Concentration based flow control in acoustic separation of suspensions

Acoustic separation is a relatively new method for recovering valuable particulate matter from suspensions. This separation method is mainly used in medical technology, but may well be applicable as water purification and material recovery technique. The key question then is what separation efficiency can be reached and whether this can be realised in an energy-efficient way. In the current study, a commercially available acoustic separator, named BioSep, which employs ultrasound enhanced sedimentation, was used. With the aim to achieve a high separation efficiency with minimal energy consumption, a model-based open-loop switching control strategy was designed for the BioSep, using a numerical–experimental approach. Firstly, a dynamic BioSep model structure was derived from mass balances and its system properties were studied. Then, the unknown system parameters were estimated from steady state and dynamic experimental data and subsequently, the switching times of the control input were determined. The model with switching control outputs was then validated by experiments. Finally, the control strategy was implemented in the experimental setup and tested using suspended potato starch. Results showed that the optimal control strategy reached a mass separation efficiency of 96%, which was an improvement of 4% with respect to the initial settings, while using less energy.