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Volume 12, No. 2, April 2012, Pages 191-199 PDF(321 KB)  
doi: 10.4209/aaqr.2011.06.0079   

Effect of Temperature and CaO Addition on the Removal of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Fly Ash from a Medical Waste Incinerator

Ya-Fen Wang1, Lin-Chi Wang2, Lien-Te Hsieh3, Hsing-Wang Li4,5, Hung-Chi Jiang4, Yue-Sheng Lin4, Cheng-Hsien Tsai6

1 Department of Bioenvironmental Engineering and R&D Center of Membrane Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan, R.O.C.
2 Department of Chemical and Materials Engineering, Cheng Shiu University, Kaohsiung 833, Taiwan, R.O.C.
3 Department of Environmental Science and Engineering, National Pingtung University of Science & Technology, Pingtung 912, Taiwan, R.O.C.
4 Department of Environmental Engineering, National Cheng Kung University, Tainan 701, Taiwan, R.O.C.
5 Sustainable Environment Research Center, National Cheng Kung University, Tainan 701, Taiwan, R.O.C.
6 Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan, R.O.C




The effects of thermal treatment temperature and CaO addition on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) content in the fly ashes from a medical waste incinerator with high chlorine content (7.5%) were investigated. Two kinds of batch mode were examined: without CaO addition under the temperature range of 50–850°C, and with CaO addition at various Ca/Cl molar ratios (CCR = 0.8–44.3) at 250°C.
    The results show that the PCDD/F content in raw fly ash was 6.20 ng I-TEQ/g. When elevating the temperature from 50 to 400°Cwithout CaO addition, the PCDD/F content dramatically increased from 5.38 to 575 ng I-TEQ/g. Even at 850°C, the PCDD/Fs were not destructed apparently and were still with a concentration of 401 ng I-TEQ/g. However, with the addition of CaO at CCR = 17.7 at only 250°C, the removal ratio of PCDD/Fs reached to 87.2% and the PCDD/F content was significantly reduced to 0.889 ng I-TEQ/g, which meets the soil pollution standard of Taiwan EPA (1 ng I-TEQ/g) and could be considered as backfill. CaO addition was proven efficiently to enhance the reduction rate of PCDD/Fs in fly ashes during the thermal treatment at a low temperature, as well as inhibit the formation of PCDD/Fs.



Keywords: PCDD/Fs; Fly ash; Thermal treatment; Calcium oxide.



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