Granulation process

Shear forces. Shear rates. Moisture, Temperature Liquid/powder/granute phases. Granule size distribution 

Scale Granule Size and Primary Feed Particles 

All else being equal, plug flow continuous and batch well mixed processes should produce identical size distributions. It is very difficult to achieve uniform mixing in practice, with properly operating fiuidized beds possibly coming the closest. 

With regard to bed weight, forces in fluid beds, and therefore consolidation and granule density, generally scale with bed height. As a gross nfle of thumb, ideally, the power input per unit mass should be maintained with mixer scale-up, related in part 

Effect of changing key process variables Fluidized beds (including coating and drying) High-shear mixers 

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Granular TSP (—6 + 16 mesh (1.19 to 3.35 mm dia)) is preferred for direct appHcation and is used in bulk blend fertilizers. A widely used slurry granulation process, the Dorr-OHver process, is illustrated in Figure 11. The ground rock is mixed with 38—49% P2 5 series of reaction vessels. 

Fig. 16. Steam granulation process for production of granular mixed fertilizers from dry, pulverized feed materials (7). A granulator producing 12 t/h would...

Some of the principal forms in which sulfur is intentionally incorporated in fertilizers are as sulfates of calcium, ammonium, potassium, magnesium, and as elemental sulfur. Ammonium sulfate [7783-20-2] normal superphosphate, and sulfuric acid frequendy are incorporated in ammoniation granulation processes. Ammonium phosphate—sulfate is an excellent sulfur-containing fertilizer, and its production seems likely to grow. Some common grades of this product are 12—48—0—5S, 12—12S, and 8—32—8—6.5S. 

Graining, flaking, and spraying have all been used to make soHd ammonium nitrate particles. Most plants have adopted various prilling or granulation processes. Crystallized ammonium nitrate has been produced occasionally in small quantities for use in specialty explosives. The Tennessee Valley Authority developed and operated a vacuum crystallization process (25), but the comparatively small crystals were not well received as a fertilizer. 

Granulation processes offer a number of important advantages. The most significant are decreased pollution problems and the abiUty to produce granules of almost any reasonable size allowing close size matching with granular ammonium phosphates and potassium chloride in the preparation of NPK fertilizers (26). 

TABLE 20-39 Growth and Breakage Mechanisms in Granulation Processes... 

Extent of Noninertial Growth Growth by coalescence in granulation processes may be modeled by the population balance. (See the... 

The efficacy of chitosan in the treatment of leg ulcers stems from its antiinflammatory action and stimulation of epithehahzation. Chitosans stimulate the granulation process and the epidermis formation, thus accelerating heahng, even in the elderly suffering from chronic venous insufficiency, the... 

Frilling towers convert molten materials into droplets and allow them to solidify in contact with an air stream. Towers as high as 60 m are used. Economically the process becomes competitive with other granulation processes when a capacity of 200- 400 tons/day is reached. Ammonium nitrate prills, for example, are 1.6-3.5 mm dia in the 5-95% range. 

Enzymes. Where tablets are not naturally very cohesive and have thus been manufactured by a wet granulation process involving one of the binders listed in Table 8, addition of small quantities of appropriate enzyme may be sufficient to produce rapid disintegration. It has also been proposed that disintegration action might result from expansion of the entrapped air due to generation of heat of wetting when the tablet is placed in a fluid. This concept has received little attention. 

The manufacturing process is sometimes discussed in terms of the characteristics of the active ingredient, e.g., the need for nonaqueous granulation processes, the need for controlled humidity in the manufacturing environment. The number of different manufacturing sites requested is mentioned in the assessment reports. Special manufacturing processes such as extrusion/ spheronization are mentioned in the EPARs. 

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