Synthesis of heat-integrated thermally coupled nonsharp distillation using self-adaptive spherical search

Although thermally coupled distillation (TCD) exhibits strong energy efficiency, the possibility of utility cost savings remains debatable. TCD designs that do not consider vapor transport can underestimate costs, making section rearrangement crucial to find more operable configurations. This study proposes an algorithm to generate a separation matrix of basic configurations, enumerating their thermodynamically equivalent configurations using a coding method and filtering the operable configurations. Acyclic simulation and proposed section pressure distribution strategies enable optimization without altering the flowsheet. The TCD system was optimized for total annualized cost using self-adaptive spherical search. Case studies reveal that TCD saves up to 49% in heating duty compared to that of conventional sequences; however, utility costs increase by 12–133%. This study demonstrates that the flexibility of operating at different design pressures outweighs the potential savings of TCD; however, this can be compensated for by the reduced capital costs of the dividing-wall column.