Research On New Process Of Vanadium Pre-extraction From Vanadium-bearing Titanomagnetite Concentrate

As 98%vanadium reserves in the world are found in vanadium titanomagnetite at present,vanadium titanomagnetite is a very important mineral resource of vanadium.Also in china,it’s the main raw material of vanadium recovery because of the rich reserves in Sichuan Province,Chengde,etc..Extracting vanadium from vanadium slags,produced in iron-steel making process of vanadium titanomagnetite,is the traditional process,which is uniquely employed by factories now.However,there are many problems with this traditional process,including low recovery ratio,serious pollution,high resources wastes and so on.So this paper pay attention to pre-extracting vanadium from vanadium titanomagnetite.Currently,one deeply and generally researched pre-extracting vanadium method is sodium roasting-water leaching.But it can’t still be applied in practice due to a lot troubles.In older to meet the contemporary increasingly strict demands of environmental protection and make good use of resources,two new processes of pre-extracting vanadium from vanadium titanomagnetite concentrate were developed in this research:(1)No salt roasting-high temperature alkaline leachingWithout any additive,vanadium titanomagnetite concentrate was oxidized by oxygen in the air at high roasting temperature.the leaching process was conducted in an autoclave.What’s more,alkali was used as leaching agent.Theoretically,based on study on thermodynamics containing calculation of reactions’Gibbs free energy and analysis of E-pH diagrams,the above new process of vanadium pre-extracting vanadium from vanadium titanomagnetite concentrate was proved to be feasible.Furthermore,the experimental results showed:vanadium loss ratio increased with increasing of roasting temperature;in a given time,the leaching ratio of the calcined material which roasted in powder was 17%higher than that of the calcined material which roasted in pellet;the leaching ratio of the high pressure leaching was 20%higher than that of the constant pressure leaching;comparing kinds of leaching agents’ experimental results,the more appropriate one is NaOH;vanadium leaching ratio increased at first and then decreased with increasing of roasting temperature;vanadium leaching ratio increased at first and then was constant with the extension of roasting time;vanadium leaching ratio increased obviously when leaching temperature increasing below 200℃;the size of calcined material had a significant effect on vanadium leaching ratio;the leaching liquid-solid ratio had little effect on vanadium leaching ratio;vanadium leaching ratio increased obviously at first and then changing slowly with rising of leaching agent’s concentration.By overall considering of vanadium leaching ratio,experimental cost,energy consumption and test cycle,the optimized experimental conditions were obtained,and the leaching ratio of vanadium in vanadium-bearing titanomagnetite concentrate could reach 63.6%under these conditions.(2)Direct oxygen pressure acid leachingInstead of employing the traditional roasting-leaching process to extract vanadium,vanadium-bearing titanomagnetite concentrate was directly put in the autoclave,the target of releasing,oxidizing and leaching vanadium could be realized under the conditions of high oxygen pressure,high temperature and acid leaching.The idea of direct oxygen pressure acid leaching to extract vanadium from vanadium-bearing titanomagnetite was proved to be a feasible process by thermodynamic calculations.Univariate multivariate experiments showed:the higher oxygen pressure,the higher oxidation degree of vanadium-bearing titanomagnetite concentrate,and the higher vanadium leaching ratio.The leaching result increased 10%when the oxygen pressure was improved 0.4MPa.Moreover,the vanadium leaching ratio could improved at higher leaching temperature and sulfuric acid concentration.Compared to those traditional processes of extracting vanadium,these two new processes of vanadium pre-extraction from vanadium-bearing titanomagnetite concentrate have more advantages on aspects of technology,energy conservation and environmental protection.