A novel process for the recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite:sodium modification–direct reduction coupled process

A sodium modification–direct reduction coupled process was proposed for the simultaneous extraction of V and Fe from vanadium-bearing titanomagnetite.The sodium oxidation of vanadium oxides to water-soluble sodium vanadate and the transformation of iron oxides to metallic iron were accomplished in a single-step high-temperature process.The increase in roasting temperature favors the reduction of iron oxides but disfavors the oxidation of vanadium oxides.The recoveries of vanadium,iron,and titanium reached 84.52%,89.37%,and 95.59%,respectively.Moreover,the acid decomposition efficiency of titanium slag reached 96.45%.Compared with traditional processes,the novel process provides several advantages,including a shorter flow,a lower energy consumption,and a higher utilization efficiency of vanadium-bearing titanomagnetite resources.     

Carbothermic reduction characteristics of ludwigite and boron-iron magnetic separation

Ludwigite is a kind of complex iron ore containing boron, iron, and magnesium, and it is the most promising boron resource in China. Selective reduction of iron oxide is the key step for the comprehensive utilization of ludwigite. In the present work, the reduction mechanism of ludwigite was investigated. The thermogravimetry and differential scanning calorimetry analysis and isothermal reduction of ludwigite/coal composite pellet were performed. Ludwigite yielded a lower reduction starting temperature and a higher final reduction degree compared with the traditional iron concentrates. Higher specific surface area and more fine cracks might be the main reasons for the better reducibility of ludwigite. Reducing temperature highly affected the reaction fraction and microstructure of the reduced pellets, which are closely related to the separation degree of boron and iron. Increasing reducing temperature benefited the boron and iron magnetic separation. Optimum magnetic separation results could be obtained when the pellet was reduced at 1300℃. The separated boron-rich non-magnetic concentrate presented poor crystalline structure, and its extraction efficiency for boron reached 64.3%. The obtained experimental results can provide reference for the determination of the comprehensive utilization flow sheet of ludwigite.     

A novel endorectal RF coil for high resolution MRI and spectroscopy of the prostate

The diagnosis of prostate diseases by magnetic resonance imaging (MRI) in vivo is sometimes difficult for the lower signal to noise ratio (SNR). To increase the SNR of the prostate image, we designed a RF coil that can be inserted into rectum and was named endorectal coil. The properties of RF coil were evaluated using a network analyzer. Moreover the images and spectroscopy of a special phantom were acquired and the results were compared to those of the commercial TORSO coil (G.E. Medical Systems, USA). Our coil gave a significantly higher SNR at the region of interest (ROI). The achieved high local SNR and resulting high spatial resolution would add more anatomic and biochemical information to the diagnosis of prostate diseases.     

New primitive ichthyosaurian （Reptilia,Diapsida） from the Middle Triassic of Panxian,Guizhou, southwestern China and its position in the Triassic biotic recovery

A new primitive ichthyopterygian Xinminosaurus catactes gen. et. sp. nov. is erected based on a complete skeleton from the Middle Triassic Upper Member of the Guanling Formation at Panxian, Guizhou, southwestern China. It has a suite of uniquely derived char- acters in its dentition, ulna, carpals and tarsals. It is similar to primitive ichthyopterygians in retaining elongated limb bones. The new taxon and a diversity of marine reptiles in Panxian Fauna are the physical markers of the Middle Triassic Biotic radiation. Detailed studies of this fauna will supply essential knowledge on the diversity, migration and paleobiogeographic affinity of Middle Triassic ichthyopterygians.     

Learning,Mutation and the Economics of Convention:A Selected Review of Evolutionary Game Theory

Before the present of basic model,one example is given in section 2 to illustrate the economic intuition behind the SSE. The general model,including the three hypotheses,adaptive play setting and basic results is laid out in section 3. Sections 4 study the asymptotic behavior of this model. This review concludes with a comment.     

Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation: A case study from the Neoproterozoic Doushantuo Formation, Guizhou Province,South China

The Neoproterozoic Doushantuo Formation at Weng'an in Guizhou Province of South China consists of phosphorites and dolomites.Three types of samples are recongnized for the phosphate-bearing rocks.In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin.The Type II samples are interbedded phosphorites and dolomites.Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed.Phosphates of Type I and II samples show similar low δ18Ophos (SMOW) values of 10.9‰～12.1‰ and 10.7‰～12.8‰, respectively, whereas Type III phosphates show higher δ18Ophos (SMOW) values of 13.2‰～15.0‰.Dolomites from Type I and II samples have δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -6.2‰～-3.4‰ and -2.2‰～-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -12.9‰～-8.6‰ and -4.4‰～-2.6‰.Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater.Calculations of palaeocean temperatures from the most 18O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period.Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng'an, Guizhou Province.     

