铝灰综合利用的技术进展

综合利用铝灰对于回收资源,改善环境,提高经济效益,实现资源优化配置和可持续发展都具有重要的意义.本文介绍了国内外铝灰综合应用的研究进展.     

二次铝灰水解渣分质利用研究

二次铝灰是一次铝灰回收金属铝产生的危险废物,我国二次铝灰年排放量超过400万吨,目前通常采用水解技术进行脱氮预处理,但水解渣利用难度较大.针对上述问题,本文提出了二次铝灰水解渣温和碱溶-稀酸除杂-成型烧结回收活性铝并制备耐火材料骨料的利用工艺,系统考察了温和碱溶过程和稀酸除杂过程中反应时间、温度、浓度等因素对铝溶出率以...     

从铝灰中回收铝制备超细氧化铝粉体过程研究

电解生产铝的过程中产生大量铝灰、铝渣,作废渣弃去,既污染环境又造成铝资源浪费.本文介绍了一条回收铝灰中的铝制备氧化铝粉体的新工艺.用硫酸浸取铝灰,使之转化为硫酸铝溶液,铝浸出率达95%以上;硫酸铝与碳酸氢铵反应生成前驱体碳酸铝铵沉淀和硫酸铵溶液,过滤、洗涤、煅烧碳酸铝铵得氧化铝扮体.所得产品经过XRD和SEM等方法检测为60mm的α-Al_2O_3.过程无废气、污水、新的废洼排放.     

废铝再生熔炼中铝渣的回收处理工艺进展

铝渣是废铝再生熔炼时不可避免的副产物,含有大量的金属铝、氧化铝、氮化铝、熔盐混合物及其他组分。对铝渣的回收处理能提高铝生产企业的经济效益并减少环境污染。综述了铝渣中金属铝的热、冷回收处理工艺以及后续铝灰中有价成分的化学法、高温法再利用技术现状,铝渣中金属铝回收工艺主要包括盐浴翻炒法、压榨法、搅拌法、离心法等热法处理工艺和破碎筛分法、电选法等冷法处理工艺;后续铝灰中有价成分再利用技术主要包括预处理工艺、化学法、高温法等再利用技术,并对国内外研究动态与发展趋势进行了分析和展望。     

废铝再生熔炼中铝渣的回收处理工艺进展

铝渣是废铝再生熔炼时不可避免的副产物,含有大量的金属铝、氧化铝、氮化铝、熔盐混合物及其他组分。对铝渣的回收处理能提高铝生产企业的经济效益并减少环境污染。综述了铝渣中金属铝的热、冷回收处理工艺以及后续铝灰中有价成分的化学法、高温法再利用技术现状,铝渣中金属铝回收工艺主要包括盐浴翻炒法、压榨法、搅拌法、离心法等热法处理工艺和破碎筛分法、电选法等冷法处理工艺;后续铝灰中有价成分再利用技术主要包括预处理工艺、化学法、高温法等再利用技术,并对国内外研究动态与发展趋势进行了分析和展望。     

铝灰的回收利用现状及发展趋势

铝灰中含有金属铝及其它有价成分,文章对国内铝灰的回收处理方法、发展趋势及二次铝灰、弃灰的利用作了简要介绍.     

铝灰处理工艺研究

铝熔炼过程中产生的铝灰含铝量大约在45%-50%,有很高的利用价值。通过实验证明了通过铝灰热处理、球磨、中频炉熔炼等工艺,可回收铝灰中大部分金属铝,并将低含铝量的铝灰做成电解铝用阳极钢爪保护环,使铝灰循环利用,充分开发了铝灰的价值,减少了铝灰对环境的污染,并收到了较好的经济效益。     

铝废料回收重熔过程中的铝灰

据有关资料报道美国能源部在其2004年年度报告<铝--未来的工业>中指出:铝灰(Aluminium dross)--美国铝废料回收再生过程中的最大损失.在铝废料回收重熔过程中有4%的铝废料由于氧化而损失.为此美国每年损失的铝数量达44万吨.过去30年中对许多重熔厂和铸造车间的调查揭示出:大多数熔炼铸造车间的设计和生产都是采用固定的熔炉,其位置要比直接冷硬铸造机位置水平要高出一些,要求铝水从一个水平到另一个水平呈阶梯式布置.因而在每次排放铝水时就会产生相当可观的数量铝灰.另外,在不合适的炉门处也造成铝的损失.     

