Thermodynamic studies on gas-based reduction of vanadium titano-magnetite pellets

Numerous studies have focused on the reduction thermodynamics of ordinary iron ore;by contrast, the literature contains few thermodynamic studies on the gas-based reduction of vanadium titano-magnetite (VTM) in mixed atmospheres of H2, CO, H2O, CO2, and N2. In this paper, thermodynamic studies on the reduction of oxidized VTM pellets were systematically conducted in an atmosphere of a C–H–O system as a reducing agent. The results indicate that VTM of an equivalent valence state is more difficult to reduce than ordinary iron ore. A reduction equilibrium diagram using the C–H–O system as a reducing agent was obtained;it clearly describes the reduction process. Experiments were performed to investigate the effects of the reduction temperature, the gas composition, and two types of iron ores on the reduction of oxidized VTM pellets. The results show that the final reduction degree increases with increasing reduction temperature, increasing molar ratio of H2/(H2 + CO), and decreasing H2O, CO2, and N2 contents. In addition, the reduction processes under various conditions are discussed. All of the results of the reduction experiments are consistent with those of theoretical thermodynamic analysis. This study is expected to provide valuable thermodynamic theory on the industrial applications of VTM.

Influence of microwave treatment on grinding and dissociation characteristics of vanadium titano-magnetite

The effect of microwave treatment on the grinding and dissociation characteristics of vanadium titano-magnetite(VTM) ore were investigated using scanning electron microscopy(SEM), nitrogen absorption measurements, particle size distribution measurements, X-ray diffraction(XRD) analysis, Fourier transform infrared(FT-IR) spectroscopic analysis, and magnetic separation. SEM analysis showed that microfractures appeared in the microwave-treated VTM, which is attributed to the microwaves' selective heating characteristic and the differential expansion between minerals and gangues. Nitrogen absorption showed that the microfractures were more pronounced when the microwave heating time was increased. Particle size distribution analysis showed that microwave treatment could improve the grindability of the VTM, thus increasing the weight percent of the fine-ground product. The increase in grindability was more significant with prolonged heating time. Moreover, the particle size distribution of the fine-ground product changed only slightly after the microwave treatment. XRD analysis showed that the crystallinity of the microwave-treated VTM increased with increasing microwave heating time. The magnetic separation tests revealed that the separation efficiency increased as a result of the intergranular fractures generated by microwave treatment. The Fe grade of the magnetic fraction of microwave-treated VTM was 1.72% higher than that of the raw ore. We concluded that the microwave treatment was beneficial, especially for the mineral processing characteristics.

Influence and mechanism of Indonesia vanadium titano-magnetite on metallurgical properties of iron ore sinter

In order to provide a reliable reference for utilizing Indonesia vanadium titano-magnetite(VTM) in blast furnace(BF) economically, metallurgical properties of iron ore sinter with addition of Indonesia VTM in mixed sintering materials were investigated, including low-temperature reduction degradation index(RDI), reducibility index(RI), and softening/melting properties. Additionally, influenced mechanism of Indonesia VTM on metallurgical properties of sinter was studied. It is found that adding Indonesia VTM in sintering process quickly increases the RDI of sinters, and decreases the RI from 78.02% to 68.43%. Moreover, both beginning temperature(T_4) and final temperature(TD) of softening/melting increase gradually, and cohesive zone temperature range(T_D–T_4) enlarges from 219 oC to 315 oC. As a result, the permeability of cohesive zone gets worse, which is proven by the higher maximum pressure drop(δPmax) in softening/melting experiments. It is concluded that, after comprehensively considering all metallurgical properties mentioned above, the proper proportion of Indonesia VTM in sintering process is proposed in the new raw materials conditions.

