Distillation Thiele-Geddes method

The method starts with an assumption of the column temperature and flow profiles. The stage equations are then solved to determine the stage component compositions and the results used to revise the temperature profiles for subsequent trial calculations. Efficient convergence procedures have been developed for the Thiele-Geddes method. The so-called theta method , described by Lyster et al. (1959) and Holland (1963), is recommended. The Thiele-Geddes method can be used for the solution of complex distillation problems,... 

This method also considers the stage temperatures as the independent variables. The algorithm is applied to a single-feed, two-product column with a partial condenser and reboiler. As in the original Thiele-Geddes method, the problem definition is such that the feed component flow rates, are known and fixed. The column pressure profile is also fixed, as well as its configuration, which defines the number of stages and feed location. In addition, one product rate (the distillate) and one internal flow (such as the reflux rate, Lj) are specified. The solution method, outlined below, is described in detail by Holland (1975). 

The modified Thiele-Geddes method was mainly designed for conventional distillation columns although it has been generalized to handle complex columns (Holland, 1963). It is limited in the types of performance specifications it can handle and could be numerically unstable, especially for wide-boiling or nonideal mixtures (Wang et al., 1980). 

A method similar to the Thiele-Geddes method has been proposed by Hummel (Ref. 9). In this method plate-to-plate calculations are made for a few plates at each end and around the feed plate to establish the temperatures. With the values and the known number of theoretical plates the temperature gradient in the tower is drawn. This then gives the temperatures to employ in a Thiele-Geddes type of calculation. For a given number of plates and a given reflux ratio, this method requires an estimation of the distillate, bottoms, and feed-plate compositions. Basically, Hummel s method furnishes a systematic method of successive approximations for the plate temperatures to be used in evaluating the equilibrium constants. 

Thiele-Geddes Stage-hy-Stage Method for Simple Distillation. 13-40... 

THIELE-GEDDES STAGE-BY-STAGE METHOD FOR SIMPLE DISTILLATION... 

Although not widely used anymore, this method is presented because it was the forerunner for many of the more recent and more efficient methods. It is one of the earlier methods for rigorous numerical solution of distillation columns. It was first described by Thiele and Geddes (1933) and later detailed by Lyster et al. (1959). 

Edminster (Ref. 4) has presented a modified absorption factor method that determines the molal quantities for each component as a fraction of their values in the distillate and bottoms in a manner somewhat similar to the Thiele and Geddes equations. The geometric mean of the absorption and stripping factors at the ends of the section under consideration is employed, and empirical correction terms are applied to these averages. 

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