含能废弃物-煤复合含碳球团固结机理与强度控制研究

As possessing good self-reduction performance, Carbon-bearing pellets provide many possible opportunities upon energy conservation and emission reduction in metallurgical industry. But the lower strength of the pellets can’t satisfy the requirements of efficient productivity. Our previous study shew that the partially addition of energy-bearing waste, such as plastics or rubbers, could obviously improve the strength of dried pellets. The dissociation product and fine coal could work synergistically to enhance iron oxides reduction. Particle morphology, physical and pyrolysis properties exhibit significant influences on the strength of green ball, dried and reduced carbon-bearing pellets. By studying the consolidation mechanism and the strength controlling of composite carbon-baring pellets with partially addition of energy-bearing waste, this project will focus on exploring the influences of the physical and thermoplastic characteristics of these pellets on strength of green balls and dried pellets, investigating the coupling effects of carbon gasification and the reduction of iron oxides, revealing the relationships among reduction strength and the after-reduction structure, iron occurrences and iron grain growth of pellets. The consolidation mechanism and strength controlling of composite pellets will be discussed and put forward. The implement of this project will supply theoretical and technical support for further utilization of carbon bearing pellets with energy-bearing waste.

具备良好自还原性的含碳球团为冶金工业节能减排提供了多种可能，但其强度难以满足高效生产要求。申请者研究发现，在含碳球团中添加一定比例粉状塑料、橡胶类含能废弃物能有效提升球团干燥强度，同时，其裂解产物可与煤粉协同强化还原铁氧化物。而含能废弃物的颗粒形貌、物化性能以及热解特性等对含碳球团制备、干燥和还原各阶段强度有较大影响。因此，本项目拟通过含能废弃物-煤复合含碳球团固结机理与强度控制研究，探索含能废弃物-煤混合体系的物性特征和热塑性能对球团生球和干燥强度影响规律，查明混合体系作用下碳气化与铁氧化物还原的耦合效应，揭示含碳球团结构特征、铁元素赋存状态和铁连晶生长与还原强度的内在联系，阐明含能废弃物-煤复合含碳球团固结机理，确立含能废弃物-煤复合含碳球团强度控制机制。项目的实施可为含能废弃物用于含碳球团生产提供理论依据和技术支持。

直接还原炼铁技术是有效解决优质矿焦资源日趋匮乏，保持钢铁工业可持续发展的重要途径。具备良好自还原性的含碳球团为冶金工业节能减排提供了多种可能，由于含碳球团原料构成与人造富矿显著不同，球团强度难以满足高效反应器生产要求。本项目通过对含能废弃物/煤复合含碳球团固结机理与强度影响因素的系统研究，揭示了含碳球团高温还原过程中热态强度变化与其物理结构、铁元素赋存状态的内在联系，提出了基于原料脉石组分优化与适宜功能性粘结剂相配合的含碳球团热态强度优化途径，为含能废弃物用于含碳球团生产提供理论依据和技术支持。同时较为系统地阐述了含能废弃物/煤复合含碳球团原料颗粒间主要作用力对球团冷态强度的影响、微热压含能废弃物/煤含碳球团性能、含能废弃物/煤混合体系还原铁氧化物的协同关系、脉石组分变化对铁氧化物还原过程与机制的影响等，建立了基于两步还原理论的单个含碳球团还原过程二维非稳态数学模型。研究表明：(1)热塑性含能废弃物与无烟煤共混能够降低无烟煤碳气化反应激烈温度，加快反应进程，存在明显的协同作用，而废弃橡胶与无烟煤共混碳气化过程不存在协同作用。(2)无粘结剂含碳球团冷态强度主要受毛细作用和啮合作用控制，碳质还原剂显著降低颗粒间啮合作用是含碳球团冷态强度差的根本原因。(3)含碳球团热态强度水平取决于其内部结构特性和颗粒间作用力。200℃-1000℃，球团热强度由颗粒间啮合作用和粘结剂胶结作用控制，高于1000℃后，维系球团热态强度主要作用力来源于球团内金属键和离子键新生相的生成与聚集。以2%热塑性含能废弃物或5%橡胶替代部分煤粉，有利于含碳球团冷态强度的提升，并可明显改善含碳球团在1000℃-1050℃热态承载能力。通过本项目研究，共发表学术论文9篇，其中SCI/EI收录6篇，中文核心期刊1篇，会议论文2篇。授权国家发明专利6件。培养硕士研究生6人。学术成果、人才培养等均完成了预期目标。