Knowledge Management System Of Institute of process engineering,CAS
攀枝花-西昌（以下简称攀西）地区钛资源储量占我国总储量的90%，在当前选矿技术获得钛精矿的钙、镁等杂质含量高，主要用于高能耗、重污染的硫酸法钛白或酸溶性钛渣的生产，难以制备满足先进沸腾氯化工艺要求的富钛料。开发攀西钛精矿制备沸腾氯化用富钛料新技术，已成为促进我国钛产业可持续发展的重要方向。本文以攀西钛精矿氧化焙烧-磁选提质和提质矿选择性氯化制备人造金红石工艺为研究对象，针对磁化焙烧过程难调控和氯化过程杂质钙、镁难去除的问题，采用高效可控的流态化氧化焙烧和流态化氯化技术方案，重点研究揭示焙烧-磁选过程矿物转化及杂质分离规律和选择性氯化过程钙、镁关键杂质氯化行为规律，建立优化调控机制，为建立攀西钛精矿提质制备人造金红石新技术提供参考。主要取得以下研究成果：（1）攀西地区红格矿区的钛精矿中钙、镁、铝、硅等非铁杂质含量较高，主体矿相存在含锰的钛铁矿和含镁的钛铁矿及未完全解离的硅酸盐脉石，磁饱和点和矫顽力分别为2000 Gs和270 Gs，具有弱磁性。热分析和物相转变研究结果表明，钛精矿在空气中，温度550 ℃以上开始氧化增重并放出热量，氧化新生成的Fe2O3与未氧化FeTiO3可形成磁性固溶体x FeTiO3·(1-x) Fe2O3，但会因继续氧化转变为TiO2和Fe2O3而磁性显著减弱。（2）基于流态化氧化焙烧实验结果，焙烧优化氧化磁化温度范围为650 ℃ ~ 750 ℃，温度越高使钛精矿达到磁性极值所需的时间越短。焙烧优化参数为725 ℃氧化30 min或650 ℃氧化90 min，样品中Fe2+/TFe含量比为0.51，其磁饱和点分别增大至9500 Gs和10000 Gs，矫顽力也增加至500 Gs和495 Gs，磁性明显增强。氧化后的钛精矿主体矿物与脉石边界出现一定程度的裂纹，经过湿式球磨5 min后，平均粒径可减小至42.20 μm，可基本实现脉石与主体矿物单体解离，继而有利于后续磁选分离去除。（3）不同参数下的磁选结果表明，杂质去除率随矿物粒度的减小或磁场强度的降低而略有增加，但钛回收率显著下降。在725 ℃氧化30 min、球磨5 min、磁场强度0.35 T的优化条件下，钛回收率47.45%，精矿中CaO、MgO、Al2O3和SiO2含量分别为0.28 wt.%、2.17 wt.%、0.63 wt.%和1.35 wt.%，相应去除率分别为81.82%、76.51%、81.35%和83.92%，可有效实现提质。磁选尾矿的TiO2品位仍高达46.50 wt.%，可直接用于硫酸法钛白或酸溶性钛渣生产，从而实现攀西钛资源的梯级利用。（4）热力学计算分析结果表明，氧化钛精矿中的铝、硅杂质难以被选择性氯化脱除，而铁、锰、钙、镁等杂质组分均可优先于钛组分发生氯化，可实现选择性氯化除杂，结合热力学平衡区域图，随着温度的升高可实现Fe、Ca、Mg选择性氯化的热力学平衡区域均有所减小；杂质铁和钙相对于钛可易于被选择性氯化去除，而杂质镁易形成难以氯化的二钛酸镁（MgTi2O5）稳定相，不利于其氯化去除。（5）为了满足流态化对物料的粒度要求，磁选提质精矿经过烧结造粒后用于选择性氯化实验。采用一氧化碳和氯气混合气体进行选择性氯化，可将杂质铁等实现氯化挥发脱除，而杂质锰、钙、镁等反应形成氯化物可进一步水浸脱除。杂质铁、锰的去除率均随氯化温度的升高和时间延长而逐渐增加，钙可在较低温度和较短时间内实现去除，而镁的去除率需要超过900 ℃时才较快增加，随氯化温度升高和时间延长杂质铝可发生氯化脱除，而杂质硅也可部分去除。（6）在选择性氯化过程中，杂质镁的有效脱除是制备人造金红石的关键。氯化过程遵循未反应核收缩方式，因杂质镁主要赋存于钛铁矿物相中，随着铁的氯化挥发和镁的富集，未反应核中的镁可形成较为稳定的钛酸镁（MgTiO3）和二钛酸铁镁（MgTi2O5-Fe2Ti2O7或MgTi2O5-Fe3Ti2O10），阻碍了镁的氯化去除和铁的深度去除，需要较高氯化温度和较长氯化时间才能有效去除，继而增加了钛的氯化损失。（7）在Cl2与CO体积比1:1、氯化温度1000 ℃和氯化时间60 min的优化参数下，提质钛精矿的氯化渣经水浸可得到TiO2品位为96.34 wt.%，杂质Fe2O3、MnO、CaO、MgO、Al2O3和SiO2含量分别为0.64 wt.%、0.01 wt.%、0.14 wt.%、0.66 wt.%、0.15 wt.%和1.77 wt.%的高品位人造金红石，杂质铁、锰、钙、镁、铝的硅去除率分别为99.53%、99.58%、81.84%、89.46%、93.84%和51.77%。产品粒径大于100 μm占比56.33%。初步形成的焙烧磁选矿提质-选择性氯化制备人造金红石新方法，为我国攀西钛资源高效利用提供新的途径。;The titanium resource reserve in Panzhihua-Xichang (also known as Pan-Xi) area accounts for 90% of the total in China. The ilmenite concentrate obtained from the existing beneficiation process can only be used for producing titanium dioxide pigment by sulphate process or smelting acid-soluble titanium slag with high energy- consumping and heavy polluting. It cannot be used as raw materials for the fluidized chlorination process due to high contents of of Ca, Mg and other components. It has become an important direction to promote the sustainable development of titanium industry in China to develop a new preparation technology of titanium rich materials for fluidizing chlorination from Pan-Xi ilmenite concentrate. In this work, the process of preparing synthetic rutile from Pan-Xi ilmenite concentrate by oxidizing roasting-magnetic separation and subsequent selective chlorination was studied. Focusing on the problems existing in the above process, such as hard to regulate magnetization in oxidation process and difficult to efficient removal calcium, magnesium and other impurities in the follow chlorination process, efficient and controllable fluidized oxidation roasting and fluidized chlorination technology were adopted. The study revealed the mineral phase transformation and impurities separation rules in the oxidizing roasting-magnetic separation process and the chlorination behavior of the key impurities of calcium and magnesium during selective chlorination process, in order to established an optimized regulation. It is valuable reference for a new artificial rutile prepared process from Pan-Xi ilmenite concentrate. The following research results have been obtained.