Impact of pressure on gas-solid hydrodynamics of Geldart B and D particles in a pressurized bubbling fluidized bed: A CFD-DEM study

Abstract

Pressurized fluidized beds have gained considerable interest in industrial applications due to their superior performance and efficiency compared to atmospheric fluidized beds. However, the mechanisms through which pressure influences the hydrodynamic behavior of different particle types remain insufficiently explored, hindering the scale-up, optimization, and broader adoption of this technology. To address this gap, CFD-DEM simulations were performed on a pseudo-2D pressurized bubbling fluidized bed using Geldart B and D particles. The effects of pressure, particle size, and initial bed height on key flow characteristics, including minimum fluidization velocity, particle dynamics (i.e., particle velocity and volume fraction distribution), and bubble behavior (i.e., bubble diameter, aspect ratio, density) were comprehensively examined. Results showed that the minimum fluidization velocity decreases with increasing pressure and increases with particle size, with greater sensitivity at lower pressures. Higher pressures lead to smaller bubble diameters, higher bubble aspect ratios, and denser bubble populations, resulting in concentrated particle distribution in the lower bed and more uniform radial dispersion. In contrast, larger particles create fewer, larger bubbles or slugs, and increase the overall bed height. These high-fidelity simulations offer valuable insights for optimizing the performance of pressurized fluidized beds in industrial processes.