Modelling methanol recovery in wine distillation stills with packing columns J. Carvallo a , M. Labbe b , J.R. Pérez-Correa b, * , C. Zaror a , J. Wisniak c a Department of Chemical Engineering, Universidad de Concepción, Edmundo Larenas s/n, Casilla 160-C, Concepción, Chile b Department of Chemical and Bioprocess Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile c Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel article info Article history: Received 2 May 2010 Received in revised form 31 January 2011 Accepted 9 February 2011 Keywords: Differential algebraic system Dynamic simulation Mass transfer Orthogonal Collocations Spirits Vapour-liquid equilibrium abstract Methanol is a well known toxic congener that contaminates many spirits. Chilean legislation indicates that methanol content in wine distillates should not exceed 1.5 g/L absolute alcohol (a. a.). To achieve this stringent limit, distillers need new tools to improve their operational policies since trial and error experiments are too slow. In this paper, a fast pseudo-stationary simulator for batch distillations in packed bed columns was developed. Packed bed columns are preferable for batch productions of fruit wine distillations since they have a wider range of stable hydraulic operations. The model was solved using orthogonal collocations and considers a liquid vapour equilibrium model of the ternary water- ethanol-methanol mixture, which accounts for most of the volatiles in wine. Simulations compared favourably with our own laboratory batch distillations of water-ethanol-methanol mixtures. In addition, our model simulations were able to qualitatively reproduce the results reported in the literature for methanol recovery in experimental batch distillations. Ethanol recovery errors were within measure- ment errors, while methanol simulations showed a 3% bias by the end of the distillation. Hence, the developed model is accurate and could be used to explore optimal operational policies in order to minimize methanol content in the heart cut used in the final product. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Pisco brandy is one of the most popular alcoholic beverages in Chile, a young distillate from Muscat wine with a distinctive fruity character produced since colonial times. During the last decade, several studies have been carried out to define and enhance the aromatic quality of this beverage, improve process operation and reduce costs. Like other spirits, Pisco’s characteristics depend on raw materials, fermentation process, distillation method and ageing. All these will determine the content of minor volatile components, so- called congeners, in the distillate. Congeners can be favourable (terpenes, esters and some high alcohols at very low concentrations), off-flavours (fatty acids), or even toxic (methanol, acetaldehyde and furfural). In Pisco distillates, oenologists normally look for high contents of terpenes and esters (that define the typical Muscat aroma) and very low concentration of fatty acids, which are normally asso- ciated with tails aroma. Specific distillation technologies have been developed to efficiently and reproducibly obtain Pisco distillates with a pre-defined aromatic characteristic. Mathematical modelling has been crucial in this development, since process engineers can use simulations to explore many operational strategies, predict the impact of changes in raw materials and design new control methods. Nevertheless, minimization of toxic compounds in Pisco has not received major attention yet. Indeed, methanol is believed to be associated with many discomforts experienced after alcohol inges- tion, such as fatigue, thirst, headache, stomachaches, nauseas, vomits, hypersensitivity to light and sound, lack of concentration and atten- tion, tremors, excessive perspiration and hypertension (Swift & Davidson, 1998). Methanol is slowly metabolized in the human body, producing formaldehyde and formic acid, which are extremely toxic at high concentrations. Hence, in many countries the methanol content of alcoholic beverages is controlled. In Chile, the concentra- tion of methanol should be less than 1.5 g/L of absolute alcohol (a.a.). Packed columns are best suited to distil wine in batch stills since they have a wider range of stable hydraulic operations. Therefore, operating policies with an extended range of reflux rates are possible, increasing the degrees of freedom during operation. However, packed columns came after bubble caps; hence, the conservative Chilean spirits industry still traditionally uses this older technology to distil Pisco. This research focuses on packed column technology with the intended use for high volume opera- tions for fruit distilled spirits, which is very relevant for the case of a fruit producing country such as Chile. * Corresponding author. Tel.: þ56 2 3544258; fax: þ56 2 3545803. E-mail address: perez@ing.puc.cl (J.R. Pérez-Correa). Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont 0956-7135/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2011.02.007 Food Control 22 (2011) 1322e1332