Behaviors of vanadium and chromium in coal-based direct reduction of high-chromium vanadium-bearing titanomagnetite concentrates followed by magnetic separation

The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.

Vanadium extraction from vanadium-bearing titanomagnetite by selective chlorination using chloride wastes (FeClx)

Vanadium extraction of vanadium-bearing titanomagnetite was investigated by selective chlorination. Thermodynamics analyses on the interactive reactions among related species in the system were made before the experiments. Some fundamental experiments for extracting vanadium by FeClx as chlorinating agent were conducted over the temperature range of 900-1300 K under air or oxygen atmosphere. The results show that vanadium can be extracted by the selective chlorination, using FeClx, based on thermodynamic analysis and experiment. Vanadium extraction ratio first increases with the increase of temperature, and then decreases with the increase of temperature over the range of 900-1300 K under air or oxygen atmosphere. The higher molar ratio of FeCI3 to oxides （nchl：noxd） reacting with FeC13, the higher ratio of vanadium extraction. Under oxygen atmosphere, the vanadium extraction ratio is up to 32% at 1100 K for 2 h by using FeCI3 as chlorinating agent.

Effect of Cr_2O_3 addition on the oxidation induration mechanism of Hongge vanadium titanomagnetite pellets

As part of a research project to develop a novel clean smelting process for the comprehensive utilization of Hongge vanadium titanomagnetite（HVTM）, in this study, the effect of Cr2O3 addition on the oxidation induration mechanism of HVTM pellets（HVTMPs） was investigated in detail. The results showed that the compressive strength of the HVTMPs was greatly weakened by the Cr2O3 addition, mainly because of a substantial increase in the porosity of the HVTMPs. The Cr2O3 addition marginally affected the phase composition but greatly affected the microstructural changes of the HVTMPs. Increased amounts of Cr2O3 resulted in a decrease in the uniform distribution of the hematite grains and in an increase in the Fe–Cr solid solutions（Fe1.2Cr0.8O3 and Fe0.7Cr1.3O3） embedded in the hematite grains. Moreover, the compact hematite was destroyed by forming a dispersed structure and the hematite recrystallization was hindered during the oxidation induration, which adversely affected the compressive strength. On the basis of these results, a schematic was formulated to describe the oxidation induration mechanism with different amounts of added Cr2O3. This study provides theoretical and technical foundations for the effective production of HVTMPs and a reference for chromium-bearing minerals.

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

Hongge vanadium titanomagnetite（HVTM）pellets were reduced by H2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ（H2）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 H2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050℃,ratio ofφ（H2）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.

Development of Intensified Technologies of Vanadium-Bearing Titanomagnetite Smelting

It was very difficult for the smelting of vanadium-bearing titanomagnetite by blast furnace because the content of TiO2 of blast furnace slag could amount to 20%-25%.After long term development and continuous improvement,special intensified smelting technologies for vanadium-bearing titanomagnetite by blast furnace were obtained and improved gradually.With the improvement of beneficiated material level and equipment level,smelting intensity has been increased gradually and the highest comprehensive smelting intensity reached 1.45 t/（m3·d）.Technical-economic indexes of blast furnace have also been increased remarkably.The highest utilization coefficient exceeded 2.7 t/（m3·d）on the condition that the burden grade was only about 50%.

Influences of Technological Parameters on Smelting-separation Process for Metallized Pellets of Vanadium-bearing Titanomagnetite Concentrates

The smelting-separation process for metallized pellets of vanadium-bearing titanomagnetite concentrates was studied.The influences of smelting temperature,smelting time,and the basicity of the metallized pellet on vanadium and iron recovery were investigated.The characteristics of titanium slag were analyzed using X-ray diffraction,energy dispersive spectroscopy,and mineralographic microscopic analysis.The results demonstrate that appropriate increases in smelting temperature and smelting time can improve the vanadium and iron recovery from metallized pellets and are beneficial for the slag-iron separation.Although increasing the basicity of the metallized pellet can considerably improve the vanadium and iron recovery,the TiO;grade of titanium slag was decreased.Under the optimal conditions,90.17% of vanadium and 92.98% of iron in the metallized pellet were recovered,and the TiO;grade of titanium slag was 55.01%.It was found that anosovite,augite,spinel,glassiness,and metallic iron were the main mineral phases of the titanium slag.

