Effect of B2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.

Effect of nickel oxide additive on smelting mechanism of chromium-bearing vanadium titanomagnetite pellets

The effect of nickel oxide additive on the smelting behaviors of chromium-bearing vanadium titanomagnetite pellets(CVTP)was investigated while analyzing the transfer behavior of nickel in iron and slag.The results show that when NiO added to CVTP increases from 0 to 6 wt.%,softening start temperature increases from 1148 to 1212℃,and the softening end temperature increases from 1280 to 1334℃;the melting start temperature increases from 1318 to 1377℃,and the dripping temperature decreases from 1558 to 1521℃.The pig iron comprises a compound of Fe-Ni-C.The slag structure depolymerizes with increasing nickel addition.The softening-melting behaviors of CVTP,the reduction of nickel into pig iron,and the depolymerization of slag structure indicate the feasibility of producing nickel-iron alloy through the blast furnace process.

Effect of Cr2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets(CVTP)with Cr2O3 addition were studied,and the reduction swelling index(RSI)and compressive strength(CS)of the reduced CVTP with simulated coke oven gas(COG)injection were investigated.The results showed that the CS of the CVTP decreases and the porosity of the CVTP increases with increasing amount of Cr2O3 added.The Cr2O3 mainly exists in the form of(Cr,Fe)2O3 solid solution in the CVTP and as Fe-Cr in the reduced CVTP.The CS of the reduced CVTP increases and the RSI of the reduced CVTP decreases with increasing amount of Cr2O3 added.The limited aggregation and diffusion of metallic iron contribute to the formation of dense lamellar crystals,which leads to the slight decrease for reduction swelling behavior of reduced CVTP.This work provides a theoretical and technical basis for the utilization of CVTP and other Cr-bearing ores such as chromite with COG recycling technology.

Effects of smelting parameters on the slag/metal separation behaviors of Hongge vanadium-bearing titanomagnetite metallized pellets obtained from the gas-based direct reduction process

Smelting separations of Hongge vanadium-bearing titanomagnetite metallized pellets（HVTMP）prepared by gas-based direct reduction were investigated,and the effects of smelting parameters on the slag/metal separation behaviors were analyzed.Relevant mechanisms were elucidated using X-ray diffraction analysis,FACTSAGE 7.0 calculations,and scanning electron microscopy observations.The results show that,when the smelting temperature,time,and C/O ratio are increased,the recoveries of V and Cr of HVTMP in pig iron are improved,the recovery of Fe initially increases and subsequently decreases,and the recovery of Ti O_2 in slag decreases.When the smelting Ca O/Si O_2 ratio is increased,the recoveries of Fe,V,and Cr in pig iron increase and the recovery of Ti O_2 in slag initially increases and subsequently decreases.The appropriate smelting separation parameters for HVTMP are as follows：smelting temperature of 1873 K;smelting time of 30–50 min;C/O ratio of 1.25;and Ca O/Si O_2 ratio of 0.50.With these optimized parameters（smelting time：30 min）,the recoveries of Fe,V,Cr,and Ti O_2 are 99.5%,91.24%,92.41%,and 94.86%,respectively.

Reduction behavior and mechanism of Hongge vanadium titanomagnetite pellets by gas mixture of H2 and CO

Hongge vanadium titanomagnetite（HVTM）pellets were reduced by H2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ（H2）toφ（CO）,and pellet size on the reduction of HVTM pellets were evaluated in detail and the reduction reaction kinetics was investigated.The results show that both the reduction degree and reduction rate can be improved with increasing the reduction temperature and the H2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050℃,ratio ofφ（H2）toφ（CO）of 2.5,and pellet diameter in the range of 8-11 mm.Under these conditions（pellet diameter of 11mm）,final reduction degree of 95.51% is achieved.The X-ray diffraction（XRD）pattern shows that the main phases of final reduced pellets under these conditions（pellet diameter of 11 mm）are reduced iron and rutile.The peak intensity of reduced iron increases obviously with the increase in the reduction temperature.Besides,relatively high reduction temperature promotes the migration and coarsening of metallic iron particles and improves the distribution of vanadium and chromium in the reduced iron,which is conducive to subsequent melting separation.At the early stage,the reduction process is controlled by interfacial chemical reaction and the apparent activation energy is 60.78kJ/mol.The reduction process is controlled by both interfacial chemical reaction and internal diffusion at the final stage,and the apparent activation energy is 30.54kJ/mol.

