摘要
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。
The vanadium-bearing titanomagnetite concentrates(VTMCs)are a major raw material for vanadium extraction,but the existing process has some defects such as the low yield and long process flow. The leaching rate of vanadium is less than 65% by roasting and water leaching process using the VTMCs powders. In order to increase the leaching rate of vanadium,the VTMCs powders are mixed with sodium carbonate to form pellets by rolling forming process,and the oxidizing and Na-activation roasting and water leaching process were investigated. The high-chromium vanadium-bearing titanomagnetite concentrates(HCVTMCs)and sodium carbonate were mixed evenly according to a certain proportion,and then the mixture was formed pellet by rolling forming process. The green pellet was dried at 120 ℃ for 2 h to obtain the dry pellet in the electrothermal drier. The dry pellet was placed into a corundum crucible and was oxidation and Na-activation roasted in the box electric furnace when the temperature of electric furnace was 300 ℃. The time from 300 ℃ to set temperature was fixed at 2 h,and continue to roasting at the set temperature for 2 h. After reaction,the roasted pellets were rapidly taken out and cooled at room temperature,and crushed and ground to obtain roasted clinker powders. In a water leaching experiment,50 g roasted clinker powder was used to extracting vanadium via a water leaching process,and the fixed leaching conditions as follows,the leaching temperature was 95 ℃,the leaching time was 90 min and the liquid-solid ratio was 6∶1. Through analyzing the data of experiments,the conclusions were as follows:(1)The results of the thermodynamic analysis of oxidizing and Na-activation roasting processshowed that the order of reaction of main compounds in HCVTMCs was:FeTiO_(3)>Fe_(2)SiO_(4)>FeV_(2)O_(4)> FeCr_(2)O_(4)>Fe_(3)O_(4). FeV_(2)O_(4)was easier to form the water-soluble sodium salt than Fe_(3)O_(4)in thermodynamics,the oxidation reaction of FeV_(2)O_(4)was occurred on the premise that the Fe_(3)O_(4)structure must be destroyed due to the fact thatthe vanadiumwas embedded in Fe_(3)O_(4)in the form of isomorphism.(2)X-ray diffraction(XRD)patterns of roasting clinkers indicated that the sodium carbonate ratio had a great influence on the phase composition of calcined clinkers,and the peak intensity of unoxidized Fe_(3)O_(4)increased significantly with increasing the sodium carbonate ratio. The reaction of FeTiO_(3)with sodium carbonate was a simultaneous process of oxidation and Na-activation,and Na_(0.75)Fe_(0.75)Ti_(0.25)O_(2)intermediates was formed when the reaction was not sufficient.(3)The results of extraction vanadium showed that increasing appropriately roasting temperature and sodium carbonate ratio were beneficial to improve the leaching rate of vanadium,but excessive roasting temperature and sodium carbonate ratio were led to the leaching rate of vanadium decreased significantly. The increase of calcination temperature and the ratio of sodium carbonate were beneficial to the formation of low melting point phases such as Na_(4)TiO_(4),Na_(2)SiO_(3)and NaAlSi3O8in the roasting clinkers,and the chemical reaction of forming water soluble vanadate was hindered by the liquid phase.(4)The analysis results of X-ray photoelectron spectroscopy(XPS)showed that the vanadium was fully oxidized,and some iron and chromium were not oxidized to high valence state. There was no obvious peak position of vanadium and chromium in HCVTMCs,but the peak intensity of vanadium and chromium in roasted clinker was obvious. The atomic proportions of Cr^(6+)and Cr^(3+)in roasted clinkerwere 53.51% and 46.49%,respectively,and the atomic proportions of Fe3+and Fe_(2)+were 77.30% and 22.70%,respectively. 5. Scanning electron microscope(SEM)images of the roasted clinker and leaching slag showed that the surface structure of roasted clinker was compact and had crystalline attachments,while the cracks and voids were evenly distributed on the surface of leaching slag. The soluble sodium salt was leached from the roasted clinker,resulting in cracks and voids were appeared on the surface of leaching slag. In addition,the roasting clinker and leaching residue particles had two kinds of morphology:dense and loose. The iron was more concentrated in the dense,while vanadium,titanium and sodium were concentrated in the loose. Based on the thermodynamic analysis of oxidizing and Na-activation roasting process,the effects of roasting temperature and sodium carbonate ratio on the roasting and water leaching process were investigated with HCVTMCs pellets as raw material. During the roasting process,the oxidation of Fe_(3)O_(4)to Fe_(2)O_(3),sodium oxidation of FeTiO_(3)to NaFeTiO_(4),and sodium oxidation of vanadium oxides to water-soluble sodium vanadate were realized simultaneously. After the roasting process,the water leaching process was used to dissolve the water-soluble sodium vanadate in the roasted clinker. Finally,the leaching rates of V_(2)O_(5),Cr_(2)O_(3)and TiO_(2)were 89.70%,55.85% and 11.54%,respectively,under the condition of roasting temperature of 1100 ℃ with the sodium carbonate ratio of 15%. The oxidizing and Na-activation reaction of the larger particles in HCVTMCs were not sufficient. Reducing the particle size of HCVTMCs was helpful to improve the kinetic conditions of oxidizing and Na-activation reaction between HCVTMCs and sodium carbonate,and further increased the leaching rate of vanadium.
作者
吴恩辉
李军
徐众
侯静
黄平
蒋燕
Wu Enhui;Li Jun;Xu Zhong;Hou Jing;Huang Ping;Jiang Yan(Panzhihua International Research Institute of Vanadium and Titanium,Panzhihua University,Panzhihua 617000,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2022年第12期1599-1608,共10页
Chinese Journal of Rare Metals
基金
四川省科技计划项目(2019ZYD026,2020YFH0195)
四川龙蟒矿冶有限公司委托项目(HX2019066)资助。
关键词
高铬型钒钛铁精矿
球团
钠化焙烧
水浸
钒
high chromium-bearing vanadium titanomagnetite
pellet
Na-activation roasting
water leaching
vanadium
