| The vanadic titanomagnetite is the main mineral resource for producing vanadium. Generally, the vanadium-titanium magnetic iron ore is reduced to hot metal in blast furnace, and then the hot metal is oxidized in the converter furnace to gain vanadium slag. The following V2O5 recovery process is directly effected by the quality and the grade of vanadium slag, which is the main raw material to produce vanadium product. Thus, in order to understand the precipitation of Fe2VO4 in the vanadium slag, it is very important to study the microstructure change of vanadium slag in different temperature and the influence that the components such as SiO2, FeO and V2O5 have on the phases of vanadium slag.At present, the datum about the phase diagram of FeO-V2O5 and SiO2- V2O5 is considerable scarce.Besides, the thermodynamic data of the intermediate compounds in this system is also lacking , and there is even no datum of ferrovanadium spinel. As lacking of thermodynamic datum on, it is difficult to conduct diagram calculation and the gibbs free energy calculation for some reactions . Lacking the phase diagram of FeO-SiO2-V2O 5has brought much inconvenient to analyzing the basic theory of the vanadium extraction. Based on the study about the phase diagram, this paper conducts the research on the chemical composition and temperature of FeO-V2O5 system and SiO2- V2O5 system, which is useful for deeply understanding the solubility and solubility characteristics of V2O5 in the vanadium slag.After high-temperature quenching experiment, the specific phases in the FeO-V2O5 system and SiO2- V2O5 system can be analyzed by X-ray diffractions and EDS. By calculating the thermodynamic data of the intermediate compounds and the thermodynamic model of solution, the phase diagrams of FeO-V2O5 and SiO2- V2O5 are obtained by applying Factsage. The molten temperature region of the phase diagrams of FeO-V2O5 and SiO2- V2O5 is measured by hemisphere point instrument, and then the phase transition temperature is measured by DSC. The results can be used to verify the calculation parameters of the phase diagram solution model to get a relatively accurate phase diagram.The following results can be get by analyzing the binary phase diagram of FeO-V2O5 and SiO2- V2O5:①For the FeO-V2O5 phase diagram, this system consists of three eutectic reactions. When the molar fraction of V2O5 is between 0 and 0.15, and the temperature is 1588K, the eutectic reaction of L→FeO+αoccurs, and Fe2VO4 is generated. The Fe2VO4 will be stable at low temperature. When the molar fraction of V2O5 is between 0.15 and 0.42 and the temperature is 1071.9K, the eutectic reaction of L→α+βoccurs. As the content of V2O5 increases, FeVO4 will generate and it can coexist with Fe2VO4, besides, FeVO4 can be stable at the condition of room temperature. . When the molar fraction of V2O5 is between 0.42 and 1 and the temperature is 800K, the eutectic reaction is: L→β+V2O5. .When the molar fraction of V2O5 is more than 0.42, the products of this system are FeVO4+V2O3+V2O5.②For the SiO2- V2O5 phase diagram, when the mass fraction of SiO2 in the system is 32%and the temperature is 843K, there will be a eutectic reaction: L→V2O5+quartz ,but no intermediate compounds generate. The system will emerge V2O5 quartz tridymite and cristobalite with the change of composition and temperature.③Through experiments and phase diagram analysis to determine the phase transition temperature of FeO-V2O5, and SiO2-V2O5 system.To FeO-V2O5 system,the phase transition temperature are:890 1100 1240 1470 1550 1650 1750 K,and to SiO2-V2O5 system,the phase transition temperature are:950 1230 and 1670K.④In the production practice, When the molar fraction of V2O5 is 0.15-0.5.There are Fe2VO4 and FeVO4 generated in the system .When the molar fraction of V2O5 is between 0.1 and 0.5 from the phase diagram, and these two kinds of substances are useful for making vanadium transfer to slag. So it is benefit for the process of vanadium extraction to control the molar fraction of V2O5 to be between 0.1 and 0.5.
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