In this paper, an optimisation-based approach is developed for the determination of the cyclic steady-sate (CSS) of a pressure swing adsorption process (PSA). It consists in treating the simulation problem as a single dynamic optimisation problem where the performance index is the CSS condition, the decision variables are the state variables at the start of the cycle and the constraints are given by the process model equations with associated initial conditions. The resulting optimisation problem is solved using a gradient-based non linear programming (NLP) method, e.g. SQP method, where the gradients are computed by means of four different methods: finite differences, numerical and analytical sensitivities and adjoint system methods.

This paper addresses the optimization of a batch copolymerization reactor of styrene and α-methylstyrene. The reactor is equipped with a jacket for heat exchange and, thus, for temperature control. The performance index is the batch period, and the decision variable is the jacket inlet temperature. The constraints involved include the process model, the polymer quality, the final monomer conversion rate, the heating/cooling rate of the reactor and upper and lower bounds of the variables. The optimization method is a direct method with a sequential strategy known as control vector parametrization method. The optimal profiles are determined with great care in terms of treatment and fulfilment of constraints. The results show a substantial improvement with respect to the complete discretization method previously used.