钒钛磁铁矿金属化还原-选分-电热熔分新工艺

针对攀枝花钒钛磁铁矿进行了金属化还原-选分-电热炉熔分实验,考察了磁场强度、还原温度、还原时间、配碳比、还原煤粒度对金属化还原及磁选分离效果的影响.实验结果表明,当磁场强度50mT、还原温度1350℃、还原时间60min、配碳比10、还原煤粒度为-75μm时,金属化还原后产物及磁选分离磁性物质、非磁性物质的各项指标最佳,进一步进行电热炉熔分可实现铁钒分离.新工艺达到铁钒钛资源高效分离要求,铁钒钛收得率分别为9507%,7160%和8008%.     

基于田口法的钒钛磁铁矿热压块抗压强度的优化

使用田口法探索了影响钒钛磁铁矿热压块抗压强度的重要因子,并通过信噪比分析计算各因子对抗压强度的贡献率,最终给出钒钛磁铁矿热压块的最佳制备条件.实验结果表明,在热压温度、配碳比、煤粉粒度三个影响因素中,煤粉粒度对抗压强度的影响程度最大,其贡献率达到了79.99%,温度和配碳比二者的贡献率分别为15%和3.63%.优化后钒钛磁铁矿热压块的制备参数为热压温度300℃、煤粉粒度75μm、配碳比1.8.在优化后的参数下进行验证实验,得到的钒钛矿热压块的平均抗压强度达到1 152.1 N.     

热压含碳球团冷态强度的实验研究

重点考察了煤种及热压工艺参数对热压含碳球团冷态强度的影响,并探讨了热压含碳球团获得高强度的机理.研究表明,煤种、配煤量、热压温度、配煤粒度及热压压力等热压工艺参数对热压含碳球团强度具有显著影响,其中热压温度是影响冷态强度最重要的因素.热压工艺利用煤的热塑性保证煤矿颗粒充分接触,增大粘结面积,从而使热压含碳球团的强度高于冷固结含碳球团.从冷态强度角度出发,以鹤岗烟煤为原料生产热压含碳球团的适宜工艺参数为配煤量25%~35%,热压温度450℃,配煤粒度<90μm,热压压力不低于35 MPa.     

钒钛磁铁矿含碳球团还原的影响因素

通过单因素实验考察了还原温度、还原时间及碳氧摩尔比（nC/nO）对钒钛磁铁矿含碳球团还原的影响,结合扫描电镜照片解释了钒钛磁铁矿的还原机理.实验结果表明,适当升高还原温度、延长还原时间及增加碳氧摩尔比均可以促进钒钛磁铁矿的还原,并且金属化率随还原温度的升高先急剧升高而后趋于平缓,随着还原时间的延长及碳氧摩尔比的增加而先升高后降低,而残碳量随着反应的进行不断降低.当还原温度为1350℃,还原时间为30 min,碳氧摩尔比为1.2时,球团的金属化率达到最大值.通过扫描电镜照片可以看出,球团在还原过程中形成了铁连晶,并且在不同的还原条件下铁连晶的大小及形态不同.     

Ferronickel enrichment by fine particle reduction and magnetic separation from nickel laterite ore

Ferronickel enrichment and extraction from nickel laterite ore were studied through reduction and magnetic separation. Reduction experiments were performed using hydrogen and carbon monoxide as reductants at different temperatures (700–1000°C). Magnetic separation of the reduced products was conducted using a SLon-100 cycle pulsating magnetic separator (1.2 T). Composition analysis indicates that the nickel laterite ore contains a total iron content of 22.50wt% and a total nickel content of 1.91wt%. Its mineral composition mainly consists of serpentine, hortonolite, and goethite. During the reduction process, the grade of nickel and iron in the products increases with increasing reduction temperature. Although a higher temperature is more favorable for reduction, the temperature exceeding 1000°C results in sintering of the products, preventing magnetic separation. After magnetic separation, the maximum total nickel and iron concentrations are 5.43wt% and 56.86wt%, and the corresponding recovery rates are 84.38% and 53.76%, respectively.     

