Rate of hexabromocyclododecane decomposition and production of brominated polycyclic aromatic hydrocarbons during combustion in a pilot-scale incinerator

Here, we examined the incineration of extruded polystyrene containing hexabromocyclododecane（HBCD） in a pilot-scale incinerator under various combustion temperatures（800–950℃） and flue gas residence times（2–8 sec）. Rates of HBCD decomposition ranged from 99.996%（800℃, 2 sec） to 99.9999%（950℃, 8 sec）; the decomposition of HBCD, except during the initial stage of combustion（flue gas residence time 〈 2 sec）, followed a pseudo-first-order kinetics model. An Arrhenius plot revealed that the activation energy and frequency factor of the decomposition of HBCD by combustion were 14.2 kJ/mol and 1.69 sec^（-1）,respectively. During combustion, 11 brominated polycyclic aromatic hydrocarbons（BrPAHs）were detected as unintentional by-products. Of the 11 BrPAHs detected, 2-bromoanthracene and 1-bromopyrene were detected at the highest concentrations. The mutagenic and carcinogenic BrPAHs 1,5-dibromoanthracene and 1-bromopyrene were most frequently detected in the flue gases analyzed. The total concentration of BrPAHs exponentially increased（range,87.8–2,040,000 ng/m^3） with increasing flue gas residence time. Results from a qualitative analysis using gas chromatography/high-resolution mass spectrometry suggest that bromofluorene and bromopyrene（or fluoranthene） congeners were also produced during the combustion.