Reduction Kinetics of Vanadium Titano-Magnetite Carbon Composite Pellets Adding Catalysts Under High Temperature

Experiments were carried out by adding CaF2 and NaF as catalysts in an Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from 1 473 to 1 673 K. The scanning electron microscope （SEM） was used to characterize the microstructure of product. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39 kJ/mol without adding any catalysts. Adding CaF2 or NaF of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95 and 15.79 kJ/mol, respectively. In addition, temperature was an important factor influencing on reaction rate.

Influence of Coating MgO on Sticking and Functional Mechanism during Fluidized Bed Reduction of Vanadium Titano-magnetite

The vanadium titano-magnetite （VTM） iron ore fines of 110--150/xm in diameter were reduced in a trans- parent quartz fluidized bed by 70 %CO-30 % H2 （volume fraction） mixtures. MgO powders served as coating agent to solve sticking problem. Two coating methods were introduced in this experiment： high temperature injection method and briquetting→oxidizing roast→crushing method. According to the experimental results, the minimum effective coating amount of MgO was 0. 1 mass%. The metallization ratio （MR） of the product rose from around 58% to above 90% with the above treatments. To investigate the sticking mechanism of fine ore, the morphology evolution was in- vestigated. Instead of iron whiskers, an interlaced fibrous porous surface formed. The ulvospinel （2FeO ： TiO2 ） in VTM is more difficult to be reduced than FeO according to thermodynamic calculation. XRD results showed that MgO diffused into Fe203 lattice before forming pleonaste （MgO · Fe2O3 ） during oxidizing roast at 1273 K. The melting point of the pleonaste is 1986 K and that made contribution to prevent the sticking problem.

微波消解-电感耦合等离子体原子发射光谱法测定钒钛磁铁矿中锆铌钒铬

提出微波消解与电感耦合等离子体原子发射光谱法测定相结合的方法测定了钒钛磁铁矿中锆、铌、钒和铬.方法以HF与HNO3为消解试剂,用高压密闭微波消解技术消解样品,因此钒钛磁铁矿中基体以及共存杂质氧化锆、氧化铌、氧化铬等难以被酸消解的组分可得到很好的溶解.在氢氟酸介质中测定避免了高浓度钛基体和铌、锆等待测元素在低酸度介质中容易水解所导致的影响.通过筛选待测元素分析谱线以及综合运用基体匹配与同步背景校正法消除了光谱干扰和基体效应的影响.背景等效浓度值从0.000 2％（Cr）至0.000 8％（Nb）,测定下限为0.001 7％（Ⅴ）～0.002 9％（Nb）.方法用于钒钛磁铁矿中锆、铌、钒和铬的测定,测定结果与火焰原子吸收光谱法及电感耦合等离子体质谱法相符,相对标准偏差（n=8）均不大于4.7％.

钒钛磁铁矿弱磁富集-酸浸提钒研究

针对陕西某地钒钛磁铁矿,进行了弱磁富集-酸浸提钒研究。结果表明:原矿经磁场强度为50 kA/m弱磁分选后,磁铁矿得到富集,V_2O_5品位从0.24%提高至1.09%。磁选精矿在硫酸浓度5 mol/L、反应温度100℃、反应时间60 min和液固比5∶1的条件下浸出,钒浸出率可达80.45%。

钒钛磁铁矿金属化还原-选分-电热熔分新工艺

针对攀枝花钒钛磁铁矿进行了金属化还原-选分-电热炉熔分实验,考察了磁场强度、还原温度、还原时间、配碳比、还原煤粒度对金属化还原及磁选分离效果的影响.实验结果表明,当磁场强度50 mT、还原温度1 350℃、还原时间60 min、配碳比1.0、还原煤粒度为-75μm时,金属化还原后产物及磁选分离磁性物质、非磁性物质的各项指标最佳,进一步进行电热炉熔分可实现铁钒分离.新工艺达到铁钒钛资源高效分离要求,铁钒钛收得率分别为95.07%,71.60%和80.08%.

