生物质用于直接还原工艺研究

选取木炭和无烟煤作为还原剂,分别研究了还原温度、C/O、还原时间对球团金属化率的影响。此外,还采用XRD物相检测分析、对比无烟煤和木炭对球团的还原效果。研究结果表明:以生物质木炭作为还原剂具有与无烟煤相当的还原效果,当C/O相同时,配加生物质木炭的球团与配加无烟煤含碳球团相比获得球团金属化率差距并不明显,以木炭为还原剂实现含碳球团的直接还原是可行的;以木炭为还原剂时,1 200℃下,C/O=0.7,还原时间20 min时,球团金属化率可达80%以上。     

白云鄂博矿含碳球团直接还原过程的实验及数值模拟研究

针对白云鄂博矿含碳球团,利用管式电阻炉研究了炉气温度在900~1 100℃之间球团的还原过程。建立数学模型考虑传热、传质以及化学反应来模拟白云鄂博矿含碳球团直接还原过程。实验结果表明,随着炉气温度的升高,球团质量减小的越快,还原反应结束的时间越短。模拟结果与实验结果吻合较好,随着炉气温度从900℃升高到1 000℃,最终金属化率从63%增加到95%,当炉气温度大于1 000℃时,增加温度对最终金属化率的影响较小;C/O比从0.8增加到1.0时,最终金属化率明显增加,从89%增加到95%,但当C/O比从1.0增加到1.2时,最终金属化率并没有明显增加;随着球团直径从12 mm增加到30 mm时,金属化率升高到最大值的时间从18 min增加到47 min,最终金属化率的值变大但增加不明显。     

金川镍渣直接还原磁选提铁实验研究

通过实验对镍渣和煤粉制备的含碳球团直接还原及磁选进行了研究,考察了不同温度、C/O、碱度等参数随时间的金属化率变化情况,以及不同磨矿细度下的磁选结果。结果表明:碳氧比为1.2,碱度为0.5的镍渣含碳球团,在1300℃下直接还原20min后可以获得98.34%的金属化率,在该条件下还原后所得金属化球团磨矿时间从10 min增加到90min,-200目所占比例从46.9%增加到95.6%,磁选后精矿TFe含量从78.82%降低到74.01%,而磁选产率与铁回收率则分别从51.77%和79.02%增加到70.92%和89.80%。实验室结果表明,镍渣通过含碳球团直接还原磁选的方式利用其中的铁资源在工艺上是可行的。     

硫酸渣含碳球团高温焙烧试验研究

基于转底炉直接还原工艺,以硫酸渣为原料进行压团、焙烧,通过正交试验研究了C/O、还原温度、还原时间等参数对球团金属化率和抗压强度指标的影响,并对其影响规律进行了分析.实验得出最佳工艺参数为:还原温度1 280℃;C/O比1.2;还原时间24 min.在此参数下,含碳球团的金属化率为89.79％,抗压强度为6 703 N/P.X光衍射(XRD)分析也证明,硫酸渣经过还原后出现了大量金属铁,表明采用转底炉工艺切实可行.     

双层结构对提高含碳球团强度的影响

为了提高含碳球团强度,提出了内层为含碳球团,外层为精矿粉的双层结构复合含碳球团新工艺.研究了不同外层厚度球团的强度和金属化率,分析了球团强度形成的机理.研究结果表明:外层厚度适中的复合含碳球团强度能得到有效提高.该复合球团生球落下强度为普通含碳球团的2倍,400℃预热球抗压强度可达147.6N/个.900℃后,随着温度的增加,球团抗压强度提高,1150℃恒温还原30 min后抗压强度为2 080 N/个.且研究发现复合含碳球团能有效提高碳素利用率,C/O物质的量之比nC/nO为2∶3的复合球团还原后金属化率可达93.90％,其中外层金属化率为92.46％.通过显微结构分析,发现球团还原后外层生成了致密的金属铁外壳,这种外壳的独特力学性能是球团强度提高的主要原因.     

