【作者】 赵卓；

【导师】 李小斌；

【作者基本信息】 中南大学 ， 有色金属冶金， 2010， 博士

【摘要】 钒是一种重要的合金元素,但其可供有价提取的资源较为不足。我国每年有1-5万吨钒进入氧化铝生产流程,这是一种重要的钒资源,且氧化铝流程中钒的存在对氧化铝产品质量有较大影响。因此,把钒从氧化铝流程中提取出来是十分必要的。从氧化铝生产流程提取钒的方法很多,而在工业上应用的唯一方法为结晶法,但此法回收率低,且只适用于钒含量高的母液,对于国内钒含量普遍较低的母液结晶法无法实现。因此,开发新的氧化铝流程高效提钒技术势在必行。本论文首先研究了钒对氧化铝流程的关键工序—溶出及分解过程的影响规律,结果表明流程中的钒对溶出过程基本无影响,而对分解过程影响较大,可造成产品纯度的下降和粒度的细化,从而明确了钒是一种对氧化铝流程危害较大的杂质。在确定拜耳法种分母液作为氧化铝流程中提钒原料的基础上,通过分析讨论提出了本论文的技术路线：母液沉钒-含钒沉淀浸出-离子交换-二次沉钒-偏钒酸铵焙烧,并对各工艺过程进行了系统深入的研究。通过对母液沉钒过程的热力学分析,发现了钒离子与母液中其它离子反应的热力学规律,并以此为指导,针对传统工艺沉钒后所得的含钒沉淀渣中V2O5含量较低的问题,提出了沉淀渣循环用于母液沉钒的新工艺,使沉淀渣中V2O5含量提高至2%以上,实现了母液的高效沉钒。含钒沉淀浸出过程的热力学分析结果表明,此沉淀渣适宜采用Na2CO3溶液在低温条件下浸出；通过对此过程的动力学研究,发现其控制步骤为固膜扩散控制；在热力学和动力学理论研究的基础上,针对直接采用Na2CO3溶液进行浸出时浸出率不高的问题,提出了浸出时通入CO2气体的改进工艺,使浸出率由80%提高到90%以上,并通过考察Na2CO3浓度、CO2通气量、温度、液固比及浸出时间等因素对浸出效果的影响,确定了适宜的浸出工艺条件。树脂吸附钒阴离子过程的动力学研究结果表明,201×7树脂对浸出液中钒离子的吸附效果较好,吸附率可达87%以上,201×7树脂吸附钒离子过程符合动边界模型,其控制步骤为颗粒扩散控制；吸附过程实验研究结果表明,采用201×7树脂吸附浸出液中的钒离子可获得较好的吸附效果,吸附率达95%左右；解吸过程实验研究结果表明,采用1mol/LNaCl+1mol/L NH4Cl的解吸体系进行解吸可取得较好的效果,解吸率可达97%以上；通过考察浸出液流速、吸附温度和吸附pH值等因素对吸附过程的影响及解吸体系、解吸剂浓度、解吸温度和解吸剂流速对解吸过程的影响,确定了合理的离子交换工艺条件。二次沉钒过程实验研究结果表明,解吸后的溶液加入NH4Cl进行沉钒,可达到较好的效果,沉率可达98%；根据二次沉钒过程反应的特点,推导出了此过程的动力学方程,并结合在考察解吸液浓度、pH值、加氯化铵系数和温度的影响规律时的实验结果,确定了动力学方程的各项参数,其反应速率常数为9.16×10-5mol/L·s,反应级数为0.932,同时也确定了二次沉钒过程的适宜工艺条件；对于偏钒酸铵焙烧过程,主要通过实验考察了焙烧温度及焙烧时间的影响情况,确定了合适的焙烧工艺条件,并制得达到GB3283-1987标准对冶金99级V2O5产品品质要求的产品,实现了钒的回收。通过本论文的研究,首次在技术上实现了利用除结晶法外的其它方法从氧化铝流程中回收钒,并具有高效且可处理钒含量低的母液的优势。以本论文研究得出的拜耳法种分母液中提取V2O5的技术路线为基础,有可能开发出从拜耳法种分母液提取V2O5的工业化技术,如果能够在氧化铝厂推广应用,不仅可消除钒对氧化铝生产流程的危害,提高产品质量,而且可产生较好的经济效益,形成新的产品,有效缓解氧化铝厂产品单一,抗击市场风险能力低的问题。更多还原

