Petlyuk Columns

Columns with completely thermal coupling flows were patented in different modifications by a number of authors sequence with prefractionator (Brugma, 1942 Fig. 6.12d) column with dividing wall (Wright, 1949 Fig. 6.12f) and column with dividing wall for separation of four-component mixtures (Cahn et al., 1962). Later, these columns were independently rediscovered (Petlyuk, Platonov, & Slavinskii, 1965 Platonov, Petlyuk, & Zhvanetskiy, 1970) on the basis of theoretical analysis of...

Heteroazeotropic Distillation

Figure 6.16a shows separate usage of distillation column and decanter, when top product of the column, close in composition to ternary heteroazeotrope-unstable node, is directed after cooling to decanter. The example is separation of the mixture ethanol(2)-water(3) using toluene(1) as entrainer (Pilhofer, 1983). At such sequence, the structure and evolution of section trajectory bundles remain the same as at separation of homogeneous mixtures, when one of the products is azeotrope -unstable...

Product Composition Regions for Ideal Four Component Mixtures

Let's examine a set of product points at R to and its subset at R to and N to for a four-component ideal mixture Fig. 3.4 . Some point of the bottom product belonging to the possible bottom product region at set feed composition dark shaded region to the right of point F corresponds to the top product point Figure 3.4. a Product region under infinite reflux for given xF and different number of trays and D F. Ideal four-component mixture K gt K2 gt K3 gt K4 , line 1 xD atN andxF1 lt D F lt xF1...

NComponent Mixture

At n gt 4, it is necessary to use special algorithms. Determining products xD and xB compositions for distillation without distributed components 1,2, k k 1, k 2, n is implemented according to formulas xDi zFi zFi i 1, 2, k 3.5 zFi i k 1, k 2, n 3.6 Nodes N and NB are defined by means of calculation of line of conjugated liquid-vapor tie-lines from point xD or line of conjugated vapor-liquid tie-lines from point xB. In Fig. 3.12, line of conjugated vapor-liquid tie-lines from point xB 3 is...

Product Composition Regions for Azeotropic Three Component Mixtures

Let's examine three-component azeotropic mixtures with one binary azeotrope and with two regions of distillation at infinite reflux RegTO Fig. 3.6a . There is some region triangle to the right of separatrix where two points of the bottom product corresponding to one top product point exist. This fact is explained by the S-shape of c-lines in this region Fig. 3.6b, points xB 2 and xB 3 . The main difference between the azeotropic mixtures and also nonideal zeo-tropic mixtures and the ideal ones...

Geometric Interpretation of Multicomponent Mixture Distillation Splits

Geometric interpretation of distillation process of binary mixtures has been decisive in understanding the subject and the basic principles of the distillation units design development. Geometric interpretation of multicomponent mixtures distillation is also important for deep insight into the pattern of the multicomponent mixture distillation and better understanding of the methods of design of the units used for the separation of these mixtures. As Chapter 1 introduced, the composition of a...

Underwood System of Equations

The Underwood system of equations can be obtained from the conditions of componentwise material balance and of phase equilibrium in the cross-section of constant concentration zones of each section. For example, the following expression can be obtained from the equation of componentwise material balance at the contour, embracing the part of top section from the cross-section in the zone of constant concentration to the output of top product, taking into consideration the conditions of phase...

Necessary Condition of Mixture Separability for the Set Split

Let's formulate now the main necessary condition of mixtures separability for the set split it is necessary that at the boundary element to which the top product Figure 5.10. Component-order regions Regj, trajectory tear-off regions RegJ 2 and Regs'2', and sharp split regions Reg 'h and Reg 'h s hatched for bottom section and shaded for top section, hatched and shaded for two section for the acetone 1 -chloroform 2 -methanol 3 mixture for splits a 1,3 1,2 RegJ 3 '2 and RegJ 3 2 and b 2,3 1,2...

Separation of Azeotropic Mixtures in Sequence of Columns with Recycles at R and N

Azeotropic mixtures can almost never be separated completely into pure components in the sequence of columns without recycles at R and N to. The set of products of such a system of columns almost always contains not only pure components, but also azeotropes pseudocomponents . Mixtures, for which concentration simplex contains only one distillation region, are an exception. For three-component azeotropic mixtures, the only phase diagrams of such type are the diagram shown at Fig. 3.10b and...

Diagrams of Extractive Reversible Distillation for Three Component Mixtures

Condition in Tear-Off Points of the Extractive Reversible Distillation Trajectories Let's examine a column of sharp reversible distillation with two feedings Fig. 4.18a for separation of a three-component mixture Petlyuk amp Danilov, 1999 . For an intermediate section of such a column, Eq. 4.6 is as follows F2, upper feeding Vyt Lxi DyDi - F2 zfi, Let's designate d DyDi - F2zf2j d Yndi For the intermediate section, point x'Di plays the same role as the product point xDi for the top...

Phase Equilibrium of Binary Mixtures

An equilibrium between liquid and vapor is usually described as follows where yi and xi are equilibrium compositions of vapor and liquid, respectively, and Ki is the liquid-vapor phase equilibrium coefficient. To understand the mutual behavior of the components depending on the degree of the mixture's nonideality caused by the difference in the components' molecular properties, it is better to use graphs y1 - x1, T - x1, T - y1, K1 - x1, and K2 - x1 Fig. 1.2 . In Fig. 1.2, the degree of...