Formation of Hearth Sediment during Vanadium Titano-magnetite Smelting in Blast Furnace No.7 of Chengde Iron and Steel Company

The large quantity of sediment produced in the hearth during vanadium titano-magnetite smelting in a blast furnace（BF） affects the stability of the blast furnace operation. Testing and analysis of the sediment in the hearth of Chengde Iron and Steel Company？s BF No.7 revealed that it was mainly concentrated in the location below the tuyere and above the iron notch. Notably, some of the bonding material（sediment） consisted of greater than 50% pig iron, and the pig iron distributed in the slag was granular. It is proposed that a large quantity of Ti C and Ti（C,N） are deposited on the surface of the pig iron. These high melting point materials mix with iron drops, preventing the slag from flowing freely, thus leading to the formation of bonding materials. In addition, the viscosity and melting temperature of the slag in the tuyere areas fluctuate greatly, and thus the properties of the slag are unstable. Moreover, the slag contains large quantities of carbon, which results in the reduction of Ti O2. The resultant precipitation of Ti is followed by the formation of Ti C in the slag, which also leads to an increase in the viscosity of the slag and difficulty in achieving separation of the slag-iron. In fact, all of these factors interact with each other, and as a result, sediment is formed when the operating conditions in the hearth fluctuate.

ICP-AES法测定钒钛磁铁矿中钒、钛元素的研究

通过实验研究了电感耦合等离子体原子发射光谱法(ICP-AES法)测定钒钛磁铁矿中元素钒、钛的分析测试条件。采用密闭式高压消解罐溶解试样,选用元素最佳分析谱线和仪器合适的工作条件进行测定,共存元素之间的干扰很小,测定值相对标准偏差小于2%,加标回收率在95%～105%之间,分析方法快速、简便,分析结果准确。

1-(2-吡啶偶氮)-2-萘酚光度法测定钒钛磁铁矿中痕量镓

利用1-（2-吡啶偶氮）-2-萘酚（PAN）与镓反应生成红色络合物的特性,建立了光度法测定钒钛磁铁矿中镓的方法。实验表明：于25mL比色管中,依次加入2.0mL KHP-HCl缓冲溶液（pH 3.2）、4.0mL 0.5g/L PAN溶液、3.0mL 95%乙醇,用水定容后反应10min,用1cm比色皿,于545nm处采用分光光度法进行测定,镓（Ⅲ）的质量浓度在0.05-3μg/mL范围内符合比尔定律,方法检出限为0.033μg/mL,表观摩尔吸收系数ε=3.0×10^4 L·mol^-1·cm^-1。将GBW 07226a钒钛磁铁矿精矿一号和GBW 07224钒钛磁铁矿原矿一号样品经氢氧化钠和过氧化钠碱熔、水浸取、过滤、酸化还原铁等步骤后,采用乙酸丁酯萃取、水反萃取,使镓与大量基体元素分离,再采用方法对样品中痕量镓进行测定,结果与认定值一致,相对标准偏差（RSD,n=3）小于15%。

钻孔岩心红外光谱-便携式XRF-磁化率测试在攀西太和钒钛磁铁矿床勘查中的应用

近年来,红外光谱技术因其可以绿色、快速、无损、精确探测矿物和提高勘查效率而备受关注。攀西超大型太和钒钛磁铁矿床位于镁铁质-超镁铁质层状岩体中,该矿床的典型矿物的红外光谱特征研究相对缺乏,制约了勘查效率的提高。本文应用便携式傅里叶变换红外光谱仪对四川太和钒钛磁铁矿床钻孔ZK1307岩心开展热红外光谱测试工作,并辅以便携式X射线荧光光谱(XRF)元素含量分析和磁化率值的综合分析,参考岩心编录情况,分析研究了钻孔岩性-矿物组合-元素含量-磁化率之间的对应关系。研究表明:热红外光谱可以实现快速、无损对辉石特征吸收峰的信息提取,识别含磁铁辉石岩体分布范围,快速界定含矿岩体;太合矿床Fe、Ti、V元素含量可以用磁化率值进行线性拟合,较高的Fe、Ti、V金属元素含量和磁化率值可作为判断地质体矿化的指示信息。

