Spray-type agglomerator

As the name implies, this technique involves the formation of a falling curtain of powder into which is directed a jet of steam, water spray or mist to wet and agglomerate the product. Small, cluster-type agglomerators are formed. 

Orifice distributors with bottom perforations should be avoided in plugging services, even when filters are installed there have been cases where small solid particles passed through the filter, agglomerated in the pan or troughs, and blocked perforations. In pressure distributors, particularly the spray type, a filter is often [but not always (297)] sufficient. 

Agglomerate breaking device shown in broken line. Spray nozzle shown in dotted line. Tumblers of this type available plain or with either or both of the above features. 

A similar technique has been applied to the generation of monodisperse suspensions in water. This type of method was first used in medical field and then widely used to spray monodisperse solid particles such as polystyrene latex particles. Aerosols of solutes have also been produced by atomizing solutions of salt, sugar or methylene blue dye dissolved in water. In practical operations, a low concentration of solid particles in a solvent is recommended in order to avoid possible agglomeration of suspensions in the solvent. 

Synthetic hydroxyapatites were prepared by the method of Hayek and co-workers (7, 8), modified to produce a product of small particle size. The products were isolated by washing the gel slurry with water until free of nitrate ion. The resultant suspensions were then spray-dried with a Minor Type 53 Niro Atomizer (Copenhagen, Denmark). The resultant dry products were in the form of porous, spherical polycrystalline agglomerates of 5 to 8 fi average diameter. The specific surfaces of these products ranged from 104 to 180 meter2/gram. 

Sodium Sulfate. Although considered a weak builder by some manufacturers, sodium sulfate (Na2S04) contributes little to detergent performance. It is commercially available from natural sources and as a byproduct from rayon processing. In dry mix and agglomerated type products, sodium sulfate is used to improve finished product flow characteristics. In spray-dried products, sodium sulfate acts as an inert filler and aids in density control. 

Numerous equipment types can be used for agglomeration, including horizontal ribbon and vertical mixers, rotary drums, zig-zag mixers, and pan agglomerators. Horizontal ribbon mixers as shown in Fig. 36.41 are used primarily for dry mix formulating, where only limited agglomeration occurs. They are comprised of a U-shaped trough and a ribbon or paddle-type agitator. Liquids are sprayed onto the surface of the dry material and slowly dispersed into the mix. Mixer operations can be either batch or continuous. 

Manufacturing techniques employed in producing instant products include spray-coating dry powders with fluid lecithin products, cospray drying powders with more hydrophihc lecithins such as the oil-free forms, or hydroxylated lecithin, and agglomeration of the powder with an aqueous dispersion of a hydrophihc lecithin. Some types of powders, for example, starches, gums, and chocolate drink mixes, require agglomeration with an aqueous dispersion of lecithin to achieve optimum wettabihty and dispersibility. 

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