关键词: 内循环流化床, 三重环流, 多重环流, 计算流体力学

Abstract: A 2D numerical model was developed to describe the flow of liquid and gas phases in a novel triplet loop fluidized bed and multiplex loop fluidized bed,which had been developed in authors' early research.Local flow field,gas holdup distribution and liquid velocity distribution were analyzed to investigate the influence of internal loop numbers on hydrodynamic characteristics of the fluidized bed,in order to explore the best internal structure and operation factors for energy saving of fluidized bed.The simulation results showed that triplet loop and multiplex loop mostly affected the mixing of fluid from the riser and the downcomer compared with the simplex loop.Increasing internal loop number could shorten circulation distance and time consumed of the internal loop,which was beneficial to enhancing interface mixing and reaction.However the flow pattern in triplet loop and multiplex loop fluidized bed was still similar to plug flow,while microcirculation was scarely observed.Multiplex loop fluidized bed had better hydrodynamic characteristics than triplet loop fluidized bed,which meant that radial and axial homogenization of liquid velocity and higher oxygen transformation efficiency could be observed with larger internal loop numbers.This research implied that flow field reconstruction by means of structure reconstruction was favorable for the improvement of hydrodynamic characteristics,which should be one of the research and development tools of aerobic biological treatment of high organic load wastewater.

Key words: internal loop fluidized bed, triplet loop, multiplex loop, computational fluid dynamics