钒钛磁铁矿含碳球团直接还原研究

以转底炉工艺为基础,在实验室模拟条件下,进行了钒钛磁铁矿含碳球团直接还原高温焙烧试验。通过XRD分析,讨论了配碳量(wC/wO)、还原温度、还原时间对球团金属化率和残碳量的影响。结果表明:随着还原温度的升高金属化率不断升高,而残碳量不断降低;在1 350℃之前,随着温度的升高,金属化率迅速升高,然后趋于平缓;当还原温度为1 350℃时,金属化率可达90%以上,随着还原时间的增加,球团的金属化率呈现先升高后降低的趋势,残碳量逐渐降低,还原时间为30 min时,球团的金属化率达到最大(91.37%);随着配碳量(wC/wO)的增加,球团还原速率加快,球团还原充分,球团的金属化率升高,当wC/wO为1.3时达到最大(94.28%)。     

塑料-无烟煤混合还原剂对含碳球团还原的影响

为了解决废塑料的污染问题,提出了将塑料与无烟煤一起进行低温热处理来制得含碳球团混合还原剂的思路,以达到钢铁工业协同处理废塑料的目的。通过研究还原温度和反应时间对含碳球团宏观形貌、金属化率及其微观结构的影响,对比分析了混合还原剂对含碳球团直接还原的影响。结果表明,以氧化铁粉末试剂为含铁原料,加入无烟煤与PE塑料热处理后的混合还原剂,在1 100和1 150 ℃,反应5~15 min时,能提高含碳球团的反应速率。当反应温度为1 150 ℃,反应接近还原终点时,混合还原剂含碳球团的金属化率为95.63%,基本接近无烟煤含碳球团的金属化率,但是在含碳球团中加入混合还原剂会引起一定程度的球团膨胀。     

钒钛磁铁精矿含碳球团成型工艺参数研究

以钒钛磁铁精矿和煤粉为原料,聚乙烯醇为黏结剂,采用正交试验和单因素试验研究水分含量、黏结剂加入量、成型压力、矿煤质量比对钒钛铁精矿含碳球团直接还原金属化率的影响,并对其影响规律进行了分析。结果表明:影响含碳球团金属化率的主次因素依次为水分含量、成型压力、矿煤质量比、黏结剂加入量;金属化率优化后的工艺条件为水分含量9%,成型压力12 MPa,矿煤质量比100∶22,黏结剂加入量0.4%,还原温度1 350℃,还原时间30 min。在此条件下含碳球团的还原效果较好,金属化率达到92.97%。     

镍渣直接还原磁选提铁试验

 通过试验对镍渣和煤粉制备含碳球团的直接还原和磁选进行了研究,考察了不同温度、碳氧比、碱度等参数随时间的金属化率变化情况,以及不同磨矿细度下的磁选结果。结果表明：碳氧比为1.2,碱度为0.5的镍渣含碳球团,在1300℃下直接还原20min后可以获得98.34%的金属化率,在该条件下还原后所得金属化球团磨矿时间从10min增加到90min,粒度小于0.074mm所占比例从46.9%增加到95.6%,磁选后精矿TFe质量分数从78.82%降低到74.01%,而磁选产率与铁回收率则分别从51.77%和79.02%增加到70.92%和89.80%。实验室结果表明,镍渣通过含碳球团直接还原磁选的方式利用其中的铁资源在工艺上是可行的。     

钒钛铁精矿含碳球团直接还原试验

采用正交试验和单因素试验考察还原温度、配碳量(nC/nO)、还原时间对某钒钛磁铁矿精矿直接还原的影响。结果表明,影响含碳球团金属化率的主次因素依次为还原温度、配碳量、还原时间。优化工艺参数为:还原时间35min、还原温度1 350℃、配碳量1.25、水分9%、成型压力12MPa、黏结剂加入量0.4%,此工艺条件下含碳球团的金属化率达91.77%,还原后球团的主要物相组成为金属铁。     

