EFFECT OF GASEOUS INHIBITORS ON PCDD F FORMATION/

Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofura ns (PCD Fs) from municipal waste in cine ration are currently a subjec t of considerable public concern because of their extreme toxicity. PC DD/F formation in incineration processes is being studied widely, but studies on inhibition are quite sparse, especially in a pilot-plant sc ale. In this work, the effect of four gaseous inhibitors (sulfur dioxi de, ammonia, dimethylamine, and methyl mercaptan) on PCDD/PCDF formati on in the combustion of liquid fuel was studied using a pilot-scale pl ant. The inhibitors were injected into the flue gas stream after the f irst economizer at a temperature of 670 degrees C and just before the second economizer at 410 degrees C. Both the chlorophenol and PCDD and PCDF concentrations decreased when inhibitors were added. Particle-ph ase PCDD/F concentrations in particular decreased by up to 98%. The re sults suggest that the formation of PCDD/Fs is hindered in the particl e phase at the early stages of the PCDD/F formation chain, probably ev en before precursors such as chlorophenols have been formed.