Distillation Gilliland Correlation

FIG. 13-41 Comparison of rigorous calcnlations with Gilliland correlation. [Henley and Seader, Eqnilihrinm-Stage Separation Operations in Chemical Engineering, Wiley, New York, 1981 data of Van Winkle and Todd, Chem. Eng., 78(21), 136 (Sept. 20, 1971) data of Gilliland, Elements of Fractional Distillation, 4th ed., McGraw-Hill, New York, 1950 data of Brown and Maiiin, Trans. Am. Inst. Chem. Eng., 35, 679 (1.93.9) ]... 

Note in this description the words reflux rate and reflux ratio. They are different, and you need to be careful to use the right one, since using too small a reflux rate could make your column not work. Finally, you use the Eduljee version (Eduljee, 1975) of the Gilliland correlation (Gilliland, 1940) [Eq. (6.6)] to find the actual number of stages. This equation correlates data on roughly one-hundred distillation columns. You must specify either the reflux ratio (R) or number of stages (S) in order to use this equation. 

F. Generalize. The Gilliland correlation is a rapid method for estimating the number of equilibrium stages in a distillation column. It should not be used for final designs because of its inherent inaccuracy. 

D6. We are separating 1,000 mol/h of a 40% benzene, 60% toluene feed in a distillation column with a total condenser and a partial reboiler. Feed is a saturated liquid. CMO is valid. A distillate that is 99.3% benzene and a bottoms that is 1% benzene are desired. Use the Fenske equation to find the number of stages required at total reflux, a McCabe-Thiele diagram to find (L/D), and the Gilliland correlation to estimate the number of stages required if L/D = 1.15(L/D)n. Estimate that the relative volatility is constant at a x = 2.4. Check your results with a McCabe-Thiele diagram... 

Gilliland correlation and Fenske-Underwood-GiUiland method for the number of st es GiUiland (1940) developed an empirical shortcut method to determine the number of stages N needed in a distillation... 

McCormick [97] presents a correlation for Gilliland s chart relating reflux, minimum reflux, number of stages, and minimum stages for multicomponent distillation. Selecting a multiplier for actual reflux over minimum reflux is important for any design. Depending on the com-... 

The two most frequently used empirical methods for estimating the stage requirements for multicomponent distillations are the correlations published by Gilliland (1940) and by Erbar and Maddox (1961). These relate the number of ideal stages required for a given separation, at a given reflux ratio, to the number at total reflux (minimum possible) and the minimum reflux ratio (infinite number of stages). 

DSTWU - shortcut distillation using Winn-Underwood-Gilliland equations and correlations Distl - Edmister shortcut distillation... 

Truly multicomponent solutions based on continuous distillation shortcut methods have been proposed for batch distillation. The Fenske, Underwood, and Gilliland equations or correlations are commonly used in conjunction with each other to solve continuous distillation problems as described in Section 12.3. Diwekar and Madhavan (1991) describe how these techniques may be modified for the design of batch distillation columns for variable and constant reflux cases. 

NUMBER OF IDEAL PLATES AT OPERATING REFLUX. Although the precise calculation of the number of plates in multicomponent distillation is best accomplished by computer, a simple empirical method due to Gilliland is much used for preliminary estimates. The correlation requires knowledge only of the minimum number of plates at total reflux and the minimum reflux ratio. The correlation is given in Fig. 19,5 and is self-explanatory. An alternate method devised by Erbar and Maddox is especially useful when the feed temperature is between the bubble point and dew point. 

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