粉尘含碳球团还原方式及气氛对其还原挥发性能的影响

在１１５０℃和１２５０℃，０．１Ｌ／ｍｉｎ和１０Ｌ／ｍｉｎ的气量下，对通入含不同ＣＯ２量的氮气影响粉尘含碳球团还原速度的实验研究表明，以滚动方式所造球团中氧化物的还原完全以间接还原方式进行，气氛中非还原气体流速（或流量）的增加对粉尘含碳球团氧化铁不速度有显著的降低作用，但还原温度提高则气量增加造成的氧化铁还原速度降低有显著和抵消作用，气氛对球团中的挥发速度影响很小，对铅的挥发速度几乎不产生影响。     

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     

转底炉工艺系统基本化学反应的热力学分析

转底炉工艺是直接还原中煤基还原的一种,其内部的热力学反应主要包括含碳球团的自还原反应、含碳球团与氧化性气体间的氧化反应、含碳球团的脱碳反应、含碳球团排出气体的燃烧反应及喷吹焦炉煤气对直接还原的影响等5个部分。对转底炉内部温度、气氛、配煤比的控制,是转底炉直接还原工艺的关键。     

含碳球团气固协同还原特点及动力学研究

通过热重实验,从还原温度、还原气氛及还原时间三方面对含碳球团的还原特点和动力学进行了研究,采用界面反应模型、三维扩散模型等对含碳球团还原过程进行拟合.研究表明:在本实验条件下,当温度为1100℃、气氛为单一H2、还原时间为60 min时,反应分数达到最大值0.81,还原效果最佳;还原过程中,还原速率先迅速增大,随后逐渐减小;当假设扩散模型为还原过程的限制性环节时,得到的拟合效果最好,反应活化能为93.18 kJ/mol.     

冷固结含碳球团用于COREX的可行性研究

通过对采用不同粘结剂的３组冷固结含球团的物化性能，冶金性能的试验检测，以及固定床、移动床竖炉模拟ＣＯＲＥＸ预还原的试验研究，探讨冷固启才用于ＣＯＲＥＸ工艺的可行性。试验结果表明，冷固结含碳球团的化学成分和高温冶金性能均能满足ＣＯＲＥＸ预还原的要求，并可以提高整个ＣＯＲＥＸ工艺的生产率，但其机械强度有待进一步提高。     

含碳球团竖炉直接还原试验研究

文中报告了９００～９７０℃下含碳球团竖炉直接还原热模拟试验的结果,试验结果表明：含碳４％～８％冷固结含碳球团的冶金性能,可以满足竖炉直接还原的要求;同时发现在含碳球团竖炉直接还原过程中,仍以气体还原为主,但固体碳直接还原的比例随温度升高而增加。并研究了含碳球团竖炉直接还原的规律和工艺参数。     

烧结烟气脱硫石膏含碳球团还原脱硫实验研究

基于含碳球团减重还原实验,研究了还原剂摩尔比、反应温度、气氛、添加剂对脱硫石膏还原脱硫的影响。还原实验结果表明,脱硫石膏含碳球团还原脱硫最适宜的工艺参数是n(C)/n(CaSO₄)为0.5～0.6,反应温度1 150℃,H₂气氛,添加剂的作用不明显。综合实验结果表明,扩大实验量级不会降低含碳球团脱硫石膏的脱硫效果,由此可指导扩大试验。     

含碳铬矿球团还原热力学研究

本文介绍了含碳西藏铬矿球团的还原顺序。Ｘ射线衍射证明：还原温度低于１２００℃时，还原产物是Ｆｅ及Ｃｒ_２Ｏ_３；还原温度高于１２００℃时，还原产物是Ｆｅ、Ｆｅ_３Ｃ、（Ｃｒ，Ｆｅ）_７Ｃ_３，在还原初期阶段生成的Ｆｅ转变成Ｆｅ_３Ｃ_，最终转变成（Ｃｒ，Ｆｅ）_７Ｃ_３；当还原温度高于１３００℃时，发现有ＭｇＡｌ_２Ｏ_４，ＭｇＳｉＯ_４生成，热力学计算的结果与Ｘ射线衍射结果相符。     

冶金尘泥含碳球团直接还原机制的试验研究

摘要：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,3~5min就能达到碳气化和铁氧化物还原剧烈进行的温度。在1270℃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CO2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。     

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。     

Numerical Analysis of Complicated Heat and Mass Transfer inside a Wustite Pellet during Reducing to Sponge Iron by H2 and CO Gaseous Mixture

