Long-Term Solidification/Stabilization and Toxicity Characteristic Leaching Procedure for an Electric Arc Furnace Dust

The effect of cure age and mix design are investigated for the stabilization of lead and cadmium in an electric arc furnace dust. Within the first year, cadmium leaching is negligible for all mix designs, whereas lead solidification/stabilization is influenced by the selection of mix design. After one year, 370-day results for lead and cadmium are nearly equal for corresponding mix designs. Furthermore, within the range of 370-day results, the rank of cadmium and lead results is the same and is established by mix design. The mix design determines the ultimate toxicity characteristic leaching procedure (TCLP) outcome, which is suspected to be the result of the extent of development of the calcium silicate phase. The comparison of TCLP data with hydroxide solubility curves indicates that extract pH values decreased with increasing cure age; TCLP results were below the hydroxide solubility curve, but they generally followed the amphoteric shape of the hydroxide solubility curve. TCLP results after 2 days of curing may be deceptive because mix designs with more binder improve with longer cure times while mix designs with less binder that are acceptable early may degrade with age.     

Stabilization of Electrical Arc Furnace Dust with Low-Grade MgO Prior to Landfill

In Spain, the stabilization of electric arc furnace (EAF) dust prior to landfill is mainly carried out using a mixture of lime and Portland cement. This paper describes the treatment of EAF dust with low-grade MgO (LG MgO) and the results are compared to those obtained with a lime and Portland cement mixture used as a stabilizer agent. The effectiveness of the treatment was assessed with leaching tests results. The use of LG MgO allows us to manage this waste as a nontoxic residue according to tests decreed by Spanish regulations. Low-grade MgO acts as a buffering agent giving the final pH mixture a value within the range of minimum heavy metal solubility.     

Understanding Environmental Leachability of Electric Arc Furnace Dust

Dust from production of steel in an electric arc furnace (EAF) contains a mixture of elements that pose a challenge for both recovery and disposal. This paper relates the leachability of six Canadian EAF dusts in four leaching tests [distilled water, Ontario Regulation 347 Leachate Extraction Procedure, Amount Available for Leaching (AALT), and pH 5 Stat] to their mineralogy. Chromium and nickel contaminants in EAF dust are largely unleachable (<5% available in AALT and pH 5 Stat), as they are found with the predominant spinel ferrite phase in EAF dust. However, even a small proportion of oxidized chromium can result in significant leachate concentrations of highly toxic chromate. The leachability of zinc (7–50% available), lead (2–17% available), and cadmium (9–55% available) can be significant, as large fractions of these contaminants are found as chlorides and oxides. The leaching of these metals is largely controlled by pH. The acid neutralization capacity of the EAF dusts appeared to be controlled by dissolution of lime and zincite, and results from regulatory leaching tests can be misleading because the variable acid neutralization capacity of EAF dusts can lead to very different final leachate pHs (5–12.4). A more informative approach would be to evaluate the total amounts of contaminants available in the long term, and the acid neutralization capacity.     

电弧炉炉尘综合处理技术及应用

从电弧炉炉尘综合治理利用的角度出发,介绍了当前国外治理电弧炉炉尘的技术和方法.详细陈述了火法、湿法以及其它方法处理电弧炉炉尘的原理,并且简述了这些工艺的可行性.     

含锌粉尘造电弧炉泡沫渣的研究

对宝钢含锌高炉粉尘、转炉二次除尘灰和电弧炉粉尘按不同配比造块与沥青焦粉混合后加入电弧炉熔渣，研究了粉尘和沥青焦加入量对炉渣发泡高度和维持时间的影响。结果表明，加入粉尘有利于炉渣发泡，炉渣中分别加入5％～10％沥青焦和20％粉尘压块时，其发泡效果最佳。     

Selective Removal of Heavy Metals from Industrial Wastewater Using Maghemite Nanoparticle: Performance and Mechanisms

This study investigated the applicability of maghemite (γ-Fe2O3) nanoparticles for the selective removal of toxic heavy metals from electroplating wastewater. The maghemite nanoparticles of 10?nm were synthesized using a sol–gel method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface area of the nanoparticles was determined to be 198?m2/g using the Brunauer–Emmett–Teller method. Batch experiments were carried out to determine the adsorption kinetics and mechanisms of Cr(VI), Cu(II), and Ni(II) by maghemite nanoparticles. The adsorption process was found to be highly pH dependent, which made the nanoparticles selectively adsorb these three metals from wastewater. The adsorption of heavy metals reached equilibrium rapidly within 10?min and the adsorption data were well fitted with the Langmuir isotherm. Regeneration studies indicated that the maghemite nanoparticles undergoing successive adsorption–desorption processes retained original metal removal capacity. Mechanism studies using TEM, XRD, and X-ray photoelectron spectroscopy suggested that the adsorption of Cr(VI) and Cu(II) could be due to electrostatic attraction and ion exchange, and the adsorption of Ni(II) could be as a result of electrostatic attraction only.     

