熔融钒渣析晶调控高效提钒机理

Crystallization control mechanism of molten vanadium slag for effective vanadium transformation and extraction

基于熔融钒渣在不同冷却制度下导致钠化焙烧-水浸工艺提钒率波动大的问题,本文采用光学显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM+EDS)及电子探针(EPMA)等表征方法,研究熔融钒渣中钒的析出及钒尖晶石结晶特征对钒提取率的影响,并深入探讨了析晶调控高效提钒机理。结果表明:熔融钒渣的水淬温度对熔融钒渣中钒的析出率、钒尖晶石结晶粒度及钒渣钠化焙烧-水浸过程钒物相转化率及浸出率影响显著。在熔融钒渣降温过程中,1400~900℃为尖晶石快速成核生长期,900℃水淬后,钒基本完成从液相向尖晶石固相中的迁移,结晶相以钒铁尖晶石为主,其中钒呈均匀分散状态;900℃后,尖晶石生长变缓,并以钛铁尖晶石沿钒尖晶石边缘析出为主,尖晶石内部仍呈现钒的“中心聚集效应”。对1400℃、900℃和400℃水淬钒渣(Water-quenched vanadium slag,WQVS)分别进行钠化焙烧-水浸试验,水淬钒渣粒度小于0.15 mm,m(Na_(2)CO_(3))∶m(NaCl)∶m(WQVS)=10∶3∶100,焙烧温度为780℃,焙烧时间为200 min。将焙烧产物磨细至粒度小于0.18 mm后80℃水浸,浸出时间为45 min,钒浸出率分别为75.15%、95.09%和78.78%。这表明将熔融钒渣缓冷至900℃水淬可有效提高钠化焙烧-水浸工艺的钒提取率,并同时提高生产效率。

The vanadium extraction efficiency fluctuates greatly during sodium roasting-water leaching process caused by cooling methods of molten vanadium slag.In this paper,the effects of vanadium precipitation from molten vanadium slag and vanadium spinel crystallization characteristics on vanadium extraction rate were studied by using optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM+EDS)and electron probe(EPMA).The mechanism of efficient vanadium extraction controlled by vanadium-spinel crystallization was further discussed.The results show that the water quenching temperature of molten vanadium slag has a significant effect on the precipitation rate of vanadium from molten vanadium slag,the crystallization size of vanadium spinel,and the vanadium phase conversion and leaching rate of vanadium slag during the sodic roasting-water leaching process.During the cooling process of molten vanadium slag,the rapid nucleation growth period of spinel occurs at 1400-900℃,the migration of vanadium from molten liquid phase to solid phase spinel completes at 900℃,and the crystalline phase is dominated by vanadium spinel,in which vanadium is uniformly dispersed.After 900℃,spinel growth slows down,and ferro-titanium spinel grows along the edge of vanadium spinel,and the“central-aggregation effect”of vanadium presents in spinel.Sodium roasting-water leaching experiments were carried out on the water-quenching slag at 1400℃,900℃and 400℃,respectively.The particle size of water-quenching vanadium slag(WQVS)is less than 0.15 mm,and m(Na_(2)CO_(3))∶m(NaCl)∶m(WQVS)=10∶3∶100,the roasting temperature is 780℃,and the roasting time is 200 min.When the roasted products are ground with size less than 0.18 mm,and then arebleached in water at 80℃for 45 min,the vanadium leaching rates are 75.15%,95.09%and 78.78%,respectively.The extraction efficiency of vanadium and production efficiency can be improved by temperature-controlled crystallization of vanadium slag,that is,molten vanadium slag is firstly air slow-cooled to 900℃and then water-quenched.