Solid hold-up measurement in a jet-impactor assisted fluidized bed using gamma-ray densitometry

A jet-impactor assisted-fluidized bed (JIAFB) for continuous de-agglomeration of nanopowder agglomerates was presented in previous work. Therein, a jet caused agglomerates to impinge up an impactor, where they would break. However, efficient impactor positioning will be dictated by particle momentum: the product of solid concentration and velocity must be highest. Herein, the variation of solid hold-up was measured in a fluidized bed of Fe₂O₃ nanoparticles using gamma-ray densitometry. Behaviour was compared under minimum fluidization and bubbling regimes, over a wide range of jet velocities (0–200 m s^?1). A new line-decomposition approach allowed mapping local solid distribution across seven axial and five radial positions, tangibly demonstrating how increasing the gas velocity enhanced the fluidization quality by increasing axial solid diffusivity. Conversely, increasing jet velocity locally decreased solid hold-up in the jet-affected zone, and brought about inhomogeneities. With this information in hand, jet-to-impactor distance was optimized and validated experimentally.