(1) The Hongge ilmenite concentrate from Pan-Xi area was used as raw material, consistsing of manganese or magnesium bearing ilmenites as main mineral phases and silicate gangue not completely dissociated, which has a high content of calcium, magnesium, aluminum, silicon and other non-iron impurities. It is show weak magnetism with the magnetic saturation point and coercive force are 2000 Gs and 270 Gs respectively. The results of thermal analysis and phase transition showed that the ilmenite concentrate begins to gain weight and exotherm in the oxidation atmosphere above 550 ℃, Futhermore, the newly generated Fe2O3 and the unoxidized FeTiO3 can combined to generate magnetic solid solution (x FeTiO3·(1-x) Fe2O3), but its magnetism will be significantly weakened by continuous oxidizing into TiO2 and Fe2O3.(2) Based on the experimental results of fluidized oxidizing roasting, the optimal temperature range of oxidized magnetization is 650 ℃ ~ 750 ℃, Moreover the duration for oxidization of ilmenite concentrate to reach the magnetic extremum can be shortened by raising the temperature. Finally the optimized parameters of fluidization roasting with air are oxidation at 725 ℃ for 30 min or oxidation at 650 ℃ for 90 min, with which the Fe2+/TFe content ratio in the oxidized sample was 0.51, the magnetic saturation point increased to 9500 Gs and 10000 Gs respectively, and the coercivity also increased to 500 Gs and 495 Gs respectively. The magnetism of the ore sample was significantly enhanced. The boundary of the main mineral and gangue was cracked to a certain extent in the oxidized ilmenite. Besides, with wet ball grinding for 5min, the average particle size of oxidized ilmenite can be reduced to 42.20 μm, which can realize the gangue and the main mineral monomer dissociated is conducive to remove gangue at the subsequent magnetic separation process.(3) The results of magnetic separation under different parameters showed that the impurities removal rate increased slightly with the mineral particle size decreased or the beneficiation strength of magnetic field increased, but the titanium recovery rate decreased obviously. Under the optimized conditions: oxidation at 725 ℃ for 30 min, ball grinding time of 5 min and the beneficiation strength of magnetic field of 0.35 T, The titanium recovery rate was 47.45%, and the contents of CaO、MgO、Al2O3 and SiO2 in the concentrate were 0.28 wt.%, 2.17 wt.%, 0.63 wt.% and 1.35 wt.% respectively, with the corresponding removal rates of 81.82%, 76.51%, 81.35% and 83.92%. It can effectively achieve the quality ilmenite concentrate improvement. And the TiO2 grade of tailings is still up to 46.50 wt.%, which can be directly used for producing titanium dioxide pigment by sulphate process or smelting acid-soluble titanium slag to realize the cascade utilization of Pan-Xi titanium resources.