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.

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.%.

Effect of reductant type on the embedding direct reduction of beach titanomagnetite concentrate

Iron and titanium were recovered from beach titanomagnetite(TTM) concentrate by embedding direct reduction and magnetic separation. The reduction products and the effects of the reductant type and reduction temperature on the reduction behavior were investigated. The results showed that the reduction of TTM concentrate was strongly related to the gasification reactivity of the reductant. Bitumite presented a better product index than wheat-straw biochar and coke, mainly because the gasification reactivity of bitumite was better than that of the other reductants. In addition, high temperatures were not beneficial to embedding direct reduction because of the emergence of a molten phase and iron-joined crystals, which in turn reduced the diffusion rate of the reducing gas and impeded the reduction reaction in the central area of the roasted briquette. The use of bitumite as the reductant at a C/Fe molar ratio of 1.4 and a reduction temperature of 1200°C for 120 min resulted in direct-reduction iron powder assaying 90.28 wt% TFe and 0.91 wt% TiO_2 with an iron recovery of 91.83% and titanium concentrate assaying 46.01 wt% TiO_2 with a TiO_2 recovery of 91.19%. Titanium existed mainly in the form of anosovite and ilmenite in the titanium concentrate.

Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate

Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate(VTC) were investigated. It was found that calcium compounds had great effects on the metallization rate of the reduction product, the order of the metallization rate of reduction product being CaCO3 > no additive > CaSO4 > CaCl2, which indicated that the addition of CaCO3 was more conducive to promoting the reduction of iron than other calcium compounds. Gas analysis showed that there were mainly two processes in the carbothermic reduction of VTC, a solid–solid and a solid–gas reaction. The concentrations of CO and CO2 were highest when CaCO3 was added, while that in a roasting system decreased the most when CaCl2 was added. X-ray diffraction(XRD) analysis showed that calcium compounds could change the reduction process of ilmenite in VTC. The phase compositions of the reduction products were changed from metallic iron(Fe) and anosovite(FeTi2O5) to metallic iron(Fe) and perovekite(CaTiO3) when calcium compounds were added. Additionally, CaSO4 and CaCl2 could significantly promote the growth of metallic iron particles, though the existence of Fe-bearing Mg2TiO4 in reduction products was not conducive to the reduction of iron. The formation of FeS would further hinder the reduction of iron after adding CaSO4.

Formation of calcium titanate in the carbothermic reduction of vanadium titanomagnetite concentrate by adding CaCO3

The formation of calcium titanate in the carbothermic reduction of vanadium titanomagnetite concentrate(VTC)by adding CaCO3 was investigated.Thermodynamic analysis was employed to show the feasibility of calcium titanate formation by the reaction of ilmenite and Ca CO3 in a reductive atmosphere,where ilmenite is more easily reduced by CO or carbon in the presence of CaCO3.The effects of CaCO3 dosage and reduction temperature on the phase transformation and metallization degree were also investigated in an actual roasting test.Appropriate increase of CaCO3 dosages and reduction temperatures were found to be conducive to the formation of calcium titanate,and the optimum conditions were a CaCO3 dosage of 18 wt%and a reduction temperature of 1400°C.Additionally,scanning electron microscopy–energy dispersive spectrometry(SEM–EDS)analysis shows that calcium titanate produced via the carbothermic reduction of VTC by CaCO3 addition was of higher purity with particle size approximately 50μm.Hence,the separation of calcium titanate and metallic iron will be the focus in the future study.

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.

Oxidation behavior of low-grade vanadiferous titanomagnetite concentrate with high titanium

In order to clarify the oxidation mechanisms and make better use of the low-grade vanadiferous titanomagnetite concentrate with high titanium(LVTC),the oxidation behavior of LVTC was investigated.The results showed that oxidation degree was achieved within 90 min when temperature was not lower than 700°C,and the main phases of the oxidized LVTC consisted of Fe9TiO15,Fe2O3,CaSiTiO5 and a small amount of Fe2.75Ti0.25O4.Increasing temperature is favorable to the formation of Fe2TiO5.The surface of LVTC gradually becomes rough,with fine particles of needle-like and granular shape appearing on the surface,which finally turn from laminar to creamy,spread out,and are interspersed with many tiny holes.The phase oxidation paths in LVTC were as follows:(1)Fe2.75Ti0.25O4→Fe9TiO15+Fe2O3;(2)Fe2.75Ti0.25O4→Fe2O3+FeTiO3→Fe2TiO5;(3)FeTiO3→Fe2O3+Fe2Ti3O9→Fe2TiO5.LVTC is predominantly mesoporous whether oxidized or not,with the pores mainly distributed in the range of 2–40 nm,and the specific surface area of LVTC decreases significantly with increasing temperature.

