PDF《博士学位论文公示材料》

1523 K,还原时间

50 min,C/O 摩尔比 2.0,CaO 用量 ―2― 6%.制备出的还原物料经分选,达到了铁粉品位 89.86%、铁回收率 96.04%、金属化率 97.46%、磷品 位1.74%、磷回收率 64.27%的良好指标.富磷铁粉特性分析表明,酸性杂质和有害元素硫的含量较低. 若采用脱磷炼钢技术对其进行冶炼,得到钢材的同时,还将获得 P2O5 含量高于 10%的脱磷钢渣,为磷 元素回收利用创造了条件. 本文的研究成果加深了对高磷鲕状赤铁矿深度还原过程的认识,丰富了难选铁矿石深度还原理论 体系,不仅对突破高磷鲕状赤铁矿深度还原的关键技术难题提供理论支撑,对其它复杂难选铁矿石的 高效利用也具有良好的借鉴意义. ―3― 论文摘要(英文) High-phosphorus oolitic iron ore is considered to be one of the most refractory iron ores in the world due to its complex mineral composition, ultrafine-grain iron minerals, high phosphorous content and unique internal structure. Coal-based reduction has recently proven a feasible way to recover metallic iron from high-phosphorus oolitic iron ores. However, most of the existent studies only examined the reduction and magnetic separation conditions, and little research focused on the key scientific issues in the reduction, such as thermodynamics and kinetics mechanisms, phase and microstructure evolution, metallic phase formation and growth, phosphorus interphase transfer, and so on. Consequently, in order to solve the above problems, the coal-based reduction of a high-phosphorus oolitic iron ore collected form Guandian iron mine, Hubei Province, China were investigated using scanning electron microscope (SEM), X-ray diffraction analysis (XRD), electron probe microanalysis (EPMA), etc. A systematical study was carried out by theoretical analysis, experimental researches and computing simulation, and some achievements, having obviously scientific and technological significance, were obtained. The investigations on thermomechanical analysis, phase transformation and microstructure evolution indicated that the process of coal-based reduction of high-phosphorus oolitic iron ore is extremely complex, it not only including phase transformations of the minerals, but also microstructure evolution of the ore. Iron minerals was reduced to metallic iron along the chemical reaction sequence of Fe2O3→Fe3O4→FeO (Fe2SiO4, FeAl2O4) →Fe and the spatial sequence from the outer layer within the particle to its inner core. Impurities such as SiO2, Al2O3 and CaO formed slag phase along the sequence of Fe-Al-Si-O→Fe-Ca-Al-Si-O→Ca-Al-Si-O. The micro oolitic structure of the ore was gradually destroyed starting from the outer layer to the inner layer, and the evolution process could be divided into the marginal, internal, and entire destruction three stages. Based on these findings, a simplified model was proposed to describe the coal-based reduction of high-phosphorus oolitic iron ore. The observations of kinetics revealed that the reduction mechanisms changed as the reduction progressed. At the early stage, Fe2O3, Fe3O4 and FeO were reduced to metallic iron in a stepwise manner, and the reduction is controlled by interfacial chemical reaction. At the later stage, FeAl2O4 and Fe2SiO4 were the main phase that was reduced to metallic iron, and solid-state diffusion is the reaction determining step. The isothermal reduction process could be divided into three stages (namely, the initial stage, middle stage and final stage), and the mechanism functions for these three stages were f(α)=4(1?α)[?ln(1?α)]3/4 , f(α)=(1?α)2 (C/O molar ratio of 1.5 and 2.0) and f(α)=2(1?α)3/2 (C/O molar ratio of 2.5 and 3.0), and 3/2(1?α)4/3 [(1?α)?1/3 ?1]?1 . The most probable mechanism function for non-isothermal reduction was chemical reaction model f(α)=3/2(1?α)2/3 [1?(1?α)1/3 ]?1 . Based on the determined mechanism functions, the corresponding apparent activation energy and pre-exponential factor were obtained, and the reduction kinetic models of oolitic iron ore by coal were proposed. The researches on formation and growth of metallic iron particle showed that the generated iron atoms firstly separate out in the surface of the ore particle and formed tenuous metallic protuberance in irregular shape, which would beco........