硫酸钠对高铁型红土镍矿中铁矿物还原的抑制机理

研究了硫酸钠对红土镍矿中铁矿物还原的抑制机理。结果发现硫酸钠能够改变铁矿物的还原历程，生成FeS和含铁的铝硅酸盐，使焙烧矿液相增加。液相的增加抑制煤的气化反应，减弱体系的还原气氛，同时抑制还原气体的扩散，对铁矿物的还原不利。 FeS和铝硅酸盐形成的液相包裹在FeO周围使其还原受到抑制，铝硅酸盐在包裹FeO的同时与其反应生成更多液相，对FeO的还原起到进一步的抑制作用。     

Effects of Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> on iron and nickel reduction in a high-iron and low-nickel laterite ore

This study investigates the reactions of Na₂SO₄ and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na₂SO₄ to SO₂ was performed with roasting up to 600℃. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na₂SO₄ reacted to produce SO₂. Na₂SO₄ reacted completely at 1000℃, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na₂SO₄ resulted in weakening of the reduction atmosphere, and the main product of Na₂SO₄ changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine.     

还原剂对高磷鲕状赤铁矿还原焙烧铁磷分离的影响

研究还原剂种类及用量对高磷鲕状赤铁矿还原焙烧铁磷分离的影响.添加脱磷剂Na2CO3,在提铁降磷的同时能降低还原铁的硫含量;还原剂用量的增加都能促进铁还原,但使用灰分和固定碳含量较高或挥发分含量较低的还原剂时,不利于降磷.焙烧产物的X射线衍射分析表明:添加脱磷剂Na2CO3时,随着还原剂用量的增加,焙烧产物中金属铁含量增加,浮氏体和石英含量降低;使用灰分含量较高的还原剂时,随其用量的增加,灰分会消耗Na2 CO3,从而减弱其对于铁还原的促进作用;还原剂用量相同时,石煤、烟煤、焦炭和褐煤所得焙烧产物中金属铁含量逐渐增加,浮氏体含量逐渐降低.总体来看,褐煤作为还原剂时铁磷分离效果最好,其次为烟煤,焦炭和石煤.     

某高磷鲕状赤铁矿磷赋存状态及还原焙烧脱磷研究

采用浸出、电渗析等试验方法研究了尼日利亚高磷鲕状赤铁矿中磷的赋存状态并采用XRD和SEM分析添加脱磷剂Na2CO3直接还原焙烧产物的特性.结果表明,含磷矿物主要是呈微细粒包裹体嵌布在铁矿物鲕粒的裂隙或孔洞中的纤磷钙铝石(CaAl3(OH)6(HPO4)(PO4))、蓝磷铝铁矿(FeAl2(PO4)2OH·6H2O)以及均匀分散在铁矿物中的磷.通过添加脱磷剂Na2CO3的还原焙烧磁选可实现高效铁磷分离.磷通过两种方式去除:一部分含磷矿物与金属铁分离,存在于脉石矿物中,通过磨矿磁选可以有效去除,一部分含磷矿物与Na2CO3反应生成溶于水的磷矿物,最终使得还原铁产品中的磷含量降低.     

煤种对钛磁铁矿直接还原-磁选钛铁分离的影响

研究了烟煤和无烟煤对海滨钛磁铁矿直接还原-磁选钛铁分离的影响机理.结果表明,在试验用量范围内,两种煤对还原铁指标的影响规律相近,煤用量低时钛磁铁矿还原不充分.随煤用量增加,被还原的金属铁越来越多,但粒度较小,与其他颗粒嵌布紧密,因此还原铁Fe品位低,Ti O2品位高,铁回收率则先提高后基本不变.所有煤用量下所得金属铁颗粒均纯净.和无烟煤相比,烟煤固定碳较低,还原气氛较弱,但灰分较高,有利于金属铁颗粒的聚集长大;因此相同用量的烟煤为还原剂时,焙烧矿中金属铁颗粒较少,但粒度较大,还原铁中Fe品位较高,铁回收率较低,Ti O2品位较低.     

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.     

Feasibility of co-reduction roasting of a saprolitic laterite ore and waste red mud

Large scale utilization is still an urgent problem for waste red mud with a high content of alkaline metal component in the future. Laterite ores especially the saprolitic laterite ore are one refractory nickel resource, the nickel and iron of which can be effectively recovered by direct reduction and magnetic separation. Alkaline metal salts were usually added to enhance reduction of laterite ores. The feasibility of co-reduction roasting of a saprolitic laterite ore and red mud was investigated. Results show that the red mud addition promoted the reduction of the saprolitic laterite ore and the iron ores in the red mud were co-reduced and recovered. By adding 35wt% red mud, the nickel grade and recovery were 4.90wt% and 95.25wt%, and the corresponding iron grade and total recovery were 71.00wt% and 93.77wt%, respectively. The X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive spectroscopy (SEM-EDS) analysis results revealed that red mud addition was helpful to increase the liquid phase and ferronickel grain growth. The chemical compositions “CaO and Na₂O” in the red mud replaced FeO to react with SiO₂ and MgSiO₃ to form augite.     

