Dynamics of a True Moving Bed separation process: Linear model identification and advanced process control

- Strategy to identify linear models based on the transfer function for a SMB unit.
- Simultaneous control of the unit purity and recovery in extract and raffinate streams.
- In order to identify the set of MVs a mathematical method based on the orthogonal projection was applied.
- Methodology enables the easy identification of transfer functions at the process optimal point.
- The MPC can control the process in both the servo and regulator problems cases.

The control of Simulated Moving Bed (SMB) units is challenging due to their complex dynamic behaviour and the difficulty of measuring their main properties. Furthermore, for the SMB units, the transfer function identification when the unit is operating at its optimal point is not easy to be done through the usual way. This work presents the development of a novel strategy to identify transfer functions of TMB/SMB and its application on classical linear model predictive controllers (MPC). However, for the process in study, due its unique dynamics, only the identification of the linear model is not enough to solve its control problem. Therefore, it is proposed a modification in the MPC prediction, that consists in a strategy based on a switching system where the most adequate transfer function is employed in the controller to overcome the problems related with the process dynamic behaviour. The results show that the used methodology enables the easy identification of transfer functions at the process optimal operating point and that the MPC can control the process in both the servo and regulator problem cases. It is also showed that the transfer function identified can be applied in the control of a SMB unit with four columns, under its optimal conditions.