Design methods for binary systems

Another graphical design method for binary systems is that of Ponchon" and Savarit. This method includes an energy balance on each stage and is totally rigorous for binary systems. However, it requires mixture enthalpy data, often unavailable, and is cumbersome in application. 

The distillation of binary mixtures is covered thoroughly in Volume 2, Chapter 11, and the discussion in this section is limited to a brief review of the most useful design methods. Though binary systems are usually considered separately, the design methods developed for multicomponent systems (Section 11.6) can obviously also be used for binary systems. With binary mixtures fixing the composition of one component fixes the composition of the other, and iterative procedures are not usually needed to determine the stage and reflux requirements simple graphical methods are normally used. 

Owing to the availability of high-speed computers, short cut methods for designing distillation processes (e.g. McCabe-Thiele and Ponchon-Savarit for binary systems or the equations of Fenske, Underwood and Gilliland for multicomponent mixtures, see Gmehling and Brehm, 1996 and Satder, 2001 for details) are no longer required. 

The general principles of design of multicomponent fractionators are the same in many respects as those for binary systems, but the dearth of adequate vapor-liquid equilibrium data imposes severe restrictions on their application. These are especially needed for liquids which are not ideal, and the danger of attempting new designs without adequate equilibrium data or pilot-plant study for such solutions cannot be overemphasized. Inadequate methods of dealing with tray efficiencies for multicomponents represent another serious problem still to be solved. 

In this chapter consideration is given to the theory of the process, methods of distillation and calculation of the number of stages required for both binary and multicomponent systems, and discussion on design methods is included for plate and packed columns incorporating a variety of column internals. 

Stresau, Development of the VARICOMP Method, Expansion of Applicability (To Determine Detonation Transfer Probabilities with Reduced Dependence Upon System Variables). Part 1. Calibration and Characterization of PBXN-5 as Design Explosive , R. Stresau Laboratory, Inc, Spooner, Wis (27 Dec 1972) [Rept RSLR 72-7 for the Naval Weapons Center, China Lake, Calif] 3) Ibid, "Ibid. Part 3. Calibration of RDX/Calcium Stearate Binary System for Use as VARICOMP Surrogates , Ibid (14 Feb 1973) [Rept RSLR 73-1 for the Naval Weapons Center, China Lake, Calif]... 

The phase equilibrium of the binary system stearyl alcohol/C02 was measured in a high pressure view cell (own design) according to the synthetic method by Teipel et al. [6] and presented in Fig. 2. The curves represent the border between the homogeneous and two phase region above the curve a homogeneous solution is present, below two phases exist. The measurements were carried out for different concentrations of stearyl alcohol in CO2 represented by the different curves. It is seen that 2.1 wt.% of stearyl alcohol are complete soluble in SC-CO2 at 333 K and 20 MPa. 

This paper has provided a framework for further application of Second Law based design methodology to separation systems. It has done so by providing a relationship that gives the available-energy destruction for a binary separation as a function of the process variables for the case in which the entropy production is primarily due to mass transfer effects. The Second Law methodology has been described and applied to a simple binary separation system. The method yields results identical to those obtained from a traditional direct search technique, and accurately indicates the respective trade-offs between fuel costs and capital investment. 

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