Non-isothermal reduction characteristics of roasted high alumina iron ore pellets

Non-isothermal reduction of roasted Guangxi high alumina iron ore pellets with CO and H₂ was conducted with high temperature synchronisation thermal analyser (NETZSCH STA 409C/CD) to understand the reduction characteristic of the ore. Chemical analysis, X-ray diffraction examination and scanning electron microscope analysis were adopted to analyse the roasted and reduced pellets. The results show that there are three main phases of Fe₂O₃, Al₂O₃ and Al₃Fe₅O₁₂ in the roasted pellets. During reduction process, the iron bonded in hercynite and fayalite is difficult to be reduced by CO so that the final reduction degree is only 35.62% at the setting temperature of 1573?K. But with H₂ atmosphere, the reduction degree can reach 100% at about 1520?K. It suggests that the ferric ion can completely be reduced to metallic iron by H₂.     

高铝铁矿焙烧球团非等温还原研究

采用CO、H_2对高铝铁矿焙烧球团在高温同步热分析仪(NETZSCH STA 409C/CD)中进行非等温还原.结果表明:焙烧球团经CO还原后,随着设定温度由1 273 K升高到1 473 K,最终还原度由32.21%仅增加到46.78%;而经H_2还原后,随着设定温度由1 273 K升高到1 573 K,最终还原度由81.93%增加到100%.在纯氢气还原条件下,高铝铁矿焙烧球团中的铁氧化物是可以被彻底还原的.     

球团矿恒温和升温直接还原膨胀行为试验

 将球团矿分别在900 ℃恒温和升温试验条件下还原,研究了球团矿的还原膨胀行为;分析了2种温度条件下球团膨胀机理;对比了2种条件下的试验结果,观察分析了还原后球团的外观和微观组织形貌,得到了导致2种温度条件下球团膨胀差异的原因。研究结果表明：恒温还原球团的最大膨胀值为18.3%,升温还原时为8.3%,恒温还原球团的膨胀行为更加明显;裂纹和气孔的形成以及金属铁的析出形态差异是造成膨胀差异的主要原因。由此得出,为了得到与实际生产相近的还原膨胀行为,球团矿应该在升温条件或模拟的生产条件下进行还原试验。     

内配碳红土镍矿球团制备工艺

以红土镍矿作为原料,煤粉作为还原剂,氧化钙作为熔剂,配加一定量的黏结剂和水,经对辊压球机压制成含碳球团.对红土镍矿的成球特性进行了研究,考察了还原剂、水分和黏结剂等因素对球团强度的影响.结果表明:红土矿粉本身具有较好的成球特性,在不加入黏结剂的条件下,球团仍具有一定的强度;较细粒度的煤粉会降低球团的强度,适宜含量的较粗粒度的煤粉能提高球团的强度;随着水分加入量的提高,球团的抗压强度逐渐提高,当水的质量分数为18%时,其抗压强度达到最大值,若水分继续增加,抗压强度呈现下降的趋势;球团的落下强度随着水量的增加而升高;随着膨润土用量的增加,球团强度有明显的提高,当膨润土的质量分数为2%时球团强度达到最大值,随着膨润土用量的进一步提高,球团强度略微下降,且膨润土中含有较高含量的SiO₂和Al₂O₃,会降低球团有用元素的品位,因此用量不宜过高.     

高铝铁矿含碳球团直接还原的研究

用高铝铁矿粉配加煤粉造球,在实验室条件下,通过改变还原温度和碳氧比研究了含碳球团的还原,对还原后的球团进行化学分析以及X-射线衍射(XRD)检测。结果表明:试样在石墨坩埚中恒温还原4 h,还原完毕后立即取出通入惰性气体冷却,在还原温度为1 200℃、碳氧比为1.3时金属化率较高,达到88.45%,在此条件下,铁、铝分离效果较好。同时从工业应用角度分析了转底炉处理高铝铁矿石的可行性。     

Influence of microwave heating on the microstructures of iron ore pellets with coal during reduction

Iron ore oxidised pellets as the burden of blast furnace present many advantages, such as uniform size, high iron grade and high physical strength. A comparison of the iron ore oxidised pellets with coal (out-proportioning) by conventional heating and microwave heating was carried out in this paper. Microstructure transformations during reduction process were investigated by optical microscopy and scanning electron microscope with energy dispersive spectrometry analysis. Micro-hardness of metallic iron phase formed in the reduction was tested with digital micro-hardness tester. The influences of microwave heating on reduction degree, morphology, iron phase and gangues were investigated, respectively. The results show that reduction time can be greatly shortened by microwave heating even at lower temperatures. The fine cracks generated, as the pellets were heated by microwave, were irradiated due to the selectivity of microwave heating. Densification of the metallic iron phase and the separation of the iron and gangues were both found to be enhanced by microwave heating.     

