Structural considerations in zeotropic distillation sequences with multiple feeds

The separation of multiple feed streams with some common components using sequences of distillation columns produces a rich space of alternatives that must be considered. In this work, we present the main structural characteristics of sequences generated when we want to take advantage of the synergies of common components in multiple feed streams to reduce both, energy consumption and the total number of distillation columns. In general, the sequence of separation tasks of the whole system can be obtained from the sequences of separation tasks of each one of the feeds. However, the integration in actual columns is not so straightforward and we must consider aspects like the optimal location of feeds in multiple-feed columns; and the alternatives of integration of common sub-mixtures (when possible) in actual columns. Besides, the optimal sequence of separation tasks for each feed is not necessarily the same when all of them are considered simultaneously. We show that the minimum number of actual columns, without considering further intensification, depends on the number of components in each feed and on the possibilities of integration of common sub-mixtures, so we extend the concepts of regular and basic column sequences to deal with these new situations. The examples show the potential savings in energy and number of columns compared to maintain isolated each feed; mixing the feed streams or an incorrect integration.The authors acknowledge financial support to the “Generalitat Valenciana” under project PROMETEO 2020/064

Design and simulation of divided wall column: Experimental validation and sensitivity analysis

This article deals with design and simulation of divided wall column. Design parameters are provided to the rigorous simulation in the ProSimPlus® software. The results show that the procedure can determine parameters quickly in the case studies and can give a good initialization for rigorous simulation. Secondly, a pilot plant has been design, built and operated in our laboratory. The pilot plant will provide necessary experimental evidence to validate the previous procedure. Ternary mixture and four-component mixture of alcohols have been used in our pilot plant in steady state conditions. The results show that the composition of products, composition and temperature profile along the column are in very good agreement with simulation results. Finally, in order to determine the optimal parameters of divided wall columns, the effects of the structural parameters of the divided wall column such as the height of the wall, the vertical position of the wall and number of stages of each section are analyzed. Ternary diagram is used as an indicator both in showing what the most economical configuration is and in showing the distillation boundary

Graphical techniques for analysing and synthesising separation processes

Recently, Column Profile Maps were developed as a generalized, graphically based distillation synthesis method. Unlike several other synthesis methods, it is not specific to any configuration and therefore allows the designer to devise almost any separation before being constrained by equipment. This thesis attempts to expand the theory of Column Profile Maps. Specifically, it is shown how new, and somewhat counter intuitive, column sections may be designed by merely imposing a sharp split constraint on a particular system. This special mathematical constraint makes it possible to maneuver topological characteristics of the system in almost any imaginable direction. This could lead to new designs being sought to exploit these profile behaviors, specifically in columns that require internal column sections (complex columns). Thermally coupled columns have received considerable attention for their ability to drastically reduce operating expenditures. Here, we have extended the Column Profile Map technique to encompass a systematic procedure for the design of single and multiple side rectifying and stripping units. It is shown how one may go about designing such columns rigorously without making simplifying assumptions with regard to the phase equilibrium behaviour and/or product specifications (as classical methods such as Underwood do), with the use of a Temperature Collocation method, as well as through a shortcut technique for rapid synthesis assuming ideal phase equilibrium behavior based on Column Profile Map eigenvectors. The efficacy of the shortcut technique is demonstrated with finding the best thermally coupled column comprising of a large main column and appending side-units. Naturally, the best structure is dependent on the objective function, and simple calculations presented here allow one to choose the best structure with regard to both heat quantity and quality. Furthermore, the eigenvector method allows one to construct an Attainable Region consisting of all potential designs for even the most complex column. The Column Profile Map technique is also extended to Reactive Distillation, which allows one to graphically assess the complex interaction of phenomena. Valuable conclusions can be gleaned from this method, specifically that improving a single piece of equipment’s performance may prove detrimental to the overall system’s operation. The methods developed here allow one to understand exactly why a complex process such as reactive distillation has some of the strange characteristics often reported in literature. Furthermore, it is shown how non-ideal phase equilibrium behavior may improve the column’s operability and in fact improve the overall feasibility of the unit. Using this method, one may quickly assess desirable process chemistry, feed compositions, desirable phase equilibrium and equipment sizes. Again, an Attainable Region is presented which shows all possible modes of operation that would give rise to a predefined product specification. Finally, computational techniques are presented which allows for swift calculation of stationary points in systems ranging from constant volatility to highly non-ideal, multi azeotropic systems. The importance of quickly and accurately knowing where pinch points are located, even in negative composition space, is demonstrated by critically looking at several design methods. Notably, it is shown that the Rectification Body Method is neither a necessary nor sufficient condition for design and cannot be safely extrapolated to complex column design. With knowledge of all pinch points and using the Column Profile Map technique it is shown how one may synthesise new and counter-intuitive column sections, so much so that azeotropes can be shifted outside the physically realizable space

