Experimental investigation of coarse coal slime fluidization characteristics in three-phase fluidized beds

The gas-liquid-solid fluidized beds are highly effective for the separation of coarse coal slime, but their hydrodynamic behavior requires further clarification. This study investigates flow regimes based on real-time pressure fluctuation signals measured using micro-pressure sensors. A comprehensive analysis of pressure signal dispersion was conducted through pressure fluctuation curves and probability density functions. The critical liquid velocity for fluidization was identified at approximately 6*10⁻³ m/s, based on inflection points in pressure drop-velocity curves. Fixed beds exhibit elevated standard deviation, skewness, and kurtosis, signifying instability and non-uniformity, whereas fluidized beds display markedly lower time-domain values. Further refinement of flow regime classification can be achieved through frequency domain analysis, which provides enhanced characterization of particle and bubble dynamics within the fluidized bed system. Fluidized beds exhibit low overall pressure fluctuation energy, with power concentrated in low-frequency regions (<10 Hz) at low gas velocities. When the gas velocity exceeds 1.5*10⁻³ m/s, energy shifts toward higher frequencies (10–20 Hz), reflecting intensified bubble turbulence. This analysis facilitates the further delineation of fluidized bed into the bubble dispersion regime and particle turbulence regime. The investigation of fluidization characteristics clarifies the environmental features in fluidized flotation, thereby laying a solid foundation for further experimental exploration and mechanistic studies of mineral separation in three-phase systems.