Discrimination of fluid bed models and investigation of particle-to-gas mass transfer by means of drying experiments

Abstract

Particle-to-gas mass transfer in fluidized beds has been investigated by drying experiments. To avoid the introduction of additional unknowns into the problem, the particle-side kinetics are described by the method of normalization. The normalized single particle drying curve has been derived by separate, direct measurement. The Sherwood number can be obtained by comparison with a heterogeneous fluid bed model. This procedure is demonstrated by measurements with aluminium silicate particles. The resulting Sherwood number is significantly lower than the respective single particle value. Model discrimination reveals that this effect can hardly be explained by bypassing or axial dispersion. Discrimination of this kind would not have been possible on the basis of traditional measurements with sublimation of compact material or drying of surface-wet particles.