PREDICTION OF THE MINIMUM FLUIDIZATION VELOCITY

Relations to determine the minimum fluidization velocity (u(mf)) are tested statistically with 80 measurements reported in the literature on 20 different substances. All relevant relations (33 equations) can be reformulated as dimensionless correlations in which the state of the fluidized bed is determined by the parameter Ar/Re(mf). The Ergun equation, the well-established relation for the pressure drop over packed beds of spherical particles, can be used to describe the behaviour of a fluidized bed at the minimum fluidization velocity correctly. Approximations of the Ergun equation give results which are only valid over a limited range of Reynolds numbers and are not able to match the original equation. Pure empirical equations are applicable in specific cases, but cannot be generalized. The Ergun equation is reformulated as follows: GRAPHICS This equation, in which the characteristic parameter of the bed (Ar/Re) GRAPHICS is a function of type of particles forming the porous bed plus the flow of the fluid through this bed, is clearly superior compared to any other equation.