Short-Cut Design Procedure for Batch Distillations

Abstract

This paper presents a short-cut procedure for the design of batch distillations which is equivalent to the Fenske−Underwood−Gilliland procedure for continuous distillations. Given a separation task, we propose computing the minimum number of stages and minimum reflux ratio required to perform it by batch distillation. These parameters are quite different from the continuous N min and R min parameters for the same separation task, because of the difference in the form of the material balances (steady state in continuous but integrated differential mass balances in the batch case). We propose that they should be computed as the number of stages and reflux ratio required by hypothetical batch distillation columns that operate at total reflux or have an infinite number of stages, respectively. Then, it is shown that the performance of batch distillations does correlate in Gilliland coordinates constructed with these batch N min and R min. This produces a quite simple, straightforward method to do preliminary design of batch distillations.

Operation planning in the rectification of essential oils

“…These distributions are obtained as product quantities relative to feed quantities and are used to solve the material balances for the whole network. With all the intermediate compositions already defined, it is possible to predict the reflux ratio needed for each separation task by using a Gilliland-like correlation developed by Salomone, Chiotti, and Iribarren (1997) for batch rectification.…”

“…(3)-(5) provides all the information needed by the methodology proposed by Salomone, Chiotti, et al (1997) to get the reflux ratios R min needed to achieve these separations. The minimum reflux to perform a separation task is defined as the reflux required by a hypothetical batch distillation column having an infinite number of separation stages, so its instantaneous separation performance is given by Underwood equations.…”

“…The integration is performed for a guessed value of R starting from feed composition and stops when the recovery of the light key component reaches g lk Then, depending on the recovery obtained for the heavy key component being smaller or larger than g hk dictates the next trial of R being smaller or larger than the value at the previous iteration, till convergence. A more detailed description of the procedure is presented by Salomone, Chiotti, et al (1997).…”

Simple, robust, and fast iterative solution of Underwood's equation for minimum reflux

“…Furthermore, they point out that their model is more convenient to use for simulating existing columns than the shortcut model independently developed by Diwekar and Madhavan (1991). Salomone et al (1997) stress the important role that batch distillation plays in the manufacture of specialty and fine chemicals, in the purification of liquid products, and in the recovery of solvents. They say that this role explains the interest in the development of process models and design procedures pertinent to batch distillation.…”

Efficient Simulation of Batch Distillation Processes by Using Orthogonal Collocation

“…Either short-cut models (Diweckar and Madhavan [1]; Al-Tuwaim and Luyben [2]; Sundaram and Evans [3]; Barolo and Guarise [4]; Salomone et al [5]) or simplified trayby-tray models (Galindez und Fredenslund [6]; Farhat et al [7]) were used. Despite the fact that satisfactory results were achieved in some cases, such simplifications may affect the accuracy of the solutions.…”