(4) The thermodynamic analysis shows that the impurity oxides of aluminum and silicon in the ilmenite concentrate is difficult to be removed by selective chlorination. The oxides of iron, manganese, calcium, magnesium and other impurities could be chlorinated preferentially than titanium oxide, thus achieved impurities removal by selective chlorination. Combined with the thermodynamic equilibrium region diagram, the thermodynamic equilibrium regions that can achieve selective chlorination of Fe, Ca and Mg are decrease with the increase of temperature. Compare with titanium oxide, the oxides of iron and calcium could be easily selective chlorinated, while magnesium oxide is easy to form a stable phase of magnesium dititanate (MgTi2O5), which is tough to be chlorinated.(5) In order to meet the particle size requirements of fluidization,the upgraded ilmenite by magnetic separation was used for selective chlorination after granulation and sintering. The selective chlorination process with carbon monoxide and chlorine gas can remove iron by simultaneous volatilization, while the chlorination of manganese, calcium and magnesium and other impurities reacted into nonvolatile chlorides, which can be further removed by water leached. Concretely, the removal rates of iron and manganese increased gradually increased with chlorination temperature and duration, while calcium can be removed at lower temperature and in shorter duration. But the removal rate of magnesium increased rapidly only if the chlorination temperature exceeded 900 ℃. In addition, aluminum can be removed by chlorination at high temperature with long duration, while silicon can only be partially removed.(6) The key in the process of selective chlorination to produce synthetic rutile is efficient removal of magnesium. During the chlorination process with unreacted shrinking core model, magnesium was enriched in the unreacted core as iron chlorination and volatilization, to from the stable magnesium titanate (MgTiO3) and magnesium ferric dititanate (MgTi2O5-Fe2Ti2O7 or MgTi2O5-Fe3Ti2O10), reatarding the chlorination of magnesium and the deep removal of iron. Consequently it is require higher temperature and longer duration to effective removal of magnesium, leading to titanium revcovery decreasing synchronously.(7) With the optimized parameters of Cl2 and CO volume ratio of 1:1 and chlorination at 1000 ℃ for 60 min, the synthetic rutile with high TiO2 grade ( 96.34 wt.% ) was obtained from selective chlorination and subsequent water leaching of the upgraded ilmenite. The contents of Fe2O3, MnO, CaO, MgO, Al2O3 and SiO2 in the synthetic rutile were 0.64 wt.%, 0.01 wt.%, 0.14 wt.%, 0.66 wt.%, 0.15 wt.% and 1.77 wt.% respectively. And the impurities removal rates of iron, manganese, calcium, magnesium and aluminum were 99.53%, 99.58%, 81.84%, 89.46%, 93.84% and 51.77% respectively. The final products with particle size over 100 μm accounted for 56.33%. The preliminary established process of oxidation roasting - magnetic separation - selective chlorination of ilmenite concentrate provides a new method for the efficient utilization of Pan-Xi titanium resources in China.
|李哲. 攀西钛精矿提质制备人造金红石研究[D]. 中国科学院大学,2020.|
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