In a multicomponent distillation configuration, there are numerous sources and sinks of heat, and a potential way to reduce the heat duty requirement is to perform heat integration. Unfortunately, an algorithmic search of the optimal heat integration opportunities is intractable when the required temperatures of intermediate streams are computed via complex models. Instead, in this work, we introduce pressure-scaled pseudo relative volatility, a new metric to compare stream temperatures. We justify the use of pseudo relative volatility by proving that this variable is a monotonically increasing function of the liquid fraction in a saturated mixture stream. Using this metric, we derive a shortcut criterion to check the feasibility of various heat integration opportunities, such as thermal coupling via heat transfer (TCH). The advantage of this approach is that it circumvents the need for explicit temperatures and instead relies on composition, component relative volatilities, and pressurequantities that are readily available in shortcut models for optimization of distillation configurations. Leveraging this fact, we propose a new optimization framework that identifies feasible TCHs that we consider within the formulation while minimizing the total heat duty of a distillation configuration. We demonstrate, on a few examples, that our formulation can identify heat duty efficient configurations, some of which are multieffect configurations. Using this methodology, we discover configurations that are not only simpler than the fully thermally coupled (FTC) configuration but also have a much lower heat duty.

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Numerous configurations are available for the separation of a multicomponent mixture by distillation; each of which has different energy requirements. We classify heat integration (a valuable method of reducing energy requirements) within distillation into two categories: conventional thermal coupling with mass exchange between columns (TCM) and thermal coupling via heat transfer without mass exchange (TCH). The sharp split distillation configurations, with the lowest number of distillation sections and transfer streams, provide simple distillation configurations but are known to have heat duties that are much higher than the fully thermally coupled (FTC) or Petlyuk configuration. However, for a mixture with four or more components, FTC, having the maximum number of column sections, is a complex configuration to build and operate. Through specific examples of four and five component distillations, we present, for the first time, sharp split configurations, using only one TCH and no TCM, which have a lower heat duty than the corresponding FTC containing only TCM, without requiring substantial pressure changes in the system.

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