Basic Studies On A Novel Process For Vanadium Recovery From Luohe-Type Iron Concentrate By Sodium Salts-Added Roasting Via Straight-Kiln Process

China has abundant vanadium resources,ranking first in the world.At present,V-Ti-bearing magnetite is the main raw material to extract vanadium,which is leached from vanadium-rich slag obtained by smelting of V-Ti-bearing magnetite in converter.Due to the poor resource endowment,the disadvantage of high energy consumption in the indirect vanadium extraction process gradually appears under the carbon peaking and carbon neutrality background,hence the direct vanadium extraction process is the development path in vanadium metallurgy.As a large magnetite deposit,the Luohe-type iron ore deposit associated with vanadium reserves of about 1.5 million tons（V₂O₅）,which is highly valuable for comprehensive utilization.In this paper,the technical idea of“synergistic iron oxidation and vanadium transformation under the action of sodium salts”was proposed for utilization of this Luohe-type V-bearing iron concentrate based on the direct vanadium extraction process.On the basis of the mineralogy characteristics of this iron concentrate,the transformation behaviors of vanadium,iron,aluminum and silicon components during roasting with sodium carbonate and the separation characteristics of their products were emphatically studied.Based on the results,a new technological flow of efficient extraction of vanadium from Luohe-type V-bearing iron concentrate is constructed,which provides a new approach for efficient utilization of vanadium resources in China.The major innovations and conclusions of this thesis are shown as follows:（1）A new technological flow for efficient extraction of vanadium from V-bearing iron concentrate based on belt roasting was established.V-bearing iron concentrate pellets were prepared using sodium carbonate as additive and coal-based colloidal compound binder as binder.The green pellets were oxidized by belt roasting,and iron and vanadium was separated by water leaching of ground pellets,and V₂O₅ product was obtained from leaching solution by extraction and precipitation methods.For a Luohe-type iron concentrate with 0.32%V₂O₅,under the optimized conditions:the green pellets were prepared with 5%sodium carbonate and0.25%（dry base）composite binder;dried pellets preheated at 1050°C for10min and roasted at 1280°C for 13min;and the water leaching system of grinding fineness of about 38μm,leaching temperature 120°C,time 180min and liquid to solid ratio 5:1,the vanadium leaching percentage reached84.94%.Compared with the existing indirect vanadium extraction process,the new process has advantages of short process and low energy consumption.Furthermore,in comparison with the existing process of direct vanadium extraction by chain grain-rotary kiln,the new process can improve the production efficiency and effectively avoid the problems of ring formation in the rotary kiln during sodium roasting.（2）The synergistic transformation mechanism of iron oxidation and vanadium conversion in vanadium-bearing iron concentrate under the action of sodium carbonate was elucidated.The transformation of vanadium-iron spinel into sodium vanadate was affected by the oxidation of iron components and the amount of liquid phase.Under the action of sodium carbonate,magnetite was oxidized to hematite（Fe2O3）,and vanadium-iron spinel was activated to sodium vanadate during the oxidizing roasting.The full oxidation of magnetite promoted the release of vanadium from spinel,which facilitated the reaction of vanadium components with sodium carbonate.The main functions of sodium carbonate included:one is to convert vanadium-iron spinel into water-soluble sodium vanadate;the other is to react with gangue components such as aluminum and silicon to produce sodium aluminosilicate salt with low melting point,promoting the transformation of vanadium components and the aggregation and growth of sodium vanadate particles.（3）A new coal-based colloidal composite binder was developed to replace bentonite for the preparation of iron concentrate pellets.The use of the composite binder solved the problem of pelletizing after adding sodium salt to iron concentrate,it also significantly improved the shock temperature of green pellets.Besides,bentonite with aluminum and silicon as the main components increased the consumption of sodium salt,compared with bentonite,the use of composite binder also avoided a large amount of sodium slat consumption and greatly improved the oxidation and leaching of vanadium.The pilot-scale tests shown that the conversion rate of vanadium in pellets with 0.25%（dry base）composite binder was27.21%higher than that of pellets with 1.5%bentonite after roasting.（4）The mineralogical characteristics of Luohe-type V-bearing iron concentrate was identified.The main phase of vanadium-bearing iron concentrate was magnetite,accounting for 90.53%.96.02%of vanadium occured in magnetite phase in the form of isomorphism,indicating that the occurrence state of vanadium in Luohe-type iron concentrate is obviously different from that of V-Ti-bearing magnetite.There are 80 figures,55 tables and 155 references in this thesis.