The significance of gas release on the mixing of larger particles in bubbling fluidized beds
Year: 2026
Type: article
Abstract: The mixing of larger particles (e.g., fuel particles) in a bubbling fluidized bed is governed by buoyancy and drag, which correspondingly promote segregation and internal circulation. Prior studies have shown that gas released from such particles during drying or devolatilization can generate so-called endogenous bubbles, which exert an effective lift force on the particle. However, the impact of gas release under bubbling conditions and with over-bed particle feeding, remains unexplored.This study investigates how gas release influences the mixing of larger particles in a bubbling fluidized bed. Experiments were conducted in a fluid-dynamically downscaled model simulating biomass pyrolysis at 700°C in a bed of silica sand fluidized with flue gas. Magnetic particle tracking captured particle trajectories, and gas-releasing tracers were used.Different behaviors were observed depending on the fluidization velocity. At low fluidization velocities (uo/umf ≥ 2), buoyant particles sink slightly deeper by locally reducing the concentration of surrounding suspension, whereas heavy particles experience inhibited sinking resulting in preferred positions closer to the bed surface. As fluidization velocity increases beyond uo/umf ≤ 3.5, the effect of gas release on axial mixing diminishes, while the lateral mixing becomes more pronounced, with the dispersion coefficient enhanced by up to 40%.
Source: Fuel Processing Technology
Institution: Chalmers University of Technology
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,180
Funder: Energimyndigheten
Award: G580094917
OpenAlex ID: W7171837049