A process design framework for considering the stability of steady state operating points and Hopf singularity points in chemical processes

• Quantitative index was constructed to describe stabilities of stable steady state operation points.
• Hopf singularity points were considered as constraint in process design optimization problem.
• Design framework was proposed for process design.

In this paper, operating point stability and Hopf singularity points were considered in chemical process design. First, a process design framework was proposed. For processes that do not meet Hopf singularity points, a quantitative stability index was established to quantify the stability in dynamic systems derived from an accurate dynamic model. This was then validated based on the time needed for convergence to a previous stable point under a given disturbance. A fermentation process was studied to show the quantitative index approach. This was followed by a methyl methacrylate polymerization reactor process, illustrating and extending the applicability to a multi-objective optimization problem, in which both economic and stability reasons were considered. For processes involving Hopf singularity points, an optimization method considering the influence of the Hopf singularity point range was proposed. A Zymomonas mobilis fermentation was studied to demonstrate the effectiveness of the proposed method.