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。     

Mass Loss and Direct Reduction Characteristics of Iron Ore-coal Composite Pellets

Mass loss and direct reduction characteristics of iron ore-coal composite pellets under different technological parameters were investigated. Meanwhile, changes of iron phase at different temperatures were analyzed by using X-ray diffraction （XRD）, and characteristics of crushed products were studied by using a scanning electron microscope （SEM）. The results showed that heating rate had little influence on the reduction, but the temperature played an important role in the reduction process. The mass loss rate increased rapidly from 800 to 1 100 ℃. The reduction process can be divided into three steps which correspond to different temperature ranges. Fe2 03 began to transform into Fe304 below 500 ℃, and FeO was reduced into Fe from 900 ℃. At 900 ℃, the reduction product showed a clear porous structure, which promoted the reduction progress. At 1000 ℃, the metallic Fe dominated the sample, and the reduction reached a very high degree.     

氧化物杂质对铁氧化物还原动力学的影响

系统分析了氧化物杂质对铁氧化物还原动力学的影响及其机理。发现：各种杂 特点与杂质浓度、存在开矿和／或加入方法,样品的初始化学组成和物理性状,还原剂的种类、反应温度、还原分数等多种因素有关。     

Analysis of Product Morphologies and Reaction Mechanisms on Gaseous Reduction of Iron Oxides

It is well established that in gaseous reduction processes solid iron oxides exhibit a wide range of reducibilities. Using the interface stability criteria developed to describe the decomposition of metal compounds in reactive gas atmospheres, together with microstructural evidence obtained under well characterised reaction conditions, the relationships between product structures, and the mechanisms and the kinetics of reduction of iron oxides have been examined. It is shown that the structures and reaction rates can be explained through the occurrence of four principal mechanisms; continuous gas pore formation, dense metal layer growth, discontinuous metal layer breakdown and continuous coupled growth of metal and pores. Through identification of the critical conditions for these different mechanisms, the maximum rates of reduction of a given starting material as a function of temperature, thermal history and gas conditions can be more clearly understood.     

白云鄂博铁矿球团富氢还原动力学研究

针对气固直接还原工艺中存在着气体利用率低和还原供热不足等问题,利用恒温热重分析(TG)法,研究了氢/碳比率对白云鄂博铁精矿还原速度的影响。结果表明,在还原试验开始后40 min内,还原速率随wH2/wCO比增加而增大,使得Fe2O3→Fe3O4反应时间缩短。基于气相内扩散和界面反应的球团还原速度方程均能较好地处理本研究的数据,得到了反应速度常数与wH2/wCO的关系为:k界面=-0.1975+0.3 575wH2/wCO,k扩散=0.171 01+0.269 7wH2/wCO。根据Arrhenius方程计算出界面反应和气相内扩散活化能分别为26 k J/mol和44 k J/mol,因此本研究条件下限制性环节为气体内扩散控制。     

转底炉生产直接还原铁的工业性试验

为验证转底炉生产直接还原铁的可行性和经济性,采用云南铁矿资源组织开展了转底炉生产直接还原铁的工业性试验,共生产金属化率为79.29%的直接还原铁991.67 t。主要技术经济指标为:还原剂煤耗301 kg/t,发生炉煤耗290 kg/t,生产成本1 179.23元/t。试验结果为转底炉直接还原铁工艺的开发提供了理论依据。     

含碳球团直接还原过程的数值模拟

基于质量守恒方程、能量守恒方程及化学反应速度式,建立了描述含碳球团直接还原过程的数学模型,用此模型所做的数值计算结果与试验结果基本吻合。数值模拟结果表明:影响含碳球团还原速率的最重要因素是炉温,含碳球团应在尽可能高的炉温下焙烧;虽然大球的还原速度开始阶段较慢,但焙烧时间足够长时,不论球大小,都可达到高金属化率;只有配碳量足够时才能获得较快的还原速率和较高的还原度。     

钒钛磁铁矿直接还原实验研究

在实验室条件下研究了钒钛磁铁矿直接还原特点,摸索了还原温度、还原时间、还原气氛和配碳量对直接还原金属化率的影响.结果表明,还原温度和气氛是影响金属化率的最重要因素,温度达到1 300℃以上,还原时间达到20 min以上,维持还原过程中性至还原性气氛,球团金属化率可稳定保持在90%以上.同时分析了还原后金属化球团的岩相组成,比较了钒钛磁铁矿与普通矿直接还原的差异.     

铁精矿氧化球团微波加热直接还原新方法

传统加热直接还原具有热效率低、球团"冷中心"和废热废气量大等问题,造成还原时间长、能耗高和污染大。试验利用微波的选择加热、快速加热、体积加热和清洁干净等优点,以及铁矿球团和无烟煤强的吸波特性,开发了铁矿球团煤基微波竖炉直接还原这一新工艺。研究表明,铁矿球团外配煤粉在1 050℃的微波加热条件下还原焙烧65min,可以获得95.25%的金属化率,同时具有1718.88N/个的抗压强度。与常规加热相比,微波加热还原焙烧的时间可以缩短27.78%,抗压强度增加近1倍,而且还原过程产生的废热废气量很少。     

钒钛铁精矿内配碳球团直接还原的动力学

采用等温还原试验并结合热力学反应数据,对钒钛铁精矿内配碳球团直接还原的还原反应进行了分析.以还原反应发生10min为边界点,将反应过程分为前期和后期两个阶段,建立了还原过程的动力学模型.结果表明,钒钛铁精矿内配碳球团直接还原的还原度随反应温度的升高而增大.温度越高,球团在反应前期还原度的增加速率越大,达到的最终还原度越...     

