Product requirements within the pharmaceutical and life sciences sector change rapidly due to new
drug developments and applications linked to new formulations. This paper presents recent developments in designing
an optimal crystallization process incorporating, at the design stage, customer demands regarding the physical
properties of the crystalline product, notably particle size and particle size distribution. Simple laboratory-scale
batch crystallization experiments were performed to extract the relevant kinetic parameters of nucleation, growth,
and aggregation and to identify further mechanisms such as disaggregation and attrition. Aggregation, considering
also nucleation and growth, was simulated via population balance modeling whereas disaggregation was considered
by quantitative determination of the interparticle forces. Using this new design route, a production-scale
crystallization process comprising a continuously operated air-jet crystallizer with an integrated clarification zone
was successfully commissioned.
69) 5 I 97 5 . 670-674 0 VCH Verlagrgerellrchaft mbY, 3-6945? W e . n ' w w , '097 0009-286W9 70505 -0670 'i 17.!iO +.5 l'0 Tabelle 1. Darstellung der Mittelwerte der PartikelgroBenverteilung von Proben, die wahrend eines Versuches von 30 Minuten mit den Dusen 1 und 2 gewonnen wurden. In Klammern ist die relative Standardabweichung pre, aufgefuhrt (System A). Probenach Probenach Probenach 2 min 16 min 31 min Duse 1, Mittelwert (ure,) 672 (3.9) 673 (3,3) 671 ( 3 , O ) Diise 2, Mittelwert (urel) 670 (4.1) 673 (3,3) 670 (2.8)
A mathematical model for mass transfer and crystallisation in a disperse system is presented under consideration of the moving boundary. The equations describing crystal birth and growth are coupled with the equations for the counter-current mass transfer. Radial profiles of composition as a function of time are generated by numerical solution of the governing equations. By solving the population balance, the average size and also the size distribution of the crystals can be estimated as a f unction of crystallisation time, which is especially important for the precipitation of finely dispersed crystals
Disperse systems in which the crystallization process takes place within droplets of a defined diameter allow the formation of globule‐shaped crystals or agglomerates with narrow particle size distribution, provided that the mass transfer between individual emulsion droplets can be neglected. The crystallization can be initiated by evaporation of the solvent, by cooling, chemical reaction or addition of an antisolvent. For antisolvent crystallizations, a model has been developed in the present work.
Feststoffanteil in der Schutzkolloidlösung mittels High Pressure Liquid Chromatography. Die Versuche zur Überführung von Phytosterolpartikeln in eine wässrige Schutzkolloidlösung zeigten, dass langzeitstabile Nanosuspensionen mit Wirkstoffgehalten von 11 g/dm 3 hergestellt werden können [3, 4].
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