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<p>Enhancing the controllability and exergy efficiency of distillation is essential for improving overall process sustainability. This study provides an integrated assessment of controllability and exergy efficiency in extractive and pressure swing distillation for azeotropic separation. Controllability is evaluated using the Morari Resiliency Index, condition number, and relative gain array number, combined into an aggregate desirability function. System responses to feed flow and composition disturbances are analyzed to determine optimal control pairings. Exergy efficiency is assessed by quantifying irreversibilities and energy utilization across process units. Two representative azeotropes are considered: the minimum-boiling tetrahydrofuran (THF)/water and the maximum-boiling acetone/chloroform mixtures, each under non-heat-integrated (NHI) and fully heat-integrated (FHI) configurations. Results show that for the THF/water system, FHI reduces energy demand in extractive distillation (ED) by 33.2% and in pressure-swing distillation (PSD) by 32.3%, while increasing exergy efficiency by 2.6% and 6.7%, respectively. Similarly, CO₂ emissions are lowered by up to 36.4% in ED and 29.3% in PSD. However, in acetone/chloroform separation, FHI enhances performance only in PSD, reducing energy use by 37.6% and emissions by 42.5%. In contrast, FHI in ED increases energy consumption by 17.7% and worsens exergy efficiency (dropping from 3.5% to 1.2%) and emissions (rising by 17.6%). Additionally, aggregated controllability desirability worsens under FHI for all cases. While heat integration is generally expected to substantially improve sustainability, its adverse effects on the extractive distillation of complex mixtures like acetone/chloroform highlight the need for alternative integration strategies or technologies.</p> Graphical abstract <p></p>

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Integrated Assessment of Controllability and Exergy Efficiency in Extractive and Pressure Swing Distillation

  • 期刊论文

  • 发表日期：

    2025年8月7日

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  • Jonathan Wavomba Mtogo,
  • Gladys Wanyaga Mugo,
  • Agnes Szanyi,
  • Péter Mizsey

摘要

Enhancing the controllability and exergy efficiency of distillation is essential for improving overall process sustainability. This study provides an integrated assessment of controllability and exergy efficiency in extractive and pressure swing distillation for azeotropic separation. Controllability is evaluated using the Morari Resiliency Index, condition number, and relative gain array number, combined into an aggregate desirability function. System responses to feed flow and composition disturbances are analyzed to determine optimal control pairings. Exergy efficiency is assessed by quantifying irreversibilities and energy utilization across process units. Two representative azeotropes are considered: the minimum-boiling tetrahydrofuran (THF)/water and the maximum-boiling acetone/chloroform mixtures, each under non-heat-integrated (NHI) and fully heat-integrated (FHI) configurations. Results show that for the THF/water system, FHI reduces energy demand in extractive distillation (ED) by 33.2% and in pressure-swing distillation (PSD) by 32.3%, while increasing exergy efficiency by 2.6% and 6.7%, respectively. Similarly, CO₂ emissions are lowered by up to 36.4% in ED and 29.3% in PSD. However, in acetone/chloroform separation, FHI enhances performance only in PSD, reducing energy use by 37.6% and emissions by 42.5%. In contrast, FHI in ED increases energy consumption by 17.7% and worsens exergy efficiency (dropping from 3.5% to 1.2%) and emissions (rising by 17.6%). Additionally, aggregated controllability desirability worsens under FHI for all cases. While heat integration is generally expected to substantially improve sustainability, its adverse effects on the extractive distillation of complex mixtures like acetone/chloroform highlight the need for alternative integration strategies or technologies.

Graphical abstract