焦炭床内铁水渗碳行为

高炉冶炼过程中铁水最终渗碳量接近饱和,相比而言,闪速炉中没有固体炉料的压迫作用,无法发生像高炉炉缸内死料柱根部与铁水之间的渗碳反应,最终渗碳量难以预料。为此,以电解铁和化学纯石墨为原料,利用管式电阻炉升温到1 855K熔化铁块,以高纯Ar作为保护气体研究焦炭床内铁水渗碳行为,并对铁水渗碳行为进行数值模拟,为闪速炼铁工业化打下基础。实验结果表明,终铁C含量随焦炭粒度增大和渗碳床高度降低而减小,且铁水初始C含量对终铁C含量具有较大影响。对于不同条件下铁水渗碳反应中C元素的迁移规律,基于VB编程技术进行了数值模拟,模拟结果与高温实验结果较吻合,相对误差在3%以内。渗流速度控制因子始终控制在0.5左右,即铁水在焦炭床中的平均速度为初始滴落速度的一半左右。     

铁渣熔体穿行焦炭床的渗碳机理

由于高炉炼铁工艺流程长、对冶金焦依赖性强,尤其是焦化、烧结、球团等原料制备过程中产生的环境问题,因此该工艺的发展受到严重制约。闪速炼铁工艺是近年来提出的一种新兴熔融还原炼铁技术,发展前景可期。不同于高炉炼铁,闪速炉中没有焦炭死料柱,其铁水渗碳量难以预估。为此,以金属化球团和工业焦炭为原料,设计实验研究焦炭床内铁渣熔体渗碳行为,并基于VB编程对铁渣熔体渗碳行为进行了数值模拟。实验结果表明,球团矿金属化率对终铁C含量有较大的影响,渗碳量(w[C],%)随着金属化率(x)的提高呈指数级增加。当焦炭床高度为50 mm时,拟合而得w[C]=0.014 34+exp((x-84.2)/3.253 48);基于VB编程进行的数值模拟结果与高温实验结果吻合较好,相对误差在10%以内,可直观展示铁渣熔体流经焦炭床时碳含量的变化规律。     

炼铁过程熔融渗碳行为研究

传统高炉冶炼过程中铁水最终含碳量是饱和的,而闪速炉中反应是在物料漂浮阶段发生,没有固态料柱的压迫作用,无法发生高炉炉缸内固体炉料与铁水的渗碳作用,最终铁水含碳量未知。为此对闪速炼铁炉中熔池底部渗碳反应进行了研究。首先,对铁碳相图进行了理论研究,基于此理论分析探讨了反应时间、焦炭粒径、焦炭床层高度及原料失重率等因素对铁水最终含碳量的影响。得出了最佳工艺条件为反应时间240 min、焦炭粒径5～8 mm、焦炭加入量70 g、原料失重率26%,在此最佳工艺条件下含碳量最大为4.73%。为了进一步探究渗碳过程中铁碳合金中元素的分布规律,对含碳量为4.73%的铁碳合金进行了SEM-EDS表征,结果显示条棒状石墨碳呈凝聚态不规则嵌布在铁碳合金中,在石墨碳边缘呈现两种不同衬度,分别为FeC相和Fe_3C相。     

高炉焦炭在铁水中溶解行为研究现状及展望

 在当前及未来大型高炉高冶炼强度的条件下,加快焦炭在铁水中的溶解速率、提高高炉炉缸铁水的碳饱和度是削弱碳不饱和铁水对炉缸炉衬侵蚀、保证炉缸正常工作及延长高炉寿命的重要措施,同时可以为下游的炼钢工序提供部分热量来源。首先对国内外焦炭在铁水中溶解的试验和模拟研究方法进行了概括,然后对焦炭自身结构性能、焦炭中矿物质、铁水的物理性质等影响焦炭溶解速率的因素进行了详细分析。结果表明,碳结构的有序度和铁水温度的升高有利于焦炭的溶解,而焦炭中矿物质及铁水中硫、磷等元素的存在会抑制铁水的进一步渗碳。研究结果为高炉操作者理解焦炭在铁水中的溶解行为提供借鉴,指导钢铁工业的节能减排。     