【Abstract】 Vandium is an important alloy element, but its resource which can be extracted economically is relatively scarce. It is estimated that the quantities of vanadium brought into alumina process per year are about 10-50 thousand tons, which is an important vanadium resource. Furthermore, the existence of vanadium in alumina process has large influence on the quality of alumina product. Therefore it is quite necessary to extract vanadium from alumina process.The unique method which has been applied in industry to extract vanadium from alumina process is crystallization method though there are many methods. Unfortunately, this method has the defect of very low recovery rate. Moreover, it only fits to treat liquors with high vanadium concentration and can’t be able to treat liquors from domestic factories, in which the vanadium concentration is low. It is imperative to develop new technique to extract vanadium from alumina process efficiently.The influence rules of vanadium on digestion and precipitation, which are the two key procedures of alumina process, were investigated firstly. The results showed that the vanadium in alumina process basically had no effect on digestion but influenced precipitation greatly, resulting in the decrease of purity and the thinning of particle size of product. Conclusion can be made that vanadium is an impurity with great harm for the alumina process.On the basis of confirming the spent liquor of Bayer process as the material for extraction of vanadium, the technical route of this dissertation was proposed after analysis and discussion. The route included the following procedures:precipitation of vanadium from spent liquor, leaching of vanadium-containing residue, ion exchange, secondary precipitation of vanadium and roasting of ammonium metavanadate. All of the procedures were investigated systematically and completely.The thermodynamics ruls of the reactions between vanadium ion and other ions in spent liquor were discovered by the thermodynamics analysis of the reactions during the precipitation of vanadium. On this basis, according to the problem that the V2O5 content in the vanadium-bearing residue is low after precipitation of vanadium by using traditional method, a new method, that the vanadium-bearing residue was used to precipitaite vanadium circularly, was proposed. By using this method, the V2O5 content in vanadium-bearing residue could be improved to more than 2%, showing that vanadium was precipitated from spent liquor efficiently.The thermodynamics analysis results of the leaching of vanadium-bearing residue showed that the residue was fit for being leached by Na2CO3 solution at low temperature. By the kinetics investigation of this procedure, its kinetics control step, which is the diffusion rate of reacting reagents in a porous solid layer, was found. On the basis of thermodynamics and kinetics results, according to the problem of low leaching rate by using Na2CO3 solution directly, a improved method, which adds the ventilation of CO2 during leaching, was proposed. By using this method, the leaching rate could be improved from 80% to more than 90%. Suitable leaching conditions were selected by investigating the influence of leaching solution concentration, CO2 ventilation, temperature, liqid-solid ratio and leaching time on leaching.The kinetics investigation results of the adsorption of vanadium anion by resin showed that 201x7 resin had good adsorption effect on vanadium ion and the adsorption rate could be more than 87%. Moreover, the adsorption process was accordance with moving boundary model and its dominant procedure was ion diffusion through particles. Experiments investigation of adsorption showed that good adsorption effects could be obtained by using 201x7 resin to adsorb the vanadium ion in leaching solution and the adsorption rate was about 95%. Experiments investigation of desorption showed that by using the desorption system of lmol/LNaCl+lmol/L NH4Cl, good desorption effects could be obtained and the desorption rate was more than 97%. The influence of flow rate, temperature and pH on adsorption, and the influence of desorption system, desorption agent concentration, temperature and flow rate on desorption were investigated. The suitable condtions for ion exchange were found.Experiments investigation of secondary precipitation of vanadium showed that good precipitation effects could be obtained by adding NH4Cl into the desorption solution and the precipitation rate of vanadium could be 98%. According to the characteristics of the reaction for secondary precipitation of vanadium, the kinetics equation for this procedure was deduced. At the basis of the experiments results for the investigation on the influence rules of desorption solution concentration, pH, KNH4Cl and temperature the parameters of the kinetics equation were calculated that its reaction rate constant was 9.16×10-5 mol/L·s and its reaction order was 0.932. Meanwhile, the suitable conditions for secondary precipitation of vanadium were found. During the investigation on the roasting of ammonium metavanadate the suitable conditions were found by investigating the influence of roasting temperature and roasting time. More importantly, V2O5 product which meets the requirements of GB3283-1987 standard for metallurgy 99 grade was prepared. The recovery of vanadium from alumina process was realized.Through the research of this dissertation, for the first time the recovery of vanadium from alumina process comes true by using another method except for the crystallization method. And this method has the advantage of high efficiency and being able to treat liquor with low vanadium concentration. On the basis of the technical route discovered by this dissertation for recovery of vanadium from spent liquor of Bayer process, it is possible to develop industrial technique for recovering vanadium from spent liquor of Bayer process. If the industrial technique can be applied widely in alumina factories, not only the negative effect of vanadium on alumina process can be eliminated, resulting in the improvement of product quality but also good economic benefit can be achieved because of the form of new product. Therefore, the pressure of simple product and low ability of countering market risk of alumina factories can be effectively relieved.更多还原