Detrital zircon U–Pb geochronology and Hf isotopic compositions of Middle–Upper Ordovician sandstones from the Quruqtagh area,eastern Tarim Basin:implications for sedimentary provenance and tectonic evolution

Figuring out whether the sedimentary provenance regions of the thick deep-water turbidite systems deposited during Middle–Upper Ordovician in South Quruqtagh are the intracontinental uplifts or the peripheral orogenic belts is of great significance for us to understand the tectono-sedimentary nature of the northeastern Tarim Basin and basin-range coupling processes in the middle Paleozoic.This paper reports the in situ LA-ICP-MS U–Pb ages and Hf isotope data on detrital zircons from two Middle–Upper Ordovician sandstone samples which were collected from the Charchag Formation and the Zatupo Formation in South Quruqtagh,respectively.The results show that the studied two samples have extremely similar U–Pb age patterns and Hf isotopic compositions,reflecting multiphase tectonothermal events with age groups of 527–694,713–870 Ma(peaking at 760 Ma),904–1,090,1,787–2,094 Ma(peaking at 1,975 Ma)and 2,419–2,517 Ma.Combining previous studies,the presence of age groups of 713–1,090 and1,787–2,094 Ma,respectively,demonstrates that Tarim had ever been a part of Rodinia and Columbia supercontinent.Moreover,98%of 713–870 Ma detrital zircons are characterized by negative e Hf(t)values ranging from-38.07 to-0.61,which are highly consistent with those of Neoproterozoic granites from the Quruqtagh area.No Early Paleozoic ages(*470–500 Ma)signifying subduction or collision events in Altyn Tagh were detected in the two samples,indicating that the Middle–Late Ordovician sediments in South Quruqtagh and northern Mangar depression were mainly derived from intracontinental uplifts,i.e.,the North Quruqtagh uplift or the Tabei paleo-uplift,rather than the Altyn Tagh.In conjunction with regional sedimentary-tectonic background and previous studies,we proposed preliminarily that the northeastern Tarim remained as a passive continental margin in Late Ordovician and changed into an active-continental margin in Silurian due to the southward subduction of the South-Tianshan Ocean.     

高炉灰为还原剂对海滨钛磁铁矿直接还原焙烧磁选--钛铁分离的影响

对高炉灰在直接还原焙烧-弱磁选工艺中用作印尼某海滨钛磁铁矿还原剂的可行性及其机理进行研究.结果表明,以萤石为添加剂的条件下,高炉灰可代替煤做还原剂,通过高炉灰与萤石的共同作用,可以在直接还原过程中提高还原铁粉中铁的回收率及品位并降低TiO2质量分数,同时回收高炉灰中铁.三种不同产地高炉灰还原效果的比较表明,高炉灰性质对还原效果有影响.在相同用量条件下,津鑫高炉灰( JX)还原效果最好;在JX高炉灰用量30%、萤石用量10%、焙烧温度1250益以及焙烧时间为60 min时,焙烧产物通过两段磨矿和两段磁选,最终得到最佳的还原铁粉中铁品位为91.28%,TiO2质量分数降至0.93%,包括海滨砂矿和高炉灰中铁的铁总回收率达到89.19%.     

Leaching of vanadium,sodium, and silicon from molten V-Ti-bearing slag obtained from low-grade vanadium-bearing titanomagnetite

The water leaching process of vanadium, sodium, and silicon from molten vanadium-titanium-bearing (V-Ti-bearing) slag obtained from low-grade vanadium-bearing titanomagnetite was investigated systematically. The results show that calcium titanate, sodium aluminosilicate, sodium oxide, silicon dioxide and sodium vanadate are the major components of the molten V-Ti-bearing slag. The experimental results indicate that the liquid-solid (L/S) mass ratio significantly affects the leaching process because of the respective solubilities and diffusion rates of the components. A total of 83.8% of vanadium, 72.8% of sodium, and 16.1% of silicon can be leached out via a triple counter-current leaching process under the optimal conditions of a particle size below 0.074 mm, a temperature of 90°C, a leaching time of 20 min, an L/S mass ratio of 4:1, and a stirring speed of 300 r/min. The kinetics of vanadium leaching is well described by an internal diffusion-controlled model and the apparent activation energy is 11.1 kJ/mol. The leaching mechanism of vanadium was also analyzed.     

A method for recovery of iron,titanium, and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures: low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.     

A method for recovery of iron,titanium, and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures:low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200℃, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.     

钒钛磁铁精矿直接还原过程中金属铁颗粒长大特性

通过钒钛磁铁矿精矿直接还原实验,研究了不同还原剂和添加剂对还原过程金属铁颗粒长大的影响.提高还原温度能促进还原产物中金属铁颗粒的长大,金属铁颗粒中V含量也显著增加.与用无烟煤和褐煤还原产物相比,用烟煤还原产物中金属铁颗粒明显长大,这是由烟煤中高灰分含量所引起的.金属铁颗粒长大机理的研究表明:Na2CO3和Na2SiO3的熔点较低,且能破坏铁橄榄石和铁尖晶石的结构,并生成一些低熔点物质,而SiO2能与铁橄榄石形成低共熔混合物.这些低熔点物质都有助于改善金属铁相的扩散,从而促进金属铁颗粒长大.     

