Study On Strenthening Of Solid-state Reduction And Comprehensive Utilization Of Vanadiferous Titanomagnetite

Vanadiferous titanomagnetite ore is quite rich in Pan-Xi Zone of China and its explored reserve is up to 98.49 billion tons,which accounts for 95%of total vanadiferous titanomagnetite resource in China and quarter of that in the world.The reserve of commensal titanium in the ore accounts for about 90.54%of total titanium reserve in China and about 35.71%of that in the world respectively.The reserve of commensal vanadium in the ore accounts for 62.6%of total vanadium reserve in China and 7.3%of that in the world respectively,which has quite high value of comprehensive utilization.So it is very significant to develop new technology process on utilizing vanadiferous titanomagnetite ore.In this paper,vanadiferous titanomagnetite ore of Pan-Xi zone in China was taken as main research object.Aiming to vanadiferous titanomagnetite concentrate and ihnenite concentrate obtained by mineral separation,solid-state reduction behavior of ilmenite and fundamentals of strengthening reduction processes were deeply discussed synthetically by these theories of kinetics,thermodynamics,structure chemistry,and so on, and modern microscopic measuring and testing technology,such asâ…©-ray diffraction,optical microscope,and scanning electron microscope and so on.Based on the above investigations,new technology process on comprehensive utilization of vanadiumferous titanomagnetite by solid-state reduction method were developed.The following conclusions were obtained.Part 1.Fundamental investigations on solid-state reduction of ilmenite and its reduction process of strengthening.1.The thermodynamics showed that the lower valence of titanium in the reduction products of ilmenite is,the more difficult reduction reaction is.The reduction reaction of ilmenite had better be put up under 1131.0℃to decrease the formation of low titanium oxide and carbide.2.Reduction kinetics showed that reduction rate of ilmenite was slow and reduction could not reach high reduction level.Reduction reaction was controlled by interfacial chemical reaction,and apparent activated energy of reaction was 125.594 kJ/mol in the range of temperature from 1000℃to 1150℃.Microscopic mechanism of ilmenite reduction showed that these phases such as,FeTi₂O₅,M₃O₅ solid solution(M stands for Fe,Ti,Mg,Mn et cl.)and Ti_nO_2n-1were found which would decrease the activity of iron ion,and the structure of reduction product.The enrichment of Mg in the unreacted core restricted the further reduction of ilmenite.3.Studies on effect of preoxidation on reduction behavior of ilmenite showed that preoxidation was able to speed up the reduction reaction and increase the metallizaiton rate of reduction product. Reduction reaction was controlled by interfacial chemical reaction,and apparent activated energy of reaction was 108.848 kJ/mol in the range of temperature from 1000℃to 1150℃.Compared with non-preoxidation, apparent activated energy of reaction was decreased by 16.746 kJ/mol. Microscopic mechanism on preoxidation strengthening reduction process showed that preoxidation could improve the structure of preoxidation product and reduction product and increase the activity of fresh ilmenite, which rooted in the new phase produced during reduction process of ilmenite destroyed the structure of original mineral and made mineral crystal particles defective.4.Studies on effect of additives on reduction behavior of preoxidation ilmenite showed that it was an important effect of the anion (group)in the alkali metal salt additives on solid-state reduction of ilmenite.In all investigations of alkali metals salt additive,the borax with boraic acid radical could greatly speed up reduction reaction rate of preoxided ilmenite and increase the metallization rate of reduction product apparently.Reduction reaction was controlled by interfacial chemical reaction,and apparent activated energy of reaction is found to be 80.263 kJ/mol in the range of temperature from 1000℃to 1150℃. Compared with non-additive,apparent activated energy of reaction was decreased by 28.585 kJ/mol.The mechanism of adding borax was that borax could decrease the melting point and accelerate the diffusion of mass unit.Sodium ion could bring the deformation of ilmenite crystal lattice and increase the activity of ilmenite.Boracic acid radical ion could reacte with MgO in the ilmenite,which held down the transfer of Mg towards the inner of reduction product particle and cancel the enrichment effect of Mg in the unreacted core.Part 2.Study on new processes of comprehensive utilization of vanadiferous titanomagnetite based on solid-state reduction.1.Strengthening reduction technology of ilmenite concentrate and rust technology of reduction product were studied and new process producing rich-titanium material by reduction-rusting of ilmenite concentrate pellet was developed.Under the optimum parameters,with Panzhihua ilmenite as raw material in the new process and rich-titanium material assaying with TiO₂ grade over 82%and recovery over 97%and red mud which could be used as raw material of iron-making are obtained, which realized the comprehensive utilization of ilmenite.2.Strengthening reduction technology of vanadiferous titanomagnetite concentrate,grinding-separation of reduction product and separation technology of rich-vanadium material were carried out and new process on reduction-grinding separation of ilmenite concentrate pellet was developed.Under the optimum parameters,vanadiferous titanomagnetite from Taihe was used as raw material in the new technology process and iron concentrate assaying with Fe grade over 93% and recovery over 86%and ilmenite concentrate with TiO₂ grade over 46%and recovery over 77%were obtained,at the same time the recovery of vanadium was over 76%,which realized the comprehensive utilization of iron,titanium and vanadium.In this paper,solid-state reduction behavior of ilmenite,kinetics and thermodynamics fundamentals of strengthening reduction process were discussed synthetically.And the point of view,important action of anion (group)in the alkali metal additives on reduction reaction of ilmenite, was put forward firstly and studied deeply.The fundamental on strengthening solid-state reduction of ilmenite was come into being.The ilmenite from Panzhihua was used as a studied object,using strengthening solid-state reduction technology of ilmenite which was added additives and preoxided,the new technology of comprehensive utilization of vanadiferous titanomagnetite accorded with Chinese resources has been developed,which has broken a new feasibility technology route for comprehensive utilization of vanadiferous titanomagnetite in China.