Gilliland’s correlation

Empirical methods, which are based on the performance of operating columns, or the results of rigorous designs. Typical examples of these methods are Gilliland s correlation, which is given in Volume 2, Chapter 11, and the Erbar-Maddox correlation given in Section 11.7.3. 

The most popular reflux-stages relationships are by Gilliland (45) and Erbar and Maddox (46). Many designers (9,11,29,47) recommend both, some (10,23,28,30,32,33,48) prefer Gilliland s, while others (13,49) prefer Erbar and Maddox s. The Erbar and Maddox correlation is considered more accurate (22,26,29,33,49), especially at low reflux ratios (49) however, the accuracy of Gilliland s equation for shortcut calculations is usually satisfactory. The single curve in Gilliland s correlation is easier to computerize. 

Gilliland s correlation has produced relevant results that offer the following advantages ... 

The maximum deviation using Gilliland s correlation in terms of tray number is within the7% range [39]. 

Figure 7-16. Linear coordinates based on Gilliland s correlation.

Gilliland s Correlation can then be used with the value of N m from Fenske and (R/D)mj from Underwood to determine the actual number of stages (N) from the actual reflux ratio... 

There are a range of equations that have been devised to describe Gilliland s correlation. The simplest of these is the Eduljee Equation. 

From Gilliland s correlation and an appropriate efficiency, estimate the actual tray requirements. 

Gilliland s work should be an encouragement to us all in developing shortcut methods from rigorous results. The proliferation of computers makes our job relatively easy. 1 feel that when correlations of this type are developed, one shouldn t stop w ith the graph but continue until an equation is fitted to the data. Computers need equations. 

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-... 

In defining a 7-factor (jd) for mass transfer there is therefore good experimental evidence for modifying the exponent of the Schmidt number in Gilliland and Sherwood s correlation (equation 10.225). Furthermore, there is no very strong case for maintaining the small differences in the exponent of Reynolds number. On this basis, the /-factor for mass transfer may be defined as follows ... 

The last step in the Hdist program is the calculation of actual trays with a given actual reflux input. Gilliland s [10] correlation of stages and reflux does this step. Gilliland s equation follows ... 

USE MCCORMICK S EQUATION TO DETERMINE GILLILAND S GRAPHICAL CORRELATION AND HENCE THE EQUILIBRIUM NUMBER OF STAGES. 

Gilliland s (13) correlation is recommended for estimating the number of theoretical separation stages required by the design. An alternate method is that of Mason (14). Gilliland is quite simple and is used as follows. 

Wang, L. Ruvinov, S. Strausberg, S. Gallagher, D.T. Gilliland, G. Bryan, P.N. Prodomain mutations at the subtilisin interface - correlation of... 

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. 

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