Verification of dioxin formation in a catalytic oxidizer.

Emissions and inlet concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) have been measured from a catalytic oxidizer and a thermal oxidizer. The catalyst inlet temperature was 427 degrees C. The thermal oxidizer operating temperature was 791 degrees C. Data of the toxic dioxin and furan congeners are reported. Important results of this field study are: (1) the catalytic oxidizer in this study produced an increase in PCDD/PCDF congener concentration of almost 10-fold from the inlet to the outlet (stack), thus verifying results of a previous study that evaluated only PCDD/PCDF emissions. All congeners increased from inlet to the stack. (2) The thermal oxidizer had little effect on PCDD/PCDF levels. There was a decrease in four of the congeners and an increase in 13 congeners. (3) Ambient air was the main source of PCDD/PCDFs in the stack emissions of the thermal oxidizer in this study. Laboratory investigations are needed to understand how PCDD/PCDFs are formed (and emitted) under conditions of this study.