Recovery of Ferric Oxide from Bayer Red Mud by Reduction Roasting-Magnetic Separation Process

A great amount of red mud generated from alumina production by Bayer process was considered as a low-grade iron ore with a grade of 5wt% to 30wt% iron.We adopted the reduction roastingmagnetic separation process to recover ferric oxide from red mud.The red mud samples were processed by reduction roasting,grinding and magnetic separating respectively.The effects of different parameters on the recovery rate of iron were studied in detail.The optimum techqicalparameters were proposed with 700 ℃roasting for 20 min,as 50wt% carbon and 4wt% additive were added.The experimentalresults indicated that the iron recovery and the grade of totaliron were 91% and 60%,respectively.A novelprocess is applicable to recover ferric oxide from the red mud waste fines.

Selective separation of iron and scandium from Bayer Sc-bearing red mud

In this study,we investigated the separation of iron and scandium from Sc-bearing red mud.The red mud object of our study contained 31.11 wt%total iron(TFe),0.0045 wt%Sc,hematite(Fe_(2)O_(3))and ferrosilite(FeO·SiO_(2))as the main Fe-bearing minerals.The Sc-bearing red mud was treated by a novel deep reduction roasting and magnetic separation process that includes the addition of coke and CaO to extract Fe and enriching Sc from the Sc-bearing red mud.The addition of coke and CaO enhances the transformation of hematite(Fe_(2)O_(3))to metallic iron(Fe~0)and magnetite(Fe_(3)O_(4))as well as the transformation of ferrosilite into metallic iron(Fe~0).The test results show that utilizing the new process a Fe concentrate with a TFe content of 81.22 wt%and Fe recovery of 92.96%was obtained.Furthermore,magnetic separation tailings with Sc content of 0.0062 wt%and Sc recovery of 98.65%were also obtained.The test results were achieved under the following process conditions:roasting temperature of 1373 K,roasting time of 45 min,calcium oxide dosage of 20 wt%,coke dosage of 25 wt%,grinding fineness of90%<0.04 mm,and magnetic field intensity of 0.24 T.The major minerals in the Fe concentrate are metallic iron(Fe~0)and magnetite(Fe_(3)O_(4)).The main minerals in the magnetic separation tailings with a low TFe content of 2.62%are CaO·SiO_(2),Na_(2)O·SiO_(2),FeO·SiO_(2),Ca_(3)Fe_(2)Si_(3)O_(12),CaAl_(2)SiO_6 and CaFe(SiO_(3))_(2).

高铁低硅赤泥钠化还原的物相转变及铁分离特性

高温焙烧赤泥可实现铁、铝、硅等元素的形态转化,使其易于分离回收,但高铁低硅赤泥的钠化还原焙烧反应差异性及机制研究却少有报道。本文采用X射线衍射分析,考察了还原温度、碳酸钠用量、还原时间等对高铁低硅赤泥还原焙烧的矿相转化及微结构影响,分析了反应后的铁磁化分离差异性。结果表明:还原焙烧中钠与铝、硅元素结合形成铝钠硅酸盐,有效破坏了铁、铝元素的紧密结构;赤铁矿、铝针铁矿大部分转为磁铁矿和浮氏体,促进了铁氧化物还原;低熔点含钠固溶体降低了金属铁质点迁移阻力,加速了铁晶粒的长大。基于铁铝结构崩解及粗晶粒金属铁的生成,焙烧产物经磨矿-磁选后,获得了全铁含量为90.41%、Fe回收率为93.08%的铁回收指标。

高铁赤泥钙化还原过程液相生成抑制机理

高铁赤泥中赋存大量铁资源难以回收利用,钙化还原—磨选方法可实现赤泥中铁、铝组分的高效分离。针对高铁赤泥钙化还原过程中易形成液相,导致物料熔化和设备黏结的问题,本文提出分段式钙化还原—磨选技术路线,研究不同温度制度下,高铁赤泥钙化还原产物的形态、金属化率、微观结构、金属铁晶粒的生长规律和相关磨选指标。结果表明:采用分段钙化还原焙烧,可在低温阶段完成铁氧化物还原至金属铁和钙铝化合物形成的反应过程,在高温阶段完成金属铁颗粒的聚集长大过程,将低熔点物形成和高温焙烧分离进行,抑制液相生成。采用第一段1 125℃焙烧30 min、第二段1 200℃焙烧40 min的分段焙烧制度,还原过程无明显液相生成,金属铁颗粒的平均粒度达到21.52μm。还原产物经磨选后,所获得的还原铁粉TFe质量分数和Fe回收率分别达到92.84%和78.68%。本文研究成果可为高铁赤泥的资源化利用提供理论依据。

