Kinetics of chloridization of nickel oxide with gaseous hydrogen chloride

The kinetics of chloridization of finely divided as well as granulated nickel oxide by gaseous HCl were studied in the temperature range 150 °C to 400 °C. The rate of chloridization depended upon temperature, partial pressure of HCl, and granule size. The conversion of NiO to NiCl₂ follows the logarithmic rate law or a pore-blocking model, which is attributed to the large increase in molar volume of the product phase. The blocked pores decreased the diffusion of gaseous reactant through the product layer. This observation has been supported by the low value of activation energy, the high order of reaction with respect to the partial pressure of HCl (g), and a slope value of −2 for the log-log plot of rate constant vs grain size. The morphological characteristics of both unreacted and chloridized nickel oxide have been studied with the help of a scanning electron microscope.     

铁矿石等温气固还原动力学研究

将未反应核模型拓展应用于烧结矿气相还原,采用四阶龙格库塔法通过编制程序求解混合控制方程.通过数值计算与实验数据的对比,证明烧结矿的气固还原过程和球团矿一样可以用未反应核模型来描述.烧结矿形状不规则,不具有明确的半径,通过与前人研究的比较,本文摒弃了传统处理中的平均半径选取,利用数据分析得到了适用于烧结矿的等效半径,解决了烧结矿应用未反应核模型时的半径选取问题,为铁矿气固还原动力学的研究提供了新的参考.     

炉腹煤气中氢含量对铁矿石滴落过程的影响

利用高温熔滴炉对喷吹富氢煤气后高炉炉料的熔滴性能进行实验研究,XRD检测技术对喷吹富氢煤气后炉料的还原情况进行分析,并利用相图原理分析了不同富氢量对滴落带的影响。结果表明:喷吹富氢煤气后,矿石在进入滴落带之前,铁的氧化物已经大量被还原,滴落温度升高,滴落区间变窄。初渣渣量减少使得高炉透气性改善,最大压差与总特性值逐渐变小。结合滴落物与坩埚内剩余物的物相检测,得出富氢煤气对高炉熔滴性能的影响规律和最佳富氢量。     

Bioleaching of lateritic nickel ore by ultrasound

The bioleaching of nickel from lateritic ore of Orissa, India, using a nativeAspergillus niger strain was studied with and without ultrasound. Different parameters, such as spore concentration, amount of dextrose in the medium, pulp densities, and sonication time, were studied for maximizing the extraction of nickel. Enhanced recoveries and reduction in leaching time were demonstrated using ultrasound. The highest amount of nickel, 95 pct, was extracted in 14 days with an inoculum size of 10⁶ spore/mL and 2 pct dextrose in the medium under 30 minutes ultrasonic pretreatment using 43 KHz frequency at 1.5 W/cm² intensity. It was also found that ultrasound assists in selective leaching of nickel over iron.     

铁精粉氧化过程的动力学研究

通过恒温和均匀升温实验,采用大载荷热重分析仪研究了铁精粉氧化过程动力学.结果表明:均匀升温过程中,铁精粉氧化的主要控制环节变化是外扩散型→内扩散型→外扩散型,氧化结束后,部分Fe₂O₃发生分解反应生成Fe₃O₄和O₂,使得TG曲线质量变化率减小;等温实验也证明了氧化主体部分的控制环节是内扩散,其表观活化能为26.193kJ·mol^-1;铁精粉氧化过程促进了钛元素富集,改变了产物的微观结构.     

铁尾矿碱浸出过程动力学

以铁尾矿为原料,研究了矿中SiO2的NaOH浸出过程,确定了铁尾矿用碱（NaOH）浸出过程中,影响SiO2浸出率的主要因素为：铁尾矿和NaOH与水的固液比,浸出反应温度,浸出反应时间．以此为条件,研究了铁尾矿在碱溶液中浸取SiO2反应的动力学行为．结果表明：铁尾矿中SiO2浸出的最佳因素为,固液比1：2,反应温度110℃,反应时间6h．SiO2的浸出动力学过程可用界面反应模型来描述,其浸出反应动力学方程为1-（3-x）2/3＋2（1-X）=k2t,表观活化能约为14．2kJ／mol,属于固体内扩散控制．     

甲醇/乙醇-氢气还原铁矿石制备Fe3C研究

鉴于工业上成功采用CH₄-H₂系和CO-H₂系气体作为还原剂制备Fe₃C, 尝试以甲醇作为碳源, 同氢气共同还原铁矿石制备Fe₃C.试验考察温度、氢还原时间、甲醇量对碳化铁率的影响.采用扫描电镜分析、XRD测试等手段研究产物的物相组成.结果表明:在反应温度700 ℃, 无水甲醇量高于60 mL, 氢还原时间120 min的试验条件下, 达到高效生产Fe₃C的目的.该工艺方法流程简单, 操作条件温和, 具有广阔的应用前景.在此基础上, 用乙醇代替甲醇, 研究其还原效果.      

