Role of Chlorine in Combustion Field in Formation of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans during Waste Incineration

Abstract

Combustion experiments performed in the presence of hydrogen chloride (HCl) in a laboratory-scale fluidized-bed reactor were carried out to elucidate the role of chlorine in the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs; together: PCDD/Fs) in various sections of a municipal waste incinerator. We first demonstrated that the homologue profile and the pattern of the congener proportions of PCDD/Fs for a model waste containing poly(vinyl chloride) (PVC) combusted in the absence of HCl were similar to those for a PVC-free waste combusted in the presence of HCl. This showed no difference between PVC in the waste and injected HCl in the role as a chlorine source in PCDD/F formation during incineration. Next, to investigate PCDD/F formation in each section of the incinerator, we carried out combustion experiments with the PVC-free waste, injecting HCl at different locations of the incinerator. The amounts of PCDDs and PCDFs formed were significantly reduced when HCI was not supplied to the main combustion section. The presence of HCI in the main combustion section was essential for the formation of PCDD/Fs, even in the downstream sections. This finding indicates that compounds that were able to form PCDD/Fs in the downstream sections were mainly formed in the main combustion section in the presence of HCl.

Field pilot study on emissions, formations and distributions of PCDD/Fs from cement kiln co-processing fly ash from municipal solid waste incinerations

“…The dominance of PCDFs over PCDDs also suggests that most formation of PCDD/Fs occurs through de novo synthesis during cement kiln coprocessing of MSWI fly ash, which is in agreement with theoretical assumptions [38]. The positive effect of chloride on PCDD/F formation during waste incineration has been demonstrated in earlier laboratory scale experiments [39][40][41]. In the present study, the content of chloride in the particulate samples was determined according to the Chinese standard method for chemical analysis of cement (GB/T 176-2008) [42].…”

Polychlorinated Dibenzo-p-dioxin and Dibenzofuran (PCDD/F) Emission Behavior during Incineration of Laboratory Wastes. Part 2: PCDD/F Profiles and Characteristics of Output Materials

“…During this stage, metal chloride plays an important role in catalyzing the formation of PCDD/Fs (Lu et al, 2007;Nganai et al, 2011). Therefore, the PCDD/F content of ash increased with increasing Cl level in the input materials, which was also reported in a previous study (Hatanaka et al, 2005).…”

“…The incineration of input materials with high Cl content generates a large amount of PCDD/Fs (Hatanaka et al, 2005). Laboratory waste often has a high level of Cl because chloride or hydrochloric acid is a common reagent in laboratory experiments.…”

An Overview of PCDD/F Inventories and Emission Factors from Stationary and Mobile Sources: What We Know and What is Missing

“…The chlorine is either supplied as solid or in gas phase or both (Gullett et al, 1994;Hatanaka et al, 2005;Lu et al, 2007). In the absence of gaseous chlorine, the formation of PCDD/Fs occurs through a series of metal-catalyzed processes.…”