Azeotropic Mixtures

This result also remains valid for azeotropic mixtures. A necessary condition for exhausting of the some component in the intermediate extractive section at reversible distillation consists of the fact that the whole trajectory of intermediate extractive section should be located in the region where this component is intermediate in phase equilibrium coefficient in the region of reversible distillation of the intermediate section Regmv e . The segment of the side containing only the component...

Feasible Splits at R and N

When dealing with practical tasks, the designer of separation flowsheet should have on hand the set of feasible splits in the first column. Of course, this set of splits will hardly allow the separation of the mixture in the system of columns into pure components without the use of recycles or special methods. But frequently it is sufficient to separate only some product components. Sometimes it is reasonable to separate the mixture into several fractions that can be the subject of separation...

Geometric Interpretation of Binary Distillation Reflux and the Number of Trays

Binary Distillation Pinch

Geometric interpretation is extremely important for the understanding of distillation process. In this relation, binary distillation gives us particularly large possibilities. Only for binary distillation are we able to show in a flat diagram the composition of both liquid and vapor curves y1 - x1 . This gives us an opportunity to understand easily some general regularities of the distillation the dependence of the required number of trays upon the reflux ratio for a preset separation preset...

Diagrams of Three Component Mixture Reversible Distillation

Locations of trajectories bundles Regrev, of node points of these bundles Nrev, and of possible product segments RegD and Reg can be shown in diagrams of three-component azeotropic mixtures sharp reversible distillation for various types of such mixtures Fig. 4.11 . Along with the diagrams of open evaporation see Chapter 3 , these diagrams contain a great deal of information necessary to design separation units. The location of trajectory bundles and possible product composition segments at...

Method of Product Simplex for Distillation Subregions m n

Let's return to the notion of distillation subregion Regiub Regiub e Reg . It is a polygon, a polyhedron, or a hyperpolyhedron, the vertexes components and azeotropes of one bonds chain connecting nodes of distillation region Reg and including all the components of a mixture. The types of boundary elements of distillation subregion are the following 1 parts of boundary elements of concentration simplex coincident with boundary elements of distillation region Reg o d 2 boundary elements of...

Is Process Opposite to Distillation Process Possible

If there is a reversible distillation process, then there should be also an opposite process, which may be called a process of the distilled flow mixing. Figure 2.15b shows a McCabe-Thiele diagram with the operation lines of the opposite process of distillation, and Fig. 2.15a illustrates a scheme of this process. In the opposite process, a light component is introduced into the column bottom, a heavy component is introduced into the column overhead, and a mixture is removed from the column...

Separation of Azeotropic Mixtures by Distillation Under Two Pressures or Heteroazeotropic and Extractive Distillation

On many occasions, general geometric theory of distillation allows development of flowsheets of multicomponent azeotropic mixture separation without using such special methods as distillation under two pressures or heteroazeotropic and extractive distillation with entrainers i.e., with additional components injected into the unit . In some other cases, these methods have to be used. For example, if a binary mixture contains an azeotrope whose composition is highly dependent on pressure, it is...

Phase Diagrams of Three Component Mixtures

Three-component mixtures represent the simplest type of multicomponent mixtures. The majority of multicomponent mixture peculiarities become apparent in three-component mixtures. This is why the three-component mixtures are best studied. Liquid-vapor equilibrium in the concentration triangle C3 is represented by a vector connecting a point of liquid composition with a point of equilibrium vapor composition x y. This vector is called a liquid-vapor tie-line. The opposite vector y x vapor-liquid...

Trajectory Bundles Under Infinite Reflux Distillation Diagrams

In the case of infinite reflux when R Eq. 2.5 will be as follows Thormann, 1928 77 The distillation process under infinite reflux is described by Eqs. 2.3 and 2.6 and is illustrated in the composition space by the trajectory being the interconnected tie-lines the end of one tie-line serves as a beginning of another tie-line when moving upward from the column bottom . A concentration profile xB xD under infinite reflux for an ideal mixture is illustrated in Fig. 2.3b point F of feed composition...

Liquid LiquidVapor Phase Diagrams

To separate mixtures in which components are characterized by a limited inter-solubility, not only is liquid-vapor equilibrium of great importance as it was considered throughout the previous sections , but liquid-liquid equilibrium is also important. Figure 1.12 shows a liquid-liquid-vapor phase diagram of isopropyl alcohol l -benzene 2 -water 3 mixture. Figure 1.12 shows the critical point of liquid-liquid equilibrium cr in which the compositions of two equilibrium liquid phases are...

Adiabatic Nonadiabatic and Reversible Distillation

Hitherto, we considered the columns characterized by the fact that heat was brought in only in the reboiler and removed only in the condenser. Therefore, we can call the method of heat feeding and removing the adiabatic distillation. The method is the most simple and, therefore, the most prevalent one, but thermody-namically from the standpoint of the second law of thermodynamics nonoptimum due to the high temperature of heat feeding and the low temperature of heat removing. In practice, it...