【作者】 龙思思；

【导师】 冯其明； 张国范；

【作者基本信息】 中南大学 ， 矿业工程， 2013， 博士

【摘要】 石煤是我国一种重要的含钒资源,目前从石煤中提钒普遍使用酸浸工艺,但该工艺存在设备腐蚀大、浸出液中杂质种类多、浸出剂不能循环使用等缺点。石煤碱浸提钒工艺钒浸出率高、设备腐蚀小、浸出液中杂质种类少、对环境友好,但该工艺浸出剂价格昂贵、成本高,因此难以得到广泛应用。为了降低生产成本、增加附产值、提高石煤碱浸工艺的竞争力,本文主要研究石煤碱浸提钒工艺过程中硅资源的提取和浸出剂的循环使用技术,旨在实现石煤中有价元素钒高效提取的同时将石煤碱浸液中的硅制备成具有商业价值的高比表面积白炭黑产品,并使浸出剂得到循环使用,最终形成石煤中钒硅资源综合利用新技术。在系统工艺研究的基础上,本文从石煤碱浸液体系的溶液化学性质出发,研究了实现石煤中钒硅资源综合利用的二大关键环节：即碱性溶液中钒、硅的分离问题和碱性溶液中钒的提取问题。主要成果如下：(1)碱性溶液中碳分法钒硅分离的理论与技术碳分法可以实现石煤提钒碱浸液中钒、硅的良好分离。往石煤提钒碱浸液中充入CO2气体,一方面充入的CO2气体将与强碱性介质NaOH溶液发生化学反应生成Na2CO3或NaHCO3,体系pH值降低,生成的Na2CO3或NaHCO3可经过后续苛化处理制备NaOH,从而为浸出剂的循环使用奠定基础；另一方面,随着体系pH值的降低,溶液中硅的过饱和度增大,当体系呈中性或弱碱性时,溶液中的硅将以沉淀形式析出而此时钒在溶液中保留,从而实现了碱浸液中的钒、硅分离。石煤碱浸液碳分过程热力学研究表明,硅从溶液中析出的主要原因是由于溶液中硅过饱和度升高而产生的白发析出。碳分过程动力学研究表明,CO：的吸收受液膜扩散控制。(2)高品质白炭黑的制备从石煤提钒碱浸液中制备白炭黑的主要影响因素为反应温度和终点pH值,此外,适量表面活性剂的加入和二次碳分工艺均可提高白炭黑产品比表面积。在石煤碱浸液的碳分法脱硅过程中,溶液中钒的存在不影响硅沉淀的生成。碳分脱硅渣中的钒是以V4O124-物理吸附的形式存在的,稀硫酸对脱硅渣中钒的脱除效果好。碳分法制备高纯度、高比表面积白炭黑的技术关键在于对产品进行酸洗处理,酸洗处理不仅可使产品得到净化还可改变其孔结构、提高比表面积。采用碳分法脱硅-酸洗处理脱硅渣工艺可以从石煤碱浸液中制备出了比表面积大于500m2/g的高品质白炭黑产品。(3)碱性溶液中钒的萃取行为与技术本文比较了碱性溶液中钒酸钙沉淀法和萃取法两种钒富集方法。在钒酸钠与碳酸钠共存的体系中,Ca(OH)2对溶液中的钒酸根离子和碳酸根离子均有良好的沉淀效果。热力学计算表明,碳酸钙沉淀将优先生成。实现碳酸钙与钒酸钙分步沉淀的关键在于控制反应温度和Ca(OH)2用量。N263对于弱碱性环境下钒的萃取效果好,采用N263为萃取剂,可从石煤碳分母液中高效回收钒。由于钒酸钙沉淀法提钒工艺流程相对较复杂、且对操作要求高,因此为了最大限度的提高钒提取效率,应优先考虑萃取法提钒工艺。(4)石煤中钒硅资源综合利用新技术根据试验研究结果,形成了以控制焙烧、强化碱浸、碳分脱硅、萃取富集钒、钒产品制备、白炭黑产品制备、苛化回收浸出剂为特征的石煤中钒硅资源综合利用新技术工艺流程。实验室小试结果表明,全流程可获得高于75%的V205总回收率；每生产lt V2O5产品,可副产9t以上比表面积大于500mZ/g的高品质白炭黑；全流程75%左右的浸出剂可以得到循环使用。浸出剂的循环使用以及碱浸液中硅资源的高效利用大大降低了石煤碱浸提钒工艺的生产成本,增加了工艺副产值,且碱浸提钒工艺环境污染小,使得碱浸提钒工艺较酸浸提钒工艺更具竞争力。更多还原

