Energy-efficient reduction of iron from its ores

Terra thermodynamic-modeling software is used to investigate the solid-phase reduction of iron, in two stages: (1) reduction in an elementary model system; (2) reduction of iron from ore by coal. In the first stage, analysis of the redox conditions in the Fe–C–O system permits determination of the boundaries of the reductive, transition, and oxidative regions and the corresponding values of the oxygen/carbon ratio. Analysis of the reducing properties of coal by calculating the equilibrium compositions in the range 373–1873 K on the basis of Terra software shows that, within that range, the gas composition is practically the same for all the types of coal considered; only the content of volatiles is different. Sharp increase in gas volume begins at 673 K and ends at 1073 K. In the second stage, thermodynamic modeling permits the determination of the optimal consumption of poorly clinkering SS coal, long-flame D coal, and 2B lignite for complete reduction of iron from ore of specified composition.     

两步三段式厚渣层铁浴熔融还原炼铁工艺

针对目前熔融还原设备无法将煤气二次燃烧氧化区与铁氧化物还原区隔离而导致能耗偏高的问题,提出了一种两步三段式厚渣层铁浴熔融还原炼铁工艺,以期利用厚渣层冶炼的方法使得氧化区与还原区的梯度隔离。设计了主反应器铁浴炉尺寸与产能,并建立了工艺的整体静态模型,考察了球团金属化率与铁浴炉炉顶煤气氧化度对工艺煤耗、氧耗以及能耗的影响。在选定的适宜操作参数,即煤气氧化度55%,球团金属化率80%条件下,冶炼1t铁水,消耗球团矿1 869.83kg,煤粉674.07kg,同时得到还原度71%的改质煤气898.44kg。结合反应器的设计产能,反应器可处理球团矿3 793.66kg/(h·m2)。     

Kinetics of smelting reduction of fluxed composite iron ore pellets

Kinetic studies on smelting reduction of unreduced fluxed composite pellets (FCP) and fluxed composite pre-reduced iron ore pellets (FCRIP) have been carried out in an induction furnace. The pellets are charged into the slag layer floating on the carbon saturated molten iron bath in a graphite crucible. The slag basicity was however varied such that it has the same value as that of the pellets charged. The temperature of the slag is varied within the range of 1623K to 1823K for the pellets of basicity 2.0. Kinetic studies show a mixed kinetic model of both diffusion and chemical reaction controlled. While the smelting of FCRIP follows the model expressed as G(or) = 1-(2/3)(α) -(1-α)^2/3, the unreduced FCP pellets initially follow the diffusion controlled model of G(α) = α² followed by a chemical reaction controlled first order model of -ln(1-α) at the latter stages of smelting reduction, where α denotes the degree of reduction. The basicity dependence on the kinetics is not very significant. Comparison of the activation energy values explains that the smelting reduction with pre-reduced pellets seems to be a rather less energy intensive process.     

熔融还原炼铁技术发展情况和未来的思考

由于全球钢铁冶炼资源的变化和环保要求的提升,非高炉炼铁技术越来越受到业界人士的高度关注。近年来,在非高炉炼铁领域,新工艺、新技术层出不穷,结合这些新的前沿技术,特别是重点介绍几种有产业化前景的熔融还原技术（COREX、FINEX、HIsmelt）,并结合宝钢集团在COREX-3000的生产操作实践、探索与创新,较客观地指出了熔融还原炼铁技术目前存在的不足和缺陷,并结合宝钢在这些方面的实践,提出未来发展熔融还原炼铁技术需要关注的内容。     

Reaction mechanism on the smelting reduction of iron ore by solid carbon

The kinetics of the smelting reduction of iron ore by a graphite crucible and carbon-saturated molten iron was investigated between 1400 °C and 1550 °C, and its reaction phenomena were continuously observed in situ by X-ray fluoroscopy. In the smelting reduction by graphite, it was shown from the observation results that the smelting reduction reaction proceeded by the following two stages: an initial quiet reduction without foaming (stage I) and a following highly active reduction with severe foaming (stage II). At 1500 °C, by the graphite crucible, the reduction rate of iron ore was found to be 8.88×10⁻⁵ mol/cm² · s, and by the molten iron, 8.25×10⁻⁵ mol/cm²·s. The activation energies for the reduction by the graphite crucible and the molten iron were 24.1 and 22.9 kcal/mol, respectively. Based on the results of kinetic research and X-ray fluoroscopic observations, it can be concluded that these two types of smelting reduction reactions of iron ore by the graphite crucible and by the molten iron are essentially the same.     

碱度对转炉钢渣熔融还原提铁的影响

为了使熔融钢渣的"渣"和"热"得到双利用,采用熔融还原法进行了钢渣提铁实验,探讨了二元碱度对还原提铁的影响.结果显示随着碱度的增大铁的回收率及金属化率呈先升后降的趋势,在碱度1.1时铁的回收率和金属化率达到最大,分别为95.8%和99.2%.与炼钢用生铁国标相比,回收的铁块中C、Si、Mn的含量较低,而S、P含量远远高于炼钢用生铁.     

