Process design and multi-objective optimization for separation of ternary mixtures with double azeotropes via integrated quasi-continuous pressure-swing batch distillation

Multiobjective Optimization and Sustainability Assessment of an Improved Wet Sulfuric Acid-Based Ionic Liquid Process for the Utilization of Hydrogen Sulfide Using a Symmetry Approach

Ionic liquids (ILs) are efficient media for the liquid-phase sulfuric acid reaction. Under mild situations, the reaction of H₂S with CH₄ in ILs happens extremely quick and virtually complete, resulting in liquid sulfuric acid (H₂SO_4(l)). 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]) ILs were formerly the most effective at capturing and converting H₂S. It can convert H₂S to H₂SO_4(l) with a proportion of up to 96%. This study aimed to develop cutting-edge techniques and assess their applicability for different acidic gas capacities and H₂S amounts by considering three sustainability metrics which are people (safety), planet (ecological), and profit. Then, to maximize profit while lowering the global warming potential (GWP), fire explosion damage index (FEDI), and toxicity damage index (TDI), a multiobjective optimization (MOO) case was performed. The trade-off between economic, environmental, and safety performance was expressed through Pareto-optimal solutions. The improved wet sulfuric acid (WSA)-based IL method was safer (lower fire and explosion damage index), ecologically friendly (lower GWP), and portable. The findings indicate that the improved WSA-based on IL gives the optimum results compared to conventional WSA processes, such as the profit of 5688$/h increased from 1896$/h, the GWP of 0.0138-ton CO₂-eq decreased from 0.0275-ton CO₂-eq, the TDI of 6.72 decreased from 13.44, and the FEDI of 6.18 decreased from 20.6, respectively. This discovery opens the door to a viable strategy for capturing and converting H₂S from an acid gas stream.

Comprehensive Analysis and Targeting of Distillation Integrated into Overall Process Considering Operating Pressure Change

Distillation is important to chemical processes but it is energy intensive, and its optimization is of great significance to energy savings and emissions reduction. Varying the operating pressures of distillation columns could assist heat integration of distillation columns into the overall process, thereby reducing energy consumption. However, influences of varying column pressures on the energy profiles of the overall process have not been systematically analyzed in previous studies. This paper presents an insightful analysis of heat integration of distillation into the overall process considering the change of operating pressure. Firstly, effects of changing the operating pressure of a distillation column on its own utility requirements and the related process streams are studied. Next, such effects are graphically represented and incorporated into the grand composite curve (GCC). The change tendencies of the GCC, pinch temperature, and total utility consumption are analyzed and presented. On this basis, rules to identify the best operating pressure that minimize the overall energy consumption are proposed. A continuous reforming unit in a petrochemical enterprise is quantitatively analyzed to verify the obtained rules. The result indicates that the hot utility of the overall process can be reduced by 758 kW when the column pressure is lowered by 260 kPa.

Enhancing the Performance of Evolutionary Algorithm by Differential Evolution for Optimizing Distillation Sequence

Optimal synthesis of distillation sequence is a complex problem in chemical processes engineering, which involves process structure optimization and operation parameters optimization. The study of the synthesis of distillation sequence is a crucial step toward improving the efficiency of chemical processes and reducing greenhouse gas emissions. This work introduced the concept of binary tree to encode the distillation sequence. The performance of the six evolutionary algorithms was evaluated by solving a 14-component distillation sequence synthesis problem. The best algorithm was used to optimize the operation parameters of a triple-column distillation process. The total annual cost and CO₂ emissions were considered as the metrics to evaluate the performance of triple-column distillation processes. As a result, NSGA-II-DE was found to be the best one of the six tested evolutionary algorithms. Then, NSGA-II-DE was applied to the distillation sequence optimization to find the best operating parameters, which led to a significant reduction in CO₂ emission and total annual costs.

Design and Control of Pressure-Swing Heat Integration Distillation for the Trichlorosilane Purification Process

Trichlorosilane (TCS) is a crucial intermediate product in the polysilicon manufacturing process, and its purification consumes a significant amount of energy. The design and control of the TCS heat integration pressure-swing distillation (HIPSD) process was investigated using Aspen Plus V8.4 and Aspen dynamics in this study. Three partial processes and one full HIPSD process were investigated by adjusting the operating conditions and rationally configuring the material flow. Compared with the conventional distillation process, the partial and full HIPSD can reduce total annual cost by 15.75 and 27.39%, respectively. The aforementioned process was controlled robustly by adding the ratio of reboiler heat duty to feed (Q _R/F) feedforward control structure and the ratio of recycle to feed (F _REC/F) control structure. In addition, the performance of the control structure was evaluated by introducing ±10% disturbances of the feed flowrate and composition. To compare the performance of the control structure, the integral squared error value is combined with the dynamic response curve. The full HIPSD scheme can resist ±10% disturbances of flow and composition with the best economic performance. This study has certain reference significance for the distillation process and control strategy design of TCS in the polysilicon manufacturing process.