Application of Acoustic Techniques to Fluid-Particle Flows in Fluidised bed*

The characterisation of dispersed flows is of great importance to many industrial sectors, including energy, and pharmaceutical industries. Recently, acoustic techniques have attracted considerable attention for the characterizarion of dispersed particle flows.This is attributed  to their ability to obtain measurements in real-time and at high particle concentrations.

In this paper, we have applied acoustic techniques to the study of solid-liquid fluidized beds.The signal processing for obtaining velocity profiles, particle size distribution, and volume fraction are discussed.The experiment was conducted in a vertical tube with a 5cm inner-diameter, made of borosilicate glass, and it contains 0.55kg glass particles.The techniques are based on the measurement of ultrasound attenuation coefficient spectroscopy, sound speed, and frequency shift of the propagated sound wave.The ultrasound propagation speed in the fluidized bed was measured to be between 1504m/s to 1565m/s for the glass particle volume fractions  from 27.1% to  60.9%  in tap water.The solid velocity profiles were measured for fluid flow rates varying from 1L/min to 5L/min.The particle size distributions were measured for four different sizes of glass particles ranging from 500μm to 1250μm at a volume fraction of 35%.