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%.

Effects of embedding direct reduction followed by magnetic separation on recovering titanium and iron of beach titanomagnetite concentrate

Embedding direct reduction followed by magnetic separation was conducted to fully recover iron and titanium separately from beach titanomagnetite （TTM）. The influences of reduction conditions, such as molar ratio of C to Fe, reduction time, and reduction temperature, were studied. The results showed that the TTM concentrate was reduced to iron and iron-titanium oxides, depending on the reduction time, and the reduction sequence at 1 200℃ was suggested as follows ： Fe2.75 Ti0.25O4→Fe2TiO4→FeTiO3→FeTi2O5. The reduction temperature played a considerable role in the reduction of TTM concentrates. Increasing temperature from 1 100 to 1 200℃ was beneficial to recovering titanium and iron, whereas the results deteriorated as temperature increased further. The results of X-ray diffraction and scanning electron microscopy analyses showed that low temperature （≤1100℃） was unfavorable for the gasification of reductant, resulting in insufficient reducing atmosphere in the reduction process. The molten phase was formed at high temperatures of 1250-1 300℃, which accelerated the migration rate of metallic particles and suppressed the diffusion of reduction gas, resulting in poor reduction. The optimum conditions for reducing TTM concentrate are as follows： molar ratio of C to Fe of 1.68, reduction time of 150 min, and reduction temperature of 1 200℃. Under these conditions, direct reduction iron powder, assaying 90.28 mass% TFe and 1.73 mass% TiO2 with iron recovery of 90.85%, and titanium concentrate, assaying 46.24 mass% TiO2 with TiO2 recovery of 91.15%, were obtained.

Recovery of titanium and vanadium from titanium–vanadium slag obtained by direct reduction of titanomagnetite concentrates

A process of NaOH molten salt roasting-water leaching to treat titanium-vanadium slag obtained by direct reduction of titanomagnetite concentrates was investigated.X-ray diffraction(XRD), scanning electron microscopy(SEM) equipped with energy dispersive spectroscopy(EDS), and thermogravimetry-differential scanning calorimetry(TG-DSC) techniques were used to characterize the samples. The results show that anosovite(Mg_(x)Ti_(3-x)O_(5))and clinopyroxene [Ca(Ti,MgAl)(SiAl)_(2)O_(6)] are the major phases of titanium-vanadium slag. In the NaOH molten salt roasting process, titanium is converted to intermediate product Na_(2)TiO_(3) and vanadium is converted to water-soluble vanadate. The response surface methodology(RSM) was used to optimize the roasting process conditions. NaOH to slag mass ratio(N/S) and roasting temperature are the main influential factors. Under the optimal roasting conditions,i.e., roasting temperature of 550℃, N/S of 1.20, and roasting time of 80 min, the conversions of titanium and vanadium are 96.5 % and 93.0 %, respectively. In the water leaching process, Na_(2)TiO_(3) is converted to amorphous structure of H_(2)TiO_(3) since Na^(+)is exchanged with H^(+). Up to 93.0 % vanadium is leached out under the optimal leaching conditions. Titanium and vanadium in the titanium-vanadium slag can be separated and then recovered.

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.

某选钛厂入库尾矿选矿工艺研究

为从某选钛厂尾矿中有效回收钛资源、提高原矿相对利用率,对TiO_(2)品位5.81%的选钛厂入库尾矿进行了选矿工艺研究,制定了重选-磁选工艺流程,并研究了磁选过程中磁场强度,重选过程中上升水流量、给矿速度、给矿浓度等对钛铁矿选别指标的影响。结果表明,经+38μm粒级重选,-38μm粒级分级底流重选、分级溢流磁选的重选-磁选联合工艺选别,能够获得TiO_(2)品位16.08%、回收率62.63%的粗精矿,抛出产率77.41%、TiO_(2)品位2.39%的尾矿,大大减少了后续浮选流程入矿量。