工艺参数对热压铁焦抗压强度的影响

热压铁焦是一种新型含碳复合炉料,高炉使用铁焦有助于降低热空区温度、减少CO_2排放.研究了工艺参数对热压铁焦抗压强度的影响,并分析其作用机理.研究结果表明,在一定范围内,铁焦抗压强度随着铁矿粉配比增加先增加后降低,在矿粉配比15%时取得较大值3 490.89 N;随着烟煤配比的增加而提高;随着热压温度的提高而提高,在热压温度350℃时取得较大值4 305.50 N;随着炭化温度的提高先降低后提高;随着炭化时间的增加先提高后降低,在炭化时间4 h时取得较大值3 518.80 N.从抗压强度角度考虑,热压铁焦合适的制备工艺参数为10%~15%铁矿粉,60%~70%烟煤,热压温度300~350℃,炭化温度1 000~1 100℃,炭化时间2~4 h.     

含硼铁精矿选择性还原-选分新工艺的实验研究

针对现有含硼铁精矿硼铁分离工艺所存在的弊端,提出了含硼铁精矿选择性还原-选分新工艺,并通过热力学分析和实验室研究进行了验证.研究表明:对于辽宁凤城Fe和B2O3质量分数分别为5605%和386%的含硼铁精矿,最佳的选择性还原-选分工艺参数如下:配碳比08~10,还原温度1275~1300℃,还原时间不小于20min,还原煤粒度为-0075mm,分选时的磁场强度为50mT.得到的选分产物为高金属化率的金属铁粉,可进一步处理用于钢铁生产;选分尾矿为高品位的含硼资源,可作为硼工业的优质原料.     

碳热还原氮化一步法制备钒氮合金工艺研究

对V2O5自还原氮化过程进行热力学分析,并以工业级V2O5和炭黑为原料,经过混料、研磨、压制成块后进行烧结和还原氮化,制得含氮量较高的钒氮合金。结果表明,为了避免V2O5在还原过程中挥发,预还原温度应控制在V2O5熔点(678℃)以下;经过650℃预还原4h,试样中的V2O5才能全部转化为低价态的钒氧化物;V2O5在N2气氛下自还原时,还原终温低于1 271℃时,还原产物优先生成VN,还原终温高于1 271℃时,还原产物中才会出现大量VC;为保证还原产物的高氮和低碳含量,应将还原氮化最终温度控制在1 200～1 300℃。     

高铬型钒钛磁铁矿配量增加对氧化球团质量的影响

采取“细磨处理高铬型钒钛磁铁矿”和“以粒度较细的廉价欧控矿代替现场生产用矿”两种优化措施，考察了高铬型钒钛磁铁矿配量增加对氧化球团质量的影响，探索了高铬型钒钛矿在球团原料中配量增加的可行性.结果表明:“细磨处理高铬型钒钛磁铁矿”和“以粒度较细的廉价欧控矿代替现场生产用矿”，当高铬型钒钛矿配量40%时，抗压强度分别为2475N·个-1和2005N·个-1，膨胀率为192%和16%，皆满足高炉生产要求，可实现该矿在原料中配量增加，能达到高铬型钒钛矿预期90万t/年的处理目标.     

Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

The technology of direct reduction by adding sodium carbonate (Na₂CO₃) and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na₂CO₃ reacts with gangue minerals (SiO₂ and Al₂O₃), forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na₂CO₃ also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product (metal iron powder) after briquetting can be used as the burden for steelmaking by an electric arc furnace to replace scrap steel.     

海砂矿深度还原-磁选分离实验研究

应用化学分析、扫描电镜观察和X射线衍射分析方法研究海砂矿的基础物性. 采用煤基深度还原-磁选工艺,系统考察矿粉中Fe和Ti的还原分离行为,并明确还原温度、还原时间、碳氧比、磁感应强度和磨矿粒度对还原磁选效果的影响规律. 结果表明:海砂矿主要由钛磁铁矿和钛赤铁矿组成;较优的还原分离工艺参数为还原温度1300℃、还原时间30 min、碳氧摩尔比1. 1、磁感应强度50 mT和磨矿细度-0. 074 mm质量分数86. 34%. 在此工艺条件下,可以获得金属化率94. 23%的还原产物,磁选指标分别达到精矿铁品位97. 19%和尾矿钛品位57. 94%,对应的铁、钛回收率为90. 28%和87. 22%,有效地实现海砂矿中铁钛元素的分离富集.     

