Effect of various parameters on bubble formation due to a single jet pulse in two-dimensional coarse-particle fluidized beds

A soft-sphere discrete particle model based on re-arrangement of the gas phase governing equations has been developed to investigate the formation of a single bubble due to a central jet pulse in two-dimensional coarse-particle fluidized beds. A comprehensive study is made on the influence of bed width, particle properties and jet velocity on the bubble characteristics. The bubble grows heterogeneously when its diameter reaches one third of the bed width and elongates rapidly when its transverse size exceeds about one half of the bed width. At a given superficial velocity, a bed with a larger width leads to a decrease of gas leakage of the bubble. The influence of particle density and particle size on the bubble characteristics can be considered as the effect of the minimum fluidization velocity, which is consistent with the results obtained by two-fluid model in literature. In the presence of wall restrictions, bubble grows into an egg shape rather than an elliptical shape at detachment time when the superficial velocity is higher than the minimum fluidization velocity. Besides, a thin layer in dilute regime is observed near the top of the bed at a larger jet velocity. A bed of finer particles tends to form this layer more easily.