Reseach On Kinetics Of Vacuum Carbothermal Reduction Of Ilmenite Concentrate

The Panzhihua ilmenite concentrate is enriched in vanadium titanomagnetite and obtained by secondary dressing in tailings after the first beneficiation of vanadium titanomagnetite.The content of impurity elements such as calcium and magnesium is high and needs to be further enriched.The preparation of titanium slag by electric furnace has become the main industrial process.However,non-ferrous metal impurities can not be effectively removed in the electric furnace process,which will have an impact on the follow-up process.Therefore,how to remove impurities such as calcium and magnesium in ilmenite concentrate becomes a key problem.Vacuum treatment of ilmenite concentrate can effectively remove impurities such as calcium and magnesium and obtain high-grade titanium slag.In this paper,the kinetics of vacuum reduction of ilmenite concentrate was studied,and the following main conclusions were obtained:The increase of reduction temperature and the prolongation of holding time were beneficial to the reduction of ilmenite concentrate and the nucleation and growth of metallic phase,but the effect of reduction temperature was much higher than that of holding time.The main reduction process of the titanium-iron oxide was FeTiO₃?FeTi₂O₅?Ti₃O₅?Ti₂O₃,it entered the volatilization stage at 1400°C.During the reduction process,the solid solution appeared and decreased the reduction effect of iron,and the oxides of titanium were reduced from high-valence state to low-valent state and enriched gradually.The study of non-isothermal kinetics shows that the reduction of iron in ilmenite concentrate during the heating process belonged to the Z-L-T model control of three-dimensional diffusion,and the overall reduction of ilmenite concentrate belonged to the anti-Jander model control of three-dimensional diffusion.The apparent activation energies of the reduction process were 587.4±2.98 kJ/mol and233.16±8.40kJ/mol,respectively.It was concluded that the volatilization process of Fe,Mg and Si during the high temperature process accords with the Jander equation of three-dimensional diffusion,the G-B equation of three-dimensional diffusion and the Valensi equation of two-dimensional diffusion,respectively.The apparent activation energies of volatilization process were 1043.02±12.29,253.15±7.63 and314.46±6.04 kJ/mol,respectively.The study of isothermal kinetics shows that in heat preservation at 1100-1250°C for 0-30min and heat preservation at 1100-1300°C for 30-90min,the reduction of iron in ilmenite concentrate were controlled by the interfacial chemical reaction and internal diffusion,respectively,and the apparent activation energies of the reduction process were 207.92 kJ/mol and 521.47 kJ/mol,respectively,the overall reduction of the ilmenite concentrate were controlled by the external diffusion and the carbon gasification reaction,respectively,the apparent activation energies of the reduction process were 314.57 kJ/mol and 162.10 kJ/mol,respectively.