Volume 14, No. 4, June 2014, Pages 1168-1178 PDF(321 KB)
Memory Effects of Polychlorinated Dibenzo-p-dioxin and Furan Emissions in a Laboratory Waste Incinerator
Jhong-Lin Wu1,2,3, Ta-Chang Lin1,2, Lin-Chi Wang4, Guo-Ping Chang-Chien5,6
1 Department of Environmental Engineering, National Cheng Kung University, 1, University Road, Tainan 70101, Taiwan
2 Sustainable Environment Research Laboratories, National Cheng Kung University, 1, University Road, Tainan 70101, Taiwan
3 Environmental Resource and Management Research Center, National Cheng Kung University, 1, University Road, Tainan 70101, Taiwan
4 Department of Civil Engineering and Geomatics, Cheng Shiu University, 840, Chengching Road, Kaohsiung 83347, Taiwan
5 Super Micro Mass Research and Technology Center, Cheng Shiu University, 840, Chengching Road, Kaohsiung 83347, Taiwan
6 Department of Cosmetic and Fashion Styling, Cheng Shiu University, 840, Chengching Road, Kaohsiung 83347, Taiwan
Laboratory wastes are discharged from experimental, testing, or analysis processes, and contain various toxic chemical compounds with a high heating-value and a high chlorine content (> 9%). Elevated PCDD/F (polychlorinated dibenzo-p-dioxin and furan) emissions during start-up stages are caused by combustion of waste with high chlorine contents, incomplete combustion, and so called "memory effects". Even though the duration of cold start-up is short compared with the hours of continuous steady operation in a waste incinerator, its negative effects with regard to PCDD/F emissions on both human health and the environment cannot be neglected. A full-scale laboratory-waste incinerator which is operated for 10 days in each run and has 15 to 20 runs annually was investigated in this study. Eleven PCDD/F samples of stack flue gas were collected during the cold start-up periods (for 60.5 hrs). The gas temperature of the primary combustion chamber was above 850°C, and was maintained at between 850 and 900°C by injecting diesel fuel without waste feed. For first 1.5–7.5 hours, the PCDD/F concentration in the stack flue gas was as high as 0.656–1.15 ng I-TEQ/Nm3. Afterward, during hours 10.5–35.5 and 54.5–60.5, this reduced to 0.159–0.459 and 0.218–0.254 ng I-TEQ/Nm3, respectively. Based on principal component analysis (PCA) and the L/H ratio, the results revealed a higher L/H ratio (1.23) before hour 32, indicating that less chlorinated PCDD/F homologues (tetra and penta) dominated, while after hour 32 more chlorinated PCDD/F homologues (hexa, hepta and Octa) had a higher mass concentration and the L/H ratio fell to 0.42. These results indicate that the PCDD/F emissions during cold start-up were caused by memory effects and thermal desorption. Therefore, in order to reduce the PCDD/F emissions from the stack flue gas of waste incinerators, is highly recommended that a higher amount of activated carbon injection is used in front of the bag filters.
PCDD/Fs; Stack flue gas; Laboratory waste; Incineration; Memory effect.