Powder Technology, Vol.365, 28-38, 2020
A conceptual model for analyzing particle effects on gas-liquid flows in slurry bubble columns
Particles play significant roles in the flow structure of gas-liquid flows in slurry bubble columns. The Dual-Bubble-Size (DBS) model based on the Energy-Minimization Multi-Scale (EMMS) approach has been developed to characterize gas-liquid flows by incorporating a stability condition in our previous work. A Particle-dependent Dual-Bubble-Size (PDBS) model is thereby developed in this work to analyze the different particle effects on gas-liquid flows. The particle effects on apparent properties of liquid phase and drag coefficients of bubbles are considered for systems of wettable particles. The model calculation indicates that the regime transition is delayed due to the increase of apparent density and viscosity. On the other hand, the particle effect on bubble drag coefficients decrease the gas holdup. The PDBS model taking account of both the effects can reproduce the decrease of gas holdup and energy consumption of bubble breakage arising from the increase of solid concentration. A new drag model is then derived from the PDBS model for CFD modeling. The CFD predictions of gas distribution under high solid loadings are in conformity with experimental data. The particle effect on stabilizing bubble surface is also analyzed for systems of non-wettable particles. The model reflects the increase of gas holdup with addition of non-wettable particles, and reveals also that small bubbles may dominate the system in such cases. (C) 2019 Elsevier B.V. All rights reserved.