| Vanadium titanomagnetite concentrate is an important source of vanadiumtitanium resources in China.The traditional blast furnace method has a low recovery rate of titanium,and the direct reduction method still faces problems such as poor separation of vanadium and titanium and large energy consumption in subsequent electric furnace smelting,which are severely restrict the comprehensive utilization of the ore.Hence,this thesis proposed the process of roasting pretreatment-potassium pyrosulfate(K2S2O7)cooperating with ammonium sulfate((NH4)2SO4)cascade roasting-induction leaching of iron powder under the normal pressure system,and ammonium chloride(NH4Cl)roasting-acid leaching process under pressure system,aiming to provide a new reference for the comprehensive utilization of vanadium titanomagnetite concentrate resources.This thesis took the high-titanium vanadium titanomagnetite concentrate with TFe grade of 42.53%,vanadium grade of 1.43%and TiO2 grade of 23.5%as the research object.The influence of(NH4)2SO4 cascade roasting under normal pressure and NH4Cl roasting under pressure on the leaching rates of vanadium,iron and titanium were systematically studied,and the two processes were compared and summarized.The results showed that the vanadium titanomagnetite concentrate was roasted pretreatment under the normal pressure,and the optimal conditions were determined as the temperature of 900?,the time of 2 h,and the air flow rate of 4 L/min.The insoluble trivalent vanadium would be oxidized into acid-soluble VO2 and V2O5.At the same time,the vanadium titanomagnetite concentrate could be restructure into a porous structure with the specific surface area and pore volume of 37.33 m2·g-1 and 0.11 m3·g-1,respectively,which was beneficial for the liquid acidifier produced by the subsequent(NH4)2SO4 roasting to pass through the internal pores of the particles to realize the full sulfation of each valuable component.Through Factsage software simulation,it is found that adding K2S2O7 with a mass fraction of 10%contributed to the generation of liquid phase in the ammonium sulfate roasting process.When the ratio of ammonium to ore of 4:1,potassium pyrosulfate content of 10%,the first-stage roasting temperature of 240?,the firststage roasting time of 3 h,then the temperature was increased to 410? for 2 h at a rate of 10?/min,and the roasted product was leached at 110? for 1 h,10%iron powder was added and continued for 2 h.the leaching rates of vanadium,iron and titanium were 97.39%,88.62%and 8.24%,respectively.XRD and SEM-EDS analysis showed that when the vanadium titanomagnetite concentrate was cascade roasted with K2S2O7 cooperating with(NH4)2SO4 after roasting pretreatment,iron and titanium were transformed into NH4Fe(SO4)2 and TiOSO4,and the lattice vanadium was converted into soluble potassium polyvanadate,which inhibited the formation of insoluble calcium vanadate.The TiOSO4 was easy to hydrolyze and precipitate when the solution was boiling,realizing the selective separation of vanadium iron and titanium from vanadium titanomagnetite concentrate.After the titanium-rich leaching residue was desiliconized by alkaline leaching,a hightitanium slag product with the TiO2 grade and recovery rate of 85.32%and 91.25%was obtained,and the additive(NH4)2SO4 could be recovered.Aiming at the vanadium and iron-rich leaching solution formed under the normal pressure,a process for synergistic extraction of vanadium with P204 and P507 was proposed.After the continuous 5-stage countercurrent extraction test,the extraction rate of vanadium reached 98.13%.The maximum co-extraction coefficient and distribution ratio of vanadium were 2.58 and 26.23,respectively.After using dilute sulfuric acid with a volume fraction of 20%for continuous three-stage countercurrent stripping of vanadium,the concentration and recovery of vanadium in the vanadium-rich solution were 0.559 g/L and 94.75%,respectively.Meanwhile,an iron oxide red product with a mass fraction of Fe2O3 of 97.2%was prepared by the precipitation.ATR-FTIR and slope method proved that the composite extractant P204-P507 was associated in the form of hydrogen bonds and could undergo cation exchange reaction with VO2+ ions.This paper also developed the process of ammonium chloride roasting-dilute HCl leaching vanadium titanomagnetite concentrate under a pressurized system.Based on the thermodynamic analysis of NH4Cl roasting vanadium titanomagnetite concentrate under the pressurized system,when the roasting temperature of 320?,the time of 2 h and the ammonium ore ratio of 1.5,the leaching rates of vanadium,iron and titanium were 95.1%,92.5%and 1.2%,respectively.The resulting secondary chlorination could strengthen the chlorination process of each valuable component in the vanadium titanomagnetite concentrate.The valueof pressure under the optimal roasting conditions was only 0.19 MPa and its operation was safety.For the vanadium and iron-rich leaching solution formed in the pressurized system,the extraction rates of vanadium and iron reached 99.2%and 98.74%,respectively,under the condition that the organic phase composition of 10%N235,5%TBP and 85%sulfonated kerosene for continuous three-stage countercurrent extraction.The Na2SO4 washing-Na2CO3 stripping process was used to separate and recover vanadium and iron,and the concentration and recovery rate of vanadium in the obtained vanadium-rich liquid were 1.58 g/L and 91.19%,respectively.Meanwhile,35.0%and 87.92%of TFe grade and recovery rate for yellow ammonium iron vitriol product and 90.27%and 91.70%of TiO2 grade and recovery rate for high titanium slag product were prepared.In terms of energy consumption and product quality,the NH4Cl roasting-weak acid leaching process under the pressurized system was better than the roasting pretreatment-K2S2O7 synergistic(NH4)2SO4 cascade roasting process of vanadium titanomagnetite concentrate under normal system. |
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