Mixing Effects on Nucleation

For mass transport, i.e., solution concentration profile and impact on crystallization, they include 

Although many variations of mixing systems have been used for crystallization processes, the three primary types that are discussed in this book are the stirred vessel, fluidized bed, and impinging jet devices. Each of these utilizes different mixing environments to achieve the desired local and global conditions. 

The predominant system in the pharmaceutical industry is the stirred vessel. Fluidized beds (Chapters 7 and 11) and impinging jets (Chapter 9) fill specific mixing requirements, as indicated in Table 6-1. 

In a mixed solution without crystals present and at constant supersaturation, increased mixing intensity can reduce the induction time—the time elapsed after mixing to create supersaturation to the time crystals first appear. Induction time decreases up to a critical speed, after which it remains unchanged (Myerson 2001, p. 145). Additional discussion may be found in Chapter 4. 

Since secondary nucleation is dominant as soon as nuclei appear, the nucleation mechanisms become virtually impossible to characterize in an industrial operation. In addition, any seeded crystaUization is by definition secondary even though some nuclei may simultaneously form by a primary or other secondary mode mechanism. Therefore, the majority of this discussion will focus on secondary nucleation. 

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Mixing effects on nucleation and growth in crystallization (Chapter 17)... 

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