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Extractive distillation and pressure swing distillation for the separation of the azeotrope of nitric acid-water: process optimization and economic comparison
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DOI：10.1016/j.cjche.2026.03.025.png)
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Abstract
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This study systematically compares extractive distillation (ED) and pressure swing distillation (PSD) for the separation of the HNO3-H2O azeotrope, highlighting their critical roles in resource recovery and environmental protection. Breaking through the limitation of traditional fixed high-concentration H2SO4, the solvent concentration is systematically optimized for the first time. Process simulation and economic optimization revealed that under optimal conditions, ED achieved efficient separation using sulfuric acid (H2SO4) with a mass fraction of 86% as the solvent,at a solvent flow rate of 4200 kg·h−1, and a total heat duty of 2234 kW. Meanwhile,to fill the research gap of PSD for the HNO3-H2O system, a two-column scheme suitable for this system is established. In contrast, PSD exhibited a significantly higher heat duty of 6036 kW under its optimal conditions, though heat integration strategies reduced this value by 37.11% to 3796 kW. Notably, this study realizes the first direct quantitative comparison between the two optimized processes. Economic evaluation showed that the total annualized cost (TAC) of ED was only 44.3% of that of PSD, underscoring the substantial cost advantage of ED. Therefore, ED is recommended for cost-sensitive industrial applications where solvent handling is feasible, while PSD remains competitive in scenarios requiring ultra-high product purity due to its solvent-free operation. This study provides a reliable quantitative basis for the industrial selecting separation strategies and contributes to enhancing efficiency and energy savings of separation processes in the chemical industry.
Keywords:
extractive distillation
pressure swing distillation
nitric acid-water azeotrope
process optimization
economic comparison
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