铁水中碳行为的研究

通过实验室实验和大量现场数据的统计分析，探讨了高炉铁水中碳的饱和程度，详细研究了块状带金属渗碳，滴落带铁滴渗碳和炉缸内铁液渗碳的机理，过程及诸多影响因素，认为在一定范围内铁水中（Ｃ）与炉温的关系比（Ｓｉ）与炉温的关系更显著；（Ｃ）可以作为高炉热状态的一个更为适当的判据。还提出高炉内铁水含碳并不饱和，（Ｃ）不仅可以控制，而且对高炉行程极有影响，因而对铁水中碳行为的研究应当引起足够的重视。     

COREX用焦在铁水中的渗碳特性

 钢铁工业是支撑国民经济发展的基础产业,同时也属于资源和能源密集型行业,随着国家严格的环保政策的逐渐实施,其面临的资源和环保要求日益增加。传统高炉炼铁生产工艺由于存在能耗高、污染物排放多的弊端,发展受到了限制,因此非高炉炼铁工艺的研究和应用日益受到钢铁行业的重视。系统研究了COREX熔融还原非高炉炼铁工艺使用的顶装焦、捣固焦和气煤焦在铁水中渗碳特性,并分析了3种不同样品在铁水中的渗碳动力学行为。研究结果表明,高温铁水与碳原子接触时发生渗碳反应的吉布斯自由能远小于Fe₃C生成反应的吉布斯自由能,焦炭与高温铁水接触被消耗的过程以渗碳反应为主。顶装焦、捣固焦和气煤焦3种焦炭样品与高温液态铁水接触后迅速发生渗碳反应,铁水中碳含量快速增加,但铁水中碳含量增加的幅度随着铁水中碳含量的升高而快速降低,在渗碳反应时间超过120 min后铁水中的碳含量基本保持恒定。3种焦炭在铁水中的渗碳速率由高到低分别为气煤焦、顶装焦和捣固焦,铁水温度对渗碳过程具有明显的影响,随着温度的升高,渗碳速率和最终铁水中的碳含量增加。动力学分析表明,捣固焦在铁水中的渗碳活化能最高,顶装焦次之,气煤焦最小。     

高炉内渣铁焦界面润湿行为研究现状及展望

 高炉作为目前世界上最大的移动床式冶金反应器,保持高炉内良好的透气透液性是保证高炉稳定顺行的关键。高炉内部被软熔带分割开来,分为上部固体散料区和下部固液共存区,下部的固液共存区是决定高炉透气透液性和煤气流分布的重要区域,因此若想明晰高炉影响透气透液性的关键,必须对高炉下部固液共存区的反应进行全面研究。高炉高温区焦炭床与渣铁的相互作用行为是决定铁-焦-渣交互作用及高炉透气透液性的重要因素,调控好液态渣铁与焦炭床的润湿性变化,可以有效改善高炉内部的透气透液性,最终会影响高炉生产效率和稳定性。因此,明晰高炉内渣铁焦的界面润湿行为显得尤为重要。首先对界面润湿现象进行了概述;然后详细从铁水成分以及焦炭性质对铁-焦界面润湿行为的影响进行了总结;其次详细分析了炉渣温度、炉渣成分以及焦炭自身性质对渣-焦界面润湿行为的影响。结果表明,目前高炉内渣铁焦界面润湿行为的研究已经从实验室试验以及基础模拟方面进行了研究,研究结果可为高炉操作者理解高炉内渣铁焦界面润湿行为提供初步理论指导,但仍需在可反映高炉内实际复杂情况的润湿行为变化方面进行深入研究。     

铁水温度对炭砖坩埚动态侵蚀的影响研究

在实验室条件下,考察了不同铁水温度下、炭砖和焦炭同时作为渗碳碳源时,炭砖的侵蚀速率和焦炭的溶解速率及炭砖微观结构的变化。结果表明:在实验范围内,随着铁水温度升高,炭砖侵蚀速率和焦炭溶解速率加快,且焦炭的溶解速率远大于炭砖坩埚的侵蚀速率,说明铁液更易与焦炭发生渗碳反应;侵蚀后的炭砖分层明显,并且有清晰的铁液渗透通道。由此得出,在高炉实际生产中,添加渗碳性能好的焦炭以及定期更新炉缸内死料柱可在一定程度上缓解铁液对炉缸炭砖的侵蚀,从而实现高炉长寿。     

