Fast X-ray tomography for the quantification of the bubbling-, turbulent- and fast fluidization-flow regimes and void structures

摘要

Multiple fluidization regimes were studied using X-ray tomography. Geldart B sand particles were usedin a 14 cm (ID) column with a dual cyclone return system. Cross sectional solids concentration (/) wasmeasured and the time averaged / ð /Þ decreased with velocity and axial height except in the turbulentregime where / remained constant. Radial profiles of / decreased to the centre, while all turbulentregime velocities resulted in similar radial / profiles. Results confirm the bubbling-turbulent transitionvelocity (Uc) determined from pressure fluctuations is a reliable quantification technique. The systemexhibited slugging behaviour at higher bubbling regime velocities with voids taking on cylindricalshapes. Turbulent regime voids were characterised by elongated cylinders with diameters slightly lessthan the bubbling regime’s slugs or fast fluidization regime’s core annulus. Distribution curves of the /signal indicated a distinct dense phase in the bubbling and turbulent regime with a velocity independentsolid concentration. Void velocity analysis suggested that the bubble linking algorithm was unable todetect fast rising voids at higher velocities.