Underwood minimum reflux multicomponent

Ultrafiltration, 631 applications, 633 membranes, 637-639 Underwood minimum reflux binaty, 387 multicomponent, 397 Units, conversion of, 671, 672 UMQUAC equation, 475 Upflow fixed beds, 609 Uranium recovery, 515 Utilities, typical characteristics, 15... 

The multicomponent form of the Underwood equation can be used to calculate the vapor flow at minimum reflux in each column of the sequence. The minimum vapor rate in a single column is obtained by alternate use of two equations ... 

Colburn (1941) and Underwood (1948) have derived equations for estimating the minimum reflux ratio for multicomponent distillations. These equations are discussed in Volume 2, Chapter 11. As the Underwood equation is more widely used it is presented in this section. The equation can be stated in the form ... 

The Underwood Equations can be used to predict the minimum reflux for multicomponent distillation9. The derivation of the equations is lengthy, and the reader is... 

Underwood AJV (1946) Fractional Distillation of Multicomponent Mixtures - Calculation of Minimum Reflux Ratio, 7 Inst Petrol, 32 614. 

The Underwood and Fenske equations may be used to find the minimum number of plates and the minimum reflux ratio for a binary system. For a multicomponent system nm may be found by using the two key components in place of the binary system and the relative volatility between those components in equation 11.56 enables the minimum reflux ratio Rm to be found. Using the feed and top compositions of component A ... 

Underwood,E.R., Fractional Distillation of Multicomponent Distillation -Calculation of Minimum Reflux Ratio, J. Inst Petrol., 32,274, 614, 1946. Van Winkle, M.C., Todd, W., Optimum Fractionation Design by Simple Graphics Methods, Chem. Eng., 78, 21,136,1971. 

Underwood, A. J. V. Fractional Distillation of Multicomponent Mixtures—Calculation of Minimum Reflux Ratio, J. Inst. Petrol. 32, 614 (1946). 

Examples chosen for this category include the operations of vapor/liquid separation, heat transfer, and fluid flow. The Underwood method of estimating the minimum reflux ratio for a fractionation column multicomponent... 

For multicomponent separations, it is often necessary to estimate the minimum reflux ratio of a fractionating column. A method developed for this purpose by Underwood [10] requires the solution of the equation... 

Use the Underwood equations to determine the minimum reflux ratio for multicomponent distillation. 

For multicomponent mixtures, all components distribute to some extent between distillate and bottoms at total reflux conditions. However, at minimum reflux conditions none or only a few of the nonkey components distribute. Distribution ratios for these two limiting conditions are shown in Fig. 12.14 for the debutanizer example. For total reflux conditions, results from the Fenske equation in Example 12.3 plot as a straight line for the log-log coordinates. For minimum reflux, results from the Underwood equation in Example 12.5 are shown as a dashed line. 

The Underwood equations can be used to calculate the minimum reflux ratio in a multicomponent system if the relative volatilities of the components are constant. There are two equations. 

An analytical approach for the estimation of minimum reflux ratio has been published by Underwood and is useful for multicomponent as well as binary systems. There are three buic assumptions made by Underwood ... 

Underwood, A. J. V. (1946b). Fractional Distillation of Multicomponent Mixtures (Calculation of Minimum Reflux Ratio). J. Inst. Petrol, 32,614-26. Underwood, A. J. V. (1948). Fractional Distillation of Multicomponent Mixtures. Chem. Eng. Prog., 44,603-14. 

The Underwood equations (Underwood, 1948) provide a shortcut method for determining the minimum reflux ratio, ilmin, in multicomponent distillation under the following assumptions constant relative volatilities and constant molal overflows in the stripping section as well as in the enriching section. The minimum reflux ratio, i min> is obtained from a solution of the following two equations for n components ... 

Underwood equation A shortcut method used to estimate the minimum reflux ratio in a multicomponent distillation process. It was proposed by A. J. V. Underwood in 1948. 

Occasionally there is a need to perform some preliminary but rapid estimates for a specific separation without resorting to the tedious graphical or plate by plate calculations. In such instances one can turn to some of the short-cut methods that have been developed specifically for multicomponent separations in the chemical process industry but which also work reasonably well with binary and multicomponent separations at low temperatures. These are the Fenske-Underwood method for obtaining the minimum number of plates at total reflux, the Underwood method for obtaining the minimum reflux, and the Gilliland correlation to determine the theoretical number of plates based on the information provided by the two prior methods. 

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