Effect of pressure on gas-solid flow behavior in dense gas-fluidized beds: a discrete particle simulation study

A computational study has been carried out to assess the influence of pressure on the flow structures and regime transitions in dense gas-fluidized beds using the discrete particle simulation (DPS) approach. By employing particle level simulation, the particle-particle-fluid interactions were analyzed to highlight the intrinsic mechanisms underlying the gas-solid flow patterns and to elucidate elevated pressure-induced improvement of fluidization quality. Our results show that the bed pressure drop could be predicted satisfactorily with the discrete particle model. Furthermore, an elevated pressure reduces the incipient fluidization velocity, widens the uniform fluidization regime, shortens the bubbling regime and leads to a quick transition to the turbulent regime. Spanning from the incipient fluidization to the turbulent regime, an elevated pressure efficiently depresses the bubble growth and therefore produces more uniform gas-solid flow structures. In particular, it is found that an elevated pressure changes the roles of particle-particle collision and particle-fluid interaction in their competition. An elevated pressure through enhancing gas-solid interaction and reducing the particle collision frequency, effectively suppresses the formation of large bubbles. As a consequence, a more uniform gas-solid flow structure with a higher bed height is produced, leading to the particulate fluidization. (C) 2002 Elsevier Science B.V. All rights reserved.