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Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from municipal waste incineration are currently a subject of considerable public concern because of their extreme toxicity. PCDD/F formation in incineration processes is being studied widely, but studies on inhibition are quite sparse, especially in a pilot-plant scale. In this work, the effect of four gaseous inhibitors (sulfur dioxide, ammonia, dimethylamine, and methyl mercaptan) on PCDD/PCDF formation in the combustion of liquid fuel was studied using a pilot-scale plant. The inhibitors were injected into the flue gas stream after the first economizer at a temperature of 670 °C and just before the second economizer at 410 °C. Both the chlorophenol and PCDD and PCDF concentrations decreased when inhibitors were added. Particle-phase PCDD/F concentrations in particular decreased by up to 98%. The results suggest that the formation of PCDD/Fs is hindered in the particle phase at the early stages of the PCDD/F formation chain, probably even before precursors such as chlorophenols have been formed.

Emissions of organic chlorinated compounds from municipal waste incineration, in particular polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), have been a cause of public concern for many years because of the high toxicity of these compounds. PCDD/F formation in incineration processes is being studied widely using labscale apparatus, but pilot-plant investigations are quite rare. The correlation between TEQ-related PCDD/Fs and chlorophenols (ClPhs) was studied here using a pilotscale plant. The results suggest that almost all the ClPh isomers correlate strongly with PCDD/Fs in the gas phase, but only certain isomers, in particular 2,3,4,6-and 2,3,4,5,6-ClPh, are of importance in the particle phase. The relationship of TEQ-related PCDD/Fs to ClPhs is so close that even predictive partial least-squares (PLS) modeling is feasible. In view of our results, some aspects of the mechanism of PCDD/F formation are discussed. From a practical point of view, the results suggest that ClPhs may be a good surrogate of TEQ-related PCDD/Fs in different incineration processes.

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