Analysis of flow dynamics and velocity in circulating fluidized beds: non-invasive measurements with gamma radiation

Abstract

This study introduces a non-invasive method for characterizing gas-solid flow in circulating fluidized bed (CFB) risers using gamma radiation transmission. By applying the Richardson-Zaki law and measuring radial gamma attenuation, the analysis quantifies FCC catalyst velocity profiles and solid holdup across varying flow conditions. Experiments explored the effects of superficial gas velocity (500–700 L/min), VPC valve openings (25–35%), and axial height on particle dynamics. Increasing the air flow rate raised catalyst velocity by up to 25%, while higher solid concentrations reduced velocity near the riser walls by approximately 22%. Velocity profiles exhibited parabolic shapes at lower positions and became uniform in the upper sections, confirming the establishment of fully developed core-annular flow. The method delivered results with high repeatability, showing less than 3% uncertainty across five repetitions. These findings provide a novel and precise tool for diagnosing flow regimes and optimizing riser performance in FCC and other multiphase process systems.