High-chromium vanadium-titanium magnetite all-pellet integrated burden optimization and softening-melting behavior based on flux pellets

High-chromium vanadium-titanium magnetite(HVTM)is a crucial polymetallic-associated resource to be developed.The allpellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future.By referencing the production data of vanadium-titanium magnetite blast furnaces,this study explored the softening-melting behavior of high-chromium vanadium-titanium magnetite and obtained the optimal integrated burden based on flux pellets.The results show that the burden with a composition of 70wt%flux pellets and 30wt%acid pellets exhibits the best softening-melting properties.In comparison to that of the single burden,the softening-melting characteristic temperature of this burden composition was higher.The melting interval first increased from 307 to 362℃and then decreased to 282℃.The maximum pressure drop(ΔPmax)decreased from 26.76 to 19.01 kPa.The permeability index(S)dropped from 4643.5 to 2446.8 kPa·℃.The softening-melting properties of the integrated burden were apparently improved.The acid pellets played a role in withstanding load during the softening process.The flux pellets in the integrated burden exhibited a higher slag melting point,which increased the melting temperature during the melting process.The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden.The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening-melting properties of the integrated burden.

Effect of basicity on sintering behavior of low-titanium vanadium-titanium magnetite

Basicity has an important effect on the sinter quality, especially for low-titanium vanadium-titanium sinter. The effect of basieity on sintering behavior of low-titanium vanadium-titanium mixture, and the transference and distribution of element in sintering process were researched by sinter pot test, mineralogical analysis, scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） analysis. The results show that CaO preferentially reacts with TiO2, generating pervoskite, so that the total liquid phase content of the sinter is low. There is an increase in the perovskite concentration of the sinter with the basicity ranging from 1.9：1 to 2.7：1. With increasing the basicity, the calcium ferrite content increases slightly and then rises rapidly, while the silicate content decreases and the metallurgical property of the sinter is improved. As for the distribution of these elements in the sinter, Ti occurs mainly in perovskite, V occurs mainly in silicate, and Fe occurs mainly in magnetite and hematite. The most abundant occurrence of Ca and Si occurs in silicate and perovskite. With increasing the basicity, the contents of A1 and Mg increase in calcium ferrite, while they decrease in other minerals.

Solid-state reduction kinetics and mechanism of pre-oxidized vanadium-titanium magnetite concentrate

The solid-state reduction kinetics of pre-oxidized vanadium-titanium magnetite concentrate was studied. The phase and microstructure of the reduction product were characterized by XRD, SEM and EDS methods, based on which the mechanism of the solid-state reduction was investigated. The results showed that using coal as reductant at 950-1100 °C, the solid-state reduction of the pre-oxidized vanadium-titanium magnetite concentrate was controlled by interface chemical reaction and the apparent activation energy was 67.719 k J/mol. The mineral phase transformation during the reduction process can be described as follows： pre-oxidized vanadium-titanium magnetite concentrate → ulvospinel → ilmenite → Fe Ti2O5 →（FenTi1-n）Ti2O5. M3O5-type（M can be Fe, Ti, Mg, Mn, etc） solid solutions would be formed during the reduction process of the pre-oxidized vanadium-titanium magnetite concentrate at 1050 °C for 60 min. The poor reducibility of iron in M3O5 solid solutions is the main reason to limit the reduction property of pre-oxidized vanadium-titanium magnetite concentrate.

Effects of basicity and temperature on mineralogy and reduction behaviors of high-chromium vanadium-titanium magnetite sinters

The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscope(SEM),and metallographic microscope were employed in this study.In this work,the reduction of HCVTM sinter with different temperature and basicity were experimented.The Fe,FeO,and TiO in reductive samples increase with increasing basicity and temperatures.The increase of basicity and temperature is favorable to the reduction of HCVTM sinter.The Fe phase has out-migration tendency to the surface of sinter while the perovskite and silicate phases have in-migration tendency to the inside of sinter.The reduction degradation index(RDI)decreases while the reduction index(RI)increases with increasing basicity.The RI increases from 67.14%to 82.09%with increasing temperature from 1073 K to 1373 K.