Kinetics of reduction of nickel chloride with hydrogen

The kinetics of reduction of nickel chloride with hydrogen were investigated in the temperature range of 533 (260 °) to 788 K (515 °). Most experiments were done with porous NiCl2 granules having ?8+10 mesh (Tyler) size. The effects of temperature, sample size, granule size and hydrogen partial pressure on the reduction kinetics were investigated. In the temperature range 533 (260 °) to 651 K (378 °) the reduction is dominated by chemical kinetic factors. At higher temperatures diffusional effects appear to become quite significant. The temperature-dependence of the chemical kinetic rate constantK is given by $$\log K = 6.744 - \frac{{22,240}}{{2.303RT}};K\,\,is\,\,in\,\,\min ^{ - 1} $$ The activation energy for the reduction was found to be 22,240 cal /mol (or 93,050 J/mol) in the chemical kinetic regime.     

红土型金矿石浸出剂的选择

根据氰化法和水氯化法对红土型金矿石浸金试验结果,论证红土型金矿石浸出剂的合理选择,兼评二者长短。     

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.     

Flue gas recirculation in iron ore sintering process

Flue gas recirculation has been introduced into iron ore sintering process to reduce pollutant emissions. Compared with the conventional process, the sintering indices reduce gradually with decreasing O₂ content in the recirculating gas. With sufficient O₂, the principle on the use of flue gas recirculation is proposed. The heat loss caused by the decrease in O₂ content is compensated by 250°C gas and 0.5%CO. The flame and heat transfer fronts of the sintering bed coincide using mixed gases of no more than 6%CO₂ and 8%H₂O (g). A novel technology of 35.5% flue gas recirculation ratio is proposed with qualified sintering indices.     

The sticking of iron ore during reduction by hydrogen in a fluidized bed

Abstract

Sticking of particles in the fluidized bed reduction of iron ore at temperatures above 600°C will occur whenever clean iron surfaces impinge. Some as-received ores are sufficiently dirty that iron-iron contact does not take place at low temperatures. However, as the temperature of reduction is raised, there is an increasing tendency for the iron nucleating on the surface of particles to grow into nodules which pierce the dirt film allowing iron-iron contact and hence sticking. Silica in the surface film stops iron nucleation near the surface of particles and thereby prevents iron nodule formation. Ores with silicacontaining coatings can be fully reduced in a fluidized bed at temperatures up to 840°C without sticking.

Résumé

Les particules de minerai de fer au cours de la réduction en lit fluidisé aux températures supérieures à 600°C ont tendance à s'agglomerer aussitôt que des surfaces de fer sont en contact. Quelques minerais utilisés comme tels sont suffisamment impurs pour que le contact fer sur fer ne se produise pas aux basses températures. Cependant, quand la température est élevée, la nucléation du fer a la surface des particules se prolonge par la formation des modules qui percent la couche d'impuretés et favorisent l'agglomération. La présence de silice dans la couche superficielle empêche la nucléation du fer au voisinage de la surface donc aussi la formation de modules de fer. Les minerais contenant de la silice peuvent être réduits complètement dans un lit fluidise a des températures allant jusqu'à 840°C sans s'agglomérer     

Sintering behaviours of iron ore with flue gas circulation

Flue gas circulation is an important method for energy conservation and pollutant emission reduction in iron ore sintering. In this paper the effects of flue gas recirculation ratio on sintering of different iron ores including haematite, magnetite and limonite were studied by illustrating the variation of sinter bed temperature, atmosphere and mineralisation characteristics of different types of iron ores induced by the circulation. It shows that the proper flue gas circulation ratios for haematite, magnetite and limonite are 37, 30 and 25%, respectively. For magnetite ore, preheating and high consumption of oxygen in combustion zone caused more silicate minerals and less acicular calcium ferrite, thereby lowering sinter tumbler strength. As for haematite ore, the rapid change of temperatures of combustion, melting and solidification zones leads to elevated combustion efficiency and increased formation of acicular calcium ferrite, which enhances the sinter strength. When using limonite ore as the main raw material, high oxygen consumption, lower maximum temperature of sintering bed, higher cooling rate and larger porosity of sinter are observed.     

