Numerical studies of the effects of fines on fluidization

Abstract

Euler-Lagrange simulations of fluidized beds of Geldart Group A particles containing different levels of fines are performed in periodic domains with various domain-averaged solid volume fractions. Bubble-like voids readily form when no fines are added. Introducing fines does not reduce bubble sizes if van der Waals force between particles is not accounted for. In contrast, the addition of van der Waals force produces significant changes. With no fines, bubbles are found to be suppressed at sufficiently high solid volume fractions, corresponding to the expanded bed regime for Group A particles. With the addition of fines, bubbles can be suppressed at lower solid volume fractions. With more fines added, bubbles can be suppressed at even lower solid volume fractions. When bubbles are suppressed, the system is found to be in a stable solid-like regime. In this regime, forces on each particle are balanced, and the particle velocity fluctuations are dampened.

Towards filtered drag force model for non-cohesive and cohesive particle-gas flows

“…It is well-known that cohesive force may lead to agglomeration of particles and affect fluidization behavior of particles. 27,28,30,31,[59][60][61] In particular, the micro-structure of particles is significantly affected by cohesive force, and as a consequence, the drag force is expected to be different from the non-cohesive case. We performed two additional simulations with low and high cohesion levels to probe the importance of particle cohesion on the extent of correction to the drag force.…”

“…In contrast, numerous Euler-Lagrange models, where the locally averaged equations of motion for the fluid phase are solved in an Eulerian framework and the particles are tracked in a Lagrangian fashion by solving Newton's equations of motion, have been successfully used to simulate gas-solid flows with such complex interactions. [27][28][29][30][31][32][33][34][35] Instead of incorporating complex particle physics into Euler-Euler models via theoretical derivations, it is more straightforward to perform Euler-Lagrange simulations including complex particle physics and use these simulation results to directly propose constitutive relations for filtered Euler-Euler models. As shown in our previous study, 36 one can use the drag corrections deduced from Euler-Lagrange simulations for filtered Euler-Euler simulations.…”

Linking discrete particle simulation to continuum properties of the gas fluidization of cohesive particles

“…In particular, particle cohesion can be straightforwardly considered through directly computing the interparticle forces such as the van der Waals force, [15][16][17][18] liquid bridge force, [19][20][21][22][23] and electrostatic force. [24][25][26][27][28] Hence, CFD-DEM approach was widely used in previous studies [29][30][31][32][33][34][35][36] for the microscopic understanding of the fluidization of cohesive particles. However, the detailed particle scale simulation of CFD-DEM will result in a prohibitively high computational cost for the modeling of an industrial system by current conventional computational infrastructures.…”

Analysis of the effect of small amounts of liquid on gas–solid fluidization using CFD‐DEM simulations

“…The hydrodynamics of granular flows and fluidized beds can be influenced significantly by interparticle forces, arising from van der Waals interactions, electrostatics, small amounts of liquid, or sticky surface coatings . Adding small amounts of liquid to granular flows and fluidized beds is necessary in a variety of processes, particularly in the energy and pharmaceuticals industries .…”