Key Takeaways & Executive Findings
- •• A novel pressure-swing-assisted ternary heterogeneous azeotropic distillation (THAD) process is proposed to synergistically combine heterogeneous azeotropic and pressure-swing distillation, achieving significant energy savings. • The integration of dividing-wall column and heat integration technologies further reduces energy consumption and CO2 emissions compared to published THAD processes. • Genetic algorithm optimization is employed to handle the complex design variables, demonstrating superior energy efficiency and environmental performance. • The proposed processes avoid aqueous phase remixing and reduce recycle stream flowrates, enhancing overall process sustainability.
Abstract
A huge amount of energy is always consumed to separate the ternary azeotropic mixtures by distillations. The heterogeneous azeotropic distillation and the pressure-swing distillation are two kinds of effective technologies to separate heterogeneous azeotropes without entrainer addition. To give better play to the synergistic energy-saving effect of these two processes, a novel pressure-swing-assisted ternary heterogeneous azeotropic distillation (THAD) process is proposed firstly. In this process, the ternary heterogeneous azeotrope is decanted into two liquid phases before being refluxed into the azeotropic distillation column to avoid the aqueous phase remixing, and three columns' pressures are modified to decrease the flowrates of the recycle streams. Then the dividing wall column and heat integration technologies are introduced to further reduce its energy consumption, and the pressure-swing-assisted ternary heterogeneous azeotropic dividing-wall column and its heat integration structure are achieved. A genetic algorithm procedure is used to optimize the proposed processes. The design results show that the proposed processes have higher energy efficiencies and lower CO2 emissions than the published THAD process.
1. Introduction
Distillation is the most commonly used separation technology to split a mixture into its pure components in the chemical industry [1], but the frequent presences of multi-azeotropic mixtures limit the regular distillation column usages seriously. The residue curve maps (RCMs) of the most complex ternary azeotropic mixtures contain three binary azeotropes, one ternary heterogeneous azeotrope, and three distillation regions. Some high-value organic components can be recovered from the wastewater by separating these kinds of mixtures. Since such complex mixtures cannot be separated by the regular distillation, therefore, the research on the effective distillation processes to separate these mixtures is of great importance for the high-quality and green development of the chemical industry.
In recent years, more and more studies focused on the separation of the ternary azeotropic mixtures by some novel distillation processes. Shen, Wang, Ye and Luyben et al. [2e5] studied the ternary pressure-swing distillation (TPSD) to separate the ternary mixtures with pressure-sensitive azeotropic compositions. Shen, Wang, and Chien et al. [6e14] studied the design, control, and agent-choice problems for the ternary extractive distillation.
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Lianjie Wu, Kun Lu, Qirui Li, Lianghua Xu, Yiqing Luo, Xigang Yuan (2023). Energy-saving design and optimization of pressure-swing-assisted ternary heterogenous azeotropic distillations. Chinese Journal of Chemical Engineering. https://doi.org/10.1016/j_cjche_144878052
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Frequently Asked Questions
What is the main contribution of this paper?
The paper proposes a novel pressure-swing-assisted ternary heterogeneous azeotropic distillation (THAD) process that synergistically combines heterogeneous azeotropic distillation and pressure-swing distillation, and further integrates dividing-wall column and heat integration technologies to achieve significant energy savings and lower CO2 emissions compared to published THAD processes.
How does the proposed process achieve energy savings?
The process decants the ternary heterogeneous azeotrope into two liquid phases before refluxing to avoid aqueous phase remixing, modifies column pressures to reduce recycle stream flowrates, and employs dividing-wall column and heat integration to further reduce energy consumption.
What optimization method is used in this study?
A genetic algorithm procedure is used to optimize the proposed processes, effectively handling the large number of design variables and achieving superior energy efficiency.
What are the environmental benefits of the proposed processes?
The proposed processes have higher energy efficiencies and lower CO2 emissions than the published THAD process, contributing to greener chemical production.
What is the significance of this research for the chemical industry?
This research provides an effective and energy-saving distillation process for separating complex ternary azeotropic mixtures, which is crucial for high-quality and green development in the chemical industry.
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