含铌铁矿粉氢气选择性还原过程中磷行为

 对白云鄂博含铌铁矿粉氢气选择性还原-熔分-铌铁冶炼的提铌方案中磷的行为进行试验研究。在该试验条件下,磷质量分数为0.100%的含铌铁矿粉通氢气还原后熔分,得到磷质量分数小于0.010%、铌质量分数为2.000%的富铌渣,铁中铌质量分数为0.008%、磷质量分数为0.230%,铌磷分离效果明显,同时熔分后铌品位是原来的3.5倍。试验结果表明,氢气在还原阶段能够在还原铁氧化物的同时将Ca3P2O8还原,通过熔分达到铌与磷、铁元素等分离的目的,铌有效地富集在渣中。     

Separation of aluminium and preparation of powdered DRI from lateritic iron ore based on direct reduction process

Lateritic iron ore has not been used effectively due to excess content of multiple metals. In this work, separation of aluminium from a high-aluminium lateritic iron ore was achieved by the process of ‘direct reduction with sodium sulfate-magnetic separation’, with a powdered direct reduced iron (DRI) produced. It is found that the presence of 12% sodium sulphate during reductive roasting significantly improves separation of iron and aluminium in magnetic separation: the total iron grade (TFe) of powdered DRI increases from 80.6 to 92.0% and the Al₂O₃ content decreases from 9.8 to 1.3% correspondingly. The presence of sodium sulphate results in formation of sodium aluminosilicates instead of FeAlO₂. Moreover, sodium sulphate significantly promotes growth of metallic iron grains which is beneficial to sufficient liberation and separation of metallic iron grains from gangue minerals in grinding and magnetic separation.     

硝酸银电位滴定法测定铁矿石中水溶氯

以2g/L硫酸钾为溶解试剂,硝酸银为滴定剂,电位滴定法测定铁矿石中的水溶氯,通过电极电位-浓度二次微商滴定曲线,计算二次微商等于零时对应的V为滴定终点,可省去绘制E-V曲线或ΔE/ΔV-V一次微商曲线作图带来的麻烦。试验比较了温度、酸度、搅拌方式等对测定结果的影响,对干扰元素及活度与浓度的关系进行了分析。方法的相对标准偏差小于2.12%,用于实际样品分析加标回收率在90.0%~108.0%之间。     

烧结厂烧结废气能见度分析

烧结厂可见的烧结废气严重影响工厂周围景色。通过详细分析大分厂一号烧结机烧结废气的组分和粉尘,对可见烟气的形成机理进行了讨论。含有硫酸的烧结废气在冷却过程中形成的可见烟气的主要物质为空气中的雾气凝结物。硫酸具有促进雾气凝结和降低可见水雾汽化的作用,废气中的粉尘可作为雾气凝结的凝结核。在名古屋3号烧结机进行的测试验证了这种机理认识,通过将富含SOx的气体与烧结废气重新混合来观察具有长尾迹的可见烟气。总之,要使烧结废气不可见,需要有脱硫设备。     

Process simulation of iron ore sintering bed with flue gas recirculation

Abstract

As issues of productivity, quality control, energy efficiency and environmental regulation become ever more important in the iron ore sintering process, controlling combustion inside the sinter bed is attracting renewed interest in terms of flue gas recirculation (FGR) and oxygen or gaseous fuel enriched combustion. The application of combustion control schemes inevitably brings changes to incoming and outgoing gas conditions as well as to plant configuration. The objective of this study is to build a process model of a sintering bed using a flowsheet process simulator and to obtain information on material flows for various process configurations and operating conditions. The process modelling was designed to quantify the heat and mass flow in each of the bed segments, which could then be integrated to represent the overall material and energy flow of the entire bed. Variations in incoming and outgoing gas conditions were compared among different configurations of recirculation using the model.     

Kinetics and catastrophic swelling during reduction of iron ore in carbon bearing pellets

Abstract

The rate of reaction between iron oxides and charcoal, agglomerated together as pellets, has been correlated with the swelling of the pellets and with the morphology of the iron formed. The experimental techniques employed were thermogravimetric analysis, X-ray diffraction analysis, and microscopic examination of partially reduced pellets. The experiments were performed in the temperature range 1223–1423 K. The conditions that favour the growing of iron in the form of whiskers, and hence lead to catastrophic swelling, have been determined.