title: Effect of injection of di- and tricyclic aromatic compounds on post-combustion formation of polychlorinated dibenzo-p-dioxins and dibenzofurans.
abstract: The formation of mono- to octachlorinated dibenzo-p-dioxins (PC₁₋₈DD) and dibenzofurans (PC₁₋₈DF) was studied using a model waste in a laboratory-scale combustion reactor with simultaneous collection of flue gas at three different temperatures (450 °C, 300 °C, and 200 °C) in the post-combustion zone. To investigate the influence of chlorination reactions and the effects of carbon backbone-containing compounds present in the flue gases, five aromatic compounds were injected into the flue gas, namely dibenzofuran (DF), biphenyl (BP), naphthalene, phenanthrene and fluorene. The injection of DF induced a reduction in the concentration of PC₃₋₅DD, but did not significantly influence the concentration of PCDF. A reduction in the concentration of PC₃₋₅DD was also observed during the injection of fluorene, which is structurally very similar to DF. The injection of biphenyl, naphthalene and phenanthrene had less pronounced effects on the formation of PCDD and PCDF. A possible explanation of the observed changes during injection of DF and fluorene, based on homologue profiles and affected congeners, involves formation of radical species from fluorene and/or dibenzofuran. The fluorene radical is stabilized by the delocalization of electrons across the aromatic ring structure and has the propensity to react with highly abundant hydrogen chloride, whereas the molecular species would require reaction with Cl₂ or chlorine radicals.
authors.affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden. stina.jansson@btk.slu.se
authors.forename: Stina
authors.initials: S
authors.lastname: Jansson
authors.forename: Jerker
authors.initials: J
authors.lastname: Fick
authors.forename: Mats
authors.initials: M
authors.lastname: Tysklind
mesh_terms: D000393:Air Pollutants / Q000138:chemical synthesis*; D000397:Air Pollution / Q000517:prevention & control; D001572:Benzofurans / Q000138:chemical synthesis*; D001713:Biphenyl Compounds / Q000737:chemistry; D000072338:Dibenzofurans, Polychlorinated; D017745:Incineration / Q000379:methods*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D001713:Biphenyl Compounds; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins; D011084:Polycyclic Aromatic Hydrocarbons; C010574:biphenyl