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

The present work proposes a P-graph based approach capable of systematically generating all combinatorially feasible alternative sequences for both continuous and batch azeotropic distillation systems when the feeds, products, and operating units and their concomitant intermediate materials are known. To facilitate synthesis, a highly effective method has been established to identify processing or operating units necessary for constructing azeotropic-distillation systems by means of first principles and logical sequencing of such units. The materials represented in the space of the residue curve map are partitioned into lumped materials bounded by thermodynamic boundaries and pinches, e.g. distillation boundaries and liquid–liquid phase equilibrium envelope. Subsequently, the operating units are identified on the basis of these lumped materials. The proposed approach automatically discards the operating units and intermediates whose inclusion will lead to infeasible sequences. The efficacy of the approach is illustrated with a realistic example.