Particle dispersion and pressure fluctuations in three-phase fluidized beds

Effect of Gas Density on the Hydrodynamics of Bubble Columns and Three‐Phase Fluidized Beds

“…Bubble dynamics were characterized through pressure fluctuation analysis. Two absolute pressure transducers (both Omega, PX808-005GV) were employed to monitor differential pressure fluctuations, with sampling at 100 Hz for 90 s periods, sufficient to detect the full spectrum of hydrodynamic signals in both bubble columns and three-phase fluidized beds (Kang et al, 1997;Vial et al, 2001). The absolute pressure transducers were positioned flush with the wall at distances of 165 mm and 600 mm above the distributor plate.…”

Radial Liquid Dispersion and Bubble Distribution in Three‐Phase Circulating Fluidized Beds

“…It is interesting to note that the effects of gas and liquid velocities and solid circulation rate on the bubble size tend to increase as the radial position approaches the centre of the riser. The increase of bubble size with U G can be due to the increase of bubble holdup with increasing U G. The reason why the bubble size decreases with increasing U L or G S can be the increase of turbulence which is effective to break down the rising bubbles in the riser (Liang et al, 1995;Kang et al, 1997;Cho et al, 2001a).…”

Characteristics of pressure fluctuations and fine coal preparation in gas-vibro fluidized bed

“…The time series of the pressure signals can be analyzed using time-domain, frequencydomain, and state-space methods (Johnsson, Zijerveld, Schouten, van den Bleek, & Leckner, 2000;van Ommen et al, 2011). The minimum fluidization velocity (Punčochář, Drahoš,Čermák, & Selucký, 1985;Sobrino, Almendros-Ibañez, Santana, & de Vega, 2008;Mohanta, Daram, Chakraborty, & Meikap, 2012), pressure wave propagation (Bi, 2007), particle dispersion (Kang, Woo, Ko, & Kim, 1997), complex dynamics of a fluidized bed (Tahmasebpour, Zarghami, Sotudeh-Gharebagh, & Mostoufi, 2013), and bubble flow (Sasic, Leckner, & Johnsson, 2006;Croxford & Gilbertson, 2011) Nomenclature C xy (ω) coherence function COP xy (ω) coherent-output power spectral density for two time series recorded at position x and y f gas pulsation frequency IOP xy (ω) incoherent-output power spectral density for two time series recorded at position x and y M number of segments N total number of pressure data points N FFT data point number of the FFT p pressure time series p x (t), p y (t) pressure time series measured at position x or y S xx (ω), S yy (ω) power spectral density of the pressure time series measured at position x or y S xy (ω) cross power spectral density for two time series recorded at position x and y t time 2004;van Ommen et al, 2011) used the advanced analysis methods as an online tool to detect defluidization in an industrial fluidized bed. In this study, pressure fluctuations in a gas-vibro fluidized bed for coal preparation were investigated to determine the relationship among pressure fluctuations, bubble behavior, and separation efficiency.…”