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe₂O₃→Fe₃O₄, Fe₃O₄→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO₂ content in the Fe₂O₃→Fe₃O₄ stage but is substantially greater than the CO₂ contents in the Fe₃O₄→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and Fe_xO_y reduction by CO, which are the restrictive step in the last two stages, require further study.     

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.     

高磷矿氢气还原过程的原位研究

通过原位观察的方法,研究了H2气氛、不同温度下高磷矿还原过程的矿相结构演变规律和温度对金属铁析出形态的影响。高磷矿的鲕状结构在还原过程中未被破坏掉;随着温度的提高,矿相结构的演变加快,温度较高时Fe发生明显偏聚,金属铁从赤铁矿相中加快析出。还原温度对高磷矿中金属铁的析出形态影响显著：在700℃时金属铁析出在矿石颗粒表面形成致密铁层;800℃时析出的金属铁形貌复杂化,铁层致密度下降,出现孔洞,同时有少量的短小铁晶须;900℃时铁晶须数量明显增多,同时伴随着大量多孔海绵铁的析出。因此,可以通过调节还原温度和时间,使得气基还原过程避免黏结失流,同时高效还原高磷矿。     

A pilot-scale study of selective desulfurization via urea addition in iron ore sintering

The iron ore sintering process is the main source of SO₂ emissions in the iron and steel industry. In our previous research, we proposed a novel technology for reducing SO₂ emissions in the flue gas in the iron ore sintering process by adding urea at a given distance from the sintering grate bar. In this paper, a pilot-scale experiment was carried out in a commercial sintering plant. The results showed that, compared to the SO₂ concentration in flue gas without urea addition, the SO₂ concentration decreased substantially from 694.2 to 108.0 mg/m3 when 0.10wt% urea was added. NH₃ decomposed by urea reacted with SO₂ to produce (NH₄)₂SO₄, decreasing the SO₂ concentration in the flue gas.     

Oxide coating mechanism during fluidized bed reduction: solid-state reaction characteristics between iron ore particles and MgO

Experiments on the solid-state reaction between iron ore particles and MgO were performed to investigate the coating mechanism of MgO on the iron ore particles’ surface during fluidized bed reduction. MgO powders and iron ore particles were mixed and compressed into briquettes and, subsequently, roasted at different temperatures and for different time periods. A Mg-containing layer was observed on the outer edge of the iron ore particles when the roasting temperature was greater than 1173 K. The concentration of Fe in the Mg-containing layer was evenly distributed and was approximately 10wt%, regardless of the temperature change. Boundary layers of Mg and Fe were observed outside of the iron ore particles. The change in concentration of Fe in the boundary layers was simulated using a gas–solid diffusion model, and the diffusion coefficients of Fe and Mg in these layers at different temperatures were calculated. The diffusion activation energies of Fe and Mg in the boundary layers in these experiments were evaluated to be approximately 176 and 172 kJ/mol, respectively.     

鲕状赤铁矿悬浮焙烧的磁性研究

针对鄂西某鲕状赤铁矿进行悬浮焙烧研究,并采用振动样品磁强计、X射线衍射分析仪、穆斯堡尔谱仪分析还原温度、还原时间、氧化温度、颗粒粒度对焙烧物料磁性和物相组成的影响规律.结果表明:铁矿石经悬浮焙烧后磁性明显增强,且焙烧物料磁性与强磁性铁矿物的含量呈正比.当还原温度为550~650℃时,还原物料的磁化强度和比磁化率随还原温度的升高而升高,超过700℃后则随之降低.延长还原时间可提高还原物料的磁化强度和比磁化率.焙烧物料中γ-Fe2O3含量随氧化温度升高而增加,在氧化温度为350℃时物料中γ-Fe2O3的含量达到最大值.当焙烧物料颗粒粒度小于15μm时,颗粒的磁化强度和比磁化率随之降低,而剩磁和矫顽力则随之增加.     

铬铁矿的还原焙烧与磁选分离

以南非铬铁矿为原料,以潞安煤粉为还原剂,进行了铬铁矿粉还原焙烧与磁选分离实验。借助扫描电镜、能谱分析和X射线衍射分析,对碳热还原和磁选分离过程中的物相变化进行了系统研究。实验发现,当温度低于1 200℃时,铬铁矿仅发生少量铁氧化物的还原,当温度高于1 300℃时,铬铁矿中铬氧化物开始被还原成碳化铬。随着还原反应的不断进行,铬铁尖晶石结构逐渐发生转变并被破坏。在本实验条件下,铬铁矿较为适宜的预处理温度为1 200℃,此温度下的还原产物磁选后,磁选产物几乎全部为金属铁,磁选所得尾渣的除铁率为46%,铬的收得率为80%,w(Cr2O3)/w(ΣFe O)值高达3.75。研究工作对于铬铁矿预处理工艺的设计开发及低品位铬铁矿的综合利用具有理论指导意义。     

