Removal of polychlorinated biphenyls by desulfurization and emissions of polychlorinated biphenyls from sintering plants

摘要

The influence of desulfurization on polychlorinated biphenyls (PCBs) from sintering plants was investigated. The concentrations of dioxin-like (dl) PCBs, toxic equivalents (TEQs), indicator PCBs, and total tri- to deca-chlorinated PCB homolog groups (aPCBs) in the flue gases at the desulfurization system inlets were 290-1906 pg m(-3) (2.4-18.8 pg World Health Organization (WHO) TEQ m(-3)), 420-2885 pg m(-3), and 6496-22,648 pg m(-3), respectively. Desulfurization reduced the values to 43.3-500 pg m(-3) (0.46-9.5 pg WHO-TEQ m(-3)), 183-587 pg m(-3), and 2383-11,639 pg m(-3), respectively. The removed PCBs were adsorbed by gypsum from the flue gas; the PCB concentration distributions at the inlets and outlets and in the gypsum samples were similar. The emission factors were 9.86 ng WHO-TEQ t(-1) for the flue gas and 8.37 ng WHO-TEQ t(-1) for gypsum. Desulfurization decreased the annual atmospheric PCB emissions from 48.6 to 30.7 g WHO-TEQ, and the estimated annual emissions in gypsum were 8.06 g WHO-TEQ. PCBs in the gypsum have not been effectively eliminated and will probably reenter the environment and in turn become a new source of PCB emission. The PCB concentrations in fly ashes from series-connected electrostatic precipitators clearly increased.