焦炭在铁水中溶解的动力学实验

高炉冶炼过程中铁水最终渗碳量接近饱和,相比而言,闪速炉中没有固体炉料的压迫作用,无法发生像高炉炉缸内死料柱根部与铁水之间的渗碳反应,最终渗碳量难以预料。以还原铁粉和化学纯石墨为原料,利用管式电阻炉升温到1 855K熔化铁粉,以高纯N2作为保护气体研究焦炭在铁水中溶解的动力学,为闪速炼铁工业化打下基础。实验结果表明,在自然对流条件下,不考虑溶解速率系数kt随溶解时间的变化时,得到了各组实验条件下确定的kt值分别为4.20μm/s(第1组)、5.28μm/s(第2组)和6.50μm/s(第3组);考虑溶解速率系数随溶解时间变化时,焦炭的kt值随着溶解时间的增加而降低,且仅受传质控制;当铁碳熔体中有硫存在时,溶解速率随着铁浴中硫含量的增加而降低。     

碳循环氧气高炉内软熔带上部炉料反应行为

近年来，在中国“碳达峰”“碳中和”战略背景下，低碳高炉炼铁已成为中国低碳冶金技术发展的重要方向。在高炉炼铁工序，由于大量使用化石燃料及炉顶煤气利用率低，导致CO₂排放量过多。为降低高炉炼铁的碳排放，提出富氢碳循环氧气高炉新工艺。以碳循环氧气高炉为研究对象，通过数值模拟与实验室试验相结合的方式，对高炉内软熔带上部含铁炉料的还原行为和焦炭气化行为进行了研究。通过SEM-EDS对烧结矿和球团矿的还原程度及渣铁分离现象加以分析，同时采用矿相显微镜对焦炭气化后的微观形貌进行表征。通过数值模拟和实验室试验得到的高炉内含铁炉料还原度变化规律基本一致，验证了数值模拟与实验室试验相结合方法的可行性。研究表明，在高炉的同一竖直方向上，随着位置的降低，含铁炉料的还原度和金属化率不断升高，焦炭的气化率不断上升。在高炉中心位置软熔带上方，含铁炉料的还原度为0.91,金属化率为67.58%,焦炭的气化率为20.91%。在高炉边缘位置软熔带上方，含铁炉料的还原度为1,金属化率为96.91%,焦炭的气化率为21.36%。并且，随着炉料下行，还原后含铁炉料的金属铁面积越大，渣铁分离越明显，观察到的...     

Kinetic experiment of dissolving coke in molten iron

The liquid iron carburization in the blast furnace process can almost come to a saturation state, while, that in flash ironmaking process is unexpected, since there is no solid charge that will press the hot metal and no carburization reaction that occurs between the bottom deadman. In order to study the kinetics of coke dissolution into the molten iron in flash iron- making process, a series of experiments were carried out. Reduced iron powder and chemically pure graphite were used as raw materials, and the tubular resistance furnace was employed to heat the samples up to 1855K and melt them, and the high- purity N2 was injected as the protective gas throughout the experiments. The experimental results show that without regard to the factor kt of dissolution rate, the values of kt under natural convection condition are 4. 20??m/s in group 1, 5. 28??m/s in group 2 and 6. 50??m/s in group 3. On the contrary, when taking this factor into account, kt decreases with time increase and only can be controlled by the mass transfer. Besides, when there is sulfur in the iron- carbon melts, it shows that kt also decreases with the increase of sulfur content.     

