Two-point Lyapunov Control of Binary Distillation Columns with four temperature measurements

The problem of controlling binary distillation column effluents by manipulating the reflux and vapor flow rates on the basis of four temperature measurements is addressed. The problem is motivated by the need of understanding and systematizing two-point control industrial schemes driven by four temperature measurements. On the basis of the relative degree structure of the nonlinear passivated model, a four-state linear-decentralized model with reconstructible load inputs is drawn. Then, a passivated by backstepping OF controller is built within a Lyapunov dissipation framework, yielding a linear control scheme with: (i) regulation of distillate (or bottom) composition by adjustment of reflux flow (or heat duty) on the basis of two temperature measurements in the stripping (or rectifying) section, (ii) per-section decentralized structure, (iii) a straightforward construction procedure, and (iv) conventional-like simple tuning guidelines, without the primary-secondary gain separation limitation of the standard cascade TPT controller. The proposed control design is tested with a representative example through simulations, finding a behavior which outperforms the ones of previous TP control schemes.