ON THE INCIPIENT FLUIDIZED STATE OF SOLID PARTICLES

A comprehensive study has been reported on all aspects of the transition of packed bed to the state of incipient fluidization (point of minimum fluidization, onset of fluidization): particle size and shape, size distribution in a batch of particles, fixed bed voidage, pressure drop through a packed bed and onset of fluidization. A number of predictive equations have been compared that were proposed to estimate the minimum fluidization velocity. All the equations tested do not have any flow limitations and are applicable to laminar, transitional as well as to turbulent flow regime. While some equations have some foundation in theory, the other are more or less generalized correlations of experimental data amassed by different authors under various conditions. The influence of temperature and pressure on the minimum fluidization velocity has been explored with respect to the important applications such as combustion and gasification. Problems have also been discussed with transition from fixed to fluidized bed of binary and polydisperse systems.