【作者】 李新生；

【导师】 谢兵；

【作者基本信息】 重庆大学 ， 冶金工程， 2011， 博士

【摘要】 钒是一种重要的战略物资,广泛应用于钢铁工业、航空航天工业及化学工业等领域。近年来,随着钢铁工业的发展,普通铁矿石的供应量日趋紧张,为了应对日益严峻的形势,同时充分利用攀西地区钒钛磁铁矿,某钢厂成功开发了钒钛磁铁矿小高炉冶炼技术,钒钛磁铁矿配加量达30%以上,产出的铁水中钒含量达到0.15%以上。为了回收铁水中这部分钒,采用转炉双联提钒工艺,得到的钒渣中V₂O₅含量小于10%,CaO含量大于5%,与普通钒渣（含12-25% V₂O₅、0.7-2.5%CaO）相比,该钒渣具较高的钙、较低的钒等特点。对于这种特殊的钒渣,目前没有较好的处理方法。本课题采用钠化焙烧-水浸与钙化焙烧-碳酸钠浸出技术从高钙低品位钒渣中提钒,探索其可行性并对氧化焙烧过程与浸出过程进行了详细的研究,为工业提钒提供理论指导。首先对高钙低品位钒渣的物相组成及元素的点、面、线分布进行了研究。结果表明:高钙低品位钒渣由尖晶石相、橄榄石相和辉石相组成。尖晶石呈连结状或分散状,其颗粒大小一般为20-30μm。在尖晶石中元素的含量从高到低依次是:铁、钒、钛、氧、铬、锰、铝;在尖晶石中心部分钒和铬的含量较高,而尖晶石外层钛、锰、铁和铝的含量较高;在橄榄石中元素的含量从高到低依次是:氧、硅、铁、锰;在辉石相中元素的含量从高到低依次是:硅、氧、钙、铁、铝、钛。采用碳酸钠为添加剂,对钒渣钠化氧化焙烧-水浸过程进行了研究,考察了氧化焙烧过程与浸出过程对钒浸出的影响、钒渣氧化焙烧过程物相变化、钠化焙烧渣浸出过程物相变化、钒酸钠的形成机理等。结果表明:①钠化焙烧-水浸提钒的最佳条件:碳酸钠加入量为18%,焙烧温度为700℃,焙烧时间为150min;浸出温度为90℃,浸出时间为30min和浸出液固比为5:1mL/g。在此优化条件下,钒浸出率可达89.5%以上,浸出液中主要杂质为Si、P和Cr。②钒渣钠化氧化过程与焙烧渣水浸过程物相变化。1)在碳酸钠加入量为18%时,钒渣的氧化温度范围为273℃至700℃;橄榄石相与尖晶石相分别在500℃和600℃分解完全;大部分水溶性钒酸钠在500℃与600℃之间形成;当焙烧温度在700℃以上时,钒酸钠富集相明显可见。当焙烧温度过高时,样品出现烧结,钒被玻璃相包裹。2)在水浸过程中,除了钠盐在水浸中溶解外,浸出残渣的主要物相与焙烧渣基本一样;而焙烧渣中钒酸钙与磷酸钠或硅酸钠反应转化为可溶性的钒酸钠,同时可除去浸出液中的杂质硅和磷。③钒酸钠的形成机理。三氧化二钒与碳酸钠反应时,在200℃到400℃之间首先生成钒氧化物VO_m （1.5<m<2.5）和钠的氧化物（如:Na₂O、Na₂O2 ）;在300℃到500℃之间形成中间产物（钒青铜）NaV₆O₁₅、Na₅V₁₂O₃₂和NaV₃O₈;在500℃到600℃之间,钒青铜被氧化成水溶性的钒酸钠。采用氧化钙为添加剂,对钒渣钙化氧化焙烧-碳酸钠浸出过程进行了研究,考察了氧化焙烧过程与浸出过程对钒浸出的影响、钒渣氧化焙烧过程物相变化及氧化动力学、氧化钙含量对钒渣氧化过程及焙烧渣碳酸钠浸出过程的影响、钒酸钙的形成机理、钙化焙烧渣浸出过程物相变化及浸出过程动力学等。结果表明:①钙化焙烧-碳酸钠浸出提钒的最佳条件:焙烧温度为850℃,焙烧时间为60min;碳酸钠浓度为160g/L,浸出温度为95℃,浸出时间为150min,浸出液固比为10:1mL/g和搅拌速度为400r/min。在此优化条件下,钒的浸出率达90%以上,浸出液中主要杂质为Si和P。②钒渣氧化焙烧过程物相变化及氧化动力学。1)钒渣的氧化温度范围为300℃到900℃,橄榄石和尖晶石分别在500℃和800℃分解完全,在850℃以上钒的富集相形成,当焙烧温度达到1000℃时,样品被烧结。2)钒渣的氧化过程可以用未反应收缩核模型来描述,在氧化过程中受内扩散控制,初始阶段（0-10min）反应的表观活化能为126.6kJ/mol。③氧化钙含量对钒渣氧化过程及焙烧渣碳酸钠浸出过程的影响。1)氧化钙含量从6.39%变化到36.39%的样品中均形成了钒的富集相;随着样品中氧化钙含量的增加,焙烧渣中主要物相Fe₂O₃、Fe₂TiO₅和SiO₂相应的衍射峰强度逐渐减弱;当样品中氧化钙含量为21.39%时,CaFe₂O₄和CaTiO₃的衍射峰出现。2)在碳酸钠浸出过程中,焙烧渣中的钒被转化为可溶性的钠盐进入溶液中,同时生成碳酸钙,且碳酸钙的衍射峰强度随着氧化钙含量的增加而增强;而其他主要物相基本不变。④钒酸钙的形成机理。当三氧化二钒与碳酸钙反应时,钒酸钙的形成主要取决于起始原料中V₂O₃和CaCO₃的比例和焙烧温度。在400℃时,部分钒被转化为钒青铜Ca_0.17V₂O₅。在500℃时V₂O₃氧化成V₂O₅。在600℃时,当V₂O₃:CaCO₃为1:1时,主要产物为Ca（VO₃）₂;当V₂O₃:CaCO₃为1:2时,主要产物为Ca（VO₃）₂和CaV₂O₇;当V₂O₃:CaCO₃为1:3时,主要产物为CaV₂O₇。当温度进一步升高,Ca（VO₃）₂会转化为Ca₂V₂O₇,进而转化为Ca₃（VO₄）₂。⑤钙化焙烧渣碳酸钠浸出过程可用未反应收缩核模型来描述,在浸出过程中受扩散控制,反应的表观活化能为51.75kJ/mol。更多还原

【Abstract】 Vanadium is defined as an important strategic material which is widely used in many fields such as steel industry, aerospace industry and chemical industry, etc. In recent years, with the rapid development of iron and steel industry, the ordinary iron ore resources have been decreased. In order to deal with the increasingly serious situation and make full use of vanadium titano-magnetite ore in Panxi region in China, the small blast furnace for smelting of vanadium titano-magnetite ore has successfully developed, more than 30% of vanadium titano-magnetite ore is added in normal iron ore during blast furnace process. In such case, the vanadium content in hot metal reaches above 0.15%. In order to recover the vanadium from the hot metal, the duplex process was used, and then the vanadium in hot metal was selectively oxidized into slag. The V₂O₅ content in vanadium slag otbained is less than 10% while CaO content is more than 5%. Compared with the normal metaurgical slag （12-25% V₂O₅, 