Investigation On Rusting Behavior Of Reduced Ilmenite And Strengthen Reaction Of Rusting Process

This thesis is a subject of molten salt intensifying ilmenite solid-state reduction,which is the subsidized item of State Natural Scientific Foundation for prominent young people(Approval Number:50504018).The reduction-rusting process is an effective method for preparation of titiamium-rich material because of its low cost and friendly environment.However,there are some problem in reduction-rusting process,for instance the rusting efficiency is low,which hasn't yet been fundamentally solved leading to the process failed to be used for producing titiamium-rich material in China.In this thesis,in order to slove the problem of low production efficiency in rusting process,rusting behavior of reduced ilmenite and controling factors affecting separation of iron from ilmentie have been studied systematically in terms of the abundance deposit titanium resource in Panxi area by comprehensive application theories on thermodynamics,kinetics,electrochemical,modem micro-testing technology such as optical microscopy,scanning electron microscopy and others.On this basis,strengthening of Ti-Fe separation efficiency and utilization of rusting production have been studied.Consequently,the conclusions are drawn as followings:(1) In ammonium chloride system,the iron removal rate is distinct effected by reduction conditions,the granularity of reduced ilmenite, liquid-to-solid ratio,ventilation rate and reaction temperature.The optimal rusting reaction conditions are as follows:reduction temperature 1100℃,reduction time 120min,material granularity -0.1mm,ammonium chloride concentration 1.6%,stirrting rate 600r/min,rusting teperature 700℃,ventilation rate 5×10³L·min^-1·m_-3,liquid-to-solid ratio 10:1, reaction time 6h,obtaining titiamium-rich material with TiO₂ 64.92%and recovery rate above 95%.(2) Adopting rusting reaction kinetics study,it is showed that rusting reaction is controlled by the surface chemical reaction and the apparent activation energy is 82.69kJ/mol in ammonium chloride sollution.By analysing the influencing factor of Ti-Fe separation,the conclusion is drew that the main influencing unit in rusting process is reaction rate rather than "in-situ rusting".(3) In ammonium chloride system,the iron electrochemistry test results show that iron rusting is remarkably controlled by the cathodic reaction and rusting reaction rate was enhanced by decreasing pH and reduced by Fe(OH)₃,Ca²⁺ and Mg²⁺.(4) Intensification of rust reaction rate shows that hydrochloric acid and pure oxygen accelerate rusting reaction.The rusting reaction kinetics study shows that hydrochloric acid reduce rusting reaction activation energy from 82.69kJ/mol to 24.14kJ/mol.And the optimum experiment condition by strengthening rusting reaction is temperature 70℃; ammonium chloride 1.6%,hydrochloric acid 4%,;pure oxygen current rate 5×10³L·min^-1·m^-3;stirring speed 600 r/min;the particle size mainly controlled below 0.1mm,reaction time 2 hours,obtaining titiamium-rich material with TiO₂ 83.67%and recovery rate above 95%.(5) The leaching experiment results show that leaching process in further heightens the grade of titiamium-rich material.The proper leaching plan is NH₄HF 0.5%,H₂SO₄ 10%,temperature 95℃,leaching time 1.5h,liquid-to-solid ratio 6:1,stirring speed 600 r/min and hydrolysate time lh,obtaining final titiamium-rich material is TiO₂ 91.08% which can be used in titanium dioxide production.After rusting reaction, by-product iron red can be used as ironmaking raw material or pigment, additional slurry can be treated by neutralization,then separated impurities and circularly utilized in rusting process.