Monochlorinated to Octachlorinated Polychlorinated Dibenzo‑p‑dioxin and Dibenzofuran Emissions in Sintering Fly Ash from Multiple-field Electrostatic Precipitators.

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) emissions in fly ash from multiple-field electrostatic precipitators in different sized sintering plants were studied. The monochlorinated-trichlorinated and tetrachlorinated-octachlorinated PCDD/F concentrations were higher for small plants (90 m2) than for medium (91-180 m2) and large (>180 m2) plants. The PCDD/F concentrations and less-chlorinated PCDD/F contributions to the total PCDD/F concentrations increased as the fly ash particle size decreased moving through the precipitator stages; the abundance of monochlorinated-trichlorinated PCDD/F congeners and homologues also increased. The ash particle size and surface area can be directly used to indicate monochlorinated-trichlorinated PCDD/Fs and toxic equivalents (TEQs). Previously ignored PCDD/F emissions in discarded fly ash were identified. Estimated total monochlorinated-trichlorinated PCDD/F and TEQ emissions in discarded fly ash were 155 kg and 1.979 kg TEQ, respectively, in 2003-2014, and the ratio between annual PCDD/F emissions in discarded fly ash and flue gases has gradually increased. Reductions in monochlorinated-trichlorinated PCDD/F emitted in flue gas and fly ash in 2003-2014 were 28 and 40 kg, respectively, because of the phasing out of small-scale plants. Reductions in TEQs emitted in flue gas and fly ash in 2003-2014 were 7476 and 180 g TEQ, respectively.