Hydrodynamic Modeling of Gas-Solid Bubbling Fluidization Based on Energy-Minimization Multiscale (EMMS) Theory

Hydrodynamic modeling of gas-solid bubbling fluidization is of significance to the development of gas-solid bubbling reactors since it still remains at the stage of experimental and empirical science. As is the role of particle clusters in gas solid fast fluidization, gas bubbles characterize the structural heterogeneity of gas-solid bubbling fluidization, and their evolution is mainly subject to the constraints of the stability and boundary conditions of the system. By considering the expansion work of gas bubbles against the normal pressure stress in the emulsion phase, an improved necessary stability condition is proposed to close a gas-solid bubbling model. Applying the upgraded gas-solid bubbling model at the scale of vessels, the steady-state hydrodynamics of gas-solid bubbling fluidization can be reproduced without introducing bubble-specific empirical correlations such as for diameter and/or acceleration. The unified modeling of the entire gas-solid fluidization regime from bubbling to fast fluidization is performed by integrating the upgraded gas-solid bubbling model with the original energy-minimization multiscale (EMMS) model. Incorporating the upgraded gas-solid bubbling model into commercial computational fluid dynamics (CFD) software at the scale of computational cells, the unsteady-state simulation of gas-solid bubbling fluidization is realized with a higher accuracy than that based on homogeneous drag models.