Modelling for controller design in tray distillation. II. Comparison of lumped and distributed parameter model performance

For pt.I see ibid., p.301-4. An algorithm for fitting the parameters of a fourth-order lumped parameter model (for a column comprising only a single-state rectifier and stripping section) derived in part I, to responses computed for a multitray column, is demonstrated. The multivariable first-order lag approximation of D.H. Owens (1975) is used as a basis for control system design and shown to produce near-identical closed-loop responses. The fitting algorithm is shown also to cope with nonminimum-phase responses generated by packed columns for which the multivariable first-order model is totally inappropriate. The fourth-order lumped parameter model for either type of column therefore provides a good basis for column controller design in general