Eulerian-Eulerian simulation of irregular particles in dense gas-solid fluidized beds

As an important and essential physical property, particle shape affects fluidization characteristics of dense gas-solid fluidized beds greatly. However, numerical studies of irregular particles in gas-solid fluidization, especially using Eulerian-Eulerian model, are relatively scarce, primarily due to the lack of an appropriate inter-phase drag model. To this end, a simple and effective drag model was proposed in this work to address the critical role of particle shape in determining the inter-phase drag force. This drag model features the usage of Ganser correlation and Ergun correlation, respectively, in dilute and dense solid concentration conditions. Moreover, particle sphericity is introduced as a concise shape descriptor, and can be calibrated by experimentally measured minimum fluidization velocity and the corresponding voidage. To verify the established numerical model, experimental study was also conducted in a lab-scale three-dimensional rectangular bed filled with irregular Geldart group B particles. Other two kinds of irregular bed materials from open literature were investigated as well to provide further validation. The predicted results using the proposed drag model are overall in relatively better quantitative agreement with the experimental data or available empirical correlations, in terms of both macro-scale and micro-scale behavior. In contrast, the numerical model with the drag force assuming perfectly spherical particles completely fails to reproduce the experimental hydrodynamics of the gas-solid fluidized bed. In addition, sensitivity analysis of the proposed drag model demonstrated its weak sensitivity to the minimum fluidization characteristics of particles. The sufficient comparison and analysis indicated that the proposed drag model together with the estimation method of particle sphericity is quite reasonable and convenient for Eulerian-Eulerian simulation of irregular particles behavior in lab-scale dense gas-solid fluidized beds. (C) 2015 Elsevier B.V. All rights reserved