（光）助电-Fenton降解有机染料罗丹明B

以高纯石墨电极为阴极,铁片为阳极,Na2SO4溶液为支持电解质,通过阳极氧化提供Fe^2＋/Fe^3＋和阴极还原溶解氧转化为H2O2而形成Fenton体系,以降解有机染料罗丹明B（RhodamineB,RhB）为探针反应,研究了外加电压、铁电极面积（电荷密度）、极间距、电解质溶液浓度及外加紫外光照射（300 nm〈λ〈380n m）等因素对RhB降解反应的影响.结果表明：外加电压为7 V,铁片面积为3 cm^2（电荷密度为0.045 A/cm^2）,电极之间距离为4 cm,Na2SO4质量浓度为10 g/L时,反应100 min后RhB褪色完全.采用过氧化物酶催化反应吸光光度法和苯甲酸荧光分析法分别跟踪测定RhB降解反应过程中H2O2和羟基自由基（·OH）,表明RhB降解过程涉及·OH历程.通过分析测定RhB降解过程TOC变化和红外光谱分析,表明染料降解反应不仅仅为简单褪色而且深度氧化,180 min矿化率为73.0%.     

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%.     

铁酸锌气体还原的热力学分析

根据热力学原理,计算并分析了含锌冶金粉尘中的重要成分ZnFe2 O4在CO- CO2气体还原过程中的热力学行为. ZnFe2 O4的气体还原遵循逐级还原规律,且ZnFe2 O4很容易被CO还原到ZnO和Fe3 O4.较高温度条件下,ZnO的气体还原易于FeO的还原.随着反应温度升高,锌完全反应和挥发所需要的CO含量不断降低,当反应温度从1100 K升高到1400 K时所需的CO体积分数由0.4降低到0.01以下.要达到还原分离金属锌的目的,不必将铁氧化物还原到金属铁,而只需将铁氧化物还原到Fe3 O4或FeO,同时满足锌的还原条件即可.在高炉炉身中上部,由于发生锌的还原反应和内部循环,给高炉生产带来危害,因此应减少和控制高炉的锌负荷.     

焙烧温度对氧化球团性质及其气基直接还原过程的影响

考查焙烧温度对氧化球团抗压强度、孔隙率、Fe3O4含量及显微结构等性质的影响,研究不同焙烧温度下球团的还原行为,计算其还原过程动力学并确定还原过程的限制性环节。研究结果表明:随着焙烧温度的升高,氧化球团抗压强度增大,晶粒间互联及渣相增多,球团内Fe3O4含量及孔隙率则明显降低;在1 200℃焙烧时球团还原最快,其次为1 150℃和1 250℃,最慢的是于1 100℃焙烧球团;在1 100,1 150和1 200℃焙烧球团还原过程受界面化学反应控制,而1 250℃焙烧球团在还原过程前期受界面化学反应控制,后期受内扩散控制。     

低配碳比含碳球团直接还原的实验研究

根据低配碳比含碳球团还原熔分工艺制备粒铁的技术思想,对低配碳比含碳球团的直接还原进行实验研究.结果表明,这种低配碳比的含碳球团还原速度较快,还原反应进行了10 min时表观还原度为84%,20min时表观还原度可达88%;继续延长反应时间,球团表层还原得到的少量金属铁会再次被氧化成FeO.还原反应结束后,球团内仍存在少量尚未还原的FeO,它们与脉石中的SiO2形成低熔点的铁橄榄石,有利于工艺后期渣铁的熔化及分离.     

不同还原度铁氧化物球团在微波场中的升温及还原行为

为深入了解氧化球团在微波竖炉中的升温以及煤基直接还原行为,实验采用铁精矿氧化球团作为基础原料,在气体还原剂条件下进行预还原,通过控制还原时间得到不同还原度铁氧化物球团,并从不同还原度铁氧化物球团的结构以及性能出发,研究它们在微波场中的升温性能及其还原变化.电磁性能测试结果表明,球团中的铁及其氧化物在微波场中的升温速度从快到慢依次为:Fe3O4,Fe2O3,Fe,FeO.微波加热还原结果分析及矿相结构观察显示,Fe2O3的深还原时间较长,物相多重转变,造成过程温度和还原气氛跟不上氧化物的还原反应速度;Fe3O4阶段升温速度快,结构松散,有助于进一步的还原,但进入浮士体(FeO的固溶体)阶段后孔隙率降低,升温速度骤降,造成还原的困难;在还原度达到66.90％时,表层以金属铁相为主,孔洞发达,吸波性能强,在气化反应有效进行的条件下,球团将会实现快速还原.