0.7-2.5%CaO）, the vanadium slag in this study contains lower V and higher Ca content. At present, there is no a better way to extract vanadium from the special vandium slag. In this paper, the feasibility of sodium salt roasting-water leaching and calcium salt roasting-soda leaching for extraction of vanadium from high calcium low-grade vanadium slag were investigated, and the oxidation process and leaching process were studied in detail. The comprehensive evaluation results could provide a theoretical direction for vanadium extraction in industrial production.At first, mineralogical composition and the spot, surface and line analysis of element in vanadium slag were investigated. The results show that high calcium low-grade vanadium slag is composed of spinel phases, olivine phases and pyroxene phases. The spinel presents connection and dispersion state and its particle size is usually 20-30μm. The descending order of element content in spinel phase is iron, vanadium, titianium, oxygen, chromium, manganese, aluminium. The content of vanadium and chromium in center part of spinel phase is higher while the content of titanium, manganese, iron and aluminium in outer part of spinel is higher. The descending order of element content in olivine phase is oxygen, silicon, iron, manganese. The descending order of element content in pyroxene phase is silicon, oxygen, calcium, iron, aluminium, titianium.Oxidation process and water leaching process were investigated using Na₂CO₃ as additive. The effect of oxidation process and leaching process on leaching efficiency of vanadium, phase transition of vanadium slag in oxidation process and roasted samples in water leaching, and formation of sodium vanadates were studied, etc. The results show that①The optimum process parameters for vanadium extraction are follows: addition of 18% Na₂CO₃, roasting temperature of 700℃, roasting time of 150min; leaching temperature of 90℃, leaching time of 30min and liquid to solid ratio of 5:1mL/g. Under the optimum conditions, the leaching efficiency reaches above 89.5%. The main impuritie are Si, P and Cr in the leach liquor.②Phase transition of vanadium slag in oxidation process and roasted samples in water leaching. 1)Slag sample with 18% Na₂CO₃ is oxidized in the temperature range from 273℃to 700℃. Olivine phases and spinel phases are completely decomposed at 500℃and 600℃, respectively. Most of water-soluble sodium vanadates are formed between 500℃and 600℃. When roasting temperature reaches above 700℃, the vanadium-rich phases of sodium vanadates can be obviously observed. However, at temperatures above 800℃, the samples are sintered. Most of vanadium is enwrapped by glassy phase compounds. 2) The major mineral matters of leach residues are hardly changed except that sodium salts dissolve in water; the calcium vanadates in roasted samples are transformed into sodium vanadates by reacting with Na₃PO₄ or Na₂SiO₃ during water leaching, at the same time, the Si and P in the liquor can be removed.