Thermodynamic Analysis of Zinc Ferrite Decomposition in Electric Arc Furnace Dust by Lime

Scientific basis of pyrometallurgical processing technology of dusts of electric steelmaking containing zinc ferrites was investigated. The thermodynamic analysis of the decomposition of zinc ferrite with lime was carried out. The analysis of calculated data has shown that, in order to decompose more than 90% ZnFe₂O₄, it is necessary to add no less than 46% CaO for dust, while to decompose more than 95% ZnFe₂O₄, no less than 60% CaO is necessary. The results of the calculation were verified experimentally using a laboratory furnace. The experimental calcination of dust in air with the addition of lime in an amount of 60% of the dust weight at 1000°C with a holding time of 4 h confirmed that the decomposition of zinc ferrite with calcium oxide with the formation of zinc oxide and dicalcium ferrite occurs. In addition, sublimates were also formed in an amount of 50 kg per 1 t of dust containing 29% of lead and 15% of zinc. Dust calcination with lime can be applied to transform zinc from ferrite into a soluble oxide form. Intermediate products for the recovery of zinc and lead can be obtained by the calcination. After zinc leaching, it is possible to obtain an iron-containing product, which can be used in ferrous metallurgy. This approach has a series of process advantages compared with the well-known Waelz technology. In particular, calcination with lime requires lower temperature (1000°C) than the known technology (1250°C), it eliminates the second stage of the Waelz treatment necessary to purify zinc oxide fed for leaching from halides, considerably reduces coke consumption, and significantly simplifies gas cleaning from dust due to a decrease in the amount of sublimates by a factor of 6–8.     

Electrochemical Pretreatment of Wastewater from Bulk Drug Manufacturing Industry

The present study involves the treatment of high strength Bulk Drug Industry Wastewater by electrochemical method. The treatability studies were carried out with four different electrodes made of mild steel, aluminum, carbon, and stainless steel. The treatment efficiencies for chemical oxygen demand (COD)/biochemical oxygen demand (BOD), color, and heavy metal removals were assessed at different electrolysis time. A comparative study for heavy metal removal between chemical precipitation using aluminum and electrocoagulation with aluminum electrode has shown electrocoagulation to be more effective. Carbon electrode has shown COD removal of 34.0% and high BOD5f/CODf ratio of 0.581 at 120-min exposure time. Among all electrodes, aluminum was found as the most efficient in removal of color, suspended solids, and heavy metals with the least energy consumption of 95.83?Wh?kg?1?CODr and anode efficiency of 5.76?kg?COD?A?1?m?2?h?1. After electrochemical treatment, certain increase in BOD/COD ratio attributed to increase in biodegradability of wastewater. The study reveals that the wastewater could be effectively pretreated by electrochemical method.     

电炉粉尘中锌金属回收的试验研究

电炉炼钢会产生大量的电炉粉尘,多数钢铁厂把粉尘仅简单处理后填埋,造成环境和资源的双重压力。然而电炉粉尘中的铁、锌元素含量较高,具有较高的回收利用价值。针对电炉粉尘中铁锌分离、回收金属锌的可行性进行了理论分析,进而试验研究了焙烧温度、焙烧时间、不同碳/氧比对铁锌分离的影响。结果表明,当碳/氧比为1.2,焙烧温度1100℃,还原时间10min,可以得到金属化率为84.95%的球团,并且收集到金属锌。     

Carbothermic Reduction of Zinc and Iron Oxides in Electric Arc Furnace Dust

The reduction of zinc and iron oxides from electric arc furnace dust(EAFD)by carbon was investigated at temperatures between 800and 1 300℃.The analytic technique employed includes chemical analysis,X-ray fluorescence spectroscopy(XRF),X-ray powder diffraction(XRD),scanning electron microscopy(SEM)equipped with X-ray energy dispersive spectrometry(EDS),and thermodynamic database FactSage 6.2.It was found that the reduction of zinc and iron oxides depends largely on Boudouad reaction.At 900 ℃,zinc exists in tested samples as ZnO,which is reduced in the temperature range of 1 000-1 100℃.At 1 100℃,99.11% of the zinc is evaporated.The metallization ratio of Fe is 79.19% at 1 300℃,as the content of Fe2+ is still 9.40%.A higher temperature is thus required for a higher reduction degree of Fe oxides by solid or gaseous carbon.     