高炉炉缸碳源渗碳性能及动力学

摘要：提高铁水碳饱和度,减弱侧壁炭砖侵蚀,实现炉缸长寿对高炉炼铁具有重要意义。利用静态法系统地研究了高炉系统中进入炉缸铁水的碳源的渗碳性能,并计算了表观反应速率常数K。研究结果表明,不同碳源的渗碳性能由强到弱为：NMA炭砖>碳棒>煤粉>焦炭>9RDN炭砖。碳源的渗碳性能随其石墨化程度的升高而降低。碳源中的灰分会极大影响其渗碳性能,但以团聚大颗粒形式存在的灰分并不能减弱其渗碳能力,同时Al2O3可明显降低碳源的渗碳速率。9RDN炭砖的渗碳性能低,预示着其可适应更加复杂的炉况条件。煤粉和焦炭渗碳性能偏差,煤粉以及炉料下行过程形成的焦粉进入炉缸会降低死料柱空隙度,造成炉缸不活跃,使得炉况波动频繁,并不利于死料柱渗碳和侧壁保护层的稳定。因此,要适当提升入炉焦炭粒度,增大风量,减弱未燃煤粉及焦粉对炉缸侧壁炭砖长寿的负面影响。     

Carburizing performance and kinetics of carbon sources in blast furnace hearth

It is of great significance to improve the carbon saturation of molten iron which weakens the erosion of sidewall carbon bricks, so as to realize the hearth longevity. Carburizing properties of various carbon sources in molten iron by static method was systematically investigated. The apparent reaction rate constant K of samples was calculated. The results show that the carburizing properties of different carbon sources from strong to weak are NMA carbon brick > carbon rod > pulverized coal > coke > 9RDN carbon brick. The carburizing performance of carbon sources decreases with the increase in its graphitization degree. Ash has a negative effect on the carburizing performance of carbon sources, but ash in the form of agglomerated large particles cannot weaken the carburizing performance of carbon sources. The Al2O3 phase can obviously degrade the carburizing performance of carbon sources. The 9RDN carbon bricks with low carburizing properties can be adapted to more complex furnace conditions. The carburizing properties of pulverized coal and coke are relatively weak. When the pulverized coal and coke powder formed in the tuyere raceway enter the hearth, the porosity of the deadman will be reduced, resulting in hearth inactivity and frequent fluctuation of furnace condition, and it is not conducive to the carburization of the deadman. Therefore, it is necessary to properly improve the coke particle size and increase the air volume for weakening the negative effects of unburned coal powder and coke powder on the longevity of the hearth sidewall carbon bricks.     

基于图像处理的高炉炉缸死铁层中焦粒信息分析

 高炉铁口水平线下(死铁层区)死料堆的位置、大小、孔隙度、更新速度等直接决定铁水及炉渣在炉缸内的流动方式,同时影响炉缸传热、耐材的侵蚀、铁水及渣的排出速度等。使用图像处理技术对莱钢1 880 m3高炉浸入死铁层中死料柱下部形状、孔隙度、焦粒尺寸、形貌分布等关键信息进行了提取。通过分析计算得到死料柱下部焦层二维孔隙度为56.73%。该区域焦粒平均粒度为15.3 mm,缩减了约70%。通过形貌分析发现炉缸死铁层中焦炭更接近椭球状,该现象说明自炉顶装入后焦炭各方向消耗速度不一致,具有明显的取向性。该高炉内渣铁通过炉缸该区域死料柱焦粒过程中,水平方向与竖直方向冲刷程度较深。有助于对高炉炉缸“黑箱”进行信息解析,进一步加深操作者对于高炉冶炼过程中死料柱下部及炉缸工作状态的认知。     

Investigation of Reduction and Smelting Mechanism in the Hi‐QIP Process

A new coal‐based reduction and smelting process for production of high quality iron pebbles in a rotary hearth furnace (Hi‐QIP Process) was developed. The reduction, carburization, smelting, and separating mechanism of the Hi‐QIP process were investigated. The experiments were carried out in a graphite heater furnace under rapidly heating up to 1773 K. A mixture of coal and ore produced molten metal and slag, which were held on the coal and did not come into contact with the refractory located under the coal layer. It is confirmed that the reduction of wettability between the iron and slag promotes the separation of them, when the content of FeO slag decreases. High productivity of the process is expected when using iron ore with small particle diameter and low gangue content. Favourable operating results were obtained in a pilot test using a rotary hearth furnace with a diameter of 7 m and a width of 1.5 m. This test demonstrated the possibility of continuous production of iron pebbles with high productivity (15t‐iron/d).     

