Study On Phase Transitions During Reduction Of Vanadium-Bearing Titanomagnetite In Alkaline Molten Salt

Vanadium-bearing titanomagnetite is a major strategic mineral resource in China.The comprehensive utilization of V,Ti and Fe is of great significance.The selective reduction-sodium modification-smelting separation coupled process can simultaneously achieve smelting separation of iron and sodium modification of vanadium in one-step high-temperature smelting process,providing a new method for the economical and efficient utilization of the resource.In this study,the vanadium-bearing titanomagnetite in Liaoxi region was used to study the phase transitions during the reduction in alkaline molten salt.The main results of are as follows:(1)The reaction conditions for the sodium modification-selective reduction-smelting separation coupled process were studied.It is indicated that the separation status of iron can be enhanced with the increase of the temperature,the additive amount and the roasting time.The increase of the coal addition can enhance separation effect at first,and then restrain the separation effect when the C/Fe ratios were lager than 2.8.The percentage of V2O5 in the slag increased as decreasing the reaction temperature,the coal addition,the reaction time,and increased as increasing the additive amount.The optimal condition was determined.Under this condition,the separation of iron can be achieved efficiently as well as the enrichment of vanadium in the slag.(2)The phase composition of the slag and the effect of the additive on the properties of slag were studied.The results showed that the slag phase mainly consisted of CaTiO3,Na16Ti10O28,NaAlSiO4 and Na1.45Al1.45Si0.55O4.Under optimal condition,vanadium existeds in calcium titanate and sodium aluminosilicate phases.The addition of additive not only promotes the sodium modification of vanadium and inhibits the vanadium enrichment in metal phase,but also reduces the viscosity of slag and enhances the separation between the iron and the slag.(3)The reduction kinetics of the vanadium-bearing titanomagnetite in alkali molten salt was studied by using the infrared gas analyzer to detect the concentration of reducing gas.The results showed that the reduction reaction was firstly controlled by interface chemical reaction rate(R3),and then followed by the diffusion rate(D4).Theactivation energy of chemical reaction is Ei=-55904J/mol,E2=-78538J/mol,respectively.At the same time,increasing reaction temperature,reducing agent and decreasing additive amount can increase the rate constant of chemical reaction and promote the reaction.