钒钛磁铁精矿冷固球团催化还原机理

对添加剂催化钒钛磁铁精矿冷固球团直接还原行为进行了详细的研究 ,包括添加剂种类和用量及催化剂催化还原机理 .研究结果表明 :在 1 0 50～ 1 1 0 0℃ ,m(C)∶m(Fe)为 0 .5～ 0 .6 ,还原时间 3h的条件下 ,添加DA 2催化剂与常规的Na2 SO4或Na2 CO3相比 ,钒钛磁铁精矿冷固球团煤基直接还原所得产品的金属化率提高 3 .1 %～ 4 .6 % ;该金属化球团经磨矿磁选进行铁和钒钛分离时 ,所得磁性产品 (直接还原铁粉 )中铁的品位提高 5 .30 %～ 5 .43 % ,非磁性物中TiO2 ,V2 O5 的品位分别提高 2 .76 %～ 3 .87%和 0 .2 7%～ 0 .45 % ,TiO2 ,V2 O5 的回收率分别提高 1 4 .68%～1 3 .0 8%和 4.1 3 %～ 6 .97% .SEM及XPS等微观测试结果表明 :添加剂DA 2的作用机理为加速铁氧化物还原 ,促进铁晶粒的长大 ,降低还原球团中MFe与TiO2 晶粒嵌布的紧密程度 ,从而强化了铁与钒钛的磁选分离     

以煤泥为还原剂海滨钛磁铁矿直接还原焙烧反应历程

研究以煤泥为还原剂,印尼某海滨钛磁铁矿在直接还原焙烧过程中,不同焙烧温度下矿物组成变化规律. X射线衍射和扫描电镜分析结果表明,随着焙烧温度的升高,钛磁铁矿逐渐被还原. 其中铁矿物经过浮士体( FeO) ,最终被还原成金属铁;而钛则经过钛尖晶石最终生成钛铁矿和少部分的铁板钛矿. 在整个直接还原焙烧过程中,金属铁颗粒在1100℃左右生成,然后不断长大,在1250℃时金属铁颗粒明显增多,在之后的保温过程中,金属铁颗粒不断长大,并在此过程中将金属铁从中分离出来.     

钒钛铁精矿内配碳球团高温快速直接还原历程

采用高温实验炉,在1 350℃,氮气保护气氛条件下对钒钛磁铁精矿内配碳球团进行了阶段还原试验,通过TG-DSC、XRD、SEM等检测方法对不同时间内配碳球团还原的组织成分、显微结构等进行研究。结果表明,钒钛铁精矿的还原历程依次为Fe2TiO4和Fe3O4、3(Fe3O4).Fe2TiO4、Fe3O4.Fe2TiO4、Fe2TiO4和FeO、Fe和FeTi2O5;在磁铁矿大量还原生成浮士体的阶段,钛铁矿与新生成的浮士体发生钛铁晶石化,最终还原转变为单质铁和含铁黑钛石。     

Recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation: process optimization and mineralogical study

Currently, the majority of copper tailings are not effectively developed. Worldwide, large amounts of copper tailings generated from copper production are continuously dumped, posing a potential environmental threat. Herein, the recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation was conducted; process optimization was carried out, and the corresponding mineralogy was investigated. The reduction time, reduction temperature, reducing agent (coal), calcium chloride additive, grinding time, and magnetic field intensity were examined for process optimization. Mineralogical analyses of the sample, reduced pellets, and magnetic concentrate under various conditions were performed by X-ray diffraction, optical microscopy, and scanning electron microscopy-energy-dispersive X-ray spectrometry to elucidate the iron reduction and growth mechanisms. The results indicated that the optimum parameters of iron recovery include a reduction temperature of 1150℃, a reduction time of 120 min, a coal dosage of 25%, a calcium chloride dosage of 2.5%, a magnetic field intensity of 100 mT, and a grinding time of 1 min. Under these conditions, the iron grade in the magnetic concentrate was greater than 90%, with an iron recovery ratio greater than 95%.     

Application of a water cooling treatment and its effect on coal-based reduction of high-chromium vanadium and titanium iron ore

A water cooling treatment was applied in the coal-based reduction of high-chromium vanadium and titanium (V–Ti–Cr) iron ore from the Hongge region of Panzhihua, China. Its effects on the metallization ratio (η), S removal ratio (R_S), and P removal ratio (R_P) were studied and analyzed on the basis of chemical composition determined via inductively coupled plasma optical emission spectroscopy. The metallic iron particle size and the element distribution of Fe, V, Cr, and Ti in a reduced briquette after water cooling treatment at 1350°C were determined and observed via scanning electron microscopy. The results show that the water cooling treatment improved the η, R_S, and R_P in the coal-based reduction of V–Ti–Cr iron ore compared to those obtained with a furnace cooling treatment. Meanwhile, the particle size of metallic iron obtained via the water cooling treatment was smaller than that of metallic iron obtained via the furnace cooling treatment; however, the particle size reached 70 μm at 1350°C, which is substantially larger than the minimum particle size required (20 μm) for magnetic separation. Therefore, the water cooling treatment described in this work is a good method for improving the quality of metallic iron in coal-based reduction and it could be applied in the coal-based reduction of V–Ti–Cr iron ore followed by magnetic separation.