Influences of Technological Parameters on Smelting-separation Process for Metallized Pellets of Vanadium-bearing Titanomagnetite Concentrates

The smelting-separation process for metallized pellets of vanadium-bearing titanomagnetite concentrates was studied.The influences of smelting temperature,smelting time,and the basicity of the metallized pellet on vanadium and iron recovery were investigated.The characteristics of titanium slag were analyzed using X-ray diffraction,energy dispersive spectroscopy,and mineralographic microscopic analysis.The results demonstrate that appropriate increases in smelting temperature and smelting time can improve the vanadium and iron recovery from metallized pellets and are beneficial for the slag-iron separation.Although increasing the basicity of the metallized pellet can considerably improve the vanadium and iron recovery,the TiO;grade of titanium slag was decreased.Under the optimal conditions,90.17% of vanadium and 92.98% of iron in the metallized pellet were recovered,and the TiO;grade of titanium slag was 55.01%.It was found that anosovite,augite,spinel,glassiness,and metallic iron were the main mineral phases of the titanium slag.

废钛基催化剂与钒钛磁铁矿制备含钛球团性能对比

钢铁企业烟气脱硝废催化剂(危废)产生量逐年增加,加强对此类废催化剂的有效处置与利用已成为行业急需解决的关键共性难题.本研究首次提出了将废催化剂添加到球团原料中制备含钛球团利用的新路径.将含废催化剂球团和市场普通含钛球团的制备过程及冶金性能进行对比研究.结果表明:球团原料中添加质量分数5.0%的废催化剂可以显著提高生球综合性能指标,且明显优于以钒钛磁铁矿制备的普通含钛球团.球团焙烧后,含废催化剂球团平均抗压强度为3083 N,高于普通含钛球团的2630 N.含废催化剂球团固结机理表明,废催化剂中TiO_(2)与铁氧化物反应形成Fe_(2)TiO_(5)相粘结,部分未反应TiO_(2)会降低球团抗压强度.两种含钛球团冶金性能与普通氧化球团基本相同,说明含废催化剂球团可以用于高炉护炉冶炼使用.本研究有望为钢铁企业烟气脱硝产生的废催化剂在企业内部资源化利用提供新思路.

钒钛磁铁精矿铁钒钛综合利用新流程

对攀西地区太和铁矿所产的钒钛磁铁精矿，采用冷固球团直接还原—磨矿磁选的新流程成功实现了Ｆｅ／Ｖ、Ｔｉ的有效分离。还原前铁精矿品位为ＴＦｅ５２．４７％，ＴｉＯ２１３．４２％，Ｖ２Ｏ５０．５９５％，经还原—分选后，磁性产物品位为ＴＦｅ９１．２５％（ηＦｅ９８．６３％）、ＴｉＯ２４．２１％，Ｖ２Ｏ５０．２２％，铁回收率为９２．２４％，经压团后可作为电炉炼钢的优质炉料；非磁性物品位ＴＦｅ１６．３５％、ＴｉＯ２４５．７４％、Ｖ２Ｏ５１．９４％，Ｖ２Ｏ５及ＴｉＯ２回收率分别为８２．６５％和８０．８８％，可作为提钒钛的优质原料或直接作为钛精矿销售，钒钛回收率分别比传统长流程提高１８％和８０％。实现Ｆｅ／Ｖ、Ｔｉ有效分离的关键在于采用冷固球团直接还原专利技术及球团内添加高效添加剂。

钒钛磁铁矿直接还原试验研究

在热力学分析的基础上研究了实验室条件下钒钛磁铁矿配煤直接还原的特点,考察了还原机理及还原温度、反应时间和配碳量对金属化率的影响.结果表明:采用直接还原可使钒钛磁铁矿中铁的氧化物优先还原为金属铁,钛仍以氧化物的形态存在;随着温度升高,球团金属化率呈上升趋势,且上升趋势随之减缓;在xC/xO=0.9∶1时,延长反应时间金属化率增加,但反应时间过长金属铁会被再氧化,反应时间控制在20 min为宜;在xC/xO=1.1∶1时,40 min内未出现再氧化现象;低配碳(xC/xO=0.8∶1)时,球团的金属化率随还原时间、还原温度的增加而增加,1 300℃下还原10 min后金属化率即达到了90%以上.

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 。

酸性护炉球团矿焙烧工艺及固结机理

研究了新型炉料酸性含钛护炉球团矿的焙烧工艺及固结机理 ,结果表明 :利用钒钛磁铁精矿和普通磁铁精矿的混合矿在预热和焙烧条件分别为 95 0℃ ,15min和 12 0 0℃ ,15min时制取的酸性含钛护炉氧化球团矿 ,其品位为TFe 5 8 5 6 %、TiO2 7 89% ,机械强度为 3 12 7N/个 ,主要冶金性能指标为RI 70 8% ,RDI-3 157 2 9% ,SI 15 2 7% ,软熔温度区间为 10 80～ 1170℃ ,可满足大中型高炉的冶炼和护炉要求 ;固结机理为Fe2 O3 再结晶和固相扩散固结 ,与普通铁矿氧化球团相同 .本工艺不仅有利于延长高炉寿命和调整炉料结构 ,而且也为合理利用钒钛磁铁矿开辟了有效途径 .

