煤中氢对含碳球团还原的影响

针对含碳球团还原过程中的煤种选择问题,研究了烟煤和无烟煤挥发分中氢对含碳球团还原的作用以及温度、加热速度对氢还原过程的影响。结果表明,含碳球团中煤热解产生的氢对铁氧化物有还原作用。由于煤中挥发分的热解析出温度与氢还原铁氧化物的还原温度不一致,氢在还原初期迅速放出,导致氢的还原作用率低;提高温度和加热速度可提高煤中氢的还原作用率和挥发分的利用率。综合考虑,含碳球团实际生产选择煤种时,应选择反应性好的无烟煤。     

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.     

冶金尘泥含碳球团直接还原机制的试验研究

以气固反应相继发生动力学模型为基础开展冶金尘泥含碳球团直接还原试验,考察还原速率、还原率以及还原气氛等表征还原特性的特征参数在整个还原过程的变化,研究冶金尘泥含碳球团的还原行为及过程的作用机制。结果表明:冶金尘泥含碳球团的还原过程由孕育启动期、快速反应期和反应结束期组成,反应进程快,3～5 min就能达到碳气化和铁氧化物还原剧烈进行的温度。在1 270℃以下,升高温度对含碳球团还原有明显加速作用,但进一步提高温度,球团n(C)/n(O)((C、O摩尔比))及球团中碳的消耗对还原过程的影响更为显著,表现在最大还原速率维持时间延长,还原率大幅提高。碳气化反应是含碳球团还原过程最重要的环节,其反应生成的CO决定了铁氧化物还原反应物的供给速度。反应过程处于明显的还原性气氛中,气氛中CO_2来自于部分CO的进一步氧化,其含量多少取决于气氛中CO的数量和反应的进程。     

含碳球团-铁浴熔融还原炼铁法与COREX法的能耗比较

通过计算机模拟计算,研究了含碳球团高温快速预还原＋铁浴终还原炼铁法、含碳球团竖炉预还原＋铁浴终还原炼铁法和含碳球团铁浴一步炼铁法这３种工艺流程的能耗,并与ＣＯＲＥＸ法进行比较。结果表明：含碳球团＋铁浴终还原炼铁法比ＣＯＲＥＸ法的耗煤量和耗氧量低。另外,还介绍了高含碳球团的优点,认为高含碳球团有一定的应用前景     

温度对高磷鲕状赤铁矿含碳球团直接还原影响

对高磷鲕状赤铁矿含碳球团直接还原进行了研究。结果表明,1100℃以下时,提高温度可以显著提高球团金属化率;1100℃以上时,继续提高温度对球团金属化率影响不大。球团金属化率越高,磁选精矿铁品位越高。还原温度不仅显著影响球团的金属化率,还影响金属铁相的长大及磁选效果。因此,控制适宜的温度对高磷鲕状赤铁矿含碳球团直接还原至关重要。     

高炉瓦斯灰制含碳球团直接还原试验研究

通过试验对高炉瓦斯灰和氧化铁皮制得含碳球团的直接还原进行了研究,考察了不同还原气氛、球团中不同C/O、还原时间、还原温度对还原结果的影响。结果表明:高温下含碳球团在空气中直接还原就能获得很高的金属化率。当球团中C/O在1.2以上时,球团的金属化率在还原过程中一直增加,在1 350℃下还原30 min,球团的金属化率达到96.94%。球团金属化率的变化趋势表明球团在反应开始是由化学反应控速环节控制,而后逐渐向扩散控速环节过渡。在1 400℃下空气中还原30 min,球团中还原出的铁与渣完全分离。     

含碳球团的还原性和还原冷却后的强度

在1273~1573 K条件下研究了不同煤种、木炭和石墨与不同种类矿石制成含碳球团的还原速度;进而讨论了温度、配碳比(C/O)、挥发分含量等因素对含碳球团还原所需时间和金属化率的影响.通过测定含碳球团还原冷却后的强度,对影响强度因素进行了分析.还原冷却后的强度在温度1273 K时较低,配入含挥发分较高的气煤,可以使还原冷却后的强度提高,加快反应速度.     

氧化锌球团还原的机理研究

采用等温法研究了纯氧化锌配加石墨碳粉制成含碳氧化锌球团的还原动力学 ;考察了坩埚尺寸对氧化锌还原的影响 ;并研究了铝浴条件下对含碳或不含碳氧化锌球团还原的影响。结果表明 :根据Arrhenius方程计算出 ,当碳气化反应和界面还原反应为限制环节时 ,在 12 73～ 14 2 3K下其活化能分别为 3 7 615kJ/moL和 43 192kJ/moL ,碳还原氧化锌的还原速度由气相扩散所控制 ,12 73～ 14 2 3K下其活化能为 46 5 48～ 5 3 2 80kJ/moL ,含碳球团在大坩埚中的还原速度快 ,有铝浴存在的还原速度快 ;在 12 73～ 15 2 3K下铝浴与氧化锌球团 (不含碳 )基本不发生还原反应     