Influence of phosphorus on iron-based friction material prepared directly vanadium-bearing titanomagnetite concentrates

In situ selective carbothermic reactions and vacuum sintering were used to prepare iron-based friction material directly vanadium-bearing titanomagnetite concentrates.Effects of phosphorus addition(0.05–0.20 wt.%)on the microstructure and properties of iron-based friction material were investigated.The results show that the addition of phosphorus improves the microstructure and properties of the material significantly.When phosphorus addition increases to 0.15 wt.%,the sintering densification is promoted and the number of lamellar pearlites increases.Therefore,the relative density,hardness and tribological properties of the material are greatly enhanced.Particularly,the friction coefficient decreases 0.58 to 0.43,and the wear rate reduces 1.829×10^(–7) to 0.694×10^(–7)cm^(3)J^(-1).The dominant wear mechanism of the material changes severe abrasive wear to mild oxidation wear accordingly.However,when phosphorus addition exceeds 0.15 wt.%,the matrix continuity and tribological properties of the material are deteriorated.Comprehensively,the optimal addition of phosphorus in the iron-based friction material is 0.15 wt.%.

Softening–melting–dripping characteristics and evolution mechanism of vanadium-bearing titanomagnetite carbon composite briquette used as novel blast furnace burden

Vanadium-bearing titanomagnetite carbon composite briquette(VTM-CCB)was proposed as an innovative and promising blast furnace burden to realize low-carbon and high-efficiency ironmaking.To optimize the compositions of VTM-CCB based on its softening–melting–dripping characteristics,the evolution behavior and mechanisms of VTM-CCB in cohesive zone and dripping zone were investigated by conducting softening–melting tests under blast furnace conditions.The results show that the structure evolution of VTM-CCB in softening–melting process is correlated to the molten slag,metallic iron,liquid iron,and residual carbon.With the molar ratio of the fixed carbon to the reducible oxygen in iron oxides(FC/O ratio)ranging from 0.8 to 1.0,the VTM-CCB tends to form dense structure and accelerate the softening and melting.With increasing the FC/O ratio to 1.2 and 1.4,the VTM-CCB tends to form concentric circular structure,which could suppress the collapse of packed bed,shift down the location of core cohesive zone,and improve the gas permeability.Although the appropriate increase in FC/O ratio could improve the softening–melting performance of VTM-CCB,a higher FC/O ratio could also promote the precipitation of Ti(C,N),thereby thickening the molten mixtures and deteriorating the dripping behavior.Fully considering the softening–melting–dripping characteristics and permeability,the appropriate FC/O ratio of VTM-CCB should be controlled in the range of 1.0–1.2.

基于突变理论的红格钒钛磁铁矿区矿山地质环境评价

利用高分一号遥感影像与实地调查数据,结合地理、地质和气象等数据,采用突变理论综合评价方法建立了矿山地质环境评价指标体系,并将其应用于研究区内红格铁矿、马鞍山铁矿、潘家田铁矿、百草铁矿、小黑箐铁矿、阳雀箐铁矿和秀水河铁矿等7个典型矿山的地质环境评价中。结果表明,应用该方法的评价结果和矿山的实地调查结果吻合,与应用较广泛的模糊数学综合评价结果一致。与其它评价方法相比,突变理论综合评价法人为干预较少、不用确定指标权重、计算简单且可以适用于大范围的矿山地质环境评价,为矿山地质环境综合评价提供了新方法。

红格钒钛磁铁矿氧化物相转变及非等温氧化动力学

在对红格钒钛磁铁矿基础特性研究基础上,探讨了其球团氧化过程物相的存在形式和转变过程,并通过热分析法研究了红格矿非等温氧化动力学.结果表明:红格钒钛磁铁矿属于高铬型钒钛磁铁矿,Cr_2O_3的质量分数为1.48%,连晶强度为625 N;主要物相组成为磁铁矿、钛磁铁矿、钒磁铁矿、铬铁矿;温度低于300℃时其氧化速率缓慢;球团氧化过程有价组元物相迁移变化历程为:Fe_3O_4→Fe_2O_3;Fe_2VO_4→(Cr_(0.15)V_(0.85))_2O_3;Fe_(2.75)Ti_(0.25)O_4→FeTiO_3→Fe_9TiO_(15);FeCr_2O_4→(Fe_(0.6)Cr_(0.4))_2O_4,Fe_(0.7)Cr_(1.3)O_3,(Cr_(0.15)V_(0.85))_2O_3.红格矿非等温氧化动力学研究表明:当升温速率为10℃/min时,温度在220~380℃,380~500℃和500~800℃时,反应活化能分别为47.02,14.95和30.36 kJ·mol^(-1).

