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This perspective paper discusses the alignment between steady‐state design and control (dynamic) simulation in the context of flexibility analysis for distillation systems. Operational variations, such as fluctuations in feed composition or flowrate, can stem from external factors like raw material quality or temperature variations. These disturbances need to be mitigated to ensure optimal industrial performance. Traditionally, these process uncertainties are usually considered in a sequential manner, where the steady‐state flowsheet is established first, and control performance is analyzed afterwards. However, recent studies have started integrating flexibility index into the design phase to account for process uncertainties. While this integration has improved design strategies, aligning steady‐state and dynamic control simulations for comprehensive flexibility analysis remains underexplored. In this paper, we wish to share new perspectives and insights we have observed by analyzing the existing literature. We highlight some points not immediately apparent in our previous studies, hoping these insights will serve as guidelines for future research in this direction. We believe that validating results between steady‐state and control simulations is a long‐term endeavor that cannot be conclusively addressed soon. However, we hope this paper will be valuable to future researchers, contributing to advancing this field and reaching those who will appreciate and build upon these insights. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

As a new gasoline additive, methyl tertiary amyl ether (TAME) can improve the antiknock performance and quality of gasoline. This study uses an energy-saving process for separating TAME/methanol (MeOH)/H 2 O by pressure-swing extractive distillation with different entrainers based on multi-objective optimization and 4E analysis. The 1entrainers are screened by the difference in relative volatility of components under different entrainer conditions, and the electrostatic potential of the molecular surface of the system and entrainers are analyzed. Multi-objective optimization of the pressure swing extractive distillation process with 5 different entrainers is carried out based on the generation non-dominated sorting genetic algorithm (NSGA-Ⅱ) optimization scheme, and the Pareto frontier is optimized by the minimum distance method. The results indicate that the extraction schemes of 1,3-propanediol (PDO) and dimethyl sulfoxide (DMSO) have excellent economic and environmental benefits through comprehensive analysis. As an effective means of process intensification, the application of heat pump technology can further reduce process costs and environmental pollution. The coefficient of heating performance (COP) is used to find the most suitable pairing route for heat pump-assisted processes, achieving the goal of reducing gas emissions and energy use. Then, different processes are evaluated in terms of economy, energy consumption, environment, and exergy loss. The results show that the process intensification scheme based on heat pump technology can effectively improve the economic and environmental benefits of the process, reducing the annual total cost (TAC) and gas emissions by 9.19% and 23.55%, respectively. This study provides the selection and reference for azeotrope separation of TAME and recycling of wastewater. [ABSTRACT FROM AUTHOR]

• Rational functions were trained as VLE surrogate models with thermodynamic consistency. • Superstructure-based extractive distillation process synthesis was solved within a few seconds. • A multi-level solvent screening was performed for ethylbenzene/styrene separation. • C 2 H 2 Br 4 was found to reduce cost by 27.9 % compared to the benchmark sulfolane. When designing extractive distillation processes, using selectivity and capacity at infinite dilution alone is hard to identify the real optimal solvent with minimal process cost. To overcome this problem, a new process-driven solvent screening approach is developed. As simple and reliable surrogate models, rational functions (algebraic fractions such that the numerator and the denominator are polynomials) and multivariate polynomials (a subset of rational functions) are trained to interpolate vapor–liquid equilibria with thermodynamic consistency. The surrogate models can directly be embedded into superstructure-based extractive distillation process design to obtain optimal solutions within a few seconds. This enables to evaluate the real process performance of numerous solvents efficiently. Incorporating the accelerated process design strategy, a multi-level solvent screening framework is proposed and exemplified for the separation of a close-boiling mixture ethylbenzene/styrene. The solvent C 2 H 2 Br 4 ultimately enables a cost reduction of 27.9 % compared to the industrially used benchmark solvent sulfolane. [ABSTRACT FROM AUTHOR]

