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.%.

盐酸与硫酸浸出预还原钒钛磁铁矿混合精矿中的Fe,V及Ti

以预还原处理后的钒钛磁铁矿混合精矿为原料,用盐酸浸出其中的铁、钒、钛,考察了各因素对铁、钒、钛浸出率的影响,并对浸出渣进行了物相分析.结果表明,在初始盐酸浓度20%(ω)、液固质量比4:1、浸出温度110℃、浸出时间4 h的优化浸出条件下,铁、钒的浸出率分别为91.8%和95.0%,钛的浸出率为0.3%;浸出过程中钛是先溶解-再水解沉淀;盐酸浸出液可用于回收铁和萃取提钒;盐酸浸出渣中Ti O2的硫酸分解率达98.2%,可作为硫酸法生产钛白的原料.