Tailoring Morphology and Particle Size Distributions via Crystallization
Advancing the chemical engineering fundamentals
Crystallization (T2-9)
Keywords: Crystallization, Kinetics, Population Balance, in-situ Measurement Probes, Model based Experimental Analysis
Crystallization from solution is not only a standard separation technique it is also a powerful method to design and tailor particle properties that satisfy consumer needs. Beside morphology, purity and form, the mean particle size and particle size distribution are important properties of a crystalline product. However, this high potential in tailoring specific particle properties still requires high resource expenditure in form of number of experiments and amount of starting material to retrieve the necessary information. This is mainly due to the simultaneously occurring kinetic processes of nucleation, growth, agglomeration, breakage, attrition and where applicable polymorphic transformation.
The objective of this study is to speed up the design of crystallization processes by combining “in-situ” measurement techniques, time dependent batch trials and a model based experimental design and analysis strategy. Thereby the required number of experiments can significantly be reduced by maximizing the information content of the experimental data at the same time. Although each technique for its own has been widely validated and proven to be beneficial, the combination is seldom employed.
The crystallization of ammonium chloride that has rarely be study in literature will serve as a model system. Experimental data are recorded using a batch laboratory crystallizer equipped with an “in-situ” MTS 3D-ORM and a SensoTech LiquidSonic probe measuring chord length distribution and supersaturation, respectively.
Experimental results will focus on the crystallization behaviour of ammonium chloride from a kinetic as well as particle properties point of view. It will be presented how the morphology can successfully be changed from an undesired dendritic to an elliptical shape using an additive, leading to a significantly reduced rate of crystal breakage. Furthermore it will be illustrated how different process conditions alter agglomeration kinetics and how it can be avoided. The gained information allows subsequently to tailor morphology and particle size distribution that are key product properties. The experimental work and optimization of crystal properties is supported by using a model based experimental analysis strategy. The model is given by a two-dimensional population balance model, incorporating growth, nucleation and attrition. Kinetic parameters will be presented.
Presenting new experimental data, the study will demonstrate how the crystal properties of ammonium chloride can be successfully tailored. Moreover, it will be highlighted that the combination of “in-situ” measurement techniques, time dependent batch trials and model based experimental design and analysis strategy is a powerful tool. It allows to base decisions on all available knowledge that is available in form of experimental data and differential equations (i.e. population balance). This leads to a significantly reduced time for the development and optimization of new crystallization processes.
Presented Wednesday 19, 15:40 to 16:00, in session Crystallization (T2-9).
