A new scheme for process simulation by optimization: distillation as an example

Commercial flowsheet simulators suffer from limitations in problem formulation flexibility and numerical instabilities which potentially turn process simulation into a tedious task. In this work, we address these problems and present a new scheme for integrated process simulation and optimization. The new method is developed here for distillation but can be extended to other unit operations. It utilizes numerically stable distillation calculations based on the solution of a sequence of fixed-point problems. Using the ideas of the shooting method the process simulation is embedded into an optimization problem and hence feasible design parameters are found by applying suitable nonlinear optimization algorithms. Systematic studies of typical examples of distillation processes are presented including also flowsheets with several columns. The new method is shown to be flexible in terms of problem formulation and more robust than those presently used in process simulators.