Experimental Support and Theoretical Predictions

Prediction of Critical Sizes. In order to use the above model for actual predictions, it is necessary to assign values to the relative velocity U0 this is, at the present level of knowledge, an extremely difficult task since, due to bubble motion (and perhaps the presence of fixed and moving internals in a fluid bed such as, for example, draft tubes) the particle movement in a fluidized bed is extremely complex. Some crude estimates of the relative velocity between particles have been made (Ennis etal., 1991) and these were expressed as 

Using the characteristic parameters shown in the figure, critical transition diameters were calculated. The values obtained were 570 microns for transition from non-inertial to inertial and 1140 microns from inertial to coating, and are seen to be within a factor of 1.5-2 of the experimental data which, in view of the approximate nature of these calculations, is quite remarkable. The constant rate of growth in the non-inertial regime also implies that only growth by nucleation occurred and that coalescence (see Fig. 12) was not prevalent. 

Granule size Increases lower u0 higher binder p higher F 

UViiaoalty d L p iiA 4 tor Oroofcf i ldJ ViaeetliMtar, T p LVT. 7) IurfM t-fiMJM 4 t naJn d dr drop utjjjit Mtihod 

This dependency was also drawn onto Fig. 27 and, as can be seen, the particle sizes measured during this experiment fall more or less on the theoretical line further lowering of the viscosity yielded no agglomerates, as expected. 

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