A hierarchical scheme for integrating process design and control using optimal PID control

Integrating process design and control (IPDC) can help chemical processes operate close to tighter boundaries safely and thus results in numerous economic and operability benefits over the traditional sequential design approach. The last three decades have seen growing interest in the integration of process design and control. However, rigorous methods for solving the problem of IPDC meet challenging mathematical formulations which are computationally intractable. In this paper, a problem of this kind is formulated as a hierarchical optimization problem, which is then solved by keeping the problem size manageable with a two-stage sequential method. The proposed approach is featured using an optimal PID controller which adaptively adjusts suitable control moves for each candidate design. And the control decisions are incorporated in a superstructure-based dynamic optimization formulation which considers both cost and controllability. The application of proposed method is illustrated and compared with the traditional sequential design approach in two chemical processes.