IRF: Institutional Repository FHNW
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Modeling nucleation, growth, and ostwald ripening in crystallization processes: A comparison between population balance and kinetic rate equation
(American Chemical Society, 01.10.2013) Vetter, Thomas; Iggland, Martin; Ochsenbein, David R.; Hänseler, Flurin S.; Mazzotti, Marco
In this work, we investigate a comprehensive model describing nucleation, growth and Ostwald ripening based on the kinetic rate equation and compare it to commonly used population balance equation models that either describe nucleation and crystal growth or crystal growth and Ostwald ripening. The kinetic rate equation gives a microscopic description of crystallization, i.e., the process is seen as an attachment and detachment of crystals of different sizes to and from each other, thereby changing their size. A hybrid model is employed in which the discrete kinetic rate equation is used to describe the smallest particle sizes while a Fokker-Planck equation is used to approximate the kinetic rate equation at larger particle sizes. This allows us to cover crystals in a size range starting from a single molecule up to macroscopic particle sizes and to solve the model numerically with reasonable computational effort and great accuracy. We show that the model based on the kinetic rate equation describes the processes of nucleation, crystal growth, and Ostwald ripening accurately in a single, continuous model. This is set in contrast with classical population balance equation models that require, due to their underlying assumptions, separation of the process of nucleation from the process of Ostwald ripening. We compare the results of the two models for different sets of parameters (such as different solubilities, surface tensions, initial supersaturations, and seed distributions). Using these results, we assess the advantages and disadvantages of models based on the kinetic rate equation in comparison to models employing a population balance equation.
01A - Journal article
Regions of attainable particle sizes in continuous and batch crystallization processes
(Elsevier, 17.03.2014) Vetter, Thomas; Burcham, Christopher L.; Doherty, Michael F.
Process alternatives for continuous crystallization, i.e., cascades of mixed suspension, mixed product removal crystallizers (MSMPRCs) and plug flow crystallizers (PFCs), as well as batch crystallizers are discussed and modeled using population balance equations. The attainable region approach that has previously been used in the design of chemical reactor networks and separation systems is applied to the above-mentioned alternatives for crystallization processes in order to identify attainable regions in a diagram of mean product particle size vs. total process residence time. It is demonstrated that the boundaries of these attainable regions can be found numerically by solving appropriate optimization problems and that the region enclosed by these boundaries is fully accessible. Knowing the attainable region of particle sizes, it is possible to generate feasible process alternatives that allow specific particle sizes to be obtained in a given process configuration. The attainable regions presented in this paper are useful to determine whether a desired mean particle size can be achieved in a specific crystallizer type. The concept of the attainable region is illustrated on three case studies: the cooling crystallization of paracetamol grown from ethanol, the anti-solvent crystallization of L -asparagine monohydrate from water using isopropanol as the anti-solvent and the combined cooling/anti-solvent crystallization of aspirin from ethanol using water as the anti-solvent.
01A - Journal article
Digital inequalities among older adults
(Edward Elgar Publishing, 19.03.2026) Seifert, Alexander; Jokisch, Mario R.; Poli, Arianna; Foster, Liam; Motel-Klingebiel, Andreas; Luo-Hermanson, Baozhen M.
04A - Book part
Stärkung der Sozialen Arbeit in der interprofessionellen Suchthilfe in der Schweiz. Ein Beispiel kooperativer Wissensproduktion zwischen Praxis und Wissenschaft
(ZKS-Verlag, 2025) Abderhalden, Irene; Krebs, Marcel
01B - Magazine or newspaper article