Marginal price : a unifying concept for insights into distillation column sequence heuristics

Abstract: "The marginal price, the change in price of a separations task as a result of performing it in the absence of non-key components, is introduced. The marginal price can be computed using any metric that reflects process economics; vapour flowrate and total annualised cost are typical examples. The utility of the marginal price concept in quantifying and explaining a number of heuristics used for distillation column sequencing is described. As an evaluation function, marginal price is closely related to the cost function employed in the predictor-based ordered search procedure of Gomez and Seader. Its performance in controlling the search in distillation-sequence design problems is compared to that of other commonly employed heuristics."