EFFECT OF SULFUR-DIOXIDE ON THE FORMATION MECHANISM OF POLYCHLORINATED DIBENZODIOXIN AND DIBENZOFURAN IN MUNICIPAL WASTE COMBUSTORS

The effect of sulfur dioxide on the formation mechanism of polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran (PCDF) in the postcombustion, downstream region (500-300-degrees-C) of a municipal waste combustor (MWC) was investigated. Laboratory experiments simulating the flue gases and particle environment of an MWC examined PCDD production under varying conditions. Effects on the concentration of an organic-chlorinating constituent, Cl2, through both homogeneous reaction with SO2 and deactivation of a Cl2-forming catalyst [Cu(II)] were examined. Experimental results suggest that the reaction of Cu(II) with SO2 to form CuSO4 renders the catalyst less active, decreasing PCDD formation. However, this inactivity is not a result of decreased Cl2 formation, but rather of reduced ability of Cu(II) to promote a second catalytic step of biaryl synthesis. These findings suggest that the apparent lack of PCDD and PCDF in the emissions from coal-fired combustors may be due to the relatively high concentrations of SO2.