Influence of variation in combustion conditions on the primary formation of chlorinated organic micropollutants during municipal solid waste combustion

The aim of this study was to investigate the influence of Variation in comb ustion conditions on the primary formation of organic micropollutants (OMPs ). The flue gas samples were taken at a relatively high flue gas temperatur e (650 degrees C), to enable mechanistic studies on the high temperature fo rmation (primary formation). Eleven experiments were performed in a laborat ory scale fluidized bed reactor fed with an artificial municipal solid wast e (MSW). The samples were analyzed for mono- to octachlorinated dibenzo-p-d ioxins and dibenzofurans (CDDs/Fs), tri- to decachlorinated biphenyls (CBs) , di- to hexachlorinated benzenes (CBzs), and di- to pentachlorinated pheno ls (CPhs). In addition to chlorinated OMPs, nonchlorinated dibenzo-p-dioxin (DD), dibenzofuran (DF), and biphenyl (BP) were analyzed. The experiments show that Variations in the CE influence the degree of chlorination of the organic micropollutants. A correlation between low CE and formation of non- and low-chlorinated OMPs was seen and a distinct relationship of higher ch lorinated homologues and efficient combustion condition. Thus, the DiCDFs a nd DiCBzs are formed during low combustion efficiency (CE), while the PeCDF and PeCBzs formation take place at higher CE. The distribution between pri mary and secondary air is important for the formation of higher CDD/Fs and CBzs. The primary formation of CDDs and CDFs is through different mechanism s. The CDDs are mainly formed by condensation of CPhs, while the CDFs are f ormed through a non- or a low-chlorinated precursor followed by further chl orination reactions.