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978-3-8439-2891-5, Reihe Technische Chemie
Measurement and Control of Agglomeration for the Design of Crystalline Products
183 Seiten, Dissertation Technische Universität Dortmund (2016), Softcover, A5
In crystallization a high effort for optimization and process control is made to achieve the desired quality characteristics of the crystalline products. The quality, which is defined by the crystal form and size, the crystal size distribution (CSD) and purity, is primarily dominated by crystallization conditions, and affects further downstream processes. The CSD e.g. is an important quality criterion for filterability and flowability. In general, the CSD is characterized by characteristic values, like median crystal size d50 or width of CSD d90-d10. However, no information about the particle morphology or the amount of agglomerates is given by these characteristic values. This lack of information about the particle morphology in CSD can lead to misunderstand the crystallization process, especially when agglomeration takes place during solid-liquid separation or drying, and an off-line CSD measurement technique is used. Through agglomeration the width of CSD might be broadened and mother liquor inclusions can lead to less purity.
Therefore, to avoid a misconception of crystallization processes in this thesis the agglomeration degree distribution (AgD) is introduced as new quality criterion to allow a quantitative characterization and comparison of crystalline product batches with different morphology. By using the AgD clear statements whether a material system tends to agglomerate during crystallization and/or downstream process can be made on basis of simple experiments.
Furthermore, the agglomeration behavior of two material systems, characterized by different crystal habit and d50, is systematically investigated. The results show indicated by the AgD that the final product can be – despite similar characteristics of the CSD – highly different. Consequently, the characterization of the product quality by the CSD alone is insufficient and the quantification of agglomeration over the whole process chain is essential for reliable product design.