Simulation of hydrodynamics in gas-solid bubbling fluidized bed with louver baffles in three dimensions

Abstract

In this study, the flow characteristics of Geldart A particles in the bubbling fluidized bed with louver baffles were simulated by CFD method for the first time. A new drag model for bubbling fluidized bed with louver baffles was developed after our early work [Yang et al. Chem. Eng. J. 259 (2015) 338–347]. In this drag model, the baffled fluidized bed was treated as a series connection of freely bubbling fluidized beds with the louver baffle as the gas distributor. The hydrodynamics of each freely bubbling fluidized bed were simulated using the structure-based drag model with the modification of the bubble diameter equation to adapt the change of bubble size after passing each louver baffle. Through analyzing bubble diameters measured by double optical fiber probe, it was found that the averaged diameter of bubbles regenerated from baffles was nearly equal to the distance between two adjacent vanes in the louver baffle. By this method, the bubbling fluidization can be correctly predicted and the simulation results showed good agreements with the experimental data of the radial and axial solid volume fraction distributions. In the simulation results, it can be seen that the variation of axial solid volume fraction across the louver baffle was fluctuant, which was different from other types of baffles. Meanwhile, the lower particle concentration at the position of louver baffle indicates the particles back-mixing inhibited by louver baffles. The guiding effect of louver baffles on the gas and solid flow can be captured in the gas and solid velocity profiles as well.