Oxygen-assisted zinc recovery from electric arc furnace dust using magnesium chloride

Electric arc furnace(EAF)dust is an important secondary resource containing metals,such as zinc(Zn)and iron(Fe).Recover-ing Zn from EAF dust can contribute to resource recycling and reduce environmental impacts.However,the high chemical stability of ZnFe_(2)O_(4)in EAF dust poses challenges to Zn recovery.To address this issue,a facile approach that involves oxygen-assisted chlorination using molten MgCl_(2)is proposed.This work focused on elucidating the role of O2 in the reaction between ZnFe_(2)O_(4)and molten MgCl_(2).The results demonstrate that MgCl_(2)effectively broke down the ZnFe_(2)O_(4)structure,and the high O2 atmosphere considerably promoted the sep-aration of Zn from other components in the form of ZnCl_(2).The presence of O2 facilitated the formation of MgFe_(2)O_(4),which stabilized Fe and prevented its chlorination.Furthermore,the excessive use of MgCl_(2)resulted in increased evaporation loss,and high temperatures pro-moted the rapid separation of Zn.Building on these findings,we successfully extracted ZnCl_(2)-enriched volatiles from practical EAF dust through oxygen-assisted chlorination.Under optimized conditions,this method achieved exceptional Zn chlorination percentage of over 97%within a short period,while Fe chlorination remained below 1%.The resulting volatiles contained 85wt%of ZnCl_(2),which can be further processed to produce metallic Zn.The findings offer guidance for the selective recovery of valuable metals,particularly from solid wastes such as EAF dust.

Zinc leaching from electric arc furnace dust in alkaline medium

Physical and chemical properties of electric arc furnace （EAF） dust from Tianjin seamless Pipe Company were measured and analyzed. The zinc leaching tests in alkaline medium were carried out under variation of leaching agent concentration, leaching temperature, leaching cumulative time and solid-to-liquid ratio. The thermodynamics and kinetics of the zinc leaching process were also analyzed. The results show that the EAF dust contains 10% （mass fraction） zinc and the median particle size is 0.69 μm. The zinc recovery of 73.4% is obtained tinder the condition of 90 ℃, 6 mol/L NaOH, and 60 min leaching time. With the increase of concentration of NaOH and the cumulative time, zinc leaching will be significantly increased. The kinetics study demonstrates that the leaching reaction is chemically controlled and the reaction activation energy is 15.73 kJ/mol.

Extraction of Zinc from Electric Arc Furnace Dust by Alkaline Leaching Followed by Fusion of the Leaching Residue with Caustic Soda

Extractability of zinc from two types of electric arc furnace (EAF) dusts containing 24.8% and 16.8% of zinc respectively (denoted as Sample A and Sample B) were tested using direct alkaline leaching followed by fusion of the resulting leaching residues with caustic soda. The experimental results show that the extraction of zinc is heavily dependent on the contents of iron in the dusts. The higher iron content, the lower extraction of zinc is obtained. 53% and 38% of zinc can be extracted when both dusts were directly contacted with 5mol·L^-1 NaOH solution for 42h. The remaining zinc left in the leaching residues, which supposed to be present as zinc ferrites, can be further leached when the residues were fused with caustic soda. Quantitative extraction of zinc can be obtained from the leaching residue of Sample A while only 85% from Sample B. The extractability of zinc from dusts wit hvarious contents of iron is compared. The production flowsheet for zinc from the dusts using the process proposed is discussed.