③Formation mechanism of sodium vanadates. When V2O3 reacts with Na₂CO₃, vanadium oxides VOm （1.5<m<2.5） and sodium oxides （e.g. Na₂O, Na₂O₂ ） are formed between 200℃and 400℃. The stable intermediates species （i.e. vanadium bronze） such as NaV₆O₁₅, Na₅V₁₂O₃₂ and NaV₃O₈ are mainly formed between 300℃and 500℃. Then the vanadium bronzes are oxidized to water-soluble sodium vanadates in the temperature range of 500℃-600℃.Oxidation process and soda leaching process were investigated using CaO as additive. The effect of oxidation process and leaching process on leaching rate of vanadium, phase transition and kinetics of vanadium slag in oxidation roasting process, effect of CaO content on oxidation of vanadium slag in roasting process and roasted sapmles in soda leaching, formation mechanism of calcium vanadates and phase transition and kinetics of roasted samples in soda leaching were studied. The results show that①The optimum process parameters for vanadium extraction are follows: roasting temperature of 850℃, roasting time of 60min, Na₂CO₃ concentration of 160g/L, leaching temperature of 95℃, leaching time of 150min, liquid to solid ratio of 10:1 mL/g and stirring speed of 400r/min. Under the optimum conditions, the leaching rate of vanadium reaches above 90%. The main impurities are Si and P in the leach liquor.②Phase transition and kinetics of vanadium slag in oxidation roasting process. 1)The vanadium slag is oxidized from 300℃to 900℃. The olivine phases and spinel phases in vanadium slag are completely decomposed at 500℃and 800℃, respectively. The vanadium-rich phases are formed above 850℃. When roasting temperature is 1000℃, the samples are sintered. 2) Oxidation process of vanadium slag can be described by the unreacted shrinking core model and is controlled by internal diffusion. The apparent activation energy is 126.6kJ/mol in the initial stage （0-10min）.③Effect of CaO content on oxidation of vanadium slag in roasting process and roasted sapmles in soda leaching. The vanadium-rich phases are formed when CaO content is varied from 6.39 to 36.39% in slag sample. The intensity of diffraction peaks of major phases Fe₂O₃, Fe₂TiO₅ and SiO2 in roasted samples decreases with the increase of CaO content. The diffraction peaks of CaFe₂O₄ and CaTiO₃ appear when CaO content in salg sample is 21.39%. 2) During soda leaching, the calcium vanadates in roasted samples is transformed to soluble sodium salt, at the same time, the CaCO₃ is produced and its relative intensity of diffraction peak increases with the increase of CaO content; the other major phases in samples are hardly changed.④Formation mechanism of calcium vanadates. When V₂O₃ reacts with CaCO₃, formation of calcium vanadate is dependent on the molar ratio of the starting materials and calcination temperature. Partial vanadium is transformed into vanadium bronze Ca0.17V₂O₅ at 400℃. The V₂O₃ is oxidized to V₂O₅ at 500℃. At 600℃, when the molar ratio of V₂O₃ and CaCO₃ is 1:1, the main product Ca（VO₃）₂ is formed; when the molar ratio of V₂O₃ and CaCO₃ is 1:2, the main products Ca（VO₃）₂ and CaV₂O₇ are formed; when the molar ratio of V₂O₃ and CaCO₃ is 1:3, the main product CaV₂O₇ is formed. With increasing calcination temperature, Ca（VO₃）₂ is transformed into Ca₂V₂O₇ or even Ca₃（VO₄）₂.⑤Soda leaching process of roasted samples can be described by the unreacted shrinking core model and is controlled by internal diffusion; the apparent activation energy is 51.75kJ/mol.更多还原