赤泥、粉煤灰、磷石膏协同高温烧结回收铁铝试验研究

赤泥(RM)、粉煤灰(FA)、磷石膏(PG)这3种固废具有产生量大、利用率低的特点,长期堆存会对水资源、土壤、空气等产生严重影响。本文提出用磷石膏代替碱石灰CaO,采用高温烧结-碱浸提铝-磁选提铁工艺协同处理3种固废回收铝、铁,并考察烧结工序工艺条件对铝、铁回收率的影响,得到以下主要结论。在烧结温度1100℃、保温时间30 min、钙比2.0条件下,铁回收率达到79.2%、铁品位达到74.5%、铝溶出率达到75.9%;升高烧结温度有利于铁、铝回收,但温度高于1100℃时熟料会出现粘黏阻碍铝的溶出;保温时间对铝铁回收影响较小;CaO与Na_(2)CO_(3)有助于激活粉煤灰中莫来石的活性,提高铝回收率;磷石膏添加过量时高温下会生成Fe_(3)Ti_(3)O_(10)、Ca_(3)Fe_(15)O_(25),导致铁品位和铁回收率降低。采用本试验工艺,每消纳10 g赤泥、6.5 g粉煤灰、15 g磷石膏,可回收75.9%的铝和3 g铁精矿,而且生产中可实现碱循环,同时生成的副产品2CaO·SiO_(2)可用来制备硫铝酸盐水泥,整个工艺流程实现了3种固废绿色协同消纳,有效实现了资源的综合利用。

拜耳法赤泥梯级分离铁铝钛制备磷酸铁的工艺研究

该文结合湿法酸浸赤泥与均相沉淀法制备磷酸铁,提出了赤泥中的铁(Fe)、铝(Al)、钛(Ti)梯级分离工艺。首先对赤泥进行碱焙烧-水淬,以焙烧温度900℃、焙烧时间90 min、纯碱/赤泥投料比为0.5∶1进行碱焙烧后,水淬焙烧产物Al的水淬浸出率达69.91%。其次进行水淬渣的酸浸,得到富含Fe、Al、Ti的酸浸液,在浸出时间1.5 h、浸出温度120℃、硫酸浓度6.0 mol/L、固液比为1∶6的最佳工艺条件下,Fe、Al、Ti浸出率分别达到90.43%、69.48%、95.63%;再次将酸浸液高温氧化水解回收Ti,Ti的回收率达76.79%,Fe组分损失率仅4.9%。而后用氟化钠分离酸浸液中的Al元素制备冰晶石,在F/Al摩尔比为1∶6、初始pH为1.0、反应温度25℃、搅拌反应1 h的条件下,Al的回收率达98.45%,制得纯度较高的冰晶石(Na3AlF6)。最后用均相沉淀制备磷酸铁,在投料Fe/P摩尔比为1∶1.1、双氧水过量1.2倍、反应pH为1.8、反应温度90℃、反应时间4 h的最佳工艺条件下制备的磷酸铁晶形良好,符合标准质量要求。该工艺流程简单,通过梯级分离实现了铁、铝、钛元素的回收利用,为拜耳法赤泥资源化利用提供了新思路。

赤泥选铁后尾矿管道输送试验研究

针对赤泥选铁后尾矿进行管道输送相关的一系列试验研究。进行了流变特性研究,结果表明此类浆体属于宾汉体模型,最佳输送浓度为35%;进行了敷设角度试验,此类浆体的最大敷设角度应不大于8.5°;进行了临界沉积速度计算,35%浓度时,浆体在内径203和255 mm两种管径的临界沉积速度分别为0.982和1.039 m/s;进行了内径203和255 mm的两种规格管道的环管试验,结果表明浆体摩阻在相同管径下,随浆体浓度的增大而增加,浆体摩阻在同种浓度下,管道内径越大,摩阻越小。

赤泥磁化焙烧选铁技术工程应用及经济性分析

采用低温溶出处理的三水铝石型铝土矿溶出赤泥,主要以磁性较差的褐铁矿或者铝针铁矿形态存在,磁选效果不佳。采用磁化焙烧-湿法磁选生产工艺对此类赤泥进行处理,可达到较好的磁选效果,品位为56%的铁精矿,产率可达到31%以上。某沿海氧化铝项目拟采用磁化焙烧-湿法磁选工艺,项目总占地61975 m^(2),总投资43363万元。工程应用后每年减少干赤泥91.7万t,减少赤泥堆存库容61.3万方,每年实现利润920万元。

Modeling assessment of recovering iron from red mud by direct reduction： magnetic separation based on response surface methodology

Red mud, the waste generated during alumina production, contains iron and other valuable metals. To recover the iron efficiently from red mud, a three-factor five-level central composite design in response surface methodology was used to study the effects of process parameters, such as FC/O （the molar ratio of fixed carbon in coal to reducible oxygen of iron oxide in red mud）, reduction temperature, reduction time, and their interaction on the iron recovery rate and total iron content in magnetic product obtained from the process of direct reduction-magnetic separation. The relevant assessment model was established. The model could predict the changing rules of iron recovery rate and total iron content in the magnetic product affected by the process parameters. The results show that the iron recovery rate is significantly influenced by three factors and reduction temperature plays the most important role. The iron recovery rate and total iron content in magnetic product could be up to 98.37 and 82.52%, respectively, under the numerically optimal process parameters condition of reduction temperature of 1400 ℃, FC/O of 0.80 and reduction time of 100 min obtained by the assessment model. The predicted values are in good agreement with the experimental values.