Metal-doped(Cu,Zn)Fe2O4 from integral utilization of toxic Zn-containing electric arc furnace dust: An environment-friendly heterogeneous Fenton-like catalyst

Pure metal-doped(Cu,Zn)Fe2O4 was synthesized from Zn-containing electric arc furnace dust(EAFD)by solid-state reaction using copper salt as additive.The effects of pretreated EAFD-to-Cu2(OH)2CO3·6H2O mass ratio,calcination time,and calcination temperature on the structure and catalytic ability were systematically studied.Under the optimum conditions,the decolorization efficiency and total organic carbon(TOC)removal efficiency of the as-prepared ferrite for treating a Rhodamine B solution were approximately 90.0%and 45.0%,respectively,and the decolorization efficiency remained 83.0%after five recycles,suggesting that the as-prepared(Cu,Zn)Fe2O4 was an efficient heterogeneous Fenton-like catalyst with high stability.The high catalytic activity mainly depended on the synergistic effect of iron and copper ions occupying octahedral positions.More importantly,the toxicity characteristic leaching procedure(TCLP)analysis illustrated that the toxic Zncontaining EAFD was transformed into harmless(Cu,Zn)Fe2O4 and that the concentrations of toxic ions in the degraded solution were all lower than the national emission standard(GB/31574-2015),further confirming that the as obtained sample is an environment-friendly heterogeneous Fenton-like catalyst.

Recovery of zinc from electric arc furnace dust by alkaline pressure leaching using iron as a reductant

To recover zinc from electric arc furnace(EAF)dust,a process of primary normal pressure leaching and secondary alkaline pressure leaching is proposed.First,under the alkaline pressure leaching system,the experiment of pure zinc ferrite being reduced by iron powder was carried out.Under the optimal reduction conditions(i.e.,temperature of 260℃,NaOH concentration of 6 mol/L,liquid-to-solid ratio of 50 mL/g,and a 5-fold excess of iron powder),89%of zinc was extracted.The iron in the reduced residue exists as a magnetite phase.Subsequently,the normal pressure leaching experiment was carried out with EAF dust as raw material,and 66%zinc was leached.The main phase of zinc in normal leaching residue was determined to be zinc ferrite.Then,the normal leaching residue was reduced by iron powder under the alkaline pressure leaching system,and 66.5%of zinc was extracted.After the two-stage leaching process,the leaching rate of zinc in EAF dust can achieve 88.7%.The alkaline pressure leaching solution can be returned as the normal pressure leaching solution,and the magnetite in the alkaline pressure leaching residue can be recovered by magnetic separation.

A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

A novel hydrothermal process was developed to extract zinc from pure zinc ferrite（ZnFe2O4） nanopowder and zinc-containing electric arc furnace（EAF） dust using hexahydrated ferric chloride（FeCl3-6H2O） as a decomposing agent.The effects of solid FeCl3-6H2O to ZnFe2O4 ratio by mass（RF/Z）,hydrothermal reaction temperature,and time on zinc extraction were systematically investigated.In the results,when the hydrothermal reaction is conducted at 150℃ for 2 h with RF/Z of 15：20,the efficiency of zinc extraction from ZnFe2O4 reaches97.2%,and the concentration of ferric ions（Fe^3＋） in the leaching solution is nearly zero,indicating a high selectivity for zinc.In addition,the zinc extraction efficiency from the EAF dust reaches 94.5%in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl3-6H2O to EAF dust ratio by mass（RF/EAF dust） of 15：10.Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.

Heat Transfer Analysis for Industrial AC Electric Arc Furnace

The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some suggestions about decreasing heat losses were presented.

Application of Extended Kalman Filter to the Modeling of Electric Arc Furnace for Power Quality Issues

Electric arc furnaces(EAFs)represent one of the most disturbing loads in the subtransmission or transmission electric power systems.Therefore,it is necessary to build a practical model to descript the behavior of EAF in the simulation of power system for power quality issues.This paper deals with the modeling of EAF based on the combination of extended Kalman filter to identify the parameter of arc current and the power balance equation to obtain the dynamic,multi-valued u-i characteristics of EAF load.The whole EAF systems are simulated by means of power system blockset in Matlab to validate the proposed EAF model.This model can also be used to assess the impact of the new plant or highly varying nonlinear loads that exhibit chaos in power systems.

