Vapor-liquid separation processes

Finally, an article by Hanson and Somerville takes note of the current impact of high-speed computers upon design, and shows how computers allow very simple calculation steps to be applied repetitively in solving complex arrangements of process operations. These authors provide a very widely applicable computation program for vapor-liquid separation processes. The program typifies present-day computation procedures and should be of direct use to a large number of readers. 

There are several characteristics common to the describing equations of all types of multicomponent, vapor-liquid separation processes, both single- and multi-stage, that make it possible to exploit the inside-out concept in similar ways to solve them efficiently and reliably. The equations have as common members component and total mass balance, enthalpy balance, constitutive and phase equilibrium equations. In addition, all such processes require K-value or fugacity coefficient and vapor and liquid enthalpy models. In all cases the describing equations have similar forms, and depend on the primitive variables (temperature, pressure, phase rate and composition) in essentially the same ways. Before presenting the inside-out concept, it will be useful to identify two classes of conventional methods and discuss their main characteristics. 

Complex distillation may be defined as a multistage vapor-liquid separation process that includes one or more of the following features multiple feeds, side draws, pumparounds, and side heaters or coolers. 

The absence of an interphase compositional differential makes the separation of azeotropes into their constituent components impossible by conventional vapor-liquid separation processes. The azeotropic pattern may be altered by adding an external component—an entrainer—that breaks the original azeotrope while forming new ones with the feed components. The process may be designed so that the... 

For the analysis of distillation and other vapor-liquid separation processes one must estimate the compositions of the vapor and liquid in equilibrium. This topic is considered in detail in this chapter with particular reference to the preparation of mixture vapor-liquid equilibrium (VLE) phase diagrams, partial vaporization and condensation. calculations, and the use of vapor-liquid equilibrium ippasurements to,obtain infonnac-. 

In Chapter 7, the focus is on separation processes, in which the criteria for the selection of separation processes and the choices of equipment are reviewed before systematic methods of process synthesis are covered. The latter begin with sequences of ordinary distillation columns, then general vapor-liquid separation processes, and subsequently sequences that include azeotropic distillation columns. Also covered are considerations in selecting separation systems for gas mixtures and for solid-fluid systems. 

In Chapters 10 and 11 gas-liquid and vapor-liquid separation processes were considered. The separation processes depended on molecules diffusing or vaporizing from one distinct phase to another phase. In Chapter 12 liquid-liquid separation processes were discussed. The two liquid phases are quite different chemically, which leads to a separation on a molecular scale according to physical-chemical properties. Also, in Chapter 12 we considered liquid-solid leaching and adsorption separation processes. Again differences in the physical-chemical properties of the molecules lead to separation on a molecular scale. In Chapter 13 we discussed membrane separation processes where the separation also depends on physical-chemical properties. 

This part, on applications, covers the following unit operations 8. Evaporation 9. Drying of Process Materials 10. Stage and Continuous Gas-Liquid Separation Processes (humidification, absorption) 11. Vapor-Liquid Separation Processes (distillation) 12. Liquid—Liquid and Fluid-Solid Separation Processes (adsorption, ion exchange, extraction, leaching, crystallization) 13. Membrane Separation Processes (dialysis, gas separation, reverse osmosis, ultrafiltration) 14. Mechanical-Physical Separation Processes (filtration, settling, centrifugal separation, mechanical size reduction). 

Distillation is a vapor-liquid separation process widely employed in petrochemical, chemical, and allied industries nowadays. The simulation of distillation has long been investigated since the 1930s of the last century. 

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