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

Abstract

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 m) than for medium (91-180 m) and large (>180 m) 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 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.

Predicting Final PCDD/F Emissions by Coupling Adsorption Model of Activated Carbon and Relationships of PCDD/Fs and Flue Gas Compositions

“…These results indicated that the uptake of PCDD/Fs by fly ash is obviously lower than that of activated carbon. To date, several reports have suggested that the uptake of PCDD/Fs by fly ash mainly originates form carbonous residue [39,40]. These reports agreed well with this paper (Figure 4f).…”

Effect of strengthened standards on Chinese ironmaking and steelmaking emissions

“…Although the small plants that closed represented 31.9% of all plants, they produced only 6.8% of iron and steel production in 2015 and mostly lacked control technologies (21.3% had SO2 controls and none had SO2 and NOX controls), such that their retirement led to much larger reductions in emissions than production capacity 30 . Of the large plants (that is, those producing >10 million tonnes of crude steel per year) that closed, all were older than 40 years, and half were older than 80 years; by virtue of their age, these plants also accounted for disproportionately large emissions relative to their production 31 . Meeting ULE standards will probably entail further retirements of smaller (that is, those producing <1 million tonnes of crude steel per year) and older plants (that is, those operating >80 years); we estimate that phasing out such plants will contribute 21.4%, 24.5% and 20.8% of reductions in PM, SO2 and NOX emissions, respectively (purple bars in Fig.…”

Occurrence and Formation Mechanism of PCDD/Fs and SCCPs in Chlorinated Paraffin Products

“…The analysis method of PCDD/Fs in CP samples was modified from the U.S. EPA Method 1613. − However, the pretreatment method of PCDD/Fs is usually based on environmental samples and biological samples and are not applicable to CP samples. − CPs are soluble in most organic solvents and have properties similar to PCDD/Fs, and the extraction of trace PCDD/Fs from the highly concentrated CP matrix is a challenge for analyzing PCDD/Fs from CP products. In this study, through screening various extractive methods and solvents, a mixture of dichloromethane and hexane (1:9, v/v; 50 mL) was used to remove some of the CP matrix finally.…”