(215f) Large-Scale DEM-CFD Simulation for a Pseudo 2-D Bubbling Fluidized Bed Containing Binary Mixture of Particles with Large Size Difference

In practical applications of
fluidized beds, the size of solid paticles is not uniform and large particles coexist
with small particles. The large size difference significantly influences the
mixing and segregation phenomena in a bed. Despite of its engineering and
physical importance, these behaviors are not fully understood. In the present
study, large-scale DEM-CFD coupling simulation (Powder Tecnol., 77(1),
pp. 79-87, 1993) is performed for a pseudo-2D bubbling fluidized bed containing
binary mixture of particles with large size difference. The momentum exchange
between the larger particles and fluid is expressed by the fictitious particle
method proposed by Tsuji et al. (AIChE J., 60(5), pp. 1606-1620, 2014). The small particles are
smaller than the computational cell size used in fluid calculation, whereas the
large particles are larger than the cell size.

A snapshot of the simulation results
is shown in Fig. 1 where twenty-five million small particles with a diameter of
1 mm and density of 2500 kg/m³ are mixed with five hundred large
particles which are 20 mm in diameter and 1600 kg/m³ in density. In
addition to the high concentration of the large particles near the side walls
(Fig. 1a), falling motion of the large particles inside the bubbles can be observed.
The large particles in the bubbles draw the surrounding small particles and induce
characteristic structure formations inside the bubbles (Fig. 1b).