贫化铜渣熔融还原提铁试验研究

研究以贫化铜渣为对象,首先对贫化铜渣熔融还原进行理论分析,并进行试验考察炉渣碱度、碳氧比、冶炼时间和冶炼温度四个因素对铜渣中铁元素回收率的影响。试验结果表明,(1)贫化铜渣熔融还原提铁合理的试验参数为:铜渣碱度0.3~0.5,碳氧比为1.15~12,冶炼温度为1 500~1 550℃,冶炼时间为40~45 min;(2)在合理试验参数下,铁元素回收率在90%以上,铜元素全部进入金属相;(3)试验获得了铁含量88%~90%,铜含量4.2%~4.6%的含铜铁,可望用于耐候钢等舍铜钢种的冶炼。尾渣中SiO2含量高达50%以上,可使用制备矿物棉等高附加值产品,从而实现铜渣资源的全部高附加值利用。     

Heat transfer in an iron bath of a two-stage smelting reduction process

Mechanisms of the heat transfer by means of iron and slag drops in smelting reduction are discussed. The quantity of slag on the molten iron exists in two forms depending on the different processes: either a thin slag layer or a voluminous slag layer. In the case of a small amount of slag, iron and slag drops are spattered in the free space above the bath furnace. By smelting reduction with a high post-combustion degree, the spattered iron drops are quickly oxidized in the free space. The spattered slag drops transfer heat from the free space to the molten iron. A definition for the heat transfer efficiency in the iron bath of a two-stage smelting reduction process is presented. Experiments on heat transfer were made in an experimental EOF-furnace with 100 kg iron. The post-combustion degree and the heat transfer efficiency were on a high level, because inleaked air was used.     

Fluidized bed reduction as the prestep of smelting reduction

Comparing the four fundamental ironmaking processes the reasons for the development of smelting reduction were derived. Based on bibliographical references a fundamental classification of the main important smelting reduction processes is presented regarding the process engineering principle of both steps, prereduction and final reduction. According to fundamental considerations, the fluidized bed process seems to be optimal for prereduction. Experiments to investigate the influence of process parameters on sticking – the main problem of fluidized-bed reduction – and their interactions were carried out. Optimal operating conditions to run a fluidized bed as the prereduction unit of smelting reduction process were derived. A special “Reduction-SEM” to directly observe metallurgical reactions, like the precipitation behaviour of iron during iron ore reduction, is presented. With the results of such investigations it is possible to show the influence of precipitation behaviour on sticking and to assign the different types of precipitates to the Baur-Glaessner-Diagram. The influence of hydrogen addition on surface morphology is sketched out.     

硫酸铈滴定法测定铁矿中铁

提出在HCl介质中,以抗坏血酸还原铁 ,残余的抗坏血酸以次甲基蓝为指示剂,硫酸铈氧化,然后在硫 磷混酸介质中,以二苯胺磺酸钠为指示剂,硫酸铈标准溶液滴定铁 。大多数常见离子不干扰铁的测定,氟的干扰可用硼酸消除。本方法简便、快速,用于铁矿中铁的测定,结果满意。     

Concept and present state of a coal-based smelting reduction process for iron ore fines

The concept of a two-stage smelting reduction process is presented. In the first stage highly metallized iron ore fines are produced in a circulating fluidized bed. In the second stage a hot metal is produced in a melter-gasifier where – together with metallized ore – coal and oxygen are injected to generate the required heat and the CO-rich reducing gas. The process was tested stepwise in pilot scale installations. Although only a reduction temperature of 830 °C instead of the required 880–900 °C could be realized in the pilot unit, test results make it very probable that a metallization of 90% can be reached with any fine ore without sticking problems, if the ore is covered with a carbon layer by CO decomposition in a pretreatment stage with the reduction offgas at 500–600 °C. The CO decomposition on the fresh ore leads to a high gas utilization which renders a CO₂ washing stage and gas recycling unnecessary. To prove the technical and economic feasibility of the combined process, the next development step should be the design and operation of a larger pilot plant with a capacity of at least 5 t hot metal/h for continuous and joint operation of both the melter/gasifier and the reduction stage.     

Fundamental studies related to the development of the smelting reduction of iron oxide and carbon-constant volume studies

Abstract

Today, most of the iron-making capacity of the world is still dependent upon the blast furnace process, although the production of sponge iron by direct reduction processes is gaining acceptance in many areas. Another method of making iron, known as smelting reduction, is receiving attention, and pilot-plant scale operations are being developed in Europe and possibly elsewhere. In this method, iron oxide is reduced with carbon (coal) by a fast reaction such that liquid iron is the product, heat being provided to the reaction by the exothermic oxidation of carbon monoxide by oxygen within the reaction vessel.

In the present investigation, an attempt has been made to study the behaviour of composite pellets of wüstite and carbon in the region of 1500°C in various gas atmospheres at constant volume. Reaction rates were followed within the constant-volume system by measuring the increase in pressure with time using a pressure transducer. Composite pellets containing slightly more than the stoichiometrically required amount of carbon were reacted to form liquid iron in an argon atmosphere; to achieve melting, good mixing of the pellets was a critical requirement. Melting conditions were also obtained in carbon monoxide-carbon dioxide mixtures between 100 per cent CO and 100 per cent CO₂ When composite pellets, surrounded by a protective layer of carbon, were introduced into an atmosphere containing free oxygen, it was again possible to obtain melting and reduction to liquid iron. The activation energy for the reaction was approximately 15 kcal/mole. Possible reaction mechanisms are discussed.

