Biology Reference
In-Depth Information
show that low rates of reactant addition, and more importantly a low reac-
tant concentration, result in a larger product size. The fact that the product
size increases if the reactant concentrations are reduced can be explained by
the fact that lower reactant concentrations lead to lower supersaturation at
the feed point, which in turn leads to a lower nucleation rate. Fewer parti-
cles will be sharing the crystallized mass. The local mixing intensity is at
the maximum close to the impeller. At the surface (where addition fre-
quently takes place in industrial processes) the mixing is often poor.
However, too much mixing will result in fragmentation and breakage of the
crystals.
Crystallizers and crystallization processes cannot be designed simply
theoretically, any more than they can be designed only on the basis of
experiment. At present, the knowledge required to design, construct and
run a full-scale crystallizer must be obtained from well-designed labora-
tory experiments on the system in question, an interpretation of the results
based on fundamental crystallization principles, relevant half-scale exper-
iments, and sometimes even from supplementary full-scale experiments.
Conclusions
In this chapter, we have presented the fundamentals of crystallization as it
applies to processing of fine organic chemicals and low molecular phar-
maceuticals. In addition some aspects on processing have been discussed.
Crystallization of larger molecules and proteins are governed by the same
fundamental mechanisms. Hence, the presentation here may contribute to
a mechanistically sound analysis and development of the crystallization of
proteins.
References
Baldyga J, Bourne JR. (1986) Principles of micromixing. In NP
Cheremisinoff (ed).
Encyclopaedia of Fluid Mechanics
, 1.
Bohlin M, Rasmuson ÅC. (1986) Direct Contact Cooling Crystallization;
l. C. Report B4 to IKF, Department of chemical engineering, KTH.
Search WWH ::
Custom Search