Flexible Power Supply System of AC Electric Arc Furnace

The AC electric arc furnace(EAF)is becoming a core apparatus of the modern steel industry.Nevertheless,it used to be a major threat of power quality in the traditional power supply system.In this paper,a flexible power supply system of the AC EAF is proposed,which is expected to completely alter its inherent cognition of impact load in the power grid.The basics of the power supply for EAF are first reviewed and the novel techniques to enhance the operation flexibility of EAF are introduced.The power circuit and the control structure are then presented,followed by the detailed strategies of various operations fully considering the features of EAF.A large disturbance stability criterion based on the mixed potential theory is also established for the practical application.Both electromagnetic transient simulations using PSCAD and benefit analyses verify the feasibility of the proposed system.

New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace(EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite(Zn Fe2O4), which accounts for more than half of total zinc in the EAF dust, into Zn O and Ca2Fe2O5 by Ca O addition. The EAF dust was mixed with Ca O powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All Zn Fe2O4 was transformed into Zn O and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient Ca O to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess Ca O beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than Zn Fe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when Ca O was added.

Ultrasound effects on zinc recovery from EAF dust by sulfuric acid leaching

In this work, an ultrasound-assisted leaching process was studied for the recovery of zinc from electric arc furnace （EAF） dust, in which zinc was mainly present in the form of franklinite （60%）. HydrometaUurgy is emerging as a preferred process for the recovery of a va- riety of metals, and the use of ultrasound could offer advantages over the conventional leaching process, especially for the dissolution of franklinite. Franklinite is a refractory phase that is difficult to leach and represents the main obstacle in conventional hydrometallurgy proc- essing. Atmospheric leaching with different sulfuric acid concentrations （0.2-2.0 M） at two temperatures （323 and 353 K） was performed. The tests were conducted using both conventional and ultrasound-assisted leaching. After the leaching tests, the solid residues were charac- terized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） techniques, whereas the leach liquor was analyzed by induc- tively coupled plasma spectroscopy OCP）. The use of ultrasound facilitated the dissolution of franklinite at low acid concentrations and re- suited in a greater zinc recovery under all of the investigated operating conditions.

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 800 and 1300℃. The analytic technique employed includes chemical analysis, X-ray fluores- cence 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 1000--1 100℃. At 1 100℃, 99.11% of the zinc is evaporated. The metallization ratio of Fe is 79.19% at 1300℃, 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.

Thermodynamics calculation on the oxidation and sulfur removal abilities of slag in EAF dust pellet reduction process

The valuable metals in the dust can be recycled by mixing it with reducing agent carbon and lignosulfonate as the binder to make pellets, then returning the pellets to electric arc furnace (EAF) and adding ferro silicon. Part of valuable metals in the dust is reduced by carbon and part of them reduced by ferro silicon for the economical consideration. The reduced metals get into the steel in the stainless steel or special steel production. But the sulfur in the lignosulfonate may affect the quality of produced steel, which is dependent on the status of the smelting slag. The experiments were conducted in the way of changing the ratio of start iron, pellets, ferro silicon and lime. The content of the slag was checked by XRF for the calculation thermodynamics study. The active concentrations of materials in the slag, the slag abilities of oxidation and sulfur removal in EAF dust reduction process were determined by thermodynamics calculation study on CaO MgO FeO Fe 2O 3 SiO 2 S slag at 1 550 ℃. The oxidation ability of slag can be expressed as N (FetO)= N (FeO)+6 N (Fe 2O 3)+8 N (Fe 3O 4). The sulfur removal ability is dependent on the amount of added ferro silicon and the basicity of the slag. The calculation thermodynamics model was set up and it could be applied to the practical production.

Revamping design of an EAF automatic temperature measurement and sampling robot

The function,features,and architecture of a robot that performs automatic temperature measurement and sampling applied on a 150-t AC electric arc furnace(EAF)production line of Baosteel were presented,and the key points of design and revamping experience on the site layout,device protection,lance tool,probe container,measuring position control,and system safety were summarized.Furthermore,a valuable reference for the application of automatic temperature measuring and sampling robots in EAF steelmaking plants will be provided.