赤泥回收铁铝资源技术研究现状及展望

赤泥作为氧化铝生产排放的强碱性固体废弃物,因其碱含量高并含有丰富的铁、铝、稀散和稀贵金属等战略金属资源而广受关注。提高赤泥中铁、铝等大宗金属资源的综合利用率,不仅能够解决赤泥大量堆存导致的生态环境污染和大量土地占用,而且能够改善我国铝土矿资源和铁矿石资源供需紧张的现状,降低我国工业发展受国际资源巨头垄断和地缘政治形势改变双重制约的铁铝资源风险。本文介绍了拜耳法赤泥的产生、理化性质以及危害,并重点从物理选矿、火法冶金和湿法冶金三个综合利用方向详细阐述了近年来国内外对于利用赤泥分离回收铁矿物和铝矿物的技术研究进展及其存在问题,同时对赤泥综合利用技术的未来发展方向提出了展望及建议。

添加剂活化赤泥磁化焙烧⁃弱磁选回收铁

为查明添加剂对赤泥磁化焙烧⁃弱磁选回收铁的影响,以某高铁高铝赤泥为研究对象,研究了焙烧、磁选制度对铁回收率的影响。结果表明,白云石和磷石膏对铁的回收无明显作用,而硫酸钠活化作用明显。较佳实验条件为:硫酸钠用量10%、焙烧温度650℃、焙烧时间90 min、总气体流量500 mL/min、CO体积分数30%、焙砂磨矿细度-0.045 mm粒级占比65%、磁场强度68.8 kA/m,此时可获得TFe品位和回收率分别为60.65%和94.01%的磁铁精矿。热力学分析结果表明,在研究温度范围内,白云石与磷石膏均有利于铁橄榄石的分解,而对铁尖晶石的分解不起作用,硫酸钠则可同时促进二者的分解。

焦硫酸钠低温焙烧法回收赤泥中的铝和铁

以焦硫酸钠为添加剂,通过低温焙烧和水浸回收赤泥中的Al和Fe,并同步实现赤泥中碱的脱除。重点考查焙烧温度、焦硫酸钠添加量及水浸条件等重要参数对Al、Fe、Na浸出的影响,并结合热力学计算、XRD、SEM、EDS等方法分析焙烧过程的反应机理。结果表明:焙烧过程中焦硫酸钠与赤泥中Al、Fe、Ca和Na等组元发生反应,分别转化为NaAl(SO_(4))_(2)·6H_(2)O、Na3Fe(SO_(4))_(3)、Na_(2)Ca(SO_(4))_(2)和Na_(2)SO_(4)。在焙烧温度300℃、焦硫酸钠添加量与理论用量的比1.1、焙烧时间90min、水浸温度60℃、液固比(mL/g)2.0、水浸时间60 min的优化条件下,Al、Fe和Na的浸出率分别为95.31%、93.34%和97.69%。溶液中的Al和Fe可通过共沉淀和碱浸进行分离,水浸渣“固碳”后,可用于建材行业。

Recovery of Iron From High-Iron Red Mud by Reduction Roasting With Adding Sodium Salt

Red mud is the waste generated during aluminum production from bauxite, containing lots of iron and other valuable metals. In order to recover iron from red mud, the technology of adding sodium carbonate—reduction roasting—magnetic separation to treat high-iron red mud was developed. The effects of sodium carbonate dosage, reduction temperature and reduction time on the qualities of final product and the phase transformations in reduction process were discussed in detail. The results showed that the final product (mass percent), assaying Fe of 90.87% and Al2O3 of 0.95% and metallization degree of 94.28% was obtained at an overall iron recovery of 95.76% under the following conditions of adding 8% sodium carbonate, reduction roasting at 1 050 ℃ for 80 min and finally magnetic separation of the reduced pellets by grinding up to 90% passing 0.074 mm at magnetic field intensity of 0.08 T. The XRD (X-ray diffraction) results indicated that the iron oxides were transformed into metallic iron. Most of aluminum mineral and silica mineral reacted with sodium carbonate during the reduction roasting and formed nonmagnetic materials.

