Discrete particle modeling of lateral jets into a packed bed and micromechanical analysis of the stability of raceways

Abstract

Gas jets are often used to promote heat and mass transfer by forming raceways or circulating regions in a packed bed. Such an operation is common and critical in many processes. Multiple raceways can interact and be affected by the formation of different flow zones. This work develops a multiscale model to examine the formation and the stability of raceways and the underlying micromechanics. Four states are observed in the fluidized flow regime. More fundamentally, a critical bed width for the observation of different flow zones and states is found through numerical simulations and a theoretical analysis. Finally, the complicated transitions between different flow states are examined at a bed scale, and two general trends of the averaged solid velocity are found. The findings from the multiscale model are useful both scientifically for the understanding of state transitions and practically for the design and the operation of relevant chemical reactors. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4240–4250, 2016

Numerical Analysis of Raceway Formation in Isothermal and Non-reactive Packed Bed

“…A mathematical model to analyze the particle motion and the fluid flow in raceway used in this study has fundamentally same structure as the previous analyses. 45,46,[50][51][52][53][54][55] In other word, the particle tracking method and the computational fluid dynamics are combined. Details of the model are explained in the following sections.…”

“…45) As used in some combustion analyses, 45,46) the combination of the particle tracking method for the particle motion and techniques of computational fluid dynamics have been applied to the analysis of the raceway behaviors. [50][51][52][53][54][55] Additionally, the particle tracking techniques including irregular particle shape were also applied to the raceway analyses. 56,57) These approaches successfully reproduced the formation of the cavity in the packed bed, the particle circulation motion and the gas flow pattern and clarified the effect of particle shape on the motion and heat transfer characteristics in and around the raceway.…”

Review on Modeling and Simulation of Blast Furnace

“…Hilton et al demonstrated that particle shape is crucial to the structure and the dynamics of circulation regions in their CFD‐DEM simulation of lateral injection of high‐speed gas into a packed bed of different shaped particles. Recently, Hou et al used a CFD‐DEM model to study the raceway behaviors as a result of two lateral jets into a packed bed and found that with increasing superficial gas velocity, a raceway can form only when the bed width is large enough. Generally, the above studies considered the lower part of BF or a box‐shaped packed bed at a small scale.…”

Simulation on the combustion in the raceway zone of COREX melter gasifier

“…Shen et al [14,15] established a series CFD models to study the coal combustion in raceway zone. Recently, the coupled CFD-DEM model was also developed to the particles and gas-flow in the raceway in blast furnace [16][17][18][19][20].…”