Particle-Scale Local Flow Disturbances Induced by Feed-Particle Size and Shape in a Gas–Solid Fluidized Bed

During coal beneficiation in a gas–solid fluidized bed, coarse feed particles act as moving intruders whose size and shape can reorganize the local gas–solid flow field. This study combines particle-surface differential-pressure measurements, synchronized visual observation, pressure-signal analysis, and Eulerian–Eulerian CFD to distinguish the disturbance caused by the feed particle from the background fluctuation of the dense medium. Unlike studies that characterize only the global bed pressure drop, the present work resolves the pressure response on the upper and lower surfaces of individual 13–50 mm feed particles and links it to bubble attachment, bypassing, and medium-particle recirculation. Within a fluidization-number range of 1.0–1.6, the disturbance intensified with feed-particle size: the 50 mm particle produced the largest upper–lower pressure difference and pressure-drop fluctuations exceeding 100 Pa. Particle shape also altered the local flow topology; the flat lower face of the block-shaped particle promoted a persistent gas cushion, localized pressure concentration, and medium recirculation; whereas, the spherical particle generated a comparatively symmetric disturbance. Synchronized images confirmed the transition from intermittent small bubbles near minimum fluidization to bubble coalescence and vigorous recirculation at higher gas velocities. At N = 1.2, the CFD results reproduced the experimental size and shape rankings, with case-by-case relative errors of 4.7–7.0% and a mean absolute relative error of 5.5%. Coherence analysis further showed that the influence of a large particle decayed with distance and produced a stepwise axial distribution of local flow states. These results provide a particle-scale basis for controlling feed-induced disturbances in gas–solid fluidized-bed separation.