Influence of Coke Content on Sintering Process of Chromium-containing Vanadium-titanium Magnetite

The sintering of chromium-containing vanadium-titanium magnetite using different coke contents was studied through the sintering pot tests, X-ray diffraction analysis and mineralogical phase analysis. Results showed that, as the coke content increased from 3.2% to 4.4%, the liquid phase and combustion zone thickness increased while the vertical sintering rate and ratio of sintered product decreased. In addition, the combustion ratio of exhaust gas also increased with increasing the coke content, indicating that combustion zone temperature also increased, and the excessive the coke content in the sintering process of vanadiumtitanium magnetite is harmful. As the coke content increased, the magnetite, silicates, and perovskite contents of the sintered ore increased while the contents of hematite and calcium ferrite of sintered ore decreased; drum strength decreased, and reduction degradation properties increased while reduction ability decreased. We found that the appropriate coke content for the sintering process is 3.6 wt%.

Three-liquid-phase extraction and separation of V(V) and Cr(VI) from acidic leach solutions of high-chromium vanadium–titanium magnetite

A new method by liquid-liquid-liquid three phase system, consisting of acidified primary amine N1923 （abbreviated as A-N1923）, poly（ethylene glycol） （PEG） and （NH4）2S04 aqueous solution, was suggested for the separation and simultaneous extraction of Ⅴ（Ⅴ） and Cr（Ⅵ） from the acidic leach solutions of high- chromium vanadium-titanium magnetite. Experimental results indicated that Ⅴ（Ⅴ） and Cr（Ⅵ） could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while AI（Ⅲ） and other co-existing impurity ions, such as Si（Ⅳ）, Fe（Ⅲ）, Ti（Ⅳ）, Mg（Ⅱ） and Ca（Ⅱ） in acidic leach solutions, could be enriched in the （NH4）2SO4 bottom aqueous phase. During the process for extraction and separation of Ⅴ（Ⅴ） and Cr（Ⅵ）, almost all of impurity ions could be removed. The separation factors between Ⅴ （Ⅴ） and Cr（Ⅵ） could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered Ⅴ（Ⅴ） and Cr（Ⅵ） in the top phase and middle phase respectively were all above 90%. Various effects including aqueous pH, A-N1923 concentration, PEG added amount and （NH4）2SO4 concentration on three-phase partitioning of Ⅴ（Ⅴ） and Cr（Ⅵ） were discussed. It was found that the partition of Cr（Ⅵ） into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of Ⅴ（Ⅴ） by A-N1923 resulted of anion exchange between NO; and H2V10O4-28. Stripping of Ⅴ（Ⅴ） and Cr（Ⅵ） from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NANO3 aqueous solutions and NaOH-（NH4）2SO4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium-titanium magnetite.

Wettability and corrosion behavior between alkaline slag from sodium smelting of vanadium-titanium magnetite and refractory substrates

The sodium smelting of vanadium-titanium magnetite can achieve the comprehensive utilization of Fe,V,and Ti.However,the generation of alkaline slag during this process may cause damage to refractory materials.The wettability and corrosion behavior of alkaline slag on three types of refractory(MgO-C,SiC,and high alumina refractory)substrates were investigated at temperatures up to 1200℃.The effects of duration on the wettability of molten slag on SiC substrates were also investigated.Results showed that the high alumina refractory exhibited better wettability with the molten slag than the others,and thus,it is easier to be corroded.The results of scanning electron microscopy coupled with energy dispersive spectroscopy showed that MgO-C and high alumina refractory substrates were severely eroded.There was a visible and regular interfacial reaction layer between the slag and SiC refractory substrate,which was produced by the redox reaction between the metal oxides in the slag and the SiC refractory substrate.With the increase in holding time,the interface layer expands and silico-ferrite phases are generated at the interface.The redox reaction between Fe_(2)O_(3) and SiC substrate is the main reason for the corrosion.By comparing the differences in wettability and corrosion behavior between the alkaline slag from sodium smelting of vanadium-titanium magnetite and MgO-C,SiC and high alumina refractories,it is concluded that SiC refractory has good corrosion resistance to the slag.Iron oxides in the slag accelerate the oxidation rate of SiC refractory.

Enrichment and reconfiguration of titanium-bearing phase in vortex smelting reduction process of vanadium-titanium magnetite

