Characterization of bubble behaviors in a dense phase pulsed gas–solid fluidized bed for dry coal processing

Abstract Pulsed gas–solid fluidized beds can effectively separate fine coal, and bubbles play an important role in creating suitable separation conditions. The present study performed statistical and image analyses of the evolution of bubbles in a two-dimensional pulsed gas–solid fluidized bed using a high-speed dynamic camera. The effects of apparent gas velocity, pulsation frequency and particle size on bubble characteristics and bed expansion were analyzed. The results indicate that, when a fluctuation frequency is added, the expansion height of the bed increases, the effect of attachment to the bed wall decreases, the leading diameter and rising velocity of the bubbles both decrease and the degree of bubble deformation increases. These trends are also more obvious for fine particles. These findings demonstrate that a high density pulsed gas–solid fluidized bed can effectively combine gases and solids to produce a uniform, stable mixture. The bubble diameter and rising velocity were also simulated in the present work, and the relationship between the two was established using a fitting model with an error within 5%. This model provides an effective means of predicting bubble velocity as well as studying the distribution of the bubble phase and improving the stability of the bed density.