赤泥磁化焙烧湿法选铁技术研究及工程应用经济性分析

采用低温拜耳法处理的三水铝石型铝土矿溶出赤泥,主要以磁性较差的褐铁矿或者铝针铁矿形态存在,磁性弱,磁选效果不佳。试验表明,采用磁化焙烧-湿法磁选生产工艺对此类赤泥进行处理,可达到较好的磁选效果,品位为56%的铁精矿,铁的回收率可达到62%。以某港口氧化铝项目为例,根据试验数据进行计算,采用赤泥磁化焙烧-湿法磁选生产工艺后,预计每年减排赤泥1 337 kt/a,节约赤泥堆存库容106.96万方,每年实现利润1 438.6万元。

赤泥强磁选铁预富集工艺研究

本文针对某铝业公司产生的赤泥,从实验室和工业试验两个方面研究赤泥的强磁选铁预富集工艺,结果表明:赤泥样品中可供选矿回收的主要组分铁质量分数为26.06%,通过“一粗一扫”强磁选流程,可得到TFe品位为37.80%、铁回收率为65.12%的预富集粗精矿,证明了强磁选机“一粗一扫”流程的稳定性和可靠性。

不同萃取剂从赤泥浸出液中萃取分离铁钙试验研究

研究了用P204、P507萃取分离赤泥浸出液中的铁、钙,考察了萃取剂的体积分数、水相pH、萃取温度、萃取时间和相比V_(O)/V_(A)对铁、钙萃取分离的影响,确定了2种萃取剂的最佳萃取试验条件,对比了萃取性能。结果表明:有机相组成为40%P204+60%磺化煤油时,在水相pH=1.4、萃取温度50℃、萃取时间15 min、相比V_(O)/V_(A)=1/1条件下,Fe^(3+)萃取率为94.29%,Ca^(2+)萃取率为5.07%,P204可较好萃取分离铁和钙;有机相为30%P507+70%磺化煤油时,在水相pH=2.5、萃取温度40℃、萃取时间15 min、相比V_(O)/V_(A)=3/1条件下,Fe^(3+)萃取率可达99.67%,Ca^(2+)萃取率为1.95%;P204、P507都能从赤泥浸出液中萃取分离铁、钙,相较而言,P507萃取分离性能好于P204。

硫磺还原高铁赤泥提铁

为提高高铁赤泥的综合利用率,响应国家“碳达峰”与“碳中和”的号召,提出了利用硫磺还原高铁赤泥、固相还原—磁选提铁的新方法,研究了不同的焙烧温度、配料比、焙烧时间对硫磺还原赤泥中Fe2O3效果的影响.利用XRD分析了焙烧产物的物相组成,采用湿法磁选机磁选分离出精矿和尾矿,并计算出精矿中铁的回收率.结果表明:在硫磺与高铁赤泥的配料比(即S与赤泥中Fe2O3的摩尔比)为1∶6、焙烧温度为800℃、焙烧时间为0.5 h的条件下,还原效果最佳,铁回收率高达90%.

从赤泥酸浸液中分离提取稀土试验研究

研究了用P507从赤泥酸浸液中分离提取稀土。首先用35%N235+15%TBP+50%磺化煤油萃取赤泥酸浸液中的铁,再用氧化镁浆液沉淀萃取铁后萃余液中的钛、钪、铝、稀土,稀土沉淀物经盐酸溶解后用P507萃取,最终得到高浓度氯化稀土产品。结果表明:以35%P507+65%磺化煤油为有机相萃取稀土,在常温、萃取时间1 min、萃取相比V_(a)/V_(o)=50/1条件下进行2级萃取,稀土萃取率可达94.34%;再用6 mol/L盐酸,在反萃取相比V_(o)/V_(a)=14/1、反萃取时间5 min条件下进行2级反萃取,稀土反萃取率达97.16%。该法可实现赤泥中稀土的有效分离提取。

赤泥沉降性能影响因素研究

在氧化铝生产过程中,赤泥的沉降分离是重要的一个环节,赤泥分离沉降的快慢以及分离效果直接影响着产品质量的好坏。由于溶出的浆料是铝酸钠溶液和赤泥组成的悬浮液,粒子之间存在着复杂的物理化学作用,且影响沉降分离效果的因素有很多,因此,研究氧化铝生产过程中赤泥的沉降分离效果对于生产具有重要的指导意义。本文从絮凝剂添加种类、添加量、添加方式、熟料粒度、溶液固含等方面对沉降分离效果进行了研究。

赤泥含铁矿物回收实验研究

根据拜耳法大坝赤泥的理化性质研究对赤泥中铁的回收工艺采用强磁选抛废。结果表明在磁场强度为1.5 T时,可获得含铁50.34%回收率为47.58%的铁精矿,通过对粗精矿反浮选脱硅提质,获得累计回收率为41.58%、品位为57.61%的优质铁精矿。