Size enlargement Agglomeration

Producing a GRANULAR matter possible by size enlargement (agglomeration, solidification of liquid droplets, crystallization, etc.) or by size reduction (crushing, grinding, etc.)... 

Each of the mentioned main constmctive elements of spray fluidized bed equipment can be used to manipulate product properties in the desired direction. For example, droplet size and spray pattern have an influence on the particle wetting and on the local liquid distribution in the fluidized bed - thus also on particle growth kinetics, the type of particle size enlargement (agglomeration in comparison to granulation and coating) and product properties (e.g., particle porosity and density, and surface morphology). 

Classification of size enlargement methods reveals two distinct categories (8,39). The first is forming-type processes in which the shape, dimensions, composition, and density of the individual larger pieces formed from finely divided materials are of importance. The second is those processes in which creation of a coarse granular material from fines is the objective, and the characteristics of the individual agglomerates are important only in their effect on the properties of the bulk granular product. 

Pai+icle size enlargement equipment can be classified into several groups, with advantages, disadvantages, and applications summarized in Table 20-36. Comparisons of bed-agitation intensity, compaction pressures, and product bulk density for selected agglomeration processes are highlighted above in Fig. 20-71. 

Both wet and dry extrusion techniques are available, and both are strongly influenced by the friclional properties of the particulate phase and wall. In the case of wet extrusion, rheological properties of the liquid phase are equally important. See Pietsch [Size Enlargement by Agglomeration, John Wiley Sons Ltd., Chichester, 346 (1992)] and Benbow et al. [Chem. Eng. Sci., 422,2151 (1987)] for a review of design procedures for dry and wet extrusion, respectively. 

Pietsch, W., 1991. Size enlargement by agglomeration. Chichester John Wiley. 

Because interparticle forces in very fine powders make them very difficult to handle, the effective particle size is frequently increased by agglomeration. This topic is discussed in Section 2.4 on particle size enlargement in Chapter 2. 

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