基于闪速还原焙烧过程难选铁矿中铅锌杂质的演变迁移机制研究

Lead and zinc were harmful impurities in iron-making raw materials. As they were easily reduced and expanded after oxidation in the blast furnace, lead was drowned beneath the iron layer and zinc was transformed zinc-bearing dust and sludge, which the production processes of blast furnace were seriously affected. Owing to lead-zinc-iron complex dissemination and very fine particles in refractory iron ore, the minerals containing lead and zinc impurities are changeable in high temperature conditions and difficult to remove them. .The subject will select to some typical lead-zinc containing refractory iron ore in the Xinjiang Uygur Autonomous Region of China and the corresponding lead and zinc minerals. There are both technology and device on flash reduction roasting to refractory iron ore by means of NI Labview control methods and online spectrum analysis. The project aims to investigate migration characteristics and the conversion relationships between pyrolysis and reduction process on lead and zinc impurity minerals during flash reduction roasting. In the beginning, the relationships of lead and zinc three-phase transformation and evolution, migration regularity on high temperature pyrolysis reactions based on flash reduction roasting will be determined. Secondly, the reaction kinetics during pyrolysis reactions will be studied, and the related kinetics coefficients will be calculated to typical lead and zinc impurity minerals. Furthermore, lead and zinc impurity transferring trajectory will be drawn by investigating the lead and zinc occurrence in the flash reduction roasted products and the relationships between lead-zinc-iron distribution. The researches will provide the fundamental understanding of iron ore by flash reduction roasting, which will benefit to control lead and zinc impurities if developing lead and zinc containing refractory iron ores in the future.

铅锌在炼铁中是有害杂质，易被还原或氧化后膨胀，并形成含铅沉淀和含锌尘泥，严重影响高炉生产。赋存于铁矿中的铅锌，形成铅-锌-铁嵌布关系复杂、颗粒微细，高温时矿相多变而难以去除。以新疆典型含铅锌难选铁矿和对应的铅锌矿物为对象，应用闪速还原焙烧技术装置及测试平台，借助NI Labview测控手段和在线光谱分析方法，围绕铅锌杂质在闪速还原焙烧条件下的相态转化和迁移特性，明晰闪速焙烧过程中铅锌的相态演变与迁移机制；查明焙烧产品中铅锌的赋存状态，揭示铅-锌-铁的嵌布关系和转变规律；探索典型铅锌杂质矿物闪速焙烧过程的动力学特性，确立铅锌矿物焙烧过程参数，建立铅锌闪速焙烧过程动力学，为开发该类矿产控制铅锌杂质提供理论支撑。

铅锌是重要的有色金属，但在炼铁中是有害杂质，易被还原或氧化后膨胀，并形成含铅沉淀和含锌尘泥，严重影响高炉生产；同时，铅锌也是重金属污染元素，易威胁人类和生物的生存环境。赋存于铁矿中的铅锌，形成铅-锌-铁嵌布关系复杂、颗粒微细，高温时矿相多变而难以去除。.全面总结和归纳了铅锌及铅锌矿物在冶金还原过程相态演变与特性、评析铅锌在高炉炼铁中的循环过程与影响；以新疆和静含铅锌难选铁矿和对应的铅锌矿物为对象，查明了含铅锌难选铁矿的矿物学性质及铅锌产出特征，实现了含铅锌难选赤褐铁矿还原焙烧及铅锌杂质同步脱除，明晰了还原焙烧过程中铅锌的相态演变与迁移机制；查明了焙烧产品中铅、锌、铁及硫的赋存状态、产出特征与相态变化，揭示了铅-锌-铁的产出形貌、嵌布关系和还原转变规律；研究了典型铅锌杂质矿物还原焙烧反应过程和动力学特性，确立了铅锌矿物焙烧过程参数，获得了高质量铁精矿和可作为电炉炼钢的铁原料。拓展研究了铜渣中还原焙烧过程铅锌挥发、金属铁析出与富集、含铁橄榄石和磁铁矿的固态碳热还原综合利用方法及相关制品应用。.针对含铅0.39%、含锌0.30%、全铁(TFe)47.04%的难选赤褐铁矿，其中90.32%的铅以氧化铅和铅铁矾的形式存在，90.60%的锌以氧化锌的形式存在；采用深度还原焙烧方法可将赤褐铁矿深度还原成金属铁颗粒，同时有效地脱除其中的铅锌杂质；当还原剂碳氧比(C:O)=2.25、还原焙烧温度1200℃、还原焙烧时间为60 min时，还原产品经弱磁选后的精矿铁品位为89.63%，铁回收率达86.09%，铅、锌杂质的脱除率为98.97%和91.19%，且水淬过程对铅锌脱除率为0.612%、1.056%。在1200℃的焙烧产品中可见大量细小、椭圆粒状、表面光滑的金属铁或自然铁颗粒，微区点含铁纯度可达99.4%以上。焙烧产物中铅锌杂质残留仅为Pb 0.0064%、Zn 0.0295%，其微区特征未见残余的铅锌有害杂质。铁矿还原焙烧过程符合收缩边界控制反应机理和收缩球体模型，表观活化能为91.37 kJ·mol-1，指前因子A为18.09 min-1，还原反应速率控制环节为固相扩散。研究成果对含铅锌铁矿的开发具有重要指导作用。