CLEANUP OF DIOXINS-CONTAMINATED SEDIMENT BY INDIRECT HEATING TREATMENT

摘要

Sediment contaminated with polychlorinated biphenyls (PCBs)-originated polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was treated by an indirect heating method using a bench scale reactor (BSR) and a pilot plant (PP) to investigate the effects of their operational conditions on removal of PCDD/Fs. In indirect heating treatment (IHT) using BSR at 450℃ under 10%O2/N2, PCDD/Fs were sufficiently removed; however, the exhaust gas contained a significant amount of PCDFs which was twenty seven times higher than that in the sediment sample prior to IHT, thereby confirming the occurrence of unintended PCDFs formation from precursors such as PCBs. In the treatment using PP under the same temperature condition, the elevation of PCDFs in exhaust gas was moderated by 12%. Furthermore, increase of the PP treatment temperature to 650℃ resulted in apparent PCDFs degradation. The obtained results clearly indicate that treatment temperature is a critical parameter for IHT to remedy sediment contaminated with PCBs-originated PCDD/Fs with avoidance of unintended PCDFs formation.