电炉除尘兼余热回收系统的设计与应用

为满足可持续发展的要求,莱钢自行研制并设计了电炉除尘兼余热回收装置,且在50 t超高功率电弧炉上得到成功应用。该系统在满足环境净化要求的同时,利用收集的烟尘热量生产出高温高压蒸汽,满足了VD生产和职工生活的需要,为国内电炉节能降耗和清洁生产进行了有益的探索,填补了国内电弧炉余热利用的空白。     

新日铁的转底炉法粉尘回收系统

新日铁君津制铁所从2000年开始采用了转底炉法(RHF)回收利用粉尘的技术.将含有氧化铁和碳的尘泥进行氧化铁的高温还原,尘泥中的锌及其它杂质则被去除并排放到废气中,生产的直接还原铁(DRI)球团金属含量达70%,可以作为高炉原料.2000年5月开始运行的1号机采用造球机造粒,主要用于干粉尘的回收利用;2002年12月开始运行的2号机采用压块成形方式,主要用于泥浆的回收利用.综合使用这两种设备,可以解决大型钢铁企业所排出的各类尘泥的回收利用问题.     

2号高炉干法除尘系统集中卸灰改造

针对炼铁厂2号高炉干法除尘系统加湿卸灰所带来的二次扬尘现象，提出了集中卸灰改造的方案，并对改造方案的可行性和改造费用情况作了探讨，同时阐述了改造的实施过程和改造后的操作要求。     

Thermal Analysis on the Pyrolysis of Tetrabromobisphenol A and Electric Arc Furnace Dust Mixtures

The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both materials with varying TBBPA loads (1:1 and 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at heating rates of 5 and 10 °C/min. The mixtures degraded through several steps, including decomposition of TBBPA yielding mainly HBr, bromination of metal oxides, followed by their evaporation in the sequence of CuBr₃, ZnBr₂, PbBr₂, FeBr₂, MnBr₂, KBr, NaBr, CaBr₂, and MgBr₂, and finally reduction of the remaining metal oxides by the char formed from decomposition of TBBPA. Thermodynamic calculations suggest the possibility of selective bromination of zinc and lead followed by their evaporation, leaving iron in its oxide form, while the char formed may serve as a reduction agent for iron oxides into metallic iron. However, at higher TBBPA volumes, iron bromide forms, which can also be evaporated at a temperature higher than those of ZnBr₂ and PbBr₂. Results from this work provide practical insight into selective recovery of valuable metals from EAFD while at the same time recycling the hazardous bromine content in TBBPA.     

30t电炉冶炼不锈钢除尘红泥球的实践

使用电炉将不锈钢除尘灰熔化还原,实现了不锈钢除尘友内的贵重合金元素Ni、Cr、Mn等的回收使用,也避免了不锈钢除尘灰对环境的二次污染。     

闪速炉烟尘系统的三期改造

介绍贵溪冶炼厂闪速炉烟尘系统三期改造的思路及实践。     

Analisys of Electric Arc Furnace Slag

The black slag produced during the melting process in electric arc furnace can be used as adjunct in the operation of land filling, building operation of road grounds, and production of concrete. Their use limitation is due to the presence of polluting chemical elements, including Cr, Ba, V, Mo, etc, that can be dangerous for human and environment, resulting by using of polluted scraps (i.e., painted, lubricated, or polymeric compound scraps). The release extent of polluting elements appears to behave as a function of the constituent phases, i.e., CaO, SiO₂, Al₂O₃, MgO, etc. The main tools employed in the characterization of the black slag consists in optical basicity calculation, SEM‐EBS and SEM‐EDS analysis. The combination of the data coming from chemical analysis, micro‐structural examination and releasing tests allows to identify the correct chemical range avoiding dangerous chemical release and to develop a working disposal procedure for the investigated slag.     

智能炼钢电弧炉技术

介绍３种智能电弧炉技术,分析了智能电弧炉的技术特点,讨论了我国发展智能电弧炉技术应注意的问题。     

超高功率电弧炉技术概况

电弧炉炼钢的迅速增冶金力工艺操作的发展密切相关，这些进展包括炉子容量最佳化，超高功率（ＵＨＰ）操作，炼钢车间和炉子的改造，ＵＨＰ电炉相关技术的，直流（ＤＣ）电弧炉技术和电弧炉熔炼工艺的根本变革。文中同时介绍和讨论了我国ＵＨＰ电弧炉的进展。     

电弧炉炼钢技术进展

回顾了电弧炉炼钢发展的概况,讨论了中国电弧炉炼钢发展面临的主要问题和机遇,重点分析了电弧炉炼钢的工艺改进和高效化技术发展,并从高效率、高质量、低能耗、低排放、可持续发展的角度出发对电弧炉炼钢流程的工艺装备和技术发展给出了新总结,并提出了发展前瞻性建议。