Design and optimization of a hybrid distillation/melt crystallization process

Abstract

in Wiley InterScience (www.interscience.wiley.com).Hybrid distillation/melt crystallization processes are widely used for the separation of isomer mixtures. The design of a hybrid separation processes is not a trivial task because of several structural and operational degrees of freedom. In this article, a new three-step design approach is proposed to address the above mentioned challenges. In the first step, process alternatives are generated by heuristic rules. In the second step, the generated process alternatives are optimized with respect to their energy consumption by using shortcut methods. In the third step, the most promising alternatives are rigorously optimized with respect to their total annualized costs, whereas the resulting mixed-integer nonlinear programming (MINLP) problem is solved using a modified generalized benders decomposition (GBD) algorithm to take the nonconvexities into account. The feasibility of this design approach is demonstrated by design of a hybrid distillation/melt crystallization process for separation of a ternary isomer mixture. 2008 American Institute of Chemical Engineers AIChE J, 54: [2925][2926][2927][2928][2929][2930][2931][2932][2933][2934][2935][2936][2937][2938][2939][2940][2941][2942] 2008 Keywords: crystallization, distillation, optimization, process synthesis, simulation, process IntroductionThe combination of distillation and melt crystallization for separation of close-boiling isomer mixtures is a well-known example for a hybrid separation process. The hybrid distillaCorrespondence concerning this article should be addressed to M. B. Franke at meikbernhard.franke@bayertechnology.com. American Institute of Chemical Engineers AIChE JournalNovember 2008 Vol. 54, No. 11 2925 tion/melt crystallization process combines advantages of the distillation, which is the working horse of the chemical process industry and the melt crystallization in which very high separation factors per stage can be reached. Simultaneously, the combination of distillation and crystallization overcomes the shortcomings of the individual unit operations, i.e. high energy-consumption at small separation factors and limitation of yield by eutectics, respectively. Several hybrid processes for the separation of terphenyl, 1 xylene, 2,3 dichlorobenzene, 4,5 and diphenylmethane diisocyanate isomers 6 are reported in literature.The detailed design of a hybrid separation process is a challenging task because of many degrees of freedom (DOF) involved (see also Figure 1), which can be divided into three classes:(1) Process structure: type of unit operations included in the flowsheet, number and sequence of unit operations, and the location of recycle streams.(2) Operating point: compositions of the process streams, so-called hand-over purities, which are discussed later in this article. As a general rule, the composition of a component which is separated in the specific unit will be chosen. For example, in Figure 1, the composition of the component P at the top of the distillation column D-1 is chosen ...

Deterministic Global Optimization of Multistage Melt Crystallization Processes in Hydroformylation

“…The cost function accounts for annualized installed investment costs of the crystallizer vessel as a heat exchanger, a storage tank for each crystallization stage with the same capacity as the crystallizer and for the energy costs of the process. The dimensioning of the crystallizer is done as in Franke et al (2008) and the required cooling is calculated according to Wellinghoff and Wintermantel (1991); Franke et al (2008). Physical parameter values were taken from Beierling and Ruether (2012); Beierling et al (2014).…”

Conceptual Design of Azeotropic Distillation Processes

“…Therefore, it may also be interpreted as a hybrid separation process [62,63]. Liquid phase splitting in the decanter facilitates breaking of the azeotrope to reach high purity products.…”

MINLP Optimization of the Hybrid Separation Process Distillation/Melt Crystallization

“…Grundlage der Shortcut-Optimierung sind vereinfachte, aggregierte Modelle, wie in diesem Fall die UnderwoodGleichung und ein einstufiges Shortcut-Modell der Kristallisation, das von vollständiger Ausbeute und keinen Verunreinigungen im Kristallisat ausgeht [8,9] …”

“…Man spricht von der gemischt-ganzzahligen Optimierung oder auch Mixed Integer Nonlinear Programming (MINLP). In dieser Arbeit wird dazu ein modifizierter Generalized-Benders-Decomposition-Algorithmus verwendet [8,9]. …”