Ternary distillation separation

The entrainer recovery column takes the distillate stream, from the azeo-column and separates it into a bottoms stream of pure water, and a ternary distillate stream for recycle to column 2. The overall material balance line for column 3 is shown in Figure 19b. This sequence was one of two original continuous processes disclosed in 1915 (106). More recendy, it has been appHed to other azeotropic separations (38,107,108). 

Stichlmair, J., J.R. Herguijuela, Separation regions and processes of zeotropic and azeotropic ternary distillation, AIChEJ, 38,1523-1535,... 

A distillative separation task with this net feed may then be specified to simultaneously produce a pure ethanol underflow and the ternary azeotrope overhead. This is feasible because the net feed, distillate, and bottoms compositions are collinear by mass balance, and because the distillate and bottoms are on the same residue curve (since all the curves in that region originate at the ternary... 

Gorak and Vogelpohl (1985) present an experimental study of ternary distillation in a packed column. The system used was methanol(l)-2-propanol(2)-water(3) and the column was 0.1 m wide and filled with Sulzer CY packing. Use the nonequilibrium model to simulate their experiments. Investigate the sensitivity of the simulation results to the thermodynamic model parameters. Write an article in the format required by Separation Science Technology that summarizes your calculations. 

Gorak, A. and Vogelpohl, A., Experimental Study of Ternary Distillation in a Packed Column, Separ. Sci. Technol., 20, 33-61 (1985). 

Azeotropic distillation involves either an embedded azeotrope, present in the feed mixture, or a contrived azeotrope, formed by the addition of an extraneous component called an entrainer. Benzene-water may be separated into high-purity benzene and the benzene-water azeotrope this is frequently practiced to remove water from benzene when very dry benzene is needed for chemical processing. More commonly encountered are distillation separations that are enhanced through the addition of an entrainer to form an azeotrope. Perhaps the best known separation of this type is the production of anhydrous ethanol from the ethanol-water azeotrope. Here, benzene is added as the entrainer, with the result that a low-boiling ternary azeotrope is formed between benzene, ethanol, and water. This permits the higher-boiling ethanol to be taken from the bottom of the column. The distillate condenses to a heterogeneous mixture of benzene and alcohol-water phases. 

Stichlmair, J., J.R. Fair, J. L. Bravo, 1989, Separation of azeotropic mixture via enhanced distillation, Chem. Eng. Progress, 85(1), 63-69 Stichlmair, J., J. R. Herguijuela, 1992, Separation regions and processes of zeotropic and azeotropic ternary distillation, AIChEJ, 38, p. 1523-1535 Stichlmair, J. G., J. R. Fair, 1999, Distillation, Principles and Practice, Willey-VCH Strathmann, H., 1990, Membrane and Membrane Separation Processes, Ullmann s Encyclopaedia of Industrial Chemistry, vol. A16 Taylor, R., Krishna, R., 2000, Modelling reactive distillation, Chem. Eng. Sci., 52, 993-1005... 

The concept of minimum reflux is more complex in azeotropic distillation, because of the high non-ideal behaviour and distillation boundaries. For the special case of ternary distillation, the analysis may be simplified. It is useful to mention that the minimum reflux is linked with the concept of distillation pinch. This represents a zone of constant phase composition, so that the driving force becomes very small. Consequently, the number of necessary stages for separation goes to infinite. Similarly, there is a minimum reboil rate. In this respect, three classes of limiting separations may be distinguished (Stichlmair and Fair, 1999). Figures 9.36 to 9.38 present concentration profiles obtained by simulation with an ideal system benzene-toluene-ethyl-benzene. 

Emtir, M. and Etoumi, A. (2009) Enhancement of conventional distillation configurations for ternary mixtures separation. Clean Technologies and Environmental Policy, 11,123-131. 

Consider a typical design problem for ternary distillation with an LNK, an LK, and an HK. The feed flow rate, composition, and tenperature are specified, as are Lq/D, saturated liquid reflux, pressure, use of the optimum feed stage, and recoveries of the light and heavy keys in distillate and bottoms, respectively. We wish to predict the number of stages required and the separation obtained. 

Most investigations of azeotropes have dealt with binary or ternary mixtures. The binary pairs of a multicomponent mixture may separately form azeotropes, but these are submerged by die possible azeotropes involving the Aril mixture. It is sometimes possible to utilize binary pair azeotrope information in estimating Are role that a multicomponent azeotn will play in the distillation separation. As an exariqile, the ethanol-water system exhibits a minimum boiling azeotrope. At atmospheric pressure, the boiling points are... 

Sargent, R. W. H. (1998). A Functional Approach to Process Synthesis and Its Apphcation to Distillation Systems. Comput. Chem. Eng., 22,31-45. Stichlmair, J. B., Herguijuela, J. R. (1992). Separation Regions and Processes of Zeotropic and Azeotropic Ternary Distillation. AIChE J,38,1523-1535. Stichlmair, J. G., Fair, J. R. (1998). Distillation Principles and Practice. New York John Wiley. 

In the first class, azeotropic distillation, the extraneous mass-separating agent is relatively volatile and is known as an entrainer. This entrainer forms either a low-boiling binary azeotrope with one of the keys or, more often, a ternary azeotrope containing both keys. The latter kind of operation is feasible only if condensation of the overhead vapor results in two liquid phases, one of which contains the bulk of one of the key components and the other contains the bulk of the entrainer. A t3q)ical scheme is shown in Fig. 3.10. The mixture (A -I- B) is fed to the column, and relatively pure A is taken from the column bottoms. A ternary azeotrope distilled overhead is condensed and separated into two liquid layers in the decanter. One layer contains a mixture of A -I- entrainer which is returned as reflux. The other layer contains relatively pure B. If the B layer contains a significant amount of entrainer, then this layer may need to be fed to an additional column to separate and recycle the entrainer and produce pure B. 

The use of a ternary mixture in the drying of a liquid (ethyl alcohol) has been described in Section 1,5 the following is an example of its application to the drying of a solid. Laevulose (fructose) is dissolved in warm absolute ethyl alcohol, benzene is added, and the mixture is fractionated. A ternary mixture, alcohol-benzene-water, b.p. 64°, distils first, and then the binary mixture, benzene-alcohol, b.p. 68-3°. The residual, dry alcoholic solution is partially distilled and the concentrated solution is allowed to crystallise the anhydrous sugar separates. 

The overwhelming majority of all ternary mixtures that can potentially exist are represented by only 113 different residue curve maps (35). Reference 24 contains sketches of 87 of these maps. For each type of separation objective, these 113 maps can be subdivided into those that can potentially meet the objective, ie, residue curve maps where the desired pure component and/or azeotropic products He in the same distillation region, and those that carmot. Thus knowing the residue curve for the mixture to be separated is sufficient to determine if a given separation objective is feasible, but not whether the objective can be achieved economically. 

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