The optimization of seeded batch crystallization when growth rate is size-dependent
Date Issued
2012
Date
2012
Author(s)
Ting, Wei-Lun
Abstract
In this work, the optimization of seeded batch crystallization processes is investigated when crystal growth rate is size-dependent. The process model with size-dependent growth was solved using the Quadrature Method of Moment (QMOM), Method of Characteristics (MOCH) and Duhamel’s Principle as proposed by Qamar et al. [Chem. Eng. Sci., 2009; 64: 3659-3667]. Four systems were studied: a dimensionless model based on previous work by Ward et al. [AIChE J., 2011; 54 (3) 606-617], and three case studies based on real crystallization kinetics reported in the literature.
Investigation of the dimensionless model using the objective of minimizing the nucleus-grown crystal mass shows that the size-dependency of the growth rate has only a small effect on the shape of the optimal supersaturation trajectory, i.e. an approximate, size-independent model can be used for the optimization with little error. This is advantageous because optimizing the size-independent model requires much less computational effort. Results from the real case studies also support this conclusion.
A modification to the procedure of Qamar is also proposed: By calculating a parameter exactly instead of using an approximation recommended by Qamar, the accuracy of the approximation can be significantly improved without a significant increase in computational effort. The error is reduced from more than 60% to less than 1% in the case where the nucleated crystal mass is large. Finally, it is also shown that optimization over the supersaturation trajectory is preferable to optimization over the temperature trajectory.
Subjects
seeded batch crystallization
optimization
size-dependent
crystal growth
non-dimensional system
supersaturation
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-101-R99524053-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):6a6b7afa263112629c7b38c25f055fea