Formation of polychlorinated dibenzofurans and dioxins during combustion, electrical equipment fires and PCB incineration.
Formation of polychlorinated dibenzofurans and dioxins during combustion, electrical equipment fires and PCB incineration.
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燃烧、电气设备火灾和 PCB 焚烧过程中会形成多氯二苯并呋喃和二恶英。
DOI：
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发表时间：
1985
影响因子：
10.4
通讯作者：
L. E. Johnston
中科院分区：
文献类型：
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作者：
O. Hutzinger;G. G. Choudhry;B. Chittim;L. E. Johnston
多氯二苯并对二恶英(PCDDs)和多氯二苯并呋喃(PCDFs)很可能是由多种初级前体热合成而成。然而，当起始材料只需要一两个反应步骤就能形成这些化合物时，预计这些化合物的含量最高，就像氯苯酚、氯苯和多氯联苯(PCBS)的情况一样。实验室的热解确实表明，多氯联苯可以产生大量的多氯二苯并二恶英，而氯苯则同时产生多氯二苯和多氯二苯并二恶英。此外，还会形成各种其他氯代芳烃化合物。从这些实验和涉及多氯联苯起火的事故中，我们知道多氯二苯并呋喃是与多氯联苯有关的最重要的有毒化合物。大多数商用多氯联苯含有低ppm范围内的多氯二苯并呋喃。在电气设备的正常运行期间，PCDF浓度不会增加。涉及多氯联苯的事故(火灾和爆炸)可使烟尘中的多氯二苯并呋喃含量高达1000ppm或更高。在现代焚烧装置中，如果使用高温、过量空气和足够的停留时间，多氯联苯的有效热销毁是可能的。最低温度和停留时间的准确数字无法给出，因为原料和焚烧炉的结构对销毁效率有很大影响。用于销毁多氯联苯的环保局许可焚烧炉排出的污水中只含有极低水平的多氯二苯并二恶英和多氯二苯并呋喃。
Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are likely formed by thermal synthesis of a variety of primary precursors. Highest levels of these compounds are expected, however, when the starting material requires only one or two reaction steps for their formation, as is the case with chlorophenols, chlorobenzenes and polychlorinated biphenyls (PCBs). Laboratory pyrolyses have indeed shown that PCBs give significant yields of PCDFs, and chlorobenzenes give both PCDFs and PCDDs. In addition, a variety of other chloroaromatic compounds are formed. From these experiments and from accidents involving PCB fires, it is known that PCDFs are the most important toxic compounds associated with PCBs. Most commercial PCBs contain PCDFs in the low ppm range. PCDF concentration does not increase during normal operation in electrical equipment. Accidents (fires and explosions) involving PCBs can give PCDF levels in soot of up to 1000 ppm and higher. Effective thermal destruction of PCB is possible in modern incineration units, provided high temperatures, excess air and sufficient residence times are used. Exact figures for minimum temperature and residence time cannot be given, since feedstock and incinerator construction greatly influence destruction efficiency. Effluents from EPA-licensed incinerators used for PCB destruction contain only very low levels of PCDDs and PCDFs.