Despite the inherent advantages of fine powders due to their high surface area, their fluidization remains challenging due to strong interparticle forces, which promote structural non-homogeneities, leading to gas bypassing and unpredictable hydrodynamics. This study investigates the hydrodynamics of a pulsed fluidized bed using square-wave flow modulation to improve the fluidization of cohesive activated carbon powder, widely used in environmental applications. Four pulsation frequencies (0.025, 0.050, 0.10, and 0.25 Hz) were evaluated at amplitudes \(\left({N}_{Re}/{N}_{Remf}\right)\) ranging from 2 to 10. The onset of non-homogeneities was consistently characterized by a negative gradient in the normalized pressure-drop-time profile. Low-frequency pulsation at 0.025 Hz failed to prevent structural failure even at a low amplitude of 2, as prolonged flow interruption allowed heterogeneities to consolidate. At 0.050 Hz, bed stability improved, with the onset of non-homogeneities emerging at a pulsation amplitude of 4. At 0.10 Hz, stable operation was maintained at intermediate amplitudes, with structural destabilization initiating near the distributor and propagating upward as amplitude increased. In contrast, increasing the frequency to 0.25 Hz markedly enhanced hydrodynamic stability by delaying the onset of non-homogeneities to substantially higher amplitudes. Frequency-domain analysis revealed that structurally stable cohesive beds strongly attenuate the imposed pulsation. The emergence of a distinct spectral peak at the fundamental frequency serves as a non-intrusive diagnostic marker of structural breakdown. These findings demonstrate that higher-frequency pulsation effectively mitigates the formation of non-homogeneities, and enhance the operation stability of fluidized bed of cohesive powders.
