Coarse-Grain DEM Modelling in Fluidized Bed Simulation: A Review

Abstract

In the last decade, a few of the early attempts to bring CFD-DEM of fluidized beds beyond the limits of small, lab-scale units to larger scale systems have become popular. The simulation capabilities of the Discrete Element Method in multiphase flow and fluidized beds have largely benefitted by the improvements offered by coarse graining approaches. In fact, the number of real particles that can be simulated increases to the point that pilot-scale and some industrially relevant systems become approachable. Methodologically, coarse graining procedures have been introduced by various groups, resting on different physical backgrounds. The present review collects the most relevant contributions, critically proposing them within a unique, consistent framework for the derivations and nomenclature. Scaling for the contact forces, with the linear and Hertz-based approaches, for the hydrodynamic and cohesive forces is illustrated and discussed. The orders of magnitude computational savings are quantified as a function of the coarse graining degree. An overview of the recent applications in bubbling, spouted beds and circulating fluidized bed reactors is presented. Finally, new scaling, recent extensions and promising future directions are discussed in perspective. In addition to providing a compact compendium of the essential aspects, the review aims at stimulating further efforts in this promising field.

Experiment and computational fluid dynamics investigation of biochar elutriation in fluidized bed

“…Each CGP represents the movement of W (statistic weight) physical particles and these particles share the same properties, such as mass, velocity, and positions. The derivation and validation of CG‐DEM is available in the literature 12–15 . The selection of statistic weight influences the computation cost and the accuracy of the simulation.…”

“…Recently, the coarse‐grained discrete element method (CG‐DEM) reduced the computation cost of discrete simulations by lumping physical particles into numerical parcels. It was used in the simulation of coal gasification, 6,7 biomass gasification, 8 biomass pyrolysis, 9 methanol‐to‐olefin, 10 circulating fluidized bed (CFB) carbonator, 11 and many other reactors 12 . However, its capability to accurately predict the elutriation rate was not evaluated.…”

A Comparison of Ansys Fluent and MFiX in Performing CFD-DEM Simulations of a Spouted Bed

“…In this work, we employed the standard values of 2/7 and 1/2 for the ratios between the normal and tangential values of the spring constant and restitution coefficient. Both Fluent and MFiX allow for reducing the number of particles by lumping several of them in a larger "parcel"; this approach is usually known as "coarse-graining" [42,43]. As the number of involved particles is already quite low, this procedure was not employed here.…”

Development of Simpler Coarse-Grain Model for Analyzing Behavior of Particles in Fluid Flow

“…Although these three models indicated that the particle behavior in fluidized beds could be represented, and that the calculation load could be reduced, the particle behavior cannot be represented with sufficient accuracy. Subsequently, for fluidized beds, numerous coarse-grain models have been developed to improve the accuracy and versatility of the models [17][18][19][20][21][22][23][24]. Sakai et al proposed the more accurate coarse-grain model for the particle behavior in fluidized beds.…”