Title: Double Azeotropy: calculations with Newton-like methods and continuous GRASP (C-GRASP)

Authors: Aline De Lima Guedes; Francisco Duarte Moura Neto; Gustavo Mendes Platt

Addresses: Instituto Politecnico, Universidade do Estado do Rio de Janeiro, Alberto Rangel S/N, 28630050, Nova Friburgo, Rio de Janeiro, Brazil. ' Instituto Politecnico, Universidade do Estado do Rio de Janeiro, Alberto Rangel S/N, 28630050, Nova Friburgo, Rio de Janeiro, Brazil. ' Instituto Politecnico, Universidade do Estado do Rio de Janeiro, Alberto Rangel S/N, 28630050, Nova Friburgo, Rio de Janeiro, Brazil

Abstract: Azeotropy is a thermodynamic phenomenon where a boiling liquid produces a vapour with identical composition. This situation is a challenge for separation engineering, since distillation processes explore the differences among relative volatilities and, thus, an azeotrope can be a barrier for the separation. In binary mixtures, the azeotropy calculation problem is characterised by a 2 × 2 non-linear system with pressure or temperature and a molar fraction as unknowns. An interesting and rare case is the so-called double azeotropy, when this non-linear system has two solutions, corresponding to two distinct azeotropes. In this paper, we present some numerical aspects of double azeotropy using classical approaches (Newton|s methods with globalisation techniques) and a new non-linear optimisation algorithm (the C-GRASP method).

Keywords: double azeotropy; Newton-like methods; continuous GRASP; C-GRASP; thermodynamics; separation engineering; nonlinear optimisation.

DOI: 10.1504/IJMMNO.2011.043091

International Journal of Mathematical Modelling and Numerical Optimisation, 2011 Vol.2 No.4, pp.387 - 404

Received: 06 Aug 2010
Accepted: 02 Dec 2010

Published online: 14 Oct 2011 *

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