Synthesis of New Distillation Systems by Simultaneous Thermal Coupling and Heat Integration

Abstract

Distillation systems with simultaneous thermal coupling and heat integration can significantly reduce both energy and capital costs compared with systems employing either thermal coupling or heat integration alone. Predefinition of all such new systems will provide a much better alternatives space in optimization when searching an optimal system for a given application. In a previous work (Rong et al. Ind. Eng. Chem. Res. 2003, 42, 4329-4339), a strategy for heat integration between heat exchangers associated with a single middle component in the thermally coupled configurations was presented, from which the heat-integrated partially coupled (HIPC) distillation systems were obtained. In this work, new strategies for simultaneous thermal coupling and heat integration have been approached, where heat integrations are performed between heat exchangers associated with both single middle components and submixtures of middle components. A large number of new heat-integrated thermally coupled (HITCs) distillation systems are synthesized. In the new HITCs, all the thermal couplings are located at the ends of columns, and all the heat integrations are implemented at the intermediate locations of the combined columns. Compared with the original thermally coupled configurations (OTCs), the new HITCs have the distinct features of (1) a reduction in the number of thermal couplings; (2) a reduction in the number of heat exchangers; and (3) a reduction in the number of columns. As a consequence, the new HITCs have the potential to further reduce energy and capital costs or to improve the operability of the OTCs. In this paper, all of the new HITCs for quaternary distillations are first generated. Then, a procedure is formulated to synthesize new HITCs for an n-component mixture. Finally, it is shown that the new HITCs produce distinct thermodynamically equivalent structures to those produced by the OTCs.