Heat and mass transfer through a wustite pellet during converting to sponge iron was investigated.Pellet was reduced by agaseous mixture containing CO and H_2.The grain model was considered to simulate gas-solid reaction rate.A finite volume method(FVM)was implemented for solving the governing equations.The heat transfer mechanism around the pellet includes radiation and convection and within the pellet,effective heat transfer is considered as a blend of particles conduction and intraparticle radiation.Heat and mass distribution along the radius of pellet for two cases of reducing gases composed of pure H_2 and pure CO was investigated.Local fractional reduction through the pellet was plotted to examine the heat and mass transfer behavior within the pellet and find their relevance with reduction degree.Afterwards,the impacts of pertinent parameters including gas ratio,pellet size and porosity were studied.     

转炉应用CO2技术

 通过对转炉顶吹CO2的热力学分析,结合实验室模拟转炉顶吹O2＋CO2混合气体试验结果,确立了CO2在转炉中应用的关键参数。得出在转炉中顶吹纯CO2虽可脱碳,但温降较大,顶吹CO2供气强度为3.0 m3/(t·min)时,钢液温降速率为15.1 ℃/min;通过喷吹O2＋CO2混合气体可实现温度平衡,但CO2配比的最大理论比例为79.1%;随着混合气体中CO2比例增大,吹炼终点钢液碳氧积降低,当[φ(CO2)∶][φ(O2)＝1][∶]1时可控碳氧积为(25～32)×10－8。     

Reduction of Solid Iron Oxide by Carbon

The reduction of pre‐reduced iron oxide by carbon was investigated from a kinetic viewpoint. The experimental procedure included thermogravimetric analysis to measure the weight change of the iron oxide pellet. The activation energy of the overall reaction was calculated to be 210 kJ/mol in the temperature range from 1273 to 1573 K. The overall reduction rate of FeO by carbon is believed to be mixed‐controlled by the Boudouard reaction and by the FeO reduction by CO gas in the temperature range investigated. The critical carbon concentration for the FeO reduction was estimated under the assumption that the activities of FeO and Fe are unity.     

Reduction Behaviors of Pellets Under Different Reducing Potentials

Owing to the change of gas composition in top gas recycling-oxygen blast furnaces compared with traditional blast furnace, many attentions are attracted to the research on iron oxide reduction again. In order to study the influence of H₂ and CO on the reduction behavior of pellets, experiments were conducted with H₂-N₂, CO-N₂ or H₂-CO gas mixtures at 1173 K by measuring the mass loss, respectively. It was found that the reduction degree increased with increasing the ratio of H₂ or CO in the gas mixture, but the reduction with hydrogen was faster than that with carbon monoxide. The reduction degree could reach 96. 72% after 65 min for the reduction with 50% H₂ + 50% N₂, while it is only 53. 37% for the reduction with 50% CO+ 50% N₂. The addition of hydrogen to carbon monoxide will accelerate the reduction because the hydrogen molecules are more easily chemisorbed and reacted with iron oxide than carbon monoxide. A scanning electron microscope was used to characterize the structures of reduced samples. Dense structure of iron was obtained in the reduction with hydrogen while the structure of iron showed many small fragments for the reduction with carbon monoxide. At the later stage of reduction with the gas mixtures containing carbon monoxide, the reduction curves showed a descending trend because the rate of carbon deposition caused by the thermal decomposition of carbon monoxide was faster than the rate of oxygen loss. Compared with the reduction with CO-N₂ and H₂-CO gas mixtures, H₂ gas could enhance the carbon deposition while N₂ gas would reduce this phenomenon. The results of X-ray diffraction and chemical analysis demonstrated that the carbons are mainly in the form of cementite (Fc₃C) and graphite in reduced sample.     

转炉四元熔渣中锰矿含碳球团焰化行为模拟研究

采用实验模拟与数值模拟相结合的方法,对锰矿含碳球团在转炉4元熔渣（51CaO-16SiO₂-10MgO-23FeO）中的熔化行为进行研究。结果表明,锰矿含碳球团在熔渣中还原时生成了固态产物层,减少固态产物层的厚度和存在时间,能加快球团在熔渣中的还原速度;基于一维非稳态导热微分方程建立了含碳球团熔化过程的数值模型,模型计算与实验结果能较好吻合;采取不同条件进行模拟计算发现,当熔渣温度为1 600℃时,假设固态产物层不存在,球团还原时间可缩短35%左右;对锰矿含碳球团进行预热、适当缩小球团直径及降低还原产物熔点均能减少固态产物层存在时间,从而提高球团还原速度。     

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.     