钛精矿制取富钛料新工艺

针对攀钢钛精矿采用回转窑直接还原技术 ,借助于添加剂的催化作用 ,使钛精矿中铁氧化物充分还原并能促使铁晶粒长大 ,实现了 Fe和 Ti在磨选过程中的高效分离 ,成功地开发了钛精矿制取富钛料的新工艺。扩大试验结果表明 ,在添加剂 KS用量 5 % ,粘结剂用量 1% ,球团经70 0℃预热 15 min后 ,在回转窑“火力模型”中还原 ,其适宜工艺参数为 :高温还原温度 110 0℃ ,高温还原时间≥ 2 10 min,C/ Fe为 2 .2左右 ,填充率 2 0 %左右 ,所得钛精矿金属化球团的金属化率 >92 % ,金属化球团经破碎、磨矿、磁选 ,得到磁性物 TFe>81% ,回收率 >86 % ;富钛料 Ti O2 >74 % ,回收率 >90 %。

某钒钛磁铁矿综合利用试验研究

本文在某高钛型钒钛磁铁矿(TFe40.74%,TiO226.11%,V2O50.29%)的工艺矿物学特征研究及磁选试验的基础上,进行了连续试验,获得了产率为67.80%,TFe、TiO2、V2O5品位分别为45.70%、31.75%、0.323%,TFe、TiO2、V2O5回收率分别为75.98%、84.80%、76.41%的铁(钒)精矿。该精矿产品经还原焙烧-磨矿分选后,可能获得TiO2品位85%的高钛渣和金属化率为90%的金属铁产品,能有效地综合利用该资源中的铁、钛。

攀枝花钛磁铁矿性质变化对铁精矿品位的影响

攀枝花地区钒钛磁铁矿成矿条件基本相同,岩浆晚期所产出的钛磁铁矿、粒状钛铁矿基本特征相似。但由于成矿地质条件的差异,矿浆物理、化学成份的变化,从而使不同矿区或相同矿区不同层位的钛磁铁矿的铁钛含量有一定的差异。攀枝花密地、白马、潘家田三选厂的原料来自攀枝花不同矿区。在基本相同的选矿工艺条件下,其铁精矿质量有一定差异。为查明原矿性质变化对选矿工艺指标的影响,对上述三选厂原矿、精矿、尾矿样品进行了工艺矿物学研究,证实了钒钛磁铁矿中钛磁铁矿性质的变化对铁精矿质量的影响。

提高钒钛磁铁精矿烧结产质量的研究

试验结果表明，热风烧结可以提高钒钛磁铁精矿烧结矿的成品率和转鼓强度，但利用系数降低；硼泥、氧化剂和ＭｅＯ对提高烧结矿的产质量有明显的效果，其中硼泥效果最佳。添加１％的硼泥，利用系数提高３％，转鼓强度提高２．４％，成品率提高４％

两种铁精粉在球团生产中的应用

针对球团精矿紧缺问题,为拓宽铁矿粉资源,降低原料成本,进行了球团配加菲律宾精粉、钒钛精粉的试验研究。通过造球性能、焙烧性能及冶金性能的测定,结果表明加入部分菲律宾精粉、钒钛精粉是可行的。

某低品位钒钛磁铁矿预分选试验研究

本文简述了某低品位钒钛磁铁矿(TFe20.49%,TiO210.31%)的工艺矿物学特性。通过条件试验,确定了预分选综合试验的工艺条件,并进行了连续验证试验,获得了产率为68.12%,TFe、TiO2品位分别为26.42%、13.62%,回收率分别为86.70%、89.62%的预分选精矿。

Windimurra钒钛磁铁矿综合回收试验研究

简述了Windimurra钒钛磁铁矿主要金属元素的赋存、主要矿物组成及矿物含量。磁选条件试验确定了该矿的试验磁场强度(磁选粗选、扫选磁场强度为280kA/m、350kA/m)和粒度(-0.5mm),并进行了一粗一扫一精、扫选精矿同精选尾矿合并后再磁选流程的闭路试验,最终获得了产率为41.93%,TFe、TiO2、V2O5品位分别为52.14%、18.52%、1.04%,TFe、TiO2、V2O5回收率分别为72.26%、83.30%、82.43%的钒(铁)精矿,对钛磁铁矿(包括钛磁赤铁矿、钛赤铁矿和钛磁铁矿)和钛铁矿矿物的回收率分别为84.32%、84.85%,能有效地回收该资源中的铁、钛、钒。