| The traditional vanadium extraction process from vanadium-titanium magnetite is based on the vanadium extraction process from vanadium slag,but this process has the problem of a low comprehensive recovery rate of vanadium.This paper intends to extract vanadium from vanadium-titanium magnetite concentrate by using the direct vanadium extraction process of first extracting vanadium and then iron smelting.The concentrate is subjected to pellet roasting and selective vanadium leaching under the conditions of pelleting to achieve the purpose of separation of vanadium from iron and high-efficiency leaching of vanadium.Moreover,the leached pellets can meet the subsequent blast furnace production after simple treatment,and realize the combination of beneficiation and smelting.This article first analyzes the process mineralogy of the concentrate.The results show that the main phases in the concentrate are ilmenite and magnetite,while vanadium mainly exists in the magnetite phase as vanadium-iron spinel.After thermodynamic analysis,it is inferred that the oxidation reaction chain of vanadium-iron spinel is FeV2O4?Fe3O4?Fe2O3?V2O5.The blank roasting-vanadium leaching study of vanadium-titanium magnetite concentrate pellets shows that the use of sulfuric acid as the leaching agent can effectively realize the separation of vanadium and iron.Under the experimental conditions that the roasting time is 180 min,the roasting temperature is 1200?,the leaching time is 6 d,the liquid-to-solid ratio is 3:1,and the sulfuric acid concentration is 10%,the vanadium leaching rate can reach 60.30%,while the iron loss rate is only 0.17%.To achieve the purpose of selective leaching of vanadium.The results of calcification roasting and vanadium leaching of vanadium-titanium magnetite concentrate pellets show that choosing calcium carbonate as a roasting additive can effectively increase the vanadium leaching rate.The optimal experimental conditions were determined:calcium carbonate addition amount 5%,roasting time 3h,roasting temperature 1200?,leaching time 6 d,leaching temperature 50?,sulfuric acid concentration 10%,liquid-solid ratio 3:1.The optimal leaching rate of vanadium is 88.90%,and the iron loss rate is 1.78%,which can realize the selective leaching of vanadium.At the same time,the leached pellets can achieve the purpose of desulfurization after twice roasting,and the strength of the pellets after the second roasting can reach 2600 N/piece,which can meet the strength requirements of subsequent ironmaking.The analysis of the selective leaching mechanism shows that vanadium in concentrate exists as V3+in ferrovanadium spinel.After calcification and roasting at 1200?,the spinel structure is destroyed,Fe3O4 is oxidized to Fe2O3,and vanadium is mainly converted to V5+Reacts with calcium to form calcium vanadate.After the pellets were leached with sulfuric acid,a CaSO4 diffraction peak was detected,indicating that the calcium vanadate produced by roasting reacted with sulfuric acid,causing the vanadium to be leached.At the same time,the test results all indicate that the iron is not leached,indicating that the roasted Fe2O3 is not easily leached by sulfuric acid,to achieve selective separation.In this paper,the method of roasting of concentrate pellets and sulfuric acid leaching of vanadium can achieve the effect of leaching vanadium and retaining iron,and finally achieve the purpose of separation of vanadium and iron and the combination of separation and smelting.This research can provide directions for the industrial practice of direct vanadium extraction from vanadium-titanium magnetite concentrates. |
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