电感耦合等离子体发射光谱法同时测定钒钛磁铁矿中钒钛钴镍

钒钛磁铁矿样品经过氧化钠熔融,盐酸提取,溶液分取稀释后用电感耦合等离子体发射光谱法同时测定其中的V2O5、TiO2、Co、Ni。实验确定过氧化钠的用量为1.5 g,盐酸的用量为10 mL,选择干扰元素较少和背景干扰较小的V、Ti、Co、Ni分析谱线分别为292.4 nm、334.9 nm、230.7 nm、231.6 nm,在稀释因子为10(总稀释因子5000)的条件下进行分析,方法检出限为0.05～0.17μg/g。用国家一级钒钛磁铁矿标准物质GBW 07225(原矿)、钒钛磁铁矿标准物质GBW 07226a(精矿)、钒钛磁铁矿标准物质GBW 07227(尾矿)验证方法精密度和准确度,方法精密度(RSD,n=12)为0.41%～1.91%;除含量较低的Ni和Co外,相对误差(RE,n=4)均小于5%。通过安装氩气加湿器有效地解决了盐分较大带来的影响,在标准系列中加入等量空白溶液,保持基体与试样一致,消除了基体效应。方法分解样品彻底完全,分析流程简单,易于掌握,一次熔样可以同时测定多种元素,可适用于大批量样品分析。

钒钛磁铁矿冷压含碳球团的粘结剂选择

为了提高钒钛磁铁矿冷压含碳球团的强度,选用膨润土、糖浆及玉米面作粘结剂,对比了3种粘结剂对球团性能的影响,从而确定适合转底炉工艺的较优粘结剂及最佳配加量。结果表明:膨润土加入量超过6%时,制备球团性能能够达到转底炉工艺要求,但导致球团内铁品位降低程度较大;添加糖浆作粘结剂时,在实验研究范围内,球团性能尚未达到工艺要求,且存在压球过程中脱模困难问题;而选用玉米面作粘结剂制备球团时各方面都能达到工艺要求。玉米面(含量2.5%)加入到浓度为4%的NaOH溶液中发酵15 min左右,所得球团的湿球落下强度为4.8次,湿球抗压强度为55.1 N,干球落下强度为24.8次,干球抗压强度为648.1N,湿球爆裂温度为400℃,满足转底炉生产的各项指标。

电感耦合等离子体质谱法测定钒钛磁铁矿中铬钴镍铜镓

建立了应用电感耦合等离子体质谱法(ICP-MS)测定钒钛磁铁矿中Cr、Co、Ni、Cu和Ga元素含量的分析方法。对溶样体系进行了试验,确定采用HCl+HNO3+HF+HClO4溶解酸体系发烟溶解试样。在最佳的仪器工作参数条件下,考察了测定中潜在的质谱干扰及干扰程度,选择52Cr、60 Ni、59Co、63Cu和71 Ga为测量同位素。研究了基体效应及内标元素对测定的校正作用,结果表明,内标元素Sc的使用能有效的提高测量精密度,降低基体效应引起的信号强度漂移。方法的检出限为0.08～2.34ng/mL。方法应用于钒钛磁铁矿有证参考物质GBW07224、GBW07227和BH0103中铬钴镍铜镓的分析,测定值与认定值符合较好,相对标准偏差(n=6)不大于6.8%。

钒钛铁精矿配比对钒钛烧结矿冶金性能的影响

就提高钒钛铁精矿配比对攀钢钒钛烧结矿冶金性能的影响进行了研究。结果表明:钒钛铁精矿配比从46%提高到52%,钒钛烧结矿的FeO含量升高,低温还原粉化率降低,中温还原度降低,软化开始、压差陡升和滴落温度均升高,最大压差升高。本结果可为钒钛铁精矿烧结合理配矿提供指导。

