Crystals are particles structured with multiple faces that often have different surfacechemistry and hence varied growth rates during crystallisation. It is possible tomanipulate the growth of individual facets e.g. Via the introduction of tailor-madeadditives which via changes in the molecular recognition for the different crystal habitfaces effect a reduction in the growth rate of a specific face, providing a means forcontrol of the shape as well the size of the final crystalline product. However theprediction of crystal shape has previously been restricted to single crystals. On the otherhand, population balance (PB) modelling of crystallisation has traditionally been monodimensional,I.e. Based on the assumption that the crystals in a reactor all have aspherical shape. Recently a few researchers have reported two-dimensional (e.g. Lengthand width) PB modelling for rod-like crystals. This paper presents a morphological (orpolyhedral) population balance model for modelling the dynamic size evolution in allface directions. The morphological PB approach uses the crystal shape information for asingle crystal obtained from morphology prediction or experiment as the initial facelocations as well as face growth rates to predict the shape evolution of the crystalpopulation. For every time instant during crystallisation, the shape prediction uses itsshape at the last time moment and the growth rate of each face. The methodology isintroduced by reference to potash alum (Kal(SO4)2·12H2O) for which literature data isavailable for comparison and validation.
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