Measurement of longitudinal distribution of solids holdup in a three‐phase fluidized bed by ultrasonic technique

Abstract

A method of measurement of solids holdup in a three-phase reactor by analyzing the shape and the phase lag or lead of an ultrasonic wave has been proposed. The solids holdup in a solids-dilute three-phase fluidized bed could be measured without being affected by the presence of gas bubbles. The experimental values of solids axial dispersivity measured by the ultrasonic technique are in reasonable agreement with an empirical correlation of previous data obtained by other methods. The possibility of the application of the ultrasonic technique to the measurement of solids holdup in a three-phase fluidized bed has been suggested.Nous proposons une mkthode de mesure de la retention des solides dans un reacteur triphasique en analysant la forme et le retard ou I'avance de phase d'une onde ultrasonore. La retention des solides dans un lit fluidis6 de solides triphasique dilut pourrait &re mesuree sans Ctre modifike par la presence des bulles de gaz. Les valeurs expkrimentales de la dispersivitk axiale des solides par la technique ultrasonore montrent un bon accord avec la corrklation empirique des donnkes antkrieures obtenues avec d'autres methodes. On suggkre d'appliquer la technique ultrasonore pour mesurer la retention des solides dans les lits fluidisks triphasiques.

Ultrasonic Technique For Measuring Phase Holdups In Multiphase Systems

“…There are several measurement techniques for measuring phase holdup in multiphase systems such as staticpressure, direct sampling, shutter, optical-probe, and electrical-probe techniques. The static pressure method is ineffective when the solid density is close to the liquid density, the direct optical-probe method and the electrical-probe technique are difficult to use for obtaining reliable results, and the direct sampling method is not accurate in measuring solid particles in the slurry (Uchida et al, 1989a). …”

Non-invasive imaging of liquid/gas flow using ultrasonic transmission-mode tomography

“…Examples of ultrasonic techniques for differentiating three-phase components in gas-liquid-solid system are the use of ultrasonic signal analysis method [9][10][11] and multi-frequency ultrasonic technique [12].…”

Measurement of gas hold‐up in three‐phase systems by ultrasonic technique

“…Okamura et al [3] established a principle for determining gas, liquid and solid hold-ups independently and simultaneously by analyzing the phase lead or phase lag of ultrasonic waves. Uchida et al [4] accurately measured the longitudinal distribution of solids hold-up in a threephase fluidized bed by applying this principle and suggested the application of ultrasonic technique to the evaluation of solids hold-up in such processes. However, they have not as yet reported on measurements of gas hold-ups by using this method.…”

“…Here, t,, tb and t, are the transmission times of an ultrasonic wave in the liquid, liquid-solid and three-phase systems, respectively'). It has been reported that the solids hold-up was determined from (t, -tb) [4]. Correspondingly, the gas hold-up in the three-phase system can be estimated from ( t b -tc).…”