A model for predicting the segregation directions of binary Geldart B particle mixtures in bubbling fluidized beds

Abstract

In gas fluidization processes involving different types of particles, the mixing or segregation behavior of the solid mixture is crucial to the overall outcome of the process. This study develops a model to predict the segregation directions of binary mixtures of Geldart B particles with density and size differences in bubbling fluidized beds. The proposed model was established by combining the particle segregation model, a previous particle segregation model, with a derived bed voidage equation of the bubbling fluidization based on the two-phase theory. The model was then analyzed with different function graphs of the model equations under various conditions. The results indicated that an increase in gas velocity or volume fraction of larger particles would strengthen size segregation, causing the larger and less dense components to descend. To validate the model, 42 sets of data collected from 6 independent literature sources were compared with the predictions of the model. When the gas velocities were below 3.2 times the minimum gas velocity, the predictions were consistent with experimental results. This study has shed new light on the mechanisms of particle segregation in binary fluidized systems and provides a theoretical foundation for designing and manipulating gas-solid fluidized reactors.