Simulation and application of pulsating bottom-blowing in EAF steelmaking

Pulsating bottom-blowing was proposed to strengthen the electric arc furnace (EAF) molten bath stirring. The fluid flow characteristics and stirring effects of different pulsating bottom-blowing modes on EAF molten bath were studied through water model experiments and numerical simulations. The mixing time was measured by water model experiments and the flow field characteristics of EAF molten bath were simulated by numerical simulations. Compared with conventional bottom-blowing, pulsating bottom-blowing can accelerate the fluid flow velocity and improve the stirring of molten bath. With pulsating bottom-blowing, the molten bath fluid flow field is more disorder, the fluid flow velocity increases and the dead zone volume decreases. Compared with EAF steelmaking with conventional bottom-blowing conditions, pulsating bottom-blowing technology can improve the metallurgical effects and the molten steel quality in EAF steelmaking with lower FeO content of final slag, lower phosphorus content and carbon-oxygen equilibrium of final molten steel, and lower temperature deviation.     

Reduction and Carburization of Iron Oxide by Carbonaceous Materials

The iron nugget making process, where mixtures of iron ore powder and pulverized coal are made to heat rapidly, is regarded as a new ironmaking process. Since the iron carburization reaction is an especially important step from the viewpoint of energy saving in this process, the purpose of this study is to reveal the carburization mechanism of reduced iron formed during the heating process of the mixtures. Fe₂O₃ and H₂‐CO‐CO₂ gas mixture were made react with each other to simulate the formation of iron ore and the generation of coal gas from coal during the heating process. An electric resistance furnace was used to heat the samples. A cut surface of the quenched iron product was observed by microscopy. Carbon content in the iron was analyzed after reduction and carburization of Fe₂O₃. It is considered that there are many possibilities in the real process to carburize the reduced iron during the heating process, such as carburization with CO formed by coal combustion, solution loss reaction, and direct carburization with coal. It was observed in the present work that the carbon content in the reduced iron became the highest as Fe₃C was formed during the heating process. Therefore, it became clear that the key technology for production of pig iron containing high carbon was to control the formation of Fe₃C in the heating period of the mixture. The carburization mechanism was discussed in this study based on these experimental results.     

Research on deadman state during tapping process

In this paper, a deadman state model is established. According to the actual operation parameters of 5500?m³ blast furnace (BF) in Shougang Jingtang United Iron and Steel, the influence of taphole depth, deficient iron amount and salamander depth on deadman state is discussed. Meanwhile, the relationship between deadman state and differential pressure of BF is analysed. The results show that deadman of 5500?m³ BF is floating during regular production and the range of floating height is 0.23–0.30?m. When the mud mushroom cannot be formed or cracks during tapping process, the range of floating height is 0.38–0.45?m. The upward movement of deadman can result in the reduction of coke size and porosity, which is one of the key factors that causes holding hot blast.     

高炉内铁?焦界面的渗碳润湿行为研究

高炉内铁水渗碳过程是影响冶炼效率及未饱和铁水对炉缸炉衬侵蚀的重要因素。本文通过高温真空润湿性测试装置模拟了高炉炉缸区的铁水渗碳反应,分析了不同碳质量分数（3.8%、4.3%、4.8%）的Fe?C熔体与质量分数为99.9%的石墨基体在高温下界面间的润湿反应,同时利用扫描电镜（SEM）和能谱仪（EDS）研究了渗碳界面的微观形貌及渗碳距离。结果表明:界面接触角随着Fe?C熔体中碳含量的增加而变大;熔化过程中,接触角随着反应时间延长而减小,并最终趋于稳定;4.8%碳质量分数的Fe?C熔体中由于含碳量已至饱和,处于不润湿状态。扫描电镜分析显示,Fe?C熔体与石墨基体的接触界面形成了“球帽状”凹陷,凹陷半径与体积随碳含量的增加而减小。能谱线扫描分析显示,随着Fe?C熔体中初始碳含量的增加,石墨基体中的碳素溶解量减少,渗碳效果变差,良好的润湿性有利于碳的传质。通过计算表面能发现,石墨基体中碳素溶解进入Fe?C熔体后,有效减小了两者之间的表面能,使得表面张力减小,接触角在熔化期间递减。