The influence of carbon deposition on the reduction kinetics of commercial grade hematite pellets with CO,H2, and N2

Experimental measurements are reported on the rate at which commercial grade, low silica hematite pellets react with a gas mixture consisting of CO, H₂, and N₂ over the temperature range 500 °C to 1200 °C. Systems of this type are of considerable practical interest, both regarding the operation of direct reduction processes and ironmaking in the blast furnace. The results of the work may be summarized as follows: No carbon deposition was found when operating the system above 900 °C and in the absence of CO gas. When operating the system below 900 °C carbon deposition occurred, which in effect prevented the normal conversion from reaching completion. The maximum rate of carbon deposition was found to occur between 500 °C and 600 °C. In general hydrogen (in the presence of CO) tended to promote carbon deposition, while the presence of nitrogen appeared to retard the deposition process. When the reaction process was being carried out below 900 °C with CO + H₂ gas mixtures, the reduction process occurred simultaneously with carbon deposition. At lower temperatures, say around 500° to 600 °C, the deposition process dominated, while at the higher temperatures, and particularly at a high hydrogen content of the reactant gas, the reduction process was dominant. The structural examination of the partially reacted specimens has shown that the carbon deposited was found primarily in the form of elemental carbon rather than cementite. Furthermore, X-ray analysis of the free pellet surface has indicated that iron was present in the carbon deposit phase. The practical industrial implications of these findings are discussed in the paper.     

高铝高硫低品位铁矿粉还原熔分制备珠铁

 基于转底炉珠铁工艺,以一种高铝高硫低品位铁矿粉和无烟煤为原料,在实验室条件下进行了还原熔分试验研究,考察了温度、配碳量、碱度和添加剂对高铝铁矿含碳球团还原熔分行为的影响,并分析了碱度和添加剂对珠铁中硫质量分数的影响。试验结果表明,温度为1 350～1 450 ℃时,空白球团熔分效果较差,金属铁渗碳量较低;提高配碳量,金属铁渗碳量略有增加,但熔分效果仍较差;碱度增加会促进球团还原,1 450 ℃时,碱度为0.6、0.8、1.0、1.2的球团可以实现渣铁良好分离,珠铁中硫质量分数逐渐降低,碱度为1.2时降低较明显;Na2CO3配比增加,球团熔分也会逐渐变差,1 450 ℃时球团基本均可以熔分,珠铁中的硫质量分数逐渐降低,但脱硫效果不明显;当碱度为1.2、Na2CO3配加为8%、CaF2配加为4%时,球团可以在1 450 ℃下良好熔分,脱硫效果显著,珠铁中硫质量分数为0.085%,脱硫率达到96.5%,所得珠铁基本满足炼钢要求。     

ABSTRACTS——From the Journal of Iron and Steel Research( in Chinese)2000 ,12(4)—2000 ,12(6)

Effect of Binder on the Reduction of PelletContaining Coal CharJIAN G Wu- feng1,L I Yun- gang1,ZH AO L i- guo1,L U Qing1,LIU Yu- quan2 (1.H ebei Institute ofTechnology,Tangshan0 6 30 0 9,China;　 2 .TianjinTiantie Metallurgical Group Co,H andan 0 56 4 0 4 ,China)Abstract:It was tested that water glass is an ideal binder tothe pellet containing coal char.The effect of binder (waterglass) on the reduction of pellet containing coal char in anitrogen atmosphere and at the temperatu…     

富氢气氛下不同含铁炉料的还原行为

 高炉低碳富氢冶炼技术如高炉喷吹煤粉、富氢燃料等会导致炉内炉腹煤气中氢气体积分数增加,为探究富氢对高炉上部炉料的影响,对富氢条件下不同含铁炉料的还原行为进行了试验研究。粉化试验结果表明,在20%H₂(体积分数)条件下,块矿和烧结矿的粉化率明显改善,RDI_{>3.15 mm}分别增加了11.08%和30.23%,同时富氢条件有利于含铁炉料粒度的均匀化。还原试验结果表明,在CO体积分数不变、改变H₂加入量条件下,球团矿和烧结矿还原度最高时的H₂体积分数为25%,块矿H₂体积分数则为10%。在保持(CO+H₂)体积分数30%不变、改变H₂加入量时,当H₂体积分数超过20%时,各含铁炉料的还原度均超过90%。扫描电镜分析结果表明,还原后的块矿明显生成渣相和铁相,球团矿出现良好的赤铁矿和磁铁矿相,烧结矿则呈“针状铁酸钙相-磁铁矿相-铁相”分层现象。