To comprehensively utilize the low-iron high-vanadium-titanium magnetite,a new method of vortex smelting reduction of vanadium-titanium magnetite was proposed,and the enrichment and reconstitution regularity of Ti-bearing phases in the slag was investigated through X-ray fluorescence spectrometry,X-ray photoelectron spectroscopy,X-ray diffraction analysis,and optical microscopy.The phase diagram revealed that the preferential crystallization of MgTi_(2)O_(5) can be achieved by adjusting the CaO,MgO,and TiO_(2) contents of slag.The predominant Ti-bearing phases in the slag obtained from the reduction process are MgxTi_(3_x)O_(5)(0≤x≤1)and CaTiO_(3).FeTiO_(3) is present at carbon-iron ratio(CR)=1.3,while MgTi_(2)O4 and TiC are formed at CR=1.3.The enrichment of TiO_(2) in the slag increases first and then decreases as the CR increases,and at CR=1.1,the enrichment of TiO_(2) in the slag reaches 51.3 wt.%.Additionally,the concentrations of MgxTi_(3_x)O_(5)(0≤x≤1)and CaTiO_(3) in the slag,along with the grain width of MgxTi_(3_x)O_(5)(0≤x≤1),decrease with the increase in CR.

白云鄂博矿区矿石中磁铁矿及萤石的X射线粉晶衍射半定量分析方法及矿物三维空间分布模型

白云鄂博超大型铁-稀土-铌矿床,伴生大量萤石等资源。现阶段,矿山资源评价采用的是多元素定量分析方法,该方法存在不能客观的表征出可用资源的矿物组成和赋存状态的缺陷。为了较为准确地确定元素赋存形式及磁铁矿、萤石矿物含量,本研究选用粉晶X射线衍射K值法定量分析法,通过以白云鄂博白云石为参比物质分别调配1∶1比例产自白云鄂博的磁铁矿、萤石与白云石单矿物样品,获得以白云石为参比的磁铁矿参比强度K_(Fe3O4)^(1)=0.61、萤石参比强度K_(CaF2)^(1)=2.51,同时,精选了白云鄂博其他常见共生矿物的K值,以实现对白云鄂博不同矿石类型中矿物含量的半定量分析,通过测试已知标样验证了改进优化K值的正确性和适用性。利用大量实际岩心矿石样品矿物定量分析数据,通过克里金插值法获得白云鄂博主矿磁铁矿和萤石矿物的空间分布三维模型,初步呈现了资源矿物的空间分布特征,推测在矿区深部仍存在巨大的找矿潜力。X射线粉晶衍射定量分析技术直接对可回收资源的矿物半定量分析研究,为矿山精准分采和资源综合利用探索了新的解决思路,也为选矿流程的优化提供的重要的技术参考。

干法重介质流化床中加重质颗粒与煤表面碰撞黏附特性研究

【目的】流态化干法分选技术是气固两相理论在选煤领域的拓展延伸。使用干法重介质流化床对原煤进行分选时,煤炭的表面水分便随着气流携带、颗粒运动等因素在床层中运移扩散,导致加重质发生颗粒团聚现象。颗粒聚团是由于流体作用以及颗粒间耗散作用形成的颗粒富集,是一种不均匀的介尺度结构。颗粒聚团可降低流化质量,导致床层失稳,床层内部密度分布不均,产品质量变差。【方法】以颗粒碰撞黏附过程为切入点,探究潮湿条件下加重质颗粒与煤表面之间的碰撞黏附特性。【结果】结果表明,随着碰撞速度的增加,颗粒法向碰撞恢复系数呈上升趋势;相同湿度条件下,碰撞速度相同时,恢复系数随着颗粒粒径的增加而呈上升趋势;潮湿条件下流化床中颗粒间碰撞的主要能量损失为颗粒表面黏弹性损失及液桥黏附能损失,随着相对湿度的增加,液桥力引起的黏附能损失逐渐增大,颗粒恢复系数显著降低。【结论】揭示了颗粒聚团碰撞黏附机理,这为实现分选流化床中颗粒聚团的调控、维持床层稳定流化、提高流化床分选效果提供理论依据。

氮掺杂冰粉基碳包覆Fe_(3)O_(4)及其储锂性能研究

碳包覆策略是能有效解决锂离子电池负极用过渡金属氧化物(TMO)材料在充放电过程中体积膨胀/收缩造成的粉化难题的一种有效途径。采用生物基可食用冰粉作为碳源与草酸高铁铵的水凝胶作为前驱物,经一步高温热解制备氮掺杂的冰粉基碳包覆Fe_(3)O_(4),采用XRD、SEM、TEM、XPS、TGA、拉曼光谱、恒电流充放电测试、循环伏安和电化学阻抗谱等方法对样品的形貌、结构和电化学性能进行研究。结果表明,该方法可快速大量制备氮掺杂碳包覆Fe_(3)O_(4)多孔复合材料(N-C@Fe_(3)O_(4)),通过调整原料配比和热处理条件,获得优异的电化学性能。N-C@Fe_(3)O_(4)-5作为锂离子电池负极材料具有良好的循环稳定性(在0.1 A/g电流密度下循环下80圈保持762.74 mAh/g比容量)和较高的倍率性能。相关机理研究表明N-C@Fe_(3)O_(4)复合材料良好倍率性能主要来源于赝电容容量的贡献。复合材料优异的电化学性能是由于碳包覆能够防止纳米颗粒团聚,提高导电性以及形成稳定的固体电解质界面(SEI)膜。冰粉基碳包覆TMO是一种改善其电化学储锂性能的有效途径,可推广并改善其他锂离子电池氧化物负极的储锂性能。

