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题名: 再生铜和再生铝冶炼过程中氯代和溴代二恶英的生成机理研究
作者: 王美
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 郑明辉 ; 刘国瑞
关键词: 氯代二恶英类,溴代二恶英类,再生铜冶炼,再生铝冶炼,冶炼工艺段,PCDD/Fs, PBDD/Fs, Secondary copper smelting processes, Secondary aluminum smelting processes, Smelting stages
其他题名: Formation Mechanisms of Chlorinated and Brominated Dioxins/Furans during Secondary Copper and Aluminum Smelting Processes
学位专业: 环境科学
中文摘要:     再生有色金属冶炼作为典型的工业热过程被认为是非故意生成的持久性有机污染物(UP-POPs)的主要排放源之一。研究影响 UP-POPs生成的主要因素以及生成机理对 UP-POPs的源排放控制具有重要的意义。目前对再生有色金属冶炼过程中氯代二恶英PCDD/Fs)的排放水平和排放特征已有系统研究,但对再生有色金属冶炼过程中 PCDD/Fs的生成机理尚有待深入研究,对再生有色金属冶炼过程中溴代二恶英(PBDD/Fs)生成的主要工艺阶段、关键影响因素以及排放特征的研究尚未开展。论文在前期研究的基础之上,选取了再生有色金属冶炼行业中产量比重较大且排放水平相对较高的再生铜和再生铝冶炼企业作为研究对象,对冶炼过程中 PBDD/Fs的排放水平、排放特征、排放因子和关键影响因素进行了系统研究。同时,在现场排放研究的基础之上,研究针对再生铜冶炼过程,选取实际再生铜冶炼过程产生的飞灰为基质,开展了实验室模拟研究,明确了影响 PCDD/Fs和PBDD/Fs生成水平和生成特征的关键因素,并根据PCDD/Fs和 PBDD/Fs的生成特征,推断PCDD/Fs和PBDD/Fs可能的生成途径。通过对实验结果的分析,得出以下结论:
1.开展了再生铜冶炼过程中 PBDD/Fs的现场排放研究,识别了PBDD/Fs生成和排放的主要工艺阶段。采集了冶炼过程中不同冶炼阶段(加料熔融段、氧化段和还原段)的烟道气样品,发现加料熔融段是 PBDD/Fs生成和排放的主要工艺阶段,占总排放量的 83%。揭示了再生铜冶炼过程中 PBDD/Fs的排放特征,发现高溴代二恶英/呋喃是主要的同类物。此结果将为再生铜冶炼过程中 PBDD/Fs主要工艺段的识别提供依据,并将有助于更有效的控制再生铜冶炼过程中 PBDD/Fs的生成和排放。
2.选取了4家不同类型和规模的再生铝冶炼厂,阐明了 PBDD/Fs的排放特征,烟道气样品中PBDD/Fs的浓度范围为143.7–4572.8pg/Nm3,烟道气中PBDD/Fs的分布以高溴代同类物为主。研究发现:原料的构成是影响再生铝冶炼过程中PBDD/Fs排放水平的关键因素,对削减再生铝冶炼过程中PBDD/Fs的排放具有重要的实际意义。其次,研究还发现再生铝冶炼过程中PBDD/Fs的排放主要集中在加料熔融段,为针对  PBDD/Fs排放的重点工艺节点进行工艺技术改进提供了参考依据。
3.以实际再生铜冶炼过程中产生的飞灰为反应基质,设计了实验室模拟的热化学反应,研究发现:飞灰可在短的时间内(≤10 min)促进PCDD/Fs和PBDD/Fs的明显生成,最高生成增量可分别达139和324倍。同时,结合PCDD/Fs和PBDD/Fs同类物的分布特征,发现低氯代/低溴代同类物的百分含量随着反应的进行而逐渐降低,高氯代 /高溴代同类物的百分含量则明显增加。推断低氯代/低溴代同类物的氯化/溴化是再生铜冶炼过程中高氯代/高溴代同类物生成的重要途径之一。这些结果有助于了解再生铜冶炼过程中PCDD/Fs和 PBDD/Fs的生成机理。
英文摘要:     Secondary  non-ferrous  metal  smelters  are considered  to  be  major  sources  of unintentionally  produced  persistent  organic   pollutants (UP-POPs).  Studies  of  the factors that influence the formation  of UP-POPs and the mechanisms involved in UP-POP  formation  are   important  because  they   provide  information  that   will  allow techniques  for decreasing  UP-POP emissions  to  be  developed. Intensive  studies  of emissions  of  polychlorinated dibenzo-p-dioxins  and  dibenzofurans  (PCDD/Fs)  and other chlorinated  organic pollutants during  secondary metal  smelting processes have been  performed,   but   relatively  few   studies   of  the   formation  and   emission   of polybrominated  dibenzo-p-dioxins  and  dibenzofurans  (PBDD/Fs),  which  are  toxic brominated analogs of PCDD/Fs, have been performed. The formation of PCDD/Fs has been  studied   in   many  laboratory   simulations   with  the   aim  of   identifying   the characteristics of PCDD/F formation processes and the mechanisms that are potentially involved. However, most of these studies have focused on municipal waste incineration processes,  and  no  simulation  studies  have  yet  been  performed  to  investigate  the formation of PCDD/Fs during secondary metal smelting process. Because of the results of previous  investigations, we  chose, in  the study  presented  here, to  investigate the emissions  of  PBDD/Fs  during  secondary   copper  smelting  (SeCu)  and  secondary aluminum smelting  (SeAl) processes.  These are  major non-ferrous metal  production processes that emit UP-POPs at  high concentrations. The PBDD/F concentrations and congener profiles emitted, and the factors that influence PBDD/F emissions from SeCu and SeAl  processes were  investigated in  detail. Furthermore,  the results of  the field study of secondary  metal smelting processes  led us to  perform a series  of laboratory experiments using fly ash from a SeCu plant as a matrix with the aim of quantifying the effects of SeCu  fly ash on the  formation of PCDD/Fs and  PBDD/Fs, determining the characteristics  of the  PCDD/Fs  and  PBDD/Fs  formed during  SeCu  processes,  and identifying the  mechanisms that  may be involved  in the  formation of  PCDD/Fs and PBDD/Fs during these processes. The results are presented below.
