Flow structure characterization in conical spouted beds using pressure fluctuation signals

• Three different solid flow structures were detected in spouted beds.
• Movement of bulk of solids in annulus has a frequency less than 5 Hz.
• Motion of particles in the spout, clustering and transfer from annulus to spout are in the frequency range of 5 to 15 Hz.
• Small scale motion of particles, including cluster formation and movement, lies in the frequency range of 15 to 130 Hz.
• Any phenomena with a frequency greater than 130 Hz can be attributed to either turbulence or noise.

Characteristics of the hydrodynamics of conical spouted beds were revealed by analyzing pressure fluctuation signals in the frequency domain. Experiments were carried out in spouted beds with three different cone angles (30°, 45°, 60°) and high density spherical particles (ρp = 6050 kg/m3) with diameters of 0.5 or 1 mm. Different hydrodynamic structures in the movement of solids were identified by examining pressure fluctuations of the bed in the frequency domain. Peaks in the power spectral density of pressure fluctuations were observed corresponding to movement of bulk of solids (low frequency, less than 5 Hz), particle transport in the spout (medium frequency, between 5 and 15 Hz) and clustering and motion of clusters throughout the bed (high frequency, between 15 and 130 Hz). Axial movement of solids and pulsation motion of spout peripheries each exhibits a distinct peak in the medium frequency zone. It was shown by the frequency domain analysis of pressure fluctuations that solids are more mobile in annulus of a bed of smaller diameter particles and there is more effective lateral solid transfer from the annulus to the spout when the cone angle is smaller.

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