Extraction processes ternary system

Since in an extractive distillation process based on this ternary system the extractive agent is nonvolatile and remains in the liquid phase, and since because of the similarity of the molar latent heats of nitric acid and water there is substantially constant molar liquid overflow, the mole fraction of magnesium nitrate remains almost constant throughout the process. It is appropriate to represent the equilibrium situation as a pseudo-binary system for each magnesium nitrate concentration, and Figure 7 shows vapor-liquid equilibria on a nitric acid-water basis at a series of magnesium nitrate concentrations from zero to 0.25 mole fraction in the liquid phase. 

Multicomponent systems containing four or more components become difficult to display graphically. However, process-design calculations can often be made for the extraction of the component with the lowest partition ratio K and treated as a ternary system. The components with higher K values may be extracted more thoroughly from the raffinate than the solute chosen for design. Or computer calculations can be used to reduce the tedium of multicomponent, multistage calculations. 

The use of simulation software to analyze this type of process is illustrated in Example 5, which considers a simplified ternary system for illustration. The simulation of an actual aromatics extraction process is more complex and can exhibit considerable difficulty converging on a solution however. Example 5 illustrates the basic considerations involved in carrying out the calculations. For more detailed discussion of process simulation and optimization methods, see Sei-der, Seader, and Lewin, Product and Process Design Principles Synthesis, Analysis, and Evaluation, 2d ed. (Wiley, 2004) and Turton et al.. Analysis, Synthesis, and Design of Chemical Processes, 2d ed. (Prentice-Hall, 2002). 

CO2 in n-hexadecane, and similarly for hydrocinnamaldehyde. Additionally the concentrations of all components that result in complete miscibility or in three-component two-phase regions can be obtained. Francis reported on 464 ternary systems that included compounds ranging from simple hydrocarbons, alcohols, esters, and aldehydes to much more complex substituted aromatics and heterocyclics. The breadth and importance of his contributions cannot be overestimated, yet, apparently his work was quite frequently not consulted for its relevance a number of research groups subsequently "rediscovered that certain separations were not advantageously carried out by supercritical fluid extraction relative to processing by distillation. 

When a soluble third component is added to two partially miscible liquids, we obtain a ternary system in which the third component (solute) is partitioned between the two liquid phases (solvents). The phase behavior of such systems is important in liquid-liquid extraction, a process that takes advantage of the differences in solubility to transfer a solute from one solvent into another. Since two mole fractions are required to represent composition in ternary systems, it is not possible to present temperature-composition or pressure-composition graphs in a two-dimensional plot. Instead, we map out the composition of the phases at constant pressure and temperature. This is done in triangular diagrams such... 

The prerequisite of all types of extraction processes is the existence of a large miscibility gap between raffinate and extract. The thermodynamic principles of phase equilibrium are dealt with in Chap. 2. An extensive collection of liquid-liquid equilibria is given in the Dechema Data Collection (Sorensen and Arlt 1980ff). Volume 1 contains data of miscibility gaps of binary systems. Phase equilibrium data (miscibility gaps and distribution equilibrium) of ternary and quaternary mixtures are listed in volumes 2-7. 

The thermodynamics of extraction processes are advantageously described in triangular concentration diagrams since both phases, i.e., raffinate and extract, are ternary mixtures. Mass fractions or molar fractions can be used as a measure for the composition of the phases. Here, x denotes the concentration of the raffinate and y the concentration of the extract. The symbol z stands for the overall concentration of a two-phase system. 

Lewis Pratt, in 1953, were the first to report that the observed Marangoni convection in their experimental ternary systems was beneficial to hquid-hquid extraction processes because it increased mass transfer rates. The effect of density gradients on interfacial convection was studied by several researchers including Berg Morig (1969), who investigated the interaction between buoyancy and interfacial tension driven effects in ternary systems. The combined interfacial convection was also seen to be beneficial to mass transfer processes. 

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