Granulating disc

Agglomeration (or balling, granulating) disc (or pan) Although similar to the balling drum, the pan features distinct differences in growth phenomena and... 

While equation (71) represents the data points " well (Figure 114), it seems (Figure 118) that the rim height of larger granulating discs tends to deviate slightly from equation (75). 

Equation (61), derived in Section 4.2.1.3.4 for the balling drum, can also be applied for the granulation disc. In contrast to drums where the loading is very small (( > = 0.1 to 0.3), Bhrany found that the mass in a pan is proportionate to the square of its diameter ... 

Figure 119. Throughput C of granulating discs as a function of pan diameter D. Comparison of data obtained by Klatt " and Corney ...

Figure 120. Relationship between throughput C of granulating discs and pan diameter D Data points according to Ries. ...

As in the case of balling drums and, to a certain degree, in mixers, shape and size depend on the growth mechanism taking place in the granulating disc. 

Often, only the easily determined moisture content is measured and reported. Such data normally show a wide scatter which may result in misleading conclusions. After introducing the pellet porosity and calculating the liquid saturation, the scatter is reduced to yield more reproducible data (compare Table 11). At optimum operation of the granulation disc, pellets feature nearly constant saturations between approximately 80 and 95 7o. The lower than expected saturation figures are caused by air entrapped in the structure by pores that are completely filled with liquid and surround such areas. If moisture contents deviate considerably from these values, agglomerates with low quality are produced (compare Figure 128). 

Platelets are heavily granulated disc-like cells that aid in intravascular clotting. Like the erythrocyte, platelets lack a nucleus. Their function is discussed in the following chapter. Platelets arise by budding of the cytoplasm of megakaryocytes, multi-nucleated cells that reside in the bone marrow. 

Relative Merits of Disc versus Drum Granulators. 20-76... 

Tumbling granulators Drums Discs 0.5 to 20 Moderate 0.5-800 ton/hr Very spherical granules Fertilizers, iron ore, non-ferrous ore, agricultural chemicals... 

Drum and disc granulators generally operate in continuous feed mode. A key advantage to these systems is the abihty to run at large scale. Drums with diameters up to four meters and throughputs up to 100 ton/hr are widely used in the mineral industiy. 

FIG. 20-81 Atypical disc granulator Capes, Particle Size Enlargement, Elsevier, 1980). 

Other advantages claimed for the disc graniilator include low equipment cost, sensitivity to operating controls, and easy observation of the granulation/classification action, all of which lend versatility in agglomerating many different materials. Dusty materials and Chernies reactions such as the ammoniation of fertilizer are handled less readily in the disc granulator than in the drum. 

In terms of processing there is no need for pre-drying PCHE granules, a standard extruder screw as used for polycarbonate may be used and discs are said to release well from the mould. Question marks remain on the oxidative stability of the polymer and on the quality of adhesion of the reflective layer but Dow claim that metallising is possible. 

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