3-D CFD Simulation of Oil Shale Drying in Fluidized Bed and Experimental Verification

Fluidized bed drying is an economical and high-efficiency deep pre-dehydration technology for oil shale. The mature fluidized bed drying technology, which intensifies the retorting process, was applied to oil shale particles of high moisture content. The main objective of this paper was to explore the 3-D computational fluid dynamics (CFD) numerical simulation and experimental verification of oil shale particles drying in a fluidized bed. The Eulerian modeling incorporating the kinetic theory for granular particles coupled with the k-s turbulence model was developed. The modeling utilized the drying model with a user-defined functions (UDE) for the simulation. The effects of the specularity coefficient and the particle-particle coefficient of restitution (COR) on oil shale particles hydrodynamics, and of the flue gas temperature and velocity on their drying characteristics were studied. It was shown that with a decrease in the specularity coefficient, the particle velocity increased, while the flue gas velocity, pressure drop and wall shear stress decreased. Decreasing the normal COR tended to increase the axial solid velocity-fluctuations and the number of the bubbles formed The predicted pressure drop and moisture content agreed reasonably with the experimental results at COR = 0.9 and the specularity coefficient = 0.2. The temperature and velocity of flue gas were shown to have a great influence on the drying characteristics of oil shale.