Process and Variables in Granulation

Factors affecting the fluid-bed granulation process can be divided into three broad categories  

Binder Different binders have different binding properties and the concentration of an individual binder may have to be changed to obtain similar binding of primary particles. Thus, the type of binder, and binder content in the formulation and concentration of the binder have major influence on granule properties. These properties include friability, flow, bulk density, porosity, and size distribution. 

Diluted binders are preferred because they facilitate finer atomization of the binder solution, provide control of the particle size, reduce friability and increase the bulk density, even though the tackiness or binding strength may suffer (8,68,78,82,82,97). 

Design The availability of the fluid-bed processors from different suppliers of the equipment is essentially similar. The differences in design of different suppliers sometimes provide difficulty in scaling-up from the laboratory units to production units in a linear scale. 

To fluidize and thus granulate and dry the product, a certain quantity of process air is required. The volume of the air required will vary, based upon the amount of material that needs to be processed. The ratio of drying capacity of the process air and quantity of the product needs to be maintained constant throughout the scaling-up process. However, some suppliers of the equipment provide higher drying capacity for their laboratory unit 

Solvent Solvent boiling point ( C) Density (g/mL) Heat of vaporization (kcal/g) 

The following general guidelines for filter cleaning frequency and duration are recommended  

Single-bag shaker unit. Frequency, 2-10 min between filter cleaning, 5-10 sec for shaking. This may vary as the fine powders form granules, and the frequency between the shakes or duration of shaking interval, can be extended. In any case, the occurrence of a collapsed bed should be kept at a minimum in a single-shaker unit. 

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