Study On The Roasting Behavior Of The Converter Vanadium Slag With MnO₂ And The Process Of Compound Roasting-Acid Leaching Process

Vanadium has high economic value and is an important strategic resource in nature.It is widely used in steel,military,metallurgy,chemical industry,aerospace and other fields.China has abundant vanadium resources and is one of the main producing areas of vanadium products in the world.Currently,vanadium resource in China mainly produced from vanadium titanomagnetite.After treating vanadium titanomagnetite with a series of processes,a raw extracted material for vanadium,converter vanadium slag,is obtained.In the traditional extraction process of vanadium by the calcification roasting,the vanadium-containing phases in converter vanadium slag adsorbs the molten phase at high temperatures,causing a sinter of the clinker phases.Hence,the vanadium can not oxidize completely,resulting in the leaching rate of the vanadium is low.Therefore,it is urgent to develop a more efficient and clean process to extract vanadium.In this thesis,setting the converter vanadium slag from Panzhihua,Sichuan Province as object,the phase transformation of converter vanadium slag-MnO₂ were studied firstly.Further,a new technology to extracted vanadium by converter vanadium slag-MnO₂-CaO composite roasting-acid leaching was proposed.The effects of roasting process and wet leaching process on the leaching efficiency of vanadium were studied,and the phase transformation of composite roasting was analyzed.It provides a new idea for the further development of vanadium extraction technology from vanadium slag.In addition,the vanadium extraction method of converter vanadium slag-MnO₂-CaO by stage roasting at low temperature was also explored.The conclusions of this study were as follows:（1）Phase transformation of converter vanadium slag-MnO₂ in the roasting process.At 25℃,The spinel phase is wrapped by olivine phase and vanadium was difficult to be extracted.With the roasting temperature rose,the combined water of converter vanadium slag would be lost at 380℃.At 540℃,MnO₂（Ⅳ）losed oxygen and promoted the oxidative decomposition of spinel.At 600℃,the structure of spinel and olivine were destroyed,and the vanadium slag was granulated.At this temperatrue,V（IV）mainly existed in converter vanadium slag.At 850℃,the final roasting product Mn₂V₂O₇ was formed,and the phase is not easy to sintered.The main valence state of vanadium is+5,and the leaching rate of vanadium reaches 84.90%through acid leaching medium.Combined with kinetic analysis,the roasting of converter vanadium slag-MnO₂ was controlled by 1.04 order reaction,and the total apparent activation energy and frequency factor were 92.741 k J/mol and 5.96.10³ min^-1,respectively.（2）Converter Vanadium slag-MnO₂-CaO composite roasting.The vanadium leaching efficiency was used as the evaluation basis of vanadium extraction efficiency.And the effects of different roasting and leaching conditions on leaching rate were studied.The results shown that leaching efficiency of vanadium was 91.62%with the optimal reaction conditions(roasting temperature=850℃,n（Ca/V）=0.6,n（Mn/V）=1.8,roasting time=2 h,leaching temperature=50℃,leaching time=60 min,V_H2SO4:V_H2O=1:4,and liquid:solid=4:1).Compared with calcified and manganized roasting,the vanadium leaching efficiency increased by 13%～15%,6%～7%,respectively.In the clinker,V（Ⅴ）was mainly found,and appeared to be an aggregation of particles.The final vanadium-containing products are Ca₂V₂O₇,Ca₃V₂O₈ and Mn₂V₂O₇.（3）The method of low temperature step-by-step roasting at low temperature was used to extract vanadium.Through the comparison of several roasting methods,it was found that the one-stage calcified and two-stage manganese roasting had better effect on vanadium extraction,and the leaching efficiency of vanadium could reach 85.44%at750℃.