稠密气固分选流化床介质颗粒团聚特性研究

为掌握介质颗粒的团聚特性,给形成均匀稳定的流化床层提供指导,分析了不同水分含量下0~300μm介质颗粒流化后的表观黏度,并研究了煤炭外水含量、介质粒度对颗粒团聚特性的影响。结果表明,水分含量越高、颗粒粒度越细,颗粒表观黏度越大;随着剪切速率的增加,颗粒表观黏度逐渐下降。随着水分含量升高,各粒级颗粒团聚过程相似,粒级0~74μm、74~150μm、150~300μm颗粒形成稳定聚团所需水分含量分别为0.75%、1.0%、1.25%,即粒度越细所需水分含量越低。水分含量越高,聚团尺寸越大;粒度越小,聚团的尺寸分布跨度越宽。随着水分含量升高,煤粉混合后的二元加重质颗粒聚团尺寸在水分含量1.75%时明显增大,聚团尺寸分布跨度窄,表明二元加重质颗粒聚团对水分变化敏感度较低。

Optimization of BF Slag for High Cr_2O_3 Vanadium-titanium Magnetite

In order to clarify the slag system of high Cr2O3 vanadium-titanium magnetite smelting in BF （blast furnace）, the melting properties of slag samples prepared by analytically pure reagents were measured. By means of orthogonal test synthetic weighted score method, the optimal slag for high Cr2O3 vanadium-titanium magnetite was obtained, which contained 10% MgO, 8% TiO2 and 15% Al2O3, with the binary basicity being 1.15. In addition, the effects of basicity, MgO, TiO2 and A12 03 on slag melting properties were investigated by single factor test, and the results showed that, with increasing the basicity or TiO2 content, melting temperature （Tin） increased, whereas initial vis- cosity （r/0） and high temperature viscosity （r/h） decreased. With increasing the MgO content, Tm decreased firstly and then increased. With increasing the Al2 O3 content, Tm increased, and η0 and r/h decreased firstly and then increased.

Oxidation Kinetics,Structural Changes and Element Migration during Oxidation Process of Vanadium-titanium Magnetite Ore

The oxidation kinetics, structural changes, and elements migration during the oxidation process of the va- nadium-titanium magnetite （VTM） ore were analyzed. Kinetics analysis indicated that the oxidation process was con- trolled by diffusion control and could be divided into interface diffusion and lattice diffusion with apparent activation energy of 99.69 kJ/mol and 144.08 kJ/mol in the range of 800--1000℃, respectively. The surface structure changed with the oxidization temperature as follows： dense surface→nano sized sheets→submicron particles→molten particles. The compact structure changed into porous one because of the elements migration and enrichment. Both Fe and Ti elements migrated in the opposite direction during the oxidation process. The V etement in the raw ore stably existed in the form of V^5＋ state, some vanadium migrated and occupied the tetrahedral sites of the hematite during the oxidation process.

Carbothermic Reduction Mechanism of Vanadium-titanium Magnetite

To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.

磁性载体强化混凝和磁力旋流澄清池组合工艺的中试试验研究

以磁铁矿粉为原料,采用球磨混合和表面酸反应“一步法”生产工艺制备得到磁性载体,经表征分析,磁性载体保持了良好的磁响应性,表层生成羟基硫酸铁活性组分,相比磁铁矿粉,磁性载体BET表面积增加到了2.8倍、Langmuir表面积增加到了6.9倍,在混凝过程中能够强化对水中污染物的混凝吸附作用。通过40 t/d处理规模磁力旋流澄清中试试验系统,比较了混凝沉淀、磁混凝沉淀和磁性载体强化混凝三个过程,用磁性载体替代PAC和磁铁矿粉混合投加的磁混凝过程后,出水COD平均为34.7 mg/L,出水总磷平均为0.30 mg/L,与磁混凝过程对COD和总磷的去除率接近,表明磁性载体强化混凝能够实现磁混凝的出水目标,其污泥产量更少、运行管理更方便。