Conceptual design, simulation and experimental validation of divided wall column: application for non-reactive and reactive mixture

Les colonnes à cloison et la distillation réactive présentent de nombreux avantages. Si ces deux concepts sont couplés, cela conduit à un procédé intensifié appelé : colonne à cloison réactive. Ce nouveau procédé intensifié constitue le principal objet d’étude de cette thèse. Dans une première partie, une procédure de design d’une colonne à cloison basée sur le modèle FUGK a été proposée. Dans cette procédure les aspects technologiques et hydrodynamiques sont abordés. Ces paramètres de design obtenus sont ensuite utilisés pour réaliser une simulation rigoureuse et une optimisation de cette colonne en utilisant le logiciel ProSim. Afin de tester cette procédure, des mélanges idéaux et non idéaux ont été utilisés. Il a été montré que cette procédure de design aboutit rapidement aux paramètres de pré design qui permettent d’initialiser de manière satisfaisante la simulation rigoureuse. Dans un second temps, un pilote d’une hauteur de 4m a été conçu, monté et testé au laboratoire. Des résultats expérimentaux ont été obtenus qui valident la procédure sur des mélanges non réactifs en termes de profils de composition et de température ainsi que sur les compositions et les débits de sortie du procédé. Enfin, dans une dernière partie, cette procédure a été adaptée à des mélanges réactifs en combinant les approches de R. Thery et al (2005) et celle de Triantafyllou et al (1992). Ces ultimes développements ont été testés sur la production d’acétate de méthyl par estérification du méthanol par l’acide acétique à la fois d’un de vue expérimental et théorique. ABSTRACT : Divided wall column and reactive distillation have many advantages. If a divided wall column and a reactive distillation are integrated, they leads to a higher integrated process is a reactive divided wall column. However reactive divided wall column has still a new research area. First of all, the thesis proposed a procedure for design of divided wall column, which based on the FUGK model. Both technological and hydrodynamic aspects in the divided wall column are considered in the procedure. Design parameters are then provided to the rigorous simulation and optimization in the ProSimplus software. In order to test this procedure, both ideal and non-ideal ternary mixtures are chosen to be separated in a divided wall column. The results show that the procedure can determine parameters quickly in the case studies and can give a good initialization for rigorous simulation. Secondly, a pilot plant has been design, built and operated in our laboratory (LGC, Toulouse, France, 2013). The pilot plant will provide necessary experimental evidence to validate the previous procedure. Ternary mixture and four-component mixture of alcohols have been used in our pilot plant in steady state conditions. The results show that the composition of products, composition and temperature profile along the column are in very good agreement with simulation results. Finally, a conceptual design method for reactive divided wall column is presented. The pre-design method of R. Thery et al., (2005) and a modified shortcut method for reactive divided wall column that is based on the classical shortcut adapted to a non-reactive divided wall column by C. Triantafyllou and R. Smith (1992) are applied. To verify, simulation and experiment are considered. The methodology has been illustrated for the synthesis of Methyl Acetate from Methanol and Acetic Acid

The modelling and control of a 1-octene dividing wall distillation column.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.Partitioned or Dividing Wall Columns (DWC) for distillation are currently receiving a lot mor

Abstracts of PhD conference 2006

This is the collection of Abstracts of the PhD conference held in 2006