Project Details
Projekt
Model-based process control for dynamic and efficient operation of liquid/liquid mixer-settler systems
Subject Area
Chemical and Thermal Process Engineering
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 504858152
Stirred tanks are probably the most used apparatus in the process industry, e.g., used for extraction processes involving immiscible liquid-liquid systems. In this case, the two phases must be separated in a downstream settler before further processing. The efficient operation of extractive liquid-liquid systems in these mixer-settler units struggles from the contrary requirements of the two unit operations. Tiny droplets and a narrow drop size distribution are ideal for interfacial mass transfer in the stirred tank. In contrast, larger drops are beneficial for fast phase separation in the settler. Parameters influencing this dilemma are, i.a., stirring speed, dispersed phase fraction, flow rates, and residence times. The project aims for a robust and dynamic process control concept based on a suitable system model to tackle this challenge. The novel optimization approach of this project consists of identifying the potential of the dynamic operation of mixer-settlers based on a controlled variation of flow rates and stirrer speed. In the first funding period, the focus was only on the stirred tank. The closed-loop control for batch operation was realized based on an identified process model with a controller that uses a soft sensor to predict the drop size distribution (DSD) in real-time based on features of inline acquired endoscope images. Online measurements of mass transfer based on complement this. In the second funding period, the established experimental setup equipped with reliable measurement and analysis techniques for DSD and mass transfer is continuously expanded and used throughout the entire process chain in continuous operation (WP1). The measurement of all relevant process parameters and variables together with continued improvements in the endoscope measurement technique, combined with the CNN image analysis, will provide the experimental database for the identification of a physics-based or data-driven process model of the complete mixer-settler system (WP2). The developed soft sensor will also be adapted and extended in the experiments (WP3) to predict not directly measurable internal states and to enable closed-loop control in combination with a controller. Based on the results obtained, a control strategy for the efficient operation of the entire mixer-settler system is developed and evaluated, whereby not only standard controllers but also model predictive control will be investigated (WP4).
DFG Programme
Priority Programmes
