Hydrodynamic and Mixing Characteristics of Gas-Solid Flow in a Pulsed Spouted Bed

The flow behavior and particle motion in a pulsed gas-solid spouted bed was investigated using the Eulerian-Lagrangian approach. The computational fluid dynamics-discrete element method (CFD-DEM) was used to evaluate the gas flow field and particle trajectories. The model was four-way coupled to account for fluid-particle, particle-fluid, and particle-particle interactions. A column of 150 x 15 mm cross-section and height 750 mm containing 24500 particles of diameter 2.5 mm was investigated. Gas entered through a 10 X 15 mm slot at the base of the bed. Steady spouting was compared with pulsed spouting at frequencies of 1, 4, and 10 Hz, with superficial velocity amplitude of 0.5 and 1 m/s and a mean superficial spouting velocity of 2 m/s. In addition to comparing the bed pressure drop versus time and its Fourier decomposition, the hydrodynamics in the spout and annulus regions were examined. A new procedure was introduced to assess spouted bed mixing and homogeneity. Flow pulsation was shown to provide stronger upward air momentum, less horizontal gas percolation, better circulation, higher downward particle flux near the sidewalls, better mixing, and greater homogeneity.