Résumé

De nos jours, la réduction des oxydes de fer s'accomplit en grande partie au haut foumeau. On note toutefois une implantation graduelle des procédés de réduction directe des oxydes en fer éponge. Une autre méthode de production du fer, connue sous Ie nom de smeltage réducteur, est actuellement à l'étude. Des essais à l'échelle de l'usine pilote se font actuellement en Europe et possiblement ailleurs. La méthode consiste à produire du fer liquide en réduisant rapidement l'oxyde de fer par du carbone. L'énergie requise pour la réaction vient de l'oxydation exothermique du monoxyde de carbone par l'oxygène présént dans l'enceinte réactionnelle.

Les auteurs ont étudié le comportement de boulet1es composées de wüstite et de carbone en présence de diverses atmosphères gazeuses dans une enceinte fermée à 1,500°C. Les vitesses de réaction ont été détérminées en mesurant l'augmentation de la pression dans l'enceinte au moyen d'un transducteur de pression. Des boule1tes composées comportant un peu plus que la quantité stoechiométrique de carbone ont été réduites en fer liquide dans une atmosphère d'argon. La fusion n'avait lieu que si les constituants des boulet1es étaient intimement mélangés. La fusion de boulet1es a été réalisée dans des atmosphères constituées de melanges CO-CO₂, les proportions variant entre 100% CO et 100% CO₂. Le fer liquide a aussi été obtenu en faisant réagir des boulettes d'oxyde et de carbone entourées d'une couche protectrice de carbone, dans une atmosphère contenant de l'oxygène libre. L' énergie d'activation de la réaction était d'environ 15 kcal/mole. En fin, les auteurs discutent des mécanismes de la réaction.     

Oxide nickel ores smelting of ferronickel in two-zone Vaniukov Furnace

Abstract

Gipronickel Institute is developing a brand new process of Kempirsay Deposit’ nickel oxide ore treatment to ferronickel based on Vaniukov Furnace smelting technology. Results of the extended laboratory scale tests using the pilot Vaniukov two-zone Furnace are presented. It is demonstrated that treatment of relatively poor nickel oxide ore (Ni, 1·05 mass-%) according to the abovementioned technology can result in production of high grade ferronickel (Ni?20%) at high nickel recovery (>90%). Technological peculiarities of the processes taking place in the furnace’ smelting and reduction areas are considered.

L’Institut Gipronickel est en train de développer un procédé entièrement nouveau pour le traitement du minerai d’oxyde de nickel en ferronickel du dépôt de Kempirsay, basé sur la technologie de fonte du four Vaniukov. On présente les résultats des essais approfondis à l’échelle du laboratoire utilisant le four pilote Vaniukov à deux zones. On démontre que le traitement de minerai d’oxyde de nickel à teneur relativement faible (1·05% en masse de Ni) peut aboutir, d’après la dite technologie, en une production de ferronickel de haute qualité (?20% de Ni) avec récupération élevée du nickel (>90%). On considère les particularités technologiques des procédés qui ont lieu lors de la fonte dans le four et dans les zones de réduction.     

Gaseous reduction of laterite ores

Lateritic nickel ores have been reduced under laboratory conditions. The reduction experiments were carried out at temperatures from 500 °C to 1100 °C in a horizontal tube furnace using various mixtures of H₂ and CO₂. The hydrogen evolution method was used to measure the degree of metallization of the reduced ore. It was found that the rate of reduction was very low at 500 °C but then increased rapidly upon heating the ore to 600 °C. The percent metallics increased with increasing H₂ to CO₂ ratios in the reducing gas. At temperatures between 600 °C and 1100 °C, a H₂ to CO₂ ratio of 3 leads to the formation of 5 to 6 pct metallics in the reduced calcine was shown. Heating the ore in air or nitrogen prior to reduction does not affect the degree of metallization. A H₂ to CO₂ ratio of at least 4 is required to obtain a ferronickel product analyzing 36 pct nickel if no further reduction is carried out during the subsequent smelting operation.     

Conclusions on the development of smelting reduction

The present paper summarizes the results of the US-German Symposium on “Innovative Iron and Steel Making Processes”. A survey is given on the state-of-the-art technology as well as the state and further needs of research.     

Investigation on the effect of Zn on the behaviour of S in the iron bath smelting reduction process

A computer program system was developed to simulate the smelting reduction ironmaking process. In this study, the effects of zinc, temperature, and post combustion ratio of the gas generated from the smelting reduction furnace on the behaviour of sulphur in the iron bath smelting reduction process were investigated from the thermodynamic point of view. The simulated results indicated that even a very small amount of zinc could introduce sulphur into the dust in the form of ZnS, which would effectively prevent the sulphur from entering the outlet gas. Moreover the deposited ZnO would accumulate continuously in the system in case of all dust being recycled.