Dynamic precompensation and output feedback control of integrated process networks

In integrated process networks, the presence of large flowrates induces a time-scale separation of the dynamics where the individual units evolve in a fast time scale while the overall process evolves in a slow time scale. The slow dynamics of such networks are modeled by a high index differential algebraic equation system which, in the case of cascaded control configurations, has a control dependent state-space. We propose a minimal-order dynamic extension to obtain a modified DAE system of index two with a control invariant state-space that can be subsequently used as the basis for controller design. We illustrate this method for a distillation column with large recycle where the top and the bottom compositions are the key outputs to control.