Computers & Chemical Engineering, Vol.19, No.S, 525-530, 1995
Controllability and Operability of Azeotropic Heterogeneous Distillation Systems
Controllability, observability and flexibility are relevant operational indexes for the identification of a complete and effective control structure for a chemical plant. In this work, we present and discuss the application of such a structural analysis to an azeotropic heterogeneous system, which is a very sensitive plant. No new theoretical aspects have been introduced, but the main feature of this paper is the extension of linear procedures to a strongly non-ideal systems. All the results have been carried out on the basis of a rigorous dynamic model, which allows to identify and verify the operational points of different control schemes. Two operating designs have also been compared, showing that an "upper tie line" (UTL) design, close to the heterogeneous boundary, is generally more flexible than a "lower tie line" (LTL) design, close to the ternary azeotrope. Moreover, the results here reported show how a suitable feedforward control structure allows to increase the operability of the analyzed design configurations with a general improvement of the corresponding operational flexibility.