| Vanadium is known as "monosodium glutamate of modern industry"because of its excellent properties.It is widely used in metallurgy,chemical industry,aerospace and other fields,and has an important strategic position.As the main raw material of vanadium extraction,vanadium slag has high grade and stable composition.However,the existing vanadium extraction process has the common problems of high energy consumption and heavy environmental pollution,so it is urgent to develop new environmentally friendly vanadium extraction process.Based on the study of the leaching behavior of calcium vanadate under pressure simulated by chemical pure reagent,the effect of calcination of vanadium slag on the leaching behavior of vanadium was studied by means of XRD,SEM-EDS and composition analysis.In view of the low yield of vanadium from calcified roasting of vanadium slag by pressurized ammonium leaching,a segmented pressurized ammonium leaching process was designed and developed to enhance the leaching behavior of vanadium.Under the experimental conditions,the following conclusions are obtained.(1)It is feasible to directly prepare V2O5 products for metallurgy by using pressurized ammonium leaching method to strengthen the leaching behavior of vanadium from calcified roasted vanadium slag,which can not only significantly improve the leaching rate of vanadium,but also eliminate the need for purification and impurity removal of leaching solution,and the vanadium extraction tail liquid can be recycled.(2)With the increase of Ca/V ratio,the calcined product changes from metavanadate to orthovanadate via calcium pyrovanadate.With the increase of calcination temperature,C a/V ratio and leaching temperature,the leaching rate of vanadium first increases and then decreases;By increasing the ratio of ammonium to vanadium and prolonging the leaching time,the dissociation process of calcium vanadate can be significantly improved,and the leaching rate of vanadium in calcined products can be increased,and the leaching rate of vanadium can reach more than 90%.(3)The vanadium slag is mainly composed of ferrovanadium spinel,peridote and pyroxene phases,and the spinel phase is mainly wrapped by silicate phase;Vanadium slag can dissociate from silicate phase at high temperature.The dissociation process can be accelerated by the addition of CaO.(4)Using two-stage pressurized ammonium leaching process,the total leaching rate of vanadium can reach more than 90%even under relatively low ammonium concentration and short leaching time;On this basis,the total leaching rate of vanadium can be increased to 94%by using three-stage pressurized ammonium leaching process. |
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