A comprehensive experimental study has been carried out to investigate the fluidization behavior with supercritical carbon dioxide at pressures up to 30 MPa for various solids which behave as Geldart A and B powders, respectively, under ambient conditions. From pressure drop measurements minimum fluidizing velocities and bed voidages were determined. Capacitance probe measurements yielded suspension voidages, bubble sizes and velocities. It was found that Ergun's equation is also applicable to the flow of a supercritical fluid through a fixed bed and that the Wen and Yu relationship can be used for the determination of the minimum fluidizing velocity. Correlations for homogeneous bed expansion, minimum bubbling velocity and the visible bubble flow were derived. (c) 2005 Elsevier B.V. All fights reserved.