Robust Initialization of Rigorous Process Simulations of Multiple Dividing Wall Columns via Vmin Diagrams

Abstract

Dividing Wall Columns (DWCs) allow the separation of a ternary mixture in one column shell by applying a vertical partition wall, yielding a reduction of operational and capital costs of up to 30%. Multiple DWC (mDWC), the consequent advancement of standard DWC, makes use of more than one partitioning wall, allowing the separation of quaternary or even higher mixtures in one column shell accompanied by a further reduction of energy consumption. Since no dedicated models for these columns are available in commercial process simulators, thermodynamic consistent flowsheets have to be designed and implemented. The thermally fully coupled Petlyuk arrangement is one important example. However, the initial convergence of these substituting flowsheets is demanding, since a large number of meaningful initial guesses have to be provided. A promising method for generating these first estimates are minimum vapor (V min ) diagrams. All internal flows can be extracted from these diagrams and used for robust initialization of the simulation. The goal of this work is to present the V min method in a comprehensive way in order to initialize mDWC simulations to predict the separation of four component mixtures. Additionally, the adaptation of the diagram to configurations different than Petlyuk arrangements for mDWC is evaluated and a systematic procedure to obtain them is presented. In the end, an example of a converging simulation is given, which was obtained with the values from the V min diagram.

Design Considerations of a Simplified Multiple Dividing Wall Column Pilot Plant

“…This step was carried out based on the V min -diagram. Using V min -diagrams for energetic evaluations is described in detail elsewhere [7,14]. Compared to the energetic optimum of the 2-3-4 configuration, all investigated systems within the 2-2-4-b configuration showed a higher energy demand and therefore an energy penalty.…”

“…The estimated values were again found by the V min -method. How simulations are robustly initialized by this method can be found elsewhere [7,14]. The thermodynamic model used in the simulation was non-random-two-liquid (NRTL), since it has a very good accuracy and is recommended for alcoholic mixtures, which were solely used in the simulation [17].…”

Multiple Dividing‐Wall Columns – Current Status and Future Prospects

“…At the sharp AB split for example, the whole component A entering in the feed stream is obtained in the distillate stream and no components B and C. Minima indicate sharp splits with distributing components which can be found in both product streams as impurities. A detailed description of the adaptation can be found in [27]. Additionally, there are two infeasible regions.…”

“…As long as the adaptations do not result in a higher peak than the original maximum one, the adaptation can be performed without energy penalty. A detailed description of the adaptation can be found in [27].…”

Modeling, Simulation, and Optimization 4.0 for a Distillation Column

“…One major improvement which combines advantages in energy consumption with also a cheaper investment are dividing wall columns , . Industrial applications are today restricted to implementations with one dividing wall, but there is still interest also to further develop the concept towards columns with two dividing walls in academia e.g., , . Another idea for improving energy‐efficiency is by using an internally heat‐integrated distillation column (HIDiC), which is hard to realize and led to the development and successful industrial application of a discrete version called D‐HIDiC with more than 50 % energy reduction.…”