Modeling of Granulation Processes

Most process engineering problems involve mass and energy balances. However, in particulate processes, especially in cases where particle number rather than mass is of primary importance, a balance over the population of materials of a given size in the system is often necessary. This is particularly 

The population follows the change in the granule size distribution as granules are bom, die, grow, or enter or leave a control volume, as illustrated in Fig. 34. The number of particles between volume v and v - dv is n(v)dv, where n(v) is the number frequency size distribution, or the number density. The population balance for granulation is then given by 

The left-hand sideofEq. (40)isthe accumulationofparticlesofagivensize. The terms on the right-hand side are, in turn, the bulk flow into and out of the control volume, the convective flux along the size axis due to layering and attrition, the birth of new particles due to nucleation, and birth and death of granules due to coalescence. 

Size Change Mechanism Relevant Governing Equations Reference and Comments 

Coalescence Typical Growth Kernels Kapur and Fuerstenau (1964) 

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The authors would like to acknowledge that the section dealing with population balance modeling of granulation processes is an abbreviated version of material prepared by Dr. J. D. Litster, University of Queensland, for a joint short course given by Dr. B. J. Ennis and Dr. J. D. Litster. 

Powder flow patterns in wet granulation can be studied using positron emission particle tracking. Eventually, this and similar techniques can be used to validate various mathematical and statistical models of the process. 

With both models of granule formation, the polyester synthase is converted into an amphipathic molecule upon polyester chain synthesis and a self-assembly process occurs either in the membrane or in the cytosol (Figure 3.5). Small water-insoluble and spherical inclusions are formed with an amorphous polyester core and polyester synthase covalently attached to the surface [58, 59], (Figure 3.5). 

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