含碳球团冷固结成形的正交回归试验研究

 通过正交试验研究了用铁矿石和煤粉制造冷固结含碳球团的影响因素。考察了粘结剂的加入量、水含量、压球机的压力、压球机进料速度、压球速度、烘干温度和烘干时间对球团抗压强度的影响。结果表明：粘结剂加入量、烘干时间与水含量对球团的抗压强度影响最大,并进一步通过回归试验获得了这3个影响因素与球团抗压强度之间的回归方程。经验证,方程在一定范围内与试验结果符合较好。试验过程中获得的铁矿石冷固结含碳球团的最大抗压强度为25167N。     

Smelting Reduction of Iron Ore‐Coal Composite Pellets

Smelting reduction of iron ore‐coal composite pellets has been carried out in an induction furnace. The pellets, tied with tungsten wire, were immersed into the liquid metal bath. The experiments were carried out in the temperature range of 1713 K to 1733 K. For 16‐18 mm diameter pellets, it was observed that (i) the time required for complete dissolution in liquid metal bath is 83‐90 seconds, (ii) the fraction of reduction for 40 seconds of immersion varied from 0.68‐0.87 for Jharia coal pellets and 0.73‐0.92 for Bhilai coal pellets, and (iii) the fraction of reduction increases with decreasing Fe/C ratio and increasing immersion period. X‐ray diffraction (XRD) of reduced pellets showed that the reduction occurred topochemically. Scanning electron microscopic (SEM) examination of partially reduced pellets evinced the structural changes in pellets. The present investigation aims to assess the effect of Fe/C ratio in pellet, volatile matter in coal, and time of pellet immersion into liquid metal bath on reduction of iron ore‐coal composite pellets.     

含碳球团的还原熔分行为

通过高温电阻炉对含碳球团还原熔分的行为进行热态模拟研究,考察温度、配碳比、化学成分等因素对球团还原熔分的影响程度.结果表明,温度、配碳比和球团传热方向上的尺寸是控制球团还原熔分的关键;化学成分对还原速率影响不明显,但是通过改变渣的组成可对渣铁熔分起促进或抑制作用.     

Use of Iron Ore Fines in Cold-Bonded Self-Reducing Composite Pellets

The feasibility of producing direct reduced iron from cold-bonded, self-reducing composite pellets, constituted from beneficiated iron ore slime, coke, and different binders (dextrin, bentonite, calcium lignosulfonate, and carboxymethyl-cellulose [CMC]) was studied. This was done using a design of experiments approach. It was found that as-received beneficiated iron ore slime is suitable as a raw material for the production of self-reducing composite pellets with carboxymethylcellulose as the most suitable binder. Dry strengths in excess of 300 N/pellet were attained by curing the pellets under ambient conditions. The composite pellets reduced within 20 min to degrees of metallization in excess of 90% at 1100°C, with decrepitation indices significantly below 5%. The degree of metallization of composite pellets increased with an increase in reduction temperature (from 1000 to 1100°C), reduction time (20 min. vs. 40 min), and coke quantity (15% vs. 20%). CMC was identified as the most economical and suitable binder for the Sishen concentrate.     

CHARACTERIZATION OF PROPERTIES AND REDUCTION BEHAVIOR OF IRON ORES FOR APPLICATION IN SPONGE IRONMAKING

Studies on the chemical and physical properties, and the reduction behavior (in coal) of hematite iron ores procured from 10 different mines of Orissa, were undertaken to provide information for the iron and steel industries (sponge iron plants in particular). The majority of the iron ores were found to have high iron and low alumina and silica contents. All these iron ores were free from the deleterious elements (S, P, As, Pb, alkalies, etc.). The results indicated lower values of shatter and abrasion indices, and higher values of tumbler index in all the iron ore lumps except Serazuddin (previous) and Khanda Bandha OMC Ltd. For all the fired iron ore pellets, the degree of reduction in coal was more intense in the first 30 min, after which it became small. Slow heating led to higher degree of reduction in fired pellets than rapid heating. All the iron ores exhibited more than a 90% reduction in their fired pellets in 2-h time interval at a temperature of 900°C. Iron ore lumps showed a lower degree of reduction than the corresponding fired pellets.     

