Towards a general correlation for minimum fluidization velocity in gas-fluidized beds: Based on a database mining from the literature

As one of the most significant parameters in fluidized beds design and operation, the minimum fluidization velocity (Umf) has received utmost attention since 1940s. As an effective reference for evaluating the fluidization characteristic, Umf is conventionally predicted using the empirical correlation developed based on experiments for the specified gas-solid system. Despite more than 100 correlations proposed in the literature, these correlations show great diversity in either the applicable regimes or the mathematical formulae. Thus a general correlation for accurately determining Umf is highly desired. In this work, with a recently established database of Umf mined from published papers, the empirical correlations with four different formulae were first assessed for Geldart Groups A, B, and D particles, respectively. In view of the application limitations, modifications to different formulae of empirical correlations have been made to achieve satisfactory performances in predicting Umf for either Geldart Groups A, B, or D particles. Note that Umf is essentially determined by the balance between the gravitational force and drag force for a gas-solid system, a new formula based on a fluidized bed drag correlation derived from direct numerical simulations (DNS) was proposed. By using this formula, we developed a general correlation for Umf in gas-fluidized beds, which exhibits the best performance for all Geldart Groups A, B, and D particles when compared with empirical correlations reported in the literature.