铁矿粉流态化还原中铁的析出形态与粘结行为研究

The stability is an important precondition of the technology for industrial applications in the process of iron ore fluidized pre-reduction. A lot research for relevant factor of stability is carried out at home and abroad, but have some difference in understanding mechanism of adhension agglomeration. It is widely believed that iron separating morphology and growth have a significant effect on sticking agglomeration. Base on the experimental facility modified visual situ observation combined metallurgy thermodynamics and kinetic theory, in this project, the physico-chemical behavior at gas-solid interface are mainly researched in the process of iron ore fluidized pre-reduction, the growth characteristics of iron crystal /whisker are simulated and analyzed, the mechanism model for separating morphology of metallic iron are improved. Applied the mechanism model combined the results of situ observation, the microstructure on the surface of disperse iron ore particle and the evolution law of separating morphology of metallic iron are studied. The gas composition, temperature, time, vein stuff, additive and charcoal preprocessing effect on iron crystal / whisker growing morphology and rate and co-action mechanism. Mainly, the adhesion, bridging mode, co-action law and control method between iron ore particles are verified in this project. Based on these researches,the thermal state experiment of controlling cohere phenomena of among iron ore particles in fluidized reduction are carried. All of which will contribute to provid theoretical reference and practical guidance for controlling sticking aggregation and unstability among iron ore particles in the process of fluidized reduction.

铁矿粉流态化还原过程的稳定性是该技术获得工业应用的重要前提，国内外对影响稳定性的相关因素进行了大量研究，但仍未解决且在机理认识上尚存分歧。普遍认为铁析出、长大对铁矿粉的粘结团聚有重要影响。本项目以改进的可视化的原位观察实验装置为基础，结合冶金热力学和动力学理论，重点开展流态化还原中气固两相界面物化行为研究，对铁晶（须）的生长特征进行模拟分析，改进铁矿粉表面铁析出形态的机理模型；应用该机理模型，结合原位观察结果，研究离散矿粉颗粒表面微结构、金属铁的析出形态演变规律；考察流态化还原过程中气体组成、温度、时间及脉石成份、添加剂、附炭预处理等对铁矿粉表面新生铁晶（须）生长状态、生长速度的影响和作用机制，重点探明铁矿粉颗粒间铁晶（须）的粘连、桥接方式、相互作用规律及调控方法；在此基础上，进行控制铁矿粉流态化还原粘结现象的热态实验研究，对控制铁矿粉在流态化还原中的粘结失稳，提供理论参考和实际应用指导。

铁矿粉流态化还原过程的稳定性是该技术获得工业应用的重要前提，国内外对影响稳定性的相关因素进行了大量研究，但仍未解决且在机理认识上尚存分歧。普遍认为铁析出、长大对铁矿粉的粘结团聚有重要影响。本项目重点开展了流态化还原中气固两相界面物化行为研究，采用第一性原理计算方法，研究了还原气体CO和H2在铁氧化物表面的吸附反应的微观机理、对新生铁及其微观结构形态的影响，以及掺杂Ca2+、Mg2+、附碳等的微观作用机理；采用相场和元胞自动机模拟的方法，建立了FeO和有空位缺陷的浮士体表面新生铁析出形态的机理模型；以Fe2O3粉粒和实验制得的片状Fe2O3粉粒为例，通过原位观察实验对Fe2O3在还原过程中表面形貌的演变和铁晶须的形成、生长和粘结过程进行了研究；通过流化床还原、热分析、粘结后强度、形貌特征等系列分析，建立了表面铁析出的形态、生长和粘结特征关系，结合利用耦合了还原反应的Euler-Euler模拟计算方法，模拟了铁氧化物颗粒在流态化直接还原过程中流动行为以及粘结失流的发生过程，研究了流态化还原过程中铁矿粉颗粒的粘连和桥接作用机制。在上述研究的基础上，利用流态化还原热态实验平台，进行了散状Fe2O3颗粒、掺混CaO和MgO和600℃预处理附碳的Fe2O3颗粒在不同温度、不同气氛（CO，H2和CO/H2混合气体）和时间条件下的系列流态化还原实验研究，结合原位观察和还原后的XRD、SEM & EDS等分析检测，研究了抑制铁晶生长和粘结现象的控制效果，提出通过调控CO/H2中H2分压pH2、附碳等方法控制表面新生铁的形态和粘连，对控制铁矿粉在流态化还原中的粘结失稳，提供了理论参考和实际应用指导，对工艺参数的优化和反应器的设计具有重要意义。