CFD-DEM Coupled Simulation for Wet Particles Drying Process in a Fluidized Bed

Wet particle drying is complex due to the variation of particle moisture which has big effect on the gas-solid flow dynamic characteristics as well as mass and heat transfer between particles and particles, particles and flow. CFD-DEM simulation were employed to investigate the main characteristics in a fluidized bed drying process. Due to the computational capability restriction and computational time limit, 2D model simulation were first employed for the whole drying and then 3D model simulation was employed at certain moisture contents for more accurate flow dynamics. The simulation was based on the coupled CFD-DEM approach. The objective of this research is to further investigate the details of the wet particles flow characteristics, the heat transfer and mass transfer process of the particle drying process in a fluidized bed dryer and the effect of the particle number and the changing liquid bridge force on the particle drying process. The simulated cross-sectional particle volume fraction shows core-annular structure and is verified by the ECT measurement. An internal circulation is formed in the height direction, and the mass and heat transfer mainly happen at the lower part of the dryer and at the contact region between the bubbles and the solid phase. The results predicted by the CFD-DEM model and the TFM model are compared.