高磷铁矿石含碳球团等温还原动力学

为了研究高磷铁矿石含碳球团等温还原动力学在温度为1 173、1 273、1 323、1 373、1 423和1 473K时,采用界面化学反应模型、Jander方程、Ginstling-Broushtein方程、G Valensi-R E Carter方程等固-固/气反应机理函数对反应过程进行拟合,并采用XRD、SEM、EDX等对样品的物相组成、微观形貌和元素分布进行表征分析。研究结果表明,随着还原程度提高,反应速率由0迅速增至最大值,随后逐渐减小并趋于平缓;当温度为1 173～1 373K时,反应过程符合界面化学反应,表观活化能为70.02kJ/mol,线性相关系数为0.948 1;当温度为1 373～1 473K时,反应过程符合Jander方程,限制步骤为铁离子固相扩散,表观活化能为215.36kJ/mol,线性相关系数为0.991 2。     

铁矿球团用有机黏结剂研究进展

 随着钢铁行业绿色低碳转型,使用有机黏结剂替代膨润土已经是铁矿球团工序提质降耗的必然趋势。然而,有机黏结剂彻底替代膨润土的技术壁垒仍未突破,严重限制了其在工业生产中的广泛应用。有机黏结剂的黏结效用也是控制球团强度的关键因素,研究其在球团生产中的作用机理对提高球团强度以及开发具有国内知识产权的新型有机黏结剂意义重大。通过总结有机黏结剂在铁矿球团中的研究进展,旨在为其在中国钢铁行业的广泛应用以及新型有机黏结剂的研发工作提供理论指导与试验依据。在介绍理想有机黏结剂分子结构模型的基础上,揭示了4种常见有机黏结剂的结构及特性。重点讨论了黏度和吸水性对有机黏结剂黏结效用的作用机理,有机黏结剂的高黏度特性能够调节球团颗粒间液桥黏滞力大小,从而显著提高生球强度;吸水性是有机黏结剂调控生球自由水含量的重要特性,只有在最佳吸水率下,才能获得强度较高、粒径均匀的生球。总结了有机黏结剂的常见优缺点,其主要优点是微量高效、烧失量大、基本不影响球团铁品位,缺点是生产球团矿缺乏渣相固结而强度不足。分析了优化原料粒度组成、添加含硼化合物及分散剂等强化有机黏结剂球团生产的调控手段,并展望了有机黏结剂未来的发展方向。     

含碳球团直接还原熔分机理

为了探究含碳球团还原熔分机理,将分析纯的Fe₂O₃、氧化物和不同还原剂固结成球并进行等温还原实验,研究了温度、还原时间、配碳量、还原剂种类等条件对球团还原熔分行为的影响.进一步采用X射线衍射、扫描电子显微镜等手段表征了含碳球团在不同还原时间的微观结构及物相变化.实验结果表明：焙烧温度过低或过高含碳球团都不能良好熔分,配碳量增加可以提高球团还原和熔分速率,适宜的温度、碳氧摩尔比、还原剂分别是1400℃、1.2和煤粉.含碳球团还原熔分包括直接还原反应、间接还原反应、碳的气化反应、渗碳反应和铁的熔化反应,最后实现渣铁分离.     

红土镍矿高料层碳热还原试验

 红土镍矿是生产镍铁合金的主要原料之一,其碳热还原后的镍铁金属颗粒尺寸对后期磁选分离至关重要。基于此,进行了红土镍矿在高料层条件下的碳热还原试验研究,考察了还原温度、时间及添加剂CaO等对还原后镍铁金属颗粒尺寸的影响规律和作用机理。试验结果表明,在配碳量C/O(质量比)为1.0、还原温度为1400 ℃、还原时间为45 min的条件下,还原效果最佳,还原后大于40 μm的金属颗粒约占70%,最大颗粒约为100 μm。对该还原条件下得到的金属化球团进行磁选分离可得到镍铁合金,基本可以将金属镍回收。研究结果可为红土镍矿碳热还原工艺的应用提供操作参数和理论依据。     

