Enhanced Formation of Chlorinated PICs bythe Addition of Bromine

A systematic series of experiments were performed on a pilot-scale rotary kiln incinerator simulator in which liquid surrogate wastes containing varied levels of chlorine and bromine were burned. The surrogate wastes used were a series of mixtures of methylene chloride and methylene bromide. The two primary independent variables of interest were the molar halogen input rate and the bromine/chlorine ratio. These tests were prompted by observations made on a previous study on the same facility where an increase in feed bromine concentration resulted in a dramatic increase in emissions of chlorinated products of incomplete combustion (PICs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs). However, these previous observations were made on a single outlying test point where the bromine content of the feed was inadvertently increased, and no verification or duplication of this phenomenon was made at the time. The purpose of the present study was to evaluate, in a more controlled manner, whether the presence of bromine can impact emissions, particularly chlorinated species, some of which are suspected precursors of PCDDs/PCDFs. During these tests, 19 different volatile organic PICs were measured using on-line gas chromatography. The emissions of the volatile organic PICs and carbon monoxide were then correlated against the molar halogen input rate and the bromine/chlorine ratio. It was found that certain volatile organic PICs, such as carbon tetrachloride, are decreased by the addition of bromine, but others, including tetrachloroethylene, are dramatically increased by the addition of bromine. Also, the addition of bromine significantly increased the total number of PICs formed.