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7Le Relntionahip Betweea Chlorine N Wale Streams and Dioxin Emissions from Wade Comfwator Stacka <br />EXECUTIVE SUMMARY <br />MAJOR FINDING <br />The hypothesis that fuel chlotine content and combustor flue gas PCDD/F' concentrations are <br />related was not confirmed by the data analyzed in this study. <br />Of the more than 1900 PCDD/F test results collected at 169 facilities in the database, PCDD/F <br />and chlorine are simultaneously characterized at 107 units in 90 facilities. Seventy-two facili- <br />ties (80:b) showed no statistically significant relationship between chlorine input and PCDD/F <br />measured in the gas sveams. For the data sets with an apparent relationship, ten displayed <br />increasing PCDD/F concentrations with increasing chlorine, while eight demonstrated a de- <br />crease. <br />The failure to find simultaneous increases in most cases and finding a few inverse relation- <br />ships, indicates that whatever effect waste feed chlorine has on PCDD/F concentrations in <br />combustor flue gases, it is smaller than the influence of other causative factors. Any effect <br />chlorine has on PCDD/F concentrations in commercial scale systems is masked by the effect <br />of air pollution control system [APCS] temperature, ash chemistry, combustion conditions, <br />measurement imprecision, and localized flow stratification. <br />The hypothesis that the amount or type of chlorine in the waste fed to combustion units is di- <br />redly related to gaseous PCDD/F concentrations measured at the combustor outlet, part way <br />through the air pollution control system or at the stack is not supported by the preponderance <br />of the data examined by this study. <br />Background <br />Combustion systems burning generally low chlorine fossil fuels usually exhibit low PCDD/F <br />concentrations. In contrast, waste combustion systems burning hazardous or municipal wastes, <br />which can have much higher chlorine contents, frequently exhibit higher PCDD/F concentra- <br />Lions. These observations have led some to hypothesize that PCDD/F concentrations are de- <br />termined by fuel chlorine content. Some regulatory agencies, public interest groups and indi- <br />viduals are even calling for limits on the input of chlorinated compounds into combustors. <br />'Also krw"n as +dioxiru"; Ircludes all the chl oriroted dibenzo(p)dioxins and tli benxofuran isomers. <br />1 <br />