【Abstract】 Stone coal is important vanadium resources of our country. Currently, acid leaching process is widely used to extract vanadium from the stone coal. The process has many disadvantages, such as corrosion of the equipment, complex constituents of the leaching solution, leaching agent not recycled. The alkali leaching process overcomes these shortcomings with a high leaching rate, but the leaching agent used is cost which hinders the widely application of the process. To lower the cost, increase the added value of the product and improve the competitive strength of the process, the utilization of the silicon from the stone coal and recycle of the leaching agent were investigated in this paper. The goal is to invent a novel technology of comprehensive utilization of vanadium and silicon from stone coal, which produces high-quality white carbon black products from the silicon in the leaching solution and recycles the leaching agent when efficiently extracting vanadium from the stone coal. On the basis of the systematic research of the process, two key points of the process were investigated theoretically, which are the separation of vanadium and silicon in alkali solution and the extraction of vanadium from alkali solution, starting from the solution chemistry properties of the leaching solution of the stone coal. The major results are as below:(1) Separation of vanadium and silicon in alkali solutionGood separation of vanadium and silicon was achieved by carbonation method。 Adding CO2gas to the leaching solution of stone coal in one aspect produces Na2CO3or NaHCO3through the reaction of CO2with the alkali medium NaOHwhich is recycled through the causticization process from the Na2CO3orNaHCO3; in the other aspect reduces the solution pH and the silicon will deposit as precipitate when the solution turns natural or slightly alkaline while vanadium stays in solution. Consequently, the vanadium was separated from silicon in alkali solution.The thermodynamics research of the process of adding CO2to the leaching solution of stone coal indicates that the increase of the supersaturation of the silicon in solution leads to the precipitation of the silicon and the adsorption of CO2is controlled by the film diffusion.The major factors of producing carbon white from alkali leaching solution of stone coal is temperature and the final pH. Besides, certain amounts of surfactants and a secondary carbonation process improves the specific area of the carbon white product.(2)Preparation of high-quality carbon whiteVanadium in the solution didn’t influence the precipitation of silicon in the desilication carbonation process。 Vanadium in the silicon precipitates exsists in the form of V4O124-physically adsorped, the desorption of which could achieved with dilute sulfuric acid. The key to producing high-specific area carbon white is washing the precipitates with acid, which can not only purify the product but also change its pore structure and improve the specific area. The process of carbonation followed by washing with acid can produce high-quality carbon white with the specific area larger than500m2/g(3) Extracting vanadium from the week alkaline solutionIn this research, the fractional precipitation of calcium carbonate and and calcium vanadate and the extraction of vanadium were investigated to separate vanadium from the alkaline medium. In the system of sodium vanadate coexisting with sodium carbonate, Ca(OH)2can precipitate the two constituents well. Thermodynamics calculations indicated calcium carbonate precipitates first. And the key to the fractional precipitation of sodium vanadate and sodium carbonate is temperature and amount of Ca(OH)2added.In slight alkaline solution N263is a good extractant for vanadium. With N263vanadium can be efficiently recovered from the leaching solution after carbonation process and the separation of vanadium from the alkaline medium was achieved.(4) The novel technology of comprehensive utilization of vanadium and silicon from stone coalThrough tests was formed a process of comprehensive utilization of vanadium and silicon from stone coal, including controlling roast, enhancing alkaline leaching, desilication by carbonation method,extracting and enrichment of vanadium, producing vanadium and carbon white and recycling the leaching agent by causticization. The results of laboratory tests indicate the total recovery of V2O5of the complete process reached higher than75%;9t of high-quality white carbon with specific area of larger than500m2/g can be produced when It V2O5was produced;75%leaching agent of the whole process can be recycled. Efficient utilization of the silicon and the recycle of the leaching agent increase the by-product value and largely reduce the cost of the process of extracting vanadium from leaching stone coal with alkaline, andin addition of alkaline leaching’s little environmental pollution, consequently make the alkaline leaching more competitive than acid leaching.更多还原