BED EXPANSION OF LIQUID-SOLID INVERSE FLUIDIZATION

The bed expansion characteristics of two-phase inverse fluidization were studied. Twelve different spheres with diameters from 1.31 to 7.24 mm and densities between 75 and 930 kg/m3 were fluidized with water. The experimental lnepsilon-lnU curves were parallel to those predicted by the model of Richardson and Zaki and therefore the exponents n were similar. However, U(i), the liquid velocity at epsilon = 1 differed from that predicted from the standard drag curve for Re(t) > 130. This can be explained by the fact that the drag curve of a freely rising light sphere differs from that of a falling particle. The values of U(i) calculated using this modified drag curve were in good agreement with the experimental results. The difference between experimental and calculated from the Ergun equation minimal fluidization velocities is explained by the difference in mechanical inertia of the light and heavy particles.