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钢铁行业六价铬元素流向分析
王妍
学位类型硕士
导师曹宏斌 ; 任彥萍
2015-10
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业化学工程
关键词钢铁工业 六价铬 总铬 三价铬 产污节点 流向分析
其他摘要

六价铬[Cr(VI)]是世界卫生组织公布的强致癌、致突变、致畸变物,是国家重点控制的5大重金属污染物之一。六价铬是钢铁冶炼过程中主要的伴生有害元素,通常会随冶炼过程“三废”排出,严重污染环境、危害生物健康。但是长期以来,我国的钢铁行业六价铬污染源背景研究不明确,污染分散并缺乏有效统计,使得行业难以有针对性地形成有效控制及处理六价铬污染的技术依据。本文旨在通过物质流分析方法,分析钢铁生产环节中铬形态与浓度的演变,针对六价铬流向的废渣、废水、废气三个领域,完整呈现钢铁生产过程中六价铬元素的流向和路径,为六价铬钢铁工业污染源解析提供重要基础,为建立钢铁行业六价铬的进一步削减与控制提供参考依据。主要研究内容及成果如下:(1)明确典型钢铁行业长流程主要工序产排污情况。生产的分析钢铁行业长流程生产流程及产污节点通过文献调研和咨询行业专家等分析钢铁长流程生产工艺及流程,选择采选矿、焦化、烧结/球团、炼铁、炼钢和轧钢全流程及不锈钢、铁合金2个重点子行业作为研究系统,系统整理相关工序和子行业的生产流程及产污节点,以及废水、废气和废渣等的排放情况。(2)根据铬元素的不同流向的状态及途径,划分出在生产过程中六价铬流入和流出的情况,明确钢铁生产中主要涉铬污染工序。结果表明铬元素在钢铁生产过程中广泛存在,其中六价铬在采选矿、铬渣烧结、炼铁、炼钢和轧钢5个工序均有参与,且以铬渣烧结和轧钢工序为主。 (3)钢铁生产中铬元素来源是矿石、消纳铬渣引入的Cr2O3、铬酸盐和重铬酸盐等原料,此外还有钝化过程的钝化液及不锈钢氧化皮中的Cr2O3、铬酸酐和铬酸盐等。含六价铬成品主要有采选矿阶段的精矿和尾矿,采用铬渣烧结的烧结矿,炼铁和炼钢工序的铁水及钢水和轧钢钝化后钢板表面的钝化膜。其中采矿工序进入矿石中的铬,炼铁、炼钢工序铁水及钢水中的铬和钝化工序进入钢板中铬的含量分别占输入总量的95.9%、99.9%、82.44%和98.8%,而钢铁生产中六价铬最主要的产生点为冷轧钝化和不锈钢钝化酸洗两部分。(4)含六价铬废气主要为以铬渣为烧结原料时产生的粉尘,炼钢生产的烟尘和轧钢钝化工序产生的铬酸雾。含六价铬废水主要有采选矿精矿和尾矿废水,烧结工序中使用铬渣后水封拉链污水池内污水;轧钢过程钝化、电镀过程产生含Cr6+废水;不锈钢酸洗废水。含六价铬固体废弃物主要产生于烧结和炼铁过程炉渣、炼钢钢渣,轧钢钝化和不锈钢生产的含铬污泥中。含六价铬固废主要来自炼钢和轧钢钢渣、不锈钢渣泥中。其中目前钢铁工业六价铬最主要的产生点为钢铁生产过程中的表面处理工序(钝化和不锈钢酸洗)和铁合金冶炼,后续治理首先应集中在这几个环节上。(5)钢铁生产主要工序的六价铬流向图及长流程生产的铬元素流向汇总图。通过文献和实测数据和生产流程节点,完成5大工序和2个重点子行业六价铬及伴随污染物流入、产生和扩散过程的物料平衡关系,及钢铁生产主要工序的流向汇总图。(6)结合钢铁行业六价铬三废末端排放,提出治理原则和趋势。六价铬三废以废渣为主,废水次之,废气较少。废渣中除含一定量铬元素外,还含大量铁、锌、镍等有价值金属,应加强回收利用或循环作其它工艺的原料;钢铁行业目前主要采用的仍是化学法对废水进行处理,应对化学方法进行优化和改进,并加快物理和生物法水处理技术的研究和推广;对废气进行净化补集。在原料替代方面,大力发展低铬/无铬钝化技术在源头减少六价铬的引入。 

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A potent carcinogen and mutagen which can lead to distortion to humans announced by the World Health Organization and one of the five major heavy metal pollutants strictly controlled by our country, hexavalent chromium [Cr(VI)] is the major associated harmful element in the iron and steel smelting process. It is usually discharged together with the “three waste” (waste water, waste gas and waste residue) of the smelting process, and as a result, it will cause heavy environmental pollution and put a great threat to the health of living beings. However, for a long time, not having a clear-cut background for the sources of hexavalent chromium pollution in the steel industry of our country, together with the decentralization of pollutions and the insufficiency of the effective statistics has prevented the industry from forming a technical basis for effectively controlling and coping with the hexavalent chromium pollution. By analyzing the evolution of the morphology and concentration of chromium in the production process of steel through the material flow analysis (MFA) approach, this paper, in the three fields—waste residue, waste water and waste gas—where hexavalent chromium goes, aims to thoroughly present the directions the hexavalent chromium flows and its paths in the production process of steel, therefore, provide an important basis for the analysis of the pollution sources of hexavalent chromium in steel industry, and provide a reference for the further cuts and controls of hexavalent chromium in steel industry. The main content and results of the research are as follows:(1) Through literature research and consulting experts, analysed the manufacturing technique and process of the long steel-making process; by selecting the overall process of mining, carbonizing, sintering, iron-making, steel-making and steel rolling, and the two key sub-sectors of stainless steel and titanium alloy as the research system, systematically sorted out related procedures and the pollution node of sub-sectors, and the emission of waste water, waste gas and waste residue.(2) On the basis of different directions and paths hexavalent chromium goes to, clarified its inflow and outflow in the production process, and clarified the main procedures polluted by chromium in the production process of steel. And the result shows that chromium widely exist in the production process of steel, and hexavalent chromium involves in all five procedures: mining, chromium slag sintering, iron-making, steel-making and steel rolling, and mainly in the procedure of chromium slag sintering and steel rolling.