多氯萘(PCNs)作为《关于持久性有机物污染物(POPs)的斯德哥尔摩公约》增列的一类新型POPs物质，由于其潜在的环境和健康风险，对其环境问题的研究已引起了广泛关注。全面削减和控制PCNs的排放是未来数十年全球共同面临的重要任务，根据工业热过程中PCNs的排放特征并结合有色金属冶炼的工艺技术特点，推断再生铝冶炼过程可能是PCNs的重要潜在排放源，但目前对再生铝冶炼过程中PCNs的排放特征研究较少，尤其对影响PCNs生成的关键因素及其生成机理的研究还很匮乏，对其主要生成途径的认识尚不够深入。 本论文在前期研究的基础上，选取实际再生铝冶炼企业为研究对象，对其冶炼过程中PCNs的排放浓度、分布特征、冶炼各环节可能存在的有机氯代前驱体以及对周边环境的影响进行了详细调查研究；在此基础上，在实验室内通过高温管式炉模拟再生铝冶炼环境，考察从头合成、前驱体生成以及萘的氯化途径下PCNs的生成水平与组成特征，分析不同冶炼阶段PCNs主要的生成机理，并对影响PCNs生成的关键影响因素进行了系统分析。取得的主要结果如下： (1)再生铝冶炼不同阶段烟气中PCNs的排放浓度存在明显差别，加料段＞熔炼段＞精炼段。炉灰、飞灰和底灰中PCNs浓度差别也较大，除尘飞灰＞烘干炉炉灰＞铝灰。通过对冶炼各环节灰尘中可能的氯代前驱体进行定性扫描与定量分析，发现高浓度的PCNs有机氯代前驱体尤其是多环芳烃类(PAHs)前驱体普遍存在于再生铝冶炼的全过程中，且在旋转烘干炉炉灰中浓度最高，再生铝冶炼原料有机脱除工艺极大程度上促进了PCNs的直接生成或间接通过前驱体生成。 (2)再生铝冶炼企业空气中PCNs浓度范围为62.3-1917pg／m³，车间外部分点位PCNs浓度水平与车间内空气中PCNs浓度水平相当。企业内部临近车间的部分土壤样品受PCNs污染较为严重，浓度范围为0.70-983ng／gd.w.。再生铝冶炼过程对周边环境的影响主要表现在距离厂区0.5㎞的区域，且随距离的增加，周边空气和土壤中PCNs浓度降低。不同再生铝冶炼企业PCNs在土壤与大气中的纵向运动状态较为一致，表现为低氯代PCNs(一至四氯萘)从土壤向大气挥发，高氯代PCNs(七氯萘和八氯萘)从大气向土壤沉降。 (3)实验室模拟前驱体生成PCNs的研究表明，前驱体生成PCNs的浓度随温度升高而升高，且在800℃时(对应再生铝熔炼工艺段)前驱体生成PCNs的浓度水平显著增高，是对应烘干温度段(550℃)的5倍以上，推测再生铝熔炼阶段PCNs的主要生成途径为前驱体生成。金属氯化物和有机氯代添加剂是影响前驱体生成PCNs的关键因素，铝的存在形态对前驱体生成PCNs影响很小。 (4)萘的氯化生成PCNs主要发生在400-600℃温度段，且在500℃(对应再生铝冶炼烘干工段)生成PCNs浓度最高，部分相邻氯取代数的PCNs同系物之间相关性非常显著，推测萘的逐级氯化是其重要反应过程。金属氯化物和氯代添加剂是影响萘的氯化生成PCNs的关键因素，且对PCNs同系物的氯化程度有促进作用。 (5)从头合成PCNs主要发生于500℃，其他温度段PCNs从头合成率较低，单质铝对从头合成PCNs具有明显催化作用，从头合成是再生铝烘干工段PCNs的主要生成途径，金属氯化物和氯代添加剂对从头合成PCNs同系物的氯化程度有促进作用，但不是影响PCNs从头合成的关键因素。 关键词：再生铝冶炼，多氯萘，排放特征，生成机理，影响因素

Polychlorinated naphthalene (PCNs),as a kind of persistent organic pollutant newly added in the controlling list of the Stockholm convention, its relative environmental problems have drawn wide attention due to its potential risk to the environment and human health. The reduction and control of PCNs will be a major task in decades for the global. According to the PCNs emission characteristics and the features of non-ferrous metal smelting technology, the secondary aluminum smelting process is likely to be an important potential source of PCNs. However, studies on PCNs emission characteristics of secondary aluminium smelting are rare, especially for the key factors and its formation mechanism research. On the basis of previous studies, this paper selected three representative secondary aluminum smelting plants with different smelting processes and ash filters as objects of our study, the PCNs emission characteristics, potential precursors during smelting and influence on surrounding environment were investigated. Based on the investigation results of the plants, the three potential pathways of PCNs formation (De novo synthesis, precursor formation and naphthalene chlorination) during the seconday aluminum smelting process were simulated in the laboratory through a high temperature tube furnace. Finally, the key factors influencing these three pathways during the secondary aluminum smelting were researched and analyzed. The main results are as follows: (1)There are significant differences in the emission concentrations of PCNs in flue gas from different stages of recycled aluminum smelting, feeding section>smelting section>refining section. The PCN concentration in the furnace ash, fly ash, and bottom ash is also significantly different, dust ash removal>furnace ash>aluminum ash. It has been found that high concentrations of PCNs organochlorinated precursors, especially PAH precursors exist in the entire process