Development of Direct Iron-Ore Reduction Process Using Fast Fluidized Bed

本项目的目的是开发一种利用细铁和炭颗粒的混合物在快速流化床中直接还原细铁矿石的组合工艺。为此，对气体和固体颗粒的行为以及煤焦气化对铁矿石的还原进行了实验。得到了以下结果：(1)快速流化床内气固两组分颗粒系统的流动特性及混合特性。对流化床局部固体颗粒速度的测量表明，流化床可分为两个区域，即颗粒上升的核心区域和颗粒下降的环形区域。另一方面，局部气体速度可以用粒子上升区域的普朗特七次根定律得到的分布函数来描述。此外，对局部固含率的空间分布测量表明，在2.0m/s以上的气速下，两者的分布相似，且床层截面上的平均含率随床层高度呈指数递减。对于两种不同粒径和（或）密度的颗粒的混合特性，在相对较低的固相率下，在床底观察到致密的粗颗粒床。当固相率进一步增大时，粗颗粒质量分数在整个床层高度上的分布较为均匀，表明尽管气速小于粗颗粒的终速，但粗颗粒的偏析倾向较小。(2)快速流化床铁还原特性研究了在快速流化床中利用铁矿粉与炭颗粒混合还原铁的实验。气体和固体颗粒的化学分析表明，铁矿石被氢和一氧化碳完全还原，在45分钟内形成乌氏体（FeO）。在还原过程中，还发现床层保持稳定的快速流化状态。此外，粗炭颗粒比细炭颗粒更有希望获得高浓度的还原性气体。为了给系统设计和直接铁矿还原工艺的开发提供依据，阐明了许多基本问题。少

The objective of this project is to develop a combined process for direct reduction of fine iron ore by using mixture of fine iron and char particles in a fast fluidized bed.For this purpose, experiments were carried out both on the behavior of gas and solid particles, and on the reduction of iron ore by char gasification. The following following results were obtained.(1) Flow behavior of gas and solid particles and mixing characteristics of the two components particle system in a fast fluidized bedMesurements of the local solid particle velocity showed that the bed could be divided into two regions, i.e., a core region in which particles ascended and an annular region in which particles descended. On the other hand, the local gas velocity could be described with the distribution function which was obtained by applying Prandtl's 7th root law the particle-ascending region. in addition, the measurement of spatial distribution of local solid holdup revealed that the distributions above a … More gas velocity of 2.0m/s were similar, and that the holdup averaged over the bed cross-section decreased exponentially with the bed height.Concerning the mixing characteristics of two species of particles with different sizes and/or densities, a dense bed of coarse particles in the bed bottom was observed at a relatively low solid rate. When the solid rate was further increased, however, the profile of weight fraction of coarse particles throughout the bed height was relatively uniform, implying that coarse particles had little tendency of segregation, even though gas velocity was smaller than the terminal velocity of a coarse particle.(2) Characteristics of iron reduction in a fast fluidized bedThe experiments were conducted on the iron reduction using the powder mixture of iron ore and char particles in a fast fluidized bed. Chemical analysis of gas and solid particles showed that iron ore was completely reduced by hydrogen and carbon monoxide, forming Wustite(FeO) within 45 minutes.During reduction, the bed was also found to be kept at stable fast fluidizing state. In addition, the use of a coarse char particle was more promising than a fine char particle to obtain high concentration of reducing gas.To provide a basis for both the system design and the development of direct irom-ore reduction process, many fundamental aspcts were clarified. Less