Study On The Reaction Behavior In Sodium Roasting Of High Vanadium Slag

China is one of the countries in the world which have rich vanadium resources. Vanadium bearing titanomagnetite ore are abundant and the ore in Panxi area alone accounts for 95% of total vanadium bearing titanomagnetite resources in China. The vanadium slag refined from vanadium bearing titanomagnetite is called high vanadium slag because of its high vanadium content. During the sodium roasting process of the high vanadium slag for extracting vanadium, it is difficult to control the process parameter because the interaction reaction or mutual influence among components in the slag which affect the recovery of vanadium. Thus, it is important to clear the physical and chemical behavior in sodium roasting of high vanadium slag.In this study, high vanadium slag was used as raw material and Na2CO3 was selected as the sodium agent. A large number of thermodynamic calculations and analyses on the sodium roasting of the high vanadium slag were discussed for understanding the raction behavior. The effects of roasting temperature, roasting time, addition amount of Na2CO3, particle size of raw material, and fraction of components on the vanadium extraction of high vanadium slag was undertaken by utilizing some modern methods or analysis such as X-ray diffraction, XRF and ICP. Some research results were obtained as follows.(1) The thermodynamic calculations and analysis shows that the oxidation reaction of vanadium, iron, Fe2SiO4, FeV2O4 from high vanadium slag is feasible within the range of temperature; the oxidation oxygen partial pressure of iron, Fe2SiO4, FeV2O4 needed is far below the roasting process of oxygen partial pressure; under the experimental temperature, the reaction of water-soluble sodium vanadate formation is feasible when Na2CO3 was used as the sodium agent in sodium roasting process, and it is easier to happen with increasing temperature; the reactions between CaO, SiO2, TiO2, Al2O3 and Na2CO3, V2O5 is also feasible from the view of the thermodynamics.(2) The experimental research shows that the sodium roasting of high vanadium slag is a significant influence on vanadium extraction; the leaching ratio of vanadium increases with the increase of the roasting temperature below 850℃ and then decreases; the leaching ratio of vanadium increases with increasing roasting time below 60min and then decreases, finally tends to level off; the leaching ratio of vanadium shows uptrend as Na2CO3 content increases below addition of 20% Na2CO3 and then tends to level off; the leaching ratio of vanadium shows uptrend as particle size of raw material decreases and reaches the maximum at the particle size of-200(-74μm). Therefore, the optimum process parameters for sodium roasting are roasting temperature of 850℃, roasting time of 60 min, addition of 20% Na2CO3, particle size of -200(-74μm); during the sodium roasting process of high vanadium slag, CaO, SiO2, Al2O3, TiO2 and FeO in high vanadium slag is unfavorable to improve the leaching ratio of vanadium, and the leaching ratio of vanadium decrease with the increase of these contents; effect of MgO was little on the leaching ratio of vanadium.