(699c) Study of Crystallization Kinetics Within a Generic Modelling Framework

Crystallization is
frequently applied in the production of salts and/or active pharmaceutical
ingredients (API). In recent years the monitoring and analysis of
crystallization operations has gained much attention because of the growing
need to control more sophisticated production lines. Crystallization operations
involve a combination of different phenomena and the modelling of these can be
combined to form the crystallization operation model. For this purpose
different kinetic models, for example growth, nucleation, agglomeration and
breakage, are required to analyse the crystallization operation. These models
require data, which may be available in different forms, in order to describe
the kinetics, which determines properties of the process outcome. Growth of the
crystals occurs in multiple dimensions and the relative rates of growth in each
direction and other kinetic phenomena such as agglomeration and breakage of the
formed crystals control the shape and size distribution of the final product.
Including more than one dimension in the crystallization will allow a more
general description of the kinetic phenomena and the crystallization operation.
This requires models for kinetics in multiple dimensions and data to estimate
the model parameters. In order to have a full description of a crystallizer, a
combination of constitutive (kinetic) models is needed. Such a description is
possible within a generic framework where the models can be combined, reused
and identified utilizing a kinetic model library for kinetic models and data. From
the data in this library new models may also be derived and identified. The
framework has been established and tested for simulation of selected crystallization
processes.

The objective of this
paper is to present a modelling procedure for systematic development,
validation and analysis of constitutive (growth, nucleation, agglomeration and
breakage) models. In this procedure, data and known crystallization kinetic
(constitutive) models representing specific chemical systems are studied with
respect to operational variables and model parameters. Based on the analysis
results, new kinetic models are generated, and using available data, the model parameters
are regressed. The modelling framework allows kinetic models representing
different kinetic phenomena to be combined in different ways so that the sensitive
kinetic model parameters can be identified and their effect on crystallization operations
analysed. That is, the importance of different (multiple) phenomena occurring
within any crystallization operation can be studied with and without including the
mass and energy balance equations. Also, the identification of any single
phenomena occurring within a wide range of crystallizer operations is
permitted. A database of kinetic models has been created and combined with the
generic mass and energy balance models allowing the validation, use and reuse
of the selected kinetic models.

The presentation will
highlight a systematic analysis and comparison of kinetic models, their
parameters and the involved variables under various crystallization operation
scenarios. The simulated results of crystal growth and/or
agglomeration/breakage, for example, will be presented for different choices of
operational variables, such as, temperature, mass transfer, seeding and present
particles. Details of the kinetic model library together with the available
data will also be highlighted.