Experimental and numerical study of the characteristics of the forced oscillation in a pulsation fluidized bed (PFB) for coal separation

•1. The main features of pressure fluctuations were investigated based on the theory of forced oscillation.•2. The fundamental reason for small bubbles in pulsation fluidized bed was demonstrated by experiment and simulation.•3. The optimal pulsation frequency for separating fine coal particles was defined as bed natural frequency. Pulsation fluidized bed (PFB) has indisputable advantages for the dry coal beneficiation process. Due to the interaction mechanism between pulsation gas flow and particles is not clear, the regulation of the parameters is still based on empirical method. In this study, the oscillation characteristics of PFB in relation to pressure fluctuations and bubbles motion were studied by both lab experiments and CFD-DEM simulation. Power Spectral Density (PSD) results indicated that dominant frequency of pressure fluctuations was the same as the pulsation frequency of gas flow. In addition, double peaks were clearly formed when the pulsation frequency was set close to the bed natural frequency (about 3.49 Hz). Furthermore, Bubble growth was limited at a moderate frequency (3.49 Hz), but continued to increase at a higher frequency (5.24 Hz). Lab separation experiment also proved that, the pulsation frequency in the middle ranges (especially close to the natural frequency) can significantly improve separation performance.