电感耦合等离子体原子发射光谱法测定钒钛磁铁矿中氧化锰、磷、铜、五氧化二钒、二氧化钛、氧化钙和氧化镁

研究了电感耦合等离子体原子发射光谱法(ICP-AES)同时测定钒钛磁铁矿中MnO、P、Cu、V2O5、TiO2、CaO、MgO的条件并建立了测定方法。采用HCl、HNO3、HF、HClO4溶解钒钛磁铁矿试样,通过采用基体匹配法消除基体效应,选择合适的光谱线作为分析线并采用谱线背景扣除法消除谱线干扰。实验结果表明钒钛磁铁矿中的MnO、P、Cu、V2O5、TiO2、CaO、MgO在一定浓度范围内与强度具有良好的线性关系,相关系数在0.999以上。将本方法用于测定标准样品GBW07226,测得结果与认定值相符,相对标准偏差(RSD)为0.56%(Cu)～10.6%(P),加标回收率在95%～107%之间。

某低品位钒钛磁铁矿选矿试验研究

某钒钛磁铁矿含TFe16.43%、TiO_2 4.70%,属表外矿。矿石组成复杂,金属矿物主要为钛铁矿、钛磁铁矿,脉石矿物主要为辉石、斜长石、角闪石和橄榄石。针对矿石性质,采用预分选-阶段磨选流程选钛,获得了TFe品位57.58%,TFe回收率60.42%的铁精矿产品;选铁尾矿采用强磁-浮选流程选钛,获得了TiO_2 品位46.23%,浮选作业回收率71.24%的钛精矿产品,实现了原矿中铁、钛的较好回收。

红格钒钛磁铁矿选铁尾矿工艺矿物学特征

通过多元素分析分析法、光学显微镜、扫描电镜、x射线粉体衍射仪、x射线荧光光谱分析等手段，对四川攀枝花红格钒钛磁铁矿选铁尾矿的矿物学特征进行了详细研究。结果表明，选铁尾矿由Fe、Ti、V、cr、cu、Ni、Mn、Ca、Mg、Si、A1、S等元素构成；选铁尾矿中的矿物主要是由金属矿物钛铁矿和普通辉石、斜长石等脉石矿物组成。选铁尾矿中主要矿物的矿物学特征与原矿中相同矿物的矿物学特征相似。选铁尾矿中的钛铁矿经过碎、磨、选后，晶体形态发生了变化，但内部结构变化并不大。选铁尾矿中的钛铁矿以粒径细小的粒状颗粒为主，粒级主要集中在0．074—0．053mm区间内。选铁尾矿中的Fe随着粒度的减小先减少后增加，Ti则随着粒度的减小而增加。该研究结果为该矿区选铁尾矿的选冶工艺以及综合利用提供了重要参考依据。

工艺参数对低钛型钒钛磁铁精粉烧结制粒的影响

研究了工艺参数对低钛型钒钛磁铁精粉烧结制粒行为的影响。研究结果表明:低钛型钒钛磁铁精粉的颗粒长大指数和均匀性指数随着制粒时间的延长而增大,当制粒时间超过5 min后,颗粒长大指数和均匀性指数的增幅降低,基本维持在一个稳定水平,准颗粒小球的强度和热稳定性随着制粒时间的延长先升高后降低;颗粒长大指数和均匀性指数随着圆筒转速的增大先升高后降低,而破损指数随着圆筒转速的升高先降低后升高,制粒小球的抗热粉化性能与圆筒的转速没有明显关系;颗粒长大指数、均匀性指数和热粉化指数随着填充率的升高先升高后降低,而破损指数随着填充率的增大先降低后升高;综合分析制粒时间、转速和填充率对低钛型钒钛磁铁精粉制粒的影响,混合料二混制粒时间应控制在5 min,圆筒转速应控制在22 rpm,填充率应控制在13%左右。