生物质强化钒钛磁铁矿还原联产合成气耦合新过程的基础研究

A reserve of more than 30 billion tons of vanadium-bearing titanomagnetite in China has not been fully developed due to the lack of effective technologies in recovering of vanadium and titanium from raw ore, which has become a bottleneck constraining the comprehensive utilization of this strategic metal resource. As a clean energy and excellent reducing agent, the annual exploitable amount of biomass reaches 300 million tons of standard coal, but its utilization ratio is still less than 10%. So, typical vanadium-bearing titanomagnetite from Panxi area and biomass resources are taken to be research object in this project. Based on the goal of recycling all the elements via create mineralogical conditions for the effective downstream separation, a technical thought of titanomagnetite selective reduction coupled with biomass transformation by regulating the performance of various constituents is proposed. In order to found the theoretical foundation and technical prototype for this new coupled process of selective reduction strengthening and co-production of synthesis gas, the transformation and performance regulation mechanisms of phases, microstructure and transformation of various constituents are primarily investigated during roasting process by applying muti-disciplinary theories and methods along with various micro-testing technologies. It is believed that new theories and methods for the efficient utilization of vanadium-bearing titanomagnetite ores and biomass resources will be found, which would provide technical support for the sustainable and healthy development of steel, vanadium and titanium industry in China.

我国储量超过300亿吨以上的钒钛磁铁矿，其中共生的钒、钛资源因缺乏相应技术尚未有效开发利用，已成为我国重大特色战略金属钒钛资源多组分综合利用的瓶颈。而作为清洁能源及优质还原剂的生物质能，其年可开发量达3亿吨标煤，利用率尚不足10％。本项目针对钒钛磁铁矿固态还原铁/钒钛高效分离的难题，提出了以攀西钒钛磁铁矿和典型生物质能为对象，以全元素回收利用为目标，以创造高效分离、提取的矿物学条件为途径的钒钛磁铁矿选择性还原强化与生物质能共转化的组分性能定向调控技术思路。综合运用多学科的理论与方法，结合各种微观分析测试手段，重点研究焙烧过程中钒钛磁铁矿物相、结构、性能演变与生物质组分的共转化规律及耦合调控机制，构建生物质能强化钒钛磁铁矿选择性还原—联产合成气新工艺的理论基础和技术原型。本项目的完成可为钒钛磁铁矿和生物质资源的高效利用提供新理论和新方法，为我国钢铁和钒钛工业的绿色可持续展提供技术支撑。

本项目以我国典型的大宗战略资源钒钛磁铁矿和清洁绿色能源生物质为对象，针对钒钛磁铁矿矿相复杂、还原难度大，生物质活性好、有害元素低的特点，系统地开展了利用生物质强化钒钛磁铁矿固态还原，同时利用矿物中晶格氧对生物质组分进行资源化转化的科学研究，获得主要结论如下。生物质反应性优于传统还原煤，其热解、气化和燃烧温度更低、反应速度更快，在mol(C/Fe)=0.4、温度1100 oC焙烧30min，获得还原产物金属化率可达92.3%；此外，生物质热解形成的大量还原性挥发分也极大地促进了钒钛磁铁矿的前期还原。等温还原动力学研究表明：生物质还原钒钛磁铁矿过程前期受晶核形成模型控制，后期受二维晶核长大模型控制，表观活化能为92.3 KJ/mol，较煤为还原剂时降低约30 KJ/mol。同时，钒钛磁铁矿的加入可有效促进生物质的气化转化过程，所得气相产率72.6%，生物质C、H有效气化率分别为69.5%、60.8%。其中，气相产率较无钒钛磁铁矿添加时提高约20%，C有效气化率提高约30%。生物质的转化历程可概括为：-OH、-C=O、-C=C裂解 → -CH3裂解 → -CH 裂解→ -CO裂解，钒钛磁铁矿的加入促进了生物质内各基团的分解。采用生物质与无烟煤的复合还原剂及原料润磨预处理的协同强化技术，在mol(C/Fe)=0.8~1.0，1000~1100oC条件下共转化40~50min，可获得气相产率76.5%，C、H有效气化率分别为72.5%、62.6%，固态产物金属化率~94%的技术指标，基本实现了本项目钒钛磁铁矿与生物质资源耦合转化的预期目标。固态产物经磨选，可获得铁品位为92.7%、回收率为90.5%的铁精粉和TiO2、V2O5品位分别为42.3%、3.8%的活性富钒钛料，可分别作为后续钢铁冶炼和钒钛提取的优质原料。本项目以创造高效原子经济性转化条件为途径，以多组分回收利用为目标，综合利用多学科的理论与方法，研究了钒钛磁铁矿固态还原与生物质能高值化转化利用耦合的新理论与新技术。本项目的完成为协同实现钒钛磁铁矿资源的综合利用与生物质能的高值化利用，为我国冶金与能源工业的绿色可持续发展提供了技术支持。