title: High temperature suppression of dioxins.
abstract: Combined Sulphur-Nitrogen inhibitors, such as sewage sludge decomposition gases (SDG), thiourea and amidosulphonic acid have been observed to suppress the de novo synthesis of dioxins effectively. In this study, the inhibition of PCDD/Fs formation from model fly ash was investigated at unusually high temperatures (650 °C and 850 °C), well above the usual range of de novo tests (250-400 °C). At 650 °C it was found that SDG evolving from dried sewage sludge could suppress the formation of 2,3,7,8-substituted PCDD/Fs with high efficiency (90%), both in weight units and in I-TEQ units. Additionally, at 850 °C, three kinds of sulphur-amine or sulphur-ammonium compounds were tested to inhibit dioxins formation during laboratory-scale tests, simulating municipal solid waste incineration. The suppression efficiencies of PCDD/Fs formed through homogeneous gas phase reactions were all above 85% when 3 wt. % of thiourea (98.7%), aminosulphonic acid (96.0%) or ammonium thiosulphate (87.3%) was added. Differences in the ratio of PCDFs/PCDDs, in weight average chlorination level and in the congener distribution of the 17 toxic PCDD/Fs indicated that the three inhibitors tested followed distinct suppression pathways, possibly in relation to their different functional groups of nitrogen. Furthermore, thiourea reduced the (weight) average chlorinated level. In addition, the thermal decomposition of TUA was studied by means of thermogravimetry-fourier transform infrared spectroscopy (TG-FTIR) and the presence of SO2, SO3, NH3 and nitriles (N≡C bonds) was shown in the decomposition gases; these gaseous inhibitors might be the primary dioxins suppressants.
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, PR China.
authors.forename: Ming-Xiu
authors.initials: MX
authors.lastname: Zhan
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, PR China. Electronic address: chentong@zju.edu.cn.
authors.forename: Tong
authors.initials: T
authors.lastname: Chen
authors.affiliation: China United Engineering Corporation, Hangzhou, 310052, PR China.
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, PR China.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, PR China.
authors.forename: Sheng-Yong
authors.initials: SY
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, PR 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, PR 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, PR China.
authors.forename: Alfons
authors.initials: A
authors.lastname: Buekens
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001572:Benzofurans / Q000032:analysis*; D060729:Coal Ash / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D005740:Gases / Q000737:chemistry; D006358:Hot Temperature; D017745:Incineration; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis; D012722:Sewage / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D060729:Coal Ash; D000072338:Dibenzofurans, Polychlorinated; D005740:Gases; D000072317:Polychlorinated Dibenzodioxins; D012722:Sewage; D009584:Nitrogen
keywords: Combined S–N inhibitors; Inhibition; PCDD/Fs; Simulated municipal solid waste; TG-FTIR analysis; Thiourea