD/Fs was released from HWIs to the atmosphere in China in 2010, which is less than that seen in 2004. The results of principal component analysis and hierarchical cluster analysis show all the investigated HWIs can be assigned to three groups, as verified by the results of nonparametric statistics. OCDD, 2,3,4,7, 1,2,3,4,7, are the main congeners in these three groups.

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The vortexing effect on reducing pollutant emission was verified via the combustion of three groups of sawdust with different diameters in a vortexing fluidized bed combustor (VFBC). The temperatures and pollutant emission distributions along the combustor were measured simultaneously. The combustion fraction in four zones of the VFBC were also calculated on the basis of the oxygen consumption. Additionally, the effects of operating variables, such as the in-bed stoichiometric oxygen ratio and the excess oxygen ratio, on the pollutant emissions were also investigated. The results show that the combustion fractions in the bed and freeboard zones increase with larger particle sizes. However, an inverse trend occurred in other zones. The CO emissions from the three sawdust combustions decrease with an increase in the particle size, excess oxygen ratio, and inbed stoichiometric oxygen ratio, whereas the NO x emissions exhibit an inverse trend. The vortexing effect, which is caused by secondary air injection, demonstrated its effectiveness in prolonging the residence time of sawdust in the high-temperature zone. However, the lowest value of CO emission is still much higher than the minimal requirements of the Taiwan Environmental Protection Agency regulations. Increasing the particle size or compacting the sawdust into pellets are two possible solutions for decreasing the CO emission.