球团矿不同气氛下的高温抗压强度

采用自行设计的高温抗压强度在线测定装置,研究了氧化球团矿在不同气氛下的高温强度变化规律,并对高温下强度变化的机理进行了分析和探讨.实验结果表明:球团矿在中性气氛和氧化性气氛下的高温强度变化规律基本一致,表现为在低于800℃的温度范围内,球团矿强度随着温度的上升而增大,但在800~900℃球团矿强度有个明显的下降,900~1100℃球团矿强度随温度的升高略有回升,1100℃以后强度急剧下降,到1200℃时已基本失去强度;中性气氛下的球团强度整体高于氧化性气氛下的强度;在还原性气氛下,球团矿强度随着温度和还原度的提高而降低,至1100℃时强度基本消失.     

碱度对白云鄂博矿球团矿还原膨胀性能的影响

高比例球团矿冶炼是高炉炼铁发展的趋势。由于化学成分、矿物组成和结构的差异,不同企业生产或所用的球团矿还原膨胀的原因各不相同且相对复杂。面向保障矿产资源安全供给的国家重大战略需求,选择白云鄂博铁精矿球团矿作为研究对象,根据球团矿铁氧化物还原理论,从热力学方面深入研究碱度对球团矿还原膨胀性能的影响机理,并结合XRD结果来探究钙结合相在球团矿生产中的变化规律以及对球团矿还原膨胀的影响,找到满足高炉冶炼对球团矿还原膨胀率要求的合理碱度,从而提高白云鄂博铁精矿球团矿在包钢冶炼生产中的比例。完善特殊矿球团矿还原膨胀理论,为复杂共生矿高效冶炼提供理论支撑。研究结果表明,随着碱度的提高,球团矿的膨胀率呈现出先升高后降低的规律,碱度为0.8时,其膨胀率最大,达到75.743%,其外形如同花瓣开花,无法维持原来的球型。综合不同碱度球团矿含铁品位的高低和还原膨胀的大小,得到制备球团矿的最优碱度为1.4。随着碱度的提高,成品球的液相生成量先降低后升高,碱度为0.8时液相生成量最少。球团矿膨胀率先增加是因为球团矿的结晶度提高,晶粒粗大,晶体结构逐渐趋向有序,为铁晶须的生长奠定了基础;膨胀率后减小是因为生成了铁酸...     

A laboratory-based investigation into the catalytic reduction of NOx in iron ore sintering with flue gas recirculation

The catalytic reduction behaviours between NO_x and CO in sinter zone were studied as using flue gas recirculation (FGR). Minerals in sinter can act as catalysts during NO_x reduction. The catalytic activity of minerals has the order of calcium ferrite?>?kirschsteinite?>?fayalite. The catalytic procedure includes two steps: iron-bearing minerals are reduced to lower valence oxides by CO, and then NO is reduced to N₂ by lower valence oxides. Improving the generation amount of calcium ferrite, especially acicular-type silico-ferrite of calcium and aluminium (SFCA), contributes to significantly reinforcing the catalytic performance between NO and CO. As the basicity of sinter increases to 2.2, it enables to generate maximum amount of acicular-type SFCA which has larger specific surface areas, therefore facilitates decreasing NO_x emission during FGR sintering.     

Evaluation of carbothermal reduction for processing of banded hematite quartzite iron ore

ABSTRACT

This study evaluates iron recovery from low grade banded hematite quartzite iron ore. The ore was found susceptible to microwaves and hence carbothermal reduction was pursued. The susceptibility of iron phases to microwave exposure and their selective absorption assists in the liberation of iron values. It was observed that ferrite balls were formed when a small fraction of ore-charcoal mixture was microwave irradiated. The adequate presence of bonded silica content leads to an easy formation of the fayalite phase which leads to fall in the iron grade. Microwave carbothermal reduction at the varying charcoal dosage (6–11%) yielded Fe_G 45–48% at Fe_R 40–70%. However, at higher charcoal dosage (11%), ferrite ball formation was observed. Taguchi L₉ statistical design revealed the formation of ferrite ball at the higher charcoal dosage (9–12%) and higher power (720–900 W) which accounts for 8–10% of total iron values contained.     

