| 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 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 A1 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 ?,the time is 4h,with NaCl-KCI 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 ?,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 ?,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?m,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 ? 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?TiO0.1395H1.1215at 700?750?800?850 ? respectively. |
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