Heat-Integrated Pressure-Swing-Distillation Process for Separation of Tetrahydrofuran/Methanol with Different Feed Compositions

A process optimization is carried out to separate binary azeotropic mixtures of tetrahydrofuran and methanol by pressure-swing distillation according to the pressure-sensitive property of the binary system. Rigorous steady-state simulation that is based on the minimization of the total annual cost for partially and fully heat-integrated pressure-swing-distillation processes is implemented on Aspen Plus following the sequential iterative optimization procedure. The feasible sequence of high pressure and low pressure of two columns in the pressure-swing-distillation process and the suitable heat integration scheme are both determined by the feed composition

Effect of Entrainer Thermodynamic Properties on the Separation of Ternary Mixtures Containing Two Minimum Boiling Azeotropes by Extractive Distillation

Generally, the selection of an entrainer in extractive distillation depends on relative volatility, but our previous research shows that relying on relative volatility alone may not achieve the best economic and environmental benefits in the process. In this work, the effects of different entrainers on the separation process of ternary mixtures containing two minimum boiling azeotropes by extractive distillation were studied using a dichloromethane (DCM)/methanol (MeOH)/water system as an example. Taking the gas emission and total annual cost as objectives, the separation processes of eight entrainers in the DCM/MeOH/water system were optimized and compared by a multiobjective optimization method. The optimization results show that 1,3-propanediol had the best economic and environmental benefits, although its relative volatility was not the best. The limitations of screening entrainers by relying on relative volatility alone were demonstrated. To achieve optimal economic and environmental benefits, entrainer screening needs to consider the relative volatility, thermodynamic properties of the entrainers, and possible thermal integration schemes. This work provides a reference for the screening of entrainers and process design in extractive distillation processes

Mechanism Analysis and Multiobjective Optimization of Efficient and Energy-Saving Separation of Green Fuel Additives via Extractive Pressure Swing Distillation with an Ionic Liquid Mixed Entrainer

A mixed system for separation of green fuel additives containing diethyloxymethane and ethanol by extractive pressure swing distillation for ionic liquids mixed with organic solvents as an entrainer was proposed for the first time. The interaction mechanism between entrainers and the azeotrope was deeply explored via quantum chemistry and molecular dynamics methods. The optimal ionic liquid entrainer was determined as 1-buty-3-methylimidazolium acetate, and the most suitable organic solvent as the entrainer was p-diethylbenzene. The separation process of the ethanol, diethyloxymethane, and toluene system was developed. The process operation parameters were optimized through a multiobjective optimization method. In order to improve the energy utilization and separation efficiency of the process, a heat pump-assisted extractive pressure swing distillation process was proposed. Compared with the mixed entrainer extractive distillation process, the heat pump-assisted extractive pressure swing distillation process reduced TAC by 1.2% and gas emissions by 17.5%, demonstrating economic advantages and environmental protection effects. This work demonstrates the application of ionic liquid mixed solvents in systems containing green fuel additives, providing guidance for the screening and application of ionic liquid as an entrainer