石人沟矿敞焰煤基直接还原的实验研究

以石人沟矿为原料,石油焦为还原剂,根据正交实验原理,在盖碳敞焰加热条件下,进行了直接还原的实验研究.通过研究获得了海绵铁生产工艺的合理操作参数.实验结果同时也表明,利用石人沟矿可以生产出全铁和金属化率均大于90%的海绵铁.     

钒钛磁铁精矿直接还原反应行为及其强化还原研究

通过在钒钛磁铁精矿中添加还原煤粉和少量添加剂,研究了还原温度、还原时间和添加剂等因素对钒钛磁铁精矿金属化率的影响,并对添加剂强化还原机理进行了探讨.结果表明:还原温度、还原时间、碳铁摩尔比及添加剂对金属化率的影响较大.在还原温度1200℃、还原时间120 min的条件下,未添加添加剂时金属化率最高可达84.5%;添加质量分数3.0%Na₂CO₃或CaF₂的条件下,钒钛磁铁精矿的金属化率可以分别达到96.5%和93.3%.     

含钒钛铁精矿氧化球团气基竖炉直接还原模拟试验

我国钒钛磁铁矿资源丰富,但综合利用难度大,现有工艺仍存在一些问题,工艺流程还有待完善和革新。气基竖炉直接还原-电炉熔分新工艺为钒钛磁铁矿资源清洁高效综合利用提供了新途径。以含钒钛的铁精矿为原料制备氧化球团,模拟气基竖炉直接还原条件,研究了还原气组分和温度对球团的还原进程、还原膨胀以及还原强度的影响。结果表明:以钒钛铁精矿为原料,配加1%膨润土,在1 250℃下焙烧20 min后,所制备氧化球团性能良好,具有较高的抗压强度。在恒定还原气组分(纯H2、H2/CO=2.5、H2/CO=1、H2/CO=0.4和纯CO)和温度(850、900、950和1 000℃)下,钒钛铁精矿球团还原速率快、还原膨胀率小(<20%),可满足气基竖炉直接还原工艺要求。煤制气-气基竖炉直接还原凭借其能耗小、环境友好、单机产能大、产品质量好等优点,将在钒钛磁铁矿资源高效清洁综合利用领域得到发展。     

外包法直接还原钛铁矿过程的动力学研究

采用外包还原剂的方法对钛铁矿进行直接还原试验,研究了直接还原钛铁矿的动力学。结果表明,半焦粉直接还原钛铁矿分为两个阶段,第一阶段是升温阶段和恒温的初始阶段,受界面化学反应控制,表观活化能为113.14kJ/mol;第二阶段为恒温阶段,受固相中气体的内扩散控制,表观活化能为180.13kJ/mol。温度对还原度和还原速率的影响显著。随着温度的升高,还原度随之升高,反应速率加快;延长恒温时间也可以提高还原度,但恒温阶段反应速率增加缓慢     

Reduction Behaviour of Olivine Iron Ore Pellets in the Experimental Blast Furnace

An experimental study was conducted to determine the reduction behaviour of olivine iron ore pellets and associated reduction mechanisms in the experimental blast furnace (EBF) located at Luleå. Two sets of EBF samples, namely slowly annealed excavated samples and rapidly quenched probe samples of olivine bearing iron ore pellets were examined in detail. Pellet samples were analysed using SEM, XRD and SIROQUANT analysis to quantitatively determine iron ore phase transformations during descent in the EBF. In the tested EBF campaign, up to 75% of reduction occurred at less than 1100°C, i.e. before the pellet reached the cohesive zone while rest of 25% reduction was completed when pellets reached a temperature of 1300°C and hence within the cohesive zone. The reduction degree of pellets was found to have a linear correlation with distance from the stock line of the EBF. This study showed that the presence of olivine did not have a significant effect on reduction degree for temperatures less than 1100°C in the upper zone of the EBF. However, olivine increased the reduction rate in the final stage of reduction for temperatures in excess of 1100°C in the cohesive zone, which was attributed to the formation of an increased amount of molten FeO containing slag within the pellet. This study is expected to make important contributions towards further improvements in the pellet design as well as the optimization of blast furnace operation and efficiency.     

Study on Direct Reduction Characteristics of Iron Ore Coal Mixed Pellets

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直接还原铁生产工艺的选择

论述了直接还原铁生产工艺的发展,介绍了目前世界直接还原铁生产工艺的现状、特点.指出,钢铁联合企业的可持续发展需要直接还原铁,高炉、直接还原炉、焦炉联合流程是其生产直接还原铁的最佳工艺选择.