Synthesizing alternative sequences via a P-graph-based approach in azeotropic distillation systems

The present work proposes a P-graph based approach capable of systematicall y generating all combinatorially feasible alternative sequences for both co ntinuous and batch azeotropic distillation systems when the feeds, products , and operating units and their concomitant intermediate materials are know n. To facilitate synthesis, a highly effective method has been established to identify processing or operating units necessary for constructing azeotr opic-distillation systems by means of first principles and logical sequenci ng of such units. The materials represented in the space of the residue cur ve map are partitioned into lumped materials bounded by thermodynamic bound aries and pinches, e.g. distillation boundaries and liquid-liquid phase equ ilibrium envelope. Subsequently, the operating units are identified on the basis of these lumped materials. The proposed approach automatically discar ds the operating units and intermediates whose inclusion will lead to infea sible sequences. The efficacy of the approach is illustrated with a realist ic example. (C) 2000 Elsevier Science Ltd. All rights reserved.