铁矿直接还原用台车连续炉

介绍一种用于铁矿直接还原的台车连续炉，含碳球团料层铺在台车上并通过炉膛进行焙烧和还原。此炉子已经成功地用于铁精矿粉还原焙烧，所得到的海绵铁产品的金属化率大于92％，全铁约90％。和转底炉比较，台车连续炉的优点是结构简单，供热点少，台车维修方便；主要缺点是台车运转速度不能太快，焙烧时间较长。     

链箅机铁矿球团料层催化脱硝的反应行为及影响因素

 在资源约束、环保压力趋紧的形势下,新时期球团环保的重点是减少NO_x的排放,其高效控制关系着球团行业的生存。以铁矿球团为对象,研究了球团料层温度对不同铁精矿球团脱硝的影响,在此基础上研究了链箅机抽风干燥段(DDD段)催化脱硝的反应行为,并通过脱硝率、氨利用率等来表征烟气成分对DDD段喷氨脱硝的影响。研究结果表明,在相同条件下,赤铁精矿的催化性能优于磁铁精矿和混合铁精矿,同时分析了链箅机各段温度分布的特点,最终选择DDD段作为SCR脱硝的反应区域。DDD段适宜的脱硝条件为,温度为300～350 ℃,氧气体积分数为15%～20%,氨氮比(物质的量比)为0.5;在链箅机抽风干燥段进行SCR脱硝时,烟气中的SO₂体积分数由0提高到0.050%,反应脱硝率由51.0%降低到34.4%;随着烟气中水蒸气含量的提高,反应脱硝率降低,在水蒸气体积分数为9%时,脱硝率仅为44.9%,总体来讲,控制SO₂体积分数小于0.040%,水蒸气体积分数小于6%,可以获得40%左右的脱硝率,在DDD段喷氨催化法脱硝是高效可行的。     

Investigation of kinetics of coal based reduction of oolitic iron ore

Abstract

An oolitic iron ore was isothermally reduced by coal at 1423–1573 K, and the reduction kinetics was investigated in detail. The degree of reduction and reduction rate increased with increasing temperature and C/O molar ratio to some extent at the same reduction time. In the entire reduction process, the reduction mechanism changes with changing experimental conditions. The degree of reduction under different experimental conditions should be represented by different reduction kinetic models. The reduction rate curves are similar in shape and could be analytically divided into initial, intermediate and final stages. The apparent activation energies of the three stages are 48·26, 69·80 and 127·58 kJ mol^?1 respectively. The rate controlling mechanism in the reduction process was determined by analysing the reduction process and apparent activation energy. The rate controlling steps of these stages are combined gas diffusion and interfacial chemical reaction, surface chemical reaction and combined solid state diffusion and boundary reaction.     

高磷铁矿含磷矿物与脉石相碳热还原机理

针对高磷铁矿矿物组成特点,对氟磷灰石与高磷铁矿中脉石相的反应进行了研究,阐明了高磷铁矿在直接还原过程中含磷矿物的碳热还原机理.研究发现：在不配加石墨的情况下,氟磷灰石与脉石之间相互独立,没有发生反应;在配加石墨的情况下,氟磷灰石发生不同程度的还原,脉石中 SiO2脱磷能力最强.当 SiO2、Al2 O3和 Fe2 O3同时加入氟磷灰石后,氟磷灰石碳热还原速率加快,并且在脉石相中形成了 CaAl2 Si2 O8.     

X射线荧光光谱法测定铁矿石中全铁及18个次量成分

采用X射线荧光光谱法测定铁矿石中主量成分（TFe）及18个次量成分（P、SiO2、Al2O3、CaO、MgO、Mn、TiO2 、V2O5、K2O、S、Cr2O3、Ni、Co、Zn、Pb、Cu、Na2O、As）。以固定理论α影响系数法校正基体效应,使各成分的适用检测范围都得到较大拓宽;采用熔融方法制样,消除了试样的粒度效应和矿物效应。为了避免S的损失,样品经预氧化后灼烧,由软件计算或准确测定样品的烧失量。精密度试验表明,各成分的标准偏差（SD）为0.001%～0.268%。方法用于铁矿石实际样品分析,结果与其他方法结果相吻合。     

三氯化钛还原-高锰酸钾无汞滴定法测定铁矿石中全铁量

用HNO3-HF处理,硫-磷混酸溶解试样,在盐酸介质中,用二氯化锡-三氯化钛将Fe3+还原为Fe2+,以二苯胺磺酸钠为指示剂,以高锰酸钾标准溶液滴定铁矿石中的全铁量。试验并确定了测定过程中的各种最佳分析条件。方法用于分析铁矿石中全铁含量,其相对标准偏差在0.28%~1.0%之间,结果与认定值相符。该方法避免了二氯化汞-重铬酸钾滴定法中汞和铬对环境的二次污染。