褐铁矿含碳球团的爆裂特性研究

根据褐铁矿含碳球团转底炉还原熔分生产粒铁的技术思想,对褐铁矿含碳球团的爆裂特性进行了实验研究.实验结果表明,褐铁矿含碳球团的爆裂与结晶水的解离有关,结晶水解离速度较快,在950℃下90s内球团中的结晶水基本上全部解离,褐铁矿含碳球团的爆裂温度约为900℃,与不含煤粉的褐铁矿球团相比约高100℃,含碳球团有利于减弱爆裂,因此,褐铁矿含碳球团的入炉温度要低于900℃.在爆裂温度以下,褐铁矿含碳球团的预热温度越低,预热时间越短,到1 300℃急速加热时,球团爆裂越严重.因此,在本实验条件下,球团最佳入炉温度约为850℃.     

煤粉粒度对预热含碳球团抗压强度的影响

为了弄清含碳球团配煤粒度对球团抗压强度的影响规律,研究了配加不同粒度煤粉的含碳球团在中性气氛中预热至不同温度后的抗压强度。结果表明:当温度小于1 000℃时,煤粉粒度对含碳球团的抗压强度影响不大,而当温度大于1 000℃后,煤粉粒度对含碳球团的抗压强度有显著影响;当配加煤粉的粒度介于0.074~0.106mm时,含碳球团还原后的抗压强度最高,煤粉粒度过细或过大都不利于球团强度的提高;在高温还原过程中,煤粉粒度越细含碳球团的还原速率越大,金属化率越高。     

Sticking behaviour and mechanism of iron ore pellets in COREX pre-reduction shaft furnace

COREX is a clean process releasing lower pollution and consuming fewer cokes than the blast furnace process. However, serious sticking phenomenon often occurs in COREX shaft furnace, causing many problems to the normal operation. In this study, the loading reduction experiments of iron ore pellets were carried out under the simulating COREX reducing conditions. The influence of temperature and H₂ content in the syngas on the sticking behaviour of the pellets was observed by scanning electron microscope, energy-dispersive spectrometer and X-ray diffraction. The results indicated that the sticking index increased from 6.7 to 90.43%, when the temperature increased from 750 to 950°C. The main composition of sticking material was metallic iron, and the sticking behaviour depended upon the amount and morphology of precipitated iron on the pellets’ surface. The sticking mechanism was the interpenetrating diffusion mechanism of iron atoms between the adjacent pellets.     

Sticking behaviour of vanadium titano-magnetite oxidised pellets during gas-based reduction and its prevention

The influence of reduction temperature and gas composition on sticking behaviour of vanadium titano-magnetite oxidised pellets was investigated in this work. It was found that the sticking index (SI) increased with temperature and CO content of gas mixture. Microstructure transformation of sticking interfaces under different temperature and gas compositions was analysed by SEM. Coating is an effective way to prevent sticking. Compared with MgO and CaO, recyclable Ti-bearing tailing is the most suitable coating material to prevent sticking behaviour of vanadium titano-magnetite pellets. The SI of pellets decreased significantly by coating Ti-bearing tailing with little influence on metallisation rate. It was indicated in SEM and EDS that spinel (Fe₂TiO₄), as the main component of minerals in Ti-bearing tailing, decreased the hooking opportunity of newly formed metallic iron between pellets by building spacers between pellets, which was applied to solve the sticking problem.     

还原流化床内铁的析出形态与铁矿粉的粘结行为

用电子扫描电镜分析和探讨了铁矿粉在还原流化床中的粘结行为与金属铁析出形态的关系，结果表明，在不同的还原条件下，金属铁将以不同的形态析出，而铁矿粉在还原流化床中的粘结行为又受金属析出形态的影响，在一定温度下，粘结现象主要由铁晶须引起的。最后，为熔融还原流化床提出了一种新的，有效的预防粘结措施。     

Stresses induced in iron-ore pellets by hydrogen reduction

The objectives of this investigation were (a) to determine the effect of reduction temperature on the strength of iron ore agglomerates and (b) to develop enhanced understanding for the cracking associ-ated with reduction. Iron-ore agglomerates from two sources (Samarco Mineração and Bethlehem Steel) were reduced in a hydrogen atmosphere at temperatures varying from 873 K to 1373 K at intervals of 100 K and times varying from 30 to 300 minutes. The compressive strength at the ambient temperature of the pellets was determined after the various reduction treatments by using a piston-and-cylinder testing technique and computing the energy required in crushing them. The highest strength, at a specific level of reduction, was found after reduction at 1073 K, for both the Samarco and Bethlehem pellets. Profuse cracking of the pellets was observed after reduction. These cracks led to a weakening of the pellets. A mechanism for reduction-induced cracking, based on internal stresses due to volume changes produced by the chemical reactions, is presented.     

