Residence Time Study Of A Bubbling Fluidized Bed Based On Reduction Of Limonite

As the highest magnetic roasting reactor, the fluidized bed plays an important rolein the magnetic roasting techniques. The fluidized bed promotes complex refractory oreefficient use, and improves the efficiency of low-grade iron ore resources. In thefluidized bed roasting process, roasting time (residence time) is an important factor inthe extent of the reduction of low-grade iron ore. If the residence time is too long, orewould occur roasting phenomenon over. If the residence time is too short, ore wouldproduce less reduction reaction. Therefore, understanding the particle residence timedistribution in the fluidized bed for comprehending and controlling magnetic roastingreaction process is necessary.In this paper, particle in the fluidized bed with Inner-vertical Partition Plates wasour research object. And we tested its residence time, discussed the relationship betweenthe residence time and the magnetization roasting process. There are three verticalpartition plates which divided the fluidized bed into different areas. This could promoteexchange of old and new material, heat in different fluidizing regions progressively, andachieve the optimum calcination temperature in the outlet section area. This couldeffectively improve the mass and heat transfer between the gas and solid, and improvethe conversion rate and yield of the reaction product.In the experimental study of particle residence time, we used quartz glass beads asbed materials, researched particle residence time by the mean residence time and thepulse method. On the basis of cold position experiment device, the influence of feedrate, superficial gas velocity, particle size and inner-vertical partitions on the residencetime has been studied. Results showed that the feed rate and the superficial gas velocitywere the main factors of the residence time. The average residence time decreased withfeed rate and the superficial gas velocity increasing. When the feed rate reached acertain value, the residence time kept constant and it depended on the change of superficial gas velocity. Within a certain range, it was a fixed linear relationship amongthe three. The particle size and the height of middle inner-vertical partition affected little.While the height of the flow-through reached a certain height, they almost had no effecton the residence time. By the pulse method, according to magnetization reductionroasting of limonite in a fluidized bed，using vertical partition plates in fluidized bedcould reduce dead region and short circuit condition. The fluidized bed withInner-vertical Partition Plates enhanced mixing intensity. Results showed that RTD wasmore average with increasing of superficial gas velocity. However, the superficial gasvelocity increased deviation from the average residence time. With increasing ofparticle size and feed rate, RTD was dispersed. The result could provide theoreticalbasis for the residence time of solid particles and using inner-vertical partition plate inthe bubbling fluidized bed.