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Effects of Sulfur and Calcium Compounds on Dioxin Reduction in a Fluidized Bed Combustor

Category: Air Toxics

Volume: 19 | Issue: 5 | Pages: 1079-1094
DOI: 10.4209/aaqr.2019.03.0140
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Hung-Ming Shen1, Ya-Fen Wang2, Chien-Song Chyang 1, Wei-Chih Wang1, Geng-Min Lin1

  • 1 Department of Chemical Engineering Research Center for Circular Economy, Chung Yuan Christian University, Taoyuan 32023, Taiwan
  • 2 Department of Environmental Engineering, Chung Yuan Christian University, Taoyuan 32023, Taiwan

Highlights

  • The concentration of PCDD/Fs of fly ash collected from the cyclone was very low.
  • The formation of dioxin depends on not only the chlorine content, but also copper.
  • The inhibitory effect of sulfur on dioxin was not clear for low copper content.

Abstract

The focus of this study is the effects of sulfur and calcium compounds on reducing dioxins in fly ash collected from the baghouse of a pilot-scale fluidized bed combustor. Pelletized sawdust with various amounts of polyvinyl chloride (PVC), pyrite, and calcium hydroxide was used as the feeding material. The experimental results indicated an extremely low concentration of dioxin in the fly ash from the cyclone (0.025 to 0.284 ng g–1), and the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the fly ash collected from the baghouse increased by 27.4% as the chlorine content increased from 0.568 to 1.136 wt%. The inhibition of PCDD/Fs by sulfur is not clear and can be attributed to the low content of copper (average 387 ppm), which serves as the catalyst for the Deacon reaction. Octa-chlorinated dibenzofuran (OCDF) was the major congener of the PCDD/Fs. The highest toxicity-equivalent (I-TEQ) of 2,3,7,8-substituted congeners was 2,3,4,7,8-PeCDF, which accounted for 37% of the total congeners (average value). The correlation between the I-TEQ values and 2,3,4,7,8-PeCDF concentration of fly ash is also discussed.

Keywords

Dioxin Fly ash Sulfur compound Calcium compound Fluidized bed combustor


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