Reduction of Pellets‐Nut Coke Mixture under Simulating Blast Furnace Conditions

In recent years an intensive work has been carried out to decrease the coke losses of the blast furnace through mixing small‐sized coke called “nut coke” in the iron ore burden layers. In order to clarify the influence of nut coke on the pellets reducibility, industrial iron ore pellets were reduced with and without nut coke participation under different temperatures and atmospheres. Isothermal and non‐isothermal reduction tests under simulating blast furnace conditions were performed using an experimental laboratory rig. Furthermore, reflected light microscopy, scanning electron microscopy and X‐ray technique were applied to characterize the microstructure and different phases developed in the origin and reduced pellets. Pellets reduced isothermally without nut coke participation exhibited reduction retardation (RR) at elevated temperature (≥1373 K) whereas the presence of nut coke had a positive effect of preventing such phenomena. The non‐isothermal reduction of pellets showed that, as the amount of nut coke in pellets bed increased, the reducibility of pellets increased, too. The rate controlling mechanism of pellets and pellets‐nut coke mixtures was predicted from the correlation between apparent activation energy calculations and microstructure examination.     

有机复合粘结剂特性表征及对球团矿性能的影响

摘要：添加有机粘结剂代替部分膨润土是减少成品球团矿的脉石含量的有效途径之一。通过残烧实验和XRD研究了膨润土与有机粘结剂间的相互作用,结果表明有机复合粘结剂比原始膨润土的晶层间距增加了008 nm。造球和焙烧实验结果表明,添加有机粘结剂替代膨润土可以提高生球落下和抗压强度。气基还原实验结果表明,添加有机粘结剂替代05%（质量分数）膨润土可以提高球团矿还原性,还原粘接指数也同时升高。SEM显微结果表明,添加有机复合粘结剂可以提高球团矿的孔隙率,有利于还原气体进入球团矿内部,从而改善球团矿的还原性。为制备有机复合粘结剂球团矿提供了参考,有助于扩大有机复合粘结剂在炼铁中的应用。     

Influence of reduction temperature on prereduction of iron oxide with coal carbonisation gas without tar

Abstract

The fundamental study on prereduction of iron oxide was carried out in order to investigate the conditions for efficient use of the volatile matter in coal in an iron bath smelting reduction total process. At a rate of 200 K h^?1 under rising temperature conditions up to 1273 K, 1 kg of non-coking coal having 37 mass-% volatile matter was carbonised. Subsequently, this gas without tar reduced 2 kg of iron oxide pellets packed in a separate reactor at various temperatures between 673 and 1273 K. The fractional reduction F increased linearly from 0·07 to 0·25 at the reduction temperatures up to 1073 K, beyond which F increased more than the linear relation, such as F=0·35 at 1173 K and 0·43 at 1273 K. This may be due to the contribution of hydrocarbons to the reduction reaction at high temperatures. The hydrogen reduction accounts for about half of the fractional reduction. The mass of filtered tar occupied a mass of about half of the volatile matter released during coal carbonisation. This implies that more fractional reduction can be obtained when the tar is used in the process.     

渣系碱度对含碳球团渣相组成和渣铁分离的影响

采用煤基直接还原熔分技术和FactSage热力学分析软件以及XRD分析手段,研究了渣系碱度wCaO/wSiO2对高铁铝土矿含碳球团渣相组成和渣铁分离效果的影响。实验结果表明,渣系碱度对含碳球团的渣系组成和渣铁分离效果有重要影响。当碱度为1.0和1.5时,粒铁尺寸最大,渣铁的分离效果最好,粒铁收得率分别为91.55%和91.86%;当碱度为0.5时,粒铁尺寸较小,渣铁分离效果较差,粒铁收得率为65.43%。当碱度为2.0时;粒铁尺寸最小,渣铁分离效果最差,粒铁收得率只有44.53%。XRD分析结果表明,当渣系碱度分别为0.5、1.0、1.5和2.0时,熔分渣的主要组成分别为α-Al2O3-CaAl2Si2O8、α-Al2O3-CaO·6Al2O3-Ca2Al2SiO7、CaO·6Al2O3-Ca2SiO4-Ca2Al2SiO7、Ca2Al2SiO7-Fe2SiO4。FeAl4O7、CaAl4O7以及金属铁在熔分渣中的含量较少。     

颗粒粒径对流态化还原铁矿粉黏结失流的影响

采用热态可视化流化床装置,在一定表观气速条件下,研究1073 K温度时不同粒级铁矿粉的黏结失流.根据对黏结失流影响程度的不同,可将矿粉颗粒分为三个粒径区间:中性气氛升温过程中失流的小粒径颗粒;还原至较低金属化率发生失流的中间粒径颗粒;还原至高金属化率也不发生失流的大粒径颗粒.分别对他们不同的影响机理进行了分析.研究还发现在正常流化条件下,随着矿粉颗粒粒径的增大,还原失流后床层的膨胀幅度会减小.