铝灰综合回收利用的国内外技术现状及趋势

铝灰是一种可回收利用的铝工业副产品,综合回收利用铝灰可节约资源,改善环境,提高经济效益。本文详细介绍了铝灰综合回收利用的国内外技术现状,特别是从铝灰中回收铝及用铝灰制备各种材料,展望了铝灰的综合利用前景。     

铝灰综合回收利用的研究现状与进展

铝灰作为一种工业副产品,具有潜在的高价值。分析了铝灰的成分及分类,介绍了铝灰中有价值成分的回收以及铝回收设备的改进,阐述了国内外铝灰的应用,总结并展望了铝灰回收利用的发展趋势。     

Process of aluminum dross recycling and life cycle assessment for Al-Si alloys and brown fused alumina

In 2008, around 596 000 t of aluminum dross was generated from secondary aluminum industry in China; however, it was not sufficiently recycled yet. Approximately 95% of the Al dross was land filled without innocent treatment. The purpose of this work is to investigate Al dross recycling by environmentally efficient and friendly methods. Two methods of Al dross recycling which could utilize Al dross efficiently were presented. High-quality aluminum-silicon alloys and brown fused alumina (BFA) were produced successfully by recycling Al dross. Then, life cycle assessment (LCA) was performed to evaluate environmental impact of two methods of Al dross recycling process. The results show that the two methods are reasonable and the average recovery rate of Al dross is up to 98%. As the LCA results indicate, they have some advantages such as less natural resource consumption and pollutant emissions, which efficiently relieves the burden on the environment in electrolytic aluminum and secondary aluminum industry.     

铝灰渣中AlN水解行为及其多元非线性回归分析

通过对铝灰渣水解反应过程中组分及其含量变化的研究,提出铝灰渣中AlN含量的修正公式;根据AlN含量和悬浊液pH值的测定,考察时间、温度、转速等水解参数对AlN水解速率的影响并对其进行多元非线性回归分析。结果表明:升高温度能降低铝灰渣中AlN含量并降低悬浊液pH值;延长时间可有效促进AlN的水解,同时在2h内悬浊液pH值迅速提升至高位;转速对AlN水解速率和悬浊液pH值无明显影响。总体而言,AlN含量比悬浊液pH值更能客观表征铝灰渣中AlN水解速率。对水解参数及修正后铝灰渣中AlN含量进行多元非线性回归分析并二次简化,发现理论值与实验值相对误差≤±8.65%。     

Dross treatment in a rotary arc furnace with graphite electrodes

Aluminum baths are always covered with a layer of dross resulting from the aluminum surface oxidation. This dross represents 1–10% of the melt and may contain up to 75wt.% aluminum. Since aluminum production is highly energy intensive, dross recycling is very attractive from both energy and economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally unacceptable because of the production of salt slags. Hydro-Quebec has developed a new technology using a rotary arc furnace with graphite electrodes. This process provides aluminum recovery rates of 80–90%, using a highly energy efficient, environmentally sound production method.     

Processing of Aluminum Dross: The Birth of a Closed Industrial Process

This is the history of a modern aluminum dross recycling company, from its beginnings in the last years of the twentieth century to the present day. The vision of the founders was to build a local recycling plant and take full responsibility for sensitive environmental issues by recycling aluminum dross locally rather than shipping it abroad. The paper tells the history of the company from the environmental perspective, and gives an overview of some of the challenges and the decisions that followed from this vision, for instance the selection of technology. The company developed a closed industrial process for the recycling of aluminum dross, and the paper discusses some of their laboratory experiments and industrial trials. An important milestone has now been reached as the process in its present form is recognized by the environmental authorities in the country. Furthermore, it seems realistic that in the near future the final product from this process will be comparable to the product delivered in the processing of salt cake in specialized chemical plants, but at a fraction of the cost.     

Recovering aluminum from aluminum dross in a DC electric-arc rotary furnace

The recycling of aluminum scrap and dross yields significant economic and energy savings, as well environmental benefits. The recovery of aluminum depends on many factors. The aim of this work is to experimentally investigate aluminum recovery under different conditions. In this study, aluminum dross was processed in a direct-current electric-arc rotary furnace. The presence of crushing refractory bodies during processing was found to increase the degree of aluminum recovery by about ten percent.     

