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%.

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.

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.

Density functional theory(DFT) studies of vanadium-titanium based selective catalytic reduction(SCR) catalysts

Based on density functional theory(DFT)and basic structure models,the chemical reactions on the surface of vanadium-titanium based selective catalytic reduction(SCR)denitrification catalysts were summarized.Reasonable structural models(non-periodic and periodic structural models)are the basis of density functional calculations.A periodic structure model was more appropriate to represent the catalyst surface,and its theoretical calculation results were more comparable with the experimental results than a nonperiodic model.It is generally believed that the SCR mechanism where NH3 and NO react to produce N2 and H2 O follows an Eley-Rideal type mechanism.NH2 NO was found to be an important intermediate in the SCR reaction,with multiple production routes.Simultaneously,the effects of H2 O,SO2 and metal on SCR catalysts were also summarized.

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.

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.

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.

Effect of oxygen enrichment on sintering behavior of high proportion vanadium-titanium magnesite concentrates

To achieve high-efficiency utilization of complex and unmanageable iron-containing minerals,the effects of oxygen enrichment on productivity,yield,flame front speed,exhaust gas peak temperature,and desulphurization reaction of the vanadium-titanium magnetite sintering process as well as sinter tumble index and mineralogy were clarified,with oxygen enrichment concentrations ranging from 21 to 29 vol.%.Results indicated that with increasing the oxygen enrichment concentration from 21 to 27 vol.%,the flame front speed increased from 30.3 to 40.0 mm min^(-1),the yield enhanced from 72%to 77%,and the productivity augmented from 1.83 to 2.67t m^(-2)h^(-1);in the meantime,the tumble index was improved from 73.7%to 77.9%,and the exhaust gas peak temperature rose from 376.4 to 484.8℃.The main reason for the improvement in sintering properties was the increased combustibility of fuels and the generation of proper liquid phase that improved the permeability of the packed bed.The improved sinter strength is mainly due to the increase in the phase fraction of silico-ferrites of calcium and aluminium.In addition,oxygen enrichment sintering could significantly increase the desulphurization level of vanadium-titanium magnetite sinter and the rate of desulphurization reaction during sintering process.

新疆巴楚小海子岩体铁钛成矿特征及资源利用前景

新疆巴楚小海子是近年来在塔里木大火成岩省探获的一个低品位-大吨位岩浆型钒钛磁铁矿床,其成岩成矿机制以及资源利用前景尚不清楚。文章针对小海子岩体2种含矿岩相橄榄辉长岩和橄榄辉石岩开展了地质地球化学研究。橄榄辉长岩相和橄榄辉石岩相虽然在空间上关系不明,但岩相学观察表明它们矿物组成的差异与矿物堆晶作用有关,且二者具有相似的稀土元素球粒陨石标准化和微量元素原始地幔标准化配分曲线,说明是同源岩浆演化的产物,橄榄石较低的Fo值(67.9~72.5)指示幔源母岩浆在深部岩浆房中发生了分异。小海子岩体和与相距约45 km的瓦吉里塔格相比,岩石组成和地球化学组成相似,表明为同源岩浆成因,但后者矿物组成变化范围更大,指示瓦吉里塔格岩体在形成过程中经历了更高程度的分离结晶作用,这可能是造成瓦吉里塔格岩体比小海子岩体的w(TiO_(2))更高的原因。小海子岩体虽然w(TiO_(2))较低(3%~4%),但铁钛氧化物固溶体分离结构不发育,且矿物颗粒粗大,使得铁和钛选矿解离比中国其他地区的钒钛磁铁矿更为容易,因此钛资源利用前景巨大,笔者建议出台地方性的勘查技术规范,为这类铁钛资源的开发利用提供技术标准。

