On the two-phase theory of fluidization for Geldart B and D particles

Knowledge of the division of gas flow between the bubble and dense phases is important for modelling and operation of bubbling fluidized beds. The two-phase theory of fluidization, which suggested that the bubble flow rate being equal to the excess gas flow above the incipient fluidization, has been proved to be an overestimation in most cases. While the two-phase theory has been modified by introducing a correction factor (Y), most previous studies were conducted for Geldart Group A powders. In the present work, the contribution to predict the parameter Y for Geldart Group B and D particles has been formulated based on almost all the available experimental data. The experimental results demonstrated that the Y value increases with decreasing particle size or density and increasing excess gas velocity. A new correlation has been developed to estimate the Y value for Geldart Group B and D particles Y = 1.72Ar(-0.133)(U-g-U-mf)(0.024) with an overall standard deviation of 19%. It only requires the knowledge of Archimedes number and excess gas velocity. This correlation is in reasonable agreement with almost all the available data in literature and the present work. (C) 2019 Elsevier B.V. All rights reserved.