(322a) An Advanced MPC Controller Design for PSA Operation

Pressure swing adsorption (PSA) is a flexible, albeit complex gas separation system (Ruthven, 1994). Due to its inherently dynamic nature of reaching only a periodic steady state, the design of an advanced model based controller for its operation remains quite a challenging task (Torre, et al., 2005).

This work focuses on the design of an explicit model predictive controller (MPC, Pistikopoulos et. al., 2004, 2007a, 2007b, 2008) for the control of the PSA system in varying operating conditions. To accomplish this task, high fidelity, first principle based mathematical model of a realistic PSA separation system is developed. It involves four adsorbent beds, five components namely, H2, CO2, CO, CH4, N2, and undergoes a cyclic operation consisting of nine process steps.

We follow a unified framework for the design and validation of explicit MPC (multi-parametric MPC), featuring a step by step methodology. First, a high fidelity PDAE based model is built based on which an approximate model is developed by applying a suitable system identification step. Then a model predictive control step is formulated for the reduced model where our multi-parametric algorithms are applied to derive a suitable and robust explicit MPC controller. By incorporating the explicit controller expressions (control laws) in the original PDAE model, a validation step is then carried out. This involves performing offline computational simulation studies. Comparisons of the derived explicit MPC (multi-parametric MPC) controller with standard conventional controllers (such as PID) are also presented.

References:

Pistikopoulos, E.N., Bozinis, N., Dua, V., Perkins, J. & Sakizlis, V. (2004). Improved Process Control, European Patent EP1399784.

Pistikopoulos, E.N., Georgiadis, M. & Dua, V. (2007a). Multi-parametric Programming: Theory, Algorithms and Applications, Weinheim: Wiley-VCH.

Pistikopoulos, E.N., Georgiadis, M. & Dua, V. (2007b). Multi-parametric Model-based Control: Theory and Applications, Weinheim: Wiley-VCH.

Pistikopoulos, E.N., Bozinis, N., Dua, V., Perkins, J. & Sakizlis, V. (2008). Process Control Using Co-ordinate Space. United States Patent and Trademark Office Granted Patent No US7433743.

Ruthven, D. M.; Farooq, S. & Knaebel, K. S. (1994). Pressure Swing Adsorption, Wiley-VCH

Torre, V. D. L.; Fox, V. G.; Bandoni, J. A. & Biegler, L. T. (2005). Model Predictive Controller for Periodic Adsorption Processes. ENPROMER 2005, 14-18 August 2005, Rio de Janeiro: Brazil.