Design of Reactive Distillation Process via Rigorous Optimization and Shortcut Methods
Date Issued
2010
Date
2010
Author(s)
Cheng, Jian-Kai
Abstract
The development of reactive distillation (RD) processes has matured significantly in the last decade, especially for the progress in the feasibility analysis, design, and control. However, two questions still often come up: (1) Can a shortcut method be employed for preliminary design? (2) How can a near-optimal design be obtained efficiently for further detailed study? In this work, these two questions are addressed.
To obtain a near-optimal design, a derivative-free optimization approach, simulated annealing (SA), is employed for the optimization of the RD column design and the SA algorithm is implemented in the Visual Basic Application which interfaces with the process simulator, Aspen Plus. This method gives an equally good or better design than the optimal flowsheet obtained from the sequential design approach. More importantly, this is achieved with much more efficient computing.
To develop a shortcut method, determination of the catalyst mass is a challenging problem in the conceptual design of reactive distillation systems. We use the concept of countercurrent cascaded vapor-liquid reactors (CCRs) to develop a shortcut method for the design of binary reactive distillation columns. An analytical expression for the theoretical minimum catalyst loading can be derived as the number of CCRs approaches infinity. On the basis of this theoretical catalyst loading, we present a calculation procedure to obtain the catalyst mass and other basic process parameters without a detailed model. Three real binary systems are used to illustrate this shortcut method, and the results show that the estimated shortcut designs are similar to the optimal designs.
Furthermore, the concept of the minimum catalyst loading is extended to more complex systems, including ternary and quaternary ideal systems and non-ideal systems with azeotropes. The results show that a minimum catalyst loading exists only if three conditions are met: (1) the RD column has a one-sided reaction zone (top or bottom) and products are withdrawn from the other side, (2) One of the reactants or an azeotrope containing a reactant is the heaviest or the lightest and (3) The pinch point in the separation section of the RD column is located in the zone with positive reaction extent.
Subjects
Reactive Distillation
Shortcut Method
Optimization Method
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-D95524021-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):1bfe0a9635fbe72150a8cb8e984ec9f4