Formation pathways, gas-solid partitioning, and reaction kinetics of PCDD/Fs associated with baghouse filters operated at high temperatures: A case study

• Published in: The Science of the total environment 2023-01, Vol.857, p.159551-159551, Article 159551
• Main Authors: Lin, Xiaoqing, Wang, Xiaoxiao, Ying, Yuxuan, Wu, Angjian, Chen, Zhiliang, Wang, Lei, Yu, Hong, Zhang, Hao, Ruan, Aizhong, Li, Xiaodong, Yan, Jianhua
• Format: Article
• Language: English
• Subjects: Chlorophenol route; de novo synthesis; Desorption; Memory effect; Municipal solid waste incineration; PCDD/F-fingerprints
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.159551

The application of the 3T method during combustion (i.e., a Temperature > 850 °C, a residence Time > 2 s, and sufficient Turbulence) can lead to elevated operating temperature in the baghouse filter for the municipal solid waste incineration (MSWI) systems without sufficient heat exchange capacity, which is potentially detrimental to the emission control of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Herein, a field study focusing on the distribution and variation of PCDD/Fs in gaseous and solid phases in a baghouse filter with high operating temperature (225–230 °C) was carried out. The concentration of PCDD/Fs in gases at the outlet of the baghouse filter was around 1 order of magnitude higher than that in inlet gases (i.e., noticeable memory effect of PCDD/Fs), because of the significant PCDD/Fs formation in filter fly ash (primarily contributed by the precursor pathway) followed by PCDD/Fs desorption. In addition, the mechanisms and factors resulting in the memory effect of PCDD/Fs were identified based on a laboratory study that carefully investigated the formation and desorption of PCDD/Fs at potential operating temperatures of baghouse filters (i.e., 180, 200, and 225 °C). The temperature was identified as the key factor inducing the memory effect of PCDD/Fs, because: i) PCDD/Fs memory effect was not observed for baghouse filters with low operating temperatures of ~150 °C in previous studies; ii) both the formation and desorption of PCDD/Fs were noticeably favored by rising temperature from 180 to 225 °C; iii) increasing temperature appeared to facilitate the transformation from inorganic Cl to organic Cl and the conversion from aliphatic carbon to aromatic carbon or unsaturated hydrocarbons, both of which were favorable to PCDD/Fs formation; and iv) the release rate of PCDD/Fs from fly ash was exponentially dependent on temperature based on the modeling results of reaction kinetics. [Display omitted] •Baghouse filter operated at ~225 °C caused obvious memory effect of PCDD/Fs.•PCDD/Fs formation from chlorophenols was greatly favored in baghouse filter.•Temperature was identified as the key factor inducing PCDD/Fs formation and desorption.•Potentially effective methods for mitigating memory effect of PCDD/Fs were proposed.