Sensor development and multi-sensorial control for batch suspension crystallization

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Product properties in suspension crystallization processes are notoriously difficult to control for the following basic reasons: (i) the complex underlying physics makes mono-causal feedback control targeting product quality very difficult. (ii) the scarcity of suitable sensors hinders monitoring the full control-relevant process state. The main objective of the project is to establish a holistic model-based multivariable control strategy for suspension crystallization. In the course of the project two novel sensor types will be developed: (i) Electrical impedance spectroscopy shall be established as a multipurpose sensor making total solid concentration and several dissolved compounds accessible with one measurement. (ii) Direct single crystal growth rate monitoring will be established giving access to growth rate without the necessity of any concentration information. Additionally, direct single crystal growth rate monitoring will be tested for being capable to act as a currently non-existent crystal purity sensor. Both sensors will be integrated in a multi-sensorial model-based control approach. The underlying population balance model will be identified online using the available sensors.