常温常压下盐酸浸出分离钒钛磁铁精矿中有价金属的试验研究

攀西钒钛磁铁矿组成及矿物结构复杂,难以低成本、高效综合利用其中的有价元素。针对此问题,本文采用常温常压盐酸浸出的方法对该矿物进行了试验探索,考察了盐酸初始质量浓度、浸出液固比、浸出时间、浸出搅拌转速率等主要因素对Fe、TiO_(2)和V_(2)O_(5)浸出率的影响,并通过矿物结构分析了钒钛磁铁精矿中铁、钒、钛分离的机理,得到以下主要结论。盐酸常温常压浸出的较佳工艺条件为盐酸初始浓度20.5%、浸出液固比12:1、浸出时间3.5 h、浸出搅拌转速率600 r/min,该条件下Fe、V_(2)O_(5)和TiO_(2)浸出率分别为84.15%、80.80%、10.05%,浸渣中Fe、V_(2)O_(5)和TiO_(2)品位分别为26.78%、0.378%和32.58%,实现了钛资源的初步富集;盐酸优先溶解试样中钛磁铁矿矿物的主晶矿物磁铁矿,铁、钒优先进入浸出液,而客晶矿钛铁矿及独立钛铁矿被破坏程度极小,富集于浸渣中;该浸出方法不需要额外的加热和加压设备,具有成本低、能源消耗和设备投资较低、操作简便、环境友好的优势,但浸出指标有待提高,后续需要进一步探索催化剂对常温常压酸浸工艺的影响。

攀西某钒钛磁铁矿中钛的赋存状态研究

对攀西某钒钛磁铁矿化学组成、矿物种类及含量、含钛矿物能谱微区成分、矿石中TiO_(2)的平衡概算、含钛矿物产出形式、钛铁矿粒度及解离度等进行详细研究,查清了矿石难选的原因,综合分析了钛精矿的技术指标以及影响选钛效果的主要矿物学因素,可为开发利用攀西某矿产资源提供详细的科学依据。

中国钒钛磁铁矿资源概况及综合利用技术进展

钒钛磁铁矿是以铁、钒和钛为主金属的复合型矿产资源,通常伴生有铜、钴、磷、钪等多种有价组分,具有综合回收利用价值。在概述了中国钒钛磁铁矿资源特点的基础上,针对资源逐渐贫细杂化、综合利用水平较低的状况,着重就预选工艺、铁精矿提质降杂工艺、微细粒钛铁矿选别工艺、伴生资源回收利用工艺技术进展进行了总结,最后分析了目前钒钛磁铁矿选矿存在的工艺技术问题,并指出高效、清洁、可持续发展是未来钒钛磁铁矿选矿技术发展的大方向。

烧结熔剂对钒钛磁铁矿液相高温行为的影响

为了改善钒钛磁铁矿的烧结液相行为,采用微型烧结方法研究了不同熔剂对钒钛磁铁矿液相高温行为的影响.结果表明:从钒钛磁铁矿的液相高温行为考虑,白云石适合做低钛型钒钛矿的烧结熔剂,石灰石适合做低钛型或中钛型钒钛矿的烧结熔剂;与高钛型钒钛矿相匹配的熔剂为高活性的生石灰,菱镁石并不适合做钒钛矿的烧结熔剂.因此,优化钒钛磁铁矿的液相高温行为应根据矿石中的钛含量,调节烧结熔剂中石灰石和高活性生石灰的配比,以及不同性能石灰石和高活性生石灰的使用量.

攀西钛资源综合利用技术应用现状及发展方向

我国四川省攀西地区钒钛磁铁矿资源中钛资源储量巨大,主要以钛精矿形式回收利用,并主要用于硫酸法钛白和酸溶性钛渣生产原料,其产量占全国钛原料市场的75%以上。硫酸法钛白工艺技术成熟,已形成相对完整的“内循环”,但尚未全面突破硫酸法钛白联产技术;电炉冶炼酸溶性钛渣工艺技术较成熟,主流工艺是钛精矿不预处理-实心圆形电极-密闭圆形电炉连续冶炼工艺,钛精矿酸性氧化球团-电炉冶炼一步法工艺、大功率矩圆形电炉冶炼酸溶性钛渣等钛渣新工艺发展较快、发展空间大,是今后主要发展方向。目前攀西地区发展钛产业的一个主要问题是缺乏沸腾氯化法钛白工艺需求的高品位钛资源,未来需要突破攀西高钙镁钛精矿除杂提质制取高品位高钛渣关键核心技术,并同时研发攻关硫酸法钛白附产绿矾和钛石膏回收循环利用技术、高炉钛渣提钛及综合利用技术、钒钛铁精矿非高炉炼铁新技术,以及以钛精矿、钛渣或钛白粉为原料制备含钛及钛基新材料技术,以期获得攀西钛产业的健康可持续发展。