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Heat Duty (heat + duty)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

A Short Note on Steady State Behaviour of a Petlyuk Distillation Column by Using a Non-Equilibrium Stage Model

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2006
Erika Fabiola Abad-Zarate
Abstract A Petlyuk distillation column, considering equilibrium and non-equilibrium stage models, was studied. Rigorous simulations were conducted using Aspen PlusÔ RATEFRAC Module for the separation of ternary mixtures. According to the equilibrium model, the energy-efficient design of the Petlyuk column requires that the intermediate component be extracted from the maximum point in the composition profile in the main column. It was found that, for the intermediate component, mass transfer occurs from the vapour to the liquid phase from the top of the column to the stage where the side stream is extracted, from this point mass transfer occurs in the opposite direction. This point, considering the non-equilibrium model, corresponds to the stage in which the net mass transfer rate is zero. For the case of two segments per stage, it was found that the heat duties predicted by the equilibrium model are significantly lower than those obtained by using the non-equilibrium model, which is consistent with previous reported results. However, it is important to say that despite the higher energy duty predicted by the non-equilibrium model; both models predict significant energy savings. On a étudié une colonne de distillation de Petlyuk en considérant des modèles d'étage en équilibre et hors équilibre. Des simulations rigoureuses ont été menées au moyen du module RATEFRAC d'Aspen PlusÔ pour la séparation de mélanges ternaires. Selon le modèle en équilibre, une conception énergétiquement efficace de la colonne Petlyuk nécessite que le composant intermédiaire soit extrait du point maximum du profil de composition dans la colonne principale. On a trouvé que, pour le composant intermédiaire, le transfert de masse se produisait de la vapeur vers le liquide de la tête de la colonne jusqu'à l'étage où le courant secondaire est extrait; à partir de ce point le transfert de masse se produit dans la direction opposée. Ce point, en considérant le modèle hors équilibre, correspond à l'étage où le taux de transfert de masse net est nul. Dans le cas où il y a deux segments par étage, on a trouvé que les rendements thermiques prédits par le modèle en équilibre étaient significativement plus faibles que ceux obtenus à l'aide du modèle hors équilibre, ce qui est cohérent avec les résultats existants. Cependant, il est important de préciser que malgré le rendement énergétique plus élevé prédit par le modèle hors équilibre, les deux modèles fournissent des économies d'énergie significatives. [source]

A matrix method for multicomponent distillation sequences

AICHE JOURNAL, Issue 7 2010
Vishesh H. Shah
Abstract We describe a simple-to-use "matrix" method for obtaining all the basic distillation configurations and additional thermally coupled configurations that separate a zeotropic multicomponent feed into essentially pure product streams. This provides an opportunity to rank-list the configurations for a given application subject to criteria of interest. The only information needed to generate the configurations is the number of components in the feed. We have successfully enumerated all the configurations for feeds containing up to eight components. The method can also be used to generate nondistillation and hybrid separation configurations, and even easy-to-retrofit configurations. We illustrate the use of this method by applying it to the highly energy-intensive problem of petroleum crude distillation. We have identified more than 70 new configurations that could potentially have lower heat duty than the existing configuration. A significant number of these could reduce the heat demand by nearly 50%. © 2009 American Institute of Chemical Engineers AIChE J, 56: 1759,1775, 2010 [source]

Shortcut method for kinetically controlled reactive distillation systems

AICHE JOURNAL, Issue 6 2003
J. W. Lee
A geometric-based shortcut method for reactive distillation is addressed. The rectification body method for nonreactive distillation, the concept of critical Damköhler numbers, and the geometric design method for reactive distillation are combined with a new eigenvector analysis of pinch points. This shortcut method provides a minimum or reasonable Damköhler number for a given heat duty, as well as the design implication of how to effectively distribute reaction zones inside a column. This method can be used for a fast screening of process design alternatives and for an initialization of rigorous optimization. [source]

Multicomponent thermally coupled systems of distillation columns at minimum reflux

AICHE JOURNAL, Issue 12 2001
Zbigniew T. Fidkowski
A method for calculating the minimum vapor flow in a ternary fully thermally coupled system of distillation columns was developed earlier by Fidkowski and Krolikowski. This method was developed further for fully thermally coupled systems separating four or more components. For multicomponent mixtures having constant relative volatilities and equal latent heats, the method leads to the identification of all of the minimum vapor flow rates in each distillation column that provide the same overall minimum heat duty in the reboiler. The quaternary fully coupled system of columns requires less heat energy than conventional configurations. These savings are often on the order of 20,50%. [source]