钒渣钙化提钒中杂质Mn和Si的迁移行为与分离机理研究

Some problems, like serious “three wastes” and low utilization efficiency of vanadium resource, exist in the process of vanadium pentoxide production from converter vanadium slag with the traditional technology of sodium roasting and water leaching. While the cleaner process of calcified roasting followed by acid leaching for vanadium pentoxide production is promising, however, further development and application of this process is restricted by the difficulty in removing higher content impurities of Mn and Si from the acidic vanadium solution in consequent purification procedure, which brings side effects to the vanadium pentoxide quality. This project aims at study on the migration behavior and separation performance of Mn and Si impurities in the process of calcified roasting-acid leaching-chemical precipitation purification, investigating the effect of chemical and physical conditions during roasting on phases formation transformation, occurrence and migration of Mn and Si, and promoting Mn and Si to transform into insoluble or low soluble phases. The coupling mechanism of occurrences of Mn, Si and acid leaching conditions acting on dissolution performance of Mn and Si are verified. Through theoretical analysis, the stability region and phase equilibrium conditions for impurities of Mn and Si in the acidic vanadium solution medium are determined, and the principle for removing Mn and Si with precipitation is proven as well. This project combining the dissolution control with purification separation, aims to address the problem of selectively removing impurities of Mn and Si during vanadium extraction with calcified roasting process, which will provide theoretical foundation and technical guidance for further development and application of the calcified vanadium extraction process.

从转炉钒渣中生产五氧化二钒的传统工艺“钠化焙烧-水浸”存在“三废”污染严重、钒资源利用率低等问题。“钙化焙烧-酸浸提钒”是一种很有前景的氧化钒清洁制备工艺，但所得酸性钒液中杂质Mn、Si含量高，在钒液净化工序中分离困难，影响氧化钒品质，制约该工艺的发展和应用。本项目以转炉钒渣“钙化焙烧-稀酸浸取-沉淀净化”中杂质Mn、Si迁移行为与分离特性为对象，研究焙烧物化条件对钒渣熟料物相组成演变及杂质Mn、Si赋存形态和迁移的影响规律，调整焙烧条件及加入添加剂促进Mn、Si进入稀酸难溶相或低溶相；探明熟料中Mn、Si赋存形态和浸出物化条件对Mn、Si溶出行为的耦合作用机制；研究酸性钒液中Mn、Si离子的稳定区域及相平衡条件，揭示沉淀净化分离Mn、Si的机理。本项目将Mn、Si溶出控制和净化分离有机结合，旨在解决钙化提钒中杂质Mn、Si选择性分离的难题，为钙化提钒工艺发展和应用提供理论基础和技术支持。

与工业广泛采用的钠化提钒工艺制备氧化钒相比，钙化提钒在成本、环保方向体现出明显优势，然而钙化酸浸选择性差，所得钒溶液中杂质含量高，导致终产品氧化钒无法与钠化工艺产品媲美，制约了该工艺的发展与推广。本项目系统研究了钒渣钙化焙烧-稀酸浸取中杂质元素Mn、Si的赋存形态、迁移规律及溶出特性，以及酸性钒溶液中杂质Mn、Si的选择性分离。钒渣中主要含钒相为钒尖晶石相，杂质Mn在尖晶石相、铁橄榄石相和辉石相中均有分布，且在尖晶石相中含量最高。热力学计算和试验研究表明添加剂CaO2和MnO2有助于钒渣中Mn2+的氧化，而增大氧气体积比则不利于Mn2+氧化为MnO2。氧气含量在20%~100%变化对钒渣氧化反应影响不明显。在保钒的前提下控制锰硅溶出的最佳焙烧条件，即：选用碳酸钙为钙化剂，将钒渣与碳酸钙以n(CaO/V2O5）=2的比例造球，通入氧气和氮气比例为0.5mL/min:2.0mL/min。以3℃/min升高至800℃，保温时间为60min，缓冷冷却。利用硫酸调节溶液pH为2.5±0.5，在50℃的条件下浸出1h。在此条件下，钒的浸出率达到82.78%、锰的浸出率控制在28.77%、硅的浸出率控制到5%以下，XPS分析发现锰在400℃以后随焙烧温度的继续升高，Mn4+的含量减少，这是由于高温使Mn4+分解为Mn2+和Mn3+，这与热力学计算结果相符。最终通过调节焙烧条件和浸出条件可改变杂质Mn和Si的溶出行为，实现对杂质Mn、Si溶出控制，从而降低溶液净化负担。将氟化氨锰沉淀脱除杂质Ca、Mg、Al和部分Si和N235萃取+氨水反萃脱除Mn、Si相结合，可有效实现酸性钒溶液中杂质的脱除，并实现Mn资源的循环利用。将杂质Mn、Si的溶出控制和化学沉淀和溶剂萃取选择脱除杂质三者有机结合，解决了钙化提钒工艺中杂质元素Mn、Si分离困难的问题，为钙化提钒中杂质Mn、Si的低成本、高效选择性分离从而能够能到高纯度氧化钒提供了一种新思路和新途径。因此，本项目具有较高的应用前景。