Field study and theoretical evidence for the profiles and underlying mechanisms of PCDD/F formation in cement kilns co-incinerating municipal solid waste and sewage sludge. (March 2017)

• Record Type: Journal Article
• Authors: Zhao, Yuyang; Zhan, Jiayu; Liu, Guorui; Ren, Zhiyuan; Zheng, Minghui; Jin, Rong; Yang, Lili; Wang, Mei; Jiang, Xiaoxu; Zhang, Xian
• Is Part Of: Waste management. Volume 61(2017)
• Page Start: 337
• Page End: 344
• Publication Date: 2017-03
• Subjects: Cement kiln -- Co-incineration -- Polychlorinated dibenzo-p-dioxins -- Polychlorinated dibenzofurans -- Municipal solid waste -- Municipal sewage sludge; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2016.12.008
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: PCDD/F profiles in different process stages of cement kilns were demonstrated. Tetra- to hexa-chlorinated dibenzofurans were dominant homologs in cement kilns. Deacon reaction might be suppressed by the alkaline conditions in cement kilns. Chlorination was speculated to be one of important pathways of PCDF formation. Abstract: A field study and theoretical calculations on the profile and formation mechanism of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) from two cement kilns co-incinerating municipal solid waste and sewage sludge were performed, and the PCDFs were mainly focused. The back-end areas of the cement kilns were identified to be the major sites of PCDD/F formation according to their distributions in particulate samples from different process stages. The proportions of tetra- to hexa-chlorinated dibenzofurans (∑Cl4–6 CDFs) at the kiln back-end areas were in the range of 50–80% of the total PCDD/Fs in mass concentrations and 62–87% in toxic equivalent concentrations. These results indicated that ∑Cl4–6 CDFs are the dominant homologs that should be the focus for reducing PCDD/F emissions in cement kilns that co-incinerate municipal solid waste and sewage sludge. It is speculated that the low contents of oxygen and copper compounds, as well as the alkaline conditions, may contribute to the dominance of ∑Cl4–6 CDFs in the PCDD/Fs formed. Chlorination was assumed to be the mechanism of formation of PCDFs. The results from model predictions and thermodynamic calculations used to test this assumption were consistent with the PCDF profiles observed from the field study.