Morphology and reduction kinetics of fluxed iron ore pellets

Abstract

The present paper describes studies of the reduction and sintering behaviour, followed by examination of the structural changes taking place, during direct reduction of fluxed composite (ore plus coal) pellets. The kinetics and morphological aspects of the direct reduction of fluxed composite pellets are compared with those for the gaseous reduction of fluxed ore pellets without carbon addition. It is shown that the chemical reaction is the rate limiting factor for fluxed composite pellets, and the mass transport of reactant gas through the reaction product iron layer governs the overall reduction process in the case of fluxed ore pellets. Microscopic analysis of the fluxed composite pellets has indicated no tendency to form a reduction inhibition iron shell towards the end of the reduction, as found in the case of gaseous reduction of fluxed ore pellets under identical reduction process conditions. The effects of basicity, Fe/C, temperature, and other variables on morphological and microstructural changes in the directly reduced fluxed composite pellets have been experimentally investigated in the present work.     

Effect of alumina on slag–metal separation during iron nugget formation from high alumina Indian iron ore fines

Abstract

Iron nuggets can be obtained from ore–coal composite pellets by high temperature reduction. Alumina in the ore plays a vital role in slag–metal separation during nugget formation, as it increases the liquidus temperature of the slag. In this study, the effect of carbon content, reduction temperature and lime addition on slag–metal separation and nugget formation of varying alumina iron ore fines were studied by means of thermodynamic modelling. The results were validated by conducting experiments using iron ore fines with alumina levels ranging from 1·85 to 6·15%. Results showed that increase in reduction temperature enhances slag metal separation, whereas increasing alumina and carbon content beyond the optimum level adversely affects separation. Carbon below the required amount decreases the metal recovery, and carbon above the required amount reduces the silica and alters the slag chemistry. Optimum conditions were established to produce iron nuggets with complete slag–metal separation using iron ore–coal composite pellets made from high alumina iron ore fines. These were reduction temperature of 1400°C, reduction time minimum of 15 min, carbon input of 80% of theoretical requirement and CaO input of 2·3, 3·0 and 4·2 wt-% for 1·85, 4·0 and 6·15 wt-% alumina ores respectively.     

Study of nonisothermal reduction of iron ore-coal/char composite pellet

Cold-bonded composite pellets, consisting of iron ore fines and fines of noncoking coal or char, were prepared by steam curing at high pressure in an autoclave employing inorganic binders. Dry compressive strength ranged from 200 to 1000 N for different pellets. The pellets were heated from room temperature to 1273 K under flowing argon at two heating rates. Rates of evolution of product gases were determined from gas Chromatographie analysis, and the temperature of the sample was monitored by thermocouple as a function of time during heating. Degree of reduction, volume change, and compressive strength of the pellets upon reduction were measured subsequently. Degree of reduction ranged from 46 to 99 pct. Nonisothermal devolatilization of coal by this procedure also was carried out for comparison. It has been shown that a significant quantity (10 to 20 pct of the pellet weight) of extraneous H₂O and CO₂ was retained by dried pellets. This accounted for the generation of additional quantities of H₂ and CO during heating. Carbon was the major reductant, but reduction by H₂ also was significant. Ore-coal and ore-char composites exhibited a comparable degree of reduction. However, the former showed superior postreduction strength due to a smaller amount of swelling upon reduction. Formerly Graduate Student, Department of Metallurgical Engineering, Indian Institute of Technology, Kanpur, India     

硫在含碳球团内的转化行为

为了研究含碳球团还原产品中硫含量过高的问题和出路,笔者借鉴高温法定硫的原理,设计了一套分析测定装置,首次系统地研究了铁精矿配加烟煤、无烟煤和生石灰等原料之后的含碳球团在不同温度、时间条件下硫的分解转化行为,得出了煤种、CaO含量、温度和时间等条件对产品硫含量的影响趋势,分析揭示了试验现象与脱硫反应之间的规律,并对含碳球团的工艺选择与环保的关系进行了相应的论述.