Designing Evolutionary Wavelet Neural Network for Estimating Foaming Slag Quality in Electric Arc Furnace Using Power Quality Indices

In the present study,a novel approach based on an evolutionary wavelet neural network(EWNN)is proposed to estimate the slag quality in an electric arc furnace(EAF)employing power quality indices.In the EWNN,an evolutionary method is applied to train the parameters for a combination of neural networks and wavelets.I For this purpose,all of the electrical parameters for six melting processes are measured with a power quality analyzer,attached to the secondary component of an EAF transformer at a Saba steel complex,to estimate the foaming slag quality.Experimental results on various combinations of measured electrical parameters,applying the designed EWNN estimator,demonstrate that utilizing five leading indicators leads to the highest precision.The obtained 99%accuracy for estimating the foaming slag quality by EWNN compared to the other methods illustrates the proposed method's efficiency.

Technological innovations of electric arc furnace bottom-blowing in China

Nowadays, in China, the bottom-blowing technique plays an important role in accelerating the molten bath stirring and promoting the metallurgical reactions in electric arc furnace (EAF) steelmaking. The innovations of bottom-blowing technologies in EAF steelmaking were reviewed. The optimized bottom-blowing arrangement in EAF based on the furnace structure and the position of electrodes was introduced, and the fluid flow characteristics of EAF molten bath with bottomblowing were analyzed. Furthermore, bottom-blowing CO2 in EAF can facilitate the carbon-oxygen reaction reaching equilibrium and decrease the content of nitrogen in molten steel due to its special metallurgical properties. Pulsating bottom-blowing in EAF can effectively improve the molten bath stirring through the action of the unsteady bottom blowing gas streams, which could make the fluid flow field more disorderly than the steady bottom-blowing. And submerged O2 injection with CO2 in EAF can noticeably strengthen the EAF molten bath stirring, increase the production efficiency and improve the molten steel quality.

铁浴条件下电炉粉尘球团的熔融与分离行为

为了提高对含锌电弧炉粉尘(EAFD)的利用效率,实验研究EAFD球团在铁浴条件下的还原熔化行为。定义铁液滴球形度作为判断其凝聚的标准,然后探讨铁液滴直径和球形度之间随时间变化的关系。根据实验最终建立EAFD颗粒的熔化和分离行为。结果表明,在铁浴条件下,EAFD球团的Zn去除率在5.0 min时达到99%以上,但在15.0 min时金属渣分离还没有完成。由于成分的波动,在EAFD球团中形成几个区域的液态渣,然后液态渣不断增加,直到球团完全熔化。球形度>65%、直径>500μm的Fe液滴的数量随着时间的推移而减少,大直径的Fe液滴先完成分离。渣铁分离过程如下:在布朗运动下Fe液滴在渣中形成,之后Fe液滴直径在马兰戈尼效应下增加,Fe液滴在渣中下降速度符合斯托克斯定律。

大容量直流电弧炉接入对电网谐波的影响分析

大容量直流电弧炉是高功率的非线性负荷,运行时会产生大量谐波,影响电网的电能质量。基于某钢铁集团130t直流电弧炉配电网架构及参数,建立了含治理装置的大容量直流电弧炉的动态仿真模型,分析了大容量直流电弧炉的谐波发射特性及其影响因素。通过现场实测和仿真结果,分析了大容量直流电弧炉接入电网后的谐波特性,验证了静止无功补偿器(SVC)的滤波效果,为直流电弧炉接入电网后的监督和治理提供了参考。

EAF steelmaking process with increasing hot metal charging ratio and improving slagging regime

A new electric arc furnace （EAF） steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps： firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace （LF）-vacuum degassing furnace （VD） refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.