Hydrodynamic scaling and cyclone performance of pressurized circulating fluidized beds

We verify the validity of the "reduced set" of four dimensionless parameters proposed by Glicksman et al. (1993) to characterize flows in Pressurized Circulating Fluidized Beds. Although the "reduced set" is valid for viscous and inertial particle drag, we test its appropriateness in the intermediate regime by comparing two series of experiments with different combinations of gases and solids that preserve the "reduced set" but mismatch the complete set of five dimensionless numbers characterizing the flow. We also evaluate the performance of the primary cyclone for both series.; While Archimedes numbers are widely different in the two series, the distribution of particle terminal velocities calculated with the correlations of Haider and Levenspiel (1989) is preserved. Comparisons of the dimensionless profiles of pressure along the flow and solid volume fraction in the radial direction indicate that both data series exhibit similar hydrodynamics in the fully-developed region.; In addition, we find that pressure and radial profiles depend strongly on the solid loading but weakly on the Froude number, and that the gas pressure gradient in the fully-developed region is nearly balanced by the suspension weight, except at the lowest superficial gas velocity. Radial profiles of solid volume fraction relative to the mean across the flow appear independent of conditions. However, the mean solid volume fraction increases with solid loading. These observations are captured by a simple model of the relative velocity between gas and solids that recognizes the crucial role played by solid clusters in this flow.; Finally, we find that pressure losses across the cyclone scale with the gas inlet kinetic energy. Our pressure data are well captured by the model of Muschelknautz and Greif (1997), who predict that pressure losses decrease with increasing solid loading. However, the loading-independent model of Leith and Licht (1972) is better at capturing the overall and grade efficiencies of our primary cyclone.