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金属钛物理化学性质优异，被称为“未来金属”，应用前景广阔。钛与氧化学结合力强，金属镁难以对氧化钛中氧进行深度脱除，因此现有金属钛生产方法是以四氯化钛镁热还原为核心的Kroll法。基于H可降低Ti-O固溶体热力学稳定性的原创性发现，美国犹他大学提出了TiO2镁热还原直接制备低氧含量金属钛粉的新方法（称为氢气协同镁热还原法，Hydrogen Assisted Magnesiothermic Reduction，简称HAMR法）。为制备氧含量低、颗粒尺寸均匀的高品质金属钛粉，HAMR法对前驱体二氧化钛及金属钛粉晶格氧含量有严格要求。本论文针对HAMR法要求的高品质TiO2原料制备及金属钛粉晶格氧控制的需求，基于低价钛氧化合物能被稀酸分解的特性，提出了富钛料铝热弱还原-稀酸溶钛-富钛液水解制备高品质二氧化钛的新方法。本论文重点开展新方法工艺研究，以及纯氢气气氛下镁热脱氧平衡条件，以为HAMR法的进一步优化提供理论依据。论文取得的主要创新成果如下：（1） 采用热力学软件HSC Chemistry 6.0对金属铝热还原二氧化钛过程的热力学计算结果表明，Al用量对生成的低价钛氧化合物的组成影响显著，随着Al用量增多，生成的钛氧化合物中钛的价态越低。实验研究证实，二氧化钛铝热还原过程中钛氧化合物呈现TiO2→Ti3O5→Ti2O3→TiO→Ti6O→Ti3Al的变化趋势。（2） 以二氧化钛为原料，研究了主要工艺参数对铝热还原二氧化钛效果、稀酸溶钛的影响规律，获得了优化的还原和酸浸条件。在Al/Ti摩尔比为0.45、温度为900 ℃、时间为4h、摩尔比为1:1的NaCl-KCl低温共熔盐的优化还原条件下，钛以Ti2O3和TiO、铝以氧化铝刚玉相存在；在6mol/L HCl，90 °C和200 min的酸浸条件下，钛溶出率为99.59%，铝溶出率为3.657%。（3） 以四氯化钛为原料，研究了主要工艺参数对富钛液水解制备高品质二氧化钛工艺的影响规律，获得了优化的水解条件；在温度为100 ℃，初始钛离子浓度为80 g/L、初始游离酸浓度为3 mol/L、时间为24h的优化条件下，制得的钛酸颗粒呈类球形、尺寸均匀分布在30 μm左右、表面光滑、流动性好，水解产率达99%以上。（4） 采用高钛渣对铝热弱还原-稀酸溶钛-富钛液水解制备高品质二氧化钛新方法进行了全流程验证。结果表明，在优化条件下，钛溶出率为92.45%，铝溶出率为7.69%，制得的钛酸颗粒球形度好、粒度分布均匀，新方法稀酸可循环使用，环境优势明显。（5） 研究了颗粒尺寸、反应时间、原料配比等动力学因素对脱氧过程的影响，获得了700-850 ℃纯氢气气氛下镁热脱氧平衡条件。在优化脱氧条件下，获得了纯氢气氛中，700、750、800、850 ℃时与MgO氧势基本相当的Ti-O-H三元固溶体的化学组成为TiO0.0252H2.0043、TiO0.0289H1.6640、TiO0.0425H1.3692、TiO0.1395H1.1215。;Titanium is known as the “future metal” due to its excellent physical and chemical properties, and has broad application prospects. The strong affinity of titanium to oxygen makes it difficult to deeply remove oxygen in titanium oxide by Mg, thus the industrial titanium production method is the Kroll process that based on the magnesiothermic reduction of titanium tetrachloride. Based on the original discovery that H can reduce the thermodynamic stability of Ti-O solid solution, the University of Utah proposed a new method for the preparation of low-oxygen titanium powder directly from TiO2 by magnesiothermic reduction (called Hydrogen Assisted Magnesiothermic Reduction, abbreviated as HAMR process). In order to prepare high-quality titanium powder with low oxygen and uniform particle size, the HAMR process is strict with the precursor titanium oxide and the content of lattice oxygen in titanium powder.This thesis is directed at the requirements of the HAMR process for the preparation of high-quality TiO2 raw material and the control of lattice oxygen in titanium powder. Based on the characteristic that titanium sub-oxide can be digested with dilute acid, a “aluminothermic reduction of titanium-bearing material”-“dilute acid digestion of titanium”-“hydrolysis of titanium-bearing solution” method was proposed. This thesis focuses on the research of new method and the equilibrium conditions of magnesiothermic deoxidation at pure hydrogen atmosphere, in order to provide theoretical basis for further optimization of the HAMR process. The main innovations of this thesis are as follows:(1) The thermodynamic calculation results of aluminothermic reduction of titanium oxide using thermodynamic software HSC Chemistry 6.0 show that the amount of Al has a significant effect on the formation of low-valence titanium sub-oxide, the valence of Ti in Ti-O compounds is being lowered with the increasing amount of Al. The experimental study confirmed that the Ti-O compounds exhibit a trend of TiO2→Ti3O5→Ti2O3→TiO→Ti6O→Ti3Al during aluminothermic reduction process.(2) Using titanium oxide as raw material, the effects of main process parameters on the effect of aluminothermic reduction of titanium oxide and dilute acid digestion of titanium were studied, and optimized conditions for reduction and acid digestion were obtained. Under the optimized reduction conditions: Al/Ti mole ratio is 0.45, the temperature is 900 °C, the time is 4h, with NaCl-KCl low temperature eutectic salt (mole ratio=1:1), titanium exists as Ti2O3 and TiO, aluminum exists as corundum. Under the optimized acid digestion conditions: 90 °C, 200 min, the leaching rate of titanium is 99.59%, the leaching rate of Al is 3.657%.(3) Using titanium tetrachloride as raw material, the effects of main process parameters on the hydrolysis of titanium-bearing solution for high-quality titanium oxide preparation were studied, the optimized hydrolysis conditions were obtained. Under the optimized conditions: the temperature is 100 °C, the initial titanium concentration is 80 g/L, the initial free H+ concentration is 3 mol/L, the time is 24h, titanic acid particles with near spherical morphology, smooth surface and good fluidity were obtained, the particle size is uniformly distributed at around 30 μm, and the hydrolysis rate is over 99%.(4) Using upgraded titanium slag as raw material, the whole new method for high-quality titanium oxide preparation was carried out. The result showed that under the optimized conditions, the leaching rate of titanium is 92.45%, the leaching rate of aluminum is 7.69%, titanic acid particles with good sphericity, uniform particle size distribution were obtained, and the dilute acid generated can be recycled, the environmental advantages are obvious.(5) The effects of particle size, reaction time and ratio of raw materials on the deoxidation process were studied. The equilibrium conditions of magnesiothermic deoxidation under pure hydrogen atmosphere at 700-850 °C were obtained. Under optimized deoxidation conditions, the chemical compositions of Ti-O-H ternary solid solution were obtained when the oxygen potential is basically equivalent to the oxygen potential of MgO, and is TiO0.0252H2.0043、TiO0.0289H1.6640、TiO0.0425H1.3692、TiO0.1395H1.1215 at 700、750、800、850 ℃ respectively.
|朱槿. HAMR法高品质TiO2原料制备及金属钛粉晶格氧控制研究[D]. 中国科学院大学,2019.|
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