The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study

Abstract

Discrete particle simulations are by now well established as an effective tool to study the mechanics of complex gas-solid flows in gas-fluidized beds. In this study, a state-of-the-art discrete particle model is used to explore the role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles. We find that the particle-particle interactions, including inelastic particleparticle collision; inter-particle friction and slightly cohesive forces, only have a negligible effect on the hydrodynamics of bubbling gas-fluidized beds of Geldart A particles. This is due to the fact that only a very small fraction of the energy input is dissipated during the non-ideal particle-particle interaction. We finally show that the selected drag correlation model significantly affects the bed hydrodynamics.

Universal relation between the density and the viscosity of dispersions of nanoparticles and stabilized emulsions

“…where 𝑚 is the mass of one nanoparticle [38,52]. The same type of equation is proposed in [53] However, the nanoparticles in motion also exerce a force −𝑛 (𝑭 + 𝑭 ) on the fluid, which undergoes a total driving force 𝑭 𝒅 due to the pressure gradient as well [38,53]. The force balance on the fluid is then given by…”

The effect of cohesive forces on the fluidization of aeratable powders

“…35 In contrast, the particle equations of motion do not require a computational grid, and a constant time step is used. As has been used for similar systems, the DPM time step is equal to 1 3 10 26 s. 11,15,36 The particle velocity is updated through a first-order integration scheme, which is in turn used to update the particle's position. In this DPM-CFD coupled approach, the simulation effectively advances in two steps.…”

“…X N c p51 2F vdw;pl n pl (15) where n pl is the unit vector along the line of contact pointing from particle p to particle l, and N c represents the number of cohesive particle-particle and particle-wall interactions. As discussed above, the model chosen here to represent surface roughness can only be considered an approximation.…”

“…Recent numerical studies from Kuipers' research group concluded that the effects of cohesive van der Waals forces were not significant in a small pseudo three‐dimensional (3‐D) fluidized bed with FCC particles of 75‐µm diameter. In one study, the gas inlet velocity was about 10 times the minimum fluidization velocity ( U mf ), and the values for material property of cohesion (Hamaker constant) were relatively low compared to those reported in the literature . In this study, full 3‐D simulations of a fluidized bed are conducted along the complete fluidization/defluidization cycle using reasonable material cohesion properties and realistic particles with asperities on their surface.…”

EMMS-based Eulerian simulation on the hydrodynamics of a bubbling fluidized bed with FCC particles

“…One possible reason is that, for Geldart A particles, the effect of sub-grid scale structure on constitutive laws is more pronounced [13][14][15]. At the same time, recent studies based on both two-fluid model and discrete particle model have shown that particle-particle interactions, including inelastic collision, the inter-particle friction and slightly cohesive force, play a minor role in the hydrodynamics of bubbling fluidized beds of FCC particles [5,16,17]. Therefore, a sub-grid scale model for inter-phase drag force appears to be the key point.…”