Study On Softening-melting Property And Phase Transformation Of Vanadium Titanium Burden

Titanium and vanadium are recognized strategic metals in the world,which are widely used in aerospace,marine engineering,medicine,communication and some other fields.Vanadium-titanium magnetite(VTM)is an important mineral resource that is rich of Fe,Ti,V and other elements,and it is also the main carrier of vanadium and titanium resources.At present,blast furnace smelting is still the main way for Pangang to realize the comprehensive utilization of vanadium-titanium magnetite.However,the proportion of high-titanium-type vanadium-titanium magnetite in the Panzhihua area is still less than 70%,which greatly limits the efficient use of vanadium-titanium resources.It is because the TiO₂ in vanadium-titanium magnetite will form high-melting substances that makes the slag becoming viscous resulting in poor fluidity,such as perovskite and titanium carbonitride during the blast furnace smelting process.At the same time,it will eventually lead to poor permeability of the material layer,which will affect the blast furnace performance and the normal operation.Therefore,it is urgent to further study the behavior of titanium-containing charge in the cohesive,especially the change of main phases in the charge,the migration of valuable elements(Fe,Ti,V),and the high-temperature interaction between mixed charges.This is of great significance to further increase the proportion of VTM into the furnace,the blast furnace forward and improve the utilization of resources.Firstly,the transfer process of valuable elements were analyzed theoretically from the perspective of thermodynamics.Secondly,the softening-melting properties of VTM and the migration rules of VTM with valence element in cohesive were studied,respectively.Finally,the melting behavior and its interaction law of mixed charge structure were discussed.The following conclusions are drawn:(1)The thermodynamic calculation shows that the reduction process of iron oxides conforms to the principle of gradual transformation.The reduction of ti-iron compounds was carried out in the order of Fe₂TiO₅?Fe₂TiO₄?Fe TiO₃.The reduction of titanium oxide was carried out in the order of TiO₂?Ti₃O₅?Ti₂O₃?Ti N/Ti C.The reduction order of vanadium is:FeO·V₂O₃?V₂O₃?VO?VN/VC/[V].It is difficult to generate TiO,Ti and V in the soft fusion experiment.In the presence of N₂,nitride will take precedence over carbides in the softening-melting process of VTM.(2)The melting interval of the softening-melting process of vanadium titanium sinter is 225°C and the characteristic value S is 1917k Pa·°C.The melting interval in the softening-melting process of vanadium titanium pellet is 181°C,and the characteristic value S is 507k Pa·°C.The melting interval of the softening-melting process of the mixed burden is 220°C,and the characteristic value S is 1269k Pa·°C,which indicates that the pellet and lump ore added to the mixed burden can significantly reduce the melting interval and improve the permeability of the burden layer,which is conducive to the smooth running of the blast furnace.(3)The iron oxides in the vanadium-titanium sinter and vanadium-titanium pellets are in accordance with the principle of gradual transformation during the reduction process;the titanium components in the sinter are based on titanomagnetite,perovskite?ulvite?ilmenite?TiO₂?titanium carbonitride,perovskite regular migration,the vanadium component is based on iron oxide,calcium ferrite,glass phase?iron,perovskite,pyroxene,spinel?iron,pyroxene regular migration;while the titanium components in the pellets migrate according to the rules of pseudobrookite?titanomagnetite/ulvite?ilmenite?TiO₂?titanium carbonitride,and the vanadium components follow iron oxide?olivine,iron,spinel?ulvite,iron?iron regular migration.(4)The slag-forming process of sinter is more complex than that of pellet.With the reduction of high iron oxide to wustite,FeO will be involved in the slag-making and then the reduction will continue.In addition to the iron,the phase components of the softening stage also contain wustite,ti-fe compounds,(calcium)magnesium silicate and perovskite.After entering the melting stage,the amount of wustite and ti-fe compounds decreased significantly.Finally,the main components of the slag phase were Mg₂SiO₄,Ca Al₂Si₂O₈,Ca₂Mg Si₂O₇ and Ca TiO₃,which approached to the equilibrium components of the phase diagram.(5)The high-temperature interaction between the mixed burden is mainly due to the diffusion of SiO₂ in the softening stage and CaO and MgO in the melting stage,and the interaction between the mixed burden is affected by the chemical composition of the material.