We integrate equilibrium and rate-based models to formulate a hybrid optimization scheme for designing an ionic liquid-based extractive distillation process for mixed-refrigerant separation. The equilibrium model assumes vapor–liquid equilibrium at each stage but challenges arise with low-volatility, high-viscosity solvents, which drive the system away from equilibrium. The rate-based approach considers mass and heat transfer rates, giving more accurate representation. We compare the two models for separating R-410A, an azeotropic mixture of R-32 and R-125, using [EMIM][SCN] ionic liquid as entrainer. Analyzing over 4300 simulations with various dimensionality reduction and topological analysis techniques, we find that predictions from the two models exhibit similar trends, but the overestimation in equilibrium-based purities sometimes leads to infeasible process designs. The proposed optimization algorithm thus combines the strengths of the two models to locate feasible and optimal designs. • Comparison of equilibrium and rate-based models for solvent-based gas separation. • Model similarity analysis using PCA, distance metrics, and Euler Characteristic. • Equilibrium models overestimate model predictions but capture trends of rate-based models. • Hybrid optimization using both models with new constraint refinement and update rules. [ABSTRACT FROM AUTHOR]

• Novel and energy-saving heat pump assisted extractive distillation processes are designed to separate EA-HEP azeotrope. • The σ-profile analyzes the intermolecular interaction at the molecular level. • The sequential iteration method is used to optimize the processes and get the minimum TAC. • The TAC, energy consumption and CO 2 emission of HPED-WITH process decreases by 16.78 %, 28.14 % and 41.83 %, respectively. In the pharmaceutical and fine chemical industries, azeotropic mixtures like ethyl acetate (EA) and n-hexane (HEP) are produced. Effective separation and purification are essential for recycling resources and protecting the environment. This study investigates the design and optimization of energy-efficient extractive distillation processes for separating EA and HEP. N-methylpyrrolidone (NMP) and p-xylene (PX) were selected as extractants. Their effectiveness was validated through vapor liquid equilibrium (VLE) studies, and their interaction mechanisms were clarified using σ-profile analysis. Extractive distillation processes using NMP and PX as extractants (ED-NMP and ED-PX) were developed and evaluated based on total annual cost (TAC), energy consumption, and CO 2 emissions. The results showed that the ED-PX process outperformed the ED-NMP process. Additionally, integrating a heat pump with an overhead steam preheater further enhanced all performance metrics, reducing TAC, energy consumption, and CO 2 emissions by 16.78 %, 28.12 %, and 41.83 %, respectively. This study provides valuable insights for the separation and purification of EA and HEP. [ABSTRACT FROM AUTHOR]

• A novel cryogenic distillation-based CO 2 capture method in LNG process is proposed. • The azeotropic characteristics of CO 2 -C 2 H 6 is utilized to avoid CO 2 freeze-out. • The proposed process can remove up to 17 % of CO 2 to less than 50 ppm. • The integrated "LNG + C 2 H 6 recovery + CO 2 removal" minimizes energy consumption. • The exergy efficiency of the system is higher than 50%. Cryogenic CO 2 capture technique is superior to other CO 2 capture methods in terms of potential environmental protection, because it uses no chemical solvent or membrane materials that need regular replacement. However, the freezing problem of CO 2 makes it difficult to achieve CO 2 capture through simple gas–liquid separation, and the existing cryogenic CO 2 capture techniques often require a specially designed separation equipment. In addition, cryogenic CO 2 capture is generally considered a method with high energy consumption due to the need for refrigeration. This study proposes a cryogenic distillation-based CO 2 capture method for natural gas with high ethane content, such as shale gas and oilfield associated gas. This method utilizes the azeotropic characteristics of CO 2 and ethane to avoid CO 2 freeze-out and the energy consumption for CO 2 capture is minimized through process integration with natural gas liquefaction and ethane recovery. The proposed system uses the propane precooled mixed refrigerant process to provide the required refrigeration, and it is simulated in Aspen HYSYS and optimized by a combined method of a genetic algorithm and sequential optimization. The results show that the proposed process can remove up to 17 mol% of CO 2 to less than 50 ppm. With extractive distillation, 99.50 % of the ethane in the feed gas is recovered with a purity of 99.50 mol%. The optimal results corresponding to the maximum allowable CO 2 content to avoid its freeze-out (with a solubility margin of 500 ppm) show that when ethane content is 2–20 mol%, the specific power consumption of the system is about 0.43 kWh/Nm3(NG) with an exergy efficiency higher than 50 %. The proposed process achieves energy-saving and efficient CO 2 capture method for natural gas with high ethane content. [ABSTRACT FROM AUTHOR]