铁矿悬浮焙烧炉U型还原腔内气固两相流动特性及蓄热还原机理研究

Iron ore suspension roaster is a new generation of high efficiency and clean magnetizing roasting equipment, which could realize the efficient utilization of complex refractory iron ore. Reduction chamber is the key device of suspension roaster, and it is of great theoretical and practical significance to study the new structure of the reduction furnace chamber and the basic scientific problems during its operation..The principle of heat accumulating reduction in iron suspension flow field is proposed in the project, and the U type reduction chamber with dual functions of reduction and seal is designed. That is to say, iron ore is heated only in the main furnace chamber, after that the heated iron ore flows through the cyclone separator into the U type reduction chamber, then iron minerals is reduced by their own accumulating heat in the suspension flow field of the U type reduction chamber. The characteristics of gas-solid flow, temperature distribution, mineral evolution regularity and heat reduction mechanism of suspension flow are investigated in detail through cold test, numerical simulation, heat accumulating reduction and micro fluidized bed coupled with mass spectrometry experiment. The project aims to find out the flow characteristics of iron ore particles and gas, and establish the multi factors coupling control mechanism of heat accumulating reduction and magnetic separation. The precise control of iron mineral phase transformation will be achieved, and the concentrate with iron more than 65% and recovery more than 85% also will be obtained. These works will solve the fundamental scientific problems in the industrial enlargement and process control of the U type reduction chamber, and provide theoretical support for the development and safe operation of industrial scale suspension roaster.

铁矿悬浮焙烧炉是新一代高效清洁磁化焙烧装备，可实现复杂难选铁矿石的高效利用，还原腔是悬浮焙烧炉的核心装置，研究还原腔新型结构及其运行过程中的基础性科学问题具有重要的理论与实际意义。.本项目提出铁矿石悬浮流场中蓄热还原技术原理，设计兼具还原和密封双功能的U型还原腔，即铁矿石仅在主炉腔进行加热，高温铁矿石经旋风分离器进入U型还原腔，铁矿物在U型还原腔悬浮流场中利用矿石自身储蓄热量进行还原。通过冷态及数值模拟、蓄热还原和质谱耦联微型流化床试验，重点研究U型还原腔内气固两相流动特性、温度场分布、矿物演变规律及悬浮流场中蓄热还原机理等内容，探明U型还原腔内矿石颗粒和气体流动特性，建立蓄热还原-磁选多因素耦合调控机制，实现对铁物相转化的精准控制，获得铁精矿TFe品位>65%、回收率>85%的指标，解决制约U型还原腔工业放大、过程控制的基础性科学问题，为大型工业悬浮焙烧炉的研制及安全运行提供理论支撑。

铁矿悬浮焙烧炉是新一代高效清洁磁化焙烧装备，还原腔是悬浮焙烧炉的核心装置，研究还原腔新型结构及其运行过程中的基础性科学问题具有重要的理论与实际意义。本项目采用冷态试验、热态试验、数学建模和数值模拟相结合的研究方法，系统开展了U型还原腔冷态试验、气固两相流动数值模拟、悬浮流场中蓄热还原动力学及矿物演变规律等机理研究，取得一些具有重要科学意义和参考价值的研究成果。.基于U型还原腔物理结构，自行研发了U型还原腔冷态试验系统，探明了操作参数对U型还原腔内气固流动特性的影响规律，建立了U型还原腔气固流动数学模型，并采用Fluent数值模拟软件仿真了U型还原腔的运行过程，阐明了不同因素作用下矿石颗粒和气体的流动规律。.U型还原腔内悬浮流场中铁矿物演变规律及蓄热还原机理研究表明，赤铁矿向磁铁矿转化过程的控制步骤为新相磁铁矿晶核形成及生长环节，新生磁铁矿晶核呈致密针状，还原过程产生的应力（体积膨胀约10%所致）促使赤铁矿-磁铁矿相界面形成微细孔道，致使磁铁矿颗粒微观呈多孔状。赤铁矿向磁铁矿还原转化的机理函数可用Avrami-Erofeev方程F(α)=[-ln(1-α)]1/n（n=1.5~1.58）描述，即赤铁矿的还原磁化过程由磁铁矿相的随机成核及一维（1D）生长模型控制。反应活化能Ea=48.70~49.64kJ/mol，指前因子A=5.58~6.55s-1。.以东鞍山预富集精矿为研究对象，系统研究了铁矿石在U型还原腔中磁化过程，阐明了该过程中赤铁矿、菱铁矿和磁铁矿的热力学行为，形成蓄热还原-磁选全流程多因素调控机制，实现U型还原腔内铁物相转化的精准控制，获得铁品位66.06%、铁回收率90.22%的优异指标。并将该U型还原腔成功应用于3000吨/年、60万吨/年和165万吨/年工业装备，完成鞍钢、酒钢、辽宁三和、塞拉利昂、阿尔及利亚等多个国家20余种矿石应用。.综上所述，本项目发明了非均质颗粒流态化U型蓄热还原反应器，探明了U型还原腔内气体流动特性和矿物演变的影响规律，解决了制约U型还原腔工业放大、过程控制的基础性科学问题，为大型工业化悬浮焙烧炉的研制和安全运行提供理论支撑。