Multicomponent distillation azeotropic

Open-loop behavior of multicomponent distillation may be studied by solving modifications of the multicomponent equations of Distefano [Am. Inst. Chem. Eng. J., 14, 190 (1968)] as presented in the subsection Batch Distillation. One frequent modification is to include an equation, such as the Francis weir formula, to relate liquid holdup on a tray to liquid flow rate leaving the tray. Applications to azeotropic-distillation towers are particularly interesting because, as discussed by and ihustrated in the Following example from Prokopalds and Seider... 

Design. When the vapor-liquid equilibria are known, in the form of UNIQUAC parameters for instance, the calculation of azeotropic distillation may be accomplished with any of the standard multicomponent distillation procedures. The Naphthali-... 

Design. When the vapor-liquid equilibria are known, in the form of UNIQUAC parameters for instance, the calculation of azeotropic distillation may be accomplished with any of the standard multicomponent distillation procedures. The Naphthali-Sand-holm algorithm (Fig. 13.19) and the 0-method of Holland (1981) are satisfactory. Another tray-by-tray algorithm is illustrated for azeotropic distillation by Black, Golding, and Ditsler [Adv. Chem. Ser. 

Stichlmair, J. G., J. R. Fair, 1999, Distillation, Principles and Practice, Wiley-VCH Stichlmair, J. G., J. R. Herguijuela, 1992, Separation regions and process for zeotropic and azeotropic ternary distillation, AIChEJ, 38 (10), 1523-1535 Taylor, R., Krishna, R., 1993, Multicomponent Mass Transfer, Wiley Wanshafft, O. M., J. W. Koehler, E. Blass, A. W. Westerberg, 1992, The product composition regions of single-feed azeotropic distillation columns, Ind. Eng. Chem. Res., 31(10), 2354-2362... 

After the optimum additive has been chosen the liquid-vapour equilibria of the ternary or multicomponent systems have to be determined as exactlj- as possible in extractive as well as in azeotropic distillation. For this reason Null and Palmer [76] looked for methods allowing equilibrium values to be obtained from as few experimental data as possible. 

Azeotropes are of great importance to distillation and rectification. At the azeotrope gas and liquid have the same concentration y = x) and, in turn, no driving force for interfacial mass transfer exists. Azeotropic mixtures behave in some respects like pure substances. They cannot be fractionated by simple distillation. Azeotropes can exhibit a boiling point minimum (minimum azeotropes) or a boiling point maximum (maximum azeotropes). In multicomponent mixtures saddle point azeotropes with intermediate boiling temperature can also exist. 

When a multicomponent fluid mixture is nonideal, its separation by a sequence of ordinaiy distillation columns will not be technically and/or economically feasible if relative volatiK-ties between key components drop below 1.05 and, particularly, if azeotropes are formed. For such mixtures, separation is most commonly achieved by sequences comprised of ordinary distillation columns, enhanced distillation columns, and/or liquid-liquid extraction equipment. Membrane and adsorption separations can also be incorporated into separation sequences, but their use is much less common. Enhanced distillation operations include extractive distillation, homogeneous azeotropic distillation, heterogeneous azeotropic distillation, pressure-swing distillation, and reactive distillation. These operations are considered in detail in Perry s Chemical Engineers Handbook (Perry and Green, 1997) and by Seader... 

This chapter introduces how continuous distillation columns work and serves as the lead to a series of nine chapters on distillation. The basic calculation procedures for binary distillation are developed in Chapter 4. Multicomponent distillation is introduced in Chapter 5. detailed conputer calculation procedures for these systems are developed in Chapter 6. and sinplified shortcut methods are covered in Chapter 7. More complex distillation operations such as extractive and azeotropic distillation are the subject of Chapter 8. Chapter 9 switches to batch distillation, which is commonly used for smaller systems. Detailed design procedures for both staged and packed columns are discussed in Chapter 10. Finally, Chapter 11 looks at the economics of distillation and methods to save energy (and money) in distillation systems. 

Castillo, F. G. L., Towler, G. P. (1998). Influence of Multicomponent Mass Transfer on Homogeneous Azeotropic Distillation. Chem. Eng. Sci., 53,963-76. Chien, H. H. Y. (1978). A Rigorous Method for Calculating Minimum Reflux Rates in Distillation. AIChEJ., 24,606-13. 

The readership at this level is broad. The topic of separation processes taught at all engineering schools is inextricably linked to mass transport, and students will benefit from an early introductory treatment of mass transfer combined with the basic concepts of separation theory. There is, in fact, an accelerating trend in this direction, which aims for students to address later the more complex operations, such as multicomponent and azeotropic distillation, chromatography, and the numerical procedures to simulate these and other processes. 

This is a multicomponent-rectification method similar in purpose to azeotropic distillation. To a binary mixture which is difficult or impossible to separate by ordinary means a third component, termed a solvent, is added which alters the relative volatility of the original constituents, thus permitting the separation. The added solvent is, however, of low volatility and is itself not appreciably vaporized in the fractionator. 

Solvent Recovery The largest current industrial use of pei vapo-ration is the treatment of mixed organic process streams that have become contaminated with small (10 percent) quantities of water. Pei vaporation becomes vei y attractive when dehydrating streams down to less than 1 percent water. The advantages result from the small operating costs relative to distillation and adsorption. Also, distillation is often impossible, since azeotropes commonly form in multicomponent organic/water mixtures. 

Efficient and economical performance of distillation equipment is vital to many processes. Although the art and science of distillation has been practiced for many years, studies still continue to determine the best design procedures for multicomponent, azeotropic, batch, raul-tidraw, multifeed and other types. Some shortcut procedures are adequate for many systems, yet have limitations in others in fact the same might be said even for more detailed procedures. 

Multicomponent distillations are more complicated than binary systems due primarily to the actual or potential involvement or interaction of one or more components of the multicomponent system on other components of the mixture. These interactions may be in the form of vapor-liquid equilibriums such as azeotrope formation, or chemical reaction, etc., any of which may affect the activity relations, and hence deviations from ideal relationships. For example, some systems are known to have two azeotrope combinations in the distillation column. Sometimes these, one or all, can be broken or changed in the vapor pressure relationships by addition of a third chemical or hydrocarbon. 

Azeotropic and extractive-distillation equipment may be designed using the general methods for multicomponent distillation, and detailed discussion is available elsewhere(1,42) and presented by Hoffman(50) and. Smith151 ,... 

Hoffman, E. J. Azeotropic and Extractive Distillation (Interscience Publishers, Inc., New York, 1964). Holland, C. D. Fundamentals of Multicomponent Distillation (McGraw-Hill Book Co., New York, 1981). King, C. J. Separation Processes, 2nd edn. (McGraw-Hill Book Co., New York, 1981). 

Data of Azeotropes. The choice of azeotropic entrainer for a desired separation is much more restricted than that of solvents for extractive distillation, although many azeotropic data are known. The most extensive compilation is that of Ogorodnikov, Lesteva, and Kogan (Handbook of Azeotropic Mixtures (in Russian), 1971). It contains data of 21,069 systems, of which 1274 are ternary, 60 multicomponent, and the rest binary. Another compilation Handbook of Chemistry and Physics, 60th ed., CRC Press, Boca Raton, FL, 1979) has data of 685 binary and 119 ternary azeotropes. Shorter lists with grouping according to the major substances also are available in Lange s Handbook of Chemistry... 

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