PREDICTION OF THE MINIMUM FLUIDIZATION VELOCITY

Relations to determine the minimum fluidization velocity (u(mf)) are t ested 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 equa tion, 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. Approx imations of the Ergun equation give results which are only valid over a limited range of Reynolds numbers and are not able to match the orig inal equation. Pure empirical equations are applicable in specific cas es, but cannot be generalized. The Ergun equation is reformulated as f ollows: 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 clearl y superior compared to any other equation.