Inventory of PCDD/Fs and Fly Ash Characteristics during the e-Waste and Municipal Solid Waste Co-Incineration Process

Abstract

In the face of a challenging situation for yearly e-waste (EW) increment and disposition, EW co-incineration (EWC) with municipal solid waste (MSW) is a promising solution whose emission characteristics remain unclear. This study is conducted in a 400 tons/day MSW incineration (MSWI) plant to characterize polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and fly ash (FA) properties. Analytical methods include high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) for PCDD/F determination, as well as X-ray diffraction (XRD), X-ray fluorescence (XRF), ion chromatography (IC), and leaching toxicity test for FA. The results indicate that toxic PCDD/F amounts are doubled by EWC in both primary exhaust gas (EG) and FA with international toxic equivalent quantity (I-TEQ) concentrations of 19.00 ± 6.32 ng I-TEQ/Nm3 and 1.33 ± 0.56 ng I-TEQ/g. After the clean-up of the air pollution control system (APCS), emitted PCDD/Fs in solid and gas phases, as well as major air pollutants (CO, NOx, SO2, HCl, and particulate matter), are permissive within the limit values of national standards GB 18485-2014 and GB 16889-2008. Distribution patterns for 136 PCDD/F isomers are analogous in both MSWI and EWC conditions. De novo synthesis is always the major formation route for both EWC and MSWI conditions, while dibenzodioxin/dibenzofuran (DD/DF) chlorination also contributes. The generation of 136 PCDD/Fs is enhanced by EWC, and the correlation coefficients of Cl and Cu in the fuel with the generation of 136 PCDD/F isomers are found to be R = 0.92 and 0.88, respectively. The main components in FA from MSWI and EWC differ less, both containing CaO, SiO2, and Al2O3. However, Cl and Cu contents, as well as leaching toxicity in FA are elevated by EW. Heavy metals, except for Cd, Ni, and Pb, meet the requirement of the standard.