(3) In production process of steel, chromium comes from such sources as minerals, the Cr2O3, the chromate and the dichromate produced by eliminating chromium slag; besides, passivation solution in process of passivation and the Cr2O3, chromic anhydride and chromate in the oxide scale of stainless steel can also bring chromium. Finished products containing hexavalent chromium are mainly the concentrates and tailings at the stage of mining and dressing, the sinters using sintered chromium slag, the hot metal and the molten steel in the procedure of iron- and steel-making, and the passivation films on the surface of the passivated steel plate. Respectively, the chromium in the minerals in the process of mining and dressing takes up 95.9% of the general input, the chromium in the hot metal and the molten steel in the process of iron- and steel-making 99.9% and 82.44%, and the chromium in steel plates in the process of passivation 98.8%. And the main production points of hexavalent chromium come down to two parts: the process of passivation and the process of stainless steel pickling.(4) Clarified the main points where the hexavalent chromium lies in the emissions of the terminal “three wastes” (waste gas, waste water and waste residue). The waste gas containing hexavalent chromium mainly consists of the dust produced when taking chromium slag as the raw material for sintering, of the mist of chromic acid produced in steel-making and in the passivation of steel rolling. The waste water containing hexavalent mainly comes from the waste water in mining and dressing concentrates and tailings, the effluent in the water sealing zipper sewage reservoir after applying chromium slag in sintering process, the effluent containing Cr6+ produced in passivation in steel-making and in the process of electroplating, and the effluent of stainless steel pickling. The waste residue containing hexavalent chromium mainly comes from the slag produced in sintering, iron- and steel-making, and from the sludge containing chromium produced in the process of passivation of steel rolling and stainless steel.(5) The flow diagram and flow summary graph of hexavalent chromium in steel production the main process Through literature, experimental data and the production process node, and by means of mass balance model, achieved the mass balance among the process of inflow, generation and diffusion of hexavalent chromium and the associated pollutants in five processes and two key sub-sectors.(6) Based on the terminal emission of the “three wastes” of hexavalent chromium in steel industry, proposed the treatment principles and trend. The waster residue ranks the highest proportion in the three wastes of hexavalent chromium, waster water takes the second place, and waste gas takes a less proportion. Besides a certain quantity of chromium element, there is also a large quantity of valuable metal in waste residue, such as iron, zinc and nickel, which should be recycled and reused as the raw material for other techniques. At present, what the steel industry applies in dealing with waste water remains the chemical methods, which should be optimized and improved; therefore, the research and promotion of a physical and biological way to deal with waste water should be accelerated, and waste gas should be purified and trapped. In terms of raw material substitution, low-chromium and free-chromium passivation technique should be developed so that the inflow of hexavalent chromium can be reduced from the source. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/21358
专题研究所(批量导入)
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GB/T 7714
王妍. 钢铁行业六价铬元素流向分析[D]. 北京. 中国科学院研究生院,2015.
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