Effects of MgO/Al2O3 ratio on viscous behaviors and structures of MgO-Al2O3-TiO2-CaO-SiO2 slag systems with high TiO2 content and low CaO/SiO2 ratio

The effects of MgO/Al2 O3 ratio on the viscous behaviors of MgO-Al2 O3-TiO2-CaO-SiO2 systems were investigated by the rotating cylinder method.Raman spectroscopy was used to analyze the structural characteristics of slag and Factsage 7.0 was adopted to demonstrate the liquidus temperature of slag.The results show that the viscosity and activation energy for viscous flow decrease when the MgO/Al2O3 ratio increases from 0.82 to 1.36.The break point temperature and liquidus temperature of slag initially decrease and subsequently increase.The complex viscous structures are gradually depolymerized to simple structural units.In conclusion,with the increase of MgO/Al2O3 ratio,the degree of polymerization of slag decreases,which improves the fluidity of slag.The variations of liquidus temperature of slag lead to the same changes of break point temperature.

四川盐边县红格钒钛磁铁矿矿石矿物及化学成分分布特征

红格矿区是我国目前最大的钒钛磁铁矿资源基地,其矿产资源储量丰富,伴生钒、钪、镓、铬、钴、镍、铜、硫等有用元素,具有较高的经济价值。通过系统分析矿区有益元素的赋存状态及分布规律表明:矿石中各种元素的相对含量以及含量的波动幅度,与矿石TFe、岩性和岩石组合高度相关。

四川攀西红格钒钛磁铁矿床地质特征及找矿预测地质模型

红格铁矿位于四川攀西地区钒钛磁铁矿整装勘查区,地处川西南山地南部龙帚山脉南端大黑山西侧斜坡地带。红格矿区沿边、延深找矿取得重大突破,一跃成为全世界最大的钒钛磁铁矿区。基于红格矿区的最新找矿勘探成果,在总结矿床地质特征的基础上,对地层、构造、岩浆岩等成矿地质条件及基性—超基性岩的岩浆演化及成矿机制进行分析,构建红格矿床的找矿预测地质模型。

攀枝花红格钒钛磁铁矿区深部及外围找矿方法分析

红格矿区是我国目前最大的钒钛磁铁矿资源基地,红格基性—超基性含矿岩体主要受区域的三级控岩构造控制。由于大黑山玄武岩浆的喷溢及正长岩体、花岗岩体的破坏,以及后期构造运动的影响,使该区第三级控岩构造转化为以南北向的挤压构造为主。并把原来可能系一个完整大岩体分割成了现在的大小不等、岩相带不全、剥蚀程度不同的十余个岩体(块)组成的岩体(块)群。研究红格岩盆分布特征拓展找矿空间取得外围找矿突破;利用“攀西杂岩层状韵律旋回模式”就矿找矿、预测深部矿体,探边摸底;最后以地磁异常加深部钻孔验证定位深部矿体,是红格矿区深部及外围勘查取得重大进展的有效找矿方法组合。

红格钒钛磁铁矿中铁、铬的赋存状态研究

通过化学多元素分析、物相分析、X射线衍射分析、光学显微镜和MLA等多种现代测试手段对攀枝花红格高铬型钒钛磁铁矿的化学组成、矿物种类及含量、含铬矿物的能谱微区成分分析-平衡概算-产出形式、钛磁铁矿的粒度及解离度等方面进行详细研究,查清了铬的分布状态及其富集趋势和铁精矿的理论指标,综合分析了磨矿细度及其对应铁精矿的理想指标,明确了影响选矿效果的主要矿物学因素,为综合开发利用红格钒钛磁铁矿提供了详细的科学依据。