New insight into contradictory distillation sequence heuristics: exergoeconomic and environmental analysis

This research focuses on possible sequences for the distillation of quaternary mixture to assess the performance of a system, where the general design heuristics are contradictory. In cases of contradictory heuristics, the most fitting operating scenarios for referencing each heuristic have not been explored in previous publications. The main objective of this research is to identify the most environmentally friendly and thermodynamically efficient processes, as well as to gain a better understanding of the effect of the objective function on the synthesis of separation trains, through environmental, economic and exergy analyses. To address this, 855 simulations are carried out with capital costs (CAPEX) and total annual costs (TAC) evaluations and environmental impact assessment. Global warming potential (GWP), along with exergy analysis results are also presented. The results of the current study reveal that in contrast to the heuristic criteria and recommendations, it is possible that a heuristically discouraged separation train may work very well, depending on operating conditions. It was also discovered that switching from liquid to vapour feed significantly reduces the direct sequence's superiority. Moreover, it was shown from exergy analysis that selecting the most thermodynamically efficient process does not guarantee optimal solutions in terms of economic and environmental aspects.