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

为开发一种在快速流化床中利用铁粉和焦炭颗粒混合物直接还原铁矿粉的组合工艺，进行了气固颗粒行为和焦炭气化还原铁矿粉的实验研究。获得以下结果。(1)本文研究了快速流化床内气固两相的流动特性和混合特性。固体颗粒局部速度的测定表明，床层可分为两个区域，即：其中颗粒上升的核心区域和其中颗粒下降的环形区域。另一方面，局部气体速度可以用分布函数来描述，该分布函数是在颗粒上升区应用普朗特七次方根定律得到的。此外，对局部固含率空间分布的测定表明， ...更多信息 气速为2.0m/s时，床层截面上的平均含率随床层高度的增加而呈指数下降，对于两种不同尺寸和/或密度的颗粒的混合特性，在较低的固体流速下，床层底部是由粗颗粒组成的致密床层。然而，当固体率进一步增加时，粗颗粒的重量分数在整个床层高度的分布是相对均匀的，这意味着粗颗粒几乎没有偏析的趋势，即使气体速度小于粗颗粒的终端速度。(2)快速流化床铁还原特性研究在快速流化床中，以铁矿石和焦炭为原料，进行了铁还原的实验研究。气体和固体颗粒的化学分析表明，铁矿石在45 min内被氢气和一氧化碳完全还原，生成氧化亚铁，还原过程中床层也保持稳定的快速流化状态。此外，粗焦颗粒比细焦颗粒更有希望获得高浓度的还原性气体。本文阐明了一些基本问题，为铁矿石直接还原工艺的系统设计和开发提供了依据。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