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首页> 外文期刊>Environmental Science & Technology >Formation of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans from a Mixture of Chlorophenols over Fly Ash: Influence of Water Vapor
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Formation of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans from a Mixture of Chlorophenols over Fly Ash: Influence of Water Vapor

机译：粉煤灰中氯酚混合物中多氯代二苯并二恶英和二苯并呋喃的形成：水蒸气的影响

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Recent efforts have been made to establish readily measurable surrogate compounds, such as chlorophenols, for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), that would enable plant operations to limit formation. Despite the extensive studies conducted on PCDDs/Fs formation from chlorophenols, very few studies have been carried out in real combustion conditions with a realistic concentration of precursors and the presence of water. In the present study, low (10~(-9) M), stable concentrations of chlorinated phenols that are representative of concentrations of such compounds in municipal waste incinerator (MWI) raw flue gas were used in experiments investigating the formation of PCDDs/Fs over fly ash. Different mixtures of the chlorophenols (CPs) studied (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and 2,3,4,6-tetrachlorophenol) were passed through a bed of oxidized fly ash (carbon-free) and glass beads with and without the presence of water. The chlorophenol reactants used in this study were found to favor PCDD over PCDF formation. The presence of water was observed to considerably reduce the yields of all PCDD/F formed ( < 0.3% phenol conversion). The PCDD homologue and isomer distributions were not affected by the presence of water, unlike the PCDF compounds. The major PCDD homologue groups formed were tetra- and penta-, both with or without water in the gas stream. The major PCDF homologue groups were mostly the lower chlorinated ones in the experiments performed in the presence or absence of water. These results contribute to the understanding of PCDD/Fs formation in realistic combustion conditions, including very low concentrations of precursors and the presence of water in the flue gas.
机译：最近，人们努力建立易于测量的替代化合物，例如多酚二苯并二恶英（PCDDs）和二苯并呋喃（PCDFs）的氯酚类，这将使工厂的生产能够限制其形成。尽管对由氯酚形成PCDDs / Fs进行了广泛的研究，但在实际燃烧条件下，实际浓度的前体和存在水的条件下，进行的研究很少。在本研究中，使用低浓度（10〜（-9）M）的稳定浓度的氯代酚（代表城市垃圾焚烧炉（MWI）原始烟气中此类化合物的浓度）用于研究PCDDs / Fs形成的实验飞灰。将研究的氯酚（CP）的不同混合物（2-氯酚，2,4-二氯酚，2,4,6-三氯酚和2,3,4,6-四氯酚）通过氧化粉煤灰床（碳（不含）和玻璃珠（有无水）。发现本研究中使用的氯酚反应物比PCDF形成更有利于PCDD。观察到水的存在大大降低了所有形成的PCDD / F的产率（<0.3％的苯酚转化率）。与PCDF化合物不同，PCDD的同系物和异构体分布不受水的影响。形成的主要PCDD同源基团为四或五原子团，气流中有水或无水。在有水或无水条件下进行的实验中，主要的PCDF同源基团大多为氯化度较低的基团。这些结果有助于理解实际燃烧条件下PCDD / Fs的形成，包括非常低的前体浓度和烟道气中水的存在。

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