Design Of Extractive Distillation Process Research Articles

Insights on the sustainable design of extractive distillation processes for separating the isopropanol/1,4-dioxane/water mixture considering economic and entropy generation indicators

Several extractive distillation processes with DMSO as extractant are proposed to separate isopropanol/1,4-dioxane/water azeotropic mixtures in this study, including direct extractive distillation (DED), indirect extractive distillation (IED), DED process with dividing wall column (DED-DWC), IED process with dividing wall column (IED-DWC) and IED process with heat integration (IED-HI). The multi-objective genetic algorithm employs total annual cost (TAC) and entropy generation as the objective functions to optimize processes. The TOPSIS entropy weight method has invested to identify the appropriate optimal solution. DWC and heat integration technologies are proposed to decrease the irreversibility of DED and IED processes. The results showed that the best option to perform the separation of the mixture was the IED-HI process. It is gratifying to note that the TAC and entropy generation of IED-HI process is decreased by 15.36 % and 28.84 %, respectively, in relation to the IED process.

Effect of operating pressure on design of extractive distillation process separating DMC-MeOH azeotropic mixture

Although dimethyl carbonate is defined as a green chemical, separation of dimethyl carbonate-methanol azeotropic mixture is an important issue for many dimethyl carbonate production processes. Extractive distillation process is considered as a favorable method for separating this mixture, but the recovery of entrainer still results in a significant loss of capital and operating costs. On the other hand, operating pressure is an important design variable for distillation columns since it has an important impact on column temperature and phase equilibrium. In this work, the effect of operating pressure is investigated for an extractive distillation process separating the dimethyl carbonate-methanol mixture using methyl isobutyl ketone as entrainer. It is observed that the increase in the operating pressure of extractive distillation column significantly decreases the amount of required entrainer flowrate. As the result, a process with an extractive distillation column operating at 10 bar reduces total annual cost and carbon dioxide emissions by 34.1% and 29.8%, respectively compared to the conventional process with an extractive distillation column operating at atmospheric pressure.

Design of extractive distillation process with mixed entrainer

AbstractThe separation of two systems containing minimum boiling azeotropes (acetone-methanol and tetrahydrofuran (THF)-water) was performed using extractive distillation with a heavy boiling mixed entrainer consisting of two compounds. The entrainer constituents did not form new azeotropes with each other and with the components of the original mixture. An analysis of the mixed entrainer influence on the vapor-liquid equilibrium (VLE) and relative volatility provides an understanding of the cases in which the separation by extractive distillation (ED) in the presence of the mixed entrainer revealed energy benefits over their individual constituents. New results for application of the mixed entrainer monoethanolamine (MEA)-ethylene glycol (EG) and dimethylsulphoxide (DMSO)-glycerol for the separation of THF-water and acetone-methanol, respectively, are presented for the first time. The individual selective agents were chosen from the efficient entrainers discussed in the literature. The calculations were performed using the platform Aspen Plus 7.3. Different extractive distillation flowsheets are provided for the zeotropic mixed agents, viz. with two or three columns. For the ED of the binary mixtures investigated, the structures of the different separation schemes, the operating parameters of the columns, and the energy consumptions are presented and compared. The application of the mixed entrainer MEA-EG fed into the ED column with pre-mixing can be recommended, providing up to 1.7 % of energy saving for acetone-methanol separation. In the case of THF-water, the mixed entrainer DMSO-glycerol provides 0.8 % of energy saving. The separate inputs of the individual constituents of the mixed entrainer led to a significant increase in the energy consumptions of the flowsheet because of the third regeneration column, hence this flowsheet cannot be recommended for use in the separation of both mixtures.

Entrainer selection for separating tetrahydrofuran/water azeotropic mixture by extractive distillation

The mixture of tetrahydrofuran (THF) and water is a minimum boiling azeotrope due to the strong hydrogen bond effect. Some entrainers with different molecular structures which can potentially disrupt hydrogen bonds have been used to improve the relative volatility of THF–water system. After cautiously screening, we find that dimethyl sulfoxide (DMSO) as a hydrogen bond breaker is more effective to break the azeotrope than 1, 2-propanediol proposed by Songlin Xu etc. To validate our viewpoint, the vapor–liquid equilibrium (VLE) data of the two ternary systems: THF (1)+water (2)+1, 2-propanediol (3) and THF (1)+water (2)+DMSO (3) were measured at 101.32kPa. And these data are also valuable for the design of extractive distillation process. The nonrandom two-liquid (NRTL) model was applied to correlate the binary and ternary VLE data.

Conceptual process design of extractive distillation processes for ethylbenzene/styrene separation

In the current styrene production process the distillation of the close-boiling ethylbenzene/styrene mixture to obtain an ethylbenzene impurity level of 100ppm in styrene accounts for 75–80% of the energy requirements. The future target is to reach a level of 1–10ppm, which will increase the energy requirements for the distillation even further. Extractive distillation is a well-known technology to separate close-boiling mixtures up to high purities. The objective of this study was to investigate whether extractive distillation using ionic liquids (ILs) is a promising alternative to obtain high purity styrene. Three ILs were studied: [3-mebupy][B(CN)4], [4-mebupy][BF4], and [EMIM][SCN]. Extractive distillation with sulfolane and the current conventional distillation process were used as benchmark processes. The IL [4-mebupy][BF4] is expected to outperform the other two ILs with up to 11.5% lower energy requirements. The operational expenditures of the [4-mebupy][BF4] process are found to be 43.2% lower than the current distillation process and 5% lower than extractive distillation with sulfolane extractive distillations. However, the capital expenditures for the sulfolane process will be about 23% lower than those for the [4-mebupy][BF4] process. Finally, the conclusion can be drawn from the total annual costs that all studied extractive distillation processes outperform the current distillation process to obtain high purity styrene, but that the ILs evaluated will not perform better than sulfolane.