钒钛磁铁矿煤球团还原过程挥发分的作用

为研究钒钛磁铁矿-煤球团还原过程中挥发分作用,开展了N2气氛下分层试样与两类球团非等温热重还原实验。试样的还原度由失重测定。结果发现,煤粉中的挥发分于400℃左右开始挥发。钒钛磁铁矿-非焦煤球团还原过程非常复杂,可分为四个阶段:挥发分挥发产生CO、H2还原球团、挥发分挥发的CO、H2及其碳氢化合物分解产生的C、H2与固体C共同作用还原球团、C经由气化反应媒介作用还原球团、C直接还原球团。挥发分的挥发能提高球团的气孔率和还原性,但影响较小。分析表明,在四个还原阶段中,C的直接还原作用对球团的还原影响最强,球团的还原度提高率可达0.1748%·℃-1。

两种铁精粉在球团生产中的应用

针对球团精矿紧缺问题,为拓宽铁矿粉资源,降低原料成本,进行了球团配加菲律宾精粉、钒钛精粉的试验研究。通过造球性能、焙烧性能及冶金性能的测定,结果表明加入部分菲律宾精粉、钒钛精粉是可行的。

钒钛磁铁精矿含碳球团直接还原工艺分析

采用煤基直接还原技术研究了钒钛磁铁矿含碳球团直接还原工艺,考察了还原工艺条件及硼砂添加量对球团金属化率的影响,并通过对不同温度下所得还原产物进行XRD分析,得出了钒钛磁铁矿直接还原过程的相变历程。研究结果表明,适当提高还原温度、配碳比和反应时间均有利于提高球团金属化率。在自然碱度下,还原温度1 300℃、还原时间30 min、C/O=1.4时,金属化率达到96%。向含碳球团中添加适量硼砂,可以促进钒钛磁铁矿的还原。XRD分析结果表明,铁氧化物主要经历Fe_2O_3→Fe_3O_4→FeO→Fe的还原过程,而钛氧化物主要经历Fe_2TiO_5→Fe_2TiO_4→FeTiO_3→Ti_2O_3、TiO_2、Ti_3O_5、TiO的还原过程。

碱度对全钒钛球团矿性能的影响

通过配加石灰石进行了全钒钛球团矿造球和焙烧试验,并对生球强度、爆裂温度,预热和焙烧制度对球团强度和不同碱度条件下成品球团抗压强度、冶金性能和微观形貌进行了分析,研究碱度对全钒钛球团性能的影响规律。结果表明,碱度由0.11逐渐增大至1.10,生球落下强度先升高后降低、抗压强度先显著升高后逐渐稳定、爆裂温度逐渐降低,预热球团抗压强度逐渐降低,成品球团抗压强度先升高后逐渐降低,预热和焙烧温度对不同碱度条件下的全钒钛球团矿抗压强度影响较大,结合试验结果和现场生产实践,全钒钛球团矿适宜的碱度为0.5~0.7,预热温度为950℃,焙烧温度为1 250℃;随着球团矿碱度逐渐升高,中温还原度和还原膨胀指数逐渐升高,软化开始温度基本不变,软化结束温度逐渐降低,软化区间逐渐减小,滴落开始温度略微降低,软熔区间逐渐变窄,高温冶金性能逐渐改善;同时随着碱度增加,球团矿中硅酸盐、铁酸盐和钙钛矿等液相生成逐渐增多,在碱度小于0.7时液相起到了强化固结效果,且石灰石分解排出CO_(2)气体的同时增加了预热球的孔隙率,抑制了同心裂纹的形成,提高了抗压强度,但随着碱度进一步提高,液相增多后,阻碍了赤铁矿的固相固结并增加了细密孔洞形成,劣化了球团强度,导致球团矿抗压强度逐渐降低。

高铬型钒钛磁铁矿内配碳钠基碱性球团制备

为探究高铬型钒钛磁铁矿内配碳钠基碱性球团的性能,开展了内配碳碱性球团制备工艺参数优化的试验研究。首先通过单因素试验讨论加水量、成球压力、黏结剂加入量、Na_(2)O加入量和配碳量对球团落下强度的影响;然后采用正交试验结合极差分析和方差分析确定影响球团落下强度的主次因素和最优工艺参数组合;最后在最优工艺参数组合条件下进行球团高温热裂性、转鼓指数和膨胀率测试。研究结果发现,球团制备的最优工艺参数组合为加水量6%、成球压力10 MPa、黏结剂加入量0.4%、Na_(2)O加入量1.2、配碳量1.2;影响球团性能的主次因素依次为成球压力、配碳量、Na_(2)O加入量、加水量、黏结剂加入量。在最优参数组合条件下,干球团在950、1050、1150、1250℃下的高温热裂性分别为15%、20%、25%、35%,转鼓指数分别为82.3%、77.6%、72.8%、63.4%,膨胀率分别为108%、120%、106%、70%。上述球团制备工艺参数优化的研究结果可为后续高铬型钒钛磁铁矿碱性球团制备以及非高炉工艺回收高铬型钒钛磁铁矿中有价金属提供工艺参考。

