Pressure Swing-Based Reactive Distillation and Dividing Wall Column for Improving Manufacture of Propylene Glycol Monomethyl Ether Acetate

Propylene glycol monomethyl ether acetate (PGMEA) is a commonly used solvent in the rapidly developing semiconductor industry. Ultra-high purity PGMEA is required for this ultra-precision industry and to satisfy the current strict waste management regulations. The traditional PGMEA production process consumes considerable energy and has a high production cost. In this study, a novel heat integrated and intensified design, which applies a dividing wall column, reactive distillation, and pressure swing techniques, was proposed for improving the energy efficiency and reducing the cost of PGMEA production. Heat integration was applied to maximize the heat recovery of the process. All processes were simulated using the commercial simulator Aspen Plus V11. The economic and environmental parameters of the process alternative were assessed for a fair comparison with the conventional process. The results showed that heat integration of the optimal pressure swing-based reactive distillation and dividing wall column processes could reduce the energy requirement and TAC by 29.5%, and 20.8%, respectively, compared to that of the optimal conventional process. The improved design provides a strong basis for achieving more sustainable PGMEA production.

Dividing-Wall Column Design: Analysis of Methodologies Tailored to Process Simulators

Dividing-wall columns (DWCs) are intensified processes that have attracted industrial and academic attention due to the reduction in operating and installation costs compared to traditional distillation systems. Several methodologies are available for the design of DWCs. Most of them consist of three parts: an analysis of operating variables; an analysis of the structural design (topology); and an optimization of the resulting preliminary design. This paper aims to study three widely used design methodologies reported in the literature for DWCs, i.e., Triantafyllou and Smith (T&S), minimum vapor (Vmin), and Sotudeh and Shahraki (S&S) methods, along with their implementation on process simulators. A proposed modification to the S&S methodology is also presented. A comparison of the methods is carried out and rated against designs with minimum total annual costs. The analysis considers the effect of different structural design variables to initialize the design procedure with each methodology. Five case studies involving mixtures with different ease of separation index were evaluated. The results show that the most efficient techniques were obtained with a modified Sotudeh and Shahraki’s methodology. It was also found that the T&S approach stands out from the other methods, as it provided excellent initial designs for the case studies tested in this work.

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

Impact of Various Feed Properties on the Performance of a Control System for a Multiple Dividing Wall Column Pilot Plant

Despite the attractive savings potential of multiple Dividing Wall Columns (mDWC), there are no reports in the open literature of an existing application so far. In this perspective, the control of mDWCs has been a rather little-investigated field. Pilot plants are a necessary step needed to further expand the application window of this sustainable distillation technology. This contribution aimed to show that mDWCs are sufficiently flexible, providing stable operation, even with suboptimal control structures arising from design limitations imposed by equipment. For this purpose, the pilot column design was assessed using dynamic simulation to evaluate its operability in case of different disturbances as well as different feed mixtures. The results showed that, in all cases, the column could be stabilized and product purities maintained. This suggests that even complex configurations such as mDWCs offer sufficient amount of flexibility to allow for the application of one design in different services.