COOLING COMPRESSED AIR and GASES
NEW BOOKS
Computer Calculations for Multicomponent Vapor-Liquid Equilibria. J.M . Prausnitz. C. A . Eckert, R. V. Orye, and J . P. O’Connell. i x f 238 pages. Prentice-Hall, Inc., Englewood Cliys, A T . J . 07632. 7967. 412.50.
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COOLING LIQUIDS
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The use of empirically obtained equilibrium vaporization ratios has long dominated calculations involving sizing of multicomponent vaporliquid separational equipment. ,The little book by Prausnitz and coworkers will not lessen the widespread attachment of industrial technologists to the vaporization ratio, but it should command the respect of serious distillation workers everywhere. The book presents a simplified, rational approach to calculations of multicomponent vaporliquid equilibrium which is both thermodynamically sound and capable of quite wide application. The book consists of six short chapters and a detailed appendix which contains the Fortran programs and subroutines which are used in the method. T h e basic postulate in the book is the 2 posteriori assumption that vapor-liquid equilibrium should be based upon the fact of the equivalence of the fugacity of a component in any phases in which it exists. Thus, the task of calculating vapor-liquid behavior involves establishing standard states for each of the components in the liquid phase, the activity coefficients of each of the components in the liquid phase, and the fugacity coefficients of each of the components in the gas phase. While, at first appearing to be a formidable task, it is actually made easy by the following expedients : the fugacity coefficients are obtained through the use of second virial coefficients, generally estimated rather accurately by three-parameter generalized methods; liquid phase activity coefficients for multicomponent mixtures are predicted with
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
good accuracy by the use of binary interaction parameters only. The first expedient limits the pressure at which predictions may be reliably made to moderate pressures, usually below 30 atmospheres. The second expedient is surprisingly effective in predicting liquid activity coefficients for multicomponent mixtures through the use of the two constant Wilson equations. Parameters for each of the binary systems can then be formed from the multicomponent mixture. After laying a sound thermodynamic groundwork for the phase behavior in the first four chapters, the authors briefly introduce the Fortran programs and subroutines which are presented in considerable detail in Appendix A. There are four main programs: bubble point temperature, bubble point pressure, dew point temperature, and dew point pressure. The program logic of the main programs and subroutines should not prove mystifying to the average reader, even those who have not been formally introduced to Fortran language and the Fortran compiler. Every program and subroutine is schematically diagrammed in either Chapter 5 and G or in Appendix A, and copies of the programs are given in Appendix A along with numerous example problems. Appendix B contains a wealth of information on pure components and binary systems, including the Wilson parameters for 99 binary systems and Henry’s constants for numerous gassolvent systems, and much other useful information. The book should prove useful in establishing the philosophy of a rational therhodynamic approach to heterogeneous phase behavior. For this and other, more pragmatic reasons, the book is a welcome addition to the distillation literature. James P. Kohn
