| 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 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34435]  |
| 专题 | 生态环境研究中心_环境化学与生态毒理学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 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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