Hydrodynamic Characterization of Three-Phase Fluidized-Beds Using Vibration Signature Analysis

Vibration fluctuations of a three-phase gas-liquid-solid fluidized-bed, as a novel method of hydrodynamic characterization of such a complex system, were introduced and investigated. The studied three-phase fluidized-bed consisted of air, water, and sand particles as three operating phases, in which, water was continuous, and air and sand particles were dispersed phases, respectively. Such fluidized-beds, in which, the gas and liquid are upward co-current flows, and solid is present from the beginning of the process, are known as the most common industrial three-phase fluidized-beds. Using reliable, yet non-intrusive methods to study the hydrodynamics of such systems is vital. In this paper, time-series obtained from vibration fluctuations signals at a height of 13.5 cm (L/D = 1.5) above the gas-liquid distributor were analyzed at time domain (statistical methods), as a usual method. Also, average cycle frequency, as a novel method to characterize such systems, was introduced. It was concluded that standard deviation of bed-shell vibration fluctuations is a powerful representative of bed overall regime change, and the change of the slope of kurtosis is occurring near minimum fluidization. Moreover, minimum liquid-fluidization velocity was acquired using average cycle frequency of vibration signals with an acceptable relative error. Operating condition, resulted by vibration analysis, at which the bed-regime change occurred, was in agreement with experimental observations, and the results of minimum fluidization were consistent with the most accurate relations in the literature. Finally, vibration signature analysis, as a fully-non-invasive method which doesn’t interfere with internal hydrodynamics of the bed, is introduced to hydrodynamic characterization of three-phase fluidized beds. Outline of present research can be used in industrial reactors operated at sever conditions of temperature and/or pressure successfully.