title: Effects of bypass system on PCDD/F emission and chlorine circulation in cement kilns.
abstract: A bypass at the kiln inlet allows the effective reduction of alkali chloride cycles and thus perhaps affects the emission of PCDD/Fs. Effects of bypass system on PCDD/F emission and chlorine circulation were studied in two typical dry cement kilns with 5000 ton/day clinker capacity in China and named CK1 and CK2, respectively. Firstly, the emission level of PCDD/Fs with the operation of bypass system was estimated in CK1, to certify that bypass system has a perfect adaption to the cement kiln regarding the PCDD/F emission even with the refuse derived fuel (RDF) as the replacement of fuel. On the other hand, the operating conditions in the CK2 were scrutinised by monitoring the concentrations of SO2, NH3 and HCl. In addition, the characteristics of raw meal, clinker, bag filter ash and bypass ash were also investigated by Energy Dispersive Spectrometer (EDS), metal and chlorine analysis. The balance of chlorine showed that 18 % of the possible accumulated chlorine could be ejected from the cement kiln system when 2 % of kiln exhaust gas was extracted. Furthermore, the emission level of PCDD/Fs in the main flue gas also decreased from 0.037 ± 0.035 ng I-TEQ/Nm(3) to 0.019 ± 0.007 ng I-TEQ/Nm(3) with a reduction efficiency of 48.2 %. Most importantly, PCDD/F emission from the bypass system was proven to have rather minor effect on the total emission factor. The congener distributions of PCDD/Fs were also analysed in the flue gas and fly ash, before and after application of bypass system, to find cues to the formation mechanism.
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Ming-Xiu
authors.initials: MX
authors.lastname: Zhan
authors.affiliation: China United Engineering Corporation, Hangzhou, 310052, People's Republic of China.
authors.forename: Jianying
authors.initials: J
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang, China. chentong@zju.edu.cn.
authors.forename: Tong
authors.initials: T
authors.lastname: Chen
authors.affiliation: Huaxin Environment Engineering Co., Ltd, Wuhan, China.
authors.forename: Yeqing
authors.initials: Y
authors.lastname: Li
authors.affiliation: Huaxin Environment Engineering Co., Ltd, Wuhan, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Li
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Alfons
authors.initials: A
authors.lastname: Buekens
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002681:China; D000072338:Dibenzofurans, Polychlorinated / Q000032:analysis*; D004784:Environmental Monitoring; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins
keywords: Bypass system; Cement kiln; Chlorine circulation; PCDD/Fs; RDF