Capacitance probes for solids volume concentration and velocity measurements in industrial fluidized bed reactors

The capacitive measurement of solids volume concentrations is based on the determination of the relative dielectric constant of a fluid-solids suspens ion in the capacitance sensor volume. The suitability of various theoretica l and empirical calibration relationships that relate the volumetric fracti on of the solids to the mixture dielectric constant has been investigated a nd a new empirical calibration relationship is suggested. The application o f the calibration relationship to capacitive measurements in high-temperatu re fluidized bed reactors is demonstrated. Measurements of solids volume co ncentrations and velocities in the upper dilute zone of a cold model circul ating fluidized bed (CFB) and in the bottom zone of a large-scale industria l CFB boiler illustrate the value of capacitance probes for local flow stru cture investigations. (C) 2000 Elsevier Science S.A. All rights reserved.