1.    Samples  of  stack  gases  emitted  during  three  SeCu  processes,  feeding-fusion,oxidation, and deoxidization,  were collected  and analyzed for PBDD/Fs. The aim was to  clarify  the major  stages  of PBDD/Fs  emissions during  SeCu  processes. PBDD/F emissions were found to occur mainly in the feeding-fusion stage. Larger
quantities   of   polybrominated   dibenzofurans   (PBDFs)   than   polybrominated dibenzo-p-dioxins (PBDDs)  were produced during  all of the  smelting processes. The  more-brominated  PBDD/F  congeners  were  the  dominant  congeners.  The PBDD/F  emission  factors  for the  feeding-fusion,  oxidation,  and  deoxidization stages were 715, 119, and 31 ng/t, respectively. The results of this study might help identify the stages of the smelting process that produce the most PBDD/Fs and help in the  development of  techniques for  decreasing PBDD/F emissions  from SeCu plants.
2.    Samples  of stack  gases  emitted  by four  SeAl  smelters that  used  different  raw materials and techniques were collected and  analyzed for PBDD/Fs. The aim was to allow  the emissions  of PBDD/Fs  during SeAl processes  to be  quantified and characterized. The PBDD/F  concentrations in the stack  gas samples were 143.7–4572.8 pg/Nm3  . The  composition of the  raw materials  used in  the smelters  was found to  be one  of the key  factors influencing  the amount  of PBDD/Fs  emitted during the SeAl processes. Overall, more PBDFs than PBDDs were emitted during the SeAl processes. The more-brominated  PBDD/F congeners were the dominant congeners. The PBDD/Fs emission is  consistent with the aluminum scrap content in the raw material in the SeAl smelters investigated. The PBDD/F emission factors were 180.1, 85.9,  and 14.3 µg/t (i.e.,  per tonne of aluminum produced)  when the proportions of  aluminum scrap in the  raw materials  were 100%, 80%,  and 50%, respectively (at plants WT, SC, and ZF, respectively). The results of this study will be useful in the development and implementation of measures  to control PBDD/F
emissions during SeAl processes.
3.    Laboratory experiments were performed using SeCu fly ash as a matrix for thermal reactions. The  aim was  to  vestigate  the effects  of fly  ash on  the formation  of  PCDD/Fs and  PBDD/Fs  and to  identify the  mechanisms that  may be  involved. Thermal reactions on the SeCu fly ash over a temperature range of 250–450 °C and with   reaction   times   of   10–120   min   caused   the   PCDD/F   and   PBDD/Fs concentrations in the  fly ash to increase  significantly. The PCDD/F and PBDD/F concentrations formed during the thermal reactions were about 99–139 and 59–324 times higher,  respectively, than  the PCDD/F  and PBDD/F  concentrations in  the original  fly  ash,  respectively, clearly  indicating  that  the  fly  ash  promoted the formation  of PCDD/Fs  and  PBDD/Fs.  Overall, the  PCDF  concentrations were much higher  than the  PCDD concentrations  and the  PBDF concentrations  were much  higher  than  the   PBDD  concentrations  after  the  thermal   reactions  had occurred.   The   more-hlorinated/brominated    congeners   were   the   dominant congeners that were formed. A comparison of the PCDD/F and PBDD/F congener patterns found  after the  thermal reactions  had occurred  with  those found  in the original fly ash showed that  the chlorination or bromination of less chlorinated or brominated congeners  might be an important  pathway in the  formation of more-chlorinated or  brominated congeners. The  results of this  study might help  in the development of techniques for controlling PCDD/F and PBDD/F emissions during SeCu processes.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34435
Appears in Collections:环境化学与生态毒理学国家重点实验室_学位论文

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Recommended Citation:
王美. 再生铜和再生铝冶炼过程中氯代和溴代二恶英的生成机理研究[D]. 北京. 中国科学院研究生院. 2015.
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