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钒钛磁铁矿精矿弱还原-低酸浸出制备钛富集料的工艺研究
FAIZA SAFDAR
Thesis Advisor郑诗礼
2020-07-01
Degree Grantor中国科学院大学
Degree Name硕士
Degree Discipline应用化学
Keyword钒钛磁铁矿(Vtm),碳还原, 弱酸浸出,Fecl3浸出,Tio2富集料
Abstract

中国的钒钛磁铁矿(VTM)是典型的复杂多金属有价矿物资源。目前VTM精矿中有价元素回收利用的典型技术为高炉法。然而,采用这种冶炼方法,精矿中的钛元素基本进入高炉渣而难以回收,同时,高炉法的钒回收率也较低。为获得优质的TiO2富集料用于钛提取,本论文设计了一种提钛新工艺。主要技术手段是利用还原剂(碳或氢)弱还原VTM精矿后,经稀硫酸浸出,浸出残渣即为目标产物。弱还原可以破坏VTM的稳定结构,促进铁在弱酸中的浸出,实现TiO2的富集。本文主要结果如下:VTM精矿经还原后,大部分铁在浸出过程中会转移至液相,获得富含TiO2的残渣。结果表明,还原程度与后续的浸出效果密切相关。优化条件为:还原温度1000oC,保护气氛下还原3 h,配碳量为VTM精矿质量的6%;在80 oC下用0.2mol/L的H2SO4溶液(L/S比为100:1)浸出3-4 h。浸出残渣含少量水合水,由锐钛矿、Al2FeO4和Fe3O4组成。脱水后,TiO2含量为72.2wt%,主物相为金红石,伴生相为Fe2TiO5和Fe2O3。通过测定不同碳量还原后的相组成,得出铁的还原途径为原始磁铁矿→Fe2.75Ti0.25O4→Fe2.5Ti0.5 O4→FeTiO3,其中FeO相一直存在,但FeO不稳定,易被还原Fe。在优化的还原条件下,主物相为Fe2.5Ti0.5 O4,并伴有部分金属Fe。另外,通过计算得出还原气体产物主要为CO。FeCl3溶液可以选择性地从还原后的VTM中浸出金属铁相。还原后VTM中的磁铁矿相在FeCl3溶液和H2SO4溶液的浸出明显不同。VTM精矿在最佳还原条件弱还原后,FeCl3溶液浸出渣的Fe/Ti摩尔比仍高达4.78,相当于Fe的浸出率约为19%,也表明还原后的VTM中有19%的金属Fe相;而用0.2mol/L硫酸溶液浸出后,浸出渣的Fe/Ti摩尔比仅在0.2左右。研究还发现,V、Al、Mg、Si、Ca和Mn等元素在FeCl3浸出过程中活性不高,据此提出经由碳还原、FeCl3浸出、稀H2SO4浸出联合富集TiO2的新流程。VTM精矿在1000oC下用15 wt%的碳量还原3 h后,FeCl3溶液可预浸铁68.7%,Fe/Ti摩尔比由6.30降至1.97。浸出残渣接着用0.1-1.0mol/L H2SO4溶液浸出,其它元素和剩余的30%铁均被溶解,得到TiO2含量约为53%的富集料。 弱还原还可用氢气完成。结果表明,通过调控温度及还原时间,可控制还原过程失重率在设定值,且发现,VTM还原后,关键元素的浸出行为与还原条件密切相关。在两个温度—时间组合的范围内,[850 oC/0.5 h,1000 oC/0.5 h]和[1000 oC/3 h,1000 oC/6 h],铁的浸出率均超过97%;而V、Mg、Al和Mn的浸出率在[850 oC/0.5 h,1000 oC/0.5 h]的还原条件范围内较高,在[1000 oC/3 h,1000 oC/6 h]的还原条件范围内较低。因此,通过调整还原参数,该工艺可以设计成同步浸出铁和钒或单独浸出铁的技术路线。在850-1000oC下还原0.5 h后,浸出渣为锐钛矿或锐钛矿与金红石的混合物;在1000oC下还原2 h后,浸出渣主要是钛铁矿以及少量Al2FeO4;在1000oC下还原3-6 h后,浸出渣物相为成分不固定的黑钛石。实验证明,用氢气在850-900oC下还原VTM 0.5 h、并用0.2mol/L硫酸溶液浸出后,可获得TiO2含量约为53%的钛富集料;用氢气在1000oC下深度还原VTM 6 h后、再用稀H2SO4溶液浸出,可获得钒与钛共存的钛富集料。本论文的研究结果确定了火法还原-湿法浸出联合工艺可从VTM精矿中获得TiO2富集料的可行性。;Vanadium titano-magnetite (VTM) is a typical complex valuable resource in China. The typical method used to recover valuable elements from VTM concentrates is by the blast furnace smelting method. However, titanium is nearly all wasted in the form of blast furnace slag. Also, the recovery rate of V is low too by the blast furnacesmelting process.In this thesis, a newpathway towards obtaining TiO2-enriched material for titanium extraction was designed. The main means is the combination of partial reduction by carbon or hydrogen and mild acid leaching by dilute H2SO4 solution. Partial reduction can destroy the stable structure of VTM, and promote the Fe leaching bymild acid to enrich TiO2 in the leaching residue. The key findings of this thesis were as follows.Even though the iron was not fully free from titanium after partial reduction, most of the iron could be transferred into the solution during leaching, leaving TiO2-enriched hydrated residue. The reduction degree and the leaching performance were co-related. The optimized conditions included reducing at 1000°C for 3 h with a carbon addition of 6% mass of VTM, leaching at 80oC for 3-4 h by using a 0.2 mol/L H2SO4 solution with a L/S ratio of 100:1. The TiO2-enriched residue contained hydrated water and was composed of anatase, Al2FeO4, and Fe3O4. The dehydrated residue contained 72.2 wt% TiO2, and its main phase was rutile, accompanied by Fe2TiO5and Fe2O3.By determining the phase composition after reduction for different dosages of carbon, the reduction route of iron in the magnetite phase of VTM is original magnetite → Fe2.75Ti0.25O4→ Fe2.5Ti0.5O4 → FeTiO3, and FeO accompanied all transformations; however, FeO is unstable and will be reduced to Fe if the reductant is available. The main phase was Fe2.5Ti0.5O4, accompanied by some metal Fe under the optimized reduction conditions. In addition, it was calculated that the main gas by product under the optimized reduction conditions was CO.Selective leaching of Fe metal phase from the reduced VTMs by FeCl3 solution could be reached. The performance of magnetite phase in FeCl3solution shows much difference from that in mild H2SO4solution. Under the optimal partial reduction conditions, i.e. with around 6% carbon dosage at 1000°C for 3 h, the Fe/Ti mole ratio of the residue was still as high as 4.78 when leached by FeCl3 solution, corresponding to about 19% leaching rate of Fe, also indicating 19 wt% Fe metal phase in the reduced VTM; while the Fe/Ti mole ratio was around 0.2 when leached by 0.2 mol/L H2SO4solution.It was found that the performance of V, Al, Mg, Si, Ca and Mn during FeCl3 leaching was also relatively inert, thus a new process composed by three main steps of deep carbon reduction, FeCl3leaching and mild H2SO4 leaching, could be designed. Fe2+enriched solution, V enriched solution and TiO2-enriched material were obtained by the new route. After reducing VTM with 15 wt% carbon dosage at 1000 °C for 3 h, 68.7% Fe could be pre-leached by FeCl3 solution, and the Fe/Ti mole ratio decreased from 6.30 to 1.97. The residue obtained from the FeCl3leaching step was further leached by 0.1-1.0 mol/L H2SO4solution, other elements and the remaining 30% iron were dissolved, and a TiO2-enriched material with around 53% TiO2 was obtained.The reductant for partial reduction of VTM can be replaced with hydrogen. It was found that the levels of temperature and reduction time can be coordinated to reach a designated value of weight loss. The leaching performance of the elements in reduced VTM was highly dependent on the reduction conditions. The leaching rate of Fe was ³ 97% relied on two temperature-time ranges of [850 ℃/0.5 h, 1000 ℃/0.5 h] and [1000 ℃/3 h, 1000 ℃/6 h]. The leaching rates of V, Mg, Al, Mn were high at [850 ℃/0.5 h, 1000 ℃/0.5 h] and low at [1000 ℃/3 h, 1000 ℃/6 h]. Thus the process can be designed to co-leach Fe and V or solely leach Fe via tuning the reduction parameters. The leaching residues were anatase or the mixture of anatase and rutile with low crystallinity when reduced at 850-1000 °C for 0.5 h, then the residues were ilmenite along with some Al2FeO4 when extending the reduction time to 2 h at 1000 °C, and the residues were magnesium titanate with unfixed chemical compositions when the reduction time was 3-6 h at 1000 °C. It was demonstrated that a TiO2-enriched material with around 53% TiO2could be obtained after partial reduction of VTM by H2 at 850-900 °C for 0.5 h and leaching by 0.2 mol/L H2SO4 solution. Deep reduced VTM at 1000 °C for 6 h by H2 could also be leached by mild H2SO4solution to enrich TiO2, with V stayed with TiO2-enriched material.The research results in this thesis have surely confirmed the feasibility of enriching TiO2 from VTM by a new pyro-hydro combined method. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/49651
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
FAIZA SAFDAR. 钒钛磁铁矿精矿弱还原-低酸浸出制备钛富集料的工艺研究[D]. 中国科学院大学,2020.
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