Direct imaging of time-averaged flow patterns in a fluidized reactor using X-ray computed tomography

X-ray computed tomography (CT), a technique which has revolutionized medical imaging diagnostics, has been applied to the study of fluidization. In particular, a model fluidized bed reactor containing powdered coal was placed inside a medical CT device and scanned under a range of experimental conditions. The CT technique enables nondestructive, noninvasive visualization based on differences in the X-ray attenuation. For coal, X-ray attenuation is dominated by Compton scattering so that visualization is essentially that of the localized bed density to an excellent approximation. Spatial resolution is 0.087 mm/sup 3/, while density resolution is better than 30 kg/m/sup 3/. Density differences within the confines of the fluidized bed were observed and quantified. Gradients in static, fluidized, and spouted beds were observed.