Porosity distributions in a fluidized bed

Abstract

Some theoretical equations, regarding the porosity distribution in a fluidized bed of very large diameter, have been developed. Measurements on this porosity distribution in the centre of a fluidized bed of glass beads and air agreed sufficiently well with the theory. In general three distinct zones in the centre of the fluidized bed could be distinguished. Near the sieve, a sieve effect zone was found, followed by a zone of constant porosity reaching up to the initial bed height at incipient fluidization and above it a zone of increasing porosity for which a probility function has been found. The constants in this function have been correlated with some fluidization variables, such as fluidization velocity, bed weight and particle size. The bed expansion in all cases showed a linearity with the product of bed weight and fluidization velocity. Experiments with silica gel and polystyrene pearls instead of glass beads had the same results. From measurements throughout the whole bed and by connecting points of equal porosity, so called isopores have been obtained, from which streaming patterns in the fluidized bed could be deduced. The influence of the bed weight on such isopores has been presented.