铁浴式熔融还原的终还原规律研究

通过实验研究了铁浴式熔融原终还原过程渣中ＦｅＯ含量的变化规律,发现渣中ＦｅＯ含量随时间的变化是先升高而后又降低,呈明显的山峰形。ＦｅＯ含量最大的时刻即是预还原球团矿的熔化终点。由此得出了“两段式”的终还原理论,并且这一理论在热态冶炼扩大实验中亦得到验证。     

熔融还原炼铁工艺的煤气富氢改质预还原

考虑到二步法熔融还原炼铁过程中终还原煤气降温和提高预还原效率的需要,以Corex为例分析了终还原炉煤气富氢改质后用于预还原的优势,讨论了其不利因素和对策.结果表明,对终还原炉煤气进行富氢改质后用于预还原是可行的.     

微型流化床中气氛对还原度的影响

为了过程优化和提高反应的还原度,设计了两步法试验。试验采用的是微型流化床反应器,能够确保反应器空间中的每一个颗粒都处于相同的温度和气体浓度。试验结果表明,预还原阶段形成的颗粒表观形貌对还原度有着重要的影响,终还原阶段中的CO在混合气体中所占的比例直接影响着还原速率的大小。合理的控制还原反应速率,延长反应时间,有利于还原度的提高。当CO在混合气体中所占的比例为83%时,巴西矿粉的还原度达到了88%。     

铜还原钼酸盐实验研究

基于钨钼的电化学性质差异,以铜为还原剂,在添加EDTA络合剂和无络合剂作用的条件下,研究了EDTA用量、pH值、还原时间、反应温度对钼还原率的影响。结果表明,添加EDTA络合剂不利于钼还原率的提高;反应可采用铜直接还原,选择pH=1.0～1.5、反应温度60℃及延长还原时间,利于钼还原率的提高。     

钒钛磁铁矿二步法熔融还原试验研究

与传统高炉流程冶炼钒钛磁铁矿相比,采用二步法熔融还原工艺有利于回收钒钛磁铁矿中的铁、钒和钛等有价元素。本研究分别在990℃、1200℃、1500℃下进行气体预还原、配碳预还原和熔融还原试验,结果表明：熔融还原的渣铁分离效果良好且铁损较低,铁水钒含量高于高炉流程铁水,钛渣品位可以达到或超过理论品位。攀枝花精矿二步法熔融还原适宜预氧化后采用固体碳预还原,其还原温度应等于或高于1200℃;熔态终还原时可不配碳,终还原应控制钛还原度、（FeO）含量在适宜的范围内。     

金属Cu还原MoO42-的动力学研究

本文对铜还原钼酸盐动力学进行了初步研究.通过还原反应的动力学模型,绘制出其氧化-还原反应机理示意图.同时为了进一步明确其反应机理及动力学过程,采用初始速率法研究还原反应的级数,计算还原反应的活化能,并研究了温度对速率系数的影响.     

流态化技术在熔融还原工艺中的应用

介绍了FINEX、FINMET、Circored和HIsmelt等几种典型熔融还原工艺采用流化床处理粉铁矿的技术及特点。总结了熔融还原中采用流化床处理粉铁矿应遵循的原则。参考国内外有关流化床处理粉铁矿的实践经验,提出了一种采用流化床处理粉铁矿的熔融还原炼铁新工艺流程,按照冶金功能分为4个系统:使用约800℃的还原煤气生产还原度约80%的DRI的流态化预热预还原系统;直接使用粉煤、高温高预还原度炉料、纯氧冶炼,二次燃烧率控制在20%左右的铁浴终还原系统;具有调节和变换终还原高温煤气和循环使用炉顶煤气功能的煤气改质系统;解决输出煤气利用的综合利用系统。     