of recycled aluminum smelting through qualitative scan and quantitative analysis of possible chlorogenic precursors in the dust at each step of the smelting process, and the concentration in the raw material drying furnace ash is the highest, drying pretreatment of recycled aluminum smelting raw materials greatly promoted the direct generation of PCNs or indirectly generation through precursors. (2)The concentration of PCNs in the air of recycled aluminum smelting enterprises ranges from 62.3-1917pg/m3, and the concentration of PCNs outside the workshop is equivalent to the concentration of PCNs in the air in the workshop. Some soil samples of the company's internal workshop are seriously contaminated by PCNs, with concentrations ranging from 0.70 to 983ng/g d.w. The impact of recycled aluminum smelting process on the surrounding environment is mainly reflected in the area 0.5㎞ distance from the plant area,and with the increase of distance, PCNs in the surrounding air and soil are less affected by the plant area. The longitudinal movement of PCNs in the soil and the atmosphere is more consistent, showing that low-chlorinated PCNs (one to tetrachloronaphthalene) volatilize from the soil to the atmosphere, and high-chlorinated PCNs (heptachlor and octachloronaphthalene) settle from the atmosphere to the soil. (3)The simulation of PCNs generated from precursors in the laboratory shows that the concentration of PCNs generated from precursors increases with increasing temperature, and the concentration level of PCNs generated from precursors at 800℃ (corresponding to the smelting process of recycled aluminum) is extremely significant, which is more than 5 times of the corresponded dring temperature range (550℃),it is presumed that the main generation route of PCNs in the smelting process of recycled aluminum is precursor formation. Metal chlorides and organic chlorinated additives are the key factors affecting the formation of PCNs in precursors, the existent morphology of aluminum has little effect on PCNs generated from precursors. (4)The chlorination of naphthalene to PCNs mainly occurs in the temperature range of 400-600℃, and the highest concentration of PCNs generated at 500℃ (corresponding to the smelting process of recycled aluminum), and the PCNs monomers with adjacent chlorine substitution number have a good correlation, it is inferred that the main formation mechanism of naphthalene is its progressive chlorination. Metal chlorides and chlorinated additives are the key factors affecting the chlorination of naphthalene to PCNs, and they promote the chlorination degree of PCNs homologues. (5)The synthesis of PCNs from scratch mainly occurs at 500℃ (corresponding to the smelting process of recycled aluminum), it is difficult to synthesize PCNs from scratch in other parts of the temperature range. Al elemental and alumina have a catalytic effect on the synthesis of PCNs from scratch, it is assumed that the main route to synthesize PCNs for recycled aluminum in the pretreatment drying stage is scratching synthesis. Metal chlorides and chlorinated additives can promote the chlorination of PCNs homologues from scratch, but it is not a key factor affecting the synthesis of PCNs from scratch. KEY WORDS: Secondary aluminium smelting, Polychlorinated naphthalene, Emission characteristic, Formation mechanism, Influencing factor