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