铁矿石还原气-固还原行为研究现状

系统分析了铁矿石还原性的影响因素以及铁矿石的气固还原动力学特征,铁矿石的化学成分、孔隙率和矿 物组成对其还原性都有影响,总体来看,铁矿石中的碱性氧化物对铁矿石的还原有促进作用,而酸性氧化物对其还 原有阻碍作用。提高铁矿石中微气孔的比例以及提高还原性好的矿物,如铁酸钙的含量可改善铁矿石的还原性; 对于铁氧化物气固还原动力学的研究大多采用未反应核模型,在还原的不同阶段具有不同的限制性环节,比如在 浮士体还原到金属铁阶段,前期还原反应由气体内扩散与界面化学反应混合控制,后期界面化学反应为还原反应 的控制环节。总结前期的研究结果,结合当前资源现状提出了今后铁矿石还原行为的2个研究方向:①加强 Al 2 O 3 、K 2 O、Na 2 O、ZnO等杂质元素和有害元素对铁矿石还原性影响研究;②加强高炉实际含铁原料,如烧结矿、 球团矿和块矿的气固还原动力学研究。     

氧化铁碳热还原过程间接还原规律研究

为了研究碳热还原过程的间接还原规律,在20 kg/h推舟炉加热装备上开展试验,借助在线气体分析仪和金属铁产品的化学成分检测,探讨了煤种、煤粉粒度以及铁精矿粉制备方式等因素对间接还原反应的影响,最后从理论上解析了该反应过程的间接还原来源和定量关系。研究表明:间接还原主要来源于碳热直接还原过程产生的CO与氧化铁间发生的化学反应;步进还原过程中,煤中部分挥发分参与间接反应,使得稳定期煤气中的CO_2/(CO+CO_2)比例超过20%;铁精矿粉粒度越小,还原效果越好,间接还原比例越高。     

新型煤基竖炉直接还原工艺的探讨

本文在热式煤基竖炉的研究基础上，提出预热预还原段采用内热式对流传热和终还原采段采用外热式传导传热相结合的煤基竖炉直接还原新工艺，并设计建造了模拟试验装置，试验表明，模拟试验装置具有操作方便，控制可靠的特点，同时取得了Ｃ／Ｆｅ比为０．５时，预还原时间为３０ｍｉｎ，终还原时间为１００ｍｉｎ，金属化率大于９５％的良好指标。     

熔融还原法冶炼高速钢

对用白钨矿、氧化钼和钒渣冶炼高速钢进行了热力学和动力学的计算与分析。在熔融还原过程中，CaWO4、MoO3、V2O5将被C、CaC2、Si-Fe、SiC还原。反应过程包括：固一固反应、液一固反应、铁浴反应和液一液反应。开发了低温快速还原、控制渣量、抑制沸腾等技术。还原WO3的限制性环节是WO3在熔渣中的扩散，改善渣的流动性，扩大反应界面能加快WO3的还原；使用阻尼剂能有效抑制钼的挥发。用20t的AC电弧炉还原氧化钨矿工业化生产高速钢M-2已取得成功，具有质量高、缩短工序、节约资源、降低能耗、提高成品率和改善环境等优点。综合上述功效，生产每吨M-2钢可节约成本1780元。应用这一新技术，重庆特钢公司累计生产M-2钢7981t。     

熔融还原冶炼高速钢

对用白钨矿、氧化钼和钒渣冶炼高速钢进行热力学和动力学的计算与分析。在熔融还原过程中,CaWO_4、MoO_3、V_2O_5、将被C、CaC_2、Si-Fe、SiC所还原。反应过程包括:固-固反应、液-固反应、铁浴反应和液-液反应。开发了低温快速还原、控制渣量、抑制沸腾等技术。(WO_3)还原限制性环节是WO_3在熔渣中的扩散,改善渣流动性,扩大反应界面能加快WO_3的还原,用阻尼剂能有效抑制钼的挥发。 在20tAC电弧炉用氧化钨矿工业化生产高速钢M-2成功,质量优异,具有缩短工序、节约资源、降低能耗,提高成品率和改善环境等优点。综合上述功效,每吨M-2钢节约成本1780元。应用这一新技术,重庆特钢公司累计生产M—2钢7981t。     

Reduction behavior and mechanism of Hongge vanadium titanomagnetite pellets by gas mixture of H2 and CO

