The fluidization property of ultrafine particles is closely related to their agglomerate size. Through the analysis of the formation process of ultrafine powder agglomerates in an acoustic spouted fluidized-bed with a draft tube

it is proposed that the shearing action of high speed jet and collision between agglomerates were the dominating factors to influence agglomerate size. Based on the force balance analysis acting on the agglomerates during the jet shearing process and collision between agglomerates

a model to predict agglomerate size distribution in an acoustic spouted fluidized-bed with a draft tube was established. The average size of agglomerates and their size distribution of TiO2 ultrafine powder at different jet velocities in the bed were predicted by the model successfully.