Improvement And Simulation Of The Separate-phase-coexistence Model For Fast Fluidization Dynamics

The gas-solid flows in fast fluidized beds(FFB)are complex,which can be influenced by many parameters.Due to the remarkable pregresses of theoretical researches and engineering practices,the fast fluidized beds have have been used widely.However,most of the existing researches and practices are isolated,which makes people can not fully understand the complex mechanics of gas-solid flows and related dynamic characteristics in fast fluidized beds.In addition,based on the existing theory and practical experience,it is still difficult to make a lager-scale application of the fast fluidized beds.Therefore,it is important and useful for a model to correlate the dynamic parameters in fast fluidized beds.In this paper,the established theory of the separate-phase-coexistence model for fast fluidization dynamics is tested and analysed by making comparisons between the predicted data calculated by this model and the accurate experimental data collected by other researchers.The results show good accuracy and reliability for this model.In addition,the separate-phase-coexistence model for fast fluidization dynamics is further improved and optimized through mechanistic analysis and experimental comparisons,making it more reliable and accurate in this paper.These improvements include the value of the minimum fluidization voidage,the relationship between the gas velocity and bed voidage in fluidized bed,the correlation for prediction type A chocking,the friction faction correlations,and the gas penetrating velocity in the inner of the clusters.Finally,based on the separate-phase-coexistence model for fast fluidization dynamics,the effects of the gas-solid characteristics and the operating conditions on the solids holdup in the dilute upper side of the fast fluidized beds are discussed,including the solids diameter,the solids density,the riser diameter,the circulated solid flux,and the fluidization velocity.