The Effect of Off-cut Recycle on the Multivessel Batch Distillation Column using Rigorous Dynamic Model
Systematic methods and tools for managing the complexity
Process Simulation and Optimization (T4-9P)
Keywords: Multivessel Batch Distillation; Dynamic Modeling; Off-cut Recycle, Optimisation
Increased interest in unconventional batch distillation column configurations offers new opportunities for increasing the flexibility, improved separation performance and energy efficiency of batch distillation. One configuration of particular interest to us is the multivessel batch distillation, compared to the conventional batch column, which can be operated in a closed mode (total reflux) where the products are collected in vessels along the column. This configuration is consists of a condenser vessel, (Nc-1) column sections, (Nc-2) inter- mediate vessels where Nc is the number of components and a reboiler.
The total reflux operation of the multivessel batch column was presented recently [1, 3]. The focus of these works were to determine optimal operation policies in terms of minimum time or energy consumption. The feed is distributed equally among the reboiler, vessels and reflux drum and only main-cuts were considered.
Our study will focus on using of main-cuts and off-cuts instead of main cut only, however the benefits measured as reduction in batch time to achieve a desired separation, an optimal amount with desired purity of the main-cut, and increase in productivity [2]
The feasibility of this strategy is demonstrated for a number of case studies which include several ternary and quaternary mixtures with different (feed compositions), in addition to different number of trays in each section, different amount of vessel hold-up and using off-cut in different vessel locations to attainable optimum time and purity . The mathematical model assumes (100% tray efficiency) and includes standard mass and energy balances and rigorous phase equilibrium models.
Reference
1. Furlonge, H.I., Pantelides, C.C. and Sorensen, E., AIChE J. 45 (1999), 781.
2. Luyben, W.L., IEC Res. 27 (1988), 642.
3. Skogestad, S., Wittgens, B., Litto, R. and Sorensen, E., AIChE J. 43 (1997), 971.
Presented Wednesday 19, 13:30 to 15:00, in session Process Simulation and Optimization (T4-9P).