The Nondestructive Determination of the Aluminum Content in Pressed Skulls of Aluminum Dross

During production of primary and secondary aluminum, various amounts (in some cases up to 200 kg) of aluminum dross, a mixture consisting of molten aluminum metal and different oxide compounds (the nonmetallic phase), are skimmed per tonne of molten metal. To preserve the maximum aluminum content in hot dross for further extraction, it is necessary to cool the dross immediately after skimming. One way to do this is to press the skimmed hot dross in a press. In this process, the skimmed dross is transformed into so-called pressed skulls, with characteristic geometry convenient for storage, transport, or further in-house processing. Because of its high aluminum content—usually between 30% and 70%—pressed skulls represent a valuable source of aluminum and hence are in great demand in the aluminum recycling industry. Because pressed skulls are generally valued on a free-metal recovery basis, which is influenced by the yield of recovery, or in other words, by the quality of the recycling process, it was recognized as important and useful to develop a method of fast and cost-effective nondestructive measurement of the free aluminum content in pressed skulls, independent of the technology of pressed skulls recycling. In the model developed in this work, the aluminum content in pressed skulls was expressed as a function of the pressed skulls density, the density of the nonmetallic phase, and the volume fraction of closed pores. In addition, the model demonstrated that under precisely defined conditions (i.e., skulls from the dross of the same aluminum alloy and skimmed, transported, cooled, and pressed in the same way and under the same processing conditions), when other parameters except the pressed skulls density remain constant, the aluminum content in pressed skulls can be expressed as a linear function of the pressed skulls density. Following the theoretical considerations presented in this work, a practical industrial methodology was developed for nondestructive prediction of the amount of free aluminum in pressed skulls w _Al, based on nondestructive measurement of the density ρ of the pressed skulls. The pressed skulls density is measured by a fully automatic gas displacement pyknometer with a working volume large enough to enable the insertion of the whole pressed skull sample. An additional integral part of this methodology is the set of experimentally determined linear graphs w _Al-ρ, plotted in advance for all classes of pressed skulls existing in the plant, from the experimentally collected data on pressed skulls density and aluminum recovery by melting. After selecting the proper graph w _Al-ρ, which is usually performed on an aluminum alloy basis, the pyknometric measured density of the pressed skulls can be routinely related to the aluminum content sought, within a relative error of ±5%.     

Melting standardized aluminum scrap: A mass balance model for europe

Although individual aluminum recycling companies have good knowledge of scrap in terms of its characteristic metal yield during melting, an overall view of this industry is still missing. An aluminum mass balance for the aluminum recycling industry in the European Union member states from 1995 to 2004 (EU-15) has been carried out. The objective was to increase the transparency of the complex recycling system and to determine how resource-conservative the industry is when melting aluminum scrap. Results show that in 2002, about 7 million tonnes of purchased, tolled, and internal scrap—with a metal content of 94%—were recycled in the EU-15. By comparing the net metal input to the final product, the study finds a very respectable metal recovery rate of 98%. For more information, contact M. Bertram, European Aluminium Association and Organisation of European Aluminium Refiners and Remelters, 12 Avenue de Broqueville, Brussels, Belgium; +32-2-775-63-61; fax +32-2-779-05-31; e-mail bertram@eaa.be.     

Recycling of lead solder dross,Generated from PCB manufacturing

The main purpose of this work is to analyze lead solder dross, a waste product from manufacturing of printed circuit boards by wave soldering, and to develop an effective and environmentally sound technology for its recycling. A methodology for determination of the content and chemical composition of the metal and oxide phases of the dross is developed. Two methods for recycling of lead solder dross were examined—carbothermal reduction and recycling using boron-containing substances. The influence of various factors on the metal yield was studied and the optimal parameters of the recycling process are defined. The comparison between them under the same parameters-temperature and retention time, showed that recycling of dross with a mixture of borax and boric acid in a 1:2 ratio provides higher metal yield (93%). The recycling of this hazardous waste under developed technology gets glassy slag and solder, which after correction of the chemical composition can be used again for production of PCB.     

Extracting aluminum from dross tailings

Aluminum dross tailings, an industrial waste, from the Egyptian Aluminium Company (Egyptalum) was used to produce two types of alums: aluminum-sulfate alum [itAl₂(SO₄)3.12H₂O]and ammonium-aluminum alum [(NH ₄)2SO₄AL₂(SO₄)3.24H₂O]. This was carried out in two processes. The first process is leaching the impurities using diluted H₂SO₄ with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of solute sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purifi ed aluminum dross tailings thus produced. The effects of temperature, time of reaction, and acid concentration on leaching and extraction processes were studied. The product alums were analyzed using x-ray diffraction and thermal analysis techniques.