Kinetics and mechanism of coal-based direct reduction of highchromium vanadium-titanium magnetite

High-chromium vanadium-titanium magnetite(HCVTM)is a valuable resource containing metal elements such as iron,vanadium,titanium,and chromium.To recycle these elements,direct reduction is an efficient way.The mechanism and reaction kinetic parameters for the direct reduction of HCVTM were studied.Experimental results show that the reduction degree increases obviously when the C/O ratio and temperature increase.Thermodynamic analysis showed a dramatic mass loss in the direct reduction of HCVTM in the temperature range of 985-1160℃.From 1200 to 1350℃,the reduction curves for the isothermal reduction of HCVTM followed the same trend,with a sharp increase in the initial reaction zone and a slight increase in the reduction rate with increasing time,and finally,the isothermal reduction process of HCVTM was divided into several limiting stages with varying degrees,with inconsistent limiting factors for the reaction rate at different stages.The results also show that the activation energy decreases slightly at larger degrees of reduction.Also,the apparent rate constant k(T)increased with increasing reduction temperature,with lnk(T)showing a good linear relationship with temperature.

A promising method to recover spent V_(2)O_(5)-WO_(3)/TiO_(2) catalyst: treatment by vanadium-titanium magnetite sintering process

A large number of spent selective catalytic reduction(SCR)denitration catalysts are produced after the ultra-low emission transformation of coal-fired power plants in China.According to the China’s“Directory of National Hazardous Wastes(Version 2021)”,these spent vanadium-tungsten-titanium catalysts are classified as“HW50”hazardous waste,and their disposal and utilization processes have been strictly controlled.Thus,an effective and low-cost technique was developed to treat and utilize these spent SCR catalysts by the vanadium-titanium magnetite sintering process.Effects of adding spent SCR catalysts on the sintering production process and product quality indexes of sinter were studied.The results showed that adding spent SCR catalysts can improve the sintering granulation and green feed permeability,thereby increasing the productivity and flame front speed.When the addition proportion of spent SCR catalysts is less than 1 wt.%,the performance indexes of the finished sinter are basically equal to those of the finished sinter without adding spent SCR catalysts.Further increasing the proportion of spent SCR catalysts to 2.0 wt.%results in a decrease in product quality indexes,which could be attributed to the increase in perovskite content in the finished sinter.

磁铁尾矿粉对水泥胶砂性能的影响

为了研究磁铁尾矿粉对水泥胶砂性能的影响,进行了单掺磁铁尾矿粉试验、磁铁尾矿粉与矿物掺和料(石灰石粉、石英粉和粉煤灰)复合试验、磁铁尾矿粉与石膏复合试验。试验结果表明:磁铁尾矿粉对水泥胶砂的流动度具有不利影响,但适量磁铁尾矿粉具有增强其抗折强度的作用;磁铁尾矿粉复合粉煤灰,随着磁铁尾矿粉掺入比例的增大,水泥胶砂的强度减小;磁铁尾矿粉复合惰性掺和料,当磁铁尾矿粉含量在10%时,矿物掺和料单位强度贡献率最高,且对抗折强度的贡献率高于抗压强度,但当磁铁尾矿粉含量超过10%时,对抗压强度有负作用;磁铁尾矿粉复合石膏,适当增加石膏的掺量,对提高水泥胶砂的性能是有利的。

掺天然磁铁矿粉沥青混合料电磁波吸收性能

为提高沥青路面电磁波吸收能力,以天然磁铁矿粉为吸收剂制备了沥青混合料试样,采用矩形波导法测试了不同天然磁铁矿粉取代率下试样的电磁参数（复介电常数与复磁导率）,并基于传输线理论计算了掺天然磁铁矿粉沥青路面的反射损耗.结果表明：随天然磁铁矿粉品位与取代率的增加,试样复介电常数实部明显增大,虚部变化不大;试样复磁导率实部与虚部都随天然磁铁矿粉品位与取代率的增加而增大.品位60以上的天然磁铁矿粉均能制备出电磁波反射损耗小于-10dB的沥青混合料.掺天然磁铁矿粉沥青混合料在其厚度为2～11cm时存在3个匹配厚度（3,5,7cm）,结合路面工程要求与经济性,掺天然磁铁矿粉吸波沥青路面上面层设计厚度合理建议值为3cm.路面上面层设计厚度大于3cm时,可适当降低天然磁铁矿粉取代率.