FLUIDIZED-BED GRANULATION - THE IMPORTANCE OF A DRYING ZONE FOR THE PARTICLE GROWTH-MECHANISM

In fluidized bed granulation, either surface layering or agglomeration may lead to granule growth. Agglomeration will occur if a wet particl e collides with another particle and is bound by a liquid bridge which becomes solidified during the subsequent drying period. In the case o f a two-fluid-nozzle spraying upwards into the fluidized bed, wetted p articles may be transported pneumatically by the nozzle air above the bed plenum and dry before they fall down in the outer regions of the b ed. Hence, a drying zone above the fluidized bed is formed, leading to significantly less agglomeration. (C) 1998 Elsevier Science S.A.