高铬型钒钛铁精矿球团氧化钠化焙烧-水浸提钒研究

在氧化钠化焙烧过程热力学分析的基础上,以高铬型钒钛铁精矿为原料,研究了焙烧温度和碳酸钠配比对焙烧熟料物相组成和钒浸出率的影响规律。采用 X 射线衍射(XRD)分析焙烧熟料的物相组成;使用 X 射线光电子能谱(XPS)、扫描电镜(SEM)和电感耦合等离子体发射光谱仪(ICP)分析了特定样品的价态、形貌、结构和元素含量。焙烧熟料 XRD 分析表明,FeTiO_(3)与碳酸钠的反应是氧化过程和钠化过程同时进行,在反应进行不充分时,出现中间产物 Na_(0.75)Fe_(0.75)Ti_(0.25)O_(2);碳酸钠配比对焙烧熟料物相组成影响较大,随着碳酸钠配比的增加,焙烧熟料中未被氧化的 Fe_(3)O_(4)峰强显著增强。提钒实验结果表明,适当提高焙烧温度和碳酸钠配比有助于钒浸出率的提高,但是过高的焙烧温度和碳酸钠配比,钒的浸出率明显下降;在焙烧温度 1100 ℃,碳酸钠配比为 15% 的条件下,V_(2)O_(5),Cr_(2)O_(3)和 TiO_(2)的浸出率分别为 89.70%,55.85%和 11.54%。XPS 分析表明,钒元素的氧化较为充分,铁和铬元素仍有部分未被氧化为高价态。此外,SEM 图像显示,焙烧熟料和浸出渣颗粒均存在致密状和疏松状两种形态,铁元素在致密状中分布更加集中,而钒、钛和钠元素在疏松状中聚集。

电炉熔分还原制取高钒生铁所用还原剂的优化

针对钒钛磁铁矿金属化球团电炉熔分还原过程中出现泡沫渣的问题,对常用还原剂焦炭、硅、铝、电石等进行了热力学分析,结果表明采用电石作还原剂对消除泡沫渣是有利的。运用FACTSage软件计算了电石的还原效果,并分析了温度、碱度、还原剂量及金属化率对铁液中各元素质量分数的影响。将电石与焦炭的还原效果进行了对比,提出了分阶段应用焦炭及电石作为还原剂的工艺构想。

钒钛磁铁矿含碳球团的还原历程

为实现钒钛磁铁矿资源的高效合理利用,对钒钛磁铁矿含碳球团的还原过程进行了解析,初步建立了动力学控制方程;利用差热分析方法对钒钛磁铁矿的还原熔分历程进行了分析与讨论,认为钒钛磁铁矿的还原可分为煤的氧化、钒钛磁铁矿的直接还原、借助碳的气化反应的直接还原和还原结束4个部分;以攀枝花钒钛磁铁矿为原料,煤为还原剂,考察了反应时间和温度对含碳球团还原度的影响,确定固体产物层内扩散是钒钛磁铁矿含碳球团直接还原反应的控制性环节,计算出其表观活化能为112.13 kJ/mol。

钒钛铁精矿非自然碱度含碳球团高温固态还原试验

为了研究钒钛铁精矿非自然碱度含碳球团高温固态还原规律,以钒钛铁精矿为原料,在实验室条件下,探索了还原温度、还原时间、碱度和配煤比对钒钛铁精矿非自然碱度含碳球团高温固态还原的影响,采用X射线衍射仪测定了金属化球团的物相组成。研究结果表明,适当提高还原温度、延长还原时间、提高碱度和配煤比均可促使球团的金属化率提高;对于钒钛铁精矿金属化球团物相组成,在还原温度高于1 400℃时,金属化球团中出现大量碳氮化钛,碱度的提高有利于抑制还原产物中碳氮化钛的生成,配煤比的增加促进了碳氮化钛的生成。从后续熔分工序对钒钛铁精矿金属化球团质量要求的角度来说,高温固态还原的适宜条件,还原温度为1 350℃,碱度为1.0,还原时间为30 min,配煤比为1.3,在此条件下,球团的金属化率为93.72%,金属化球团碳质量分数为6.08%,主要物相为黑钛石和金属铁。