Hongge vanadium titanomagnetite(HVTM)pellets were reduced by H_2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ(H_2)toφ(CO),and pellet size on the reduction of HVTM pellets were evaluated in detail and the reduction reaction kinetics was investigated.The results show that both the reduction degree and reduction rate can be improved with increasing the reduction temperature and the H_2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050°C,ratio ofφ(H_2)toφ(CO)of 2.5,and pellet diameter in the range of 8-11 mm.Under these conditions(pellet diameter of 11mm),final reduction degree of 95.51% is achieved.The X-ray diffraction(XRD)pattern shows that the main phases of final reduced pellets under these conditions(pellet diameter of 11 mm)are reduced iron and rutile.The peak intensity of reduced iron increases obviously with the increase in the reduction temperature.Besides,relatively high reduction temperature promotes the migration and coarsening of metallic iron particles and improves the distribution of vanadium and chromium in the reduced iron,which is conducive to subsequent melting separation.At the early stage,the reduction process is controlled by interfacial chemical reaction and the apparent activation energy is 60.78kJ/mol.The reduction process is controlled by both interfacial chemical reaction and internal diffusion at the final stage,and the apparent activation energy is 30.54kJ/mol.     

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Isothermal reduction experiments of the pellets from Wuhan Iron and Steel Corporation (WISCO) were performed with the thermogravimetry technique in the temperature range from 900?? to 1100?? and under the atmosphere of CO of 100% (volume fraction). The apparent activation energy, reduction rate constant and diffusion coefficient were calculated in terms of the Arrhenius plots and the unreacted core model, respectively, and the rate controlling steps were ascertained accordingly. The microstructure and forms of iron oxides of the pellets at the different reduction stages were observed by FESEM and EDS techniques and the reduction reaction mechanism of the pellets was analyzed accordingly. The results show that the controlling step of the reduction reaction of the pellets is the interfacial chemical reaction during most of the time from the initial stage through the middle and later stage, and it shifts to the solid diffusion at the final stage, and that the pellets reduction proceed in the order from higher oxides to lower oxides of iron and the application of the unreacted core model to the kinetic analysis is appropriate.     

Volume Changes of Iron Oxide Compacts under Isothermal Reduction Conditions

Compacts made from chemically grade Fe₂O₃ were fired at 1473K for 6 hrs. The fired compacts were isothermally reduced either by hydrogen or carbon monoxide at 1073–1373K. The O₂ weight‐loss resulting from the reduction process was continuously recorded as a function of time using TGA technique, whereas the volume change at different reduction conditions was measured by displacement method. Porosity measurements, microscopic examination and X‐ray diffraction analysis were used to characterize the fired and reduced products. The rate of reduction at both the initial and final stages was increased with temperature. The reduction mechanism deduced from the correlations between apparent activation energy values, structure of partially reduced compacts and application of gas‐solid reaction models revealed the reduction rate (dr/dt) at both the initial and final stages. At early stages, the reduction was controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism, while at the final stages the interfacial chemical reaction was the rate determining step. In H₂ reduction, maximum swelling (80%) was obtained at 1373K, which was attributed to the formation of metallic iron plates. In CO reduction, catastrophic swelling (255%) was obtained at 1198K due to the formation of metallic iron plates and whiskers.     

3#宽厚板坯连铸机凝固末端轻压下技术

介绍了宝钢分公司炼钢厂3#宽厚板坯连铸机采用的凝固末端轻压下技术,简述了凝固末端轻压下技术的原理,并对其主要工艺参数轻压下凝固末端的位置及其确定方法、压下率、总压下量和压下速率进行了讨论和分析,介绍了从控制角度这种技术的几种分类方式:静态轻压下、动态轻压下和半动态轻压下.得出结论,凝固末端轻压下技术对减少中心偏析很有效.     

凝固末端轻压下技术在连铸中的应用

文章阐述了凝固末端轻压下技术的原理，介绍了这种技术的几种不同方式，并对其主要工艺参数轻压下的位置、压下率、总压下量、压下速率和拉速等等的确定进行了讨论和分析。对比了一些厂家使用末端轻压下技术的效果。末端轻压下技术对减少中心偏析很有效，对提高产品质量、生产高附加值产品有重要意义。