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Influence of entrainer recycle for batch heteroazeotropic distillation

Laszlo Hegely, Peter Lang

《化学科学与工程前沿（英文）》 2018年第12卷第4期页码 643-659 doi: 10.1007/s11705-018-1760-5

摘要：

Dehydration of isopropanol applying batch heteroazeotropic distillation with toluene as entrainer (E) is investigated. The composition of the feed is near to that of the isopropanol (A)-water (B) azeotrope. The effects of recycling the entrainer and the off-cut are studied by dynamic simulation with a professional flow-sheet simulator. Three consecutive batches (one production cycle) is studied. Both operational modes (Mode I: decantation after distillation and Mode II: decantation during distillation) are simulated. For Mode II, calculations are performed both for Strategy A (distillate from the aqueous (E-lean) phase only) and Strategy B (partial withdrawal of the organic (E-rich phase), as well). The E-rich phase, the final column hold-up and the off-cut (Mode II only) are recycled to the next batch. The influence of the following parameters are determined: quantity of entrainer, reflux ratios of the steps. The variations caused by the recycling in the 2^nd and 3^rd batches are also shown. The best results (lowest specific energy demand and highest recovery of A) are obtained by Mode II, Strategy A. Recycling increases the recovery, and drastically diminishes the entrainer consumption. However, it makes the production slower and decreases the quantity of fresh feed that can be processed.

关键词： batch distillation heteroazeotropic distillation operational policies off-cut recycle entrainer

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Energy-efficient recovery of tetrahydrofuran and ethyl acetate by triple-column extractive distillation: entrainer

Ao Yang, Yang Su, Tao Shi, Jingzheng Ren, Weifeng Shen, Teng Zhou

《化学科学与工程前沿（英文）》 2022年第16卷第2期页码 303-315 doi: 10.1007/s11705-021-2044-z

摘要： An energy-efficient triple-column extractive distillation process is developed for recovering tetrahydrofuran and ethyl acetate from industrial effluent. The process development follows a rigorous hierarchical design procedure that involves entrainer design, thermodynamic analysis, process design and optimization, and heat integration. The computer-aided molecular design method is firstly used to find promising entrainer candidates and the best one is determined via rigorous thermodynamic analysis. Subsequently, the direct and indirect triple-column extractive distillation processes are proposed in the conceptual design step. These two extractive distillation processes are then optimized by employing an improved genetic algorithm. Finally, heat integration is performed to further reduce the process energy consumption. The results indicate that the indirect extractive distillation process with heat integration shows the highest performance in terms of the process economics.

关键词： extractive distillation solvent selection conceptual design process optimization heat integration

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Systematic screening procedure and innovative energy-saving design for ionic liquid-based extractive distillation process

《化学科学与工程前沿（英文）》 2023年第17卷第1期页码 34-45 doi: 10.1007/s11705-022-2234-3

摘要： In the traditional extractive distillation process, organic solvents are often used as entrainers. However, environmental influence and high energy-consumption are significant problems in industrial application. In this study, a systematic screening strategy and innovative energy-saving design for ionic liquid-based extractive distillation process was proposed. The innovative energy-saving design focused on the binary minimum azeotrope mixtures isopropanol and water. Miscibility, environmental impact and physical properties (e.g., melting point and viscosity) of 30 ionic liquids were investigated. 1-Ethyl-3-methyl-imidazolium dicyanamide and 1-butyl-3-methyl-imidazolium dicyanamide were selected as candidate entrainers. Feasibility analysis of these two ionic liquids was further performed via residue curve maps, isovolatility line and temperature profiles. An innovative ionic liquid-based extractive distillation process combining distillation column and stripping column was designed and optimized with the objective function of minimizing the total annualized cost. The results demonstrate that the total annualized cost was reduced by 19.9% with 1-ethyl-3-methyl-imidazolium dicyanamide as the entrainer and by 24.3% with 1-butyl-3-methyl-imidazolium dicyanamide, compared with that of dimethyl sulfoxide. The method proposed in this study is conducive to the green and sustainable development of extractive distillation process.

关键词： ionic liquid entrainer screening feasibility analysis extractive distillation