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.     

Gas-based reduction of vanadium titano-magnetite concentrate: behavior and mechanisms

The reduction of vanadium titano-magnetite pellets by H₂-CO at temperatures from 850 to 1050℃ was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_H2/(V_H2 + V_CO) on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_H2/(V_H2 + V_CO). The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H₂ atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy (SEM) in conjunction with back scatter electron (BSE) imaging. The results show that the difference in thermodynamic reducing ability between H₂ and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_3-xTi_xO₄ cannot be reduced under a CO atmosphere because of the densification of particles' structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H₂ atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H₂ reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.     

Dolochar as a reductant in the reduction roasting of iron ore slimes

The present investigation examines the viability of dolochar, a sponge iron industry waste material, as a reductant in the reduction roasting of iron ore slimes, which are another waste generated by iron ore beneficiation plants. Under statistically determined optimum conditions, which include a temperature of 900℃, a reductant-to-feed mass ratio of 0.35, and a reduction time of 30-45 min, the roasted mass, after being subjected to low-intensity magnetic separation, yielded an iron ore concentrate of approximately 64wt% Fe at a mass recovery of approximately 71% from the feed iron ore slime assaying 56.2wt% Fe. X-ray diffraction analyses indicated that the magnetic products contain magnetite and hematite as the major phases, whereas the nonmagnetic fractions contain quartz and hematite.     

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.     

提钒尾渣碳热还原过程实验

在碳热还原反应热力学分析的基础上,通过球团还原焙烧实验,并结合物相分析和成分分析,对含铬提钒尾渣中金属氧化物的碳热还原过程进行了系统研究。实验结果表明,在不同的还原温度下,铁、铬、钒、锰、钛等有价金属氧化物展现出不同的还原反应特征和富集迁移规律。     

Influence of microwave treatment on grinding and dissociation characteristics of vanadium titano-magnetite

The effect of microwave treatment on the grinding and dissociation characteristics of vanadium titano-magnetite(VTM) ore were investigated using scanning electron microscopy(SEM), nitrogen absorption measurements, particle size distribution measurements, X-ray diffraction(XRD) analysis, Fourier transform infrared(FT-IR) spectroscopic analysis, and magnetic separation. SEM analysis showed that microfractures appeared in the microwave-treated VTM, which is attributed to the microwaves' selective heating characteristic and the differential expansion between minerals and gangues. Nitrogen absorption showed that the microfractures were more pronounced when the microwave heating time was increased. Particle size distribution analysis showed that microwave treatment could improve the grindability of the VTM, thus increasing the weight percent of the fine-ground product. The increase in grindability was more significant with prolonged heating time. Moreover, the particle size distribution of the fine-ground product changed only slightly after the microwave treatment. XRD analysis showed that the crystallinity of the microwave-treated VTM increased with increasing microwave heating time. The magnetic separation tests revealed that the separation efficiency increased as a result of the intergranular fractures generated by microwave treatment. The Fe grade of the magnetic fraction of microwave-treated VTM was 1.72% higher than that of the raw ore. We concluded that the microwave treatment was beneficial, especially for the mineral processing characteristics.     

Utilization of waste polyethylene terephthalate as a reducing agent in the reduction of iron ore composite pellets

The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate (PET), because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450°C for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron (iron nuggets) were reduction at 1450°C for 10 min using composite pellets containing 60% PET and 40% coke.     

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.     

强磁场对球墨铸铁退火处理的影响

研究了强磁场对退火处理球墨铸铁力学性能以及渗碳体分解、碳扩散的影响．在平行试样方向上施加强磁场进行退火处理后，球铁的拉伸强度、硬度降低．延伸率、断面收缩率升高．SEM分析表明，施加强磁场能够显著地提高渗碳体分解和碳扩散的速度．磁化力F是加速渗碳体溶解和碳扩散的驱动力，通过推导可以得出单位体积力F的表达式。